ACTA PHYTOGEOGRAPHICA SUECICA 65 EDIDIT SYENSKA V AXTGEOGRAFISKA SALLSKAPET

Leif Kullman

Change and stability in the altitude of the birch tree-limit in the southern Swedish Scandes 1915-1975

UPPSALA 1979

ACTA PHYTOGEOGRAPHICA SUECICA 65 EDIDIT SVENSKA V AXTGEOGRAFISKA SALLSKAPET

Leif Kullman

Change and stability in the altitude of the birch tree-limit in the southern Swedish Scandes 1915-1975

Almqvist & Wiksell International, Stockholm

UPPSALA 1979 Suggested citation: Kullman, L., 1979, Change and stability in the altitude of the birch tree-limit in the southern Swedish Scandes 1915-1975. Acta Phytogeogr. Suec. 65. Uppsala.

Doctoral dissertation at Umea University, Sweden 1979.

ISBN 91-7210-065-6 (paperback) ISBN 91-7210-465-1 (cloth)

Leif Kullman 1979 ©

Svenska Vaxtgeografiska Sa1lskapet Box 559, S-751 22 Uppsala

Editor: Erik Sjogren Technical editor: Gunnel Sjors

Printed in Sweden 1979 by Borgstroms Tryckeri AB, Motala Contents

Introduction 1 Previous investigations 1 Aims of the investigation 2

Th e investigated area 4 Topography, solid geology and drift deposits 4 Climate 4 Continentality-maritimity 6, Temperature 6, Precipitation 6, Snow cover 7, Wind direction 7, Length of the vegetation period 7 Recent climatic fluctuation 7 Climatic fluctuation within the investigated area 8 Main features of the vegetation 12

Human impact around the tree-limit 14 Prehistoric time 14 Historic time 14 Permanent settlement 14, Shieling practice 15, Decline of shieling practice 17, Lapps and reindeer grazing 18

Insect attack 22

Investigation methods 23 Determination of altitude 23 Age-determination of trees 23 Use of previous data for the altitude of tree-limit 24 Age-determination transects 26 Photographic record 27

Basic data from the investigated localities 28 Explanatory remarks, terminology and abbreviations 28, Present-day altitudinal limits 28, Age-determination transect 28, Documentation 29, Past tree-limit (PTL) 29, Degree of change 29

Investigated localities 31

Analysis of primary data 84 Significantdisplacement and its relation to geographical position 84, Continentality/maritimity 85, Aspect 86, Depth and duration of snow cover 86, Angle of slope 87, Slope morphology 88, Local land usage 88, Chronology of birch expansion in the belt between PTL and TL 89, The colonisation of the present-day tree-limit level 91, Establishment of the TL 92, Minimum age of stems of trees growing at the TL 92, Relationship between the degree of tree-limit displacement and the altitude of the PTL 93, Changes in the growth rate and vitality of indi- vidual birch stems during the present decade 93 Summary of results 94 Discussion and general conclusions 96 The nature of the factors causing change or stability of the tree-limit 96, Relationship between degree of displacement and type of habitat 97, Extent and duration of the snow cover 98, Evidence for an earlier snow­ melt 98, Characteristic habitat features of localities with a recorded rise in tree-limit 99, Characteristic habitat features of localities with no recorded rise in tree-limit 105 Summarised conclusions 109

References 111 Maps 118

Appendices 119 Kullman, L., 1979, Change and stability in the altitude of the birch tree-limit in the southern Swedish Scandes 1915-1975. Acta Phytogeogr. Suec. 65. Uppsala. 128 pp. ISBN 91-7210-065-6, 91-72 10-465- 1.

The birch tree-limit was determined altimetrically during 1970-75. In most of the 213 sites investigated, similar determinations had been made in 1915-16 mainly by Dr. Harry Smith. Annual ring counts were made on the seemingly oldest birches along vertical line transects, which gave data on the tree-limit advance, if any. Such a rise was indisputably recorded for 75 %of the sites, with an unchanged altitude at the remaining ones . The observed rises were correlated to a variety of habitat factors. The sites were classified into four groups, with 0 m, 5-20 m, 25-40 m, and over 40 m displacement. Each factor was graded, objectively or subjectively, and the percentage distribution of displacement classes upon grades of factor strength was calculated. This yielded an "ecological lowest common denominator" for the displacement groups with regard to each factor considered. A clear relationship was found between changes in altitude of the birch tree-limit and changes in local snow conditions. Localities which, in 1915, had much snow and late thawing, showed a subsequent great rise, but little or no change in tree-limit was recorded for sites with a shallow snow cover. Intermediate cases showed moderate displacement. No relationship was found for degree of human impact. According to age of stems, 2 m tall or more and growing above the 1915 limit, most of the colonization took place in the 1930's, when a series of warm summers caused early thaw and rapid drying of the soil. Thus the rise was conditioned by seedling establishment mainly during the first half of the present century, coming to a halt about 1950, when the favourable climatic trend reversed. Birches already established, however, could grow on, up to the present day. The climatic ameliora­ tion in the earlier period is believed to have caused a decrease in meltwater, and in the soil, less moisture, earlier upwarming and higher temperatures. In localities where the tree-limit remained unchanged, the scantiness of the snow cover, both before and during the period 1915- 1975, may have prevented seedling establishment permanently through frequent droughts in the growth period. Altitudinal birch limits in Scandinavia depend on a complex of habitat factors, of which the local climate and its effect on the edaphic conditions are important.

Key words: tree-limit, birch, succession, climatic change, snow cover, land usage, germination, establishment.

Leif Kullman, Department of Ecological Botany, Umea University, S-901 87 Umea, Sweden

Introduction

The Swedish phytogeographer Goran Wahlen­ Previous investigations berg (1813, p. 35-38) was the first scientist to make a distinction between the tree-limit and the Previous investigations, both inspiring and pio­ forest-limit. Ever since then research on both of neering, have been made in this field, particularly these concepts has traditionally occupied a pro­ by Professor Ilmari Hustich (see e.g. 1958), who minent place in Scandinavia and many informa­ showed that a relationship existed between tive monographs on these subjects have ap­ changes in the altitudinal limits of Scots pine (Pi­ peared, especially during the first few decades of nus sylvestris L.) in N Finland during the 20th the present century. Many of these papers con­ century and climatic changes. tain a mass of detailed information on the altitudi­ The dynamics of the tree- and forest-limits of nal limits of different tree species (e.g. Smith birch (Betula pubescens Ehrh. s. 1.) and spruce 1920). (Picea abies (L.) Karst.) have not been systema­ The idea of utilising these earlier data as the tically investigated to the same degree, particular­ basis for a study of possible fluctuations in altitu­ ly not in Sweden. dinal limits during the present century therefore Prior to about 1930, the general opinion among readily suggested itself. In view of the detailed phytogeographers and forestry research workers and relatively well-substantiated information was that both the tree- and forest-limits in north­ available in the phytogeographical literature sug­ ern Europe were in a phase of retreat. About gesting that both the tree-limit and the fo rest-limit 1930, however, views changed and certain re­ (for definitionssee section, Explanatory remarks, search workers began to maintain that tree dis­ terminology and abbreviations) were advancing, tribution limits were extending both altitudinally such an investigation seemed to offer both a and latitudinally at the same time as self-regene­ worthwhile and an attractive field ofresea rch. ration from seed was improving in both scale and During recent years, furthermore, this problem frequency (see Hustich 1947, 1958 and the litera­ has become increasingly relevant, since foresters ture cited therein) . At the same time, thanks to have slowly but steadily become interested in climatological research, a picture emerged from timber production from and the forestry re­ the observational data which more and more sup­ sources of such marginal, high-lying areas and ported the view that since the close of the 19th also following the attempts of paleo-ecologists century there had been a progressive climatic and quaternary geologists to interpret post-glacial amelioration. Many biologists became aware of climatic fluctuations in terms of more or less ficti­ this postulate and they attempted to discover tious fluctuations of the tree-limit or forest-limit. whether or not a relationship existed between this It appeared likely, therefore, that research di­ recent climatic change and certain biological fluc­ rected towards a better understanding of the fac­ tuations (cf. Erkamo 1956; Perring 1965). tors affecting and controlling the position of the In 1951 the Geographical Society of Finland tree-limit would be gained by studying such alti­ arranged a symposium on various effects on plant tudinal shifts within a large and heterogeneous and animal life of the climatic amelioration (The geographical region, with varied topography , recent climatic fluctuation in Finland and its con­ climate, soil conditions, vegetation cover and sequences, 1952). The same problems were dis­ land utilisation conditions. cussed again by the Society during a meeting in

Acta phytogeogr. suec. 65 2 Le ifKullm an

1976. Hustich (1978) gives a concentrated ac­ recently in areas where it had not grown for a count of these discussions. long time. By sending a questionnaire to a large number of Within a relatively limited area in the moun­ Norwegian farmers, foresters and similar people, tains of southern Norway, Ve (1930, 1940, 1951, Hesselberg & Birkeland (1940) tried to find out 1968) has documented an upward expansion of whether and how the birch had reacted in recent birch, although he was unable to assess for cer­ times. The replies they received were fairly una­ tain the relative importance of the climatic im­ nimous; the birch forest-limit had risen in the past provement and the contemporary decline in the few decades and it had done so largely because of use of summer-farms (Sw, 'fabodvasen'). At one an improvement in the climate, although in many locality (Ve 1940, p. 77) he showed that the for­ cases a decline in the degree of utilisation of this est-limit had remained constant since the begin­ marginal region by man had also played a part. ning of the 19th century. These results must be accepted with some reser­ At Vettismorki in S Norway Skar (1964) ob­ vations, due to the way the questionnaire was served a marked advance of the birch up certain worded. hillslopes and an obvious regeneration of the A considerably more reliable and more de­ birch forest, with scattered old, and now dying, tailed picture was given by the results of Sand­ birches growing among a relatively young stand berg's (1940, 1958, 1960, 1963) investigations in (cf. also Ve 1940). Skar (op.cit.) considers that Torne Lappmark in N Sweden. Although no anthropogenic factors were responsible for these concrete examples of increased altitudinal limits changes only in exceptional cases. He found a lot are cited, the reports of local birch expansion of indications that at the end of the 19th century during the 1930's into formerly unforested areas the mountain birch forest was becoming thin­ appear to be convincing. Sandberg (op.cit.) noted ned-out and in a stage of decline. The naturally­ that the birch had colonised depressions in occurring rejuvenation succession was thereafter which, previously, the accumulated depth of accelerated by the change in climate . snow had been too great to permit tree growth. By repeating the observations, made by an ear­ The birch expansion had been most obvious in lier research worker at the start of the present the mountain heath and grassland communities of century, on the altitude of the forest-limit at seve­ the more western and relatively locally maritime ral localities in southeastern Norway, Aas (1969) areas, in places formerly subject to prolonged found that the forest-limit had advanced vertical­ snow-cover. ly by a mean value of 40 m. He believed the On the Norwegian side of the Sylene massif, reason to be the occurrence of a series of fa­ which borders on my own investigation area, vourable summers during the 1930's and 1940's. Nordhagen (1956, 1964) , by taking repeated pho­ Faegri (1972), however, is not convinced that tographs of the same localities, over a period of the upward expansion of the birch during this years, discovered that certain hill slopes which century has anything to do with the climatic ame­ did not bear a single birch shrub about 1920 had lioration. by the early 1950's become densely forested. He considered this to be due to a decrease in the duration of the snow-cover. In an adjacent area on the Swedish side of the border, Smith ( 1957), from a comparison of belt Aims of the investigation transects made in 1919 and 1950, showed that the birch had increased its distributional area in this 1. To determine in absolute terms any changes in mountain region. He judged the cause to be the the tree-limit of the birch (Betula pubescens drying-out of the ground associated with an ear­ Ehrh. s.l.) since the start of the present century, lier disappearance of the snow from previously within a relatively large and geographically and long-lying snowbeds. ethnologically heterogeneous region. From the Petsamo area, formerly in N Finland, 2. To discover the general and ultimate cause of Aario (1941) reported that the birch had expanded any observed changes in the tree-limit, i.e.

Acta phytogeogr. suec. 65 Change and stability of birch tree-limit in the Scandes 3 primarily changes in the climatic conditions and/ The project has also included a study of the or a decline in the utilisation of such areas by recent and post-glacial history of changes in the man. tree-limits of coniferous species. These results 3. Should the climatic factors turn out to be the will be presented in subsequent papers. most important, to investigate in detail how cli­ matic changes have produced the observed Nomenclature changes in the position of the tree-limit and, if possible, from the conclusions drawn, to define Nomenclature for vascular plants follows Lid the general factors which determine the height of (1974). the tree-limit of birch.

4. To indicate the most promising lines of ap­ Acknowledgements proach for future research on both forest- and tree-limits. Financial support has been provided by the Swedish Natural Science Research Council, the Hierta-Retzius 5. To make certain comments applicable to Research Fund, the Gunnar and Ruth Bjorkman Fund paleo-ecological work on the basis of the results for Botanical Research in Norrland, the P. F. Wahlberg obtained from the present investigation. Fund, the Seth M. Kempe Memorial Foundation and the Swedish Tourist Association Fund for Scientific 6. To establish as accurately as possible, at all Research. the localities investigated, the altitude of the pre­ I would like to thank most warmly Professor Bengt sent-day tree-limit so that future changes may be Pettersson and all my colleagues and the staff at the recorded in order to increase our knowledge and Department of Ecological Botany, Umea University, refine our understanding of the causes of such for their help in both word and deed towards the suc­ cessful completion of the work and its publication. I am changes. also greatly indebted to Dr. Sven Kilander, who with his wide knowledge of both the subject and of the investigated area, has facilitated my work in many Realization ways, as well as for placing his unpublished observa­ The work was carried out at the Department of tions and maps at my disposal. Finally I wish to thank most gratefully my friend Dr. Ecological Botany, U mea University and started Philip Tallantire, who has translated the manuscript in 1970. Most of the fieldwork was done during into English and also made valuable and wise criti­ the period 1972-197 5. cisms.

Acta phytogeogr. suec. 65 The investigated area

The 214 localities investigated are situated in the (summits at ea 1500-1800 m a. s.l.), is the land provinces of Sweden (Sw. 'landskap'), known as relief more alpine in character. Jamtland, Harjedalen and Dalarna, distributed Prominent features of many of the mountains, over an area of ea 40 x 200 km (Fig. 1) just east of due to nappes and other tectonic thrust features, the main watershed in the southern part of the are relatively gently-sloping and level W- and Scandes mountain chain in Central Sweden (63° NW-f acing slopes and steep E- and SE-facing 23'-61° 53'N lat.; 13° 34'-12° 03' E long.). slopes. This topographic feature is very impor­ tant because of its differential effect on the distri­ bution of the snow cover. Those forested or wooded valleys which are Topography, solid geology and present within the investigated area are generally drift deposits broad and more or less U-shaped. The valley bottoms seldom lie below an altitude of 600 m. This section has been compiled from information Within a wide central part of the investigated given in the following sources: Hogbom (1920), area, in Jamtland and the northern half of Haijeda­ G. Lundqvist (1951), Stromberg (1955, 1961), len, the solid rocks are various kinds of calcare­ Hj elmqvist (1966), Jan Lundqvist (1969). ous tectonites. Both eastward and westward of this The solid rocks have usually been eroded to zone biotite-rich greywackes occur, with transi­ yield rounded and smoothed landforms. Only on tions to quartzites. A few of the highest mountain the highest mountain massifs such as Helagsfjal­ summits are built of Sylarna amphibolite. From let, Sylarna, Snasahogarna and Harjangsfjallen the middle of Harjedalen down to the southern­ most investigated localities in Dalarna the under­ lying rocks include light-coloured feldspathic quartzites, augengneiss and blastomylonite, light-coloured sparagmites and Vemdal quartzite. The drift deposits above the birch forest-limit consist of moraine (including frost-shattered ma­ terial), various types of glaciofluvial deposits and, to a minor extent, of lacustrine sediments. The depth of all these superficial deposits decreases markedly with increasing altitude. The deglaciation chronology of the investigated area is not yet known in any detail, although it seems probable that most of the area had become ice-free by about 7000 BC (Jan Lundqvist 1973).

Climate Except where otherwise stated this section is based on data supplied by the Swedish Meteoro­ Fig. 1. Location of the investigated area (black) within logical and Hydrological Institute (SMHI, Norr­ Scandinavia. koping).

Acta phytogeogr. suec. 65 Change and stability of birch tree-limit in the Scandes 5

o oAre Duved ODalen

0bstersund

\ . • �)( �-· ' O Ljungdalen •IC J OStors ti j · •If)( � • � ,. . · . .. .. �- .11 � 0\ruksval�r na -c ...

Qljusnedal

oTannas • OHede 0 vskelasen M

Fig. 2. The sites of the investi­ 0 Lofsdalen gated localities in Jamtland and Harjedalen. e: localities at which an upward displacement of the tree-limit occurred. lo­ x: calities at which the tree-limit remained unchanged.

Fig. 3. The sites of the investigated localities in Dalar­ na. e: localities at which an upward displacement of the tree-limit occurred. localities at which the tree­ x: limit remained unchanged.

Acta phytogeogr. suec. 65 6 Le ifKullman

Continentality-maritimity and is considered to have a clear phytogeographi­ The relative proximity of the investigated area to cal relevance (Hintikka op.cit.; Jim Lundqvist the Norwegian Sea and the Gulf Stream condi­ 1968). The annual amplitude values for the normal tions a maritime-continental climatic gradient in a west-east direction across the area. Because of period 1931-60 for all the meteorological stations the hindrance to advection produced by the topo­ situated within the investigated area (Figs. 2-3) graphy to the west of the southern part of the are shown in Table 1. investigated area, a similar gradient , but in a Temperature north-south direction, exists hereabouts (Wal­ len 1968; Angstrom 1974). Local divergences For only a few of the above-mentioned stations from the broad pattern described above are, do continuous temperature records over long pe­ however, very probable because of the broken riods exist. The majority are typical valley-floor nature of the topography over the area as a whole stations and therefore it is uncertain to what de­ (Angstrom op.cit.). gree the data can be regarded as representative The thermic continentality-maritimity of the for the bioclimate prevailing at the tree-limit, al­ regional climate mentioned above is quite well though they probably indicate the regional trends correlated in Scandinavia with humidity (Hintik­ in the thermoclimate within the investigated area. ka 1963), in such a manner that areas with a Generally speaking, the valley stations probably local-maritime climate are characterised by gene­ have a more continental climate than that which rally humid weather and receive a relatively large prevails at the tree-limit (cf. Jim Lundqvist 1968). part of their precipitation in the form of snow. The annual mean temperatures and mean tri­ Those areas with a local-continental climate , on term values for the period June-August are shown the other hand, are subject to relatively dry con­ in Table 1. The station positions are shown in ditions and only a single seasonal maximum of Figs. 2-3 . precipitation, namely during the summer.· The annual temperature amplitude, i.e. the dif­ Precipitation ference in mean temperatures for the warmest The very broken nature of the topography leads and coldest months in the year, forms a good to very great differences in the precipitation fall­ indication of the character of the local climate ing at quite closely-situated localities.

Table 1. Climatic data for the meteorological stations within the investigated area. All are mean values for the normal period 193 1-60, excepting the length of the vegetation period (mean for 196 1-74). A: annual temperature (°C); B: temperature for the tri-term June-August (°C); C: annual temperature amplitude (°C); D: annual precipita- tion (mm); E: duration of snow cover (days); F: depth of snow remaining on May 15 (cm) ; G: date by which all snow had melted ; H: length of vegetation period (i.e. mean daily temperature ;?!':+6 °C).

Station: a.s.l. A B c D E F G H m Storlien 595 + 1.1 +10.00 19.3 1012 218 27 30/5 122 Duved 385 +1. 8 +12.07 23.4 656 188 2 ll/5 132 Dalen 480 427 179 5 10/5 Storsjo 575 +0.7 +11. 10 23.4 566 187 5 14/5 122 Ljungdalen 615 608 195 8 14/5 Bruksvallarna 700 570 216 12 22/5 Ljusnedal 585 +0.1 11.10 25.0 503 188 2 9/5 121 + Fjiillnas 795 -0.4 9.63 22.2 666 212 35 27/5 108 + Myskelasen 770 573 208 9 21/5 Hede 420 +0.9 +12.17 26.0 527 139 Lofsdalen 605 1.3 + 11.17 21.9 702 197 8 18/5 132 + Sveg 360 +2.1 +13 .07 24.9 574 177 0 1/5 146 Grovelsjon 815 +0.8 +10.37 20.0 636 201 11 22/5 Idre 450 574 Sarna 422 1.2 + 12.5 25.5 678 186 0 7/5 139 +

Acta phytogeogr. 65 suec. Change and stability of birch tree-limit in the Scandes 7

The annual mean values for all the relevant for a particular locality in terms of a predeter­ meteorological stations are shown in Table 1. The mined air temperature threshold value has any station positions are shown in Figs. 2-3. real meaning. The most adequate measure would naturally be a vegetation period based on physio­ Snow cover logical estimates of plant productivity parame­ ters. On practical grounds, however, the values None of the data for snow cover given for the for the length of the vegetation period at certain various meteorological stations have any great of the meteorological stations within the investi­ relevance for the conditions which prevail at the tree-limit, where the snow cover varies widely gated area (shown in Table 1) are based on the from place to place. The official figures do, how­ number of 24 hr-periods during which the mean air temperature equalled or exceeded + 6°C. The ever, provide some idea of the broad regional data are taken from Perttu & Huszar (1976) and trends within the area as a whole. are mean values for the period 1961-1974. The annual mean values for the duration of the Birches growing at the tree-limit have usually snow cover, the depth of snow present on May 15 become fully-leafed by the middle of June at each year, and the date for the disappearance of latest. By the middle of September or somewhat the snow cover, are shown in Table 1. All the earlier the leaves have usually turned colour. values are taken from Pershagen (1969) . The sta­ The start ofleafing, following the snowy winter tion positions are shown in Figs. 2-3. of 1975-76 was delayed. by ea 3 weeks at some Investigations by Melin (1943) and Ager (1964) localities, compared with the other years. How­ showed that in general the depth of snow increas­ ever, observations of these trees made during the es very greatly with increasing altitude. From the following summer gave no indications that the meteorological data it is clear that snow cover very delayed leafing had any deleterious effects persists longer in the northern and western parts of any kind. of the investigated area than in the southern and The assimilation period for tree-limit birch eastern parts. normally lasts about 80-100 days. To use the leafing data as an indication of the Wind direction macroclimate has little meaning, since the start of Ager (1964) has summarised the mean annual fre­ birch leafingcan be very much modified by other quencies for the various wind directions over the factors, e.g. the soil conditions. At sites where year for Storlien and Sarna (Table 2). Storlien has there is little depth of frozen subsoil (Sw. 'tjale') a locally maritime climate, as shown by the high­ leafing may occur at appreciably lower air tem­ er frequency of westerly winds, as compared to peratures than is the case at deep-frozen sites. Sarna, which with its more continental type of climate, has more equal values for the winds from all directions, although with a slight excess of Recent climatic fluctuation north-westerlies. During the 1880's the climate over the whole of the Northern Hemisphere started to become Length of the vegetation period warmer, now a well-established fact (cf. e.g. It is questionable whether the traditional practice Angstrom 1939, 1974; Hesselberg-Birkeland of expressing the length of the vegetation period 1940; Ahlmann 1943, 1948; Johnson 1965 ; Lamb

Table 2. Mean annual frequencies (%) of the various wind directions at Storlien and Sarn(\ during the normal period 1931-60.

Wind direction N NE E SE s SW w NW calm total

Station: Storlien 0.1 0.2 11.7 17.2 2.0 1.1 30.6 1.8 35.3 lOO Sarna 6.2 4.2 4.0 10.8 7.4 9.2 5.9 18.8 33.5 lOO

Acta phytogeogr. suec. 65 8 LeifKullm an

1965 , 1978 ; Liljequist 1970 ; Johannessen 1970; Climatic fluctuation within the Bolin 1974) . investigated area The climatic amelioration was caused by an increase in cyclonicity (Ahlmann 1948; Bliithgen 1966), possibly associated with an increase, since All the climatic date referred to below have been ea 1915, in the amount of extra-terrestrial solar supplied by SMHI, Norrkoping. radiation (FrydendahJ 1978) . Prior to about 1915 The yearly mean temperatures for the triterm the amelioration was primarily restricted to the June-August for two meteorological stations situ­ winter months, i.e. the climate became more ma­ ated within the investigated area are given in ritime. After that time the summers also became Figs. 4 and 5, viz. Storlien and Ljusnedal (for warmer and the climate became more continental position see Fig. 2). The position of the record­ in character (Wallen 1968) . ing instruments at Storlien was changed to a According to Johnson's (op.cit.) calculations minor degree in 1963 . During that year, how­ the degree of continentality (Conrad's continenta­ ever, observations were made at both the old and lity index) was appreciably greater during the pe­ the new locations and the meteorological data riod 1928-58 compared with the 1901-30 period. obtained showed virtually no difference at all. On This increase was particularly marked in those this account I consider that the use of data fr om parts of the investigated area which have a locally the old and new station localities in one and the maritime climate, e.g. Storlien, where the great­ same diagram (Fig . 4) is justified. Unfortunately est increase in degree of continentality was re­ no observations exist for Lj usnedal for the years corded. In mountain areas further south with a 1956, 1958, 1959, nor prior to 1917. climate of local continental character the change Storlien, at 595 m a. s. 1., represents the most was a relatively minor one. locally maritime part of the investigated area, The greatest temperature increases were re­ whilst Lj usnedal at 585 m, although situated in a corded in locally maritime areas relatively far to more continental area, is not representative for the north (Angstrom 1953); e.g. Eriksson (1943) the most continental part of the area. Both the reported that the annual mean air temperature for Storlien and Lj usnedal meteorological stations lie January at Jacobshavn in Greenland rose by tooc in the coniferous forest belt, 220 and 460 m, re­ between 1905 and 1936. In northern and central spectively, below the local tree-limit for birch. Scandinavia, however, the temperature changes The mean summer air temperatures at Storlien have been appreciably smaller. Generally speak­ show a clear upward trend up to 1914, followed ing, the values quoted for the mean temperature by a distinct temporary minimum at the start of increase during the winter period are of the order the 1920's. This same minimum is shown by the of 1-3°C (cf. e.g. Hesselberg-Birkeland op.cit.; Lj usnedal data. This picture of the course of the Liljequist 1943, 1950; Strand 1962). At Storlien, summer mean temperature wholly agrees with in the northwestern part of the investigated area, that given by Liljequist (1950) for Central Sweden the mean air temperature for the months June­ in general. August rose by 1.4°C as compared with the de­ During the decade 1921-1930 the June-August cadaJ means for 1901-19 10 and 1931-1940. The temperatures fluctuated quite markedly at both trend towards increasing warmth in summer stations (cf. Liljequist op.cit.). Three extremely seems to have halted about 1950 (Liljequist 1970 ; warm summers in a row occurred in 1925, 1926 Lamb 1974). and 1927. A clear temperature maximum is The use of periodic mean values of air tempera­ shown for the decade 1931-1940, followed by a ture may nevertheless serve to obscure certain weak decline thereafter. conditions which are of vital importance for bio­ The mean decadal summer temperatures (tri­ logical phenomena. It is therefore desirable that term June-August) for Storlien and Lj usnedal climatic trends should be described in terms of have been set out in Tables 3-4, together with an frequencies of temperature extremes (cf. Ang­ indication of the number of times per decade the strom 1942; Bryson et al. 1970; Climate Monitor mean temperature equalled or exceeded certain 1977). extreme values. The data for the period 1963-

Acta phytogeogr. suec. 65 Change and stability of birch tree-limit in the Scandes 9

'c

10

1901 1905 1910 1915 1920 1925 1930 1935 1940 1945 1950 1955 1960 1965 1970 1975

Fig. 4. Annual mean air temperatures (190 1-1975), for the triterm period June-August, fo r Storlien (595 m a.s.l.) meteorological station .

10

1917 1920 1925 1930 19·35 1940 1945 1950 1955 1960 1965 1970 1975

Fig. 5. Annual mean air temperatures (1917-1975) for the triterm period June-August, for Lj usnedal (585 m a.s.l.) meteorological station.

1972 are all derived from the re-located station at temperature culminated during the decade 1931- Storlien. Judging fr om the values obtained during 40. The unique character of this decade stands the summer of 1963 , in which both the old and out most clearly, however, when the frequency new station were operated, it is possible that the data for certain extreme temperature values are mean summer temperature values fo r the new examined (11 oc for Storlien, the 11 o and l2°C station are on average a fe w tenths of a degree values for Ljusnedal). Neither earlier nor later centigrade lower than they would have been at during the whole period 1901-1975 has such a the former station. consecutive sequence of extremely warm sum­ Tables 3-4 show that the trend of increasing mers occurred as during the abovementioned de-

Acta phytogeogr. suec. 65 10 Leif Kullman

Table 3. The decadal mean temperatures (June-August) re­ Table 7. The decadal mean temperatures for September re­ corded at Storlien (595 m a. s.l.), showing the number of corded at Storlien (595 a. s.l.), showing the number of m years within each decade when the triterm mean equalled or years within each decade when the September mean equalled exceeded 10°, llo and l2°C, respectively. or exceeded 5°C and 6°C, respectively.

Period June-August Period September mean (0C) woe ll°C 12°C mean (0C) 6°C 7°C

1901- 1910 9.23 3 1 1 1901-1910 6.25 5 3 1911- 1920 10. 14 4 3 0 1911-1920 5.70 5 2 1921-1930 9. 54 5 3 1921-1930 5.85 3 1 1931-1940 10.65 7 6 1 1931-1940 6.25 5 3 1941-1950 10.41 7 2 0 1941- 1950 7.00 9 3 1951-1960 10. 18 5 3 1951-1960 6.65 7 4 1963-1972 10.24 5 3 1963-1972 6.10 4 3

Table 4. The decadal mean temperatures (June-August) re­ Table 8. The decadal mean temperatures for September re­ corded at Ljusnedal (585 a. s.1.), showing the number of corded at Ljusnedal (585 m a s.l.), showing the number of m years within each decade when the triterm mean equalled years within each decade when the September mean equalled or exceeded ll0, 12° and l3°C, respectively. or exceeded 6°C, 7°C and 8°C, respectively.

Period June-August Period September mean CC) ll°C l2°C 13oC mean (0C) 6°C 7°C 8oC

1921-1930 11. 13 5 4 1 1921-1930 5.95 5 2 0 1931-1940 12.15 9 6 I 193 1-1940 6.50 5 4 2 194 1-1950 11.58 7 2 1 194 1-1950 6.18 8 3 2 1963- 1972 10.63 6 0 1963-1972 6. 18 5 2 0

cade (cf. Lysgaard 1963). If the temperature for Table 5. The decadal mean temperatures for May recorded at the individual years of this decade are examined, Storlien (595 m a. s.l .), showing the number of years within it is clear that the period 1933-1939 marks the each decade when the May mean equalled or exceeded so and 6°C, respectively. culmination of the climatic amelioration. This unique sequence of meteorologically ex­

Period May mean tremely warm summers most probably entirely (OC) 5°C 6°C altered the chances of colonisation in new margi­

1901-1910 2.90 2 0 nal habitats of populations of such plants which 1911-1920 4.05 4 3 show distributions conditioned by a factor com­ 1921-1930 3.30 3 I plex of temperature-soil moisture. 1931-1940 4.15 3 1 1941-1950 3.65 2 After 1945 the mean temperature for the sum­ 195 1-1960 3.85 2 2 mer period, June-August, appears to have en­ 1963-1972 4.53 6 1 tered a declining phase. This is particularly marked as regards the frequency of extremely warm summers. Nevertheless, the temperature

Table 6. The decadal mean temperatures for May recorded at conditions prevailing at the turn of the 19th cen­ Ljusnedal (585 m a. s.l.) showing the number of years within tury have not yet been reached. each decade when the May mean equalled or exceeded 6°C, 7oc and 8°C, respectively. The mean June temperature for the period 1961-74 is higher than that for the period 193 1-60

Period May mean in the southern part of the Scandes (Perttu & (OC) 6°C 7oc 8oC Huszar 1976).

1921- 1930 5.35 4 2 0 The decadal values of the mean temperature in 1931-1940 6.25 6 I May are shown in Tables 5-6, together with the 1941-1950 5.85 5 2 I number of times per decade the mean May tem­ 1963-1972 5.82 3 0 perature equalled or exceeded certain extremes.

Acta phytogeogr. suec. 65 Change and stability of birch tree-limit in the Scandes 11

Fig. 6. The distance between this hillslope and the nearest summer-farm has at no time been less than 15 km. Former livestock grazing here can there­ fore be ruled out. Nor are there any signs of former Lapp occu­ pation of the area, reindeer fences etc. The hill slope re­ ceives a heavy snow cover (see Fig. 28) and becomes snow-free relatively late on in spring. The explanation for the observed rise in the tree-limit, therefore, is to be found in the general change in snow conditions known to have occurred in the investigated area during the present century. Both the birch forest-limit and the tree-limit run evenly across the entire hill­ slope and coincide pretty well with the upper limit of the ava­ lanche cones . Higher up there is an obvious lack of fine-grade mineral matter in the soils, which has probably prevented the birch from ever attaining a higher altitude. Photo: August 5, 1977.

The tabulated values show that both the mean impossible to adduce any statistically significant temperature value for May and the frequency of change for the mean annual precipitation for north­ warm Mays rose after the turn of the present em Sweden during the periods 1861-1900 and century. The maximum was attained somewhat 1901-1930. He nevertheless considers it probable later than the corresponding maximum for the that the increase in strength of the atmospheric summer (June-August) mean temperature. It is circulation during the 20th century did result in clear that the greatest positive deviations from increased precipitation in mountainous regions. the ov:erall mean are shown by the temperature At the majority of the meteorological stations in values for the locally maritime Storlien area dur­ northern Sweden the mean annual precipitation ing the most recent decades. increased during the period 1931/32-1958/59 The decadal means of September temperature according to Ager ( 1964). are shown in Tables 7-8, together with the Indications that climatic fluctuation of the pre­ number of times per decade that the September sent century also involved an increase in precipi­ mean temperature equalled or exceeded certain tation in the north of Scandinavia have been pre­ extremes. It is clear from these figures that the sented by, e.g. Ostman & Henriksson (1942), Jo­ climatic amelioration, with regard to September hannessen (1942), Wallen (1968), Rudloff (1967), mean temperature, culminated before or about Lamb (1974) and Heino (1978). 1950. At the meteorological stations Storlien, Sveg So far as the existence of any similar differen­ and Sarna within the investigated area (for posi­ ces in precipitation during the 1900's is concerned, tions see Figs. 2-3), mean annual precipitation in the picture is still rather confused. According to the decades after 1920 was higher than during the Schytt (1973) there are no definite indications at preceding 2-4 decades (Andersson 1970). Never­ all that a reduction in winter precipitation has theless, because of the methodological difficulties taken place. Angstrom (1942) considers that it is attending the recording of representative precipi-

Acta phytogeogr. suec. 65 12 Leif Kullman tation values (Angstrom 1941b, Hare 1971), all conclusions drawn about trends in precipitation are uncertain. Because the present climatic fluctuation was initiated by a change in the pattern of the atmo­ spheric circulation one might reasonably expect to findthis reflected in changes in the frequencies of the various wind directions over the years. At RS}ros in Norway , ea 60 km to the west of the investigated area, Johannessen (1942), in a com­ parison of the wind data for the periods 1886- 1895 and 1926-1935, found that there had been a marked decline in the frequency of northerly winds and a considerable increase in the frequen­ cy of westerly winds. For the other wind direc­ tions, as for calm air conditions, there had been Fig. 7. The highest-lying stands of Scots pine (Pinus small increases overall (cf. Johannessen 1970). sylvestris) have often been thinned out by forest fires, or by deliberate timber fe lling. In consequence, the lower limit of the birch forest belt has thereby been artificially lowered at many places . The photograph shows the burnt stub of a felled pine situated (655 m Main features of the vegetation a.s.l.) just below the pine tree-limit on the N-facing slope of Lillhammaren in Jamtland. Photo: July 6, The investigated area lies wholly within the 1976. 'Northern Boreal Zone' (Ahti et al . 1968). At virtually all the localities the birch is the tree species which forms the uppermost forest-limit such as insect plagues, or human destruction etc. and the tree-limit below the open vegetation co­ (see Kullman 1976a and b). ver of the mountain slopes (Sw. 'kalfja.ll'), ex­ The mountain birch forests of the investigated cept in a very few places (see Kullman 1976b). region correspond quite well with those of Ha­ The tree-limit declines gradually from a maxi­ met-Ahti's (1963) 'continental subalpine' and mum altitude of ea 1100 m in the southern part of 'oceanic subalpine' subzones. The birch forests the investigated area, to ea 800 m in the predomi­ of the former sub zone type are best developed in nantly maritime parts lying fu rther to the NW. the southernmost part of the area where , as men­ The subalpine birch belt, which lies between tioned above, the climate is drier and the soil­ the tree-limit and the closed coniferous forests conditions poorer. The detailed differences be­ lower down, varies widely in vertical extent. In tween the different types of mountain birch forest the southernmost parts of the area, with those in the area are summarised in the accounts by localities which receive the smallest amounts of Smith (1920) and Samuelsson (1917). snowfall , it may be virtually absent , whereas in The coniferous forest-limit is almost every­ certain valleys further north, with an abundant where formed by the spruce (Picea abies (L.) snowfall, the altitudinal range of the birch belt Karst.), although at a fe w localities in Dalarna the may be 200-250 m. Scots pine (Pinus sylvestris L.) forms the conife­ The boundary between birch forest and rous forest-limit . In places near this limit the coniferous forest has .in many places been Scots pine sometimes increases in importance on artificially depressed by human interference and the otherwise spruce-dominated forested slopes. by forest fires (see Fig. 7), both natural and deli­ On certain N-facing slopes spruce may form pure berate (see Kullman 1976a). stands. It has been postulated that the continuous exi­ The vertical zonation of the vegetation over a stence of certain types of mountain birch forest large part of the investigated area has been stu­ depends on the occurrence of periodic disasters, died by Kilander (1950, 1955, 1965). He deter-

Acta phytogeogr. suec. 65 Change and stability of birch tree-limit in the Scandes 13

mined the upper altitudinal limits for the alpine area there are large tracts of lichen heaths (Cla­ vegetation belts (see e.g. Sjors 1963) to be as donia spp.). On well-drained slopes which re­ follows: low alpine belt 1300--1400 m; middle ceive a deep, but not too long-lasting, snow-cover alpine belt 1600 m; high alpine belt > 1600 m a. the landscape is dominated by metre-high willow s.l. Only a few of the higher mountain summits in thickets (Salix lapponum, S. glauca and S. the area include the high alpine belt. lanata), with scattered junipers (Juniperus com­ The vegetation within the tree-limit ecotone, munis). Only in the northwestern part of the in­ i.e. the tract between the forest limit and the vestigated area, where the maritime influence is tree-limit of birch, is very varied in character. relatively strong, do mire communities play any Dwarf-shrub heaths, in which Vaccinium myrtil­ particular role within the vegetation of the tree­ lus, Empetrum hermaphroditum and Betula nana limit ecotone. alternate as dominants, cover wide areas. Where More detailed accounts of the vegetation of the the snow-cover is longer-lasting and the supply of area can be found in several of the works already seepage from the snow-melt is more permanent mentioned (Smith op.cit.; Samuelsson op.cit; Ki­ and of longer duration grass heath and snow­ lander op .cit.). A recent and detailed vegetation patch communities, of mountain meadow or map , with accompanying text, exists for one, re­ heath character, occupy relatively large areas in­ latively limited, part of the area, the Ottfjall stead. mountain massif (Warenberg 1977). In the southernmost part of the investigated

Acta phytogeogr. suec. 65 Human impact around the tree-limit

In certain cases below, descriptions and maps During the later part of the Iron Age, 700-ca from former land surveys such as the delineation 1000 AD, there was marked expansion of of crown and private land (Sw. 'avvittring') and settlement within the area. The remains of enclosure awards (Sw. 'laga skifte '), made during small-scale dwelling-sites probably only seasonal­ the 19th century are referred to. These docu­ ly occupied, have been found at many places at ments are kept at the County Archives, at the the present-day altitude of the birch forest belt Land Survey Office of Jamtland province at Os­ (Hallstrom 1931, 1944; Janson et al. 1962). It is tersund. A list of all my informants about former therefore not entirely inconceivable that the prac­ land usage within the investigated area is given in tice of shieling (summer-farming, Sw. 'fabod­ Appendix I. vasen ') originated fr om the activities of Iron Age farmers at these altitudes (Jan son et al., op.cit.; Selinge 1976). Skj�lsvold (1969), however, is Prehistoric time critical of this early dating of shieling and consi­ ders that hunting and fishing were still the most important economic activities during the Iron Far too little archaeological research has yet been Age. carried out in the southern part of the Swedish It is admittedly impossible, today, to decide to Scandes. However, archaeological remains from what extent the vegetation in general and the hunting, fishing cultures with a neolithic mode of tree-limit in particular were affected to any per­ life have been known for a long time in many manent degree by the prehistoric cultures men­ places within the investigated area. These finds tioned above (see Kullman 1976a). One pheno­ were formerly considered to belong chronologi­ menon which is well worth noting in this connec­ cally to the Younger Stone Age, i.e. post 3000 tion, and one which often occurs when such areas BC. Nowadays it is thought to be fairly certain become settled, is a drastic increase in the frequ­ that human activity occurred in the area as far ency of fo rest fires(cf. e.g. Lutz 1959; Zackrisson back as the Older Stone Age, 4-5000 BC (Christi­ 1977) ansson 1969; Selinge 1976) . The majority of the occupation sites have been found along the shores of lakes and rivers, though sites at the Historic time tree-limit are by no means unknown. The commonest archaeological remains within Permanent settlement the area are pit traps for animals (Sw. 'fangst­ grop'). That certain of these date from the Stone Permanent settlement within the investigated Ages cannot be ruled out, but the majority are area, in most cases 3-400 m below the present probably more recent. These pits were intended tree-limit, dates fr om the early part of the Middle to trap elk and reindeer. In many places there are Ages (Selinge op.cit.). intricate systems of pits which extend from the During the 17th and above all, the 18th century, tree-limit on one side of a valley to that on the another quite widespread settlement phase set in, other (Manker 1960 ; Selinge 1974 ; Jenssen 1977). partly as a consequence of the discovery of To judge from the results of radiocarbon datings workable copper and iron ore deposits here and of these pits (Selinge op.cit) there are grounds there in the investigated area. Both the mining of for thinking that the investigation area was visited the ore and its processing necessitated the local by hunters as long ago as the Bronze Age . felling of large quantities of timber for fu el and

Acta phytogeof?r. suec. 65 Change and stability of birch tree-limit in the Scandes 15

charcoal. This may have led to changes in the relative proportions of tree species in the forest, especially perhaps in the region between the coni­ ferous forest and the mountain birch forest belts (Hiilphers 1777; Hvarfner 1961 ; Kullman 1976a). There are indications from this period of a high frequency of forest fires (Kullman op.cit.), al­ though the prevailing climatic conditions at this time were probably a contributory factor (cf. Zackrisson op.cit.)

Shieling practice

In about the 17th and 18th century an extensive development of shieling commenced in the

mountains beyond the farming settlements (cf. Fig. 8. The Axhogvallen shieling (summer-farm) in e.g. Hiilphers 1762, 1777; Linden 1974 ; Hallinder Harjedalen, at ea 860 m a.s.l. Most other shielings 1977) . usually lay at a greater vertical distance below the Every family in a farming hamlet (cluster of tree-limit than this one. Very good quality grazing land was often accessible in the forest quite close to the farmhouses, Sw. 'by') in the valley bottom had at huts, wherefore the area close to the tree-limit was least one summer farm (Sw. 'fabod'), although as probably, at most, only sporadically grazed. Photo: a general rule they had 2-3 shielings, situated at July 29, 1973 . . different distances away from the home farm and grazed successively throughout the summer and ing area might be extended, on certain days, bey­ early autumn. Some of these multiple shielings ond the forest-limit up on to the open uplands. were only used in alternate years . The summer Livestock grazing , in other words, has regularly farms were usually occupied from the middle of occurred at and above the tree-limit at certain of June until the time of the first snowfalls in the the localities within the investigated area (Kell­ autumn, usually in October. Although each fami­ gren 1892 ; Lampa 1910; Boethius 1931; Frodin ly had its own shieling the farmers from each 1952). valley hamlet usually built their huts in the same Maps and descriptions made in connection place, such that similar clusters of dwellings with the middle and late 19th century land sur­ arose on the mountain pastures as down in the veys (inter alia the Sw. 'laga skifte' and 'avvitt­ valleys (Sw. 'fabodbyar'). ring') indicate that the land situated above the Within the investigated area the shielings were forest-limit was generally classified as 'wilder­ always situated in the mountain forest belt, never ness', from the grazing point of view. The main at the tree-limit itself or on the bare uplands grazing area was undoubtedly the mountain birch above (see Fig. 8) as was frequently the case on forest belt (local informants; cf. also Frodin the Norwegian side of the border mountains op.cit.). (Frodin 1919, 1929, 1952; Kilander 1942; Rudberg The majority of the local informants considered 1957). Scarcely any of the shielings lay higher that the livestock had not had any particular in­ than 100 m below the local tree-limit. fluence on the woody vegetation. Damage, due mainly to grazing by goats and sheep, had only been observed locally in the immediate vicinity of Upland grazing the huts. The livestock, i.e. cows, sheep and goats , grazed Compared with cows and horses, goats and on the generally unfe nced (Bryng 1968) common sheep graze closer to the ground and are more grazings, within a radius of 2-3 km from the aim­ selective in their choice of trees and bushes huts (local informants). In those parts where (Steen 1958; Baadshaug 1974 ; Wielgolaski 1975). forb-rich willow thickets were present� the graz- Certain of the older informants seemed to re-

Acta phytogeogr. 65 suec. 16 Leif Kullman member that grazing goats and sheep held back When considering the quantitative aspects of the development of young birches growing in vi­ livestock grazing, the very wide extent of the cinity of the almhuts. grazing areas must always be borne in mind. With Kellgren (1892), an agricultural botanist who the aid of information from the local population, studied the conditions in the area, noted that the about the number of animals of different kinds young foliage of birch was very attractive to live­ which were grazed on the shielings and the ap­ stock. The same author (1893) also stated that the proximate area of the grazings, I have calculated birch's worst enemy was domestic livestock. that within some of the most intensively grazed Anonymous (1906) relating his or her experiences parts of the investigation area (in western Harje­ within a small area in western Harjedalen, inter­ dalen) at the height of the shieling phase (ea preted the localisation to dense juniper and wil­ 1895), there was a grazing density of about 5 cows low thickets of birches growing at the tree-limit as and 5 goats, and perhaps a few more sheep, per being an expression of the high intensity of graz­ km2. Liibeck (1920) considered that a density of ing. 50 livestock per km2, in the upper part of the It is well known from other regions that grazing coniferous belt, is sufficient to make the estab­ by livestock can more or less entirely prevent lishment of seedlings impossible. effective regeneration of birch from seed (Chard No deliberate attempts were made to improve 1953; Bjor & Graffer 1963 ; Kinnaird 1968, 1974). the grazing areas. Hellbom (1884), namely, points Against these negative effects of grazing should out that in the pretty heavily grazed hill area of be set for example, the positive effects of tramp­ Svansjofjallet (Rutfjallet) in western Harjedalen ling, which certainly improves the chances for ''fallen trees and shrubs are left to moulder seed germination and establishment (Bjor & Graf­ away" (transl. from Swedish), in contrast to the fer op.cit.; Kinnaird 1968; Dunwiddie 1977). This state of affairs in those parts of the mountain is an important factor in any area close to the birch forest from which hay crops were obtained. distributional limit for a species, where a closed vegetation cover may greatly inhibit regeneration from seed (cf. Hintikka 1963). Burning fo r grazing improvement Within the investigated area, the fact that the field-layer vegetation of the tree-limit ecotone Burning for grazing improvement (Sw. 'betes­ and below in the shieling areas was generally lush branning') proved to be virtually unknown, ex­ in character, renders it less likely that livestock cept in a few cases, to local people in the area would selectively graze on the young stages of whom I interviewed (cf. Kullman 1976a). birch (cf. Selsjord 1966). Henning (1895) noted the presence of birch seedlings just below the tree-limit at Storlien despite of quite a heavy graz­ Hay-making ing intensity (local informants; Hedberg 1939). The general indications are that livestock did A very important intent with the practice of shiel­ not deliberately graze birch seedlings and sap­ ing transhumance was the harvesting of winter­ lings (cf. Rolsted 1931). fodder for the livestock. According to Barth (1886) birch seedlings pos­ In most places the hay made from sloping fens sess some kind of chemical defence mechanisms accounted for the major part of this winter fod­ against being grazed. This does not seem an un­ der. A study of the descriptions and maps from reasonable suggestion, considering the analogous the older land surveys ('avvittring', 'laga skifte') feature following birch defoliation by larvae of reveals that practically every mire in the investi­ the geometrid (Peppered) moth ( Oporinia autum­ gated area was cut for hay. Even quite small nata) (see Haukioja 1976, 1977). According to mires, which lay well above the tree-limit and Wielgolaski (1975) the increase m lignin content tens of kilometres away from the almhuts were of the leaves and shoots of certain woody plants visited and utilised for winterfodder production. during the vegetation period explains their unpa­ As a general rule the mires were only cut for hay latability (cf. also Arnold 1964). every other year (e.g. Oster 1936).

Acta phytogeogr. suec. 65 Change and stability of birch tree-limit in the Scandes 17

The woody vegetation growing on the upland Tree fo liage harvesting mires which were cut for hay was to a certain One form of fodder harvesting which is even extent regularly cleared (Frodin 1927 , 1952; older than hay-making is the cutting and drying of Kvarning 1961). As hay-making has now virtually tree foliage (Sw. 'lovtakt'; see Malmstrom 195 1). ceased on these subalpine fens, the drier parts of The majority of my local informants within the many are nowadays rapidly becoming overgrown investigated area were well-acquainted with this by shrubs and trees (cf. Moen 1976,). Neverthe­ activity, which is also well-documented from this less it is difficult to imagine that such hay-cropp­ same area (e.g. Kellgren 1892; Forsslund 1919; ing can have led to any widespread depression of Jirlow 1945; Oster 1936; Rudberg 1957; Kvarning the birch tree-limit, since the extent of such mires 1961). The dried birch foliage was primarily in­ at this level is in general quite insignificant in tended as fodder for the sheep and goats. Usually most parts of the investigated area. branches were cut, but sometimes whole young Certain types of highly-productive mountain trees, 2-3 m tall. birch forest, with a field-layer dominated by gras­ Verbal information suggests that such foliage ses and forbs, were also regularly cut for hay harvesting was even carried out at the forest-limit (local informants; bster 1936; Jansson 1951). In and at the tree-limit, although the main harvest these areas the vegetation structure and produc­ was taken from the lower-lying forest areas, tion potential was maintained by the systematic nearer to the permanent farmsteads. removal of older, more or less dying, tree trunks (see Hellbom 1884). However, as a general rule hay-making of this type has quite certainly not Cheese-making been carried out near to and above the forest-li­ Cheese-making at the summer-farms demanded mit (local informants). large supplies of firewood, which led to a certain thinning-out of the birch forest in the immediate Lichen-harvesting vicinity of the huts (Jarnefors 1932) . There are no indications, however, that any shortage of these A large part of the winter fo dder for the livestock firewood supplies arose which might have led to consisted oflichens (Cladonia and Cetraria spp.). tree-felling at either the forest-limit or the tree-li­ Where such lichen-rich areas existed, large quan­ mit. tities were raked off in the autumn. Wherever Kellgren (1893), quite definitely maintained practicable such lichen-harvesting was also car­ that such direct anthropogenic activities in the ried out at the tree-limit or above (local infor­ investigated area had had no effect on the natural mants; Hi.ilphers 1777; Kellgren 1892; Kellgren & altitudinal limit for birch. Nilsson 1893; Oster 1936) Since both the settled farming population and the nomadic Lapps com­ peted for these upland lichen stocks, the likely Decline of shieling practice result was a total devastation of this natural re­ source over certain areas (cf. Kullman 1975). Prior to the Land Enclosure Acts (Sw. 'laga skif­ Geijerstam (1891), for instance, stated that "for te') of the close of the 19th century, the grazing tens of kilometres at a stretch the uplands have areas attached to the shielings were used jointly turned dark" (transl. from Swedish) due to by the individual farming hamlets. The effects of over-harvesting of the available lichen stocks. the enclosure awards made such continued joint Similar opinions were put forward by Kellgren utilisation of the grazings and of the shieling (1893), Bergman (1948) and Berg (1952). hay-meadows and huts impossible, and led to the At most of the investigated localities, however, abandonment of many shielings. This meant a re­ lichen-dominated communities can by no means duction in both the extent and intensity of all the have existed at the tree-limit at the turn of the various activities which have been described century. Thus, the practice of lichen-harvesting is above. To see livestock grazing in the mountain definitely a negligible factor for the present inves­ birch forests nowadays is quite an occasion (Fig. tigation. 9).

Acta phytogeogr. suec. 65 18 LeifKullm an

far from any known shielings that any effects due to the grazing of their livestock can be ruled out entirely (see Fig. 6) . As indicated above, shieling activity was al­ ways concentrated within the birch forest belt. Although the vegetation at the tree-limit may have been affected locally, this can scarcely have led to any general depression of the forest- or tree-limits for birch within the investigated area as a whole (cf. Rudberg op.cit.). This conclusion is supported by the fact that neither Smith (1920) nor Kilander (1955, 1965), both of whom studied the altitudinal limits for birch within areas in which shielings were still in existence, mention Fig. 9. Nowadays livestock grazing near the tree-limit either grazing or hay-making as important factors is a relatively rare phenomenon within the whole of the investigated area. The cattle visible in the photograph affecting these altitudinal limits. are grazing in a ravine just above a summer-farm (Ny­ vallen) on the slopes of Mt. Sonfjallet. Thereis quite a growth of birch saplings in the ravine and it cannot be Lapps and reindeer grazing entirely ruled out that they are held back by being A potential factor which may have lead to an browsed on, in which case grazing may perhaps have prevented the birch colonisation here which would artificial depression of the tree-limit at certain have been expected to have resulted from the earlier localities is the nomadic culture of the reindeer disappearance of the snow-cover during the present Lapps (see e.g. Ruden 1911; Barth 1915). Holm­ century. Photo: August 15, 1974 . gren (1912), however, dismisses this contention as largely groundless and instead places the Hay-making on the upland sedge-mires and fo­ blame on damage caused by mass-outbreaks of rest in glades has gradually ceased from the turn insect larvae, snow avalanches etc. of the present century onwards (local informants; More recent investigations have nevertheless Kilander 1940, 1942; Kvarning 1961). The furth­ more or less convincingly shown that in fo rmer est distant and least productive areas were fi rst to times the Lapps had an unfavourable influenceon be abandoned. From the late 1940's or early the forested areas in the vicinity of their camp 1950's, hay-making has virtually stopped in the sites (e.g. Selander 1950; Hultblad 1968). upland areas (local informants). Harvesting of Written sources exist which indicate that lichen fodder seems already to have ceased in Lapps practising a domestic reindeer economy Jamtland during the 19th century, although in were present in the investigated area in the mid- parts of Harjedalen and Dalama it was still prac­ 17th century (e.g. Wiklund 1928). There is a pos­ tised during the early decades of the present cen­ sibility that the Lapps did not come into the up­ tury. This decrease in the harvesting of lichens, land parts of Dalarna before the 18th century like that of birch foliage , seems generally to have (Huss 1959). From a study of place-name tradi­ taken place earlier than the decline in hay-making tions, Bergsland ( 1970) has found cause to sus­ in the uplands (Oster 1936; Frodin 1952; Kvar­ pect that there may have been Lapps present in ning op.cit.). the investigated area as early as the 14th century. Although certain shielings were in existence for Prior to the revised Reindeer Grazing Act of several centuries, the great majority were in fa ct 1928, the Lapps could in principle utilise the fa ­ only established towards the end of the 18th and rested land within their own areas in any ways during the 19th century, in connection with the they wished, i.e. for firewood, for fe ncing posts, spread of settlement up into many upland valleys fo r building timber etc. Under the terms of the (Kilander op.cit.; Rudberg 1957). revised Act such utilisation could only be made It is important to emphasize that a large num­ with the permission of the State foresters and ber of the investigated localities are situated so only made where there were no grounds for fear-

Acta phytogeogr. suec. 65 Change and stability of birch tree-limit in the Scandes 19

Fig . 10. Visible signs of the former activities of Lapps in the investigated area are to be found in general on fairly flat terrain quite some way below the 1915/16 tree-limit (PTL). The oval patch of treeless ground visible on the left-hand side of the hillslope (arrow) in the photograph (850 m a.s.l.) has re­ sulted from tree-felling by Lapps for their habitations and reindeer fe nces . There is hardly any reason to believe that in this well-forested and steep envi­ ronment the Lapps ever specifi­ cally sought out the tree-limit as their source of timber supplies , or carried out any systematic felling of large areas of forest here. The W-facing slope of Lill-Stensdalsfjallet (locality 78). Photo: June 30, 1974.

ing that a lowering of the forest-limit would result ioned nomadism, with regularly shifting camp (Cramer & Prawitz 1970). sites, became replaced by a more permanently­ The reindeer economy practiced prior to about settled form, with fixed dwellings situated at a 1925 was more intensive in character, i.e. the considerable distance below the tree-limit. This individual reindeer herds were smaller than those new type of reindeer economy was considered to of today, but the degree of domestication was obviate the risk of over-grazing, previously a appreciably higher. The herd was kept much permanently present hazard (Manker 1945, 1947). more together and when being moved from one Selander (1950), however, states that, at least in grazing area to another the whole Lapp family southwestern Lule Lappmark in N Sweden, the followed along. The reindeer were strictly and effect was the exact opposite . Under the exten­ permanently herded on the grazings and were sive type of economy the reindeer herds became driven home to the camp site every night fo r larger and during the height of the summer graz­ milking inside fe nced paddocks, which were ing conditions sometimes led them to concentrate often built of close-set vertical birch stems. Such on particular areas (cf. also Hultblad 1968). fences necessitated cutting of large quantities of Despite all the information reported above, my birch from the fo rest (Ruong 1937; Manker 1947) . opinion remains that fe lling and cutting of birches Each family (or a fe w families together) often by the Lapps have only very locally within the possessed several such paddocks, which were investigated area led to any reduction in the alti­ used in rotation (Ruong 1954). H�rbye (1861) tude of the tree-limit. The older remains and signs considered that the cutting of birch by the Lapps of Lappish culture which I myself found, or in the mountain areas had a deleterious effect, which have been shown to me by local Lapps, in leading to patches of open forest here and there the great majority of cases lay a good way below on the birch-covered hillslopes. the present-day tree-limit (cf. Kullman 1975 and During the 1920's the reindeer economy chang­ Fig. 10). At several of the investigated localities it ed its nature and became much more extensive in is clear that the terrain in the vicinity of the tree­ character. The reindeer were no longer milked limit is far too steep to have been suitable for and were not so carefully herded. The oldfash- camp sites, milking paddocks etc . Instead , the

Acta phytogeogr. suec. 65 20 Le if Kullman traces of Lappcul ture visible in nature are on flat deer selects only the uppermost and youngest areas, e.g. fluvioglacial outwash plains, quite shoots. Furthermore, food preference changes obviously at a lower altitude than that of the frequently during the snow-free season of the tree-limit as it was at the turn of the present year (Skuncke 1963 ; Steen 1966; Gaare & Skog­ century. land 1975). The greatest potential danger to the tree-limit Reindeer grazing at the tree-limit is, and was in most probably was grazing by the reindeer. Mo­ the past of fairly short duration and is mainly dern food-habit investigations have confirmed concentrated to the spring and autumn seasons. that birch leaves and buds form an important part The majority of the summer grazing grounds were of the food of reindeer during the snow-free sea­ up in the mountains well above the tree-limit son of the year (e.g. Skuncke 1963 ; Kallio & (Hogstrom 17 41; Ruong 1969) . Lehtonen 1973; Haukioja & Heino 1974; Waren­ There is also a possible positive effect connect­ berg 1977). Markgren (1961) considers that in ed with reindeer grazing which should not be Swedish Lappland the vertical spread of the birch neglected, viz. the trampling. This serves to dis­ is quite obviously hindered by reindeer grazing. rupt any continuous surface layer of raw humus A large part of the seedling crop derived from and exposing and breaking up the mineral soil seed germination above the tree-l imit is thought over a multitude of smallpatc hes. This should aid to be browsed off by the reindeer (cf. Bliithgen in the regeneration of birch from seed (Helle 1960). 1966; Kallio & Makinen 1978). In the subarctic birch forests of northern Fin­ When assessing the evidence presented in re­ land, Kallio & Lehtonen (op.cit.) have shown spect of the present investigation one should bear that reindeer grazing may effectively prevent re­ in mind that, although reindeer grazing is exten­ generation by seed of areas of birch forest killed sive during the snow-free season, this does not off by the attacks of the larvae of the geometrid apply to the very earliest and very latest snow­ moth (Oporinia autumnata). free vegetational types, which are both subject to Hoglund & Eriksson (1973), from their investi­ highly intensive grazing (Steen 1966; Warenberg gations in the upland parts of southern Harjeda­ 1977). len found that local, extremely intensive, rein­ Quantitative data on the importance of reindeer deer grazing was capable of reducing the area grazing for the population dynamics of birch covered by birch forest by about two-thirds. growing at its altitudinal limit are virtually non­ Helle ( 1966) , working in Finland, found that existent. Haukioja & Heino's (1974) study of the dense herds of reindeer cause damage to birch subarctic birch forests of northern Finland never­ seedlings (cf. also Kallio & Makinen 1978), but theless suggests that the greatest effect of rein­ that this damage was restricted to extremely limit­ deer grazing on the birch sta nds occurs a short ed areas and had no effect on the situation in distance below the tree-limit. general. Even an approximate estimate of the possible Interviews made with the local population of fluctuationswith time in the intensity of the graz­ the investigated area indicated quite clearly that ing pressure at every single one of the investigat­ reindeer regularly browse on the foliage of trees ed localities is qu ite impossible. A general im­ and shrubs, although grazing of saplings had only pression can nevertheless be gained by consider­ been observed by a fe w people. I have myself ing the known variation in the total reindeer stock found birch saplings, 10-20 cm in height, at seve­ within the investigated area at different times. ral localities within the investigated area, which The only change in reindeer numbers which were thickened basally in a manner which accord­ has been drastic enough to possibly have had an ing to Kallio & Lehtonen (1973) is an indication effect on birch regeneration considered from the of repeated grazing damage by reindeer. regional point of view, not just locally, is the very A certain degree of caution is called for when heavy decimation of the re indeer stock which assessing the effects of reindeer on the vegetation was deliberately carried out during the period cover, since they are much more extensive gra­ 1912-1916. So many of the reindeer in the area zers than are domesticated livestock. The rein- had reverted to the wild state at that time that

Acta phytogeogr. suec. 65 Change and stability of birch tree-limit in the Scandes 21 large scale slaughter was the only remedy, some heavier in certain parts of the area than the bear­ 12 000 animals or more were then shot. The rein­ ing capacity of the grazings, and this therefore deer stock only recovered to its former strength resulted in a marked reduction in the area of at the end of the 1920' s (Lappfogdens i Jamtlands lichen-dominated (Cetraria spp., Cladonia spp.) lan, arsberattelse 1916; Burman 1970). By all ac­ vegetational types (Lappfogdens i Jamtlands lan, counts, the number of reindeer in the area just arsberattelse 1899, 1900). prior to the enforced slaughter, as well as just Thus, everything points to the fact that the prior to the turn of the present century, was grea­ appreciable reduction in grazing intensity which ter than at any other time during the rest of the took place during the period 1915-1925, had a present century (SOU 1966) . The grazing pres­ potentially positive effect on the regeneration of sure was then (i.e. 1900-1912) quite certainly birch from seed within the tree-limit ecotone .

Acta phytogeogr. suec. 65 Insect attack

An important factor in the population dynamics attacks took place in the southern part of the of the mountain birch forest is attack by a variety investigated area in the summers of 1882-84, of leaf-eating insect larvae, in particular the ca­ 1888-92 and 1915-1922 (cf. also Kullman 1976a). terpillars of the geometrid moths ( Oporinia au­ Smith (1920), who carried out fieldwork in that tumnala and Operophthera spp.). High densities same area during the period 1908-1919, did not can have such a devastating effect on the birch mention such insect attacks. There are therefore foliage that no recovery is possible within the good grounds for assuming that such devastating short vegetation period and can lead to wide­ attacks were relatively localised and probably spread destruction of the subalpine and subarctic merely resulted in a temporary defoliation of the birch forest, even to the extent of causing a local birches. The attacks can scarcely have been on lowering of the altitudinal forest- and tree-limits such a scale that they led to a more or less general (e.g. Holmgren 1912; Nuorteva 1963 , Tenow lowering of the tree-limit over the whole of the 1972; Kallio & Lehtonen 1973, 1975). investigated area. According to Tenow (op.cit) serious caterpillar

Acta phytogeogr. suec. 65 Investigation methods

Determination of altitude the observer always stood at the same level as the base of the actual tree for which the altitude was The altitude of the tree-limit above sea level has being estimated. The values obtained in this way been measured at each locality with a Paulin ane­ are considered to be accurate to the nearest 10 m roid altimeter, which could be read with an accu­ (cf. Jim Lundqvist 1968; Rindert op.cit.). Most of racy of ± 1 m. The cited values have been the localities were visited on more than one occa­ rounded off to the nearest 5 m interval. The ane­ sion and differences in the altitudes obtained roid barometer was checked and overhauled an­ hardly ever exceeded 10 m. On the rare occasions nually by the makers. when such was the case the finalcit ed value is the The instrument was adjusted on the following arithmetic mean of all the readings made at that standard basis: locality. 1. for a latitude of 45°N In certain cases determinations of altitude have 2. for the density of air at a temperature of + 10°C been taken from the figures shown on the rele­ 3. for a water vapour pressure equivalent to 1 % vant ordnance maps. These values were always of the barometer reading revised whenever the respective sheets of the 4. the zero point on the scale was set to corres­ modern Topographic map for Sweden were pub­ pond to an air pressure of 762 mm of mercury. lished in the meantime. For those parts of the investigated area for which no topographic map Corrections for changes in air temperature and was yet available in print, copies of the provisio­ pressure during the course of the day, using a nal base-maps for the forthcoming topographic barograph and whirling-thermometer, were not map sheets were obtained from the Swedish carried out (cf. Kilander 1955). Instead, subse­ Ordnance Survey (Statens Lantmateriverk). quent corrections were made possible by carrying out frequently-repeated re-calibrations of the al­ timeter in relation to the close network of levelled heights shown on the official topographical maps (scale 1:50 000) . Such checks were made at inter­ Age-determination of trees vals which seldom exceeded one hour in length. Minor discrepancies which may occasionally The absolute age of individual birch trees growing have occurred, of the order of 20--30 m, were in the upland regions is sometimes difficult to corrected by interpolation, on the assumption determine, because of the customary multi­ that any change in barometric pressure which stemmed form of the birch and a great ability to was noted to have occurred during the interval reproduce vegetatively. between two consecutive checks, had taken place The age-determination results referred to in the gradually. To aid such a procedure the time of present work have all been made at a fixed dis­ day was always noted when observations were tance along each stem, measured from the stem made. Whenever consecutive readings lay an ap­ base where it joins the rootstock, by taking core preciable distance apart vertically, the altimeter samples with an increrrientbor er. was always allowed to stabilise for 1 0--15 min. During the initial stages of the investigation, a before the second reading was made (cf. Rindert number (22 in all) of sawn cross-sections (discs) 1975). of the stems of birches growing at the tree-limit in When making readings the altimeter was held different parts of the investigated area were col­ by the observer at breast-height, taking care that lected and examined. In just one case a few of the

Acta phytogeogr. suec. 65 24 Le ifKullm an annual rings were found to be discontinuous, i.e. magnification of 15-25 x, and kept permanently had bore cores along different radii been taken moistened, the boundaries between the individual from this stem for age determination the results rings were very distinct on the flat surface so would have also differed by a few years . The produced. partial disappearance of certain rings all proved The results of the age determinations of the to be on the side of the stem facing the downhill birch stems investigated have all been expressed slope and at the crooked base of the stem, which in relation to 1975 as the starting point (also in the was asymmetric in cross-section due to recovery legends to the figures). from prostration when young. To eliminate this source of error as far as possible the bore cores were always taken parallel to the hillslope. Obviously, a core bored at a fixed point along a Use of previous data for the stem only yields a minimum estimate of the altitude of the tree-limit length of that stem at the particular point in time given by the age determination. Any conclusions about change or stability of the So far as is known, there are no reports for tree-limit are necessarily based to a large extent birch of more than one annual ring being formed �m comparisons of the present-day altitudes and per year (cf. Sterner 1911). Hustich (1949) found tqose which are reported in literature , as far back that double rings presented no problem in his in time as possible, for the particular localities dendrochronological work on Scots pine growing concerned. An assessment of the reliability of at the arctic tree-limit in N Finland. such accounts is therefore of the greatest impor­ Elkington & Jones (1974) do not exclude the tance, as well as of their terminology. possibility of 'frost-rings' and 'disappearing The majority of the older data on tree-limit rings' being formed in birches growing in Green­ altitude are taken from Harry Smith's monograph land. Beschel & Webb (1963) reported that in (1920, p. 102 ff) , in which he mainly reports unfavourable summers no annual rings were observations made in 1915 and 1916. Unfortu­ formed in the wood of Salix spp. growing in the nately, nowhere in the text does Smith make Arctic. However, so far as birch growing at the quite clear just what he meant by the term 'tree­ tree-limit is concerned, by taking repeated bore limit' (Sw. 'tradgrans'). The only unequivocal cores from five particular stems during the period statement made is that the altitudes given refer to from winter 1976/77 to winter 1977/78, I found the altitudes above sea level at which the upper­ that even during the exceptionally cold summer most tree-sized birches were found growing along of 1977 a normal and perfectly distinct annual ring a 2-5 km stretch of hillslope (op.cit. , p. 97). Just was laid down. According to Schove (1954), miss­ what he meant by 'tree' is not described in abso­ ing rings are mainly a problem when dating very lute terms either. From an examination of his old stems, which is not the case in this investiga­ photographs, however, it would seem that at tion. times multi-stemmed birches, 2-2.5 m in height, Each bore core was secured by binding it with were regarded as being trees (cf. op.cit., pp. 94, refrigerator-tape. It was brought back to the labo­ 116, 118). As a confirmation of this point of view ratory, where I personally did the annual-ring is the mention ( op. cit. , p. 93) that the multi­ counts from a week to at most a month later. stemmed birches, at most of man's-height, Attempts were made, using various stains, to shown on the photographs published by Frodin achieve a greater degree of contrast between (1916, Fig. 7 and Plate Ill), and classified by him summer-wood and autumn-wood, but none gave as 'bushes', according to Smith belonged within any better result than the use of water alone (cf. the 'birch region', i.e. were regarded by him as Eidem 1954). Before counting the bore cores 'trees'. All the indications, therefore, are that were soaked in water for 5-10 min, after which Smith placed his 'tree-limit' at the level of the the surface along which the annual rings were uppermost birches with stems at least 2 m in most clearly visible was finely pared with a scal­ height. In all probability even individual multi­ pel. When viewed under a stereomicroscope, at a stemmed birches, which on morphological

Acta phytogeogr. suec. 65 Change and stability of birch tree-limit in the Scandes 25 grounds ought to be considered as 'bushes' (sen­ lues obtained at neighbouring localities were su Lindman 1914), were reckoned as 'trees' by made. Despite a considerable amount of effort I Smith. have unfortunately been unable to locate Smith's In actual fact the exact minimum height used original field notebooks containing the original by Smith in his 'tree' concept is not so very basic data for his height determinations. important, since at ea 70 % of the localities de­ Accurate determination of altitude by Smith's scribed in the present investigation the upper­ method presupposes the existence of a large most birches with a minimum height of 2 m had number of accurate spot heights in the vicinity of stems of 2-2.5 m in height or more. At only ea the tree-limit localities visited, i.e. reliable and 20 % of the localities these birches were exactly 2 detailed maps are essential. Smith (op.cit.) does m in height and the vertical distances between not make clear just which maps he used, merely such birches and those of a minimum height of 2.5 mentioning the existence of the then newly­ m growing on the same slopes were on average published, ordnance maps (Sw. 'Generalstabs­ only ea 15 m (cf. Kilander 1955, p. 53). At some blad') at scales of 1:200 000 to 1:50 000. Almost of the dry, nutrient-poor, localities in Harjedalen certainly he used sheets 65 Duved and 71 Lj usne­ and Dalarna, the distances apart of these height dal, on the first-mentioned scale, which were is­ categories were greater. Under similar conditions sued in 1904 and 1909 respectively. He was also in N Finland, Armio (1963), for an altitudinal probably able to avail himself of the provisional difference of 100 m, fo und a 37 cm decrease in prints for the larger-scale versions of these maps, mean stem height. issued for the 1:50 000 and 1:100 000 scale sheets Smith's altitudinal determinations were made respectively (Dr. Sven Kilander, pers . comm.). with two aneroid barometers (mean value used) The map situation for the southernmost part of and a whirling thermometer (op.cit., p. 91). A the area investigated by Smith was much less barograph was obviously not used for making satisfactory at that time . Only a tourist map corrections to the barometers for any changes in existed, with a fe w almost certainly inaccurate atmospheric pressure during the field-work. spot heights on it (Smith, op.cit., p. 90). The When making his observations Smith obtained overlapping part of a Norwegian map of the adja­ a value fo r the difference in air pressure (in mm of cent region provided a few fixed points to work mercury) and temperature between a known from. In 1919, however, the Swedish ordnance starting-point and the particular locality, where­ map sheet 76 Tannas (probably a provisional edi­ after these values were converted to m a. s. I. tion) was issued and Smith was able to check the using Professor P. G. Rosen's conversion table reliability of his altitudinal estimates. He states (Svenska Turistforeningens Arsskrift 1893, ·pp. (op.cit. pp . 90--91) that there was complete 184-185), which is based on an equation worked agreement between his barometric heights for out by W. Jordan and E. Hammer (see Jordan various topographic features and the correspond­ 1917). In principle this is the same formula as that ing values shown on the map. on which the modern Paulin aneroid-barometer Since Harry Smith followed the forest-limit scale is based (information supplied by Microma­ during his wanderings (op.cit., pp. 1 and 91), he tic International Co Ltd.). Jordan (op.cit.) states would probably have used the topographic fea­ that the equation holds fo r altitudes up to 1000 m tures in its vicinity, for which spot-heights were a. s. I. Smith's highest altitudinal determination available, when making his calibrations. A com­ was 1007 m. No grounds therefore exist for think­ parison of the altitudes given for Smith's prob­ ing that there is any systematic difference be­ able calibration points on the old ordnance maps tween my values and Smith's in this respect. and the modern topographic maps shows very The mathematical calculations which were little difference in most cases. Only exceptionally bound up with Smith's final values do allow a is there more than 10 m difference in height and in certain possibility for the occurrence of minor these few cases, where it is obvious that Smith's mistakes. Major miscalculations, however, are values have been derived from the use of inaccu­ unlikely, since any such gross deviations would rate spot heights, the altitudes have been correct­ have been noted when comparisons with the va- ed before being cited in the present investigation.

Acta phytogeogr. suec. 65 26 Le ifKullman

In certain cases, great difficulty arose in identi­ Smith in the southern part of his investigated fying Smith's localities by name. Because of area, mentioned above, nevertheless indicate that these difficulties, quite a large proportion of the margin of error as a whole is amazingly low; a Smith's 391 localities for which tree-limit altitu­ value of ± 10 m seems a reasonable estimate. des are given have had to be rejected. Neverthe­ In certain cases observations made prior to less, because Smith lists his localities in a more or those of Smith have been used (Hisinger 1819, less chronological order, and the fact that at least 1820; Hprbye 1861; Henning 1887; Sernander a proportion of them were recognisable, has 1898; Birger 1908 ; Samuelsson 1917). All these meant that the sites of others could be re-identi­ investigators determined altitude with a baro­ fied with a great degree of certainty and used for meter. Even fewer maps were available to them, comparison in the present investigation. Site however, than were available to Smith. Further­ identification was further facilitated by Smith's more the exact nature of what they measured the statement (op.cit., p. 97) that each height deter­ altitude of is hardly made clear. In most cases the mination referred to the uppermost tree-sized values probably refer to the limit of some kind of birches present along that particular 2-5 km birch stand, i.e. they thus provide no more than a stretch of terrain. minimum altitude for the birch tree-limit at that Identification difficulties due to Smith's use particular time. sometimes of older local names for certain locali­ At certain localities the altitudinal limits for ties have been obviated thanks to the welcome birch about 1950 were determined by Dr. Sven help of Dr. Sven Kilander, who has both worked Kilander (1955). At these localities therefore, it is in that area himself and knew Harry Smith perso­ possible to elucidate the exact degree of tree-limit nally. change after 1950. The uncertainties in Kilander's In principle all the identifiable localities from values are almost certainly less than those at­ Smith's investigation were re-visited. These are tached to Smith's calculations, because of the representative for most of the habitat types pre­ greatly improved maps issued in the meantime sent in the tree-limit ecotone within the studied and the refined instruments. region. In a few cases it is obvious that Smith some­ how or other did not discover the highest-growing Age-determination transects birch-trees at a particular locality. The probable explanation is that he kept along the forest-limit, As a complement to the data on the former extent more or less parallel with the general contours, of the tree-limit derived from a study of the litera­ the whole time (cf. above). In such broken and ture, age-determination transects were invest­ rather undulating terrain, where the vertical dis­ igated at ea 75 % of the 213 localities studied. For tance apart of the forest-limit and the tree-limit is i 7 % of the studied localities such age-determina­ often quite appreciable, it is highly probable that tion transects provide the only evidence on which the highest-growing trees have escaped his notice to draw conclusions about altitudinal shifts of the (e.g. localities 52 and 56). tree-limit. Harry Smith was renowned as being a very The aim of the age-determination transects has careful 'fieldworke r' (Dr. Sven Kilander, pers. been to assess the 'probability' that at any parti­ comm.). It is therefore highly improbable that he cular locality at least one birch of tree-height was ever knowingly tried to spare any effo rt in his growing at that particular altitude in 1915/16. attempts to find the highest-growing birches. In principle the method adopted was that the The main element of uncertainty attached to ages of small numbers (seldom more than 5) of Smith's tree-limit altitude de terminations is prob­ subjectively selected birch stems were determin­ ably the difficulty of eliminating the effect of sud­ ed at different altitudes along a vertical transect, den changes in atmospheric pressure on the read­ from the present-day tree-limit down to the level ings he made, because of the great scarcity, on at which birches of tree-height were known for the maps available at that time, of spot heights for certain to have been growing at the investigated cross-checking. The good results obtained by locality about 1915. This latter level was arrived

Acta phytogeogr. suec. 65 Change and stability of birch tree-limit in the Scandes 27 at from data in literature and/or from visual as­ altering direction so as to include the oldest-look­ sessment of the ages of the present-day trees, ing stems at any particular altitude. Because of based on stem diameter, height, appearance of the irregular distribution of the available trees, the bark and the degree of coverage by epiphytic particularly in the upper parts of the transects, lichens. Age determinations of the selected stems the resulting transects have been more a zig-zag were then made from wood cores obtained with than a straight line, i.e. it proved impossible to an increment borer. As the number of such age maintain a fixed vertical interval for the age de­ determinations increased, there was a corres­ terminations made within any particular transect. ponding improvement in the author's capability of In general the cores for age determination were making a visual assessment of the age of particu­ taken at a height of 10-20 cm above ground-level. lar stems, based on the criteria mentioned above, For practical reasons bore cores could not be whereby the oldest stems in a particular birch taken at ground-level, although ideally this would stand at any particular altitude could in all proba­ naturally have been desirable. Where obviously bility be localised and their actual ages could then old stems (> 60 years) were encountered, the be exactly determined from bore cores. bore cores were taken at a height of 2 m above the Since most localities were visited more than base of the trunk. The age of only one stem per once, supplementary age determinations could be individual rootstock was determined. Old tree made in those cases in which the data obtained stumps and fallen trunks of former, well-grown, from the literature about the altitude of the tree­ tree birches, which were obviously more than 2 m limit in 1915/ 16 conflicted with the initial results in height when alive, were always carefully given by the age-determination transect made at searched for in the transects. the same locality. The approximate height of all the living stems At certain of the investigated localities no age investigated was estimated visually. The degree determinations could be made, or were impos­ of uncertainty attached to such height determina­ sible at certain altitudes along the transects, due tions is likely to amount to only 10-20 cm for to a variety of reasons such as breakage of the stems 2 to 4 m in height, and to a maximum of 0.5 increment borer or loss of cores, nature conserv­ to 1 m for longer stems. ation considerations, or because precise annual­ Immediately after the investigation of the lower ring counts were impossible on some cores due to limit of any particular transect and the determina­ aberr�nt wood anatomy etc. In a few cases no tion of its altitude with the altimeter, I returned confirmatory age determinations were considered uphill to the starting point of that transect and necessary, because the good agreement found be­ checked the initial altitude determination. If there tween the visual assessment and the literature was any difference between the two values, due data was considered to yield a true picture of to changes in the barometric air pressure in the events. meantime the altitudinal values determined at all The lateral extents of the age-determination the intervening points in the transect were cor­ transects were not predetermined. In dense forest rected accordingly. The vertical distances apart stands widths were generally less than 50 m, of the different levels within each transect ought whereas above the forest-limit, where the trees therefore to be pretty reliable. grow fairly far apart, a transect width of more than 50 m was necessary . At particular altitudes along a transect where the ages of several stems were determined, the Photographic record altitude value cited in the text really represents an approximation of ± 5 m, due to the slope of the All the photographs were taken by the author, ground at that point. using a twin-lens reflex camera, a Yashica Mat­ The practice adopted in the field was to start at -125 G (negative size 6x6 cm) with a 80 mm the present-day tree-limit and work downwards, objective, 1 :2.8.

Acta phytogeogr. suec. 65 Basic data from the investigated localities

Explanatory remarks, terminology and disjunct, formed of scattered, but dense, clumps abbreviations of birch trees. In the latter case a minimum of three such clumps, each covering an area of at The basic data yielded by the field investigations least 5x5 m and comprising a minimum of 10 are set out separately for each locality in turn, tree-sized stems, has been required before that under five headings. particular altitudinal niveau was considered to lie The localities have been consecutively num­ below the forest-limit. Where the forest-limit was bered from N to S within the investigated area. irregular, with wedge-shaped lobes or tongues Each has been named in accordance with the thrusting out upslope, the forest-limit has been usage given on the topographical map sheets (see taken as being the highest-lying tips of such fea­ Maps). Site aspect is shown by capital letters tures. immediately after the site name. The position of The character of the forest-limit is in each case the present-day tree-limit (TL) is indicated for indicated after the respective altitudinal value. each locality by citing the respective coordinates The forest-limit data are cited for future com­ from the Swedish National Grid, with an accura­ parative purposes only. MSL-mature stem li­ cy of ± 100 m. mit: represents the altitudinal limit for still-living, Each of the named localities represents a verti-· or now dead, erect or fallen birch stems which cal transect, running at right-angles to the local were at least 2 m in height and alive in 1915/16. slope contours and with a breath of ea 50 m. This limit provides the minimum altitude for the Abbreviations adopted are also used in the rest position of the tree-limit at that time and forms an of all subsequent sections of the present paper. important complement to the tree-limit data ob­ The fivemain data headings and the respective tained in literature . abbreviations used are dealt with below, in the The position of the MSL has in the majority of order in which they occur in the descriptions. cases been determined from the results of the age-determinations, generally from the annual­ ring counts made on the bore cores, though in Present-day altitudinal limits certain cases based solely on visual estimates. The present-day altitudes for four differently-de­ Where the remains offal len trunks or stumps of finedbirch limits are given for each locality. The former well-grown trees, which seemed to have heading is followed by the date (year) for which been at least 2 m in height in 1915/16, were en­ the data are valid. countered, these have also been taken into ac­ Where no indication is given for any one of the count in determining the altitude of the M�L. four limits this implies that that particular limit TL-present-day tree-limit: represents the alti­ was not recognisable at that particular locality . tude, at any particular locality, at which the up­ Each of the four limits is referred to by its permost birch, with stem(s) at least 2 m in length, capital letter abbreviation given below, and each grows at the present-day; i.e. each value refers to is followed by the altitude, in metres above sea­ a particular point in the terrain and has no genera­ level, determined in the field. FL-forest limit: lised horisontal implication (cf. Kullman 1976a). represents the highest point at a locality at which The sole criterion for calling such a birch stem a birches of tree-height (see below) form a more or 'tree' has been that good grounds existed (e.g. the less closed stand. The limit may be sharp and snow-depth indicating lichen-limit (Sw. 'oliva­ distinct, running as a line across the landscape, or cea-grans') or direct observations during the win-

Acta phytogeogr. suec. 65 Change and stability of birch tree-limit in the Scandes 29 ter) for thinking that this stem is not completely values form the basis for the calculation of the snow-covered at any time during the winter. degree of tree-limit displacement at each locality. SL-species limit: represents the highest alti­ In certain cases the MSL results from the age­ tude at a particular locality at which birch, irre­ determination transect and the data obtained spective of stem diameter or height, was found from the literature survey yielded different values growing at the present-day. for the tree-limit in 1915/16. To minimise any bias in the resulting calculations of the tree-limit dis­ placement at such localities the higher of the two Age-determination transect values obtained has been chosen for comparison For most localities the data given under this head­ with the present-day tree-limit value (TL). ing are the results obtained from the age determi­ All values cited for former positions of the nations made at different levels within the tran­ tree-limit, however, have been rounded off to the sect made at that locality (for details se Investi­ nearest 5 m. gation methods). In all subsequent parts of the present paper the The data obtained at each investigated level are past tree-limit is simply referred to as the PTL. set out in the form of an alpha-numerical code, as follows: a = the altitude of the investigated tran­ Degree of change sect level, in m a. s. 1.; b = the age(s) of the stem(s) investigated; c = the mean length(s), in The altitudinal extent of any displacements in the metres of the stem(s) investigated; d = the height tree-limit between 1915/16 and the present-day above groundlevel, in decimetres, at which the are described below, as follows. bore core(s) for the age determination(s) was ta­ Apparent displacement, viz. the difference be­ ken. tween the values of the TL and the PTL is given E.g. with values in m. a b c d As already pointed out (see pp. 24 ff) some 915--39, 37, 3 1--3 .0--2 degree of uncertainty is especially attached to the older determinations of the altitudinal position of the tree-limit. In adverse cases, for example, one Documentation may imagine that one of Smith's determinations This section contains a summary, for that particu­ was 10 m too low and that my own determination lar locality, of the data available in literature for was 5 m too high, i.e. the calculated tree-limit the altitudinal limits for birch, primarily for the displacement would be exaggerated by 15 m. So tree-limit, at earlier periods. This summary forms as to obviate, as far as possible, any such spat­ the basis for a comparison with the present-day ious augmentation, all the values for 'Apparent limit. displacement' have been deliberately reduced if The majority of the comparisons are with the derived from comparison of the present-day alti­ data given by Smith (1920, pp. 102- 1 07) from his tude of the tree-limit (TL) with its former position field surveys made in 1915/ 16. These data are as adduced from literary evidence alone (literary cited in an abbreviated form as follows: TL-Smith values higher than the MSL values), or in cases in (a):b, where 'a' is the number given by Smith to which the latter values are the same as the MSL that particular locality, and 'b' is the altitude in values. If, on the other hand, the PTL is based m a. s. l. solely upon the MSL data (MSL values higher than literary values), then no correction has been made to the 'Apparent displacement' values, be­ Past tree-limit (PTL) cause of the fact that the vertical distances apart This is the tree-limit altitude for the respective of the different levels in each age-determination locality, derived either from literature or fr om the transect are reliable (see pp. 26 f). age-determination transect results, for the point In general, the greatest magnitude of the cor­ in time (1915/16) chosen for comparison with the rection factor used has been -15 m. For all locali­ present-day (TL) value found there; i.e. the PTL ties which are situated in the vicinity ( < 1 km

Acta phytogeogr. suec. 65 30 LeifKullm an away from) of topographical features for which tions of this paper are the minimum values found reliable spot heights were available in 1915I 16 and and that the actual changes may well in certain which lay at about the same altitude as the MSL cases have been greater. estimation points, the use of a smaller correction The use of the term 'significant' should never­ factor has been considered justified(e ither 10 or 5 theless not be taken too literally, since at best it m was subtracted). only represents a probability that a change has The corrected value for the 'Apparent dis­ occurred, i.e. that probability is directly propor­ placement' so obtained has been termed the 'Sig­ tional to the calculated value of the displacement. nificant displacement' . The use of this value, rath­ The terms 'displacement, shift, change etc.' er than the uncorrected ones, in the mathemati­ used later on in this paper, all refer to values of cal treatment of the data, ensures that any tree­ 'Significant displacement'. limit changes discussed in the subsequent sec-

Acta phytogeogr. suec. 65 Investigated localities

1 Tj uvbodklumpen S (70 364 13 178) the tree-limit. The lattermay reasonably well have lain higher than the forest-limit, although scarcely at the Present-day altitudinal limits ( 1976) same altitude as it does today , since from Smith's FL: 810, lobes locality 4 the uppermost trees can clearly be seen sil­ MSL: 780, a fairly high number of stems houetted against the skyline , a point which is scarcely TL: 820, a 2.2 m high stem likely to have escaped his notice. SL: 825 , a creeping, ea 1 m high stem Past tree-Limit Degree of change Age-determination transect 780 Apparent displacement: +40 820-31-2. 2- 1 Significantdispla cement: +40 810 - 52, 44 , 42, 35, 27 - 3.5 - 2 800 - 29 - 7.0 - 20 2 Hastryggarna S (70 339 13 174) 790 - 57 , 47, 35, 34, 2 9-5.0 -2 780 - 70 - 4.0 - 20 Present-day altitudinal limits (1976) 775 - 71 - 8.0 - 20 MSL: 740, one stem TL: 785, a ea 2 m high stem Documentation That Smith observed this hillslope at a distance, e.g. Age-determination transect from his locality 4, is an unavoidable conclusion. The No investigation made presence of the lake Skurdalssjon at the foot of this Documentation hillslope enabled the approximate altitude of the fo­ TL-Smith (5):746. The summit of this hill is shown as rest-limit to be established with a fair degree of certain­ 14 m lower in altitude on Smith's map than on the ty. Probably the figure so obtained did not deviate modern topographical map. Smith's tree-limit has appreciably from that of the vicinity in which he was therefore been corrected by + 14 m. (ea 750 m), so that he considered it was hardly worth the effort involved to make a separate determination of Past tree-limit Degree of change 745 Apparent displacement: +40 Significant displacement: + 35

3 Larsvalen NV (70 323 13 159) Present-day altitudinal limits ( 1976) FL: 730, diffuse boundary MSL: 705 , one stem TL: 740, a ea 2 m high stem Age-determination transect 705 - 78 - 4.0 - 20 Documentation TL-Smith (3):723 . The altitude of the nearby lake Skurdalssjon is shown as 13 m lower on Smith's map than on the modern topographical map, Smith's tree­ limit has therefore been corrected by + 13 m. Bosaeus (1929) published a photo of the so-called Printzskold Monument (Fig. 12) which stands on this hillslope at an altitude of 710 m a. s. I. It is quite clear from the photo that the immediate vicinity of the me­ morial stone, just prior to 1929, was treeless. Today it Fig . 11. The tree-limit (820 m a.s.l.) at locality 1. The is surrounded by a dense stand of 2-3 m high young birch tree is growing in a shallow depression from birches (Fig. 13). which the snow has just melted. An age-determination on a bore core from the base of the longest stem gave Past tree-limit Degree of change 31 years. Because of the exceptionally snowy winter 725 Apparent displacement: + 15 1975/76 the tree is still leafless . Photo: July 4, 1976. Significantdis placement: + 10

Acta phytogeogr. suec. 65 32 LeifKullm an

Fig. 12. The Printzskold Monument at locality 3, as Fig. 13. The same view as in Fig. 12. The monument is seen on a photograph published by Bosaeus (1929). today surrounded by dense clumps of trees, vigorous­ Low birch shrubs exist in the vicinity, but definitelyno ly-growing and 2 to 3 m high. The establishment of tree-sized birches. tree-stands has obviously increased local snow reten­ tion. Photo: March. 1, 1977.

4 Skurdalsbergen N (70 323 13 141) 5 Skurdalshojden N (70 308 13 143) Present-day altitudinal limits Present-day altitudinal limits (1974) FL: 720, clumps of trees MSL: 740, one stem MSL: 705, one stem TL: 795, several individual trees bearing 2-2.5 m TL: 775, a ea 2.5 m high stem high stems SL: 835-805, a few 1.5-1 .8 m high shrubs; some Age-determination transect were at least 2 m high at the beginning 705 - 62 - 4.5 - 20 of the 1970's Age-determination transect Documentation 740 - 71 - 3.0 - 20 TL-Smith (12):682. For a similar reason as above, Smith's value has been corrected by + 13 m. According Documentation to the estimates of altitude made by Hisinger (18 19) in Smith estimated the tree-limit on all sides of the Skur­ this areas, using an aneroid barometer, Skurdalssjon dalshojden, except on the N-facing slope. The lack of lay at 1916 Parisian feet, i.e. ea 622 m a. s. 1., which is 73 any value for this point of the compass is probably best m lower than the correct value. All his altitude estima­ interpreted as indicating the absence of trees, above tions were made in the course of one single day, within the valley floor, at 73�740 m of this side on the hill. a few hours of time; consequently, the above-mention­ Past tree-limit Degree of change ed error is assumed to be applicable to all. When Hi­ 740 Apparent displacement: +55 singer's other results are converted to metres and cor­ Significant displacement: +55 rected by adding 73 m, the following values are obtained: "limit of birch bushes"-ca 785 m, "limit of 6 Skurdalshojden E (70 306 13 153) tree growth"-lower than 720 m, although no indica­ tion is given of the meanings of the terms "bush"' and Present-day altitudinal limits ( 1972) "tree". FL: 725, clumps of trees At an altitude of715 m on the hillslope under discus­ MSL: 725, one stem sion, there is the old standing-stone "Stenen i gronan TL: 765 , a 2.1 m high stem; only 5 m below there dal", which is thought to have marked the old route are some 3.5 m high stems between Sweden and Norway (Festin 1934). In 1934 Age-determination transect the stone was moved slightly, during its restoration, 725 - 62 - 3.0 - 20 and thereafter photographed together with its environs. Documentation At that time there was a birch thicket (maximum height TL-Smith (6):724. Smith calls this locality "Storlien". 1 m) behind the stone. Today the same spot is occupied The hill now called Skurdalshojden, was in the past by a dense stand of 2-3.5 m high birches. known as Storlifjalletor Storlien (Flemstrom 1972). Past tree-limit Degree of change Past tree-limit Degree of change 705 Apparent displacement: + 70 725 Apparent displacement: +40 Significant displacement: +65 Significant displacement: + 35

Acta phytogeogr. suec. 65 Change and stability of birch tree-limit in the Scandes 33

7 Skurdalshojden S (70 304 13 143) 10 Rekdalshojden N (70 262 13 115) Present-day altitudinal limits ( 1975) Present-day altitudinal limits (1974) FL: 770, tongues and clumps of trees, with a FL: 700, even limit marked admixture of the hybrid Betula nana MSL: 755, a small number of stems x pubescens. TL: 820, a few clumps of 2.5-3 m high stems, some MSL: 738, a small number of stems of which had died quite recently TL: 815, several 2 m high stems which project SL: 840, a 1.8 m high stem above a dense and extensive metre high Age-determination transect thicket of bushy birch 820 -46, 37, 35, 30, 28 - 2.7 -2 SL: 840, a few 0.4 m high shrubs 775 - 54, 52, 49 , 42, 41 - 3.0 - 2 Age-determination transect 755 - 64 - 4.0 - 20 825 - 13 - 1.3 - 1 755 -93, 57, 37, 35, 31 - 3.5-2 815 - 45, 43 , 33, 32 - 2.0 - 2 720 - 71, 63 - 4.0 - 20 800 - 30 - 2.5 - 2 Documentation 785 - 39 - 3.2 - 2 TL-Smith (56):820. Although this mountain was un­ 785 - 22 - 3.2 - 20 named on Smith's map it was quite natural that he 730 - 60 - 5.5 - 20 should refer to it in the text as "Rundvalen", since it 720 - 77 - 5.5 - 20 represents a spur from this mountain towards the NW. Documentation The summit altitude shown on Smith's map is 6 m TL-Smith (7):730 higher than that given on the modern topographical map . In consequence Smith's value has been reduced Past tree-limit Degree of change accordingly. 730 Apparent displacement: +85 Significant displacement: +80 Past tree-limit Degree of change 820 Apparent displacement: 0 Significant displacement: 0

8 SW (72 304 13 137) Skurdalshoj den 11 Rekdalshojden W (70 253 13 112) Present-day altitudinal limits (1972) Present-day altitudinal limits (1974) FL: 780, tongues and lobes FL: 830, wedge 740 , MSL: one stem MSL: 815, a small number of stems TL: 795, a ea 3 m high stem TL: 835, a small number of 2.5 m high stems of 820, SL: a few metre high shrubs low vitality Age-determination transect 740 - 71 - 3.5 - 20 Documentation TL-Smith (9):739 Past tree-limit Degree of change 740 Apparent displacement: +55 Significant displacement: +50

9 Skurdalshojden W (72 307 13 136) Present-day altitudinal limits ( 1972) FL: 765 , even limit MSL: 740, one stem TL: 785, a 2 m high stem SL: 790, a few 10-20 cm high shrubs Age-determination transect 740 - 74 - 4.0 - 20 Documentation Fig. 14. The tree-limit (835 m a.s.l.) at locality 11. All TL-Smith (10):745 the birch stems are obviously quite young and have Past tree-limit Degree of change been severely deformed by the weight of the snow 745 Apparent displacement: +40 cover. Vaccinium myrtillus and Nardus stricta are the Significant displacement: + 35 fieldlayer dominants. Photo: June 12, 1974.

Acta phytogeogr. suec. 65 34 Le ifKullman

Age-determination transect Past tree-limit Degree of change 835 - 56, 47, 47, 44, 31 -2.0 -2 803 Apparent displacement: 0 820 - 80, 74 , 65, 54, 39 - 3.0 - 2 Significantdispla cement: 0 815 - 63 - 3.5 - 20 Documentation 15 Rundvalen W (70 207 13 147) TL-Smith (55):810. See locality 10. Mrs Gunborg Ant­ Present-day altitudinal limits holm and Mr Sten Olofsson, both of Storvallen, state FL: 770, even limit that the birch limit is higher today than when they were MSL: 785, a small number of stems young (about 50 years ago). TL: 785 , several 3-4 m high clumps of trees Past tree-limit Degree of change Age-determinaton transect 815 Apparent displacement: + 20 785 - 71' 62 - 4.5 - 20 Significantdispla cement: + 20 785 - 88 - 4.5 - 2 Documentation 12 Rundvalen N (70 208 13 151) TL-Smith (27):792 Present-day altitudinal limits (1973) Past tree-limit Degree of change FL: 755, tongues and clumps of trees 792 Apparent displacement: -5 MSL: 785, one stem, very old, but impossible to date Significant displ�cement: 0 more accurately because of fungal attack TL: 795 , a single tree bearing five 3 m high stems 16 BHihammarkhippen WNW (70 139 13 161) Age-determination transect Present-day altitudinal limits No investigation made FL: 870, clumps of trees Documentation MSL: 855, one stem TL-Smith (25):786 TL: 915, a sparse clump of 2.5-3 m high stems

Past tree-limit Degree of change Age-determination transect 785 Apparent displacement: + I 0 915 - 37' 36, 26 - 2.7 - 2 Significant displacement: + 5 855 - 64 - 3.0 - 20 835 - 87 - 4.0 - 20 13 Rundvalen E (70 203 13 154) Documentation Present-day altitudinal limits TL-Smith (36):890. Mrs Gunborg Antholm, Storvallen, FL: 755, diffu se limit states that the birch limit is higher today than when she MSL: 785 , a few stems was young. TL: 795, a small number of ea 2 m high stems Past tree-limit Degree of change Age-determination transect 890 Apparent displacement: + 25 785 - 91 - 4.5 - 20 Significant displacement: + 10 Documentation TL-Smith (26):784. Mrs Gunborg Antholm, Storvallen , 17 BUthammarklappen W (70 123 13 122) states that the birch limit is higher today than when she Present-day altitudinal limits ( 1976) was young. FL: 875 , lobes and small clumps of trees Past tree-limit Degree of change MSL: 850, one stem TL: 940, two 2.3 m high stems, much deformed by 785 Apparent displacement: + 10 · Significant displacement: + 5 the weight of snow Age-determination transect 14 Rundvalen S (70 205 13 151) 940 - 26 - 2. 3 - 2 Present-day altitudinal limits 935 - 32 - 3.5 - 2 FL: 790, even limit 930-39-3.5-2 MSL: 800, one stem 920 - 37 - 2.5 - 2 TL: 800, a 2.5 high stem, which pokes out of a 875-55, 45 , 34, 34, 30 - 3.3 - 2 1-1.5 m high scrubby growth 850 - 85 - 5.0 - 20 SL: 805, a few metre high shrubs Documentation Age-determination transect TL-Smith (35):896. Mrs Gunborg Antholm, Storvallen, 800 - 88 - 3.0 - 20 states that the birch limit is higher today than when she was young. Documentation TL-Smith (29):803 . Mrs Gunborg Antholm, Storvallen, Past tree-limit Degree of change states that the birch limit is higher today than when she 895 Apparent displacement: +45 was young. Significant displacement: + 30

Acta phytogeogr. 65 suec. Change and stability of birch tree-limit in the Scandes 35

18 GraslidfjallN (70 162 13 172) Documentation TL-Smith (40):820. See locality 19. Present-day altitudinal limits (1975) FL: 830, even limit Past tree-limit Degree of change MSL: 825, one stem 815 Apparent displacement: 0 TL: 900, a 2.5 m high stem Significantdi splacement: 0 Age-determination transect 900 - 26 - 2.5 - 2 21 Getvalen NW (70 195 13 228) 895 - 35, 35 - 3.5 - 2 Present-day altitudinal limits (1977) 880 - 46 - 3 . 5 - 1 FL: 860, clumps of trees with ea 3 m high stems 870-81,68, 61, 42, 39 - 5.0-2 MSL: 805 , a small number of stems 825 - 61 - 5.0 - 20 TL: 875 , several individual trees with 2-3 m high 810 - 78 - 6.0 - 20 stems Documentation Age-determination transect TL-Smith (37) :862. Mrs Gunborg Antholm, Storvallen, 875 - 31, 30 - 2.8 - 2 states that the birch limit is higher today than when she 870 - 39, 32 - 3.0 - 2 was young. 855 - 52, 42,38, 35 -3.0 - 2 Past tree-limit Degree of change 835 - 35 - 4.5 - 20 860 Apparent displacement: +45 805 - 71 - 6.0 - 20 Significant displacement: + 30 Documentation TL-Smith (41):760. Smith states that this spot faced W, 19 Lillhammaren N (70 179 13 203) which may be explained by the fact that the contours Present-day altitudinal limits (1977) shown on his map run in a more markedly N-S direc­ FL: 800, lobes and small clumps of trees tion than the contours shown on the modern topo­ MSL: 790, a small number of stems graphical map. TL: 830, five 2.5 m high stems borne by Kilander (1955) gives values for the altitudinal limits two individual trees for birch on this hillslope, made in 1951. The results SL: 835, a few 1 - 1.5 m high shrubs were as follows: Age-determination transect 880, a nearly-prostrate shrubby birch 830-57, 51,47, 38 -2.5-2 870, a shrubby birch 810 - 42 - 2.5 - 2 867, a 1.5 m high birch thicket 805 - 61' 41' 38 - 4.0 - 2 860-855, a 2 m high birch thicket 795 - 73 , 56, 42 - 4.5 - 2 840, a thicket, together with a few 3 m high trees 795 - 39 - 5.0 - 20 835, forest 790 -73, 64, 51, 31 - 3.5-20 Past tree-limit Degree of change Documentation 805 Apparent displacement : + 70 TL-Smith (38):838. Smith probably calibrated his alti­ Significant displacement: + 70 meter at pt. 898 or pt. 892 shown on his map. The latter spot height is also shown on the modern topographical 22 Getvalen NNW (70 204 13 236) map, although with an altitude 7 m lower than that shown on Smith's map . There is therefore a strong Present-day altitudinal limits ( 1977) probability that the altitude given by Smith, measured FL: 840, clumps of trees, 3 m high in relation to the calibration point mentioned above, is MSL: 810, one stem somewhat excessive. TL: 850, several 2-3 .5 m high stems Past tree-limit Degree of change Age-determination transect 830 Apparent displacement: 0 850 - 52 - 3,5 - 2 Significant displacement: 0 840-91,45, 38, 25-3.0 - I 810 - 61 - 7.0 - 20 20 Lillhammaren NE (70 182 13 209) Documentation Present-day altitudinal limits ( 1977) TL-Smith (42):736. Mrs Gunborg Antholm, Storvallen, FL: 740, small clumps of trees states that the birch limit is higher today than when she MSL: 730, one stem was young. TL: 815, a small number of 2-2.5 m high stems Dr Sven Kilander has placed his unpublished results for the altitudinal limits of birch, made in 1951, at my Age-determmation transect disposal , viz: 815 - 38, 32, 30 - 2.5 - 2 790 - 69, 42, 35, 27 - 3.0 - 2 880, prostrate stems (Kilander 1955) 730 - 64 - 5.0 - 20 855 , an almost 3 m high tree

Acta phytogeogr. suec. 65 36 Le ifKullman

855, the more or less distinct limit for small clumps of 24 Storsnasen N (70 203 13 259) birch Present-day altitudinal limits ( 1976) Past tree-limit Degree of change FL: 760, wedge 810 Apparent displacement: +40 MSL: 760, a small number of stems Significant displacement: +40 TL: 795 , a 2.3 m high stem Age-determination transect 790 - 47 ' 42, 30 - 2.5 - 2 23 Ingolvskalet N (70 203 13 249) 760 - 69 - 4.0 - 20 Present-day altitudinal limits (1975) Documentation FL: 800 , even limit TL-Smith (44--46): max 779. Mr Sten Olofsson, Storval­ MSL: 815, one stem len, states that the birch limit is higher today than when TL: 845 , a 3 m high stem he was young. Age-determination transect Past tree-limit Degree of change 845 - 32 - 3.0 - 2 780 Apparent displacement: + 15 830 - 24 - 2.5 - 2 Significant displacement: 0 815 - 51, 44, 43 , 38 -4.0 - 2 815 -76-5.0 -20 25 Storsnasen NE (70 197 13 264) 800 - 69 - 6.5 - I 0 800 - 88 - 5.5 - 20 Present-day altitudinal limits FL: 805, even limit Documentation MSL: 760, one stem TL-Smith (43):773. Mrs . Gunborg Antholm and Mr TL: 865, two 2.5 m high stems Sten Olofsson, both of Storvallen, state that the birch SL: 875, a 0.9 m high shrub limit is higher today than when they were young. Age-determination transect Kilander (1955) estimated the upper limit for 'low­ 865 - 31 - 2. 5 - 2 grown forest' to lie at 790 m in 1951, and on the same 855 - 26 - 2.0 - 2 occasion found several ea 2 m high birch thickets grow­ 845 - 25 - 2.2 - 2 ing at 845-840 m. 845 -45, 37, 35, 34, 32 - 1.5-1 Past tree-limit Degree of change 820 - 43 , 38, 34, 33, 28 - 2.3 - 2 815 Apparent displacement: + 30 810 - 42, 40, 39, 37, 37 - 2.5 -2 Significant displacement: + 30 760 - 71 - 5.5 - 20

Fig. 15. Birches growing 10 m below the tree-limit (880 Fig. 16. Birches growing 30 m below the tree-limit (880 m a.s.l.) at locality 26. Around 1940 there were, at m a.s.l.) at locality 26. Stem base age of the oldest one most, only birch shrubs less than I high growing was 39 years. These stems are growing very close to m here. The photo was taken just before the trees burst the local snowline at leafing time and have now at­ into leaf and it is obvious that only a slight increase in tained a length at which they are very liable to be the duration of the snow-period would make their con­ broken by the weight of snow. Photo: June 6, 1974. tinued existence at this locality impossible. Photo: June 6, 1974.

Acta phytogeogr. suec. 65 Change and stability of birch tree-limit in the Scandes 37

Documentation states that the birch limit is higher today than when he TL-Smith (47 or 48):780 or 794 . Mr Sten Olofsson. was young. Storvallen, states that the birch limit is higher today Kilander (1955) found a 0.3 m high shrub at 925 m in than when he was young. 1951. Kilander's (1955) determinations on this hillslope in Past tree-limit Degree of change 1951 gave the following results: 805 Apparent displacement: + 75 855-850, several birch thickets, ea 1 m high. Significant displacement: +60 810, scattered arborescent birches 785 , small, low-growing, clumps of trees 27 Storsnasen SE (70 165 13 277) Past tree-limit Degree of change Present-day altitudinal limits (1974) 795 Apparent displacement: + 70 FL: 800, clumps of trees Significant displacement: +55 MSL: 810, a small number of stems TL: 875, a small group of birches, with ea 2.5 m high stems 26 Storsnasen E (70 171 13 278) Age-determination transect Present-day altitudinal limits (1975) 860 - 4 7' 41 ' 40 - 2. 5 - 2 FL: 800, lobes and small clumps of trees 810-85, 75, 46-3.3-2 MSL: 805 , a small number of stems 810 - 81 - 4.0 - 20 880, 3 TL: a m high stem Documentation Age-determination transect TL-Smith (50):804. Mrs Gunborg Antholm and Mr Sten 880 - 31 - 3 . 0 - 2 Olofsson, both of Storvallen, state that the birch limit 875 - 31 - 2.3 - 2 is higher today than when they were young. 870 - 32 - 2.2 - 2 Kilander's (1955) results for this locality in 1951 860 - 34 - 2.0 - 2 were: 850 - 39, 36, 33, 25 - 3.3 - 2 886, a 2 m high thicket 835 - 76, 74, 56, 35, 35 - 3.5 - 3 870, a 1.3 m high thicket 830 -45, 37, 36, 35, 26 - 3.2 - 2 853, scattered, more or less arborescent, specimens 805 - 103 - 7.0 - 20 848 and 825, small clumps of trees 800 - 150, 78 - 4.0 - 20 Past tree-limit Degree of change Documentation 810 Apparent displacement: +65 TL-Smith (49):806. Mr Sten Olofsson , Storvallen, Significant displacement: +65

Fig. 17. On both sides of this ridge at locality 28 (805 m a.s.l.) birch has colonised wide areas of ground which receive a rela­ tively long-lasting snow cover. On the other hand, on the crest of the ridge, which is dry in summer and retains only a thin snow cover in winter, there has been no birch colonisation since 1915/16. Photo: June 5, 1974.

Acta phytogeogr. suec. 65 38 Le ifKullman

MSL: 790, a small number of stems TL: 905 , a small clump of 2.5 m high stems

Age-determination transect 905 - 45, 38 - 2.5 - 2 850 - 40 - 5.0 - 20 790 - 85 , 75 - 4.0 - 20 Documentation TL-Smith (52):804. Mrs Gunborg Antholm and Mr Sten Olofsson, both of Storvallen, state that the birch limit is higher today than when they were young . Past tree-limit Degree of change 805 Apparent displacement: + 100 Significant displacement: +85

30 Getryggen E (70 132 13 268) Present-day altitudinal limits (1973) FL: 850, clumps of trees Fig. 18. The largest birch tree indicates the position of MSL: 8 I 0, a small number of stems the tree-limit in 1915/ 16 (PTL at locality 28; 825 m TL: 920, a 2 m high stem 1 a.s.l.). A stem core taken ea m above the snow Age-determination transect surface gave an age of 71 years. Despite the depth of 920 - 32 - 2.0 - 2 snow still lying here (ea I m) birch ieafing is quite well 880 - 58, 51' 50, 44, 34 - 4.0 - 2 advanced. Photo: June 5, 1974. ov5 - 55, 50, 40, 38, 36 - 4.5 - 2 840-34-4.5 -20 815 - 48 - 5.5 - 20 28 Norder-Tvad'tklumpen E (70 149 I3 269) 8IO - 64-6.0 - 20 Present-day altitudinal limits ( 1974) 795 - -;� - 6.0 - 20 FL: 840 , lobes Documentation MSL: 825, a small number of stems TL-Smith (53):8I2. Mrs Gunborg Antholm and Mr Sten TL: 915, four ea 2.5 m high stems Olofsson, both of Storvallen, state that the birch limit Age-determination transect is higher today than when they were young . 915 - 33 - 2.5 - 2 Past tree-limit Degree of change 890-37, 28-3.5-2 810 Apparent displacement: + 110 850 - 44, 42, 40, 36, 34, 34 - 2.7 - 2 Significant displacement: +95 825 - 51 - 5.0 - 1.3 825 - 55, 50, 27 - 3.3 - 2 3 I Getryggen SE (70 I I 9 I 3 259) 825-7I -6.0 -20 805 - 99, 94, 35 - 4.0 - 2 Present-day a/titudinal limits (1973) 805 - I 14 - 4. 0 - 20 FL: 845 , even limit MSL: 810, one stem Documentation TL: 890, a small number of individual trees with TL-Smith (51):803 . Mrs Gunborg Antholm and Mr Sten 2-3 m high stems Olofsson, both of Storvallen state that the birch limit is higher today than when they were young. Age-determination transect

Kilander (1955) recorded the following birch limits in 890 - 54 - 3 . 0 - I 0 I95I: 890 - 60 - 2.0 - 2 855, a I m high thicket Documentation 875 , five big bushes TL-Smith (54):808 . 865 , a 2 m high thicket Dr. Sven Kilander has placed the following unpub­ 830, a fringe of shrubs and low trees lished results of his own observations in 1948, at my Past tree-limit Degree of change disposal : 825 Apparent displacement: +90 880, shrubs Significant displacement: +90 845, a solitary tree 845, an isolated birch thicket 29 (70 I42 Norder-Tvaraklumpen SE I3 268) Past tree-limit Degree of change Present-day altitudinal limits ( 1977) 810 Apparent displacement: +80 FL: 790, wedge Significant displacement: +65

Acta phytogeogr. 65 suec. Change and stability of birch tree-limit in the Scandes 39

Fig. 21. The same tree as shown in Figs. 19-20. A comparison of the photographs indicates that no change in the vitality of this birch has occurred in 1972-1977. Maximum snow depth here does not ex­ ceed 30 cm, i.e. the photo provides no support for the view that, as a tree, the closer to the tree-limit birch grows the greater need it has for a deeper snow cover as a protection against the increasing severity of the local climate with increasing altitude. Photo: March 2, 1977.

Fig. 19. The tree-limit at locality 32 (935 m a.s.l.). 32 Getryggen S (70 115 13 244) Photo: August 6, 1972. Present-day altitudinal Limits (1978) FL: 840, wedges and small clumps of trees MSL: 835, a small number of stems TL: 930, a 2.5 m high stem SL: 945 , a 1.8 m high stem Age-determination transect 930 - 26 - 2.5 - 2 925 - 52 - 2.7 - 2 920 - 56 - 4.5 - 2 905 - 53 - 2.3 - 2 835 - 69 - 5.0 - 20 Documentation TL-Smith (58):830. Kilander (1955) recorded the following values in 1948-5 1: 920, a 1.5 m high thicket 916-985, a good number of fairly tall and slender shrubs and birch thickets, of which the highest mea­ sured 2.5 m, at 916 m altitude 895 , several trees, forming a thicket of 25 m2 in extent; he draws attention to the fact that these trees had obviously increased in height only a short time pre­ viously. 852, scattered trees 83�825, spearpoints of forest Fig. 20. The same as shown in Fig. 19. This birch has become established long after 1915/16, obviously as a Past tree-limit Degree of change result of the more rapid disappearance of the snow­ 835 Apparent displacement: +95 patch after that time. Photo: June 7, 1974. Significant displacement: +85

Acta phytogeogr. suec. 65 40 LeifKullm an

./>�. ·� Fig. 22. A birch tree growing 25 m below the tree-limit Fig. 23 . The same tree as in Fig. 22. A comparison of (930 m a.s.l.) at locality 32, where the tree-limit has these two photos shows the same depth and distribu­ risen by 85 m since 1915/16. The stoutest stem had a tion of the snow cover here in 1977 and 1978. Photo: stem base age of 53 years. Photo: March 2, 1977. March 24, 1978.

33 BHihammarfjallet SSW (70 114 13 22 1) MSL: 840, one stem TL: 890 , several individual trees with 2 m high Present-day altitudinal limits ( 1972) stems FL: 880, clumps of trees SL: 900, a 1.5 m high stem MSL: 845 , one stem TL: 895, a small number of 2-2 .5 m high stems Age-determination transect No investigation made Age-determination transect 895-41, 30-2.5-2 Documentation 845 - 76 - 3.5 - 20 TL-Smith (61):830 Documentation Past tree-limit Degree of change TL-Smith (3 1):854 830 Apparent displacement: +60 Significant displacement: +45 Past tree-limit Degree of change 855 Apparent displacement: +40 36 Lill-Ulvatjallet N (70 076 13 272) Significant displacement: + 25 Present-day altitudinaf limits ( 1975) 34 Stor-Ulvafj allet N (70 099 13 239) MSL: 870, a small number of stems TL: 875, two individual trees, each bearing Present-day altitudinal limits ( 1975) several ea 3 m high stems FL: 865 , clumps of trees MSL: 865, a small number of stems Age-determination transect TL: 915, a 3.2 m high stem 875 - 63 , 47 - 3.0 - 2 870 - 35, 28, 28 - 3.5 - 2 Age-determination transect 870 - 77 - 5.0 - 20 915-31 -3.2 -2 840 - 91 - 5. 0 - 2 890 -43, 40, 40, 37, 31 -4.3 -2 865 - 79 - 4.0 - 20 Documentation TL-Smith (62):85 1 Documentation TL-Smith (59) :884 Past tree-limit Degree of change 870 Apparent displacement: + 5 Past tree-limit Degree of change Significant displacement: +5 885 Apparent displacement: + 30 Significant displacement: + 15 37 Lill-Ulvatjallet E (70 069 13 279) Present-day altitudinal limits ( 1975) 35 Stor-Ulvafj allet SE (70 088 13 246) FL: 815, wedge Present-day altitudinal limits (1975) MSL: 850, several stems FL: 855, clumps of trees TL: 895, a 2.5 m high stem

Acta phytogeogr. suec. 65 Change and stability of birch tree-limit in the Scandes 41

Age determination transect 895 - 32 - 2.5 - 2 890-3 1-2 .0 -2 885 - 33 - 3.5 - 2 870 - 31' 30 - 2.5 - 2 865 - 33 - 2.5 - 2 850 - 74 - 4.5 - 20 835 - 77 - 4.5 - 2.0 Documentation Smith unquestionably visited this locality (cf. Smith 1920, p. 122). The absence of any cited altitude is almost certainly because the tree-limit lay between 829 and 851 m, the values determined at the nearest locali­ ties on either side of the locality now under discussion. Past tree-limit Degree of change 850 Apparent displacement: +45 Significant displacement: +45 Fig. 24. The tree-limit (900 m a.s.l.) at locality 38. The birch had a stem base age of 47 years. It is growing in a dwarf-shrub heath with Vaccinium myrtillus and Betu­ 38 Lill-Ulvatjallet SW (70 063 13 249) la nana as field-layer dominants. Dr. Sven Kilander Present-day altitudinal limits ( 1975) noted the presence of this· birch in 1951, at which time TL: 900, a 3.1 m high stem it was 0.5 m high. Despite the relatively unfavourable development of the climate since 1950, this stem has Age-determination transect managed to continue growing very well, a fact which 900-47-3.1 -2 indicates that the position of the tree-limit is not imme­ 890 - 33' 25 - 1.0 - 2 diately controlled by the ambient air temperature and Documentation its fluctuations during the vegetative period. Photo: Smith probably visited this locality. The absence of August 19, 1975. any altitudinal record may therefore be taken as an indication that no trees were growing above the valley bottom, at ea 870 m. 840 - 80, 74 - 5.0 - 20 Dr Sven Kilander's unpublished results from 1951 835 - 95 , 93 , 86, 83, 58 - 3.0 - 2 are as follows: Documentation 900 , ea 0.5 m high shrubs 890, two shrubs with coarse-grown stems, 0.5 m and TL-Smith (65):829 0.75 m high, respectively. Past tree-limit Degree of change Thanks to the detailed description given for this loca­ 840 Apparent displacement: +20 lity, there is no doubt whatsoever that the birches Significant displacement: + 20 described by Dr. Kilander in 1951 are identical to those which were included in my age-determination transect 40 Gas en W ( 69 998 13 318) made in 1975, i.e. the mean increase in stem length Present-day altitudinal limits ( 1972) during the period 1951-1975, 10 cm/year, is therefore a FL: 905, clumps of trees very precise value. MSL: 900, a small number of stems Past tree-limit Degree of change TL: 935, a 3 m high stem <870 Apparent displacement: + 30 Age-determination transect Significant displacement: + 30 900-84-3.5-20

39 b Endalshojden E (70 008 13 285) Documentation TL-Srnith (68):909. Smith calls this locality "Gasan", Present-day altitudinal limits ( 1975) which is very probably identical with the actual locality FL: 820, even limit mentioned above (cf. Kilander 1955, p. 52). MSL: 840, a small number of stems Kilander (op. cit.) quotes the following altitudinal TL: 860, two 3.5 m high stems limits, based on observations made 1950-5 1: SL: 870, several 1.5 m high shrubs, some of which 960, a prostrate bush were dead 952, a 1.5 m high thicket Age-determination transect 945-25, several low shrubs 870 - 40 - 1.5 - 2 935, a 1.75 m high shrub 860 - 30' 29 - 3.5 - 2 923, several bushes, maximum height 2.5 m 845 - 54, 38 - 3.3 - 2 924, a ea 3 m high thicket

Acta phytogeogr. suec. 65 42 Leif Kullman

920, a group of trees, forming a lobe of forest Past tree-limit Degree of change 965 +40 Past tree-limit Degree of change Apparent displacement: Significant displacement: + 25 910 Apparent displacement: +25 Significant displacement: + 15 42 Laptentjakke NW (70 087 13 291) Present-day altitudinal limits ( 1972) FL: 925 , even limit 41 Laptentjakke W (70 075 13 297) MSL: 875, a small number of stems Present-day altitudinal limits ( 1976) TL: 950, several individual trees, FL: 950, clumps of trees bearing 2-2.5 m high stems MSL: 920, a small number of stems Age-determination transect TL: I 005 , a 5 m high stem No investigation made Age-determination transect Documentation 1005 - 43 - 5.0 - 2 TL-Smith (77):883 1005-33-5.0-20 Past tree-limit 985 - 46, 41 - 4.5 - 2 Degree of change 885 985 - 35 - 4.5 - 2 Apparent displacement: +65 955 - 45, 44, 44, 34 - 4.3 - 2 Significant displacement: +50 920 - 85 - 4.0 - 20 43 Mettjeburretjakke W (70 109 13 288) Documentation Present-day altitudinal limits ( 1974) TL-Smith (73):964. FL: 885, even limit Dr. Sven Kilander has placed his unpublished results 885, for altitudinal limits, made in 1943, at my disposal . MSL: one stem 935, 2.5 These are cited below, together with his published TL: a m high stem results (Kilander 1955): Age-determination transect 1013, a shrub 925 - 53' 44 ' 41 - 3 . 3 - 2 975, a 3 m high tree 910 - 46 - 3.0 - 2 940, a few 4-5 m high trees 885 - 80, 62, 37 - 4.0 - 2 940 , a forest fragment 885 - 63 - 4.0 - 20

Fig. 25. A group of birches growing I 0 m below the pres­ ent-day tree-limit (935 m a.s.l., locality 43) and which became established after 1920. Across this shallow depression, at right angles to the slope, there is a pronounced ecological gradient with regard to the time of the snow-melt in spring, which is re­ flected in the composition of the vegetation. All the birches have become established in the same part of this gradient. In other words, birch colonisation and the upward displacement of the tree-limit appear to have been directly related to the more rap­ id disappearance of the snow cover, during the firsthalf of the present century. Nardus stricta dominates the vegetation of the lowest part of the ground de­ pression, with dwarf-shrub heaths, dominated by Vaccini­ um myrtillus and Betula nana , respectiveiy, at successively higher levels. Photo: June 10, 1974.

Acta phytogeogr. suec. 65 Change and stability of birch tree-limit in the Scandes 43

Documentation TL: 865, several 3 m high stems (79):884. TL-Smith This locality is named "Straten" Age-determination transect on Smith's map. 865 - 70, 46 , 44 - 3.0 - 2 Past tree-limit Degree of change 855 - 115, 65 , 33 - 4.5 - 2 885 Apparent displacement: +50 840-74-5.5-20 Significant displacement: + 35 Documentation TL-Smith (89):854 44 Straten WNW (70 131 13 295) Past tree-limit Degree of change Present-day altitudinal limits ( 1974) 855 Apparent displacement: + 10 FL: 875 , even limit Significant displacement: 0 MSL: 865, one stem TL: 945, a 2 m high stem SL: 950, a 2.5 m high, dead stem, with basal live 46 Hardeggen N (70 150 13 321) shoots several decimeters in length. Present-day altitudinal limits ( 1974) Age-determination transect FL: 855, even limit 930 - 58, 45, 45 - 3.0 - 2 MSL: 855, one stem 905 - 48, 48, 44, 38 - 3.0 - 2 TL: 935, two, single-stemmed, ea 2.5 m high indi- 880 - 53, 49, 46, 37 - 4.5 - 2 vidual trees 865 - 76 - 4.5 - 20 Age-determination transect 855 - 68 - 5.0 - 20 935 - 32,25 - 2.5 - 2 Documentation 925 - 30 - 3.0 - 2 TL-Smith (87 or 88):863 or 871 855 - 150, 106, 98, 58 - 3.5 - 2 855 - 78 - 3.5 - 20 Past tree-limit Degree of change 840 - 71 - 4.0 - 20 870 Apparent displacement: + 75 Significant displacement: +65 Documentation TL-Smith (90):836 45 Hardeggen· NW (70 149 13 315) Past tree-limit Degree of change Present-day altitudinal limits ( 1974) 855 Apparent displacement: +80 FL: 865 , even limit Significant displacement: +80 MSL: 840, several stems 47 Vasteran N (70 133 13 342) Present-day altitudinal limits (1977) FL: 875, a small, dense clump of trees MSL: 855, a small number of stems TL: 890, a small number of 3.5 - 4 m high individual birches Age-determination transect 890 - 53 - 3. 5 - 2 875 - 36, 33, 32 - 2.5 - 2 855 - 93 - 4.5 - 20 Documentation TL-Smith (92):850. Smith almost certainly calibrated his altimeter at pt. 926 shown on his map. This spot-height lies at ea 940 m according to the modem topographical map . Smith's values have therefore been corrected by + 14 m. Past tree-limit Degree of change 855 Apparent displacement: + 35 Significant displacement: + 35 Fig. 26. The tree-limit (935 m a.s.l.) at locality 46, a locality characterised by the large quantities of snow 48 W of Bunnran NNE (70 122 13 363) present in the extensive snow-field nearby at the time of birch leafing. In all probability these snow-fields Present-day altitudinal limits ( 1974) covered an appreciably larger area at the same time of FL: 800 , lobe the year in 1915/16, thereby making tree colonisation at MSL: 850, one stem that time impossible. Photo: June 8, 1974. TL: 855, a 2.5 m high stem

Acta phytogeogr. suec. 65 44 LeifKullm an

Age-determination transect Documentation No investigation made TL-Smith (97):802 Documentation Past tree-Limit Degree of change TL-Smith (93):850. Smith's value has been corrected 805 Apparent displacement : 0 by + 14 m for similar reasons as for locality 47. Significant displacement: 0 Past tree-limit Degree of change 850 Apparent displacement: + 35 Significant displacement: + 20 52 Rodberget S (70 163 13 428) Present-day altitudinal limits (1972) 49 NW of pt 1242 N (70 144 13 381) FL: 775, lobes and clumps of trees MSL: 765, one stem Present-day altitudinal limits (1974) TL: 775, a 2 m high stem FL: 785, clumps of trees MSL: 875, two stems Age-determination transect TL: 880, a small number of 2 m high stems No investigation made Age-determination transect Documentation 875-51,39-3.5-2 TL-Smith (98):770 875 - 64 - 3.5 - 20 64, Past tree-limit Degree of change 860 - 71 - 4.0 - 20 770 Apparent displacement: + 5 830 - 73, 69 - 4.0 - 20 Significant displacement: 0 815 - 117, 98, 70, 57-2.5 -2 800 - 103, 97, 28 -4.0 - 2

Documentation 53 Jarptm N (70 132 13 423) TL-Smith (95):800. Smith's value is probably too low, Present-day altitudinal limits ( 1976) because he was unaware of the existence of the FL: 780, clumps of trees highest-lying trees, which grow on sites hidden by rises MSL: 850, several 5-6 m high individual stems in the ground of this otherwise fairly flat terrain. TL: 875, a 2 m high, very slender stem Past tree-limit Degree of change Age-determination transect 875 Apparent displacement: + 5 875 - 21 - 2.0 - 2 Significant displacement: + 5 870 - 34, 28, 24 - 2.3 - 2 860 - 33 - 2.5 - 2 50 N of pt 1242 N (70 146 13 393) 850 - 84, 76 - 5.5 - 20 Present-day altitudinal limits (1974) 820 - 69, 27 - 5.5 - 20 FL: 835, lobes 800- 79 - 6.0 - 20 MSL: 835, a small number of stems Documentation TL: 860, a small dense clump of trees, bearing TL-Smith (99):796 2.5-3 m high stems Past tree-limit Degree of change Age-determination transect 850 Apparent displacement: + 25 860 -93, 63, 51, 42 -2.7-2 Significantdis placement: + 25 835 -66-3.2-20 83 5 - 95' 81 ' 65 - 3.6 - 2 815 - 117, 98, 70, 57 - 3.5 - 2 54 N Kyrkstensskaftet N (70 154 13 434) 815 - 73 - 6.5 - 20 Present-day altitudinal limits ( 1972) Documentation FL: 770, clumps of trees TL-Smith (96):835 MSL: 820, a small number of stems Past tree-limit Degree of change TL: 830, a small number of 2 m high stems 835 Apparent displacement: +25 Age-determination transect Significantdis placement: + 15 No investigation made

51 Grotmjolhogen S (70 155 13 416) Documentation TL-Smith (100):828. Smith describes two localities, Present-day altitudinal limits ( 1972) both of which he calls "Kyrkstensskaftet" . That both 800, lobe FL: were situated on the N-facing hillslope, broadly speak­ MSL: 805, one stem ing, seems a reasonable assumption, since there are no TL: 805 , a small number of 2-2 .5 m high stems trees growing in other quarters . A comparison of the Age-determination transect present-day highest tree-limit with the highest-lying of No investigation made Smith's two localities, thus seems justifiable.

Acta phytogeogr. suec. 65 Change and stability of birch tree-limit in the Scandes 45

Past tree-limit Degree of change MSL: 750, one stem 830 Apparent displacement: 0 TL: 830, several 2-2 .5 high stems Significant displacement: 0 Age-determination transect No investigation made 55 N Kyrkstensskaftet N (70 166 13 469) Documentation Present-day altitudinal limits ( 1972) TL-Smith (107):727. The nature of the terrain is such FL: 795, lobes that it cannot be ruled out that Smith overlooked the MSL: 790, a small numbers of trees highest-lying trees here. TL: 820, several 2.3 m high stems Past tree-limit Degree of change Age-determination transect 750 Apparent displacement: +80 No investigation made Significant displacement: +80 Documentation TL-Smith (103):785. Smith, in conformity with general 59 Kyrkstensfj allet (Kyrkstenen) E (70 107 13 491) usage on the maps of his time, calls this and the fo llow­ Present-day altitudinal limits ( 1976) ing three localities "Rekdalshojden". FL: 790 , even limit Past tree-limit Degree of change MSL: 790, a small number of stems 790 Apparent displacement: + 30 TL: 835, a group of 3-4 m high stems Significant displacement: + 30 SL: 855, a small number of 1-1.5 m high stems growing on rockface ledge a 56 N Kyrkstensskaftet NE (70 163 13 474) Age-determination transect 835 - 38, 37, 37, 32 - 3.5 - 2 Present-day altitudinal limits (1972) 830 - 48, 48, 30 - 2.3 - 2 FL: 800 , lobes 790 - 72 - 4. 0 - 20 MSL: 790, one stem TL: 830, a small number of 2.5-3 m high stems Documentation TL-Smith (121):814 Age-determination transect 790 - 68 - 3.5 - 20 Past tree-limit Degree of change 815 Apparent displacement: + 20 Documentation Significant displacement: + I 0 TL-Smith (104):786. Smith 's account of the position of the two, relatively close-together, spot-height, locali­ ties 104 and 105 is somewhat obscure. This is of minor 60 Rekhuvudet SW (70 163 13 505) importance, however, since it is clear from Smith's Present-day altitudinal limits ( 1971) data that tree limit was relatively uniform in alti­ the FL: 850, even limit tude all over the actual hillslope under discussion . MSL: 835, one stem Past tree-limit Degree of change TL: 870, a small number of 2-2.5 m high stems 790 Apparent displacement: +40 Age-determination transect Significant displacement: +40 No investigation made Documentation 57 N Kyrkstensskaftet E (70 153 13 483) TL-Smith (110):845 ( Present-day altitudinal limits 1972) Past tree-limit Degree of change 800 , FL: even limit 845 Apparent displacement: +25 MSL: 780, a small number of stems Significant displacement: + 10 TL: 850, several 2-2 .5 m high stems Age-determination transect 61 Ottfjallet NE (70 133 13 777) No investigation made Present-day altitudinal limits ( 1976) Documentation FL: 755, even limit TL-Smith (105):785. See the remarks under locality 56. MSL: 775 , several stems TL: 855, a 2 m high stem Past tree-limit Degree of change SL: 890, a 1.5 m high stem 785 Apparent displacement: +65 Significant displacement: +55 Age-determination transect 855 - 28 - 2.0 - 2 835 - 30 - 2.0 - 2 58 N Kyrkstensskaftet SSE (70 124 I 3 487) 830 - 37 - 3.0 - 2 Present-day altitudinal limits ( 1972) 815 -45, 35, 28, 22 -3.0 - 2 FL: 750, clumps of trees 775 - 78 - 4.5 - 20

Acta phytogeogr. suec. 65 46 Le ifKullman

Documentation 870 - 66 - 3.5 - 20 TL-Smith (115):840 865 -46, 42, 33 - 5.0 - 2 Past tree-limit Degree of change Doe umentation 850 Apparent displacement: + 15 TL-Smith (118):861. Significant displacement: 0 Kilander's (1955) observations, made in 1950, are as follows: 62 Ottfjallet NE (70 115 13 593) 938, a shrub 893 , a 3 m high, rapidly growing, arborescent speci­ Present-day altitudinal limits (1971) men together with a 2 m high shrub FL: 870, clumps of trees 820, a continuous lobe of forest MSL: 865 , one stem TL: 930, a dense clump of trees, with 2.5 - 3 m Past tree-limit Degree of change high stems 895 Apparent displacement: +40 Significantdi splacement: +40 Age-determination transect 865 - 74 - 5.5 - 20 65 Ottfjallet s (70 107 13 548) Documentation Present-day altitudinal limits ( 1971) In 1950 Kilander ( 1955) noted the presence of several FL: 860, clumps of trees 1.5 m high shrubs at 900-903 m altitude. MSL: 860, a few stems Past tree-limit Degree of change TL: 885, a small number of 3 - 3.5 m high stems 865 Apparent displacement: +65 Age-determination transect Significant displacement: +50 860-67-5.0-20

63 Ottfjallet SE (70 Ill 13 591) Documentation In 1950, Kilander (1955) found ten or so shrubs, almost Present-day altitudinal limits (1971) 2.5 m high, growing at 881 m. FL: 845, wedge MSL: 805 , a small number of stems Past tree-limit Degree of change TL: 935, a small number of 2-2.5 m high stems 860 Apparent displacement: +25 SL: 960, a small number of 1.5 - 1.8 m high shrubs, Significant displacement: + 25 the top parts of which were deadwood 66 Ottfjallet (Klappen) SW (70 101 13 554) Age-determination transect 805 - 81 - 5.0 - 20 Present-day altitudinal limits (1973) FL: 860 , clumps of trees Documentation MSL: 855, one st�m TL-Smith (117:)810 TL: 880, a few 2 - 2.5 m high stems Past tree-limit Degree of change SL: 910, some shoots, a few decimetres long 810 Apparent displacement: + 125 Age-determination transect Significant displacement: + 110 880 - 49 - 2.3 - 1 880 - 11 - 2.3 - 20 64 Ottfjallet (Pucklarna) SSW (70 099 13 577) 875 - 35 - 3.7 - 20 Present-day altitudinal limits 875-35-3.0 -2 FL: 865, clumps of trees 870 - 70 - 3.0 - 2 MSL: 885 , a small number of stems 870 - 21 - 3.0 - 20 TL: 935, a 2 m high stem Documentation Age-determination transect TL-Smith (108):842. 920 - 35 - 2.5 - 2 In 1950, Kilander ( 1955) noted the following altitudi­ 915 - 22 - 2.5 - 20 nal limits: 915 - 42 ,32 - 2.5 - 2 858, 845 , 840, spearpoints of more or less continuous 910 - 27 -2.1 -2 thickets; 848 a large tree 905 - 32 - 2.3 - 2 Past tree-limit Degree of change 900 - 33 - 2.7 - 2 855 Apparent displacement: + 25 895 - 32 - 3.0 - 2 Significant displacement: + 25 895 - 28 - 2.8 - 10 89 5 - 63 ' 20 - 3.0 - 20 67 Middagsvalen SSE (70 064 13 609) 890-53-3.0 -10 885 - 33 - 2.5 - 2 Present-day altitudinal limits ( 1977) 880 - 58 - 3.0 - 2 FL: 815, small clumps of trees 880 - 22 - 3.0 - 20 MSL: 815, a small number of stems

Acta phytogeogr. suec. 65 Change and stability of birch tree-limit in the Scandes 47

TL: 825 , a multi-stemmed birch, the longest stem Past tree-limit Degree of change 4 m high. 840 Apparent displacement: +30 Significant displacement: + 15 Age-determination transect 825 - 55, 37 - 3.0 - 2 815- 112-6.5 -20 71 Pt. 1011 S (70 066 13 459) Documentation Present-day altitudinal limits (1974) TL-Smith (120):826 FL: 920, lobe Past tree-limit Degree of change MSL: 920, one stem 825 Apparent displacement: 0 TL: 945, a 2.5 m high stem Significant displacement: 0 Age-determination transect 940 - 48, 30, 28 - 3.0 - 2 68 Middagsvalen NE (70 069 13 609) 920 - 74, 64-4.0 - 2 Present-day altitudinal Limits (1974) 920 - 65 - 4.5 - 13 FL: 810, even limit 895 - 35 - 5.0 - 20 MSL: 800 , one stem 890 - 72 - 5.0 - 20 TL: 825, a few 2 m high stems Documentation Age-determination transect TL-Smith (123):845 825 - 37, 32 - 2.0 - 2 Past tree-limit Degree of change 800 - 62 - 4. 0 - 20 890 Apparent displacement: +55 Doe umentation Significant displacement: +55 Smith's maximum tree-limit for this small hill was 826 m (=preceding locality) 72 Stor-Stensdalsfjallet S (70 068 13 456) Past tree-limit Degree of change 800 Apparent displacement: + 25 Present-day altitudinal limits (1972) Significant displacement: + 25 FL: 890, clumps of trees MSL: 865, one stem TL: 945 , a few 2-2.5 m high stems 69 Middagsvalen W (70 067 13 605) Age-determination transect Present-day altitudinal limits (1974) 865 - 74 - 3.5 - 20 FL: 810, even limit MSL: 800, several stems Documentation TL: 820, a few 2-3 m high stems TL-Smith (124):85 1. Smith gives values for four, im­ SL: 825, a small number of 0.5 - 1 m high stems perfectly localised, points from E to W along this hill­ slope. The positions of the fu rthest-east and furthest­ Age-determination transect west of these localities (pts. 124 and 127) can be deter­ 820 - 34' 27' 27 - 3.0 - 2 mined with a fair degree of certainty (my localities 72 805 - 62 - 3.0 - 2 and 73, respectively), thanks to other, easily identified, 800 - 84 , 69 - 5.5 - 20 localities in their immediate vicinities. Documentation Past tree-limit Degree of change See locality 68 865 Apparent displacement: +80 Past tree limit Degree of change Significant displacement: +80 800 Apparent displacement: +20 Significant displacement: + 20 73 Stor-Stensdalsfjallet S (70 074 13 438)

70 S Kyrkstensskaftet SE (70 074 13 488) Present-day altitudinal limits (1972) FL: 860 , clumps of trees Present-day altitudinal limits ( 1974) MSL: 900, several stems FL: 805 , lobes TL: 965 , a 2 m high stem MSL: 830, a small number of stems TL: 870, a small number of 2-3 m high stems Age-determination transect 900 - 82 - 3. 5 - 20 Age-determination transect 870 -47, 43, 37 -2.5-2 Documentation 850 - 84 , 81 ' 56 - 3.0 - 2 TL-Smith (127):915. See locality 72. 830 - 78 - 3.5 - 20 Past tree-limit Degree of change Documentation 915 Apparent displacement: +50 TL-Smith (122):838 Significant displacement: + 35

Acta phytogeogr. suec. 65 48 LeifKullm an

74 Stor-Stensdalsfjallet S (70 073 13 429) Present-day altitudinal limits ( 1972) FL: 860, clumps of trees MSL: 890 , one stem TL: 970, a small number of 2 m high stems SL: 980, a small number of 1.5 - 1.8 m high stems Age-determination transect 890 - 79 - 4.0 - 20 Documentation TL-Smith (128):875. See locality 72. Past tree-limit Degree of change 890 Apparent displacement: +80 Significant displacement: +80

75 b Bunnerstoten S (70 068 13 396) Present-day altitudinal limits (1977) Fig. 27. The uppermost tree-sized birch at locality 75 FL: 950, even limit (990 m a.s.l.). At leafing time the nearest snow-patch is MSL: 940, several stems ea 5 m away from this birch tree. Judging from the TL: 990, a 2.1 m high stem dimensions of the stem, the stem base age would not SL: 1020, a small number of 0.5 - 1.3 m high exceed 25 years. Photo: June 29, 1976. shrubs Age-determination transect 985 - 31' 26 - 2.0 - 2 980 - 27' 21 - 2. 0 - 2 955 - 48, 36, 36, 32, 32 - 5.0 - 2 945 - 32 - 5.5 - 20 940 - 76, 60, 62 - 4.5 - 20 Documentation TL-Smith (130):960

Past tree-limit Degree of change 960 Apparent displacement: + 30 Significant displacement: + 15

Fig. 28. The arrow marks the position of the tree shown in Fig. 27. The establishment of this birch, and thus the rise in the tree-limit as well, is obvious­ ly related to the local snow ac­ cumulations seen on the photo, which by all accounts were even more widespread at the same season of the year in 1915/16. Photo: June 29, 1976.

Acta phytogeogr. suec. 65 Change and stability of birch tree-limit in the Scandes 49

76 Sj tantja N (70 068 13 396) Present-day altitudinal limits ( 1977) FL: 895, clumps of trees MSL: 895, one stem TL: 905, a small number of 2-2.5 m high stems Age-determination transect 905 - 35 - 2.5 - 2 895 - 89 - 5.0 - 20 880 - 79 - 6.5 - 20 Documentation TL-Smith (131):900 Past tree-limit Degree of change 900 Apparent displacement: + 5 Significantdisplacement: 0

77 Tubbeke SE (70 049 13 428) Present-day altitudinal limits ( 1974) FL: 915, even limit MSL: 910, one stem Fig. 29. A ring count of a stem core taken 2 m above TL: 940, a 2.5 m high stem the ground gave an age of 71 years for this well-grown SL: 970, several 0.5 - 1.5 m high shrubs birch, which thereby indicates the position of the tree­ limit in 1915/16 (PTL). The birches growing higher up Age-determination transect the hillslope have all attained tree height considerably 940 - 33 - 2.5 - 2 later than that date. Locality 78, 930 m a.s.l. Photo: 920 -44, 43, 41, 40, 39 - 2.8 - 2 June 30, 1974. 910-65-4.5 - 20 900 - 80 - 5.0 - 20 79 Lill-Stensdalsfjallet N (70 039 13 455) Documentation TL-Smith (134):910. From Smith's isohypsometric map Present-day altitudinal limits (1974) (Karta l) it is clear that he calibrated his altimeter on FL: 885, tongues and lobes the summit of this small hill, at 1032 m, a value which MSL: 870, a small number of stems coincides exactly with that given on the modern topo­ TL: 970, several 2.5 m high stems graphical map. Age-determination transect Past tree-limit Degree of change 970 - 55, 42 - 2.5 - 2 910 Apparent displacement: + 30 960 - 36 - 3.5 - 2 Significantdispla cement: + 25 910-38-2.2 -2 880 - 73, 53 - 5.5 - 20 Documentation TL-Smith (140):878. Smith mentions values fo r three, 78 Lill-Stensdalsfjallet W (70 046 13 441) rather imprecisely located, places on this hillslope. The Present-day altitudinal limits ( 1974) easternmost of these has been selected for comparison, FL: 920, diffu se limit with the TL value for the eastern part of the N -facing MSL: 930, several stems hill slope. TL: 955, scattered trees and small clumps of trees, Past tree-limit Degree of change maximum height 2.5 m 880 Apparent displacement: +90 Age-determination transect Significant displacement: +80 955 -45, 38, 33, 31, 24-2.3-2 930 - 68, 45 , 41, 39, 37 - 5.0 - 2 80 Lill-Stensdalsfjallet ENE (70 022 13 469) 930 - 71 - 5.0 - 20 Present-day altitudinal limits ( 1974) Documentation FL: 850, clumps of trees TL-Smith (137):905 MSL: 865, a small number of stems TL: 920, an isolated clump of trees, ea 3 m high Past tree-limit Degree of change 930 Apparent displacement: + 25 Age-determination transect Significant displacement: + 25 865 - 69 - 3.5 - 20

Acta phytogeogr. suec. 65 50 LeifKullman

Documentation 84 Gruvsmallen SSE (69 954 13 459) TL-Smith (142):875 Present-day altitudinal limits (1974) Past tree limit Degree of change FL: 945 , small clumps of trees 875 Apparent displacement: +45 MSL: 955, mouldering remains of quite coarsely- Significantdispla cement: + 35 dimensioned, old stems TL: 955, a 3.2 m high stem

81 Smallhogarna NW (70 018 13 4 78) Age-determination transect 955 -42-3.2-2 Present-day altitudinal limits ( 1974) 945-61, 57, 53, 48-4.0 -2 FL: 875, clumps of trees MSL: 880, one stem Documentation TL: 920, two 3.5 m high stems Since this locality was almost certainly visited by Smith, the absence of any value for the tree-limit here Age-determination transect can probably be assumed to indicate that trees were 920 - 42 - 3.5 - 2 either absent, or present in only very small numbers 905 - 51 - 3.0 - 2 (i.e. overlooked). 880 - 65 - 5.5 - 20 Past tree-limit Degree of change Documentation 955 Apparent displacement: 0 TL-Smith (143):870 Significantdisplace ment: 0 Past tree-limit Degree of change 880 Apparent displacement: +40 85 Valavalen N (69 970 13 490) Significantdispla cement: +40 Present-day altitudinal limits (1972) FL: 920, clumps of trees 82 Smallhogarna NNE (70 018 13 487) MSL: 900, one stem TL: 940, small clumps of trees , ( Present-day altitudinal limits 1976) bearing 2 m high stems FL: 890, clumps of trees MSL: 890, a small number of stems Age-determination transect TL: 935, a 2.3 m high stem 900 - 67 - 3.0 - 20 SL: 940, a 1.9 m high stem Documentation Age-determination transect TL-Smith (147):910 935 - 42 - 2.3 - 2 Past tree-limit Degree of change 925 - 38, 36, 35, 33 - 2.8 - 2 910 Apparent displacement: + 30 890 - 106, 83 , 69, 59, 34 - 4,5 - 2 Significantdisp lacement: +20 890 - 79 - 4.5 - 20 Documentation 86 Valavalen s (69 965 13 513) TL-Smith (144):905 Present-day altitudinal limits ( 1972) Past tree-limit Degree of change FL: 975 , wedge 905 Apparent displacement: + 30 MSL: 915, one stem Significant displacement: + 25 TL: 980, a small number of 2 m high stems Age-determination transect 83 Smallhogarna E (69 993 13 475) 915 - 74 - 3.5 - 20 Documentation Present-day altitudinal limits ( 1974) TL-Smith (149) :920 FL: 875, clumps of trees MSL: 885, several stems Past tree-limit Degree of change TL: 925, a 3 m high stem 920 Apparent displacement: +55 +50 Age-determination transect Significant displacement: 925 - 22 - 3.0 - 20 915 - 60, 55 - 3.0 - 2 87 Valavalen ESE (69 965 13 515) 915 - 31 - 3.0 - 20 Present-day altitudinal limits (1972) 885 - 79 - 6.0 - 20 FL: 950, clumps of trees Documentation MSL: 940, a small number of stems TL-Smith (145):903 TL: 985, a multi-stemmed individual tree, ea 2 m high Past tree-limit Degree of change 905 Apparent displacement: + 20 Age-determination transect Significant displacement: + 10 No investigation made

Acta phytogeogr. suec. 65 Change and stability of birch tree-limit in the Scandes 51

Documentation TL-Smith (148):946 Past tree-limit Degree of change 945 Apparent displacement: +40 Significantdi splacement: + 30

88 Luspentjarve N (69 930 13 481) Present-day altitudinal limits (1972) FL: 915, clumps of trees MSL: 940, three stems TL: 940, three 3.5 m high stems Age-determination transect 940 - 78 - 3.5 - 20 Documentation TL-Smith (152):937 Past tree-limit Degree of change 940 Apparent displacement: 0 Significantdisplacement : 0 Fig . 30. The tree-limit at locality 89 (960 m a.s.l.). The 89 Luspentjarve E (69 935 13 492) longest stem had a stem base age of 31 years. The Present-day altitudinal limits ( 1974) displacement of the tree-limit at this locality, character­ FL: 900, clumps of trees ised by marked snow accumulation, has nevertheless MSL: 920, one stem remained relatively slight, because of the absence of TL: 960, a small number of 2-2.5 m high stems suitable edaphic conditions above the altitude of the Age-determination transect 1915/16 tree-limit. Photo: July 2, 1974. 960 - 31 - 2.3 - 2 930 - 102 - 3.5 - 2 920 - 58 - 4.0 - 20 Documentation 910 - 72 - 4.0 - 20 TL-Smith (156):963 900 - 80 - 4.5 - 20 Past tree-limit Degree of change Documentation 965 Apparent displacement: + 25 TL-Smith (153):940. Smith's observations can scarcely Significantdisplaceme nt: + 15 have been made on the actual S-facing slope of the mountain, since at no point does this slope extend as 91 Grasjofjallet ENE (69 943 13 514) low down as 940 m a. s. 1. and today it is completely Present-day altitudinal limits (1974) destitute of any vestiges of birch growth. With the FL: 910, even limit greatest probability his value instead refers to the S­ MSL: 925, a small number of stems facing flank of one of the morainic ridges which are TL: 990, a 2 m high stem present on the E-facing slope of the mountain. Age-determination transect Past tree limit Degree of change 990 - 3 1 - 2.0 - 2 + 20 940 Apparent displacement: 975-42-3.5 -2 Significant displacement: + 10 965 - 3 8' 34 - 3 . 0 - 2 955 - 33 - 3.5 - 2 90 Grasjofjallet w (69 939 13 506) 940 - 32, 30 - 2.7 - 2 Present-day altitudinal limits ( 1974) 925 - 7 4 - 5.0 - 20 FL: 945 , tongues and lobes Documentation MSL: 950, one stem TL-Smith (157):936 TL: 990, a 2 m high stem SL: 1000, a small number of 0.5 m high shrubs Past tree-limit Degree of change 935 Apparent displacement: +55 Age-determination transect Significant displacement: +45 990 - 32 - 2.0 - 2 980 - 34 - 2.5 - 2 92 Trondfjall S (69 934 13 539) 975-51, 37, 35, 32-3.0 -2 965 - 31 - 4.5 - 20 Present-day altitudinal limits (1976) 960 - 27 - 4.0 - 20 FL: 950, clumps of trees 950 - 81 - 4.5 - 20 MSL: 975, one stem

Acta phytogeogr. suec. 65 52 LeifKullman

94 Trondfjall NW (69 95 1 13 539) Present-day altitudinal limits (1971) FL: 940, tongue MSL: 940, one stem TL: 950, a 2.3 m high stem Age-determination transect 940 - 89 - 4.0 - 20 Documentation For localities situated on either side of the one under discussion, Smith cites values of 950 and 910 m, re­ spectively. The actual tree-limit probably lay some­ where in between these two values. Past tree-limit Degree of change 940 Apparent displacement: + 10 Significant displacement: 0

Fig . 31. At locality 92 the 1915/16 tree-limit (PTL) is 95 Trondfjall N (69 962 13 559) indicated by the birch tree shown, 975 m a.s.l. A core from this particular tree, taken 2 m above the ground, Present-day altitudinal limits (1971) gave an age of 78 years. The vegetation in the immedi­ FL: 875, tongue ate vicinity is dominated by Vaccinium myrtillus. MSL: 905, one stem Photo: July 5, 1976. TL: 905, a few 3 m high stems Age-determination transect 905 - 77 - 3.0 - 2 1010, TL: a multi-stemmed birch, maximum height 905 - 68 - 3.0 - 20 2m SL: 1025, a small number of 0.5 - 1.5 m high Documentation shrubs TL-Smith (163):910 Past tree-limit Degree of change Age-determination transect 910 Apparent displacement: -5 1010 - 22 - 2.0 - 2 Significant displacement: 0 985 - 56 - 3.0 - 2 985 - 28 - 1.8 - 2 96 V Endalshojden SW (70 028 13 197) 980 - 30 - 2.0 - 2 975 - 78 - 4.0 - 20 Present-day altitudinal limits ( 1976) FL: 870, clumps of trees Documentation MSL: 870, a small number of stems TL-Smith (161):975 TL: 905 , a clump of stems, maximum height 3 m Past tree-limit Degree of change Age-determination transect 975 + 35 Apparent displacement: 905 - 76, 58, 49, 40, 39 - 2.7 - 2 + 25 Significant displacement: 900 - 57 - 3.0 - 20 870 - 85 - 4.5 - 20 93 Trondfjall W (68 940 13 534) Doeume ntation Present-day altitudinal limits ( 1976) TL-Smith (29):830. FL: 960, clumps of trees In 1949 Kilander ( 1955) found an extensive stand of MSL: 950, a small number of stems arborescent, bushy birches at ea 900 as well as a 3 m TL: 995, a 2 m high birch m, and a 4 m high tree growing at 872 m. Age-determination transect Past tree-limit Degree of change 995 - 26 - 2.0 - 2 900 Apparent displacement: + 5 985 - 29 - 2.0 - 2 Significant displacement: + 5 980 -42, 37, 35, 33, 28-4.5 -2 950-81-5 .5 -20 97 Fruntimmersklumpen E (69 970 13 253) Documentation Present-day altitudinal limits ( 1977) TL-Smith (162):950 FL: 870, a few small clumps of 2 - 2.5 m high stems Past tree-limit Degree of change MSL: 865, a multi-stemmed birch, including the 950 Apparent displacement: +45 mouldering remains of former stems which Significant displacement: + 35 exceeded 2 m in length

A eta phytogeogr. suec. 65 Change and stability of birch tree-limit in the Scandes 53

TL: 905 , an individual tree with five 2-2.5 m high 985, a 1.75 m high tree stems 981, a shrub 980, a thicket, maximum height 1.5 m Age-determination transect 957, a thicket, 2 m high 905 - 39 - 2.3 - 1 875 - 58 - 3.0 - 2 100 Nj ameletjarve SSW (69 823 13 204) 875-34-3.0 -13 870 - 37' 35 - 2.5 - 2 Present-day altitudinal limits (1975) 865 - 63 - 3.0 - 2 FL: 885, clumps of trees MSL: 885, a small number of stems Documentation TL: 885, a few 3 m high stems Smith (1920, p. 122) visited this area, but makes no SL: 900 , a dead, 1.5 m high stem, surrounded by mention of any arborescent birches, which suggests basal shoots a few dm in length that no such specimens grew above the floor of the valley (ea 850 m a. s. 1.). Sporadic trees may, however, Age-determination transect have gone unnoticed in this very broken terrain, with 885 - 55, 42, 38 - 3.0 - 2 its multitude of low ridges and hillocks rising above the 885 - 64 , 31-3.0 -20 relatively gently-sloping hillside. 865 - 82, 75, 74, 53, 43 - 3.0 - 20 Past tree-limit Degree of change Documentation 865 Apparent displacement: +40 TL-Smith (391):875. Smith (1951, p. 374) states that the Significantdi splacement: +40 forest-limit in 1915 lay at 870 m and had advanced to 925 m by 1950. The latter value is probably too high, since no birch fo rest grows above 905 m anywhere 98 Hammaren E ( 69 909 13 246) between Njameletjarve and Predikstolen (cf. Fax en Present-day altitudinal limits (1977) 1951, p. 454). FL: 900, small clumps of trees Past tree-limit Degree of change TL: 920, four 2-2.5 m high stems 885 Apparent displacement: 0 SL: 945, a 1.3 m high shrub; Significant displacement: 0 975 , several ea 30 cm high shoots

Age-determination transect 101 Nj ameletjarve SW (69 815 13 216) 920 - 39 - 2.5 - 2 890 - 45, 43, 33 - 2.5 - 2 Present-day altitudinal limits (1975) 890 - 35 - 3.5 - 20 FL: 905, scattered clumps of trees 885 - 27 - 2.2 - 2 MSL: 900, one stem 885 - 84, 76 - 2.5 - 2 TL: 930, a 2.5 m high stem Documentation Age-determination transect Smith (1911, p. 506) reproduces a photograph showing 930 - 38 - 2.5 - 2 bushy birches, 0.5 m high, growing at 920 m altitude. 920 - 58 - 2.7 - 2 910 - 56, 43, 35 - 2.5 - 2 The tree-limit, therefore , at the beginning of the pre­ sent century, lay below 920 m. Smith's isohypsometric 905 - 63 - 2.5 - 13 map (Karta 1), however, indicates that isolated clumps 900-62-3.5-20 of trees, or solitary trees, were growing hereabouts at Documentation ea 900 m. TL-Smith (390):880 In 1951 Kilander ( 1955) fo und a 3 m high tree grow­ Past tree-limit Degree of change ing at 918 m, as well as a 1 m high shrub at 995 m and a 900 Apparent displacement: + 30 low-growing clump of trees at 900 m altitude. Significant displacement: + 30 Past tree-limit Degree of change 900 20 Apparent displacement: + 102 Predikstolen SSW (69 788 13 269) Significant displacement: + 10 Present-day altitudinal limits ( 1975) FL: 900, clumps of trees 99 Helagsfjallet S (69 780 13 320) TL: 1035, a 2.1 m high stem Present-day altitudinal limits (1975) Age-determination transect TL: 955, a 2 m high, multi-stemmed birch 1000 - 62, 33 - 2.3 - 2 Age-determination transect 990 - 60, 28 - 3.0 - 2 955 - 40 - 2.0 - 2 960 -62, 51, 38, 38 -3.0-2 Documentation Documentation Kilander (1955) gives the following observations made TL-Smith (388):885. Smith (1920, p. 102) noted creep­ in 1950: ing shrubs growing at 1000 m. When he revisited this

Acta phytogeogr. suec. 65 54 Leif Kullman

Fig. 32. The tree-limit (1015 m a.s.l.) at locality 103. Fig. 33. The same tree as in Fig. 32. The longest stem One of the stems has quite recently been broken by the has become considerably more bent down than it was weight of the snow cover. Photo: August 2, 1973. in 1973. Photo: August I, 1976.

Fig. 34. The same tree as in Figs . 32-33. Some of the basal shoots are in process of growing to tree-size. A Fig. 35. The birch shown in the three fo re-going views comparison with the earlier figures shows that there (Figs. 32-34) is growing more or less at the spot indi­ has been a continuous regression of the low-growing cated by the arrow. The hill slope here receives an willow shrub (Salix sp.) in front of this birch . Photo: extremely deep snow cover, which is liable to ava­ July 12, 1977. lanche. Photo: April 4, 1975.

Acta phytogeogr. suec. 65 Change and stability of birch tree-limit in the Scandes 55 locality in 1950, he found that the tree-limit had risen to 106 Dunsjofjallet W (69 806 13 451) 990 m, at which altitude the highest-lying stems were Present-day altitudinal limits (1975) ea 3 m high (Smith 1951). FL: 890, even limit Past tree-limit Degree of change MSL: 890, a few stems 885 Apparent displacement: + 150 TL: 930, a clump of trees, maximum height 3 m Significant displacement: + 140 Age-determination transect 930 - 39, 33, 32 - 3.0 - 15 890 - 79 - 3.5 - 20 103 Husvalen SSE (75 765 13 506) Doe umentation Present-day altitudinal limits (1977) TL-Smith (197):920 FL: 950, clumps of trees Past tree-limit Degree of change MSL: 855, a small number of stems 920 Apparent displacement: + 10 TL: 1015, a few 2.1 m high individual birches with Significantdi splacement: 0 a large number of metre-high basal shoots

Age-determination transect 107 Dunsjofjall W (69 828 13 447) 1015 -21-2 .1 -2 995 -43, 32, 31, 28-4.0-2 Present-day altitudinal limits (1975) 955 - 38, 38, 29, 26 - 3.5 - 2 FL: 97 5, clumps of trees 855-81-4.0 -20 MSL: 975, a small number of stems TL: 1025, a few 2.5 - 3 m high stems Documentation TL-Smith (191):925 Age-determination transect 1025 - 27 - 3. 0 - 2 Past tree-limit Degree of change 1010 - 40, 31, 27-2.5 -2 925 Apparent displacement: +90 1010 - 30 - 1.5 - 1 Significant displacement: + 75 990-45, 41, 36, 34, 28 -3.0-2 875 - 67 - 4.5 - 20 965 - 69 - 5. 0 - 20 104 Husvalen SSW (69 769 13 492) . Documentation Present-day altitudinal lrmits ( 1973) TL-Smith (199):974 FL: 900, clumps of trees Past tree-limit Degree of change MSL: 880, one stem 975 Apparent displacement:. + 50 TL: 930, a 2.5 m high stem Significant displacement: + 35 Age-determination transect 930 - 34 - 2.5 - 5 108 Dunsjofjall w (69 852 13 44 1) 880-74-3.0 -20 Present-day altitudinal limits (1975) Documentation FL: 925, even limit TL-Smith (193):934 MSL: 925, one stem Past tree-limit Degree of change TL: 960, a fe w 2-3 m high stems 935 Apparent displacement: -5 Age-determination transect Significant displacement: 0 960-3 1-3 .0 -2 950 - 29, 25 - 2.0 - 2 940 - 29 - 3.0 - 20 105 Nedre Lillvalen WSW (69 768 13 485) 930 -44, 41 - 4.0 - 20 925 - 72 - 4. 0 - 20 Present-day altitudinal /imits ( 1973) FL: 900, diffu se limit Documentation MSL: 900, a small number of stems TL-Smith (202):945 TL: 925, a 2.5 m high stem Past tree-limit Degree of change Age-determination transect 945 Apparent displacement: + 15 890 - 88 - 3.0 - 20 Significant displacement: + 5 Documentation TL-Smith (194):920 109 Herrjangsasen S (69 90 1 13 329) Past tree-limit Degree of change Present-day altitudinal limits ( 1977) 920 Apparent displacement: + 5 TL: 980, a 2.3 m high stem, which looked quite Significant displacement: 0 young; in addition to this tree there were only

Acta phytogeogr. suec. 65 56 Le ifKullman

Fig. 36. The tree-limit (1025 m a.s.l.) at locality 107 is Fig. 37. The same birch as in Fig. 36. The lowermost formed by a birch tree growing in a thicket of willow branch has been riven off since 1973 , presumably as a (Salix spp.) and juniper (Juniperus communis) shrubs result of the excessive weight of the snow cover in about 1 m high. The birch is unlikely to be more than spring. Photo: July 8, 1975. 25-30 years old. Photo: July 31, 1973 .

two single birches present on this hillslope, 111 Vargtjarnstoten SSW (69 819 13 429) above the level of the valley floor (ea 920 m Present-day altitudinal limits (1973) a. s. 1.): at 960 m a 2 m high stem and at 950 m a FL: 950, lobes and clumps of trees single specimen with two 1.2 m high stems MSL: 930, a few stems Documentation TL: 990, a small number of stems, maximum height Smith (1920, p. 119) states, with regard to the mountain 2m plateau S of the Herrjfmg massif (at ea 920 m altitu­ SL: 1010, a few bushes, 0.5 m high de)- " .... despite favourable soil conditions here, there is no trace .... of tree-growth at 920 m above Age-determination transect s.l.". 990-37, 33, 28, 27, 24 -2.0 - 1 Boberg (1920, p. 92) states that no trees were to be 980 - 34 - 3.5 - 2 seen on the S-facing slope of Herrjangsasen, or on the 965 - 39, 33, 28, 23 - 3.0 - 2 level slope below. 930 - 62 - 4.0 - 20 Past tree-limit Degree of change Documentation <920 Apparent displacement: +60 TL-Smith (210):949 Significant displacement: +60 Kilander (1955) determined the altitudinal limits for birch, in 1950 and 1952, as follows: 1000 , bushes, a good metre in height 110 Vargtjarnstoten E (69 821 13 432) 975, bushes, about one metre in height 968 , a bush almost 2 in height Present-day altitudinal limits (1973) m 956, a 3.5 m high tree FL: 900, even limit 930, strips of forest MSL: 890, a few number of stems TL: 950, 2.5 m high stem Past tree-limit Degree of change a 950 Apparent displacement: +40 Age-determination transect Significant displacement: + 30 890 - 82 - 3. 5 - 20 Documentation 112 Stortuvan SSW (69 814 13 404) TL-Smith (208): 900 Present-day altitudinal limits (1973) Past tree-limit Degree of change FL: 935, wedge 900 Apparent displacement: +50 MSL: 900, a few stems Significant displacement: +40 TL: 935, a smallnum ber of 2-2.5 m high stems

Acta phytogeogr. suec. 65 Change and stability of birch tree-limit in the Scandes 57

114 Kesudalen S (69 839 13 403) Present-day altitudinal limits ( 1973) FL: even limit MSL: 875, one stem TL: 930, a small number of 2-2.5 m high stems Age-determination transect 875 - 91 - 4.5 - 20 Documentation TL-Smith (214):904. This value is mentioned in Smith's text (1920, p. 105) in such a relationship to other nearby Fig. 38. Several of these birch stems were at least 2 m localities, which can be identified with fair certainty, long in 1915/16, i.e. the tree-limit at this locality (no. that it is highly probable that he is referring to precisely 113) has remained unchanged. The terrain is fairly flat the place on the S-facing slope of the valley which is and receives an inconsiderable snow cover. Now­ locality 114. adays, as in 1915/16, large parts of this area become Dr. Sven Kilander (pers. comm.) states that conti­ nuous forest extended up to an altitude of 875 m in snow-free long before the time at which the birches break into leaf. Photo: April 7, 1975. 1950. Past tree-limit Degree of change 905 Apparent displacement: + 25 Age-determination transect Significantdisp lacement: + 20 900 - 69 - 4.5 - 20 Documentation 115 Torkilstoten NE (69 791 13 420) TL-Smith (213):904 Kilander's (1955) observations, made in 1950, are as Present-day altitudinal limits (1975) follows: FL: 895, even limit 929, a thicket MSL: 870, one stem 920, a 3 m high shrub TL: 950, a small number of 2-2.5 m high stems 917, sparse forest Age-determination transect Past tree-limit Degree of change 950 - 26 - 2.5 - 2 905 Apparent displacement: + 30 870 - 88 -4.5 - 20 Significantdispla cement: + 25 Documentation TL-Smith (217) :860. Mr Johan Jonsson, Lj ungdalen, 113 Kesudalen SSE (69 832 13 377) states that the birch limit lies higher today than when Present-day altitudinal limits (1975) he was young. FL: 895 , tongues and lobes Past tree-limit Degree of change MSL: 925, two stems 870 Apparent displacement: +80 TL: 925, a sparse clump of trees, with stems Significantdi splacement: +80 3-3.5 m high Age-determination transect 925 - 69' 64 - 3. 5 - 20 116 Torkilstoten SE (69 781 13 422) 915 - 36 - 2.5 - 2 Present-day altitudinal limits (1975) 895-51-6.0 -20 FL : 945, even limit 895 -64-4.0 - 20 MSL: 910, one stem Documentation TL: 960, several 2.5 - 3 m high stems TL-Smith (215):880. Smith probably overlooked the SL: 995, a 0.5 m high shrub highest-lying birches here, which grow in a broken Age-determination transect terrain, often hidden from view. 960 - 34, 23 - 3.0 - 2 Kilander (1955) determined the following altitudinal 945 -46, 38, 35, 32 - 5.0 - 2 limits for birch in 1950. 930 - 53, 40, 35, 32 - 6.5 - 2 935-925, multitude of thickets, maximum height 910 - 62 - 6.0 - 20 2.5 m 905, a clump of fo ur trees Documentation 895, a forest lobe TL-Smith (219-22 l):max . 92 1 Past tree-limit Degree of change Past tree-limit Degree of change 925 Apparent displacement: 0 920 Apparent displacement: +40 Significant displacement: 0 Significant displacement: + 35

Acta phytogeogr. suec. 65 58 LeifKullm an

117 Stotliden SE (69 765 13 406) Present-day altitudinal limits (1975) FL: 920, clumps of trees MSL: 905 , a small number of stems TL: 965, a few 2 m high stems Age-determination transect 960 - 50 - 2.5 - 13 905 - 84 - 3.0 - 20 Documentation TL-Smith (222):909 Past tree-limit Degree of change 910 Apparent displacement: +55 Significant displacement: +45

118 Viksjovalen E (69 735 13 434) Present-day altitudinal limits ( 1975) FL: 880, clumps of trees MSL: 875, a few stems TL: 895, a few 2-3 m high stems 39. (965 121. Age-determination transect Fig. The tree-limit m a.s.l.) at locality 26 895 - 44, 39, 37 - 2,7 - 2 The birch had a stem base age of years. It is growing in a vegetation characteristic of habitats with a fairly 87 5 - 78 - 3. 5 - 20 long-lasting snow cover combined with nutrient-rich Documentation soil conditions. Characteristic species include: An­ TL-Smith (223):890 thoxanthum odoratum, Deschampsia caespitosa, Gali­ Past tree-limit Degree of change um boreale, Geranium sylvaticum, Polygonum vivipa­ 890 Apparent displacement: + 5 rum, Ranunculus acris, Solidago virgaurea and Viola Significant displacement: 0 biflora . Photo: August 1, 1973 .

119 Viksjovalen W (69 734 13 417) Documentation Present-day altitudinal limits (1975) TL-Smith (226):940. Smith (1911, p. 526) mentions that FL: 920, clumps of trees ''a proper little forest of stunted birches'' was growing MSL: 905 , one stem just below 1000 m a. s. I. TL: 925, a fe w 2-2.5 m high stems Past tree-limit Degree of change Age-determination transect 940 Apparent displacement: +65 905 - 68 - 2.8 - 20 Significant displacement: +55 Documentation TL-Smith (224):888 121 S Grondorrstoten S (69 756 13 388) Past tree-limit Degree of change Present-day altitudinal limits ( 1976) 905 Apparent displacement: +20 FL: 940, even limit Significant displacement: + 20 MSL: 900 , one stem TL: 965 , a 2.5 m high stem 120 N Grondorrstoten S (69 769 13 391) Age-determination transect 965 - 26 - 2.5 - 2 Present-day altitudinal limits ( 1975) 945 - 48, 44, 38, 36, 34 - 3.0 - 2 FL: 985 , even limit 925 -52, 44, 41, 40-4.5 - 13 MSL: 935, a few stems 900-91-5.0 -20 TL: 1005, a 2 m high stem Documentation Age-determination transect TL-Smith (227):910. Mr Johan Jonsson, Lj ungdalen, 1005 - 26 - 2. 0 - 2 states that the birch limit lies higher today than when 1000 - 17 - 2.5 - 2 he was young. 990 - 46 - 3.0 - 13 980 -47, 47,39, 37, 34 -3.5 - 13 Past tree-limit Degree of change 965 - 53 , 46, 43, 40 , 37 - 4.0 - 13 910 Apparent displacement: +55 935 - 66 , 60 - 4.5 - 20 Significantdi splacement: +45

Acta phytogeogr. suec. 65 Change and stability of birch tree-limit in the Scandes 59

124 Gronfjallet s (69 724 13 392) Present-day altitudinal limits ( 1975) FL: 865, clumps of trees MSL: 930, one stem TL: 965, a 2 m high stem Age-determination transect 965 - 26 - 2.0 - 2 955 - 26, 26 - 2.3 - 2 950 - 57, 33, 32, 31, 30-2.5-2 930 - 60 - 4.0 - 20 915 - 52 - 3.2 - 20 Documentation TL-Smith (233):909 Past tree-limit Degree of change 930 Apparent displacement: + 35 Significantdispla cement: + 35

Fig. 40. The tree-limit (965 m a.s.l.) at locality 124. These birches were only seedlings at the close of the 125 Flatruet (Falkvalen) NNE (69 653 13 447) 1940's. They now suffer greatly from the effects of snow pressure. The vegetation is a dwarf-shrub heath Present-day altitudinal limits (1977) dominated by Vaccinium myrtillus, interspersed with FL: 880, clumps of trees patches of pure Nardus stricta, i.e. the area does not MSL: 885, one stem become snow-free until quite late on in spring. Photo: TL: 925, a multi-stemmed birch, maximum height July 9, 1975. 2.2 m SL: 945, a 1.8 m high stem Age-determination transect 945 - 15 - 1.8 - 1 925 - 29, 22 - 2.2 - 1 122 Pt. 977 (Gruvfjallet) E (69 745 13 394) 895 - 31, 25 - 2.3 - 2 Present-day altitudinal limits ( 1973) 885 -63, 35, 34, 30, 27, 25 - 4.5 -2 FL: 860, clumps of trees 885 - 104 - 5.0 - 20 MSL: 885, one stem Documentation TL: 920, a 2 m high stem TL-Smith (240):890. Mr Albert Langstrom, of Skarkda­ SL: 935, a 1.8 m high stem len, states that the birch limit lies higher today than Age-determination transect when he was young (about 50 years ago). 885 - 62 - 3.5 - 20 Past tree-limit Degree of change Documentation 890 Apparent displacement: + 35 TL-Smith (228):891 Significant displacement: + 25 Past tree-limit Degree of change 890 Apparent displacement: + 30 Significant displacement: + 25 126 Flatruet (Hardangesbacken) NNE (69 64 1 13 468) 123 Gronfjallet E (69 728 13 396) Present-day altitudinal limits (1975) Present-day altitudinal limits (1973) FL: 890, clumps of trees FL: 860, small clumps of trees MSL: 915, one stem MSL: 910, one stem TL: 915, a few 3-4.5 m high stems TL: 925, a small number of 2.5 - 3 m high stems Age-determination transect Age-determination transect 915 - 36, 34, 30, 28 - 4.0 - 2 910 - 67 - 3.5 - 20 915 - 82 - 3.5 - 20 Documentation Documentation TL-Smith (231):92 1 TL-Smith (241):903 Past tree-limit Degree of change Past tree-limit Degree of change 920 Apparent displacement: + 5 915 Apparent displacement: 0 Significantdispla cement: 0 Significant displacement: 0

Acta phytogeogr. suec. 65 60 Le ifKullman

Fig. 41. Young, multi-stemmed, birches growing 20 m below the tree-limit (925 m a.s.l.) at locality 125. In Fig. 42. The same birch clump as shown in Fig. 41. front of them is a narrow belt of Salix lapponum, to­ gether with patches of Betula nana. Photo: July 27, During the intervening period (1973-1977) some of the central group of tree-sized stems have died off, while 1973. other stems have thinned-out somewhat. In the dense thicket of birch, visible on the right-hand side of the central group mentioned above, some of the stems seem to be in process of becoming tree-sized, while the others have suffered a decline, like some of the stems to the left of the central group. The fringing willow thicket has remained more or less unchanged in extent. Photo: July 11, 1977.

Fig. 43. The same view as in Figs. 41-42. The max­ imum depth of the snow cover in this birch stand is a little over 1 m. Photo: February 26, 1978.

127 Sarvvalen NW (69 647 13 497) Present-day altitudinal limits (1975) FL: 920, clumps of trees MSL: 920, a few stems TL: 920, a large number of 3-4 m high stems Age-determination transect 920 - 59, 49 - 3.5 - 20 920 - 42 - 4.0 - 2 910 - 30 - 4.0 - 20 900 - 64 - 4.0 - 20 Documentation Fig. 44. The tree-limit (915 m a.s.l.) at locality 126 has TL-Smith (243):927. Smith does not state just which remained unchanged throughout the present century. part of Sarvvillen his observation refers to . Almost The large birch tree was already at least 2 m high at the certainly, however, he would have selected the locality end of the 19th century. The terrain is relatively flat where the tree-limit lay highest, which, to judge from and the snow cover is shallow, usually melting-away the altitude of the MSL here, was probably on the long before the birches have burst into leaf. Photo: NW-facing hillslope. April 6, 1975.

Acta phytogeogr. suec. 65 Change and stability of birch tree-limit in the Scandes 61

Past tree-limit Degree of change 131 b Stoljan S (69 576 13 515) 925 Apparent displacement: -5 Present-day altitudinal limits (1975) Significantdisplacement: 0 FL: 880, wedge MSL: 900, one live stem, together with a large tree- 128 V Stoljan NNE (69 618 13 511 ) stump, one metre in height Present-day altitudinallimits (1975) TL: 910, dense 2 m high clump of trees FL: 880, even limit Age-determination transect MSL: 890, one stem 910 - 40, 38, 27, 26 - 2.0-3 TL: 920, a few 2-2.5 m high stems 900 - 69 - 3.0 - 20 Age-determination transect 880 - 61 - 4.0 - 20 890 - 67 - 4.5 - 20 Documentation Documentation TL-Smith (252):904 TL-Smith (245):890. Smith is here probably referring to Past tree-limit Degree of change the NE-facing hillslope, since at no point does the 905 Apparent displacement: +5 N-facing slope descend as low as 890 m. Significant displacement: 0 Past tree-limit Degree of change 890 Apparent displacement: + 30 Significant displacement: + 20 132 Ruandan SSE (69 565 13 542)

129 b Stoljan NE (69 602 13 517) Present-day altitudinal limits (1975) FL: 935, clumps of trees Present-day altitudinal limits (1975) MSL: 935, a few stems 890, wedge FL: TL: 950, a multi-stemmed 2 m high birch MSL: 905 , mouldering remains of quite coarsely­ dimensioned, old arborescent stems Age-determination transect TL: 905 , a multi-stemmed birch, maximum height 950 - 42 - 2.2 - 1 2.2 m 945 - 27 - 1.8 - 1 935 - 28, 27' 25 - 2.0 - 1 Age-determination transect 935 - 52, 45, 33 - 3.0 - 20 905 - 50 - 2.2 - 2 930 - 75, 50 - 3.5 - 20 895 - 76 - 4.0 - 20 880 - 69 - 5.0 - 20 Documentation TL-Smith (251):927 Documentation TL-Smith (246):884. Smith is here probably referring to Past tree-limit Deg;�e of change some place on the NE-facing hillslope, somewhat 930 Apparent displacement: + 20 further E than the fo regoing locality. This interpreta­ Significant displacement: + 20 tion is based on the fact that at no point does the N -facing slope proper descend as low as 884 m. Past tree-limit Degree of change 133 Svartmorhojden S (69 585 13 476) 905 Apparent displacement: 0 Significant displacement: 0 Present-day altitudinallimits (1974) FL: 920, even limit MSL: 940, a few stems 130 b Stoljan NE (69 595 13 527) TL: 945 , a small number of 2.3 -4 m high birches Present-day altitudinal limits ( 1975) SL: 955, a few multi-stemmed 1.5 m high shrubs FL: 870, wedge Age-determination transect MSL: 885, a large tree-stump, formerly bearing an 955 - 51 - 1.5 - 1 arborescent and very old stem 945 - 48 , 48 - 3.0 - 2 TL: 885, a few 2.5 - 3 m high stems 940 - 52 , 49, 40 , 33, 27 - 2.8 - 2 Age-determination transect 940 - 76 - 4.0 - 20 885 -66, 49, 31, 27, 27-3.0 - 13 925 -70, 44, 43 , 37, 35, 35 -3.0-2 870 - 68 - 5.0 - 20 910 - 69 - 4.5 - 20 Documentation Documentation TL-Smith (247):887 TL-Smith (253):900 Past tree-limit Degree of change Past tree-limit Degree of change 885 Apparent displacement: 0 940 Apparent displacement: + 5 Significant displacement: 0 Significantdisplacement: + 5

Acta phytogeogr. suec. 65 62 Le if Kullman

134 Falkvalen SSW (69 608 13 421) Past tree-limit Degree of change 965 Present-day altitudinal limits (1975) Apparent displacement: +40 +40 FL: 890, clumps of trees Significantdi splacement: MSL: 900, one stem TL: 930, a small number of 3 - 3.5 m high stems 137 Lill-Axhogen S (69 659 13 306) Age-determination transect Present-day altitudinal limits ( 1976) 930 - 41 ' 40 - 3. 3 - 2 FL: 950, clumps of trees 915 - 42, 28 - 3.0 - 2 MSL: 960, one stem 910 - 60 - 4.0 - 3 TL: 990, a small number of 2.5 m high stems 905 - 60, 47, 46, 40 - 2.8-2 Age-determination transect 900 - 75 - 5.0 - 20 990 - 50, 46 - 2.5 - 2 Documentation 975 -48, 41, 30-3.5-2 TL-Smith (255):902 965 -49, 42, 41, 37 -2.5 - 2 Past tree-limit Degree of change 960-65-3.0 - 20 900 Apparent displacement: + 30 Documentation Significant displacement: + 20 TL-Smith (265):925 Past tree-limit Degree of change 960 Apparent displacement: + 30 Significantdis placement: + 30 135 Korpasen S (69 612 13 407) Present-day altitudinal limits (1975) 138 Mittahammaren S (69 67 1 13 281) FL: 910, even limit MSL: 920, a small number of stems Present-day altitudinal limits ( 1972) TL: 955, several 2.5 - 3 m high stems FL: 935, even limit MSL: 925, a few stems Age-determination transect TL: 945, several 2.5 - 3 m high stems 955 - 87' 82, 63 - 2.8 - 2 940 - 61, 59, 56, 50, 37 - 3.0 - 2 Age-determination transect 920 - 107-4.5 - 20 925 - 86 - 4. 5 - 20 Documentation Documentation TL-Smith (256) :930 TL-Smith (267):932 Past tree-limit Degree of change Past tree-limit Degree of change 930 Apparent displacement: + 25 930 Apparent displacement: + 15 Significantdisplaceme nt: + 15 Significantdi splacement: + 10

139 Lill-Mittaklappen NW (69 659 13 281) Present-day altitudinal limits ( 1972) 136 Stor-Axhogen S (69 644 13 329) MSL: 900, a few stems Present-day altitudinal limits ( 1976) TL: 900, a small number of 2-3.5 m high stems FL: 950, clumps of trees Age-determination transect MSL: 965 , a large tree-stump, formerly bearing an 900-64-3.5-20 arborescent and very old stem. TL: 1005 , two individual birches with 3 m high Documentation stems TL-Smith (270): 890 SL: 1010, an individual tree, with three dead stems, Past tree-limit Degree of change not long ago ea 2 m high, with live basal shoots 900 Apparent displacement: 0 several dm long Significant displacement: 0 Age-determination transect 1005-32-3.0 -2 985 - 60, 59, 54, 45 - 3.0 - 2 140 Lill-Mittaklappen NE (69 659 13 281) 955 - 51' 45 , 38, 25 - 3.3 - 2 Present-day altitudinal limits (1972) 955 - 55 - 4.5 - 20 FL: 900, clumps of trees 945 - 40 - 5.0 - 20 MSL: 915, a dead, very coarsely-dimensioned stem 925 - 69 - 5.0 - 20 TL: 920, a few 2 m high stems Doe umentation Age-determination transect TL-Smith (263) :940 895 - 79 - 3.5 - 20

Acta phytogeogr. suec. 65 Change and stability of birch tree-limit in the Scandes 63

Documentation TL-Smith (271):915 Past tree-limit Degree of change 915 Apparent displacement: + 5 Significant displacement: 0

141 Lill-MittakUippen E (69 650 13 291) Present-day altitudinal limits (1972) FL: 900, even limit MSL: 890, a few stems TL: 930, a small number of 2.5 - 3 m high stems

Age-determination transect 890 - 91 - 4.0 - 20 Documentation TL-Smith (272):900 Past tree-limit Degree of change 900 Apparent displacement: + 30 Fig. 45. The present-day tree-limit (TL) at locality 142 Significant displacement: + 20 is fo rmed by a dense stand of birch stems bowed down by the weight of the snow cover and which were at most a fe w decimetres in length in the mid- 1920's. 142 Lill-Mittaklappen s (69 642 13 289) They had probably only colonised this spot at about Present-day altitudinal limits (1975) that same time. The birches are growing in a dwarf­ FL: 910, clumps of trees, which form strips shrub heath dominated by Vaccinium myrtillus and running parallel to the contours Betula nana, also with species such as Anthoxanthum MSL: 910, one stem odoratum, Deschampsia flexuosa, Nardus stricta, TL: 960, a small clump of trees, with stems Rumes acetosa ssp. lapponicus and Solidago virgau­ 2.5 - 3 m in height rea . The species composition of the vegetation strongly suggest that the site is subject to a long-lasting snow Age-determination transect cover. Photo: July 23, 1975. 960 - 50, 47' 39 - 2.8 - 2 935 - 47, 45, 29 - 3.0 - 2 910 - 80 - 6.0 - 20 860 - 72 - 5.0 - 20 Documentation TL-Smith (273):880. Henning (1887, p. 10) describes the vegetation cover of this hillslope without making the slightest mention of the occurrence of even scatter­ ed trees on the S-facing slope itself, above the level of

Fig. 46. The arrow marks the position of the birch stand in Fig. 45. Birch growth here in 1915/16 was probably impos­ sible because of the slower dis­ appearance of the large snow­ field here at that time. Photo: July 13, 1972.

Acta phytogeogr. 65 suec . 64 Le ifKullman

the valley floor. The kind of vegetation cover he Past tree-limit Degree of change describes suggests an appreciable accumulation of 960 Apparent displacement: 0 snow here in winter. Significantdisplacem ent: 0 Past tree-limit Degree of change 910 Apparent displacement: +50 146 Gruvvalen SSW (69 611 13 261) Significantdispla cement: +50 Present-day altitudinal limits (1975) FL: 925, clumps of trees MSL: 920, a few stems 143 Stor-MittakHippen NE (69 638 13 287) TL: 935, a small number of 2.5 m high stems Present-day altitudinal limits ( 1975) Age-determination transect MSL: 885, a few number of stems 935 - 42, 31 - 2.5 - 2 TL: 895, a small number of 2-3 m high ste ms 930 -41, 38, 30 - 3.0 - 2 Age-determination transect 920 - 101, 89, 66-4.5-2 885 - 67 - 3.5 - 20 920 - 70 - 4.5 - 20 Documentation 915 - 76 - 5.0 - 20 TL-Smith (274):895. Smith gives three values (pts. Documentation 274-276), from "NW to S", for Stor-MittakHippen. It is TL-Smith (277):925 obvious that they refer to the NE-, E-, and SSE-facing Past tree-limit Degree of change hillslopes, respectively. 925 Apparent displacement: + 10 Past tree-limit Degree of change Significant displacement: + 5 895 Apparent displacement: 0 Significantdisplace ment: 0 147 Vallarfjallet SW (69 536 13 311) Present-day altitudinallimits (1974) 144 Stor-Mittakhippen E (69 623 13 288) FL: 880, clumps of trees MSL: 895 , one stem Present-day altitudinal limits (1975) TL: 950, a 2 m high stem FL: 850, clumps of trees MSL: 925, one stem Age-determination transect TL: 1005 , a small number of 2 m high stems 895 - 68 - 4.0 - 20 Age-determination transect Documentation 1005 - 31 - 2.0 - 2 TL-Smith (284):910 985 - 34 - 2.0 - 2 Past tree-limit Degree of change 980 - 34 - 2. 5 - 2 910 Apparent displacement: +40 960 - 46, 29, 25 - 3.5 - 2 Significant displacement: + 30 925 - 67 - 3. 5 - 20 905 - 88, 61 - 6.0 - 20 148 Vallarfjallet SE (69 536 13 314) Documentation Present-day altitudinal limits ( 1974) TL-Smith (272):900. See locality 143. FL: 880, clumps of trees Past tree-limit Degree of change MSL: 885, a few stems 925 Apparent displacement: +80 TL: 940, a 2 m high stem Significant displacement: +80 Age-determination transect 930 - 50 - 3.5 - 20 145 Stor-MittakHippen SSE (69 617 13 288) 885 - 78 - 5.0 - 20 Present-day altitudinal limits (1975) Documentation FL: 910, clumps of trees TL-Smith (283):890 MSL: 960, one stem Past tree-limit Degree of change TL: 960, a small number of 2-3.5 m high stems 890 Apparent displacement: +50 SL: 980, a 1.5 m high stem Significant displacement: +40 Age-determination transect 960-91-3 .5 -20 149 Kappruet WNW (69 534 13 430) 960 - 58, 38, 32 - 2.5 - 2 Present-day altitudinal limits (1975) 935 - 74 - 4.0 - 20 FL: 925, wedge 935 - 63 , 51 - 4.0 - 2 MSL: 930, a few mouldering remains of old Documentation arborescent stems TL-Smith (276):926. See locality 143. TL: 930, a small number of 2-2.5 m high stems

Acta phytogeogr. suec. 65 Change and stability of birch tree-limit in the Scandes 65

Age-determination transect 925 - 82 - 4.5 - 20 Documentation TL-Smith (286):920 Past tree-limit Degree of change 930 Apparent displacement: 0 Significant displacement: 0

150 Kappruet S (69 525 13 450) Present-day altitudinal limits (1974) FL: 975, even limit MSL: 985, one stem TL: 985, several 2.5 - 4.5 m high stems Age-determination transect 985 - 38 - 4.5 - 2 985 - 65, 40 - 4.0 - 20 975 - 68, 50 - 3.5 - 2 Fig. 47. The two nearest stems seen in the photograph Documentation form the tree-limit (970 m a.s.l.) at locality 152 at the TL-Smith (288):979 present-day (TL). Their ages, estimated from cores taken 2 m from the stem base, were 95 and 68 years , Past tree-limit Degree of change respectively, which indicates that the tree-limit here 985 Apparent displacement: 0 has not been displaced during the present century. Significantdis placement: 0 Photo: August 19, 1973 .

151 Am1kroken S (69 500 13 415)

Present-day altitudinal limits ( 1976) Age-determination transect FL: 1005, clumps of trees 970 - 95' 68 - 4.0 - 20 MSL: 1015, mouldering remains of a quite coarsely- dimensioned, old stem Documentation TL: 1030, a small number of 2-2.5 m high stems TL-Smith (289):960. Smith gives no definite indication SL: 1050, a few 0.5 - 1.5 m high shrubs of the aspect of this site. That it can scarcely be the S-facing hillslope is clear from the argument advanced Age-determination transect under locality 151, and Smith gives other values which 1005 - 60 - 4.0 - 20 definitelyrefer to the N- to NE-facing slope. The E-fac­ 995 -92-5.0-20 ing slope nowhere descends so low as 960 m, i.e. only Documentation the W -facing slope is left. A few kilometres E of this locality Smith recorded the Past tree-limit Degree of change 1007 highest tree-limit for the whole country, at m. It 970 Apparent displacement: 0 would therefore seem highly probable that the tree-li­ Significantdispla cement: 0 mit at this precise locality in fact lay very near 1007 m altitude, otherwise Smith would almost certainly have 153 Between Anakroken and Roaldsstoten SSW noted the fact, since he determined the tree-limit on (69 485 13 426) several other slopes of this particular mountain. Present-day altitudinal limits (1973) Degree of change Past tree-limit MSL: 1005, one stem 1015 Apparent displacement: + 10 TL: 1015, a small number of clumps. of trees, + 10 Significantdispla cement: with 2 - 3 m high stems Age-determination transect 1005 - 73 - 4.0 - 20 152 Anakroken W ( 69 505 13 410) Documentation Present-day altitudinal limits (1973) TL-Smith (297): 1007. In 1915 the highest altitudinal FL: 950, lobes and clumps of trees tree-limit in the country was recorded at this locality. MSL: 970, several stems, together with the moulde­ ring remains of a very coarsely-dimensioned Past tree-limit Degree of change tree 1005 Apparent displacement: + 10 TL: 970, a large number of 2.5 - 4 m high stems Significant displacement: 0

Acta phytogeogr. suec. 65 66 LeifKullm an

154 Annfjiill NNE (69 487 13 398) Documentation TL-Smith (299):956 Present-day altitudinal limits ( 1976) FL: 910, clumps of trees Past tree-limit Degree of change MSL: 945, several stems 955 Apparent displacement: + 5 TL: 960, small clumps of 3-4 m high stems Significantdi splacement: 0 Age-determination transect 945 - 80 - 4.0 - 20 158 Uggarna SE (69 452 13 460) Documentation Present-day altitudinal limits (1975) TL-Smith (307):954 FL: 975 , lobe MSL: 955, one live stem, together with the Past tree-limit Degree of change mouldering remains of several coarsely­ 955 Apparent displacement: + 5 dimensioned, very old, stems Significant displacement: 0 TL: 995 , a small number of 2 - 2.5 m high stems 155 Fj iilliindan S (69 460 13 474) Age-determination transect 995 - 43 - 2.5 - I Present-day altitudinal limits ( 1975) 975 - 83 , 54, 49, 43 , 40 - 3.0 - 2 FL: 955, clumps of stems 975 -57, 51, 50-4.0 -20 MSL: 985, one stem 955 - 70, 70, 62 - 4.0 - 20 TL: 1020, a 2.0 m high stem SL: 1040, a 0.6 m high shrub Documentation TL-Smith (300):954 Age-determination transect 1020 - 32 - 2.0 - 1 Past tree-limit Degree of change 1015 - 33 - 2.0 - 2 955 Apparent displacement: +40 1005 - 40, 36, 28, 25 - 2.5 - 2 Significant displacement: + 30 985 -69-3.5 - 20 960-71, 62-4.0 -20 159 Grastoten s (69 445 13 404) 945 -68-4.0 - 20 Present-day altitudinal limits ( 1974) Documentation FL: 955, even limit TL-Smith (298): 1002 MSL: 1040, one stem Past tree-limit Degree of change TL: 1040, a multi-stemmed, 2.5 m high birch 1000 Apparent displacement: +20 Age-determination transect Significantdispla cement: + 10 1040 - 65 - 2. 5 - 17 1040 - 19 - 2.5 - 2 156 Fj aiJ::indan SSE (69 460 13 487) 995 - 40, 39, 32, 30, 30 - 2.5 - 2 Present-day altitudinal limits ( 1973) 995 - 69 - 3.0 - 13 FL: 925, even limit 970 -55, 51, 49, 46, 42 -2. 5-2 MSL: 945, one stem 960 - 63 - 3.5 - 20 TL: 975, a small number of 2 - 2.5 m high stems Documentation Age-determination transect Hisinger ( 1820), using a mercury barometer, determin­ 945 - 67 - 4.5 - 2.0 ed the "birch limit" on this hillslope to be 3261 .88 Sw feet (i.e. 968 m) in 1819. Two hours previously he had Documentation determined the altitude of the highest point to be TL-Smith (295):940 3762.00 Sw feet (i.e. 1117 m), which is 6 m lower than Past tree-limit Degree of change the modern value. Hisinger's "birch limit" ought 945 Apparent displacement: + 30 therefore to be corrected to 974 m a. s. I. The term Significant displacement: + 30 "birch limit" should refer to some kind of closed stand of birch, since at certain other localities he also deter­ 157 Between U ggarna and Fj iillandan S mined what he called "the limit of the highest-growing (69 455 13 466) bushy birches", which ought probably to agree more or less with the definition of the 'tree-limit" used in the Present-day a/titudinal limits (1975) present investigation. FL: 960, clumps of trees Immediately to the E and W of this locality Smith MSL: 930, a few stems records values of 942 and 948 m, respectively. Since he TL: 960, a small number of 2.5 - 3 m high stems certainly must have passed by the S-facing slope of Age-determination transect Grastoten, it would therefore seem probable that he 960 - 60' 37' 3 5 - 2. 7 - 2 would have made particular mention of the fact if the 930 - 94 - 5.0 - 20 tree-limit value there had deviated appreciably from

Acta phytogeogr. suec. 65 Change and stability of birch tree-limit in the Scandes 67

Fig. 48. The tree-limit at locali­ ty 159 has remained stable dur­ ing the present century. The ter­ rain above the tree-limit is char­ acterised by pronounced snow deflation. This locality is gener­ ally free of snow long before the birches burst into leaf and the vegetation is scarcely influ­ enced by snow meltwater at all during the vegetation period. Photo: April 27, 1976.

t

those cited above. Nevertheless, the highest-growing Age-determination transect birches on that slope are scattered very far apart and 1045-1 7-2.0- 1 do not stand out well against the boulderstrewn and 1040 - 27 - 2.0 - 1 quite steep, hillslope. There is therefore a strong pro­ 1 025 - 3 5 ' 34 - 3 . 0 - 2 bability that Smith overlooked the highest-lying bir­ 1010 -41,38, 27, 17-3.5-2 ches here. 995 - 68 -7.0 - 20 970 - 86 - 6.0 - 20 Past tree-limit Degree of change 1040 Apparent displacement: 0 Documentation Significant displacement: 0 TL-Smith (306):948 Past tree-limit Degree of change 160 Grastoten SW (69 452 13 395) 995 Apparent displacement: +50 Present-day altitudinal limits ( 1974) Significant displacement: +50 FL: 960, wedge A MSL: 950, a few stems 162 nnfjallet W (69 472 13 379) TL: 965 , a small number of 2-2.5 m high stems Present-day altitudinal limits (1975) Age-determination transect FL: 980, lobe 950 - 70 - 4.0 - 20 MSL: 995, one stem TL: 1035, a 2.2 m high stem Documentation TL-Smith (304):948 Age-determination transect 1035- 17-2.2- 1 Past tree-limit Degree of change 1030 - 30 - 2.5 - 2 950 Apparent displacement: + 15 980 - 65 - 5.5 - 20 Significant displacement: 0 965-61-5 .0 -20 Documentation 161 Annfjallet SE (69 467 13 376) TL-Smith (305):960 Present-day altitudinal limits (1976) Past tree-limit Degree of change FL: 985, lobe 995 Apparent displacement: +40 MSL: 995 , a small number of live stems, together Significant displacement: +40 with the mouldering remains of a few coarse stems 163 Ormruet N (69 466 13 355) TL: I 045, two 2 m high stems SL: 1105, two metre-long, creeping stems of the Present-day altitudinal limits (1975) same individual FL : 925, lobe

Acta phytogeogr. suec. 65 68 LeifKullman

Fig. 49. In response to a more rapid snow-melt on the leeward side of the ridge visible in the background the birch tree-limit at locality 161 has risen 50 m in altitude since 1915/16. The approximate position of the present-day tree-limit is shown by the arrow. Photo: April 27, 1976.

MSL: 930, one mouldering, very coarse stem, which 165 Giertebaune S (69 634 13 198) at one time was appreciably more than 2 m Present-day altitudinal limits (1975) in height FL: 910, clumps of trees TL: 955, a small number of 2-2.5 m MSL: 885, a few stems high stems TL: 920, a clump of stems, maximum height 2 m SL: 960, a few 0.5 m high shrubs Age-determination transect Age-determination transect 885 - 79 - 4. 0 - 20 955 - 31' 26 - 2.5 - 1 940 - 38 - 3.0 - 2 Documentation 920- 103-5.0 -20 TL-Smith (335):920 Documentation Past tree-limit Degree of change TL-Smith (331):942 920 Apparent displacement: 0 Significant displacement: 0 Past tree-limit Degree of change 940 Apparent displacement : + 15 Significant displacement: + 10 166 Kejsam SW (69 653 13 146) Present-day altitudinal limits (1975) FL: 960, clumps of trees 164 Rostvalen S (69 622 13 236) MSL: 925, a few stems Present-day altitudinal limits (1975) TL: 975, clumps of 2-3 m high stems FL: 920, clumps of trees Age-determination transect MSL: 910, one stem 925 - 82 - 4.5 - 20 TL: 945, a 2.3 m high stem Documentation Age-determination transect TL-Smith (336):926 945 - 31 - 2.3 - 2 930-31, 30-3.0-2 Past tree-limit Degree of change 920 - 44, 43, 36, 35 - 4.5 - 2 925 Apparent displacement: +50 920 - 40 - 4.5 - 20 Significantdis placement: +40 910 - 104 - 6.0 - 20

Documentation 167 Haftorsstoten ESE (69 647 13 135) TL-Smith (334):920 Present-day altitudinal limits ( 1975) Past tree-limit Degree of change FL: 880, clumps of trees 920 Apparent displacement: +25 MSL: 905, one stem Significant displacement: + 20 TL: 945, a small number of 2.5 m high stems

Acta phytogeogr. suec. 65 Change and stability of birch tree-limit in the Scandes 69

Age-determination transect Documentation 905 - 84 - 6.0 - 20 TL-Smith (341):929 885 - 107 - 6.0 - 20 Past tree-limit Degree of change Documentation 930 Apparent displacement: + 30 TL-Smith (339):890 . Significant displacement: +20 In 1819 Hisinger (1820), using a mercury barometer, found that the "birch limit" at Lj usnetjarn,i.e. on the SE-facing slope of Haftorsstoten, lay at 3095.14 Sw 170 Gronvalen S (69 625 13 141) feet (equivalent to 919 m). The height determined for Lj usnetjarn is 4 m higher than the modern value, i.e. Present-day altitudinal limits ( 1976) the corrected value for Hisinger's "birch limit" is thus FL: 900, wedges and clumps of trees 915 m a. s. 1. As mentioned above (locality 159), the MSL: 915, a few stems "birch limit" is assumed to refer to some kind of TL: 955, a 2.5 m high stem closed stand of birch. Age-determination transect H�rbye (1861, p. 133) determined "the birch limit" 955 - 66, 34 - 2.7 - 2 to lie at a maximum height of 2890 Norw. feet on the 945 - 40 - 2.0 - 2 E-facing slope of Haftorsstoten. At the same time he 935 - 40, 27 - 2.5 - 2 determined the altitude of certain nearby points in the 925 - 27 - 4.0 - 20 terrain, the modern heights of which above sea-level 915 - 72 - 5.0 - 20 are precisely known. This enables a correction of the above-mentioned "birch limit" value to be made, to ea Documentation 900 m a. s. 1. The latter value is therefore a minimum TL-Smith (342):923 value for the tree-limit (cf. Nordhagen 1928). Past tree-limit Degree of change Past tree-limit Degree of change 925 Apparent displacement: + 30 905 Apparent displacement: +40 Significant displacement: + 20 Significantdis placement: + 30

171 Gruvsjohojden SSW (69 563 13 098) 168 Haftorsstoten S (69 648 13 127) Present-day altitudinal limits (1973) Present-day altitudinal limits ( 1975) FL: 920, clumps of trees FL: 925 , clumps of trees (distinct FL on the MSL: 905, one stem Norwegian side of the border) TL: 945, a 3 m high stem MSL: 930, a few stems Age-determination transect TL: 1030, a clump of 2.5 m high stems 905 - 69 - 5.0 - 20 Age-determination transect Documentation 1030 - 31 - 2.5 - 2 TL-Smith (343):906 1010 - 37 - 4.0 - 2 980 - 35, 34, 25 - 3.5 - 2 Past tree-limit Degree of change 960 - 31, 31, 29, 26, 20 - 3.5 - 2 905 Apparent displacement: +40 930 - 84 - 4.0 - 20 Significant displacement: + 30 Documentation TL-Smith (340):955 172 Gronfjallet w ( 69 579 13 148) Past tree-limit Degree of change 955 Apparent displacement: + 75 Present-day altitudinal limits ( 1972) Significant displacement: +65 FL: 950, clumps of trees MSL: 900, a fe w stems TL: 975, a small number of 2.5 - 3 m high stems SL: 990, a 1.8 m high stem; 1000, a 0.75 m high 169 Gronvalen NNE (69 63 1 13 146) shrub Present-day altitudinal limitsI (1975) Age-determination transect FL: 930, clumps of trees 900 - 89 - 5.5 - 20 MSL: 915, a few stems TL : 960, a small number of 2.5 - 3 m high stems Documentation TL-Smith (344):909 Age-determination transect 960 - 38, 37, 35, 28 - 3.0 - 2 Past tree-limit Degree of change 930 - 53, 49, 45 - 5.0 - 2 920 Apparent displacement: +55 915 - 89 - 6.0 - 20 Significant displacement: +45

Acta phytogeogr. suec. 65 70 Le ifKullm an

173 Gronfjallet N ( 69 588 13 152) MSL: 925, a small number of stems 975 , 3.2 Present-day altitudinal limits ( 1972) TL: a m high stem FL: 925, wedge Age-determination transect MSL: 935, one stem 97 5 - 44 - 3. 3 - 2 TL: 960, a small number of 2.5 - 3 m high stems 960 - 33 - 2.3 - 2 955 - 34, 34 - 2.8 - 2 Age-determination transect 945 - 52, 51, 48 - 3.5 - 2 935 - 64 - 4.0 - 20 925 - 76 - 4.0 - 20 Documentation Documentation TL-Smith (345):945. Mr Paulus Middagsfjall, Gronda­ TL-Smith (347):923 len, states that the birches now grow higher-up than they did when he was young (about 60 years ago) . Past tree-limit Degree of change 925 Apparent displacement: +50 Past tree-limit Degree of change Significant displacement: +40 945 Apparent displacement: + 15 Significant displacement: + 5 176 Osj ovalen E (69 585 13 209) Present-day altitudinal limits (1972) 174 Klasberget N (69 602 13 174) FL: 970, wedge Present-day altitudinal limits ( 1975) MSL: 930, one stem FL: 920, small clumps of trees , TL: 97 5, a small number of 3-3.5 m high stems MSL: 930, a few stems Age-determination transect TL: 960, a small number of 2.5 m high stems 930 - 69 - 4.5 - 20 Age-determination transect Documentation 960 - 39 - 2.5 - 2 TL-Smith (348):941 940 - 39, 32, 32 - 3.5 - 2 930 - 105, 85, 51 - 4.0 - 20 Past tree-limit Degree of change 920 - I OJ - 4. 0 - 20 940 Apparent displacement: + 35 Significantdispla cement : +25 Documentation TL-Smith (346):932 177 Osj okhippen S (69 556 13 225) Past tree-limit Degree of change Present-day altitudinal limits ( 1974) 930 Apparent displacement: +30 FL: 990, even limit Significant displacement: + 20 MSL: 950 , one stem TL: 1000 , two 2.5 m high stems 175 Klasberget NW (69 597 13 172) Age-determination transect Present-day altitudina/ limits (1975) 1000 - 33 - 2.5 - 2 FL: 955, lobes and clumps of trees 990 -49, 46 , 40, 37, 37 -4.0-2

Fig. 50. All the birch trees visi­ ble as darker spots in the exten­ sive willow thickets (Salix spp.), became established after 1915/ 16 and represent an upward dis­ placement of thetr ee-limit by 25 m. The birches are watered for a large part of the summer by meltwater from the snow-field above . In all probability this meltwater supply was appreci­ ably greater in 1915/16 and at that time prevented any effec­ tive birch colonisation within the tract of ground lying be­ tween the past and the present­ day tree-limits here at locality 176. Photo: July 12, 1972.

Acta phytogeogr. suec. 65 Change and stability of birch tree-limit in the Scandes 71

Fig 51. A regular front of birches forming the forest-limit (990 m a.s.l.) at locality 177. The birches became established here at the end of the 1920's. The lighter-coloured vegetation, im­ mediately in front of the birches, is a dwarf-shrub heath dominated by Vaccinium myrtil­ lus, Betula nana, together with herbaceous species, while Nar­ dus stricta grass heath is domi­ nant still higher up. The vegeta­ tion thus shows a clear zona­ tion, which depends on differ­ ences in the time of the snow­ melt. It is therefore a resonable surmise that birch establishment here (i.e. the rise in the tree-limit) is related to an up­ ward shift of all these zones, due to an earlier disappearance of the snow cover. Photo: June 16, 1973 .

Fig. 52. The arrow marks the position of the birch front at lo­ cality 177 (see Fig. 51). This lo­ cality is situated within a pro­ nounced snow accumulation area. The climatic amelioration during the present century has almost certainly led to a more rapid disappearance of the snow-fields , a circumstance which completely altered the ecological conditions and there­ by the local vegetational zona­ tion. Photo: June 16, 1973 .

955 - 56, 39, 37, 37, 36, 27-5.0 -2 178 Osjoklappen ssw (69 555 13 214) 950-68-5.0 -20 Present-day altitudinal limits ( 1974) 920 - 91 - 6.0 - 20 FL: 1010, clumps of trees Documentation MSL: lacking on and above the valley floor, ea Smith must almost certainly have viewed this particu­ 965 m a. s. I. lar hill-slope from quite close quarters in 1915I 16. Had TL: 1025 , two 2.2 m high stems the tree-limit thereabouts exceeded ea 950 m a. s.l. he Age-determination transect would undoubtedly have made an aneroid reading 1025 - 31 - 2.2 - I here. As it stands the value cited is highly probable, 1015 - 36, 32, 28, 27 - 3.0 - 2 judging from the tree-limit altitudes for all the nearby, 1 000 - 41 ' 3 7' 3 3 - 3 . 5 - 2 comparable, localities. Documentation Past tree-limit Degree of change The fact that at the nearby locality 177, the tree-limit 950 Apparent displacement: +50 obviously lay at 950 m in about 1915, increases the Significant displacement: +40 probability that the tree-limit at the actual locality con-

Acta phytogeogr. suec. 65 72 LeifKullman cerned was not much higher at the same time. Furthermore, Smith's isohypsometric map (Karta 1) shows that there was no birch forest growing on this hillslope, i.e. that the present-day tree-limit is probably considerably higher than it was in 19I5. Past tree-limit Degree of change <965 Apparent displacement: +60 Significantdisplace ment: +60

I79 Ramundberget N (69 574 13 237) Present-day altitudinal limits (1977) FL: 920, clumps of trees TL: 975, a small number of 3-3.5 m high stems Age-determination transect 975 - 45, 44, 30 - 3.2 - 2 960 - 30, 26 - 3.0 - 2 Fig. 53. A clump of birches, which became established 955 - 41 - 5.0 - 20 long after 19I5/I6, is visible just on the edge of the 950 - 4I - 4.0 - 20 large and deep snow-field, at the time of birch leafing. Documentation Nowadays birch would be virtually unable to colonise TL-Smith (349):933 this particular site by seed, because of the effects of the increased supply of snow meltwater after ea I950. Past tree-limit Degree of change Well-established birches, however, are still quite cap­ 935 Apparent displacement: +40 able of holding out fairly well, despite the changed Significantdisplacement: + 35 environment, because of their stem pliability, although with increasing age they become broken down one­ 180 Ramundberget S (69 544 13 244) by-one by the weight of the snow cover. The vegeta­ tion growing in front of the snow-field is a willow Present-day altitudinal limits (1975) thicket (Salix spp.) almost 1 m high. Locality 181, 950 FL: 980, even limit m a.s.l. Photo: June 16, 1973 . MSL: 980, one stem TL: 1000, a 2.3 m high stem Age-determination transect Past tree-limit Degree of change 1000-31-2 .3 -2 905 Apparent displacement: +55 990 -45, 37, 3I -2.5 -2 Significant displacement: +55 980 -49, 48, 42, 33, 24 - 4.5 - 2 980 - 66 - 5.0 - 20 182 Skenorsfjallet S (69 505 13 199) 960 - 24 - 5. 0 - 20 Present-day altitudinal limits (1975) 945 - 57 - 6.0 - 20 FL: 975, small clumps of trees 930 - 102 - 7.0 - 20 MSL: 975, one stem 920 - 54 - 4.5 - 20 TL: 1075, a 2 m high stem Documentation Age-determination transect TL-Smith (350):9I2 I 07 5 - 3 2 - 2. 0 - 1 Past tree-limit Degree of change 1050 - 35 - 2.3 - 1 980 Apparent displacement: +20 10I5 - 45, 35, 33, 33, 23 - 2.5 - 1 Significantdisplacement: + 20 975 - 64 - 4.0 - 20 Documentation 181 Kariknallarna E (69 5I2 13" 235) Sernander (1905) mentions that a tree-limit exists on this hillslope, and in a later paper (19IO) maintains that Present-day altitudinal limits (1975) the plateau lying at the foot of the mountain is situated FL: 950, even limit in the uppermost birch forest region. This is probably MSL: 905 , a few stems to be interpreted as meaning that small, discrete, TL: 960, a small number of 2.5 - 3 m high stems stands of birch, as well as occasional solitary trees, SL: 1005, a 1.5 m high stem were growing here up to an altitude of 970--980 m at the Age-determination transect beginning of the present century. 905 - 87 - 5.0 . 20 Past tree-limit Degree of change Documentation 975 Apparent displacement: + IOO TL-Smith (351):900 Significant displacement: +I00

Acta phytogeogr. suec. 65 Change and stability of birch tree-limit in the Scandes 73

183 Stor-Skarven ESE (69 479 13 238) 1015 - 22, 16 - 4.0 - 20 1010 - 88, 84, 80, 58, 29 - 5.0 - 2 Present-day altitudinal limits (1973) 1000 - 27 - 5.0 - 20 FL: 965, clumps of trees 990 - 104, 75, 70, 64 , 53 - 5.0 - 2 MSL: 900, one stem TL: 970, several 3 m high stems Documentation TL-Smith (353):949. That the tree-limit lay higher-up Age-determination transect than the altitude given by Smith, can not be entirely 970 - 45 - 3.0 - 2 ruled out, although at most it can have been at 1010 m 900 - 68 - 5.5 - 20 (cf. Kullman 1976a, p. 122). Documentation Henning (1887) has given a fairly detailed account of TL-Smith (352):896 both the flora and the vegetation cover of this particu­ Past tree-limit Degree of change lar hillslope. Nowhere does he give so much as a hint 900 Apparent displacement: + 70 that birch was growing anywhere hereabouts at that Significantdis placement: + 70 time (cf. Kullman op. cit.). Past tree-limit Degree of change 950 Apparent displacement: + 115 184 Lill-Skarven SE (69 448 13 234) Significant displacement: + 110 Present-day altitudinal Limits (1974) FL: 1040, clumps of trees 185 Lill-Skarven SW (69 443 13 223) MSL: 950, very old, but age-determination impos- sible because of damage from fu ngal attack Present-day altitudinal Limits (1972) FL: 960, clumps of trees TL: 1065, a 2.5 m high stem M�L: 930, one stem SL: 1075, 0.3 - 0.7 m high shrubs TL: 1010, a small number of 2.5 - 3 m high stems Age-determination transect Age-determination transect 1065 - 32 - 2.5 - 2 . 1010 - 39, 37 - 2.7 - 2 1060 - 32 - 2.5 - 2 985 - 40, 38, 37 - 3.0 - 2 1040 - 60, 50, 49, 37, 31 - 4.0 - 2 955 -50, 36, 34, 31 - 5.0-2 1030 - 35 - 4.0 - 2 930 - 74 - 5.0 - 20 1030 - 19 - 4.0 - 20 1025 -68, 56, 34, 31, 30 -4.0-2 Documentation 1015 - 39, 33 - 4.0 - 3 TL-Smith (358):945

Fig. 54. The photograph (locality 186) was taken during a storm with accompanying driving snow (no snow fall), on the westward side of a ridge (915 m a.s.l.). The local birch tree-limit coincides with the point of change-over from snow accumulation to snow deflation. More or less similar snow deflation areas as the one shown in the photograph, immediately above the tree-limit, are characteristic of most of the localities in the investigated area at which the tree-limit was found to have remained unchanged since 1915/16. Photo: April 20, 1974 .

Acta phytogeogr. suec. 65 74 LeifKullman

Fig. 55. Tree-limit (1010 m a.s.l.) at locality 189. The Fig. 56. The same tree as shown in Fig. 55. The shoot birch probably has a stem base age which scarcely system has obviously increased somewhat during the exceeds 30 years. Photo: June 26, 1970. period 1970-1977. Photo: July 14, 1977.

Past tree-limit Degree of change Past tree-limit Degree of change 945 Apparent displacement: +65 935 Apparent displacement: 0 Significant displacement: +55 Significant displacement: 0

186 Storvallsruet W (69 414 13 253) 188 Hamrafjallet E (69 449 13 209) Present-day altitudinal limits (1972) FL: 895, clumps of trees Present-day altitudinal limits ( 1977) MSL: 915, one stem FL: 935, sparse clumps of trees TL: 915, a fe w 2-4.5 m high stems MSL: absent, both on and above the valley floor (alti- tude ea 920 m) Age-determination transect TL: 975, a small number of 2-2.5 m high birches 915 - 68 - 4.5 - 20 Age-determination transect Documentation 975 - 36, 30 - 2.5 - 2 TL-Smith (355):914 960 - 41 - 3 . 0 - 2 Past tree-limit Degree of change Doe umentation 915 Apparent displacement: 0 Birger (1908, p. 112) gives the "birch limit" as 93 1 m. Significantdis placement: 0 Smith's statement "Hamrafjall 6 ... 900", probably applies to the SE-facing hillslope, since on the E-facing 187 Lillvalen S (69 429 13 227) proper a value of 900 m is impossible. Present-day altitudinal limits ( 1972) Past tree-limit Degree of change FL: 930, clumps of trees 930 Apparent displacement: +45 MSL: 935, one stem Significant displacement: +40 TL: 935, a few 2 m high stems Age-determination transect 935 - 61 - 4.0 - 20 189 Hamrafj all SE (69 446 13 207) Documentation Present-day altitudinal limits ( 1977) TL-Smith (357):927 FL: 990, dense clumps of trees

Acta phytogeogr. suec. 65 Change and stability of birch tree-limit in the Scandes 75

Fig. 57. The tree-limit (1010 m a.s.l.) at locality 189. Fig. 58. The same tree as in Fig. 57. The left-hand stem The stems are somewhat older than those shown in has become very much more bent over since 1970, but Fig. 55. The surrounding vegetation is bilberry heath is not yet completely dead. The right-hand stem has (Vaccinium myrtillus) with scattered shrubs of willow produced a much greater mass of foliage during the (Salix spp.) and juniper (Juniperus communis). Photo: same period. Photo: July 14, 1977. June 26, 1970.

MSL: 950, a few stems Documentation TL: 1010, a few 2.5 m high birches For reasons mentioned under locality 189, the tree-li­ Age-determination transect mit lay above 93 1 m at the beginning of the present 955 - 59 - 6.0 - 20 century. (1908 : 8, 20) 950 - 62 - 6.0 - 20 Birger Tafl . Fig. reproduces a photo­ graph in which this hillslope, although not appearing Documentation absolutely distinct, is clear enough to make it obvious TL-Smith (359):900 . See locality 188. that the belt of birch forest present between ea 920 and Birger (1908 , p. 1 12) states that the lowest value for 990 m today, was entirely absent at the beginning of the the "birch limit" on Hamrafjalletis fo und on the E-fac­ present century. ing slope , viz. at 93 1 m. This value thus represents the . Past tree-limit Degree of change minimum altitude for the tree-limit on the slope in 940 Apparent displacement: + 70 question . Significant displacement: + 70 Past tree-limit Degree of change 955 Apparent displacement: +55 Significant displacement: +55 191 Hamrafjallet SSE (69 445 13 195) Present-day altitudinal limits ( 1977) 190 Hamrafjallet S (69 446 13 203) FL: 960, small clumps of trees Present-day altitudinal limits ( 1977) MSL: not above 925 m FL: 990, clumps of trees TL: 1060, a small number of 2-2.5 m high stems MSL: 940, one stem Age-determination transect TL: 1010, a few 2-2.5 m high birches 1060 - 28 - 2.0 - 2 SL: 1015, a 1.5 m high shrub 1055 - 29, 23, 21 - 2.5 - 1 Age-determination transect 1010 - 42 , 40, 39, 35, 32 - 2.7 - 1 990-56, 54 , 53, 51, 38-3.5-2 965 - 30 - 4.5 - 20 965 - 58, 46, 43 , 42 , 32 - 4.0 - 2 960-43, 37, 35, 29, 29 -3.5-2 950 - 55, 53 , 50, 49, 36 - 7.0-2 960 - 33 - 5.5 - 20 940 - 77 - 6.0 - 20 935 - 34 - 9.0 - 20 930 - 55, 48 , 40 - 7.0 - 2 930 - 48 - 6.0 - 13 930 - 81 - 5.0 - 20 925 - 48 - 7.0 - 20

Acta phytogeogr. suec. 65 76 LeifKullm an

Documentation TL-Smith (361):968 (cf. Kullman 1976 a, p. 120). Sernander (1905) estimated the "rational tree-limit" to lie at 890 m, at the same time as the height of the summit plateau was determined as being 1030 m. The latter value is appreciably too low. It is impossible, however, to decide from his account to just what parti­ cular point on the plateau that value refers . Sernan­ der's report is thus of little use in the present connec­ tion. Past tree-limit Degree of change 970 Apparent displacement: +90 Significant displacement: +80

192 Hamrafjallet SSW (69 442 13 185) Present-day altitudinal limits (1977) FL: 1050, clumps of trees MSL: 975 , several stems TL: 1085, a multi-stemmed individual tree, of maximum height 2.2 m

Fig. 59. In the upper part of the birch forest belt the Age-determination transect most important mortality factor for stems which have 1 085 - 3 5' 25 - 2. 2 - 2 attained a certain thickness and length is simply me­ 1080 - 38 - 1.9-2 chanical injury from the weight of accumulated snow. 1070 - 39 - 2.2 - 2 Younger, more slender, stems are better able to with­ 1065 - 35, 32, 30, 30 - 2.7 - 2 stand snow pressure, since they are still pliable enough 1050-41, 41 , 34, 30-3.0-2 to bend under its weight without breaking. Locality 1020 - 26 - 4. 0 - 20 191, 960 m a.s.l. Photo: August 2, 1976. 1005 -52-5.0 - 20 995 - 48 - 5. 0 - 20 975 - 86, 78 - 5.5 - 20 Documentation Henning (1887) determined the "birch's upper limit" to be at 1024 m (corrected value). Birger (1908) found the "highest-lying outposts of birch" at 1030 m. For further discussion concerning

Fig. 60. These birches grow 20 m below the tree-limit at locality 192. Their development has been carefully followed by tak­ ing photographs at yearly inter­ vals, always from the same viewpoint. The long-lasting snow cover and fertile soil con­ ditions here give rise !P a vege­ tation dominated by a mixture of grasses and herbs, together with willow thickets (Salix spp.). The arrow indicates a birch stem permanently dama­ ged by the weight of the snow cover. Photo: July 6, 1972.

Acta phytogeogr. suec. 65 Change and stability of birch tree-limit in the Scandes 77

Fig. 61. The same view as in Fig. 60. Apart from the fact that the birch stem marked by the arrow in Fig. 60 has died off completely and is hidden by the surrounding vegetation, no ob­ vious changes have occurred here in 1972-1977 . Photo: July 10, 1977.

Fig. 62 . The same view as in Figs. 60 and 61. These birches which all have stem base ages not exceeding 55 years, grow in an environment characterised by a deep snow cover and a late snow-melt. Their establishment here has obviously been de­ pendent upon an amelioration of these particular habitat factors since 1915/16. Photo: May 22, 1977 .

A eta phytogeogr. suec. 65 78 Le ifKull man

these two particular values see my earlier paper (Kull Age-determination transect man 1976a, p. 119) 980 - 64 ' 3 8' 34 - 2.7 - 2 Past tree-limit Degree of change 975 - 26 - 2.0 - 2 1030 Apparent displacement: +55 945 -64, 49, 41, 40, 39 -4.0-2 925 - 65 - 4.5 - 20 Significant displacement: +55 Documentation 193 Hamrafjallet N (69 455 13 190) TL-Smith (367):938. Present-day altitudinal limits ( 1977) Sernander (1898, p. 329), in 1895 or 1896 , determined the altitude of the "tree-limit" to be 870 m, while at the FL: 955, wedge MSL: 955, a small number of stems same time determining the altitude of the nearby lake TL: 970, a multi-stemmed birch, 3.5 m high Malmagen as 755 m, a value which is 26,5 m too low. The altitude of Sernander's, otherwise undefined, Age-determination transect tree-limit thus needs correcting to 900 m. 970 - 69 - 3.5 - 2 965 - 42 - 5.0 - 20 Past tree-limit Degree of change 955 - 64 - 5.5 - 20 940 Apparent displacement: +40 Significant displacement: + 35 Documentation TL-Smith (362):940 197 Storklappen NE (69 429 13 167) Past tree-limit Degree of change 955 Apparent displacement: + 15 Present-day altitudinal limits ( 1974) Significantdi splacement: + 15 FL: 900, clumps of trees MSL: 900, a small number of stems TL: 965, a multi-stemmed birch, 2.5 m in height 194 Malmagsvalen SW (69 507 13 144) Age-determination transect Present-day altitudinal limits (1974) 965 - 38 - 2.5 - 2 FL: 980, clumps of trees 950 - 53, 39, 27 - 3.5 - 2 MSL: 975, a few stems 925-41, 39, 38, 33, 29-4.0 -2 TL: 985, several 2-2.5 m high stems 900 - 73 ' 64 - 5. 0 - 20 Age-determination transect Documentation 985 - 69, 63, 60, 48, 38 - 2.5 - 2 TL-Smith (368):947 975 - 85 - 5.0 - 20 Past tree-limit Degree of change Documentation 945 Apparent displacement: + 20 TL-Smith (364):960 Significant displacement: + 20 Past tree-limit Degree of change 975 Apparent displacement: + 10 198 Svanaklappen SSW (69 398 13 180) Significant displacement: + 10 Present-day altitudinal limits (1974) FL: 975 , clumps of trees 195 Rutfjallet (Lillruten) NNE (69 498 13 099) MSL: 940, a few stems TL: 975, a small number of 4-4.5 m high stems Present-day altitudinal limits ( 1972) FL: 905, clumps of trees Age-determination transect MSL: 930, one stem 975 - 62, 53, 47, 29 - 4.5 - 2 TL: 965, a small number of 2-2.5 m high stems 970 - 28 - 4.0 - 2 940 - 79' 62 - 5.0 - 20 Age-determination transect 930 - 75 - 4.5 - 20 Documentation TL-Smith (370):942 Documentation TL-Smith (366): 944 Past tree-limit Degree of change 940 Apparent displacement: + 35 Past tree-limit Degree of change Significant displacement: + 30 945 Apparent displacement: + 20 Significant displacement: + 10 199 Svanaklappen E (69 398 13 185) 196 Grastoten NE (69 465 13 129) Present-day altitudinal limits ( 1974) Present-day altitudinal limits ( 1974) FL: 900, clumps of trees FL: 935, clumps of trees MSL: 915, one stem MSL: 925, one stem TL: 945 , a small number of 2-3.5 m high birches TL: 980, a small number of 2.5 - 3 m high stems SL: 950, a l.7 m high stem

Acta phytogeogr. suec. 65 Change and stability of birch tree-limit in the Scandes 79

Age-determination transect Documentation 915 - 70 - 5.0 - 20 TL-Smith (373):980

Documentation Past tree-limit Degree of change TL-Smith (371):900 990 Apparent displacement: + 10 Significant displacement: + 10 Past tree-limit Degree of change 915 Apparent displacement: + 30 203 Rodfjallet s (69 336 13 213) Significantdispla cement: + 30 Present-day altitudinal limits ( 1972) 200 SvanakHippen N (69 402 13 184) FL: 875, clumps of trees MSL: 950, a few stems Present-day altitudinal limits ( 1972) TL: 950, a small clump of 4-5 m high stems FL: 900, clumps of trees MSL: 900, a few stems Age-determination transect TL: 960, a small number of 2-2.5 m high stems 950 - 93 - 5.0 - 20 Age-determination transect Documentation 900 - 89, 62 - 5.5 - 20 Lacking Documentation Past tree-limit Degree of change TL-Smith (369):915 950 Apparent displacement: 0 Significant displacement: 0 Past tree-limit Degree of change 915 Apparent displacement: +45 204 Rodfjallet E (69 340 13 247) Significant displacement: +40 Present-day altitudinal limits ( 1972) 201 Rodfjallet NNE (69 369 13 207) FL: 845 , small clumps of trees MSL: 925, two stems Present-day altitudinal limits ( 1974) TL: 925, a small number of 3 - 4 m high stems FL: 935, clumps of trees MSL: 980, one stem Age-determination transect TL: 995 , a 2.5 m high stem 925 - 62 - 4.0 - 20 870 - 69 - 4.5 - 20 Age-determination transect 995 - 41 - 2.4 - 2 Documentation 985 -46, 41, 33-2.5-2 Lacking 980-87-3.5 -30 Past tree-limit Degree of change 965 - 63 - 3.5 - 20 925 Apparent displacement: 0 960 - 64 - 4.0 - 20 Significant displacement: 0 Documentation TL-Smith (372):987. 205 Brattriet S (69 280 13 234) Henning (1887) determined the "upper birch limit" Present-day altitudinal limits (1975) to be 845 m, at the same time as he determined the altitude of the highest point of the mountain as 1100 m. FL: L015, clumps of trees The later value is 145 m too low, compared to the MSL: 975 , one stem modern value, wherefore this "upper birch limit" has a TL: 1115, two 2.1 m high stems corrected value of 990 m. Age-determination transect 1115 - 26 - 2. 1 - Past tree-limit Degree of change I 1075 - 28, 25 - 2.5 - 1 990 Apparent displacement: +5 Significant displacement: 0 1035 - 41 - 3.0 - 2 1015 -73, 62 , 41, 32, 32 -4.0-2 975 - 98 - 4.0 - 20 202 Rodfjallet s (69 339 n 241) Documentation Present-day altitudinal limits (1974) TL-Smith (378):972 FL: 985 , wedge MSL: 990, one stem Past tree-limit Degree of change TL: 1000 , two, 2.5 m high stems 975 Apparent displacement: + 140 Significant displacement: + 140 Age-determination transect 1000 - 31 - 2.5 - 2 206 Sanfjallet s (69 08 1 13 82 1) 990 - 63 - 3.5 - 20 985-45-3.0 -2 Present-day altitudinal limits (1973) 980 - 85 - 4. 5 - 2 MSL: 1025, a single live stem, together with re­ 97 5 - 60 - 4.0 - 2 mains of former stems which were at least

Acta phytogeogr. suec. 65 80 Le ifKullman

Fig. 64. This birch forms the tree-limit (1025 m a.s.l.) at locality 206 . The age of the thickest stem, estimated 2 m above the ground, is 61 years. In other words, the Fig. 63 . The birch stems seen in the photo (locality tree-limit here has remained unchanged since 1915/16. 205) represent the highest-known present-day In the immediate vicinity of the birch the vegetation is tree-limit (TL) in the whole of Sweden (1115 m a.s.l.). bilberry heath (Vaccinium myrtillus), while Cladonia The stem base age of the left-hand one is 26 years. The alpestris is dominant fu rther away from the tree. vegetation is dominated by Vaccinium myrtillus and Photo : August 15, 1973 . Betula nana. Photo: July 21, 1975.

2 m in height and were fairly old when they Documentation died The tree-limit would be expected to have lain at ap­ TL: 1025, multi-stemmed 3.5 m high birch proximately the same altitude (1025 m) as that of the Age-determination transect previous locality, because the two localities lie quite close together and the topography and edaphic condi­ I 025 - 61 - 3.5 - 20 tions at both sites are similar. Documentation Past tree-limit Degree of change Lacking 1025 Apparent displacement: +95 Past tree-Limit Degree of change Significant displacement: +95 1025 Apparent displacement: 0 Significant displacement: 0 208 Grasidan SSE (69 086 13 788) 207 Korpflyet SSE (69 062 13 720) Present-day altitudinal limits ( 1974) Present-day altitudinal limits ( 1974) FL: 940, clumps of trees FL: 1050, small clumps of trees MSL: 970, a mouldering stump of a very old MSL: 960, a few stems arborescent birch TL: 1110, a multi-stemmed 2 high birch TL: 970, a small number of multi-stemmed m birches, maximum height 4 m Age-determination transect SL: 985, a few 1 - 1.5 m high shrubs; 1100 - 34 - 2.0 - 2 1010, a 0.5 m high shrub 1110-34 - 1.5 - 2 1 100 - 46 - 2. 2 - 2 Age-determination transect 1090 - 23 - 2.0 - 2 970 - 66, 64 - 4.0 - 2 1035 -68, 41, 36, 32 -3.0-2 970 - 58 - 4.0 - 13 1015 -59-2.7 - 10 965 - 36 - 2.3 - 2 985 -57, 49 , 48, 41 -3.0 -2 960 - 99 - 3.0 - 2 960-73-3.5 -20 960-82-3.5-20 950-65-3. 5-20 955 - 11 - 2.8 - 2

Acta phytogeogr. suec. 65 Change and stability of birch tree-limit in the Scandes 81

Fig. 65. In this type of environment, with virtually no supply of snow meltwater during the entire vegetative Fig. 66. At locality 210, which has a rather shallow season, neither at present nor at all likely in the past as snow cover and becomes snow-free early on in the well, the tree-limit has remained stable. The birch in spring, the open ground above the tree-limit (930 m the foreground has grown in height from 0.2 to 2.8 m a.s.l.) has never offered the pre-conditions for any since the mid 1960's, an amazingly rapid growth rate upward displacement of the tree-limit. The stem age of for a birch growing very close to the tree-limit. This the tree, cored 2 m above ground-level, was 70 years. indicates that the tree-limit here is not directly climati­ The dominant vegetation here is bilberry heath (Vacci­ cally conditioned. Locality 208, 995 m a.s.l. Photo: nium myrtillus). Photo: July 19, 1974. August 16, 1974.

Documentation Past tree-limit Degree of change Lacking 965 Apparent displacement: + 15 Past tree-limit Degree of change Significant displacement: + 15 970 Apparent displacement: 0 Significant displacement: 0 210 6stra Barfredhagna SSW (69 876 13 219) Present-day altitudinal limits (1975) 209 Jakobshojden SW (68 94 1 13 178) FL: 870, stands of very sparse fo rest MSL: 930, one stem Present-day altitudinal limits (1975) TL: 930, a small number of 2.5 - 3 m high stems FL: 955 , lobes and clumps of trees MSL: 955 , a few stems Age-de termination transect TL: 980, a small number of 3 m high stems 930 - 70 - 2.8 - 20 925 - 72 - 4. 0 - 20 Age-determination transect 920 - 54 - 3. 0 - 13 980 - 61 - 3 . 0 - 2 920 - 50, 47 - 2.5 - 2 97 5 - 40 - 3.0 - 2 910 - 71 - 3.5 - 20 965. -33-3.0 -2 910 - 83 - 2.5 - 2 960 - 49 - 3.0 - 2 890 - 141 - 4. 0 - 13 955 - 64-3.5 - 2 945 - 76 - 3.5 - 20 Documentation Samuelsson ( 1917, p. 120) has given a summarised Documentation description ?f the tree-growth on the S-facing slope of TL-Smith (458):957. This value is a personal communi­ . cation to Smith from Gunnar Samuelsson. It is quite this mountam, from which it is clear that the conditions at that time very much resembled the situation at the clear that Samuelsson did not consider multi-stemmed present-day. birches 2 m in height as being trees (cf. Samuelsson 1917, p. 96) . It is therefore highly probable that birches Past tree-limit Degree of change of the fo rmer type were present at an altitude some­ 930 Apparent displacement: 0 what above 957 m (e.g. 965 m). Significant displacement: 0

Acta phytogeogr. suec. 65 82 LeifKullm an

211 Molnet SSE (68 771 13 460) Present-day altitudinal limits ( 1975) FL : 1050, clumps of trees MSL: 975, a few stems TL: 1070, a multi-stemmed, 2.4 m high birch Age-determination transect 1070 - 19 - 2.1 - 2 1060 - 49 - 2.0 - 2

1025 - 64 - 2.0 - 2 1005 - 65, 64 , 52, 39, 22 - 2.5 - 2 990 - 64 - 3.0 - 2 980 - 60 , 46 - 4.0 - 2 975 - 72 - 4.0 - 20 Documentation Samuelsson (1917, p. 95) states that the forest-limit on this hillslope was as high as that for locality 212, i.e. 995 m, and that above this altitude there was a belt of birch shrub. A comparison of Samuelsson's Fig. 4 (op. cit.) and present-day conditions (see Kullman 1976b, Fig. 67 . The relatively flat terrain at and above the Fig. 3) reveals that the local boundaries between tree-limit (900 m a.s.l.) at locality 213 has almost cer­ clumps of trees and boulderfield have remained rela­ tainly 'at all times' retained a relatively shallow snow tively constant since 1912. It is highly probable that cover and has become snow-free again early on in the stunted birch-forest, which Samuelsson would almost spring. A surplus of snow was quite certainly not a certainly have classified as birch shrub (cf. locality limiting factor which prevented higher colonisation by 209), in 1912 grew as high up as the level of the pre­ the birch at the beginning of the present century. Thus, sent-day forest-limit, i.e. 1050 m a. s. I. In addition, the climatic amelioration, here and at similar localities Samuelsson maintains that scattered solitary birches, was unable to affect the actual position of the birch which from all accounts could have measured 2 m in· tree-limit, since the only environmental change in­ height, grew well above the altitude of the uppermost duced was even less favourable to birch colonisation, birch stands on the E- and S-facing slopes of Molnet. viz. a decreased supply of meltwater, leading to in­ creased dryness of the soil in summer, especially dur­ Past tree-limit Degree of change ing the unique succession of abnormally warm sum­ 1075 Apparent displacement: 0 mers during the 1930's. Photo: July 21, 1974. Significant displacement: 0

212 Nipfjallet s (68 74 1 13 429)

Present-day altitudinal limits ( 1975) Past tree-limit Degree of change FL: 1025, clumps of trees 1000 Apparent displacement: + 25 MSL: 1000, mouldering remains of an Significant displacement: +25 arborescent, very old birch TL: 1025, a small number of 2-2.5 m high stems 213 Stadjan WSW (68 717 13 455) Age-determination transect Present-day altitudinal limits ( 1974) 1025 - 48, 45, 40, 28, 24, 20 - 2.4 - 2 FL: 860, even limit 1010 - 51, 28 - 2.5 - 2 MSL: 900 , mouldering remains of a fairly coarsely- 990-74, 61,44, 37, 34-3.0 -2 dimensioned stem, over 2 m in length 990 - 33 - 2.8 - 20 TL: 900 , a 3 m high stem 970 - 39, 34, 31 - 2.5 - 2 Age-determination transect 965 - 64, 59 - 4.5 - 20 900 - 65 - 3. 0 - 2 955 - 43, 43, 32, 27 - 3.5 - 20 895 - 64 - 3.8 - 2 Documentation Documentation Samuelsson (1917, p. 95) mentions the presence of Lacking birch forest, composed of tree-sized birches , at 955 m. A belt of birch scrub was present higher up, the stems Past tree-limit Degree of change of which may have just exceeded 2 m in height (cf. 900 Apparent displacement: 0 locality 209). Significant displacement: 0

Acta phytogeogr. suec. 65 Change and stability of birch tree-Limit in the Scandes 83

214 Stadjan SW (68 702 13 459) Age-determination transect 900 - 44 , 29, 18 - 3.0 - 20 Present-day altitudinal Limits ( 1974) 890 - 79 - 5. 0 - 20 FL: 895 , wedge MSL: 890, a few number of stems Documentation TL: 905 , a small number of 2.5 m high stems Samuelsson (19 17) gives the altitude of the fo rest-limit SL: 920, mouldering remains of two recently dead as 900 m. stems, which were at least 2 m in height and Past tree-Limit Degree of change 25-30 years old 900 Apparent displacement: + 5 A few still living, 2 dm high basal shoots Significant displacement: 0

Acta phytogeogr. suec. 65 Analysis of primary data

The relationship between the degree of displace­ Significant displacement and its relation to ment of the tree-limit and the effect of various geographical position environmental factors, which may be relevant in Out of the total of 213 localities at which the explaining such changes, has been investigated in dynamics of the tree-limit was investigated, a po­ an attempt to find the cause or causes. The re­ sitive Significant displacement was found to have sults are presented below. occurred at 160 (ea 75 %). At the remaining 53 The basic philosophy motivating such a treat­ localities (ea 25 %) the position of the tree-limit ment of the data has been: The greater the degree remained unchanged. In no case was an undisput­ of displacement of the tree-limit found to have able lowering of the tree-limit found to have ta­ taken place, the greater the probability that the ken place. The greatest upward shift of the tree­ prime operative factor causing the observed shift limit was 140 m (localities 102 and 205). can be ascertained from its close relationship The number of localities for each of the eight over the widest area to interlinked environmental displacement intervals is shown in Table 9. The factors. In other words, those investigated locali­ mean values (with standard deviation) for the alti­ ties at which the greatest and least degrees of tude of the tree-limit within the investigated area displacement are recorded ought to exhibit most as a whole in 1915/16 (PTL) and in 1975 (TL) are clearly the ecological characteristics which de­ shown in Table 10. termine, or control, the presence or absence of a The geographical distribution of the localities change in the tree-limit. with or without a positive value of Significant The analyses are intended to elucidate any displacement is clear from Figs. 2 and 3. quantitative differences in the operative factors in relation to different degrees of Significant dis­ placement. Table 9. The numbers of localities for which the recorded The statistical relationships have been mainly values for the altitudinal displacement of the tree-limit (1915/ investigated by calculating for each environmen­ 16-1975) fell within each of 8 classes of magnitude. tal factor, the percentual distribution of a small number of quantitative classes, within each of Tree-limit No. of displacement localities four different intervals with respect to the magni­ (m) tude of the Significant displacement. 0 53 The results are presented in the form of histo­ 5- 10 23 grams, in which each horizontal column (dis­ 15-20 26 placement interval) representing 100 %, is subdi­ 25-30 31 35-40 28 vided into the proportions represented by each of 45-60 24 the quantitative classes of a certain environment­ >60 28 al factor. This provides a graphic representation of the degree of the displacement of the tree-limit in relation to the quantitative expression of the re­ Table 10. Mean (x) and standard deviation (s.d.) for the alti­ tude of the tree-limit (m a. s. l.) in 1915/16 and 1975, respec­ spective environmental factor. tively, at all the 213 investigated localities taken together. The (present-day) estimated quantitative val­ ues for the environmental factors considered are Year s.d. X set out in Appendix I. 1915/1916 896.92 ±67.23 1975 930.92 ±69. 14

Acta phytogeogr. suec. 65 Change and stability of birch tree-limit in the Scandes 85

There are virtually no clearly marked regional Interval (m) differences distinguishable in the degree of dis- Tot al : 1 I 2 3 4 I n 2 3 placement of the tree-limit over most of the in- l; ]. , . , < vestigated area. The proportion of localities at .. . which no change was recorded is, however, defi- 0 2 3 4 n 53 ·- = I !I I ! I nitely greater in Dalarna and the southernmost ' ' ··- .. part of Harjedalen , compared to the remainder of . n: the investigated localities. It is also clear from the 5-20 1 2 3 4 49 r' I . locality descriptions and Figs. 2 and 3, that the \ \ \I degree of displacement of the tree-limit can differ - 0 . very markedly even between two neighbouring 25 4 1 2 3 ) 4 1 n=59 ':1 l ' localities (e.g. the following pairs of localities: 20, ' ' 21; 45 , 46; 61' 62 ; 103' 1 04 ; 144, 145). >40 1 2 l 3 14 I n:s2 0 50 100%

Continentality/ maritimity Fig. 68 . Percentual distributions of each of the 4 grades of local continentality-maritimity within each of The relative degree of local thermic continentali­ the 4 tree-limit displacement intervals and within the ty or maritimity has for a long time been consi­ material as a whole (Total). The climate classification dered to play a determining role in the absolute is as follows:- 1. Local maritime, in the vicinity of, and due to , the major depression in the Scandes mountain altitude of the tree-limit, when seen in a broader, chain at Storlien, which permits a ready penetration of regional, perspective (e.g. Brockmann-Jerosch oceanic air masses eastwards from the Norwegian Sea; 1919; Kilander 1965; Mork 1968, 1970) . Further­ - 2. Weakly local maritime, where the above-men­ more, it was shown earlier that the degree of tioned airmass penetration is locally weakened by iso­ recent climatic change differed between areas lated massifs , e.g. Snasahogama/BH1hammaren and Sylama; - 3. Intermediate local climate, intermediate with a continental resp. maritime character of the in type between 2 and 4; - 4. Local continental , condi­ regional climate. tioned by a relatively great distance from the Norwe­ There are therefore good grounds fQr consider­ gian Seacoupled with the presence of intervening topo­ ing whether or not the changes in the tree-limit, in graphic barriers. (n=number of localities) the different parts of the investigated area with a similar local climate, have also been similar with­ in the period studied. Unfortunately there are only a few meteorolo­ especially snow accumulation and rate of melt­ gical stations within the area which provide the ing, has also been considered. Nevertheless, it data necessary for forming a proper picture of the must be pointed out that the classification is ap­ differing climatic regimes present. proximate , although by and large giving some Each locality has been classified with regard to indication of the regional distribution of local cli­ climatic type, on a basis of available meteorologi­ mates. cal data (Table 1), Angstrom's (1974, Fig. 23) map The percentual distributions, within each of the of the extent of areas of local continentality or four displacement intervals and within the mate­ local maritimity in Sweden, and certain opinions rial as a whole, for the total numbers of localities about climatic differences between different parts belonging to each of the four local climate catego­ of the investigated area expressed in literature ries, are shown in Fig. 68. (Jalas 1950; Hintikka 1963 ; Kravtsova 1972). The result shows incontrovertibly that the When classifying the climate of each locality highest frequency of category 4 (local continental attention has also been paid to the large-scale climate) is found within the 0-interval, i.e. that topography of the surrounding area, which might representing a non-displaced tree-limit during the be expected to deflect certain airmasses, or to 1915/ 16--1975 period. This frequency value de­ cast an orographic rainshadow. In a few cases creases steadily for each higher interval. The fre­ personal knowledge of local weather conditions, quencies of the local climate types 2 and 3 are

Acta phytogeogr. suec. 65 86 LeifKullm an greater for the three highest displacement inter­ lnterval(m) vals, compared with the lowest. In other words, 5 n 213 6 = areas characterized by local continentality of the ] I1 7 ]sl ,' I climate have only to a relatively small degree been characterized by an upward shift of the 5 tree-limit. 1 6 r 7 [ sin=5 3 .

5

I 6 7 Aspect I 1 I lsl. n=49 I I ; I The aspect of a locality , i.e. the compass point 5 towards which the ground surface fa ces, is parti­ = 1. • 1 7 1+ ·· cularly important regarding the altitude of the ...... " '

tree-limit thereabouts. Generally speaking , the 5 highest tree-limits are recorded from S- to SW­ facing slopes, while N- to NE-facing slopes yield 0 50 100 % the lowest values (cf. Smith 1920; Kilander Fig. 69 . Percentual distributions of each of 8 main (1965). The underlying reason is the relationship compass points (site aspect) within each of the 4 tree­ between the amount of incident solar radiation limit displacement intervals and within the material as and local snow-accumulation (e.g. Lundqvist a whole (Total). The classification of site aspect is as 1968; Perttu 1972). follows:-I. N incl. NNW;- 2. NE inkl . NNE; - 3. E incl. ENE; - 4. SE incl. ESE; - 5. S incl. SSE; - 6. SW Quite obviously this factor called for investiga­ incl. SSW; -7. W incl . WSW; - 8. NW incl. WNW. (n

tion in relation to the extent of tree-limit dis­ = number of localities) placement at each locality . To this end the aspect of each site investigated in the field was deter­ mined with a hand compass, and assigned to the The snow conditions pertaining to each locality nearest of eight main compass points. were summarised and values assigned, on a The results of the statistical treatment of the four-degree scale. The assessments were made data, in histograms for the four displacement in­ on a basis of field observations from the time just tervals and the 8 compass points, compared to prior to , and during , birch-leafing at each locality , that for the material as a whole, are shown in i.e. the time of year at which the local differences Fig. 69. in the snow cover and their relation to the micro­ Only for ESE- to SE-facing sites was a con­ topography of the area are revealed most clearly. sistent and unequivocal relationship to tree-limit Many of the localities were also either visited, or displacement found. The percentage of sites fac­ examined through binoculars at a distance, dur­ ing ESE and SE increases with increasing up­ ing the depths of winter. The field observations ward displacement of the tree-limit. have been complemented with data obtained Apparently, the ecological conditions were from the local population and the local police such that they favoured an upward shift of the about the situation and extent of hillslopes sub­ tree-limit at ESE- to SE-facing localities. ject to accumulation of great depths of snow and considered dangerous from avalanches. The classification, at each locality, is valid for Depth and duration of snow cover the area between the PTL and the TL. At locali­ As mentioned already, both Sandberg ( 1940, ties where no tree-limit change occurred the clas­ 1958, 1960, 1963) and Nordhagen (1956, 1964), as sification was made for the stretch of ground ex­ well as Smith (1957), considered that a direct tending 100 m above the TL. Four grades of snow relationship existed between the expansion of the cover were used. birch in recent decades and changes in the dura­ The results of the standard treatment of the tion of the local snow cover. There was therefore data, in relation to the displacement-intervals, are a strong motive to check this relationship using shown in histogram form in Fig. 70, which reveals the data obtained in the present investigation. quite clearly a good positive correlation between

Acta phytogeogr. suec. 65 Change and stability of birch tree-limit in the Scandes 87

Interval (m ) Interval (m)

3 4 n= 213 1 n= 213 Tota l 2 2 3 4 5 . I. ) Total( I --- ( I - - . ' - . . I ·-- [' I ' ' .. . ' J - - ·-- ' ' - ' ' 0 2 · 0 2 3 4 n= 53 · = · . I -·· · B 5 .. - I . I . 1 c -·· I . I l, ' r ... . l . 1 l . ... - _,. I . 5-20 2 3 I n: 49 5 - 20 2 3 4 . . 1 ' . . . . 1 I ' . I .. I . ' J 1 . I ]+=·· . . ' .. '

5 - 40 3 4 25-40 2 3 4 r 2 n = 59 11[ 9 --- 1 n=5 . ' J . s [ r ' Il . ,' --- . . , -·· . . -·· ' . ' >4 . 0 1 2 3 4 I n = 5 2 >40 H 2 [ 3 4 5 I n=52 0 50 100% 0 50 100%

Fig. 70. Percentual distributions of each of the 4 Fig. 71. Percentual distributions of each of the 5 cate­ grades of depth and duration of local snow cover within gories of angle of slope within each of the 4 tree-limit each of the 4 tree-limit displacement intervals an,d with­ displacement intervals and within the material as a in the material as a whole (Total). The classification is whole (Total). The classification is as follows: - I. <5°; as follows: - 1. Extreme deflation area, mean max­ - 2. 5-10°; - 3. 11-20°; - 4. 21-30°; - 5. >30°. (n imum depth of snow cover 0-20 cm, ground surface number of localities) becoming snow-free long before birch-leafingoccurs ; - 2. Areas intermediate in character between grades 1 and 3, mean maximum snow depth, over a relatively wide area, ea 1 m, ground snow-free just prior to The slope angle may exert such an effect through birch-leafing; - 3. Extreme accumulation area, exten­ its relationship to such other factors as local sive and deep snowbeds still present at and after the time of birch-leafing, although between such snow beds depth and duration of snow cover, ground water there may be local patches of bare ground; - 4. Condi­ drainage, mechanical effects of snow accumula­ tions as for grade 3, but in addition known to be subject tion, frequency of -avalanches, solar energy bud­ to avalanches. (n = number .ofloca lities) get, depth of soil and soil composition etc. Although very much a non-active factor in it­ increasing grade of present-day snow cover and self, the angle of slope r�quires investigation in increasing upward displacement of the tree-limit. relation to the locally documented displacements There is therefore an obvious propensity for the of the tree-limit, since it might provide an indica­ birch tree-limit to have increased in altitude at tion of the potential action of other environmental localities which at the present-day enjoy a deep factors. and long-lasting snow cover, which would have At each locality the mean angle of slope of the been even deeper and longer-lasting at the turn of ground between the PTL and the TL, has been the century. estimated from a study of the contours shown on At localities with only a sparse and transient the respective sheets of the topographical maps, snow cover at the present-day, the birch tree-li­ scale 1:50,000, or larger if available. At localities mit has remained more or less static since 1915- for which a static tree-limit was recorded for the 16. 1915/16-1975 period, the angle of slope over the stretch of ground 100 m above the present-day tree-limit was estimated. The angle of inclination Angle of slope data have been subdivided into five categories. The angle of inclination of the ground surface at The results of the standard treatment of the data any particular point in the terrain is a habitat are shown in Fig. 71. factor which may affect the possibilities of estab­ The only relatively clear trend found is that lishment of birch seedlings, or of the vegetative localities with slopes of <5° inclination were less propagation of already extant trees and shrubs. frequently represented in the two highest dis-

Acta phytogeogr. suec. 65 88 LeifKull man

placement intervals than they were in the two Interval (m) -- lowest classes, i.e. on gentle slopes there was less otal = T �r----r-----2 -----.-� 3-.-, -4 r--1 5 -r-1 6 , n 213 tendency for any upward shift of the tree-limit to ' ' ' J .....-.. \ "" i , have occurred and it is obvious that no further ...... -......

___ correlation exists between angle of slope and :�:·] :-y6 ln=53 ­ tree-limit displacement. - .. -- .. -. .. 5-20 H 2 Slope morphology

This concept embraces the ecological presupposi­ tion that the possibilities for tree growth vary 25-40 1 2 with the geomorphology, slopes of different topographic nature bearing different degrees of 2 tree cover. As with angle of slope, geomorphological differ­ 0 100% �------�------�50 ences are coupled with the effects of such fac­ Fig. 72. Percentual distributions of each of the 6 cate­ tors as the depth and duration of the snow cover , gories of slope morphology within each of 4 tree-limit groundwater drainage, soil depth and composi­ displacement intervals and within the material as a tion, insolation etc. whole (Total). The classification is as follows: - 1. Virtually level or Six different categories of slope morphology only weakly undulating terrain. No fe ature of the mic­ were used to classify the conditions pertaining at ro-relief exceeding 1 m in mean amplitude. No difficul­ each locality between the PTL and a point ea 100 ty in driving over such terrain; - 2. An appreciably m above the TL, or to 100 m above the TL in well-developed micro-relief (feature amplitude 1-10 m) cases where the tree-limit had remained static consisting of morainic or other ridges, with intervening troughs and hollows. Impossible to drive across such 1915/16-- 1975. The localities were classified on a terrain. At about the level of the TL the nature of the basis of field notes and a large number of photo­ terrain changes to that of category 1 or 4; - 3. As for graphs. category 2 below the TL;- 4. Terrain has the form of a The results of the standard comparisons of the decidedly concave slope, which changes its inclination percentual distributions of the six categories of at the level of the tree-limit; - 5. As for category 4, except that there is no sudden change in inclination at slope morphology, within the four displacement the TL; - 6. Bare rock surface outcrops, boulder­ intervals and the material as a whole, are shown strewn slopes, or coarse screes. (n = number of local­ in Fig. 72. ities) It is obvious that categories 1 and 3 are predo­ minant among the localities belonging to the dis­ placement interval 0 (i.e. static tree-limit) and category 1 is unrepresented in higher classes. Ca­ Local land usage tegory 2 localities are unrepresented in displace­ The various types of land usage at the tree-limit ment interval 0 simply because of the way in have already been described in general terms in which this category has been defined, but are the chapter on Human impact around the tree-li­ predominant in the higher intervals. Categories 4 mit. and 5, concave slopes, are predominantly repre­ To categorise the kind and degree of human sented by localities belonging to the highest in­ influencefor each locality in detail, however, is a terval (tree-limit displacement >60 m). much more difficult matter. The classification There is thus in geomorphological terms a clear presented below, used for the localities in the distinction between localities -at which the tree­ investigated area, is therefore based on the care­ limit has remained static and those at which it has fully-considered probability that the usage(s) do­ advanced. The terrain in which the latter are situ­ cumented for a wider region is/are applicable for ated is more or less broken, whereas for the for­ the respective locality in question. The chosen mer the terrain is much smoother, or only gently sub-divisions comprise forms of land usage which undulating. have either ceased entirely, or markedly declined

Acta phytogeogr. suec. 65 Change and stability of birch tree-limit in the Scandes 89

lnterval(m) tion (see Appendix 11) and by direct observations in the field of the remains of hay-drying poles, 2 3 4 _ n 243 Tot al L....-1 _--+-' - --;- s ____,1 = --+-� --+[ 0 [ I fences, evidence of Lappish encampments etc. .. ' I I ' A detailed study of the available topographic ----f---,1 2 3 5 n 59 and ethnological descriptions and natural history o'---1 r _r _--T---'H��' = ' �! �! • accounts from the investigated area has yielded a f ' 0 n:61 rich harvest of local data. A full bibliography of L.-1 5-2 L.-1 --+-� _2 -t--l-3 ---:'--l]•j_5____,1 all my sources would unfortunately take up too ' ' .-, ,, much space. The most important works consult­ ed are cited in the chapter on 'Human impact 2 40 2 3 4 _ 6 5- '---1 ---+-.J- ----j,l"-----+-( -+-j s_l n: 7 around the tree-limit' and themselves contain further information on earlier sources. A general 40 2 3 n=56 selection of the more important works consulted > '---1 �r __[�.. L--L-I ·�r:_��-�_5 �' is provided in Appendix Ill. The results of the 0 50 100% standard treatment of the data, for each dis­ placement interval and for the material as a Fig. 73 . Percentual distributions of each of the 5 land usage categories within each of the 4 tree-limit dis­ whole, are shown in Fig. 73. placement intervals and within the material as .a whole The only correlations found were that a higher (Total). The classification is as follows: - i. Slight proportion of the localities of land-usage category and/or sporadic grazing by cows, sheep, goats and 5 (i.e. no documented fo rm of human impact) and horses. Scything of the sedge mires for hay may have a lower proportion of category 3 (i.e. Lappish occurred in the vicinity of the locality. Aim huts rela­ tively distant, or at most a single, rather small, aim hut activities) were represented in the higher dis­ within a radius of 5 km; - 2. Intensive and frequent placement intervals, i.e. with gradually increas­ grazing by cattle. Both sedge mires and natural forest ing values for the upward shift of the tree-limit. meadow vegetation cut for hay in the vicinity of the There are thus no indications that cessation of locality. Several aim huts present within a radius of 5 human influence led to a subsequent rise in the km; - 3. Frequent seasonal occupation by Lapps and/ or other visits to the locality involving usage of local altitude of the tree-limit . The present upward ex­ resources, e.g. seasonal round-ups of the reindeer tension of birch is definitely not a re-colonisation herds for marking, sorting out and slaughter, daily of lost territory. milking etc, within a radius of 2-5 km of the locality. Until about 1925 the reindeer will have grazed rather intensively within the same radius; - 4. Various other Chronology of birch expansion in the belt between kinds of land usage at the tree-limit, e.g. pack trails, mining etc.;- 5. No documented forms of land usage of PTL and TL the types described in categories 1-4. (n = number of The ages obtained for all the stems investigated in classifications; in certain cases more than one per lo­ the age-determination profiles and which were cality) growing above the tree-limit of 1915/16 (PTL) have been summarised in Fig. 74 (107 localities in both extent and intensity during the present altogether) . century. The ages have been converted into the absolute The localities have been assigned to five diffe­ years concerned and the data so obtained have rent land-usage categories on a basis of archival been grouped into quinquennia. The numbers of evidence, e.g. the maps and reports of former dated stems represented by each quinquennium land surveys such as the delineation of Crown are indicated along the vertical axis of the graph, and private land (Sw. 'avvittring') and enclosure with the time interval shown along the horizontal awards (Sw. 'laga skifte '), which provide relative­ axis. ly objective descriptions of the land usage in the These quinquennial intervals have been termed respective areas at different times in the middle 'colonisation periods', irrespective of whether and late 19th century. These data have been sup­ the stems concerned were produced from seed plemented by information derived from inter­ during that particular period, or whether they views with the older members of the local popula- were already present but under-developed , i.e. as

Acta phytogeogr. suec. 65 90 LeifKullman

No.of stems

1890-94 1895 -99 1900-04 1905-09 1910-1 4 1915-19 1920-24 1925-29 1930-34 ·1 935-39 1940-44 1945-49 1950-54 1955 -59 1960-64

Fig. 74 . Absolute distributions for successive quinquennia of the numbers of pioneer birch stems (for all the localities taken together), shown by annual ring counts of stem basal cores to belong to trees which colonised above the PTL during the respective quinquennium.

No. of local ities

35

1961 -65

30

25

20

15

10

1880-84 1885-89 1890-94 1895 -99 1900-04 1905-09 1910-14 1915-1 9 1920-24 1925-29 1930-34 1935-39 1940-44 1945 -49 1950 -54 1955-60

Fig. 75. Absolute distributions for successive quinquennia of the numbers of localities at which the present tree-limit altitude (TL) was first colonised during the respective quinquennium. The approximate date of tree-size attainment for the stems representing each quinquennium, according to growth rate estimates, is indicated at the top of certain bars.

Acta phytogeogr. suec. 65 Change and stability of birch tree-limit in the Scandes 91

prostrate shrubs. A wholly satisfactory answer to Interval I m) that problem was impossible, since the cores for � Total ,...... 11 21- 3 ---, -4 -----r--] s ) -6 -,--,1 7�J 8B"T""T'"'"1i n= 5 dating had to be taken, for practical reasons, , ' 9 ,' ,' , . ,' , :,:·, : some way ( 10-20 cm) above the stem base at ground-level. 5-20 H�( 4 ( 5 i 6 (1 (.j':o(n I n:29 At all events , however, the data provide an indication of the earliest period during which the stems started to grow in length faster than pre­ 25-40 4 ···r· j:j ·�·�---: -� j • ( • �:1-:t� I ·=·· viously (i.e. entered a growth-acceleration pe­ riod). In most cases, however, it is most likely

·-- n= 0 that the colonisation-period or perhaps more cor­ >4+H 3 \1 :::: -.:-.--}�-� ·];·,:\1 3 rectly a few years beforehand, is a good approx­ - 0 so 100% imation of the establishment time of individual birches (cf. Fries 1964). Fig. 76. Percentual distributions of each of the 11 quin­ quennial colonisation periods within each of 3 tree­ Besides, Smith (1920) states that at the time of limit displacement intervals and within the material as his surveys there was no belt of low-growing a whole (Total). The periods have been coded as fol­ birch bushes above the tree-limit itself. With very lows:-1. 1960-64; - 2. 1955-59 etc. backwards in time. few exceptions the bushes that were present grew at most 20-50 m above the tree-limit. Were a majority of the dated stems not derived from ly be regarded as being those of the pioneer colo­ seedling birches established after that time nists of their particular locality. In Fig. 75 these (1915/16), then Smith would necessarily have gi­ data have been set out in such a way that the ven a vastly different picture of the tree-limit number of localities with the same quinquennial vegetation in his account, i.e. a belt of birch colonisation of the present-day tree-limit level bushes would have been generally present. fo rms the vertical axis and the quinquennial pe­ Furthermore, in several cases I was able to riods of years, i.e. the periods of actual seedling count the rings in cores taken at ground-level and a •· colonisation at the p rticular altitude, forms the 20 cm higher up the same stems, and the age horizontal axis. difference never proved to be greater than six It is obvious from Fig. 75 that prior to 1915-19 years. birch colonisation at the altitude of the TL had Fig. 74 gives an overall picture of the chronolo­ occurred at only a small number of localities (ea gy of the phases during which colonisation of 11 %). In general this process occurred appreci­ successively higher altitudes was most intense in ably later on, and in fact it is indicated that the the particular altitudinal belt considered, i.e. be­ maximum was first attained in 1940-44. Because tween the PTL and the T L. of the slight inexactitude in the dating method the In summary, Fig. 74 shows that after 1910-1914 time of this intense colonisation falls, however, birch colonised the region above the tree-limit, at within the preceding quinquennial period (1935- that time, at an ever-increasing rate which 39). Individual birches (trees or shrubs) were pre­ culminated during the period 1940-44, or perhaps sent at the TL-level in 1950 at ea 95 % of the a little earlier if allowance is made for the time localities at which age-determinations of tree-li­ taken to grow from seedling to a 10 to 20 cm-long mit stems were made and at which the tree-limit stem (see p. 92). After the 1940-44 quinquennium had risen. the birch colonisation at successively higher alti­ Fig. 75, however, gives no indication of any tudes was abruptly reduced. possible differences between localities which might exist if account were taken of the degree of The colonisation of the present-day tree-limit level the shift in the tree-limit throughout the investi­ For 95 of the localities at which a rise in the gated area. fo investigate this problem Fig. 76 altitude of the tree-limit was recorded, data also was constructed, in which the same data as above exist for the ages of the oldest stems of tree were used, for each quinquennial period, but now birches growing at the TL. These stems can right- subdivided as histograms showing the percen-

Acta phytogeogr. suec. 65 92 Leif Kullman tual representation of each of 11 quinquennial birch growing in the upper part of the subalpine periods within each of three tree-limit displace­ belt in Norway. Haglund (1905) cites a value of ment intervals compared with the distribution for �7 cm for birches growing in the subalpine belt the whole body of data. in northernmost Sweden. Fig. 76 shows quite clearly that with increasing On a basis of the present value (8.6 cm/year) a degree of displacement of the tree-limit (1915/ certain opinion can be formed about the times at 16-1975) the attainment of the present-day tree­ which the respective pioneer stems at 95 locali­ limit (TL) was, on average, progressively de­ ties, attained tree size (i.e. a minimum stem layed. This suggests that throughout most of the length of 2 m). On average it took 21 years for a period up to about 1950 the conditions for birch stem to grow from a length of 20 cm to 2 m. By colonisation became more favourable at a conti­ adding this figure to the respective colonisation­ nually increasing altitude, i.e. favourable condi­ periods (quinquennia) in Fig. 75 the resulting (see tions for birch expansion did not set in simul­ Fig. 75) conclusion is, that, at ea 62 % of the taneously over the whole of the available area localities in question, the TL was established at between the PTL and the TL. that particular altitude at some time after 1955. Allowing for the unavoidable inaccuracy in dat­ ing, due to coring some decimetres above ground-level, this date is more probably ea 1950. Establishment of the TL A more direct measure of eventual changes in In the previous two sections the timing of the the altitude of the tree-limit after 1950 can be birch expansion within the investigated area as a obtained by comparing the data for the TL found whole has been established for the belt between in the present investigation with the data avail­ the PTL and the TL, as well as at the TL. able for the same localities given by Kilander The question arises, at what period(s) of time (1955 and pers. comm.) and Smith (1951) for the did the birch stems growing at the TL attain a local tree-limit at about 1950 (for details see the minimum height of 2 m, i.e. when did these birch­ locality descriptions). In this way data for 21 of es become trees? A complete answer demands a the total 214 localities in the investigated area knowledge of the mean annual growth in length of were available. birch stems, involving a tree-ring analysis of .the At 12 of the 21 localities (i.e. ea 57 %) the stems of the pioneer individual birches. This altitude of the tree-limit at about 1950 lay >5 m would have taken an excessively long time to lower than at the present-day (TL). At the accomplish and was impracticable. Instead, a remaining 9 localities the tree-limit was either the rough answer has been attempted by making an same as at present, or was insignificantly lower. analysis of the mean annual growth in length of 16 The localities available for comparison are not representative stems from trees growing at the entirely representative of the localities investi­ TL. The basis for this work has been counts of gated over the area as a whole, but they do annual-rings from cross-sections sawn at 10 cm­ provide some idea of the tree-limit changes since intervals up the stem, from the base to the top. 1950. Stems adjudged to be 30-50 years old from the Ottfjall massif in Jamtland and from Skarvarna and Klasberget in Harjedalen were investigated. Minimum age of stems of trees growing at the TL All the 16 stems were growing on fairly gentle As mentioned above, the age determinations of hillslopes covered with a Vaccinium myrtillus­ stems of birches growing at the TL were primari­ dominated dwarf-shrub heath. The maximum ly those of the obviously oldest stems of birches mean depth of the snow cover was about 1 m. of tree-height. In certain cases, however, stems The annual mean increase in stem length (with appreciably younger than those of the pioneer s.d.) for the period 1940-1965 was found to be birches were dated. The ages and growth rates of 8.6±0.31 cm. In comparison, Kj elvik (1973) and such stems provide useful information about the Wielgolaski (1975) recorded mean annual in­ growth conditions for birches at the tree-limit creases for the past few decades of 6-11 cm for during about the last 25 years (1950-1975).

Acta phytogeogr. suec. 65 Change and stability of birch tree-limit in the Scandes 93

Table 11. Attainment of tree-height (�2 m) of birches which higher than elsewhere, whereas at the present­ colonised the present tree-limit (TL) at different times within day it is relatively lowest. This radical reversal of the period 1950- 1965. the relative altitude of the tree-limit in the two contrasted groups of localities indicates that in Colonisation No. of stems Date at which period dated they attained most cases the birch tree-limit is not conditioned tree-height by the action of thermoclimatic factors on the

1951-55 11 1972-76 physiological processes which control plant pro­ 195(H)0 4 before 1976 ductivity. Had such been the case, then the de­ before 1976 1961-65 I gree of displacement of the tree-limit should have been directly proportional to the absolute altitude of the local tree-limit in 1915/16. Instead, one The data set out in Table 11 show the numbers must suppose that the local thermoclimate con­ of such stems, ordered according to the quin­ trols the position of the birch tree-limit in some quennia in which colonisation occurred, which grew indirect manner, i.e. by affecting a habitat factor, in length by a minimum value of 1.8 m after about or factors, which is/are operative over a wide 1950. The probable dates at which these stems area (i.e. altitudinal interval). The greater the ac­ attained tree-height (� 2 m) are also indicated, tion-radius of the said factor or factors, the based on the mean annual growth rate of 8.6 greater the degree of displacement of the local cm/year, established previously. tree-limit. The results clearly show that an increase in stem length, from 10-20 cm to � 2 m, was pos­

sible, even into the 1970's, for birches growing at Changes in the growth rate and vitality of indi­ the TL at localities for which a rise in the birch vidual birch stems during the present decade tree-limit was evidenced. The growth in length of the stems of 47 birches of, or just under, the minimum for tree-height was Relationship between the degree of tree-limit studied on 8 representative sample plots (!Ox 10 displacement and the altitude of the PTL m). The plots were laid out in 1972-73 and check­ The mean values and standard deviations have ed in 1975 or 1977, although a few plots were been calculated for the PTLand the TL for all the visited annually. Photographs, taken in different localities within each of the four displacement years, provide confirmatory evidence in some ca­ intervals (Table 12). ses for the degree of growth in length which took As a generalisation, the table shows that the place (see Figs. 19, 20, 21; 32, 33; 36, 37; 41, 42, greater the increase in the altitude of the tree-li­ 43 ; 55, 56; 57, 58; 60, 61, 62). mit, the lower the absolute altitude of the tree-li­ All the stems were growing within the local mit was in 1915/16 at the respective locality. At limits for the altitudinal rise in the tree-limit localities at which the tree-limit has remained 1915/16-1975 at each of the following four locali­ more or less unchanged during the present centu­ ties: Hamrafjallet (S-SE aspect), Anntjall (W as­ ry, the tree-limit altitude in 1915/16 was relatively pect), Flatruet (N aspect) and Ottfjallet (S as­ pect). Stem lengths were measured each time with a rod marked off in decimetres.

Table 12. The mean values (with s.d.) for the altitude of the The results are set out in Table 13, which tree-limit (in m a. s. l.) in 1915/16, compared with those for shows that 69 % of the stems increased in length 1975, grouped according to the degree of upward displace­ during the present decade. The few cases in ment of the tree-limit. which stems decreased in length are explained by stem breakage at the base due to the weight of Tree-limit Past tree-limit Present tree-limit displacement (PTL 1915/16) (TL 1975) snow in winter, or to grazing of the tips by hares in winter. 0 912±61 912±61 5-20 903 ±60 924±61 Where the snow cover is deepest the stems are 25-40 892±60 933±62 bent so low by the weight of snow that the hares >40 877±78 952 ±81 can usually easily reach the tips of even

Acta phytogeogr. suec. 65 94 LeifKull man

Table 13. The means (x) and standard deviations (s.d.) for �he stems are seen to have suffe red loss or disappear­ annual increase in length (dm) of birch stems during the penod ed entirely. This is perhaps explained by the fact 1972/73- 1 975/77. The stems from the eight plots are sub­ divided into three groups, according to whether stem length that the stems photographed were growing closer increased, remained unchanged, or decreased. to the present-day tree-limit than were the stems on the sample plots as a whole. Length change No. of stems x (dm) s.d. (dm) For individual birches with their main stem Increase 32 0.81 0.39 broken basally by the weight of snow accumula­ Unchanged 10 tion in winter, a rapid and prolific regeneration Decrease 5 3.04 3.3 from preexisting basal shoots was visible. At 46 of the entire 214 investigated localities tree-sized birches (cf. Pruitt 1970). This factor living or dead birches (0. 3-2.5 m in height) were has been found to be quite important in determin­ present above the TL. At 8 of these 46 localities ing the physiognomy of birches growing at the these birches were either dead or in an extremely tree-limit. s�ch grazing results in a dense mat of poor condition (just a fe w basal shoots still alive). branches which all finish at the same level, pro­ In all cases they were, or had been, quite young ducing a table-top effect like that of deliberate topi­ birches, scarcely exceeding 25 years in age. The ary (cf. Resvoll-Holmsen 1918; Bliithgen 1960) . cause of death in certain cases was obviously The mean annual growth rate for the stems from the mechanical effects of accumulated which increased in length was 8.1 cm per year, a snow, although the presence of a few dead, yet value in almost full agreement with that calculat­ still upright, stems indicates that other factors ed previously (see section, Establishment of the were also at work. TL) , viz. 8.6 cm per year. The conclusion from the data reported in this Whenever the eight sample plots were re-visit­ section must be that there has been no general ed, a careful watch was kept for the presence of reduction in the vitality of the birches which were seedlings or saplings. In no cases, however, were· responsible for colonising the belt between the any found. PTL and the TL, i.e. which became established In addition to the above-mentioned plots, a there during the course of the present century. check on stem growth was made by taking photo­ The death, or reduced vitality, of a minor propor­ graphs from the same viewpoint on different tion of the birch stems kept under observation occasions, of subjectively-chosen represen�ative may be nothing exceptional, but simply repre­ birches. Such data are available from localities sents a quite normal successional phenomenon in regularly scattered all over the investigated area the population dynamics of birch growing near to and always from the belt where the tree-limit has its altitudinal tree-limit. risen during this century. Only major changes in The greatest threat to the continued existence growth and/or vitality were discernible from of the stems of well-established birch trees is these photographic comparisons. without any doubt the straightforward mechani­ The results, set out in Table 14 and illustrated cal effect of the pressure of wet snow during the in some of the photographs cited above, show a period of the snow-melt in spring (see Fig. 59) and general agreement with those given by the sample perhaps locally the effects of sporadic avalanches plot surveys, although a greater proportion of in winter.

Table 14. Changes in the vegetative development of individual birches, as revealed by photographs taken in 1970/73 and 1975-77. Summary of results

Changes in stem vitality and length No. of The relationship between the degree of displace­ stems ment of the birch tree-limit, or its virtual stability, Growth 2 during the present century (1915/16-1975) and No obvious change 30 A few stems have been bent to the ground 7 the local magnitude of certain environmental fac­ A few terminal shoots have died off 3 tors has been investigated. Large parts of the shoot system have died-off 2 The results of these analyses indicate that cer-

Acta phytogeogr. suec. 65 Change and stability of birch tree-limit in the Scandes 95 tain abiotic factors, such as the nature of the local cerned (see the section on The recent climatic macroclimate, site aspect, depth and duration of fluctuation). the snow cover, angle of slope and slope morpho­ 3. At 57-62 % of all the localities at which an logy, have differed, at least qualitatively, when undoubted altitudinal rise in the tree-limit was studied in relation to the local degree of dis­ evidenced and where tree-limit birches were dat­ placement, or otherwise, of the tree-limit. ed, the pioneer birches now growing at the TL The intensity of some of these factors was firstattained tree-height afterabout 1950. found to be directly proportional to the extent of 4. The TL was established most recently at locali­ the altitudinal rise in the tree-limit. No such rela­ ties at which the scale of the altitudinal increase tionship was found to exist with a variety of hu­ was greatest, i.e. the conditions determining man influences and their cessation or diminution. birch colonisation at the tree-limit became fa­ When the data were examined with regard to vourable at successively higher altitudes over a the timing of the birch colonisation, which result­ period of time, not everywhere between the PTL ed in the increased altitude of the tree-limit in and the TL at once. different parts of the investigated area, the 5. The absolute rise in the altitude of the birch following results were obtained: tree-limit has on average been inversely propor­ 1. Colonisation of the belt between the PTL and tional to the local position of the tree-limit in the TL started during the first few years of the 1915/16 (PTL). This suggests that air temperature 20th century. The process speeded-up after ea only exerts an indirect control, most probably via 191�1914 and had a maximum at the end of the some other local habitat factor(s). 1930's. A distinct reduction in the extent of birch 6. The stems of a small number of subjectively colonisation in the above-mentioned belt is evi­ chosen birches growing near the TL have on ave­ dent from the period 194�1 950 onwards. rage increased in length by at least 1.8 m during 2. At the start of, or mid-way during, the 1940's, the past 25 years , i.e. after the culmination of the individual birches (trees or shrubs) were already recent climatic amelioration. present at the altitude of the TL at 80 % of the 7. There are no indications of any general dimi­ investigated localities at which an undoubted alti­ nution in vitality during the present decade of tudinal rise in the tree-limit has been evidenced and at which age-determination transects have those birches which have colonised the belt be­ tween the PTL and the TL since 1915/16. been made. By about 1950 this figurehad risen to 95 % of the above-mentioned localities. The pe­ 8. An important cause of the death of well-estab­ riod 194�4, or more correctly probably slightly lished stems in the present-day birch populations earlier (1935-39), appears to have been one in at the tree-limit is simply mechanical damage which conditions were particularly favourable for from the pressure of the wet snow cover during birch colonisation above the PTL. This period in the time of the spring snowmelt. Grazing of the fact coincides with the culmination of the recent aplcal shoots of side and main branches by hares climatic amelioration, at least as far as the mean in winter may also be important locally' especial­ temperature for the triterm June-August is con- ly in modifying the form of such birch trees.

Acta phytogeogr. suec. 65 Discussion and general conclusions

The nature of the factors causing change or stabili­ gated area in which a positive altitudinal displace­ ty of the tree-limit ment of the tree-limit was recorded were any An altitudinal rise of the tree-limit for birch dur­ remains of former trees found, which might have ing the past 60 years has been found to be a indicated that the tree-limit advance was simply general phenomenon over the whole of the investi­ due to a re-colonisation of areas fo rmerly defo­ gated region. The basic cause of this positive rested by human interfe rence with the landscape. displacement of the tree-limit must therefore According to Holmgren's (1912) investigations in have been a factor operative over a wide area, northern Scandinavia, dead birch stems lying on although the obvious fact that the degree of dis­ the ground surface can be preserved for 70-80 placement differed considerably even between ad­ years and Barth (19 15) states that birch bark can jacent localities, indicates that the resultant effect be preserved for ea 100 years . Summer-farm of this prime factor can be modified to greater or transhumance culminated at about the turn of the lesser degree by the local habitat factors, both century. Had this farming activity been respon­ past and present. sible for a widespread depression of the tree-limit The statistical treatment of the data has en­ then the remains of some of the trees formerly abled the identification of some of these habitat present ought to have still been visible, at least at factors and their lowest common denominator. a few of the localities within the investigated area Thereby an attempt has been made to identify the at which a positive displacement of the tree-limit basic cause(s) of the tree-limit displacement and was recorded. Perhaps the frequent occurrence to add to our knowledge about the tree-limit as a of dense thickets of Salix spp. and Juniperus natural phenomenon. communis enabled some regeneration of birch, to As mentioned above, in certain cases quite large occur which may explain why there was no gene­ differences were found in the degree of displace­ ral lowering of the tree-limit in heavily grazed ment at neighbouring localities. This makes it areas (cf. Anonymous 1906) . highly probable that the factors concerned all The proven fact that the conditions for birch show marked differences in intensity over quite colonisation improved at an ever-increasing alti­ short horizontal distances. Various abiotic fac­ tude is a fu rther indication that in general terms tors fulfil this requirement and would therefore the upward altitudinal displacement of the tree­ appear to be those most probably concerned. The limit has formed part of a primary, not a seconda­ relevant biotic factors, human impact on the ry ecological succession. Had the upward birch landscape included, do not normally exhibit such expansion been merely a re-colonisation of lost sharp horizontal discontinuities in nature near the territory, one would have expected to find that tree-limit as do certain abiotic ones (cf. Klikoff this had occurred contemporaneously over the 1965; Barry & van Wie 1974) . whole area between the PTL and the TL, consi­ The statistical treatment of the data has also dering that there is seldom any shortage of viable revealed an indisputable relationship between a birch seed in the lower part of the low-alpine belt number of interdependent abiotic habitat factors, (see below) . On the whole, therefore, human uti­ of varying degrees of intensity, and the degree of lisation of the tree-limit region, although formerly displacement of the tree-limit. On the other hand, quite intensive at many of the investigated locali­ no such relationship was found with the degree of ties, did not lead to a depression of the birch human impact on the landscape or type of land tree-limit (cf. Kilander 1965). A more open ques­ usage. Nowhere within those parts of the investi- tion, however, is whether the tree-limit would

Acta phytogeogr. suec. 65 Change and stability of birch tree-limit in the Scandes 97

Fig. 77. The summer grazing of livestock has virtually ceased at most of the shielings during the course of the present century. In the open woodland, or park­ land-like fo rest grazings, a vigo­ rous growth of young birches sprang up as grazing ceased. The photograph was taken in the vicinity of a shieling on the E-facing hillslope of Ramund­ berget in Haijedalen. The vege­ tation in the fo reground is meadowlike and dominated by Geranium sylvaticum . Photo: July 27, 1974.

have risen during the past 60 years at certain of intensity of certain abiotic environmental factors the investigated localities if the degree of grazing and the degree of displacement of the local tree­ pressure had remained stable, instead of steadily limit. All these environmental parameters have decreasing or ceasing entirely. It is conceivable an effect on the depth and duration of the snow that grazing might have led to the failure of all the cover at each of the investigated localities. How­ attempts of birch colonisation at higher altitudes ever, a direct causality is not immediately obvio­ following the . improvement in the natural envi­ us, since the snow conditions are intimately rela­ ronmental conditions (climatic amelioration). ted to other ecological factors , as mentioned At lower and middle levels within the subalpine above (cf. Watt & Jones 1948; Poore & McVean belt it is quite clear that the present-day increase 1957; McVean & Ratcliffe 1962). in forest tree density is at least to some extent due Nevertheless, there is no doubt at all that the to the cessation of grazing and hay-making (see degree of recent upward displacement of the Fig. 77). tree-limit at any particular locality is an expres­ Thus it is obvious that the upward shift of the sion of the degree of change of the snow condi­ tree-limit since 1915/ 16, generally speaking, has tions thereabouts. been caused by changes in some natural, non­ On average, characteristic snow-accumulation human, environmental factors. areas have exhibited th({ greatest degrees of dis­ placement of the tree-limit, whereas those locali­ ties for which no change in the tree-limit altitudes Relationship between degree of displacement and were found are situated in snow-deflation areas , type of habitat and in between these two extremes the tree-limit As mentioned previously, a positive relationship displacement has also been intermediate in scale. has been shown to exist between the degree of

Acta phytogeogr. suec. 65 98 Le ifKullman

Extent and duration of the snow cover boundaries between these two contrasting types Before a closer elucidation and explanation of the of localities have obviously been displaced during natural course of events involved in the tree-limit the first half of the 20th century (evidence pre­ changes can be attempted, the general principles sented below). Several different explanations can underlying the distribution of snow in moun­ be put forward to account for the displacement tainous areas must be discussed. postulated above: It has long been known that the uneven distri­ 1. an absolute diminution in the annual snowfall. bution of the snow cover in the alpine and upper 2. an earlier and more complete melting-away of part of the subalpine belt follows a definite pat­ the snow cover, due to an increase in the supply tern. The winds, which bring and deposite snow of advective heat. in the particular part of the mountain chain in 3. increased solar radiation in springtime. which the investigated area lies, blow for the 4. a reduction in the frequency of winds fr om a most part from the west or north-west. Most of westerly direction, i.e. diminished wind-drift of the snow is deposited on the lee-side of terrain snow from windward to leeward localities. features, i.e. on east- and south-east facing slo­ 5. various combinations of the above 4 factors. pes. On the wind wards side of the mountains the Postulates 1, 3 and 4 are not supported by the snow fills up all depressions in the terrain, whilst more even parts of the slopes receive a relatively meteorological observations made during the minor snow cover and become snow-free early on 60-year period under discussion (cf. Bh.ithgen in the spring. Any depth of snow deposited on 1942, Pershagen 1969, Johannessen 1970, Schytt 1973), whilst postulate 2 agrees entirely with the such slopes during windless conditions is later removed by storms, being carried away and re­ known climatic changes (as described in the sec­ deposited on the leeward sides, where it builds up tion The recent climatic fluctuation). the typical wind-compacted snowdrifts . The above information has mainly been drawn from the following sources: Hogbom 1897 , V es­ Evidence for an earlier snow-melt tergren 1902, Hamberg 1907 , Enquist 1916, Smith As stated above, the major cause of the diminu­ 1920, Lundqvist 1969. tion in the depth and duration of the snow cover The geological structure of the area produces a has without any doubt been an increase in the characteristic macro-relief, with more or less amount of snow melting-away during spring and gentle W-facing hillslopes and short, steep, E- and early summer, due to an increased supply of SE-facing slopes. The long windward and steep warmth . Schytt (1962 , 1967) has shown that the leeward slopes, in turn, greatly facilitates snow decline in the extent of glaciers and permanent accumulation on the E- and SE-facing sides of the snowfields during the present century has been mountains, where the insolation conditions fur­ controlled by changes in the temperature condi­ ther serve to prolong the retention of these, prima­ tions in summer, in the length of the ablation rily orographically-conditioned, snow accumula­ period, and in the insolation conditibns. Ablation, tions (cf. Lundqvist 1968; Perttu 1972). The inso­ in other words, is a fu nction of altitude (m a. s. l.) lation conditions nevertheless play a minor role in of a locality. In principle, therefore, a thermic determining the site of localities with a predomi­ amelioration will result in an upward displace­ nantly long-lasting snow cover. It is by no means ment of the ablation gradient. Glacier retreat has · unusual to find even thermically-favourable S­ been a well-known expression of the climatic facing slopes which receive and retain an ex­ amelioration during the present century (cf. tremely deep snow cover and which are extremely Faegri 1934; Ahlmann 1943 ; Karlen 1973 ; Kar­ susceptible to avalanches (cf. Enquist op.cit.). len & Denton 1975; and others). As a general rule the above-mentioned pattern Bergstrom (1955) and Lundqvist (1969) have of alternating localities receiving inconsiderable studied the changes in the extents of those gla­ or massive snow covers is found to be pretty ciers which are present within the investigated stable from year to year (cf. Sernander 1905; En­ area. They found that after attaining a maximum quist 1910; Kronfuss 1967). However, the extent about 1908 the glaciers thereafter continu-

Acta phytogeogr. suec. 65 Change and stability of birch tree-limit in the Scandes 99

ally retreated up to the 1960's, with a particularly adays ( 1969-78) all the snow has disappeared here rapid retreat after ea 1930 and a marked slowing by the end of July. down in the rate of retreat again after ea 1950. In the Scottish Highlands, too, former semi­ Also the permanent and semi-permanent snow­ permanent snowbeds have gradually disappeared fields within the investigated area have declined during the course of the climatic amelioration of both in frequency and extent in parallel with the the present century (Watt & Jones 1948) and gra­ retreat of the glaciers. The result has been a gen­ dual changes in the vegetational composition of eral drying-out of the soils in the alpine and sub­ these areas have been recorded (McVean 1958). alpine belts, by a reduction in the supply of melt­ An increased permanency of the snowbeds in the water from the snowbeds during the main sum­ same area has once more been noted since the mer period (Smith 1957). mid- 1960's (Spink 1969) . Local informants within the present area of For certain of the habitat types represented in investigation have reported that former streams the investigated area, therefore, the final disap­ have dried-up and that certain high-lying fens pearance of the snow is earlier than it was in have become much drier, although when assess­ 1915/16. Thereby, that part of the summer which ing such reports one must bear in mind the fact is most favourable, from the temperature condi­ that such mires and fe ns which are no longer tions point of view, to the vegetation for growth, mown for hay, may also have altered the hydro­ maturation and reproductive processes, including logical conditions (cf. Kullman 1977a) . A similar seedling establishment, is thus prolonged. drying-out of the fens in other parts of northern Smith's (1957) studies in part of the investigat­ Fennoscandia has also been reported (Hustich ed area showed that the area covered by those 1937, 1940 ; Huse 1965). plant communities which require a moderate to A particularly good example of the earlier considerable degree of 'protection' by the snow onset of the snowmelt latterly is given by compar­ cover decreased during the period 1919-1950, ing Sernander's (1905) description of the snow while those communities requiring a shorter snow conditions in 1904 on the SE-facing hillslope of cover increased their coverage correspondingly. Hamrafjall (locality 191), with those at the pre­ This can scarcely have been due to anything sent-day. Sernander (op.cit.) describes a snow­ other than an earlier disappearance of the snow fieldof immense horizontal extent, just above the cover and a consequent increase in soil aridity. tree-limit, which remained so until the middle of July. From 1969-1975 I have myself observed this

same snowfield, and each year, by the middle of Characteristic habitat features of localities with a June, or in the latter half of June at latest, it had recorded rise in tree-limit already become split up into a small number of discrete snow patches, each a few hundred m2 in Duration of snow cover extent. Even these snow patches had disappeared The factor common to al1 the localities at which a entirely by the end of July (even during the cold rise in the birch tree-limit was recorded is the summers of 1977 and 1978), whereas in a photo occurrence of orographically-determined snow taken by Sernander in August 1904 (Sernander accumulation, i.e. an ample snow cover. In other op .cit.) the situation resembles that which at pre­ words, the depth of the snow cover is appreciably sent exists during the first part of July. greater than that which would be expected from A further piece of evidence for the earlier dis­ the local snowfal 1 data alone, and in consequence appearance of the snow-beds at the present-day is the duration of snow cover is prolonged. fu rnished by a .diary observation made by two The greatest accumulations (vertical and hori­ visitors to part of the investigated area in 1796 zontal extent) of snow here coincide with the (Robsahm & Schwab 1938). On August 18th they sites at which the greatest displacements of the crossed the upland plateau at the foot of the ESE tree-limit were recorded. Localities at which and SE slopes of Lill- and Stor-Skarven (locali­ more moderate displacements of the tree-limit were ties 183 and I 84 respectively) and noted that recorded are those at which the accumulation of snowdrifts were present on these slopes. Now- snow in winter is, relatively speaking, slight but

Acta phytogeogr. :mec. 65 100 LeifKullman unbroken over fairly large vertical distances. Columbia, Brink (1959) and Fonda & Bliss (1969) The nature of the local climate , the angle of have shown that certain coniferous tree species slope and the aspect of a locality are factors have colonised formerly treeless areas of heath­ which are indirectly correlated with the degree of land near the tree-limit, following alterations in displacement of tree-limit. As shown above, the the local snow conditions. way in which the climate has changed during the present century has led to an increased rate of Vegetation period melting of permanent or semi-permanent snow­ beds. Such a development of the climate has been It is naturally tempting to see a plausible explana­ the pre-condition for the recorded rise in the tion for the rise in the birch tree-limit as a direct birch tree-limit. consequence of a lengthening of the vegetation Smith (1920) found that at localities receiving period, from the increased rate of melting of the an ample snow cover the tree-limit coincided with snow cover and/or an improvement in the air the position of the margin of the retreating snow temperature conditions during the vegetation pe­ at the time of birch leafing (cf. also Hustich 1937; riod. In other words, in 1915/16 the potential net Nordhagen 1943), a circumstance which can be assimilation rate was insufficient to permit tree similarly demonstrated at many localities at the growth in the belt where the tree-limit has since present-day (see Figs. 15, 16, 53). risen (cf. Boysen-Jensen 1932; Sarvas 1970). That the altitudinal tree-limit has risen in an However, this general tree-limit theory has not inverse relationship to its absolute altitude in been accepted by e.g. Wardle (1974) and Holt­ 1915/16, as shown above, indicates that the de­ meier (1974). gree of displacement has been conditional on a A further argument against the above supposi­ corresponding decrease in the intensity of a fac­ tion is the fact that after 1950, when the climatic tor which depresses the local tree-limit. The only amelioration culminated and reversed, the up­ probable factor is the depth and duration of the ward displacement of the altitudinal birch limit local snow cover, which has been proven to be came more or less to a complete halt, whereas the very susceptible to variations of the thermocli­ shoots of already-established birch individuals mate . This conclusion is further supported by the above the PTL continued to grow in length, and results of the present investigation, which indicate still do. Analogously , Zackrisson (1978) found that, in many cases, the birch tree-limit ceased that natural regeneration by seed of pine and de­ to rise any fu rther once a topographically and ciduous trees, on a lake-shore in a river in N edaphically unfavourable niveau was reached Sweden, was strictly concentrated to the period (see section 'Slope morphology'), i.e. piano­ 1930-1955. This was thought to be related to the convex landscape fo rms with little snow accumu­ climatic amelioration and consequent annual wa­ lation and low soil moisture conditions. ter-level (i.e. meltwater) fluctuations. That a clear relationship exists between the birch tree-limit displacement and 'nival phenolo­ gy' is shown at many places within the birch Germination-establishment expansion belt by the presence of a fr inge of The conclusion to be drawn is that it is the joint young birches surrounding depressions in the combination of edaphic conditions and seed ger­ ground occupied by long-lasting snow-beds (see mination/seedling establishment which reacts Fig. 25). A similar phenomenon has been shown sensitively to the climatic fluctuations and which in the case of spruce growing in the fo rest tundra determines the ultimate altitudinal position of the ecotone in north-western Canada (Larsen 1965). tree-limit. According to Wardle (1974) the forest­ It is especially interesting, in this connection, limit for Nothofa gus solandri iri New Zealand is to note that in the Cascade Range in the United controlled in a similar manner, by a series of States Franklin et al . ( 1971) found that a recent critical threshold values for the habitat factors immigration of the tree Abies lasiocarpa into which are operative during the first summer after subalpine meadows has taken place , which they germination. ascribe to the recent climatic change. In British The general conclusion is that the rise in the

Acta phytogeogr. suec. 65 Change and stability of birch tree-limit in the Scandes 101 tree-limit is brought about by the increased pos­ birch seed germination at the forest-limit requires sibilities for seed germination and seedling estab­ soil surface temperatures which are hardly ever lishment provided by an earlier and more com­ attained in 'normal' summers. The reduced ex­ plete disappearance of the snow cover and a subse­ tent of the snowbeds ought therefore to have quent decrease in meltwater influence. So far as improved the chances of successful birch coloni­ seed germination is concerned, the decrease of sation at certain places above the PTL. soil moisture, by itself would be expected to be a Since the birch normally develops a vertical less important factor. According to research re­ main-root very early on during its life-cycle (Lai­ sults presented by e.g. Heikinheimo (1915), Lin­ takari op.cit.), it is obvious that seedling estab­ kola (1930) , Sarvas (1937), B�rset (1962) and lishment is greatly hampered in fr ont of long-last­ Kinnaird (1974), germination does not occur un­ ing snow fields, where the vertical gradient of soil less there is already a high degree of moisture temperature is very steep (Mani op.cit.). Smith present. In fact, an excess of water does not (1920) states that the majority of birch seedlings hamper germination provided it has fairly high which he found were growing in the 'warm oxygen content (Mork 1944). The latter condition Dryas-heaths', a fact which fu rther emphasises the ought always to be fu lfilledfor the localities dealt importance of soil surface temperatures in this with, since the supply is non-stagnant snow connection. Havranek (1972) has carried out ex­ meltwater of low temperature. In an experimental periments with seedlings of Larix decidua and study from the Rocky Mountains, Holway & Picea abies near the tree-limit in the Alps. He Ward (1963) found that the cold meltwater had a found that the soil surface temperature represent­ pronounced delaying effect on certain phenologi­ ed an important limiting which controlled the dry cal phases of many species of vascular plants, matter production of both tree species. although it is not quite easy to decide definitely That an improvement in the soil surface tempe­ whether it was the increase in soil temperature, ratures, in particular, occurred during the fi rst or the decrease of soil moisture, which was the half of the present century is evidenced in several operative factor. different ways, viz: The main positive effect of a decrease of soil 1. The 'palsas' (peat hummocks with a perma­ moisture is probably on seedling establishment. nently frozen ice core) or 'palsa-like' features This is suggested by an investigation by Bannister which Smith (1920) encountered in the investi­ (1964) , who showed that root penetration and gated area do not appear to exist at the present seedling establishment by Erica cinerea and E. day (Lundqvist 1969). A similar disappearance of tetralix were very poor in wet soils. The same can such features has been reported from other places be expected to hold for birch, with its normally situated close to the southern boundary for 'pal­ deep root penetration (cf. Laitakari 1934). sas' in Sweden (Wramner 1967). McVean (1956) has experimentally demonstrated 2. Henning (1895) states that the sloping fens on a high degree of mortality of birch seedlings in Snasahogarna, situated in the northwestern part very wet and badly aerated environments. of the investigated area, were still fr ozen 30 cm Furthermore, in snow-rich environments with a below the ground surface at the end of July, high proportion of finer soil fractions and water whereas nowadays there is no such frozen peat in saturated soil, the seedlings are permanently these mires at all in July. stressed by frost-heave. Earlier in the present paper it was pointed out A drying out of the soil should in fact be that the birch colonisation above the PTL was favourable for both germination and seedling es­ most intensive during a period which coincided tablishment primarily because of the consequent with the maximum intensity of the present clima­ rise in soil temperature (Holway & Ward 1965). tic fluctuation, so far as the absolute frequency of In the Himalayas, Mani's (1962) work has namely exceptionally warm summers is concerned. In shown that, during June , the temperature of the this context it is interesting to note Leach & upper layers of soil gradually increased with Polunin's (1936) observation, in Finnmark in increasing distance from the margins of the northern Norway , during the very warm summer retreating snow patch. According to Mork (1944) of 1930, that birch seedlings were found to be

Acta phytogeogr. suec. 65 I 02 Le ifKullm an present in that part of a snowbed locality which length of the vegetation period (as defined mete­ melted away last of all. This suggests that a suc­ orologically) during the present century, had led cession of only a few summers more favourable to improved seed production and seed maturity than average is sufficient to enable birch to colo­ by birches growing in the subalpine belt. nise areas from which it was previously excluded During certain years at least, the birches which because of the presence of too long-lasting snow form the tree-limit, and even birch shrubs above patches. Holmgren (1912), likewise, found that in the tree-limit may produce viable seed (Henning several places in the subalpine belt in northern 1889; Smith 1920; Soyrinki 1938; Sarvas 1952; Scandinavia birch seedlings colonised the peri­ Kullman 1976a; Kallio & Makinen op.cit.). It is pheral parts of snow patches during summers in nevertheless doubtfu l whether fluctuations in the which the rate and extent of the snowmelt were quantity and quality of the seeds produced by above average, but were unable to survive birches growing in the upper part of the birch belt through a subsequent unfavourable summer. are a limiting factor for birch regeneration from Furthermore, in the eastern Pyrennees, Braun­ seed within and above this vegetation belt (cf. Blanquet (1948) found that following a succession Sarvas 1948), since because of the relatively great of only a few extremely snowy winters the Nar­ seed production by the birch, and its excellent dus-dominated grass-heaths became strewn with distribution potential (Heikinheimo 1915; Res­ the seedlings of typical chionophiles, e.g. Sibbal­ voll-Holmsen 1928; Sarvas op.cit.; Kinnaird dia procumbens and Salix herbacea. 1968) an additional supply of seed from birches All the indications are that, before any success­ growing at lower altitudes, whose seed quality ful birch colonisation and establishment in new probably varies less, can always be counted upon areas can occur, a succession of summers with (cf. Aminoff 1907). above-normal air temperatures is necessary. This Smith (1920) reported finding birch seeds seve­ is precisely what occurred during the culmination ral hundred metres above the nearest tree-limit of the recent climatic fluctuation. birches. Elven & Ryvarden (1975) recorded a Since it is primarily seed germination and the dispersal distance of 4 km. Similar observations initial establishment of birch seedlings which have al so been reported from melting snowdrifts seem to take place periodically in the peripheral in Norwegian mountain areas (Lid 1937). parts of snowbeds and snow patches, one dares One may assume that on hillslopes which re­ to draw the conclusion that the immediate causes ceive an ample snow cover, the potential seed sup­ of displacements of the tree-limit are the periodic ply is always high enough to render any possible fluctuations in the climatically-conditioned eda­ fluctuations in seed viability virtually unimpor­ phic factors during the vegetation period. If e.g. tant, since in such habitats the birch seed is di­ winter survival was a decisive factor, then one stributed and accumulated according to the same would expect to find the habitats in question principles as described for the snow (cf. Porsild strewn every summer with birch seedlings. But 1951). During the period of the snow-melt it is by this is definitely not the case. no means uncommon, in certain places, to find the snowdrifts covered with a quite thick layer of birch seeds (see Fig. 78). Seed production Besides the onset of more favourable edaphic conditions for germination and seedling estab­ Heavy snow cover lishment, which followed as a consequence of the earlier melting-away of the snow, the germination The purely mechanical effects of the weight of percentage, i.e. seed quality and quantity of Betu­ snow in winter may also conceivably play a cer­ la pubescens (coli.), is also influenced by the air tain role in the population dynamics of the moun­ temperatures prevailing during the summer (Sar­ tain birch. Vestergren (1902) has suggested that vas 1937, 1948; Soyrinki 1938; Mork 1944; Kallio these effects may act as a differentiating factor on & Makinen 1978). the composition of the vegetation along the gra­ Bliithgen (1966) considered that the increased dient fr om bare and wind-exposed to snowpatch

Acta phytogeogr. suec. 65 Change and stability of birch tree-limit in the Scandes 103

Fig. 78. At localities receiving a deep snow cover a shortage of birch seed is very seldom a fac­ tor limiting birch colonisation. Accumulations of birch seed and catkin scales arise in such . areas according to the same physical principles which condi­ tion snow accumulation. During early summer the snow drifts are often found to be covered by quite a thick layer of wind-drift­ ed birch seeds and catkin scales. The south-facing flank of Ann­ fjallet, Harjedalen, 975 m a.s.l. Photo: June 12, 1971 .

localities. Ve (1940) has also maintained that the day. Projecting shoots and branches are subject occurrence of even just a few extremely snowy to mechanical forces which are proportional to winters is sufficient to more or less wipe out the the local degree of slope of the ground, to the birch cover over large areas, simply by the me­ depth of the snow cover and to the temperature of chanical action of the weight of snow. The me­ the snow (Ramsli 1951; Lenz 1967 ; In der Gand chanical effects of the snow cover have been 1968a, b). intensively studied in the Alps. For woody spe­ By building different kinds of mechanical hind­ cies the negative effects arise when the snow rances along such snow accumulation slopes the cover starts to settle during the snowmelt period. scale of such snow movements can be reduced The combined action of this downward settling and the losses of coniferous transplants exposed motion and the innate propensity of the mass of to such danger can be significantly reduced (In snow to slide downhill, leads to internal stresses der Gand op.cit.), a fact which would suggest that and strains within the wet snow mass, both local­ snow pressure may represent a negative factor ly and along the whole hillslope. The movement for natural tree regeneration in such places as of the body of snow, induced in this way, varies well. from several metres to just a fe w millimetres per As shown above, there is no doubt that mecha-

Acta phytogeogr. suec. 65 104 LeifKullman nical damage due to snow pressure represents a developed root system. Seedlings with root sys­ dominant mortality factor fo r birch stems which tems restricted to the upper part of the moving exceed a certain length (ea 1 m) . When birch layer of soil escape b�ing damaged in this way (cf. stems reach a certain size they lose their earlier Coker 1966). elasticity and break in two. On hillslopes which receive a particularly heavy snow cover, there­ Frost-drought fore , the mean age of the birch stems is often quite low, despite the fact that the birch popula­ A reduced risk of damage from frost-drought can tion as a whole maintains its continued presence be ruled out as the factor responsible for an im­ on the site (cf. Kullman 1976b, 1977a) provement in birch rejuvenation from seed, in the The increase in the rate of melting of the snow, particular types of localities considered here , in consequence of the climatic amelioration, since the mean snow depth is ea 1 m or more and ought in principle to have reduced the degree of thus the stems do not project above the snow risk of damage fr om the mechanical effects of surface until they are ea 10 years old. If frost­ snow pressure for already established birches drought had been a limiting factor prior to 1915/ 16 (see Figs. 15 and 16). a broad belt of birch shrubs would have been present on all such slopes above the PTL (cf. Wardle 1974) . There is no evidence that such was Solifluction ever the case. Another factor, which is also correlated with the depth of the snow cover and which needs to be considered in relation to the rise in the birch Ground vegetation tree-limit during the firsthalf of the present cen­ If we take a look at type of ground vegetation in tury, is solifluction , a phenomenon which occurs which those birches which became established on hillslopes of which the upper soil layers be­ after 1915/16 are growing today, we find that the come saturated with water during the greater part majority are situated in that part of the ecological of the vegetation period because downward gradient 'windexposed-snowpatch' which is do­ drainage is prevented by the frozen state of the minated by Vaccinium myrtillus or Betula nana­ underlying soil layers (Lundqvist 1969) . Empetrum hermaphroditum. The field layer in According to Sernander's (1905) investigation question consists of a rather heterogeneous plant at Hamrafjallet (locality 191), the position of the assemblage in which Solidago virgaurea, Trienta­ local forest-limit was related to some degree to Lis europaea, Viola bijlora, Deschampsia .flex­ the lower-limit of active solifluction on the hill­ uosa, Lycopodium annotinum and the lichen slope. A comparison of Sernander's (op .cit.) Nephroma arcticum are fairly frequently present . description with present-day conditions shows This vegetation type most closely corresponds to that the intensity of solifluction there has de­ that of Smith's (1920) 'moss-rich bilberry heath'. creased strongly and that birch trees have be­ Smith's (1957) studies, within part of the investi­ come established on ground which was formerly gated area, on the vegetational changes between subject to solifluction. 1919 and 1950, as revealed by repeated line !ran­ The surface and subsoil creep which consti­ sects , indicate that it was precisely the 'moss-rich tutes the phenomenon termed solifluction must in bilberry heath' and the 'moss-rich Betula nana­ principle constitute a great strain on the rooting Empetrum heath' which increased their area at the system of the birch. Hogbom ( 1914), for instance, expense of such communities as Nardus heath, reports having seen birches on Vargtjarnstoten Anthoxanthum grass-heath and Carex bigelo­ (locality 110 or 111) which had been killed off by wii heath. These grass-heath and sedge-heath solifluction. Solifluction ought nevertheless only communities all demand a snow cover of longer to effect the earliest colonisation and establish­ duration than that tolerated by the dwarf-shrub ment stages of birch to a minor degree, (cf. Kallio heaths which have replaced them. By means of & Makinen 1978) whilst presenting a considerable comparative vegetational analyses, Nordhagen danger to larger trees and shrubs with a well- (1928) has shown that a similar development is

Acta phytogeogr. suec. 65 Change and stability of birch tree-limit in the Scandes 105

the most likely response to an amelioration of the come established in the interstices between the climate . steadily shrinking Nardus tussocks. In some localities a disharmonious element of Generally speaking, it is probable that seed more or less typical snowbed species occurs, e.g. germination and seedling establishment have Alchemilla alpina, Gnaphalium supinum, Lyco­ been favoured in this way in habitats which are podium alpinum, Rumex acetosa ssp. lapponi­ usually influenced by meltwater during the sum­ cus, Sibbaldia procumbens. In Torne Lappmark, mer, and where drought never represents a limit­ in northern Sweden, Sonesson & Lundberg ing factor for the colonisation phase of birch. (1974) have found a similar vegetation in localities At quite a number of localities, during the pre­ which have fairly recently been invaded by birch. sent century, newly-established birches could be The presence of such species indicates that the found growing in metre-high and dense thickets vegetation of these areas has only relatively re­ of willows (Salix spp.) and/or of Juniperus com­ cently changed from a type which was more munis (see Fig. 36). According to Smith (op.cit.) adapted to a snow cover of longer duration than the combined area of such thickets remained that experienced at the present-day. Watt & more or less stable during the period 1919-1950. Jones (1948), from their studies of snowbed com­ That the Salix thickets, to a considerable extent, munities in the Scottish Highlands, thought that changed from a herb-rich to a grass-rich type changes in the relative dominance of fl!ardus during the same period, is considered to have stricta, Carex bigelowii and Deschampsia flex­ been due to the gradual diminution in the supply uosa were detectable, as a response to the recent of meltwater which took place. Areas of bare soil � periodic fluctuations in the duration of the snow are always to be found in places within these cover. McVean & Ratcliffe (1962), consider that thickets , so that the explanation for the birch the decline in Nardus stricta in Scotland is due colonisation is probably to be sought for in rather to the decrease in soil moisture than to any changed soil temperature and/or soil moisture of the other effects correlated with a shortening conditions, rather than in a lessening of plant of the duration of the snow cover. competition. Regarding the conditions for germination and The reduced illumination conditions found seedling establishment of birch in Nardus heath, within the Salix thickets are not considered to be Henning (1895), Soyrinki (1938) and Gj aerevoll a limiting factor for seed germination and seedling (1956) all maintain that the roots of birch seed­ establishment in such pla�es (cf. Resvoll-Holm­ lings have great difficulty in penetrating the thick sen 1928; Sarvas 1950; Black & Wareing 1955). humus layer in closed swards of Nardus, whereas The juvenile birches which grow up in this type Resvoll-Holmsen (1928) and Henning (op.cit.) of vegetation are probably well-protected from have found that conditions are quite favourable the ill-effects of mechanical pressure from the wherever the Nardus sward is less dense. overlying snow cover by the encircling shrubs of The Nardus sward is regularly interrupted by Salix spp. and/or Juniperus communis (cf. Holt­ small patches over which mosses form the domi­ meier 1974) . nant plant coummunity (cf. Gj aerevoll op.cit.). These patches represent areas subject to regular local flooding during the snow-melt period and it Characteristic habitat features of localities with no is conceivable that these weak points in the recorded rise in tree-limit otherwise closed sward may be colonised by Duration of snow cover birch during climatic periods in which meltwater supplies diminish. It is known that moss-carpets It has been demonstrated that a characteristic may be favourable substrates for birch seed ger­ feature of those localities at which little or no mination (e.g. Vaartaja 1954; Kinnaird 1974). In altitudinal shiftin the tree-limit was recorded, is a any case, during the driest summers the result relatively sparse snow cover and a relatively ear­ would have been an opening-up of the vegetation ly onset of the snow-free period. cover, whereby tree seedlings, including those of At the present-day, any appreciable meltwater birch, should have been able to colonise and be- influencehas already ceased long before the birch

Acta phytogeogr. suec. 65 106 Le if Kullman comes into leaf. Thus the relatively late disappear­ which receive a deep snow cover, and at which in ing of the snow during the very fi rst decades of fact the tree-limit has risen (Faegri 1934; Soyrinki this century was by no means so late that an 1938; Mannerfelt 1945; Retzer 1974) . Localities excess of meltwater was then a factor controlling with a shallow snow cover, generally speaking, vegetational composition. In all probability, a therefore experience difficulty in retaining their pronounced aridity during summer prevailed here already inconsiderable supply of soil water, be­ even before the start of the climatic amelioration, cause of the relatively shallow depth of the soil the effect of which should have been to fu rther there and its unfavourable (coarse-grade) texture increase the aridity during summer. This could (cf. Retzer op. cit.). In addition, as shown above, only have involved a deterioration in the habitat­ such localities are restricted to piano-convex conditions for birch. landscape forms, which are subject to increased The effe ct of insufficient water supply is pro­ insolation and to wind exposure, both of which bably most detrimental during the early stages of further increase the natural soil aridity (cf. Frodin the life-cycle of birch (cf. Jenssen 1947 ; Tranquil­ 1916). Gaiser (1951) has shown that for Quercus lini 1957). Admittedly, fe w studies have yet been alba in Ohio, the negative effect, on growth in made on seed germination and seedling estab­ tree height, of a shallow soil cover is reinforced lishment of birch in mountainous areas, but both on piano-convex landscape features, compared to these stages in all likelihood require an ample elsewhere. supply of soil moisture for their success (Heikin­ In his report on investigations into the chrono­ heimo 1915; Linkola 1930; Sarvas 1937; B�rset logy of the retreat of the inland ice sheet in the 1962; Kinnaird 1974) and a not too-impoverished region presently under discussion, Eriksson subs trate (Perttula 1941). Vaartaja (1954) empha­ (1914) drew attention to the fact that the birch sizes that Betula pubescens is extremely suscept­ seemed unable to establish itself on sites where ible to soil drought just after germination . Very the finer fractions of the morainic deposits were high values fo r seedling mortality have been re­ absent. He considered that the texture of the corded from wind-exposed localities subject to mineral soil was an important factor to bear in pronounced summer-drought (Soyrinki 1938; mind when considering the question of the altitu­ Perttula op.cit.). dinal tree-limit for birch. At certain localities in the investigated area, at which little or no rise of the tree-limit was record­ Depth of surface deposits ed the importance of the 'water-supply-morain­ The distribution of the unconsolidated surface ic soil' type factor complex was quite clearly deposits in the mountains to a certain degree ex­ visible, for example on the N-facing slope of hibits the same pattern as the distribution of Trondfjall (locality 95) where a narrow natural snow. The morainic and fluvioglacial deposits, 'alh�e' of sturdy birch trees runs up towards the although carried by glacier, water, and wind tree-limit on both sides of a small stream. The movements respectively, are generally deeper in streambed is only slightly incised into the hillside terrain depressions than on elevations, and to and does not itself give rise to any particularly leeward of obstacles, i.e.: accumulations are increased depth of snow cover thereabouts . On deepest in basins and at the foot of E- and SE-fac­ either side of the birch allee the morainic soil ing slopes. As a general rule the depth of the cover is very thin and the ground very dry and surface deposits in mountain regions decreases there is virtually no tree growth at all. The bir­ from the valley bottom towards the mountain ches in the alle are undoubtely just as exposed to summits (Tanner 1914; Lundqvist 1969 ; Soyez the weather as they would be at any other point in 1971). the surrounding terrain, which is gently-sloping, To a certain extent at least, in exposed locali­ has only a shallow snow cover and coarse and ties with only a shallow snow cover and a more or shallow morainic deposits. The only habitat fac­ less stable tree-limit, the finerfrac tions of the soil tor which is radically different in the allee com­ will have been removed by meltwater and wind pared to the surrounding areas is the water supply. erosion, and re-deposited in those localities In the immediate vicinity of the stream the stable

Acta phytogeogr. suec. 65 Change and stability of birch tree-limit in the Scandes 107 and ample water supply has enabled the birches crop of tree-limit trees had been shed from the to establish and to grow into 7-8 m high trees, catkins during the autumn, whilst in other years a whereas only a short distance away just a few large quantity of seed remained in the catkins low-growing birch shrubs are capable of growing. until well on into the winter or spring (cf. also The above-mentioned example supports Fro­ Kallio & Makinen 1978). din's (1916) conclusion, based on his experiences According to the information available in litera­ in Lule Lappmark in northern Sweden, that the ture a certain proportion of the birch seed shed local water supply is of vital importance in germinates already during late-summer and au­ explaining the regional variations seen in the alti­ tumn, but the major part of the seed crop probab­ tudinal birch tree-limit, although this hypothesis ly overwinters under the snow cover and germi­ has been disputed by Tengvall (1920) . nates during the following spring (Sylven 1906; Leach & Polunin (1932) considered that the Heikinheimo 1915; Faegri 1958; Billings 1974). limiting factors for the distribution of birch in Overwintering seems to lower the minimum Finnmark in northern Norway were edaphic, ra­ temperature needed for successful germination ther than directly climatic. The importance of the (Mork 1950) . water supply and its permanency in conditioning In the case of autumn seedlings, these general­ the ultimate altitudinal limits for vascular plants ly may have great difficulty in surviving through in general has been claimed by Webster (1961). the winter, because they are insuffi ciently hardy Gorchakovski (1965) maintains that the forest-li­ (cf. Perttula 1941; Haugberg 1962). Investigations mit in the U ral Mountains is only primarily clima­ made in Scotland have shown that low tempera­ tically conditioned in areas in which there is a tures in winter can have a deleterious effect on sufficiencyof fine-grade mineral matter in the soil seedling development in areas with a poor snow (cf. Ellenberg 1966). cover (Me Vean & Ratcliffe 1962) .

Ground-level temperatures and fr ost-heave Frost-drought Near the tree-limit, the very high ground-level It is rather unlikely that a relatively shallow snow temperatures attained in summer (cf. Aulitzky cover could have been responsible for the failure 1961 ; Wardle 1974) and the occurrence of fr ost­ of the tree-limit to rise at the present localities, heave (cf. Vaartaja 1954) in certain of the habitats due to a permanent or increased risk of fr ost­ with only a shallow snow cover are further fac­ drought or mechanical erosion of shoots by ice tors which might selectively have hindered recent and snow. These latter factors are often thought birch colonisation there. to be major obstacles to birch survival in habitats Linteau ( 1948) has demonstrated that seedlings with a shallow snow cover (cf. e.g. Elkington & of yellow birch (Betula lutea), in Quebec, Cana­ Jones 1974). da, to a high degree were killed or damaged by According to investigations made on conife­ heat during summer, especially on exposed sites rous tree species in Central Europe (Michaelis (cf. also Haig 1936) . The same risk should be 1934; Baig et al . 1974) frost-drought damage, to considered to be relatively high in habitats with those parts of the plant which project above the little snow-cover within the present investigation snow cover, occurs very frequently near the area. Localities with a late snow-melt are not tree-limit and determines its ultimate position. exposed to this danger to the same degree, due to Experimental investigations on Mt. Washington, the cooling effect of the evaporation of the snow New Hampshire, on Picea mariana, Abies bal­ meltwater (cf. Holway & Ward 1963). samea and Betula papyrifera, however, indicate that winter desiccation caused by high wind velo­ cities when the soil is frozen is by no means a Seed dispersal, germination and establishment universal lethal factor at the tree-limit (Marchand My own observations during the 1970's concern­ & Chabot 1978). It is suggested that the position ing the time of seed dispersal, varied greatly of the tree-limit in that area is explained in terms from year to year. In some years most of the seed of reproduction biology and demography.

Acta phytogeogr. suec. 65 108 LeifKullm an

My own field studies in the investigated area Scandinavia only very exceptionally exhibit during the winter period have shown that it is by morphological abnormalities directly attributable no means uncommon to find that birches of tree­ to frost-drought damage, e.g. a 'table-top' shoot size or less, growing at the tree-limit, have the system (cf. Kihlman 1890; Fries 1913), or the major part of their shoot systems and buds ex­ presence of shoots which have died back to the posed to wind and weather above the snow cover level of the snow cover. The follow-up studies throughout the winter. Often only the unbranched made on individual birches growing near the lower parts of the birch stems receive any 'pro­ tree-limit within the investigated area did not tection' from the snow (cf. Leach & Polunin yield indications, either, that frost-drought repre­ 1932). sented a serious mortality factor, for well-estab­ It frost-drought were to represent a primary lished stems at least. reason for the absence of birch trees above a certain altitude, then there ought to be a belt of Mechanical damages shrub birches, successively lower in height, Brich shoots which stick up 0-50 cm above the above the tree-limit. Furthermore, these shrubs snow-cover in winter are sometimes subject to ought for the most part to be completely buried mechanical erosion by ice and snow crystals car­ beneath the snow during the winter and to be ried by the wind along and just above the snow shaped in conformity with the morphology of the surface (cf. Samuelsson 1917; Werenskiold 1925). snowdrift s (cf. Wardle 1974). Such a belt of birch Occasionally, nearly all the low-growing basal shrubs is not present in either that part of the shoots are debarked in this way, although despite mountain chain covered by the investigated area, this a few scattered shoots often somehow ma­ or e.g. in Lule Lappmark in northern Sweden nage to survive and grow to tree height. The phe­ (Frodin 1916). The present investigation has nomenon, in my experience, is rather uncom­ shown that in most cases (ea 80 %) the present mon, in both space and time, and can hardly have tree-limit (TL) and the species limit (SL) coincide. any direct influence on the local position of the In any case, as a deciduous species, the birch tree-limit (cf. Turner 1968 ; Holtmeier 1974) and should be little liable to damage from frost­ has nothing at all to do with the recent altitudinal drought, and as far as I am aware no such damage changes in the tree-limit. has been convincingly reported for birch growing in the mountainous regions of Scandinavia. On the other hand it has been reported for other deci­ Influences of reindeer duous tree species growing at the tree-limit in The effects of reindeer (Rangifer tarandus) graz­ other parts of the world e.g. Nothofa gus solandri ing and trampling represent a fu rther factor which (Wardle 1972) and Larix europaea (Nageli 1969: must be taken into account in localities which Holtmeier 1974). receive only a shallow snow cover in winter. Dur­ Investigations on Betula verrucosa in Central ing the spring calving season the reindeer herds Europe made by Geurten (1950), showed that are greatly attracted by bare patches of ground transpiration occurred through the periderm and and may cause considerable erosion of soil and lenticels, even in wintertime, and then especially vegetation (e.g. Warenberg 1977). on the S-facing and lower parts of the stems. The statistical treatment of the tree-limit data Therefore, it cannot be entirely ruled out that a from the investigation area as a whole yielded no reduction of transpiration by the snow cover has support for the view that the localities at which a positive value, especially for the survival of the little or no rise in the tree-limit was recorded were lower stems and of the initial seedling stages. those which were previously more affected by Whether this is really a controlling factor for Lappish activities, including reindeer grazing, birch establishment in this type of habitat or not, than the other localities. can only be finally decided experimentally, al­ Since both localities with a very early snow­ though the facts presented in the present investi­ melt and localities with long lasting snow cover gation argue against this possibility. Further­ are attractive to reindeer, although at different more, birches growing in the tree-limit ecotone in times of the year, the difference in the tree-limit

Acta phytogeogr. suec. 65 Change and stability of birch tree-limit in the Scandes 109 reaction between these two contrasting types of 2. The basic cause for the rise in the tree-limit habitats, has apparently no connection with even­ was the increase in the frequency of extremely tual changes in the degree of reindeer activity. warm summers, in which respect the decade To sum up, it has been established that the 1930--39 was wholly unique. absence of any significantrise in the tree-limit at 3. There are no indications that the cessation of localities characterized by a shallow snow cover human impact was the primary cause of the alti­ is correlated, according to the evidence presented tudinal displacement. above, with the pronounced aridity of the soil 4. The decisive ecological difference between which characterizes these localities and which those localities at which a rise in the tree-limit becomes more and more pronounced in the occurred, and the rest, lies in differences in the course of the summer. The general increase in depth and duration of the snow cover. The former mean summer temperature during the first half of localities are situated in typical snow accumula­ the present century, mentioned above, will have tion areas, the latter in deflation areas. exacerbated this propensity to summer drought at 5. The degree of displacement recorded was pro­ these localities. Thus the ecological requirements portional to the extent and duration of the snow for successful germination and seedling estab­ cover. lishment will have either deteriorated or remain­ ed stable during the same period of time. 6. Depth and distribution of snow cover and. of The altitudinal position of the birch tree-limit surface deposits are interrelated, together form­ seems to a high degree to be determined by those ing a factor-complex which determined the de­ environmental factors which primarily affect the gree of change of the bir�h tree-limit and its local habitat conditions for seed germination and the differences. The tree-limit at all the investigated seedling stages. The same conclusion has been localities is basically controlled by the interaction drawn regarding the arctic tree-limit (Sochava of edaphic and climatic factors. 1940 [cited in Tikhomirov 1962]; Tikhomirov If the tree-limit was determined by the level at 1961, 1962, 1970). which the local climate no longer is favourable Those factors which lead to mortality among enough to support a sufficient net assimilation well:.established saplings and trees are not neces­ for tree-growth, then one would have expected to sarily the same ones which condition the ultimate find that the tree-limit rise would have ceased position of the tree-limit (cf. Sochava op.cit.; about 1950, at the time of the culmination of the Wardle 1974). This is further emphazised in a present climatic fluctuation. However, the seed­ fascinating study of the local migrations of spruce lings established by that time have continued to clones at the tree-limit in the Rocky Mountains, grow into trees· (stems � 2 m high) and therefore, USA, by Marr ( 1977), who showed that seed technically, the tree-limit has continued to rise at germination and seedling establishment are de­ most places even after 1950 (1950--1975), although pendent upon entirely different habitat factors there has been practically no new birch colonisa­ than those which control the growth and subse­ tion (i.e. seed germination with seedling estab­ quent vitality of the shoots of successfully estab­ lishment) at higher altitudes since 1950 anywhere lished saplings and young trees, a point also made in the investigated area. by Larsen (1965) and in regard to the palaeohisto­ 7. At those localities at which a rise in the birch ry of spruce in Fennoscandia by Tallantire (1972, tree-limit was recorded, tile main effect of the 1977). more favourable summertime \veather was a more rapid melting-away of the reiatively-deep win­ ter snow cover, which resulted in an earlier dry­ Summarised conclusions ing-out of the soil during the vegetation period. There are many indications which .suggest that 1. At ea 75 % of the investigated localities the the birch expansion was conditional upon the in­ altitude of the birch tree-limit increased. At the crease in surface soil temperature and the de­ remaining localities the tree-limit remained un­ crease in soil moisture which occurred as a result changed between 1915/16 and 1975. of the diminished snow meltwater supply.

Acta phytogeogr. suec. 65 110 LeifKullm an

Seed germination seems to have been favoured colonisation is possible (i.e. the 'potential tree­ mainly by the increase in soil temperature , whilst limit' at any period). Productivity studies of trees seedling establishment has obviously been fa­ growing in the tree-limit ecotone therefore, can voured by both the warming up and the drying­ never yield any definite answers about the true out of the surface soil. nature of the factors which determine the position The unique, long-term, series of extremely of the birch tree-limit. warm summers during the decade 1930--39 pro­ It is most important that future investigations vided very good growth conditions for the newly­ should be so designed as to separate the differing colonised birch seedlings and enabled them to ecological effects of the depth and the duration of mature sufficiently to survive the subsequent re­ the snow cover. turn of less favourable conditions. 13. On a basis of the research results obtained so 8. The absence of any rise in the birch tree-limit far it is interesting, from a palaeoecological view­ at ea 25 % of the investigated localities is related point to try to form some opinion about the prob­ to the existence there of permanently unfavour­ able effects of different types of climatic change able conditions for seed germination and seedling on the altitudinal position of the birch tree-limit . establishment. The most probable operative fac­ It is now quite clear that even quite an appreci­ tors were damage by drought and/or high air tem­ able rise in the mean temperature of the sum­ peratures during the vegetation period. mer-months (June-August) only results in a rise Nothing suggests that a shallow winter snow in the tree-limit at typical snow-accumulation lo­ cover per se should present any hindrance for the calities. Even here it may be restricted by the growth of tree-birches. absence of a suitable depth or particle-size com­ position of the surface soil deposits. Further­ 9. No unequivocal evidence was found for the more, appreciable increases in mean summer hypothesis that frost-drought or the mechanical effects of wind-driven snow and ice particles, temperatures will lead to a decrease in the supply represent factors limiting the altitudinal tree-limit of snow meltwater and in soil humidity, which can be expected to hamper any further rise in the for birch. tree-limit and ultimately even to lead to a fall, 10. For birch stems growing in the tree-limit eco­ perhaps even to the replacement of the subalpine tone, and which have attained tree height, or birch belt by other tree species e.g. pine. almost so, the most important lethal factor is the The effects of a radical diminution in solid pre­ mechanical effect of the weight of the snow cover cipitation should be roughly the same as those during the period of the snow melt. The more already described above. rapid disappearance of the snow cover during the A long-term decline in mean summer tempera­ culmination phase of the climatic fluctuation re­ tures would be expected, first and foremost, to sulted in a reduction of the above factor, without lower the tree-limit in pronounced snow accumu­ which a rise in the tree-limit, of the proportions lation localities, whilst at snow deflationlo calities recorded, would probably have been impossible. the tree-limit would probably remain unchanged 11. In general terms the tree-limit, like the vege­ for a longer period of time. tation cover as a whole, may be considered as Therefore, when considering the tree-limit in relatively unstable in snowy, locally maritime, palaeoecological terms, one must expect to find areas, because in such areas the spatial variation that climatic fluctuations do not everywhere, or in the depth of the snow cover is a very important simultaneously, lead to the same pattern of vege­ differentiating factor and one which reacts rela­ tational change. tively soon to any change in the thermoclimate . Attempts to reconstruct the course of the post­ 12. The problem of the birch tree-limit should be glacial climate by palaeoecological methods, i.e. studied in the future by such methods as popula­ from birch tree-limit change, can therefore be tion-ecology studies of the earliest stages in the expected to be most successful in locally-mari­ life-cycle, since it is obviously possible for bir­ time areas, characterised by a heavy accumula­ ches, once established, to continue to grow and tion of snow, for the reasons outlined under point survive at a higher altitude than that at which 11 above.

Acta phytogeogr. suec. 65 References

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1919. Hibodbebyggelsen i Kall och Offerdal.-Ge­ 1977. Retarded growth of a geometrid larva after ogr. Ann. 1. mechanical damage of its host tree.-Ann. Zool. - 1927. Bygdestudier i norra Jamtland.-Lunds Univ. Fenn. 14. Arsskr., N.F. Avd. 1, 24: 1. Haukioja, E. & Heino , J. 1974. Birch consumption by - 1929. Om fa bodbebyggelsens utbredning och olika reindeer (Rangifer tarandus) in Finnish Lapland.­ typer i Europa.-Svensk geogr. Arsbok 1929. -Rep. Kevo Subarctic Res. Stat. 11. - 1952. Skogar och myrar i norra Sverige i deras Havranek, W. 1972. Uber die Bedeutung der Boden­ funktion som betesmark och slatter.-Instituttet f. temperatur fiir die Photosynthese und Transpira­ Sammenlignende Kulturforskning Ser. B, 66. tion junger Forstpflanzen und fiir die Stoffproduk­ Frydendahl, K. 1978. Increase in solar radiation about tion an der Waldgrenze.-Angew. Bot. 46. 1915.-Danske Meteor. Inst. Klimat. Medd. 4. Hedberg, E. 1939. Storlien nu och fo rr.-Pa Skidor Gaare, E. & Skogland, T. 1975 . Wild reindeer food 1940. habits and range use at Hardangervidda.-In: Fen­ Heikinheimo, 0. 1915. Kaskiviljelyksen vaikutus Su­ noscandian tundra ecosystems, Part 2: Animals and omen metsiin.-Acta Forest. Fenn. 4:2. system analysis. Ed. by F.E. Wielgolaski. Berlin­ Heino, R. 1978. On climatic changes in Finland.-In: Heidelberg-New York. Danske Meteor. Inst. Klimat. Medd. 4. Gaiser, R.N. 1951. Relation between topography, soil Hellbom, P.J. 1884. Norrlands lafvar.-Sv. Veten­ characteristics and the site index of White Oak in skapsakad. Handl. 20. southeastern Ohio.-Central States Forest Expe­ Helle, R. 1966. An investigation of reindeer husbandry riment Station. Technical Paper 121. Ohio . in Finland.-Fennia 95:4. Geijerstam, G. af 1891. Kulturkampen i Herjedalen. Henning, E. 1887. Vaxtfysiognomiska anteckningar

Fran striden mellan lappar och bofaste .­ fran vestra Hiirjedalen med sarskild hiinsyn till Stockholm. Hymenomyceternas forekomst inom olika vaxt­ Geurten, I. 1950. Untersuchungen iiber den Gaswech­ formationer.-Bih. Sv. Vetenskapsakad. Handl. 13. sel von Baumrinden.-Forstwiss. CentBl. 1950. 1889. Forstligt botaniska studier i Jemtland Gj aerevoll, 0. 1956. The plant communities of the 1888.-Tidskr. skogshushalln. 1889. Scandinavian alpine snow-beds.-Norske Vidensk. 1895. Studier ofver vegetationsforhallandena i Selsk. Skr. 1956, 1. Jemtland ur forstlig agronomisk och geologisk syn­ Gorchakovskii, P.L. 1965. An essay on the phytoge­ punkt.-SGU, Ser. C, 145. ographical subdivision of the Uralian Highlands.­ Hesselberg, Th . & Birkeland, B.J. 1940. Sakulare In: Studies on the flora and vegetation of high­ Schwankungen des Klimas von Norwegen.-Ge­ mountain areas . Ed. by V. N. Sukachev. Academy ofys. Publ. 14. of the Sciences of the U.S.S.R. Jerusalem. Hintikka, V. 1963. Uber das Grossklima einiger Pflan­ Haglund, E.E. 1905. Ur de hognordiska vedvaxternas zenareale in zwei Klimakoordinatensystemen dar­ ekologi.-Uppsala. gestellt.-Ann. Bot. Soc. Vanamo 34. Haig, I.T. 1936. Factors controlling initial establish­ Hisinger, W. 1819. Anteckningar i physik och geognosi ment of Western White Pine and associated spe­ under resor i Sverige och Norrige . I. Jemtland och cies.-Yale Univ. School of Forestry , Bulletin No. Dalarne .-Upsa la. 41. New Haven. 1820. Anteckningar i physik och geognosi under Hallinder, A. 1977. Fabodar i Klovsjo.-In: Nordiskt resor i Sverige och Norrige. 11. Herjedalen.-Upsa­ fa bodvasen. Forhandlingar vid fa bodseminarium i la. Alvdalen, Dalarna, 1-3 sept. 1976. Stockholm. Hj elmqvist, S. 1966. Beskrivning till berggrundskarta Hallstrom, G. 1931. Den tidigaste jarnaldern i Dalar­ over Kopparbergs lan.-SGU, Ser. Ca, 40. na.-Dalarnas Hembygdsbok 1931. Hogbom, A.G. 1897 . Nagra anmarkningar om de is­ - 1944, Gravfaltet pa Vivallen i Funasdalen.-Forn­ damda sj oarna i Jemtland.-GFF 19. vardaren VIII-IX. - 1920, Geologisk beskrivning over Jamtlands Hamberg, A. 1907 . Die Eigenschaften der Schneedecke lan.-SGU, Ser. C, 140. in den lapplandischen Gebirgen.-Naturwiss. Un­ Hogbom, B. 1914. Uber die geologische Bedeutung des tersuch. d. Sarekgeb. in Schwed.-Lappland , 1:3. Frostes.-Bull. Geol. Inst. Univ. Upsala 12. Hamet-Ahti, L. 1963 . Zonation of the mountain birch Hoglund, N.H. & Eriksson, B.R. 1973. Forvildade forests in northernmost Fennoscandia.-Ann. Bot. tamrenars inverkan pa vegetationen inom Lovhogs­ Soc. Vanamo 34. omradet.-Statens Naturvardsverk PM 358. Hare, F.K. 1971. Snow-cover problems near the arctic Hogstrom, P. 1741. Beskrifning ofwer de til Sweriges tree-line of North America.-Rep. Kevo Subarctic krona lydande lapmarker.-Stockholm. Res. Stat. 8. Holmgren, A. 1912. Studier ofver nordligaste Skandi­ Haugberg, M. 1962. Grunnlaget for skogens naturliga naviens bj orkskogar.-Stockholm. foryngelse.-ln: Skogbruksboka. Oslo. Holtmeier, F.-K. 1974. Geookologische Beobachtung­ Haukioja, E. 1976. Does birch defend itself actively en und Studien an der subarktischen und alpinen against herbivores?-Rep. Kevo Subarctic Res. Waldgrenzen in vergleichender Sicht.-Wiesba­ Stat. 13. den.

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Holway, J.G. & Ward, R.T. 1963 . Snow and meltwater Johannessen, T.W. 1942. Klimatet pa R��Sros.-In: effects in an area of Colorado Alpine.-The Ameri­ Rj1Sros-BokaTr ondheim. can Midland Naturalist 69. 1970. The climate of Scandinavia.-ln: Climates of - 1965. Phenology of alpine plants in Northern Colo­ Northern and Western Europe. World survey of rado.-Ecology 46. climatology 5. Ed. by C.C. Wallen. Amsterdam­ H��Srbye, J .C. 1861. Et strj1Sg af riksgraendsen.-Nyt London-New York. Mag. Naturvidensk. 11. Johnson, B. 1965. Medeltemperaturens och vegeta­ Hultblad, F. 1968. bvergang fran nomadism till agrar tionsperiodens nutida fo randringar i Sverige.-Un­ bosattning i Jokkmokks socken.-Lund. published manuscript, Geogr. inst. Stockholm. Huse, S. 1965. Strukturformer hos urskogsbestand i Jordan, W. 1917. Barometrische Hohentafeln fiir Luft­ 0vre Pasvik.-Meld. Norg. Landbr. Hj1Sgskole44. driicke zwischen 630 mm u. 765 mm u. f. Lufttem­ Huss, E. 1959. Utredning rorande renbetestrakter fo r peraturen zwischen oo und +35°. Die ersten sechs lapparna i Jamtlands och Kopparbergs lan.-Mi­ Temperaturgrade neu hinzugegefiigt v. Prof. Dr. E. meographed. Hammer.-Stuttgart. Hustich, I. 1937. Pflanzengeographische Studien im Kallio, P. & Lehtonen J. 1973. Birch forest damage Gebiet der niederen Fj elde im westlichen finni­ caused by Oporinia autumnata (Bkh .) in 1965-66 in schen Lappland.-Acta Bot. Fenn. 19. Utsjoki, N Finland.-Rep. Kevo Subarctic Res. 1940. Nagra vaxtgeografiska forskningsuppgifter i Stat . 10. Lappland.-Mem. Soc. Fauna Fl. Fenn. 16. 1975. On the ecocatastrophe of birch forests caused 1947. Climatic fluctuations and vegetation growth by Oporinia autumnata (Bkh.) and the problem of in northern Finland during 1890-1939.-Nature reforestation.-In: Fennoscandian tundra ecosys­ 160. tems, Part 2: Animals and system analysis. Ed. by 1949. On the correlation between growth and the F.E. Wielgolaski. Berlin-Heidelberg-New Uork. recent climatic fluctuation.-Geogr. Ann. 31. Kallio, P. & Makinen, Y. 1978. Vascular flora of Inari 1958. Onthe recent expansion of the Scotch Pine in Lapland. 4. Betulaceae.-Rep. Kevo Subarctic northern Europe.-Fennia 82. Res. Stat. 14. 1978. A change in attitudes regarding the import­ Karlen, W. 1973. Holocene glacier and climatic vari­ ance of climatic fluctuations.-Fennia 150. ations, Kebnekaise Mountains, Swedish Lap­ Hvarfner, H. 1961. Bygd kring Lossen.-In: Lossen. land.-Geogr. Ann. 55 A. Liv och arbete vid en Harjedalssjo. Lund. Karlen, W. & Denton , G .H. 1975. Holocene glacial Hiilphers, A. A:son 1762. Dagbok ofwer en resa ige­ variations in Sarek National Park, northern Swe­ nom de, under Stora Kopparberg hofdingedome ly­ den.-Boreas 5. dande lahn och Dalarne ar 1757.-Wasteras. Kellgren, A.G. 1892. Agronomiskt-botaniska studier i 1777. Samlingar till beskrivning ofver N orrland. norra Dalarna aren 1890 och 1891.-SGU, Ser. C, Tredje samlingen, om Herjedalen.-Westeras. 119. 1893. Agronomiska studier i Harjedalen 1892.­ In der Gand, H. 1968a. Aufforstungsversuche an einen Landtbruksakad. Handl. och Tidskr. 32. Gleitschneehang.-Mitt. Schweiz. Anst. forstl. Kellgren, A.G. & Nilson, L.F. 1893 . Undersokning af Versuchswes. 44. svenska foder- och betesvaxter.-Ibid. 32. 1968b. Aufforstungsversuche an einen Gleitschnee­ Kihlman, A.O. 1890. Pflanzenbiologische Studien aus hang. Ergebnisse der Winteruntersuchungen 1955/ Russisch Lappland.-Acta Soc. pro Fauna et Flora 56 bis 1961/62.-Mitt. Schweiz. Anst. forstl. Ver­ Fenn. 6:3. suchswes. 44 . Kilander, S. 1940. Fabodvasendet i Undersakers sock­ Jalas, J. 1950. Zur Kausalanalyse der Verbreitung eini­ en.-Unpublished manuscript. ger nordischen Os- und Sandpflanzen.-Ann. Bot. - 1942. Fabodvasendet i Are socken.-Unpublished Soc. Vanamo 24. manuscript. Janson, S., Biornstad M. & Hvarfner H. 1962. Jamt­ - 1950. Det lagalpina baltets ovre grans och underbal­ lands och Harjedalens historia. Arkeologisk inled­ ten i ostra Sydskanderna.-SBT44 . ning.-Stockholm. - 1955. Karlvaxternasovre granser pa fjall i sydvastra Jansson, 0. 1951. Fj allsocknarna Tannas och Stor­ Jamtland samt angransande delar av Harjedalen sj o.-In: Natur i Halsingland och Harjedalen. Ed. och N orge .-APhS 35. by T. Arnborg & K. Curry-Lindahl. Goteborg. - 1965. Alpine zonation in the southern part of the Jarnefors, A. 1932. Saterliv i vastra Harjedalen.-In: Swedish Scandes.-APhS 50. Bilder fran vastra Harjedalen. Sveg. Kinnaird, J.W. 1968. Ecology of birch woods.-Proc. Jensen, R. 1977. Hallbilder och fangstmiljo-STF:s Bot. Soc. British Isles 7. Arsskr. 1977. - 1974 . Effect of site conditions on the regeneration Jenssen, J. 1947 . Litt om vernskog,-saerlig i Nord­ of birch (Betula pendula Roth and B. pubescens Norge.-Tidsskr. Skogbr. 55. Ehrh.). J. Ecol. 62. Jirlow, R. 1945. Ur folklivet vid slutet av 1800-talet.­ Kj elvik, S. 1973 . Biomass and production in a willow In:Sarna-Idre 300 ar. En hembygdsbok. Falun. thicket and a sub-alpine birch forest, Hardanger-

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Lundqvist, Jim 1968. Plant cover and environment of Kronfuss, H. 1967. Schneelage und Ausaperung an der steep hillsides in Pite Lappmark.-APhS 53 . Waldgrenze.-Mitt. forstl. Bundes-Versuchsanst. Lutz, H.J. 1959. Aboriginal man and white man as Wien 75. historical causes of fires in the boreal forest, with Kvarning, L.A . 1961. Dj urens fo da.-In: Lossen. Liv particular reference to Alaska.-Yale U niv. School och arbete vid en Harjedalssjo. Lund. of Forestry, Bulletin 65. Laitakari, E. 1934. Koivum juuristo.-Acta Forest. Liibeck, R. 1920. Betesdjurens skadegorelse i sko­ A Fenn. 41. gen.-Svenska Betes- och Vallforen. rsskr. 1920. Lamb, H.H. 1965. Britain's changing climate .-In: Lysgaard , L. 1963. On the climatic variation.-In: The biological significance of climatic changes in Changes of climate. Proc. of the Rome Symp. org. Britain. Ed. by C.J. Johnson & L.P. Smith. Loo­ by UNESCO and the World Meteorol. Org. Liege. don-New York. Malmstrom, C. 1951. 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Liljequist, G. 1943. The severity of the winters at Gaertn. Ill Seedling establishment.-]. Ecology 44. Stockholm 1757-1 942 .-SMHA, Medd. Ser. - 1958. Snow cover and vegetation in the Scottish Upps. 46. Highlands.-Weather 13.

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McVean, D.N. & Ratcliffe , D.A. 1962. Plant communi­ der Wald-Hainwiesen und Hainfelsenvegetation.­ ties of the Scottish Highlands.-Monographs of the -Ann. Acad . Sci. fe nnicae A 58. Nature Conservancy. I. London , H.M.S.O. Polunin, N. 1936. Plant succession in Norwegian Lapp­ Melin, R. 1943 . Nederbord och vattenhushallning inom land .-J. Ecol. 24. Malmagens fj�illomrade.-SMHI , Medd. Ser. - 1937. The birch forests of Greenland.-Nature 140. Upps. 43 . Poore, M.E.D. & McVean, D.N. 1957. A new approach Michaelis, P. 1934. Okologische Studien an der alpinen to Scottish mountain vegetation.-J. Ecol . 45 . Baumgrenze. IV. Zur Kenntnis der winterlichen Porsild , A.E. 1951. Plant life in the Arctic. Canadian Wasserhaushaltes.-Jb . wiss. Bot. 80. Geogr. J. 42. Moen, A. 1976. Slattermyrers vegetasjon, produksjon Pruitt, W.O., Jr. 1970. Some ecological aspects of og verneverdi. Forelyjpig meddelelse fra forsk­ snow.-In: Ecology and Conservation. 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Nageli, W. 1969. Waldgrenze und Kampfzone in den London. Alpen.-Hespa Mitt. 19. Rindert, B. 1975. Meteorologiska standardinstru­ Nordhagen, R. 1928. Die Vegetation und Flora des ment.-Mimeographed, Meteorol. Inst. Uppsala. Sylenegebietes. I. Die Vegetation.-Skr. Norske Robsahm, C.M. & Swab , A. 1938. Resa genom Harje­ Vidensk.-Akad. I. Mat.-naturvid. kl., 1927:1. dalen till Norge och Roros kopparverk. Ed . by H. 1943 . Sikilsdalen og Norges fjellbeiter. En plante­ Richter.-Jernkontorets Bergshist . Skriftserie 6. sosiologisk monografi.-Bergens Mus. Skr. 22. Stockholm. 1956. Vegetasjonsforskyvningen i naturparken ved Rolsted, M. 1931. Skogen og beitespyjrsmalet.­ Sylene i perioden 1920-1954 som bevis pa klimatis­ Tidsskr. Skogbr. 39. ke endringer. En fotografisk dokumentasjon.­ Rudberg, S. 1957. Odemarkerna och den perifera be­ Norske Videnskapsakad . .Arb. 1955. byggelsen i inre Nordsverige.-Geographica 33. 1964 . Vassdragsreguleringene , naturvernet og Ruden, I. 191 I. Fremstilling av en del av den skade norsk videnskap.-Aftenposten 25 mars 1964. som de svenske flytlapper og ren har voldt paa Nuorteva, P. 1963 . The influence of Oporinia autumnata skogen i Tromsyj amt.-Kristiania. (Bkh.) (Lep., Geometridae) on the timber-line in Rudloff, H. von 1967 . Die Schwankungen und Pend­ subarctic conditions.-Ann. Ent. Fenn. 29. lungen des Klimas in Europe seit dem Beginn der regelmassigen Instru menten-Beobachtungen Oster, J. 1936. Pa slatterang och i lovskog. En nutids­ (1670).-Die Wissenschaft 122. skildring av foderfangsten i en fj �illby i norra Harje­ dalen.-Jamten 30. Ruong, I. 1937. Fj allapparna i J ukkasjarvi socken.­ Ostman, C.J. & Henrikson, H. 1942. Om kold och is i Geographica 3. - 1954. Om renmjolkningen pa sydlapskt omrade.­ nyare och aldre tid.-Ymer 1942 . In: Scandinavica et Fenno-Ugrica. Studier tillagna­ Perring , F.H. 1965. The advance and retreat of the de Bjorn Collinder den 22 juli 1954. Stockholm. British flora.-In: The biological significance of - 1964 . Jakkakaska same by .-Svenska landsmal och climatic changes in Britain. Ed . by C.J. Johnson & svenskt folkliv 86. L.P. Smith. London-New York. - 1969. Samerna.-Stockholm. Pershagen, H. 1969. Snotacket i Sverige 193 1-60.­ Samuelsson, G. 1917. Studien iiber die Vegetation der SMHI, Medd. Ser. A, 5. Hochgebirgsgegenden von Dalarne.-Nova Acta Perttu , K. 1972. Skogsgransens beroende av olika kli­ Reg . Soc. Scient. Ups. Ser. 4, 4:8. matologiska och topografiska faktorer.-Inst. f. Sandberg, G. 1940. Den pagaende klimatforandring­ skogsforyngring. Skogshogskolan. Rapp. o. Upps. en.-Svenska Vall- och Mosskult. Foren. Kvar­ 34. talsskr. 2. Perttu, K. & Huszar A. 1976. Vegetationsperioder, - 1958. Fj allens vegetationsregioner, vegetationsse­ temperatursummor och frostfrekvenser beraknade rier och viktigaste vaxtekologiska faktorer.-In: ur SMHI-data.-Ibid. 72. Lappvasendet-Renforskningen, Medd. 4. Uppsala. Perttula, U. 1941. U ntersuchungen iiber die generative 1960. Vadvetjakko. Serien Sveriges Nationalpar­ und vegetative Vermehrung der Bliithenpflanzen in ker.-Stockholm.

Acta phytogeogr. suec. 65 Change and stability of birch tree-limit in the Scandes 117

1963 . Vaxtvarlden i Abisko nationalpark.-In: Na­ Sochava, V.B. 1940. 0 bezlesii tundry (Tundra barren­ tur i Lappland. Del 2. Ed. by K. Curry-Lindahl. ness).-Trudy Leningradskogo Obshchestva Est­ Uppsala. estvoispytatelei 68. Sarvas, R. 1937. Kuloalojen luontaisesta metsittymi­ Sonesson, M. & Lundberg, B. 1974. Late Quaternary sesta.-Acta Forest. Fenn. 46. fo rest development of the Tornetrask area, North - 1948. Tutkimuksia koivun uudistumisesta Etela-Su­ Sweden.-Oikos 25. omessa.-Comm. Inst. Forest. Fenn . 35. SOU (Statens Offentliga Utredningar) , 1966: 12. Renbe­ - 1950. The effect oflight on the germination offorest tesmarkerna. Betankande avgivet av renbetes­ tree seeds.-Oikos 2. marksutredningen.-Stockholm. - 1952. On the flowering of birch and the quality of Soyez, D. 1971. Geomorfologisk kartering av nordvas­ seed crop.-Comm. Inst. Forest. Fenn. 76. tra Dalarna.- Stockholms univ. Naturgeogr. inst. - 1970 . Temperature sum as a restricting factor in the Forskn. rapport 11. development of forest in the Subarctic.-In: Ecolo­ Soyrinki, N. 1938. Studien iiber die generative und gy and Conservation. Ecology of the subarctic re­ vegetative Vermehrung der Samenpflanzen in der gions, UNESCO-symp . Helsinki 1966. Paris. alpinen Vegetation Petsamo-Lapplands. I. Allge­ Schove, D .J. 1954. Temperatures and tree-rings in meiner Teil.-Ann. Bot. Soc. Vanamo 11. North-Scandinavia.-Geogr. Ann. 36. - 1939. Studien i.iber die generative und vegetative Schytt, V. 1962 . N aturgeografisk fa ltstation i Kebne­ Vermehrung der Samenpflanzen in der alpinen Ve­ kajse.-Svensk Naturvetenskap 1962.-Stock­ getation Petsamo-Lapplands. 11. Spezieller Teil.­ holm. Ibid. 14. - 1967. A study of "ablation gradient" .-Geogr. Spink, P.C. 1969. Scottish snowbeds in summer Ann. 49. 1968.-Weather 24. - 1973. Glaciologiska metoder i klimatforskningens Steen, E. 1958. Betesinflytelser i svensk vegetation.­ tj anst.-Svensk Naturvetenskap 1973 .-Stock­ Statens Jordbruksforsok Medd. 89. holm. - 1966 . Renbetet.-In: Ekonomisk renskotsel. Boras. Selander, S. 1950. Floristic phytogeography of Sterner, E. 1911. Nagra undersokningar ofver tillvax­ South-Western Lule Lappmark (Swedish Lapp­ ten hos de skogbildande traden a tvenne platser i land) I.-APhS 27. Tome Lappmark.-BN 1911. Selinge, K.-G. 1974. Fangstgropar.-Fornvardaren 12. Strand, L. 196,2 . Temperaturendringer i de siste decen­ - 1976. Manniskan i landskapet.-Ibid. 14. niene.-Medd. Norske skogsfors�ksv. 18. Selsjord, I. 1966. Vegetasjons- og beitegranskinger i Stromberg, A. 1955. Zum Gebirgsbau der Skanden im fjellet.-Forskning og Fors�k i Landbruket 17. mittleren Harjedalen.-Bull. Geol. Inst. Univ. Sernander, R. 1898. Studier ofver vegetationen i mel­ Uppsala 35. lersta Skandinaviens fjelltrakter. I. Om tundrafor­ - 1961. On the tectonics of the caledonides in the mationer i svenska fjalltrakter.-Ofvers. Sv. Ve­ south-western part of the County of Jamtland.­ tenskapsakad. Forh . 1898 (6). Ibid. 39. - 1905. Flytjord i svenska fjalltrakter.-GFF 27. Sylven, N. 1906. Om de svenska dikotyledonernas fOr­ - 1910. Pinguicula alpina och P. villosa i Harjeda- sta fo rstarkningsstadium.-Sv. Vetenskapsakad. len.-SBT 4. Handl. 40. Sjors, H. 1963 . Amphi-atlantic zonation, nemoral to Tallantire, P.A. 1972. The regional spread of spruce arctic.-In: North Atlantic Biota and their history. (Picea abies (L.) Karst.) within Fennoscandia: a Ed. by A. Love & D. Love. Oxford. reassessment.-Norw. J. Bot. 19. Skar, 0. 1964 . Vettismorki . Monografi over et skog­ 1977 . A further contribution to the problem of the omrade.-Meld. Norg. Landbr. H�gskole 43 . spread of spruce (Picea abies (L.) Karst.) in Fenno­ Skj�lsvold, A. 1969. En fangstmanns grav i Trysil-fjel­ scandia.-J. Biogeogr. 4. lene.-Viking 33. Tanner, V. 1914. Studier ofver kvartarsystemet i Fen­ Skuncke, F. 1963 . Renbetet, marklavarna och skogs­ noskandias nordliga delar.-Bull. Comm. Geol. bruket.-N orrl. skogsvardsforb . tidskr. 1963 . Finlande 38. Smith, H. 1911. Postglaciala regionforskjutningar i nor­ Tengwall, T.A . 1920. Die Vegetation des Sarekge­ ra Haijedalens och sodra Jamtlands fjalltrakter.­ bietes. 1.-Naturwiss. Untersuch. d. Sarekgeb. in OFF 33. Schwed.-Lappland, 3:4. Stockholm. - 1920. Vegetationen och dess utvecklingshistoria i Tenow, 0. 1972. The outbreaks of Oporinia autumnata det centralsvenska hogfjallsomradet.-Norrl. Hand­ Bkh. and Operophthera spp. (Lep., Geometridae) bib!. 8. Uppsala. in the Scandinavian mountain chain and northern - 1951. Harjedalsfjallens flora forr och nu.-In: Na­ Finland 1862- 1968.-Zool. Bidr. fr. Uppsala, tur i Halsingland och Harjedalen. Ed. by T. Arn­ Suppl. 2. borg & K. Curry-Lindahl. Goteborg. The recent climatic fluctuation in Finland and its con­ - 1957. En botanisk undersokning av Neans dal­ sequenses, 1952.-Fennia 75. gang.-Sv. Vetenskapsakad. Avhandl. i Natur­ Tikhomirov , B.A. 1961. The changes in biogeographi­ skyddsarenden 16. cal boundaries in the north of U.S.S.R. as related

Acta phytogeogr. suec. 65 118 LeifKullm an

with climatic fluctuations and activity of man.­ - 1951. Stig skogsgrensa?-Tidsskr. Skogbr. 59. Bot. Tidsskr. 56. - 1968 . Utbreidsla og hji)gdegrensor til skog-, tre- og - 1962 . The treelessness of the tundra.-Polar Re­ buskeslag i Sogndal og Hafslo.-Oslo. cord 11. Webster, G.L. 1961. The altitudinal limits of vascular - 1970. Forest limits as the most important bioge­ plants.-Ecology 42. ographical boundary in the North.-In: Ecology Werenskiold, W. 1925. Foksneen og granbuskene.­ and Conservation. Ecology of the subarctic re­ Tidsskr. Skogbr. 33 . gions, UNESCO-symp. Helsinki 1966. Paris. Vestergren, T. 1902. Om den olikformiga snobetack­ Tranquillini, W. 1957. Standortsklima, Wasserbilanz ningens inflytande pa vegetationen i Sa�jekfjal­ und C02-Gaswechsel junger Zirben (Pious cembra len.-BN 1902. L.) an der alpinen Waldgrenze.-Planta 49. Wielgolaski, F. E. 1975. Grazing by sheep.-In: Fen­ Turner, H. 1968. Uber "Schneeschliff ' in den Al­ noscandian tundra ecosystems, Part 2: Animals and pen.-Wetter und Leben 20. system analysis. Ed. by F.E. Wielgolaski. Berlin­ Unaeus, J.O. 1953. Harjedalens beskrivning. Transl. Heidelberg-New York. by E. Modin.-Nytryck av aldre skrifter om Jamt­ Wielgolaski, F.E. & Karenlampi, L. 1975. Plant pheno­ lands lan. II. Ed. by P. Nilsson-Tanner.-Tands­ logy of Fennoscandian tundra areas .-In: Fenno­ byn. scandian tundra ecosystems, Part 1: Plants and Vaarama, A. & Valanne, T. 1973 . On the taxonomy, microorganisms. Ed. by F.E. Wielgolaski. Berlin­ biology and origin of Betula tortuosa Ledeb.-Rep. Heidelberg-New York. Kevo Subarctic Res. Stat. 10. Wiklund, K.B. 1928. Huru lange har det funnits lappar Wahlenberg, G. 1813. De vegetatione et climate in i Jamtland och Harjedalen?-Fornvardaren 3. Helvetia septentrionali.-Ziirich. Wramner, P. 1967. Studier av palsmyrar i Laivadalen, Wallen, C.C. 1968. Climate.-In: A Geography of Lappland. Teknik och natur. Studier tilHignade Norden. Ed. by A. S�mme. Stockholm. Gunnar Beskow .-Goteborg. Vaartaja, 0. 1954. Factors causing mortality of tree Zackrisson, 0. 1977. Influence of fo rest fires on the seeds and succulent seedlings.-Acta Forest. North Swedish boreal forest.-Oikos 29. Fenn. 62. - 1978. Skogsvegetationen vid stranden av Storvin­ Wardle, P. 1972. New Zealand timberlines.-Tussock deln under 200 ar.-SBT 72 . Grasslands and Mountain Lands Inst. Review 23. - 1974. Alpine timberlines.-In: Arctic and alpine environments. Ed. by J.D. Ives & R.G. Barry. Maps London. Warenberg, K. 1977. Vegetation och renbete inom Generalstabens karta over Sverige, 1: 100 000: 65 Du­ Ottfjallets renfarm.--Ostersund. ved; 71 Lj usnedal; 76 Tannas ; 77 Hede; 81 Idre. Watt, A.S. & Jones, E.W. 1948 . The ecology of the Nya Grovelsjokartan, 1: 25 000. Caimgorms. Part 1. The environmental and the alti­ Topografisk karta over Sverige, 1: 50 000: 16 C Idre tudinal zonation of the vegetation.-J. Ecol. 36. NW, SE (provisional editions); 17 C Funasdalen Ve, S. 1930. Skogtraemes fo rekomst og hji)idegrenseri NW, NE; 17 D Hede SE; 18 C Sylama NW, NE, Ardal.-Medd. Vestland. forstl. Forsji)ksstat. 13. SW, SE; 18 D Storsjo NW, SW; 19 C Storlien NW, 1940. Skog og treslag i indre Sogn fdi Laerdal til SW, SE; 19 D Are SW. Fillefjell.-Ibid. 23. Turistkarta over Idre fjall med omgivningar, 1: 50 000.

Acta phytogeogr. suec. 65 Appendices

Appendix I. The estimated strengths of the different ecologi- 2 3 4 5 6 cal factors at each of the localities at which these were asses- 47 N 2 1 2 1 sed (for details of scale gradings see the respective figure 48 N 2 2 2 1 legend). The factors are as follows: 1 Maritimity-continenta- 49 N 2 3 2 5 lity; 2 Aspect; 3 Depth and duration of snow cover; 4 Angle of 50 N 2 2 2 1 slope; 5 Slope morphology; 6 Local land usage 51 s 1 5 1 5 52 s 1 3 1 5 Ecological factors 53 N 2 2 2 3 54 N 2 2 1 1 2 3 4 5 6 55 N 3 4 2 5 Loc:l s 3 3 2 5 56 NE 2 4 2 5 2 s 2 2 2 1 57 1 E 3 3 5 5 3 NW 3 l 2 1 58 1 SE 3 1 4 5 4 N 3 3 2 1&4 59 1 E 3 4 2 3 5 N 3 3 5 1 60 1 SW 2 4 2 1 6 E 3 2 2 1&4 61 1 NE 4 5 6 7 7 s 3 2 2 2 62 1 NE 3 3 5 1 8 SW 3 2 2 2 63 2 SE 4 3 4 5 9 w 2 2 2 2 64 SW 3 3 2 1 10 N 3 3 1 1 65 s 2 2 2 1 11 w 3 4 3 5 66 1 SW 2 2 2 1 12 N 1 1 2 1&3 67 2 s 2 2 6 13 E 3 1 2 1 68 2 NE 2 3 2 14 s 1 2 3 69 2 w 1 4 2 1 15 w 1 3 70 2 SE 2 2 2 1 16 NW 2 3 2 1 71 2 s 3 3 4 5 17 w 2 3 5 1&3 72 2 s 2 2 2 5 18 N 3 2 2 1 73 2 s 2 3 2 5 19 N 2 1 1 3 74 2 s 2 3 2 5 20 NE 2 2 1 1 75 2 s 3 4 6 5 21 NW 3 3 4 1 76 2 N 2 2 3 5 22 N 3 4 4 1 77 2 SE 2 3 2 5 23 N 4 4 5 2 78 2 NW 3 4 6 3 24 1 N 1 4 6 5 79 2 N 4 4 5 3 25 1 NE 4 3 5 1 80 2 E 3 1 2 5 26 2 E 3 3 2 2 81 2 NW 2 2 2 5 27 2 SE 3 2 2 2 82 2 NE 3 3 3 5 28 2 E 3 3 2 1 83 2 E 3 3 2 5 29 2 SE 3 2 2 1 84 2 s 2 4 1 4 30 2 E 3 4 2 1 85 2 N 1 4 2 3 31 2 SE 3 3 2 5 86 2 s 2 2 4 5 32 2 s 3 3 2 5 87 2 SE 2 5 6 5 33 2 SW 2 2 2 3 88 2 N 2 3 1 5 34 2 N 2 4 2 5 89 2 s 2 4 2 5 35 2 SE 2 3 2 5 90 2 w 2 4 6 3 36 2 N 2 1 2 5 91 2 E 3 4 6 5 37 2 E 3 3 2 5 92 2 s 2 3 2 5 38 2 SW 2 2 2 5 93 2 w 2 5 6 3 39 2 E 2 1 2 5 94 2 NW 3. 4 6 3 40 2 w 2 2 2 3 95 2 N 1 3 1 3 41 2 w 2 5 6 5 96 2 SW 2 2 2 3 42 2 NW 2 3 2 5 97 2 SE 2 2 2 5 43 2 w 3 3 2 3 98 2 E 2 1 2 5 44 NW 3 2 3 1 100 2 SW 2 2 3 4 45 NW 1 3 1 1 101 2 SW 2 2 6 4 46 N 3 4 4 2 102 3 SW 2 2 5 5

Acta phytogeogr. suec. 65 120 LeifKullm an

2 4 5 6 2 3 4 5 6

103 4 s 4 4 4 5 159 4 s 5 6 104 4 SW 1 2 1 3 160 4 SW 1 2 3 1 105 4 w 1 3 1 1 161 4 SE 3 3 2 1 106 3 w 1 2 1 1 162 4 w 3 3 2 2 107 3 w 3 4 4 1 163 3 N 1 4 2 1 108 3 w 2 3 2 3 164 3 s 2 3 2 2 109 2 s 2 2 2 5 165 3 s 1 2 1 2&3 110 3 E 3 4 2 1 166 3 SW 2 4 2 5 111 3 SW 3 4 4 2&4 167 3 SE 2 3 2 3&4 112 3 SW 3 3 4 2 168 3 s 2 5 2 5 113 3 s 1 1 1 2 169 3 NE 2 3 6 1 114 3 s 2 1 2 2&4 170 3 s 2 2 2 2&3 115 3 NE 4 3 4 2 171 3 SW 2 2 2 5 116 3 SE 3 4 4 2 172 3 SW 2 2 2 3 117 3 SE 2 2 2 1&3 173 3 N 2 1 2 1&3 118 3 E 1 2 1 2 174 3 N 3 2 2 2&3 119 3 w 1 2 2 2 175 3 NW 2 2 2 1 120 3 s 3 5 2 4 176 3 E 3 3 5 2&3&4 121 3 s 3 4 2 5 177 3 s 3 4 2 1 122 3 E 2 4 2 4 178 3 SW 4 5 4 1 123 3 E 3 4 6 4 179 3 N 3 3 2 1 124 3 s 4 4 2 2 180 3 s 2 3 2 2 125 4 NE 2 I 3 181 3 E 4 3 5 2 I26 4 NE I 1 I I I82 3 s 3 4 2 3 I27 4 NW 1 2 I 3 183 3 SE 4 2 2 2 I28 4 NE I 2 2 1 184 3 SE 3 4 4 2 I29 4 NE I 1 1 1 185 3 SW 3 3 2 2&4 130 4 NE 1 1 1 186 3 w 1 4 1 2 13I 4 s 1 1 1 2 187 3 s 2 1 2 132 4 s 2 2 2 1&3 I88 3 E 4 2 5 2 133 4 s I 3 1 2&3 189 3 SE 4 4 2 2 134 4 SW 2 I 3 1&3 I90 3 s 4 4 2 2 135 4 s 2 2 2 1&3 191 3 SE 4 5 4 2 136 3 s 2 2 2 2 192 3 SW 3 3 5 2 137 3 s 2 2 2 2&3 193 3 N 1 2 2 2&3 138 3 s 1 4 4 2&3 194 3 SW 1 1 2 1 139 3 NW 1 2 1 1&3 195 3 NE 3 I 3 2 140 3 NE 1 5 1 2 196 3 NE 3 4 4 2&3 141 3 E 3 5 6 2 197 3 NE 2 4 2 2 142 3 s 3 3 4 2 I98 3 SW 2 4 6 I 143 3 NE 2 3 1 2&4 199 3 E 2 2 2 1 144 3 E 4 4 2 2&3 200 3 N 2 2 2 2 I45 3 s 2 2 3 2 20I 3 NE 2 3 I I I46 3 SW I 2 2 I&4 202 4 s 2 3 2 I&3 147 3 SW 2 I 5 1 203 4 s 2 2 3 3 148 3 SE 2 2 5 1 204 4 E 2 3 I 1 149 4 NW I 1 1 3 205 4 s 3 4 5 5 150 4 s I 5 I 1&3 206 4 s 2 3 I 5 151 4 s 3 4 2 5 207 4 s 2 5 2 5 152 4 w I 3 1 5 208 4 s 2 4 1 3&6 I 53 4 SW I 2 3 3 209 4 SW 2 3 2 3 154 4 NE 1 3. I 5 2IO 4 SW 1 5 I I&3 155 4 s 2 5 2 1 211 4 s 2 5 6 5 156 4 s 2 5 2 I 212 4 s 4 4 6 2 157 4 s 1 3 1 2 213 4 w 2 1 158 4 SE 2 4 5 1 214 4 SW 3 3

Acta phytogeogr. suec. 65 Change and stability of birch tree-limit in the Scandes 121

Appendix ll. Local informants

Halvar Andersson, Ljungdalen Gunborg Antholm, Storvallen Karl Backen, Funiisdalen Olle Blind , Lj ungdalen Edor Burman, Funiisdalen Bengt Ell is, Funiisdalen Elias Fj iillgren, Mittadalen Per-Oskar Fj ellner, Vemdalen Jonas Jonasson, Tanndalen Stina Jonasson, Tiinndalen Johan Jonsson, Lj ungdalen Algot Lindqvist, Ottsjo Per Lundberg, Lj ungdalen Albert Langstrom, Skarkdalen Paulus Middagsfjall, Grondalen Martin Martensson, Lj usnedal Sten Olofsson, Storvallen

Appendix Ill. Supplementary references concerning the for­ Forsslund, K.-E. 191 1. Rundt Sonfjallet.-STF:s Arsskr. mer local land-usage within the different parts of the investi­ 1911. gated area. Abbreviations are the same as in 'References' - 1913. Till Storvatteshogna och ldre-lappama. Ibid. 1913. - 1915. Runt Sonfjiillet, Hiitjedalens hj iirta. In: Vildmar- Adrian, G. 1918. Undersaker-Orebro. En vandringstur.­ ker .-Stockholm. STF:s Arsskr. 1918. Frodin, S. 1893 . En sommarvandring till Helagsfjallet.­ Ahnlund, N. 1931. Pilgrimsvagar i Harjedalen .-Ibid. 1931. STF:s Arsskr. 1893 . Almqvist, S. 1870. Berattelse om en resa i Jamtland somma­ Hellbom, P.J. 1868. Bericht von einer botanischen Rei se in ren 1898 .-0fvers. Vetenskapsakad. Forh. 1869, 26. Herjedalen und angrenzenden Theilen Norwegen im Anonymous, 1919. Bland vart lands sydligaste samer i Idre.­ Sommer 1867 .-Flora oder allgemeine bot. Zeitung her­ Samefolkets Egen Tidning 1(4). ausgegeben von der konigl. bayer. bot. Gesellschaft im Anrick, C.J. 1923. Vastra Valactalen. Turistforeningens nya Regensburg. Neue Reihe: XXIV Jahrg. station i Jamtland.-STF:s Arsskr. 1923 . Jansson, E.A. 1958. Lj usnedals bruks kronika.-Klippan. Antholm, H. 1945. Infodingar och turister i gransfjallen.­ Peterson-Berger, W. 1906. Stroftag kring Helagsfjallet.­ Norrkoping. STF:s Arsskr. 1906. Amdt, E. M. 1808. Resa genom Sverige ar 1804.-Carlstad . Ribers, U. 1958. Harjedalens fa bodrike.-Jamten 52. Roden, H. 1897 . Sylarne sasom turistfjall.-STF:s Arsskr. Biermerklahka, 1922. Brev fran Storvallen.-Samefolkets 1897. Egen Tidning 4 (1). - 1898. En skidtur till Sylarne och andra turer bland hogfjal­ Blomberg, A. & Lindstrom, A. 1879. Praktiskt geologiska len kring Storlien .-Foren. f. skidlopn. framjande i Sveri­ undersokningar inom Hetjedalen och Jemtland.-SGU, ge. Arsb. 1897-98. Ser. C, 32. Schmidt, J. W. 1801. Reise durch einige schwedische Provin­ Boberg, T. 1930. Lunndorrpasset och Tranrisdalen.-Sveri­ zen bis zu den siidlichern Wohnplatzen der nomadischen ges Natur 21. Lappen.-Hamburg. Burman, F. 1894. Koncept-dagbocker forda under resor i Storsjo Sockenkronika 1971. Ed. by C.-E. Sahlberg (1972)­ Jiimtland aren 1793-1 802.-Norrliindska Samlingar Ill. Sveg. Ed. by J. Nordlander.-Stockholm. Thedenius, K.F. 1844 . Berattelse om resa till Hatjedalens och - 1902. Jamtlands vagar. Dagboksanteckningar fran 1791.- Jamtlands fjalltrakter.-Wikstrom, J.E., Bot. Arsber. 0stersund. 1839-1842 . - Concept-dagbocker fran resor i Jemtland aren 1793 , 1794, Tegengren, F.R. 1924. Sveriges adlare malmer och berg­ 1798 , 1799 och 1802.-Unpublished manuscript kept at the · verk.-SGu, Ser. Ca. 17. County Library, Ostersund. Thelander, T. 1898. Vandringsminnen fran Jiimtland och Fj allturer i Jamtland, Hatjedalen och Dalama 1953, Ed. by I. Harjedalen sommaren 1897.-STF:s Arsskr. 1898. Rydelius .-Stockholm. Wennberg, S. 1925. Jiimtlands bergverk.-Fornvardaren 1.

Acta phytogeogr. suec. 65

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