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Variability and ecology of Siberian larch species

Anatoly P. Abaimov Jerzy A. Lesinski Owe Martinsson Leonid I. Milyutin

n iSTRlEimON OF THIS DOCUMENT IS UNLIMITED FOREIGN SALES PROHIBITED

Institutionen for skogsskotsel Swedish University of Agricultural Sciences Rapporter 43 Department of Silviculture Umea 1998 Reports, No. 43 Institutional for skogsskotsel Department of Silviculture

Forteckning over utgivna RAPPORTERfranochmed 1983: List of REPORTS from 1983 onwards:

1983 and root/shoots ratio in young stands of Scots 8. Naslund, B-A.: Talls&dders utveckling fram till pine, Norway spruce and lodgepole pine). forsta gallring. ResultatMn tre forsoksytormed och utan enkelstallning. (Development of Scots 16. Eko, P-M.: En produktionsmodell for skog i pine seededplantations to first thinning. Results Sverige, baserad pi bestind frin riksskogstax- from three experimental plots with and without eringens pro vy tor. (A growth simulator for Swe­ release-cutting). dish forests, based on data from the National Forest Survey). 9. Bjorkroth, G.: Inverkan av hyggesavfall pS. kvavet och den organiska substansen i nigra 14- 17. Pehap, A. & Sahlen, K.: A literature review of 18 ir gamla forsokspianteringar med gran. (The seed respiration. influence from slash on nitrogen and organic matter in some 14-18 years old experiments with 1986 Norway spruce). 18. Naslund, B.A.: Simulering av skador och av- ging i ungskog och deras betydelse for be- 10. Martinsson, O., Karlman, M. & Lundh, J-E.: stindsutvecklingen. (Simulation of damage and Avgingar och skador i odlingsforsok av tall och mortality inyoung stands and associated stand contortatall 4-9 ir efter plantering. (Mortality development effects). and damage in semipractical trials of Scots pine and Lodgepole pine 4-9 years after plantations). 19. Albrektson, A., Frivold, H., Holstener-Jorgen- sen, H., & Malkonen, E.: Published and 11. Pehap, A.: A review of literature in the subject Unpublished Biomass Studies in the Nordic of some physiologically active substances in the Countries. An annotated bibliography up to seeds and pollen of forest, fruit and agricultural 1982. species. (En litteraturoversikt om nagrafysiolo- giska aktiva substanser i pollen och fron fran 20. Simak, M.: Chromosome aberrations in stored upptagna arter). seeds of Pinus silvestris and Picea abies and the consequences on plant properties. 12. Simak, M. & Sahlen, K: Bibliography on x- 1987 radiography in seed research and testing. 21. Pehap, A., Henriksson, G. & Sahlen, K.: Respiration of individual, germiating spruce seeds: 1985 Some investigations and measurements with the 13. Bergsten, U.: A study on the influence of seed Warburg Direct Method. predators at direct seeding of Pinus sylvestris L. 22. Mellberg, I. & Naslund, B-A.: Barrotsplantors 14. Hagglund, B. & Peterson, G. (Editors).: tillvSxt och overlevnad fram till rojningstidpunkt. Broadleaves in Boreal Silviculture - an obstacle or - Resultat frSn en forsoksserie med skilda plants- an asset? (The report contains seventeen papers orter. (Growth and survival for bare-root presented at the Kempe-symposium at the Swe­ seedlings until the time of cleaning. - Resultsfrom dish University of Agricultural Sciences, UmeS, experimental series with different types of in June 1984). seedlings). 1988 15. Martinsson, O.: Markberedningens inlytande 23. Simak, M. & Bergsten,B.: Databas overskogs- pi overlevnad, tillvaxt och rot-skottrelation i frolitteratur publicerad i Sverige fram till 1975. foryngringar av tall, gran och contorta. (The (Data base onforest seed literature published in influence of site preparation onsurvival, growth Sweden up to 1975). DISCLAIMER

Portions of this document may be illegible in electronic image products. Images are produced from the best available original document. VARIABILITY AND ECOLOGY OF SIBERIAN LARCH SPECIES

Anatoly P. Abaimov1, Jerzy A. Lesiriski2, Owe Martinsson2 andLeonid I. Milyutin1

‘Sukachev Institute of Forest, Siberian Branch, Russian Academy of Sciences Akademgorodok, 660036 Krasnoyarsk, Russia

^Swedish University of Agricultural Sciences (SLU), Dept, of Silviculture 901 83 Umea, Sweden ISSN 0348-8968 ISRN SLU-SSKTL-R-43-SE

Printed by SLU, Grafiska Enheten, Ume5, Sweden 1998 Abstract

Abaimov, A.P., Lesinski, J.A., Martinsson, O. and Milyutin, L.I. 1997. Variability and ecology of Siberian larch species. Swedish University of Agricultural Sciences (SLU), Department of Silviculture. Report 43, 123 pp. (Eng.)

There are at least four larch taxons distinguished in Siberia that occupy almost 37 percent of the the Russian forests. The natural distribution of the taxons is clinal from the west to the east with L. sibirica Ledeb. in the west followed by L. x czekanowskii Szafer, L. gmelinii Rupr. and L cajanderi Mayr. L sibirica and L. x czekanowskii are phytocenosis builders only at the northern timberline and in the South-Siberian mountains whereas L. gmelinii and L. cajanderi are the main species over the vast territory within and beyond the permafrost zone of East Siberia. Due to large variety of growing conditions, the main features of the larch forests in terms of age structure and growth rates are also enormously variable. Thanks to specific life strategies with respect to seed dispersion patterns and very high adaptability to fires that often affect Siberian forests, these larch species regenerate very well being only seldom temporary replaced by Betulasp. forming secondary forest associations. Larch forests of different categories (protective and commercial) are exploited and regenerated in the same way as it is applied for Scots pine in Siberia.

There is a growing interest in Siberian larch species among researchers and practicioners from abroad, mainly due to their fast growth and excellent wood properties. Some attempts of introducing Siberian larch species as commercial plantations have already been initiated in western countries. However, the knowledge of botanical, ecological and silvicultural features of Siberian larch species is rather poor outside of Russia. Because of its economic importance for Russian forestry the Siberian larch species have been comprehensively studied for many years and many papers as well as a number of mono ­ graphs have been published, most of them in Russian. The large Russian expertise concerning regionalisation of seed sources, seed crop and quality, seed orchards, seedling production in nurseries and silvicultural practices in commercial plantations beyond their range of natural distribution is presented in this report. May it support foreign foresters in their efforts to enlarge use of Siberian larch species.

Key words: Larch, Siberia, Larix sibirica, Larix gmelinii, Larix cajanderii, systematics, variability, hybridization, distribution, growing conditions, stand structure, dynamics, silviculture, provenance, introduction.

Authors’ addresses: Sukachev Institute of Forest, Siberian Branch, Russian Academy of Sciences Akademgorodok, 660036 Krasnoyarsk, Russia

Swedish University of Agricultural Sciences (SLU), Department of Silviculture 901 83 UmeS, Sweden Preface

Larch is the most abundant tree species on the territory of the Russian Federation. Some 263.4 million hectares, i.e. appr. 37 percent of the whole forest area, is occupied by larch. The immense area with more or less abundant pure or mixed larch forests, stretches throughout Russia from the White Sea in the West to the Pacific Ocean in the East, as well as between the tundra zone in the North (Lat. N 12°) and the Siberian steppe zone (Lat. N 48 °) in the South. However, the larch forests occur even outside of Russia, reaching at the southernmost locality in Mongolia some 45:th parallel. This large distribution of the genus of Larix Mill, in Eurasia shows its extremely high ecological adaptivity to different growing conditions.

Larch forests occurring in Siberia are of very high biospheric and ecological importance not only for Russia itself but also far beyond its boundaries. They form large forest massives of the same type in the permafrost zone, establish both the northern and the southern timber-lines and carry out the water- and soil protective functions in monutain regions. Valuable features of Siberian larch species, such as fast growth, high wood quality and high durability, good perspectives for introduction beyond the range of natural distribution, high potential for selection of the natural populations as suitable to obtain fast growing hybrids, attract attention of scientists to the Siberian larch species both in Russia and in other countries.

Botanical, ecological and silvicultural features of Siberian larch species have been comprehensively studied by Russian researchers for a long time, and many papers as well as some generalized monographs have been published. However, these papers were published mainly in Russian and are almost unknown for western researchers. The insufficient knowledge seriously hampers larger introduction of the Siberian larch species abroad. Nevertheless, some projects have already been initiated in other countries (Sweden, Norway, Finland, Germany, Iceland, and other).

The present report is an attempt to reduce the existing gap of knowledge on the Siberian larch species. The authors do not pretend to comprehensively cover all areas which may be of the readers interest Nevertheless, this book contains a review of results presented in available references that deal with Siberian larch species.

The report was completed by the authors during a 3-month long stay as visiting scientist of the first author in Umei. However, the main part of the work has been done by Abaimov and Milyutin before Abaimovs arrival to Sweden.

Umea, in December 1996

Anatoly P. Abaimov Jerzy A. Lesinski Owe Martinsson Leonid I. Milyutin Contents 1. Systematics 8 1.1. Review of taxonomic studies 8 1.2. Present-day systematics 9 1.3. Interspecific natural hybridization 14 2. Variability 18 2.1. Intraspecific differentiation 18 2.2. Interpopulation and intrapopulation variability 20 2.2.1. Morphological features 20 2.2.1.1. Generative organs 20 2.2.1.2. Vegetative organs 29 2.2.2. Karyotypes 31 2.2.3. Biochemical features 32 3. Range of natural distribution 34 3.1. Lara sibirica Ledeb. 34 3.2. Larix gmelinii Rupr. 39 3.3. Larix cajanderi Mayr 41 3.4. Hybrid complexes 42 4. Growing conditions 44 4.1. Larix sibirica Ledeb. 46 4.2. Larix gmelinii Rupr. 48 4.3. Larix cajanderi Mayr 51 4.4. Hybrid complexes 53 5. Stand structure and dynamics 55 5.1. Age structure and stratification 55 5.2. Diameter structure 60 5.3. Species composition 64 5.4. Growth rates 72 6. Silviculture 76 6.1. Felling systems 76 6.2. Natural regeneration 80 6.3. Artificial regeneration 84 6.3.1. Regionalisation of seed sources 84 6.3.2. Seed crop and seed quality 86 6.3.3. Seed orchards 90 6.3.4. Seedling production in nurseries 92 6.3.5. Commercial plantations and provenance trials 94 in former Soviet Union 6.3.5.1. Within the range of natural distribution 94 6.3.5.2. Beyond the range of natural distribution 95

7. Existing experience and perspectives for introductions in northwest 97 Europe 7.1. Commercial plantations 97 7.2. Provenance trials 99 7.3. Conclusions and practical advice 104 8. Concluding remarks 105 References 106 1. Systematics

1.1. Review of taxonomic studies

As many as eight larch species were quite well known by botanists already at the end of the 19 th century, however at this time they were considered as a separate grup within the genus Pinus L. (Bobrov, 1972, 1978). Some authors, e.g. Ruprecht (1845) assigned larch species to the genus Abies Mill. Regel (1871) was perhaps the very first who considered larch as being a separate genus. Only three larch species were distinguished in Russia by that time, i.e. Larix decidua, Larix sibirica, and Larix dahurica. Works made by the German dendrologist Mayr (1906) - who described three larch species including the East-Siberian Larix cajanderi - had a great importance for knowledge of larch growing at the eastern boundary of the Asian continent.

German botanist Patschke (1913) - who divided Larix Mill, into two sections - Multi- seriales and Pauceriales - has greatly contributed to knowledge of systematics of this genus. Patschke included all Siberian larch species (as well as other species of this genus occurring in Russia) into the section Pauceriales or into the section Larix. Species with spherical or ovate-spherical cones, seed scales distributed in a low number of rows and with protective scales which are two times shorter than the seed scales, were grouped in this section.

More detailed studies on Euroasian species of the section Larix were initiated by the Polish scientist Szafer (1913) who argued for separate status of the Polish larch species Larix polonica. Szafer supposed correctly that Larix polonica is very close to Larix sibirica. According to his opinion within L. sibirica such forms as typica, culta, rossica and altaica should be distinguished. He pointed also correctly that L dahurica is rather far from L. sibirica. But, according to Bobrov ’s (1972, 1978) opinion, Szafer’s assumption that L. dahurica is close to L laricina was wrong. Szafer did not distinguish the north-eastern L cajanderi from L. dahurica.

The most important step in larch systematics was made by Sukachev (1924) who has outlined the main evolutionary stages of the genus. He combined known at this time Siberian and Far Eastern larch species into two genetic series - Eurasiaticae and Pauci- squamatae. Larix sibirica was put by Sukachev into the first series, while L. dahurica and other species of the Far East were assigned to the second one. He considered L. dahurica as relatively young, progressive species originating from the north-eastern horn of Asia at the end of pleistocene and at the beginning of holocene "... not only in terms of a migration process but, very likely, also at the site through the gradual trans­ formation of one species into another" (1924, p. 30). Sukachev does not mention about Larix cajanderi either in the above or in his later papers devoted to the genus Larix.

Larix species’ review made by Pilger (1926) was another important step. Ten larch species recognized by this scientist were grouped to the sections earlier distinguished by Patschke. Six other species described by that time, Pilger considered as forms or synonyms of L gmelinii.

8 Studies carried out by Szafer and Pilger as well as later papers published by the Danish scientists Ostenfeld and Syrach-Larsen (1930) were basic to built up the systematics of the genus Larix, and, in particular, of species in Siberia.

Analysing different East-Siberian and Far Eastern larch species Komarov (1934) returned to the name Larix dahurica Turcz. for Dahurian larch and did not recognize the earlier described L. cajanderi, L. maritima and L. lubarskii as separate species. He accepted the species status only for L. dahurica, L kamtschatica and L olgensis, while other species considered as forms of L. dahurica.

Quite opposite opinion on systematics of larch growing in the Asian part of Russia had Kolesnikov (1946). He accepted all earlier distinguished larch taxons such us L midden- dorfii, L. komarovii and L ochotensis as species. On the other hand, L cajanderi was considered by Kolesnikov as a younger branch of L. dahurica.

Much later, Dylis (1961) - a leading Russian scientist dealing with larch systematics - described Larix sukaczewii, L. sibirica, L dahurica, L kurilensis, L olgensis, and L x maritima as species spread out through the Russian Federation area from the West to the East. L x czekanowskii, L ochotensis , L. x amurensis and L lubarskii were considered by Dylis as hybrid complexes. The first of them occurs in Siberia, while the other ones in the Far East.

Thus, even from this brief review one can see that opinions of different authors on larch taxonomy were extremely discrepant, both in terms of the number and status of the distinguished taxons within the genus Larix.

1.2. Present systematics

Recent knowledge on Siberian larch taxons has been generalized by Abaimov and Milyutin (1995). First of all, it should be noticed that systematics of the genus Larix including Siberian species is extremely tangled. It may be easily explained when considering the main criterion of the differentiation of any species, i.e. its reproductive isolation. In larch this criterion is very weak, thus leading to easy hybridization under natural conditions. Up to present time, there is still no consensus even on the total number of larch species, e.g. according to Sukachev (1924) there are 14 larch species, Komarov (1934) - 25, Dylis (1961) - 20, and Bobrov (1972,1978) - 16 different species.

Different opinions exist also about the number of larch species occuring in Siberia. Dylis (1947, 1961,1981) recognized three species: Larix sukaczewii Dylis, L. sibirica Ledeb., and L. dahurica Turcz. ex Trautv., while Bobrov (1972,1978) agreed about the number of species but not about their names. He recognized instead Larix sibirica Ledeb., L gmelinii (Rupr.) Rupr. and L. cajanderi Mayr. The authors want to point out that all Siberian larch taxons, but Larix sukaczewii will be presented in this review.

There are two reason for this omission. The first is, that only the relatively small, easternmost part of the area of L. sukaczewii covers the westernmost part of Siberia, and

9 second, that this species has been sufficiently described by many scientists during the last years (Putenikhin, 1993; Putenikhin & Martinsson, 1995; Kashin & Kozobrodov, 1994; and others).

Nevertheless, it should be noted that Larix sukaczewii remains up to now a debatable point, though it is described in many Russian dendrological reports and text-books. There are still serious objections against its distinguishing as an separate species. In particular, it can be noted that the essential genetic and karyological differences of L. sukaczewii from L. sibirica are absent (Simak, 1964; Milyutin, Muratova & Larionova, 1993; Semerikov & Matveev, 1995; and others). Bobrov (1978, p. 103) presented an opinion that the above species "cannot differ from each other neither morphologically nor geographically, nor genetically, nor coenotically, nor karyologically ". Such a statement is too long going, for sure. There is a lot of evidences that Larix sukaczewii differs from L sibirica in many morphological and biochemical characters (Mikhailenko & Deryuzhkin, 1970; Latysh et al. 1975; Iroshnikov, 1980; and others). However, in spite of these differences originating from some geographical isolation and distinctions in both species’ ecology, the problem remains debatable whether or not are they sufficient to distinguish L. sukaczewii as the separate species.

The most studied larch species in Siberia is L sibirica Ledeb. The tallest trees of this species are up to 40 m high or more. The young shoots are usually straw-yellow coloured and hairless. The young cones are red most often, of different shades, very seldom green. When maturing they are getting light-brown, of 10 - 50 mm in length and width. There are 9 - 44 seed-scales in a cone. They are distributed in 3 - 7 rows (para- stiches). Seed-scales are ovate or rounded, evidently domed, "spoon-shaped", more or less reddish-downy, with rounded entire upper edge. Scales are 5 - 17 mm long and wide, protective scales are obviously visible. In mature cones, an angle of seed-scales varies from 20° to 50°. The typical form of mature cones is wide-ovoid (Fig. 1). The needles on brachyblasts grow in bundles of 10 - 50. Needle length strongly varies from 5 to 60 mm. Average weight of 1000 filled seeds varies from 4 to 10 g in natural populations. Seed germination energy is 17-70 percent. Germinating ability and share of filled seeds make 24 - 73 percent.

Larix sibirica forms many different forest types. Only in mountains of the southern Siberia, some 172 larch forest types formed by this species have been distinguished (Smagin et al., 1980).

Describing Larix dahurica Dylis (1961,1981) suggested to distinguish two geographical races within its vast area of natural distribution: the western - typical L dahurica ssp. dahurica and the eastern - L dahurica ssp. cajanderi. In his opinion the eastern larch race of Larix dahurica has been formed by the late pleistocene as result of intensive selection as well as of adaptation to climate continentality in initial populations of mother species.

Bobrov (1972, 1978) - who has restored original name of Larix dahurica, i.e. Larix gmelinii (Rupr.) Rupr. - also suggested to consider the eastern race as an separate species that previously was described by Mayr as L. cajanderi Mayr. We also consider

10 Figure 1. Typical mature cones of Larix sibirica Ledeb. Each cone represents one population. Photo: A.P. Abaimov (1996)

L. cajanderi as an separate species distributed over a certain area as well as a number of morphological, biological and ecological features that are different from those of L. gmelinii (Abaimov, 1980; Abaimov, Karpel’ & Koropachinsky, 1980; Abaimov & Koropachinsky, 1984; Abaimov, 1995 a).

Under optimal ecological conditions the tallest trees of L. gmelinii can reach the height of 35 - 40 m. Young shoots are coloured from yellowish-ochre to brown, being hairless or downy. Young cones are mainly red, more seldom green. The colour of mature cones varies from yellow to brown. They are 8 - 35 mm long and 5-25 mm wide. The cones have 7-30 scales distributed in 2 - 5 rows. Seed-scale surface is flat or wavy, they are hairless, with emarginate or weakly emarginate, serrate or straight cut upper edge. Cones are compact. In mature cones, the angle of seed-scales varies from 15° to 45°. Typical form of mature cones is oval and ovate (Fig. 2). The width/length ratio in cones from natural populations makes 0.62 - 0.96. The scales are of 6 - 15 mm long, and 5 - 13 mm wide. TTie needles on brachyblasts grow in bundles of 8 - 58. The needle length varies from 4 to 42 mm. The average weight of 1000 filled seeds varies within a range of 1.5 - 5.0 g in natural populations. Seed germination energy is 11 - 76 percent, germinating ability 18-77 percent, and share of filled seeds 23 - 84 percent.

11 Figure 2. Typical mature cones of Larix gmelinii Rupr. Each cone represents one population. Photo: A.P. Abaimov (1980) 11 L. gmelinii forms a lot of forest types within its vast area. More than 50 different forest types were distinguished for the southern part of Siberia (Panarin, 1965,1977) and more than 40 types for the permafrost zone in the North (Shcherbakov, 1975; Abaimov, 1995 b).

The tallest trees of Larix cajanderi can be up to 35 - 40 m in height. Annual shoots colour varies from yellowish-ochre to brown. Young cones are red or close to this colour, seldom they are green. When maturing, the cones change their colour from yellow to brown. Their length varies from 9 to 25 mm, and width from 10 to 28 mm. The cones consist of 10 - 30 scales growing in 2 - 4 rows. Seed-scales are spathulate, flat or wavy, hairless, shining or mat. Scales are 6 - 17 mm in length and 5-15 mm in width. The upper edge is emarginate, weakly emarginate, serrate or straight cut. Bract-shaped scales are longer than protective ones and are clearly visible. Mature cones are widely open; the angle of seed-scale bending outside is usually as broad as 45° - 90°, sometimes even 100° - 110°. Typical form of cones is round or flattened-round

12 •i] population. Photo: A.P. Abaimov (1980) $ y\ (Fig-3). Width/length ratio of cones varies within species from 1.03 to 2.22. The needles on the short shoots grow in bundles of 12 - 59 and are from 6 to 33 mm long. The average weight of 1000 filled seeds varies in natural stands of L cajanderi from 1.1 up to 6.5 g. Germination energy is 49 - 64 percent; germinating ability 45-81 percent, and share of filled seeds 33 - 69 percent. Seed harvest varies from 20 up to 65.4 kg/ha.

■} Also this larch species forms different forest types. Only in Yakutia more than 40 forest I) types as well as open forests were described (Pozdnyakov, 1975; Shcherbakov, 1975; .] Isaev, 1993). 1.3. Interspecific natural hybridization

The reproductive isolation is weakly expressed between species of the genus Larix. Therefore natural interspecific hybrids are formed very often within the border zones between individual larch species. Obviously, the process of differentiation in larch is not, yet finished.

L. x czekanowskii Szafer (L. sibirica x L. gmelinii) takes a special place among natural hybrids in Larix. The vast area covered by forests of L. x czekanowskii, its ecological specificity and some morphological characters made many researchers pay much attention to this taxon. Hybrids of L. sibirica and L. dahurica were mentioned for the first time by Middendorf (1867). Studying herbarium materials, Szafer (1913) paid attention to larchmaterial collected by Czekanowski and Muller in Siberia. Szafer found that some samples have characters of both L. sibirica and L dahurica which made him consider the hybrid nature of these samples. Thus, in honour of the well-known Polish researcher of Siberia, henamed the selected hybrid forms for Larix czekanowskii Szafer.

The above hybrid complex was described in many papers (by Sukachev & Poplavskaya, 1914; Beissner-Fitchen, 1930; Ostenfeld and Larsen, 1930, and others). The most complete characteristics of L x czekanowskii was given by Sukachev (1934). He noted that the contact zone is the result of the expansion of the two larch species L. sibirica and L. dahurica in opposite directions. In this case L. sibirica expands eastwards while L. dahurica westwards. In the contact zone the result is interbreeding and hybrid forms. The detailed definition of L. x czekanowskii given by Sukachev (1934) remains appropriate till now.

A special attention was paid to L. x czekanowskii by Dylis (1947, 1961), and one of his papers (Dylis, 1959) was almost fully devoted to this taxon. Dylis has roughly analysed morphological variability of L. x czekanowskii, formulated its diagnostic characters, described its geographical area, revealed certain regularities of topoecological location for different hybrids in places where primary species have met, and finally, he gave characteristics of forest types formed by L. x czekanowskii.

The most complete studies of L. x czekanowskii have been presented by Milyutin (Kruklis & Milyutin, 1977; Milyutin, 1983). These studies, based on analysis of paleo- botanical data, show that L. sibirica (or forms allied to this species) first appeared in the north-eastern part of Siberia at the end of the pliocene period. L. dahurica (i.e. L. gmelinii and L. cajanderi) was formed somewhat later i.e. during the pleistocene period when climate become more severe. L. sibirica and L. dahurica which have grown together in the north-east of Siberia, got separated from each other during glacial periods. L. dahurica as being better adapted to the changing environment, remained in this region, while the less adapted L sibirica resisted only to the west and south from the border of glaciation. In the process of expansion westwards, L gmelinii came close to the eastern border of L. sibirica.

The process of outcompeting L sibirica by L. gmelinii still continues. However, never in the past this process was of the same intensity or of the same type along the whole

14 contact zone between two species. Nevertheless, a permanent penetration of L gmelinii into the area previously occupied by L. sibirica results in a light interbreeding of both species. Climate change as well as moving of vegetational zones during the pleistocene period caused the formation of a hybrid zone of L. sibirica and L. gmelinii (Bobrov, 1961). Destruction of ecological niches of the primary species under influence of anthropogenic factors has enlarged spreading of hybrid populations of L. x czekanowskii up to some hundreds kilometers in many regions. At present, this taxon occurs within rather stable area, where it is not outcompeted by any of the initial species.

L. x czekanowskii is characterized most often by the unusual combinations of the characters of primary species, e.g. by downy seed scales of cones which are typical for L sibirica and with emarginate seed-scale edge which characterizes L gmelinii (Fig. 4). In some cases, morphological features of L. x czekanowskii are different from features known for the primary species, e.g. revoluted seed scales. Growth heterosis in L x czekanowskii is a known phenomenon, however a share of heterose specimen does not exceed a few percent in natural populations.

SJ

Figure 4. Mature cones of Larix x czekanowskii Szafer. Each cone represents one population. Photo: L.I. Milyutin (1983)

15 There are evidences on natural hybridization of L. sukaczewii and L sibirica (Dylis, 1947; Igoshina, 1963; Iroshnikov, 1980; and other). It is interesting that also in these hybrid populations, alike in L. x czekanowskii , the cones with revoluted seed-scales can be found, though very seldom (less than 1 percent). However, according to Iroshnikov (1980) the area borders of these two larch taxons have close contact only in the lower flow of the Ob River. In the middle and southern taiga subzones, as well as in the forest/steppe zone of theWestern Siberia, larch populations of both species are not only small but also sparsely distributed. Thus, the interspecific hybridization is almost impossible. Besides, since larch share in species composition of mixed stands is most often low, the gene exchange is also weak within populations.

Appearance of transitional forms in the contact zones between areas of L. cajanderi and L. gmelinii was noted for the first time in 1979 by Abaimov & Koropachinsky. It was found that the angle of seed-scale in mature cones - considered as a main morphological feature differenciating the two species - is distinctly related to certain parts of Eastern Siberia. If the compact, oval or ovate, weakly dehiscent cones (the angle of seed-scale

Figure 5. Mature cones of Larix hybrids from the contact zone between areas of distribution of L cajanderi and L. gmelinii. Each cone represents one population. Photo: A.P. Abaimov (1980)

16 is 15° - 45°) are characteristic for L. gmelinii (Fig. 2), then on the contrary, the widely open, round or flattened-round cones (the angle of seed-scale 45° - 90°) are typical for L. cajanderi (Fig. 3). In transitional populations the above mentioned features take an intermediate position (Fig. 5). Finally, a zone with transitional natural populations - that covers some 7 percent of the area of both mother species - was outlined (Abaimov, KarpeV & Koropachinsky, 1980; Abaimov & Koropachinsky, 1984; Koropachinsky, 1983).

Unfortunately, further investigations in this remote and sometimes almost inaccessible region cannot be carried out at present time due to shortage of measures. Therefore, it was not possible for to get more detailed data on biological and ecological features of those transitional forms. 2. Variability

2.1. Intraspecific differentiation

Intraspecific differentiation of Larix sibirica has been studied very extensively. According to Sukachev (1924, p. 36) "L sibirica is divided into subspecies, such as: the westernmost - L. sibirica ssp. polonica (Racib.), then successively L. sibirica ssp. rossica (Regel) in the north-eastern part of European Russia and L. sibirica ssp. obensis in Western Siberia (basin of the Ob River with exception for Altai). Strictly speaking also other subspecies should be determined, such as L. sibirica ssp. altaica (Szafer) (occurring in the Altai and Sayan Mountains and in the north-western part of Mongolia) as well as L sibirica ssp. jenisseensis, since both the Altai/Mongolian and Yenisei/ Irkutsk larch taxons differ somehow not only from each other but also from the West- Siberian one. However, all these subspecies overlap each other". However, in his paper (1938) Sukachev revised his own taxonomy of L. sibirica giving former subspecies rank of climatic ecotypes:

1) oec. rossica (Sab.) - in the northern and north-eastern regions of the European part of Russia (west of the Urals); 2) oec. obensis Suk. - in the Ob River basin, with exception for the Altai region; 3) oec. altaica (Szafer) - in the Altai region; 4) oec. jenisseensis Suk. - in the Yenisei River basin.

According to Sukachev’s data (1938) oec. rossica is quite similar to L. decidua in cones, while oec. obensis seems to be most typical for L. sibirica. On the other hand, cones of oec. jenisseensis and oec. altaica are a little bit more open, reminding of L. dahurica. Besides some deviations in cone structure, seed-coat in oec. altaica is thicker than that in other ecotypes. Oec. altaica also seem to differ from other ecotypes in its ecological demands, e.g. when grown outside of its range of natural distribution in various regions of the European Russia, oec. altaica showed high frost sensivity.

The oec. altaica possibly demand a higher taxonomical rank. However, because of great heterogeneity of physical and geographical conditions of the Altai region, this problem should be studied more in detail. According to some biochemical characteristics (essential oils composition) this ecotype should be considered as separate species L. altaica (Deryuzhkin et al„ 1971, 1975). In opinion of Iroshnikov (1980) L. altaica is an alpine geographic race with a weak polymorphism and with dominance of green cone form. Larch populations from the Saur Ridge, and Central and Southern Altai Mountains are related to this race.

Within L sibirica ssp. altaica Dylis (1947) has distinguished var. sajanensis. Into this taxon Dylis included also ssp. jenisseensis, that was earlier distinguished by Sukachev (1924). However, according to Milyutin (1983) such approach might be correct only for regions of the upper Yenisei. Iroshnikov (1980) divides var. sajanensis into two geographic races: the upper Yenisei race (populations of the north-eastern Altai, Kuznetsky Alatau, Western Sayan, Tannu-Ola, and the northern Mongolia), and the Sayan race (populations of the Eastern Sayan and Priangarie regions). Such a division

18 is rightful as a whole. It is validated somehow by isoenzyme polymorphism study of Larix sibirica by Larionova and Milyutin (1981) who determined genetical similarity of such L. sibirica subspecies as altaica, sajanensis and jenisseensis. Only the north-west Mongolian larch populations should be considered as the upper Yenisei race, since L. sibirica from the northern Mongolia is close rather to the larch populations from the Zabaikalie region.

Developing studies done by Sukachev, Dylis (1947) distinguished some more varieties close to subspecies or ecotypes of L. sibirica, such as: var. polaris, var. lenensis, and var. baicalensis. However, geographical distribution of var. polaris in the northern Siberia is very uncertain, thus does not let to consider this variety as an intraspecific taxon. Nevertheless, it is doubtful that L sibirica is homogenous in the vast area of the northern regions of Western Siberia between the Urals and the Yenisei River. There are evidences (Skripachenko & Milyutin, 1977, 1982) that the northern populations of L. sibirica differ from the southern ones in nucleotidic DNA composition. These subpolar populations are called by Iroshnikov (1980) L. sibirica var. polaris.

It is relevant to separate var. lenensis and var. baicalensis but their geographic distribution differ from that described by Dylis (1947). According to Milyutin (1980) var. lenesis grows in the regions of the upper Lena and the Irkutsk’ Priangarie. At the north-western coast of the Baikal Lake as well as on the Olkhon Island, var. lenensis is replaced by hybrid forms of Lx czekanowskii. It was olso found that var. baicalensis occurs not only at the south-western but also at the south-eastern Baikal Lake coast

It is hardly probable to identify the above mentioned varieties with the "previous" (Dylis, 1947) or even with the existing hybrids (Bobrov, 1972, 1978). Describing intra­ specific differentiation of L sibirica neither Sukachev (1924) nor Dylis (1947) covered the whole area of this species. Sukachev described intraspecific taxons distributed as far to the East as the Yenisei River, while Dylis reached even the Baikal Lake. L. sibirica from the Zabaikalie region, which forms forests on such mountain ridges as Dzhidinskiy, Khamar Daban, Menzinsky and other was not described at all. Larch from the Zabaikalie region has some specific morphological and ecological features and is worthy to be considered, at least, as variety of var. transbaicalensis. Intraspecific differentiation study of L. sibirica using methods of biochemical genetics (Larionova & Milyutin, 1981) also showed an isolation of L. sibirica growing in Zabaikalie.

Considering intraspecific differentiation of L gmelinii it should be noted that this species was studied much less than L. sibirica. Only one ecotype of L. gmelinii growing under xerophytic conditions in Zabaikalie, should be recognized (Povamitsyn, 1949). Other deviations in this species were usually removed from L. gmelinii and considered as separate species (Mayr, 1906; Sukachev, 1934; Kolesnikov, 1946; Dylis, 1961; Bobrov, 1972, 1978). However, considering L gmelinii in accordance to the present knowledge on this species (Bobrov, 1972), its heterogeneity within the vast area must be obvious. Growing in such different natural conditions as the Middle Siberian Plateau, Western Yakutia, Zabaikalie, etc. it is differentiated, for sure, into smaller intraspecific taxons, which differ in morphological and ecolgical features.

19 Intraspecific differentiation of L. gmelinii is quite well documented, however existing evidence originates only from either provenance trials (Iroshnikov, 1977) or engrafting orchards (Avrov, 1977).

Intraspecific differentiation of L. cajanderi practically has not been studied, yet. In a way, it is described by means of the forest seed regionalisation (1982) (Fig. 6).

According to the principles of this regionalisation, the regions determine given area while the subregions express altitudinal zonality. 5 seed regions and 9 subregions are recognized within the L. cajanderi range of distribution. For L gmelinii this figures are: 6 regions and 12 subregions, for L. x czekanowskii - 6 regions and 10 subregions, for L sibirica - 15 regions and 45 subregions, and for L. sukaczewii - 4 regions and 2 subregions.

2.2. Interpopulational and intrapopulational variability

2.2.1. Morphological features

2.2.1.1. Generative organs

Colour of seed-scales. The colour of seed-scales in female flowers (young cones) is not considered as important diagnostic feature in larch systematics (Dylis, 1961). In fact, either red or green coloured seed-scales occur in all Siberian larch species. Nevertheless, for various species they are named differently: /. rosea Szaf., /. rubriflora Szaf.,/ viridiflora Szaf. forL. sibirica, while/ erythrocarpa hort.,f. chloro- carpa hort. for L. gmelinii and L cajanderi (Ukhanov, 1949). However, in trees from all these species those with red cones of different nuances are prevailing. The only exception in this respect for L. sibirica from Altai. Some 72 - 80 percent of the total number of trees in investigated populations of L. gmelinii and L. cajanderi and 41-91 percent in L. sibirica had the red cones (KarpeV, 1971; Medvedeva, 1971; Pozdnyakov, 1975; Mulyutin, 1983, Abaimov, 1995 a). Some specificity of species is observed in local populations of L sibirica and L. gmelinii occurring in the contact zone: almost 100 percent of trees of L. sibirica had red cones, while the share of L. gmelinii trees with green cones increased to 10 - 34 percent (Milyudn, 1983; Abaimov, 1995 a).

The number of trees with red cones in the population of L. x czekanowskii is more than in that of L. gmelinii and less than in that of L. sibirica, and to the contrary, the number of trees with green cones of L. x czekanowskii is less than in that of L. gmelinii and more than in that of L. sibirica. Thus, L x czekanowskii takes intermediate position, therewith trees with green cones are met more often in populations close to the border of natural distribution of L. gmelinii, and trees with red cones - in populations closer to the L sibirica area (Kruklis & Milyutin, 1977).

20 The relationships between the cone colour and the growth rate in larch was considered in many studies. Existing evidences in matter concerning L sibirica are especially numerous and contradictory. Some researchers found that trees of L. sibirica with green cones grow faster, while others could not find such an evidence. For example, studies carried out in Zabaikalie did not reveal any certain differences in the growth rate when related to the cone colour (Kruklis & Milyutin, 1977). At the same time, there are evidences that qualitative seed characteristics from trees of L gmelinii having green cones growing in the south-western part of Yakutia are higher than those from trees with red cones (Karpel’ & Medvedeva, 1977).

Form of seed-scale upper edge. This feature is of great importance for the larch species diagnostics. In dendrology the scales of round, slightly straight-cut, emarginate and serrated form are usually determined according to theupper edge shape. Trees having cones with round scale form make 80 - 100 percent in Larix sibirica populations (Kruklis & Milyutin, 1977). It is impossible to determine any geographical or ecological regularity of presence of this characteristics in the L sibirica populations. We stated, however, that trees with straight scales are met more often in those stands which are located near the eastern borderline of the L. sibirica distribution.

The edge form of seed-scales in the L. gmelinii and L. cajanderi populations is more various. All types of seed scale upper edge are met in different combinations in the structure of these species, but emarginate ones (37 - 86 percent) and weakly emarginate (6 - 28 percent) are most common. The edge form is characteristic of L gmelinii , but is not characteristic of L. cajanderi. Trees with the straight-cut upper edge of seed-scales make in these species 12 - 17 percent, and with serrated upper edge 13 - 15 percent. Trees with the round upper edge of seed-scales were found only in 7 of 68 populations of L. cajanderi (Abaimov, 1980). As a rule, the above populations occurred at the eastern portion of the species distribution, where in the past L cajanderi had some contact with the larch species of the Far East.

It should be noticed that a higher portion of trees with round seed-scale upper edge is also observed in the local L gmelinii populations near the western border of distribution of this species. 4.3 - 29.0 percent of cones in 13 populations of 137 studied in different localities within the L gmelinii range of distribution had round seed-scale upper edge, which indicate hybridization of this species with L. sibirica. It has to be stressed that these populations occurred in basins of the rivers Kheta on the Taimyr Peninsula and Nizhnyaya Tunguska in Evenkia, thus some 250 - 350 km from the present eastern border of the L. sibirica distribution. This evidences a wide range of hybridization processes during the latest millennia and confirms the idea of the expansion of L gmelinii westwards and stepwise decline of the eastern border of L. sibirica.

In terms of the seed-scale upper edge form, the populations of L. x czekanowskii - in which all its types are met in different combinations - are most differentiated. Trees with round upper edge of seed-scales prevail (57 - 97 percent) in stands similar to L sibirica, while with weakly emarginate, emarginate and straight-cut (50 - 98 percent) are met in populations where features of L. gmelinii dominate. However, any regularity in frequencies of trees with these or those features were not revealed (Milyutin, 1983).

21 Considering the above, there is no doubt about a high polymorphism of Siberian larch species in the form of the upper edge of seed-scales. Nevertheless, a certain specificity of the feature, especially for L sibirica, is followed rather obviously. It is reasonable tosuppose that round upper edge of seed-scales is phylogenetically more ancient then emarginate ones.

Shape of seed-scale surface. This feature is largely applied in systematics of the genus Larix. Seed-scale surface is most often spoon-shaped or flat or transitional between the two. However, wavy (deformed) seed-scales as well as with turned back upper part also occur in larch. This qualitative feature is in practical terms stable both within each tree and each larch species. Polymorphism of the seed-scale surface is closely related to the variability in their consistence and thickness. Wavy and turned back scales are usually soft and thin, while spoon-shaped are more often woody, rigid and thick.

In all populations of L. sibirica being studied by the authors, this species is represented by trees which have cones with spoon-shaped scales, exclusively. There are practically no deviations from this seed-scale shape even in the easternmost part of the species distribution. L. sukaczewii has seed-scale shape similar to this in L sibirica (Dylis, 1947, 1961; Bobrov, 1972; and others).

Populations of L gmelinii and L. cajanderi are more polymorphic in respect to this feature. Within the whole diversity, the trees with flat and transitional seed-scales (72 - 94 percent) prevail in populations of these species. Spoon-shaped scales are met more often at the eastern border of L. cajanderi distribution, i.e. near the Sea of Okhotsk coast where in some stands 24 - 50 percent of trees are related to this type. Likely, such a structure of these populations suggests a hybridization of L cajanderi with some Far- Eastern larch species in the past. The increase of the share of spoon-shaped seed-scales in populations of L gmelinii near its western border of distribution can be also explained in the same way, i.e. as a result of its contact with L. sibirica. According to results of investigations carried out in the Zabaikalie region (Kruklis & Milyutin, 1977) as well as on the Taimyr Peninsula and in Evenkia (Abaimov, 1980) in some stands the seed- scale surface shape in some 4-8 percent trees of L. gmelinii were not specific of this species.

In L. x czekanowskii populations, all shapes of seed-scale surface are present, however trees with cones having spoon-shaped scales (57 - 100 percent) prevail in most cases. Similar trees make the majority even in populations close to the area occupied by L. gmelinii. Likely the spoon-shaped seed-scale is more stable than other ones. At L. sibirica and L gmelinii hybridization, the genes of L. sibirica which control this feature seemingly remains in genotypes of the hybrid complex longer than other genes.

L. x czekanowskii trees often have cones with seed scales turned back (Dylis, 1961; Kruklis & Milyutin, 1977; Milyutin, 1983). Nevertheless, they are met only in some populations and relatively seldom (2-13 percent). Besides, such trees were sporadically met in the populations of L gmelinii and L. cajanderi (Abaimov & Koropachinsky, 1984). Various hypotheses on origin of the turned back seed-scales were suggested.

22 Taking into consideration that similar phenomena are known from hybrids of other species, e.g. L sibirica and L. sukaczewii (Pugach, 1968) Picea obovata and P. abies, it could be supposed that this type of seed-scale shape has been caused by disturbancesin cone evolution due to hybridization processes (Milyutin, 1983). As a whole, spoon ­ shaped, rigid and thick seed-scales are the feature older than flat or transitional ones which are characteristic of L gmelinii and L. cajanderi.

Downiness of seed scales. This feature is very important for larch diagnostics. Among the considered species L. sibirica has downy cone seed-scales, while in L. gmelinii and L. cajanderi the scales are bare. However, L. sibirica is polymorphic in respect to this feature, since the downiness degree in cones from individual trees varies.

The entire diversity of downiness can be combined into several groups (Milyutin, 1983), such as: very dense, when scales are downed by dense red "tomentum"; dense, when scales are covered by easily seen red down; moderate, when only lower half of a scale is covered by red hairs; weak, when red hairs are seen only at a scale base; weak- whitish, when sparse whitish hairs occurs at a scale base, only.

Scales with very dense downiness are met more often in polulations of L sibirica occurring at the south-western and south-eastern coasts of the Baikal Lake. In other regions, such a downiness degree is observed more seldom. The dense downiness of seed-scales is most common in L. sibirica - in investigated populations it occurred in 70 - 100 percent of trees. In this species, the moderate and weak downiness of seed- scales is seldom.

L. gmelinii and L. cajanderi are similar in respect to this feature. Trees with not downed, shiny or matt seed-scales in mature cones are met in most populations of these species. And only nearby the western border of distribution of L. gmelinii , trees with whitish or weak red downiness at scale base are met in a low frequency. Any deviations in this feature in the contact zone of these species were not observed (Abaimov, 1980).

L. x czekanowskii is probably the most polymorphic taxon in degree of downiness. All degrees of downiness are met in populations of this hybrid larch. Besides, in populations closer to L sibirica the trees with dense downiness of scales prevail (50 - 77 percent), while in populations closer in their features to L. gmelinii the trees without any kind of downiness of cone scales (52 - 82 percent) dominate (Milyutin, 1983).

Cone length. Length of mature cones is one of the most important characters when concerning systematics and intraspecific variability in larch. According to Sukachev (1924, p. 16) "larger cones should be considered as a more ancient feature, and small cones should be considered as a character of recent time". Cone length variability within the tree (endogenic variability) is not large, variation coefficient C = 5-18 percent Such figures correspond to the low or moderate level of variability (Mamaev, 1969). Endogenic cone length variability does not differ so much among individual taxons; variation coefficients in L sibirica, L gmelinii and L x czekanowskii are equal in average 9.4,10.4, and 10.7 percent respectively (Milyutin, 1983). Similar

23 figures (Abaimov, 1980) were found also in northern sites for L. gmelinii (7-9 percent) and for L. cajanderi (10.0 - 14.1 percent). Within individual populations, cone length variability is characterized by a low and moderate level of variability. Average variation coefficient for L. sibirica is 11 percent, L gmelinii - 12 percent, L. x czekanowskii - 13 percent (Milyutin, 1983), and for L. cajanderi 9-22 percent (Abaimov, 1980).

As a whole, the cone lengh of L sibirica varies from 11 to 52 mm, of L. gmelinii from 7 to 30 mm, of L. cajanderi from 8 to 28 mm, of L x czekanowskii from 8 to 36 mm. This feature has not any diagnostic value for L. gmelinii and L. cajanderi. L. sibirica greatly differs from them by much larger cones, while the hybrid L x czekanowskii takes intermediate position.

Cone width. Endogenic variability of the feature is characterized by the low, and moderate level (C = 5 - 22 percent). Average variation coefficient for L sibirica is 12 percent, for L gmelinii -12 percent, for L x czekanowskii - 11 percent (Milyutin, 1983), and for L. cajanderi 7.8 - 12.6 percent (Abaimov, 1980).

L. cajanderi is characteristic of higher average values of the feature in comparison with L gmelinii. Cone width in the L gmelinii populations varies according to forest types and geographical localities from 8.8 to 17.8 mm and it is always much less than the cone length. Average values of the feature in L cajanderi vary from 13.2 to 23.3 mm accordingly and exceed the cone length constantly. Student (t) value for differences between data sets on cone width in L. gmelinii and L. cajanderi makes some 22.2 - 39.9 what once again points out distinct differences between these two larch species. The population variability in mature cone width of L gmelinii and L. cajanderi is low or moderate, ranging from 9.4 to 22.1 percent (Abaimov, 1980). The.lowest values for cone width in L. sibirica is 9 mm, and the highest 50 mm. In L. x czekanowskii cone width varies from 6 to 40 mm (Milyutin, 1983).

Average coefficient of cone width variation as calculated for populations from different localities equals: forL. sibirica -11 percent, L. gmelinii -12 percent, L cajanderi - 12.4 percent, hybrid complex from the contact zone of L. cajanderi and L. gmelinii - 11.8 percent, and for L. x czekanowskii -12 percent Thus, the hybrid forms do not express any increase in variability of this feature.

It has to be pointed out that the cone size in larch depends on two factors, such as specificity of populations (that is related to the larch species) and growing conditions (that are related to geographical localisation). For example, moving from the North 1600 - 2000 km to the South, average cone length in Lx czekanowskii increases only by 2.6 - 4.5 mm, while moving from the East to the West at the distance only of 150 - 200 km (i.e. from the distribution borderline of L. gmelinii to that of L. sibirica) it increases by 4-6 mm (Milyutin, 1974).

Number of scales in cones. This feature is related to the length of cone (Dylis, 1961; Kruklis & Milyutin, 1977; Abaimov & Koropachinsky, 1979; Abaimov, 1980; Milyutin, 1980; and others). Endogenic variability of the scale number

24 is characterized by low and moderate variability levels (C = 5 - 23 percent). Average coefficient of variation for L sibirica is 9 percent, L. gmelinii - 14 percent, L cajanderi - 14.9 percent, and for L. x czekanowskii 12 percent

Absolute values of the scale number in L. sibirica cones vary from 12 to 48, in L gmelinii from 6 to 35, in L x czekanowskii from 7 to 44, and in L. cajanderi from 11 to 36. Average statistical scale number in cones of the L gmelinii populations make 11.7 - 20.2 (C = 10.5 - 23.2 percent), of L. cajanderi - 16.0 - 25.3 (C = 9.2 - 24.0 percent), in hybrid complex from the contact zone of the distribution areas of both species - 14.3 - 19.6 (C = 13.2 - 23.4), of L. sibirica - 21.2 - 28.7 (C = 11.1 - 22.3 percent), and of L. x czekanowskii 16.9 - 27.0. Thus, average scale number of L. gmelinii is less than those in other larch species occurring in Siberia.

Angle of seed-scale'). This feature did not attract attention of researchers for a long time. Sukachev (1924) was one of the first who pointed out the large variability in angle of seed-scale in different larch species. Then, Kolesnikov (1946) used this feature when describing L. cajanderi as a separate larch species. It was found later that this angle not only determines the form and structure of mature cones but also the state of cone maturation and release of seed (Dylis, 1961; Egorov, 1961; Pozdnyakov, 1962; Karpel’, 1969; Medvedeva, 1971; Abaimov & Karpel’, 1978; and others). Dylis (1961) considered this feature as very important for diagnostics in larch, since it let him distinguish two geographical races of L dahurica. In turn, Bobrov (1972) used this distinctive feature for species status of L cajanderi.

Earlier, the angle of seed-scale was determined mainly visually. To obtain statistically reliable data characterizing polymorphism of populations in terms of the degree of opening of mature and dry cones, special device has been made (Abaimov, 1980). This device enabled to determine the range of variation of the angle of seed-scales with sufficient accuracy to answer the question "...about degree of genetic inheritance ... of the species’ feature, which is necessary to carry out for the works on selection" (Mamaev, 1969, p. 3). Already, some 30 000 cones from more than 260 Siberian larch populations have been measured for this purpose.

It was found that endogenic variability of the angle of seed-scale in L gmelinii is moderate (C = 14.7 - 21.5 percent), while in L cajanderi this variability is rather low (C = 5.8 - 8.9 percent). Population variability in both species, however, is characterized by moderate or increased levels of variability (C = 11.2 - 26.5 percent). In different sites, the average values of this feature vary in L. gmelinii within the range of 24° and 37° (absolute limits are 15° - 50°). Moving from the North to the South, the average values of this feature increase somewhat within this species area, e.g. in the Olenyok River basin (68° N) these values vary from 24° to 30°, while in the southern part of the Chita region (54° N) from 31° to 38°. The most compact and thus weakly open cones are typical for the larch populations from the Taimyr Peninsula, Evenkia and the north-eastern part of Yakutia, i.e. for regions with the most severe climate (Fig. 2).

*) The angle between seed-scale and the main axis in a mature larch cone.

25 In L. cajanderi, the angle of seed-scale ranges from 54° to 90°, sometimes even up to 100° - 110°. Average values of the feature vary from 73° to 84° in different localities of the species distribution, and increase eastwards as the climate continentality strengthens (Fig. 3). So, the trees of which cone scales are open at obtuse angle are met more often in the basins of the Indigirka and Kolyma Rivers in the northern part of the species distribution than elsewhere (Abaimov, 1980). Thus, the Dylis’ (1961) assumption about high compactness of cones as an adaptive character for larch species that occur in a harsh climate conditions is wrong. In fact, only cones of L gmelinii are compact or weakly open, while cones of L. cajanderi - that occurs in the Far North-East of Asia where climate continentality strengthens still further - are widely open.

In different localities within the contact zone between distribution areas of L. gmelinii and L. cajanderi, the angle of seed-scales changes in both species gradually (Abaimov, et aL, 1980). This observations contradict the opinion presented by Dylis (1961) about a sharp replacement of the eastern race of L. dahurica with western one, in accordance to this feature. The width of the transitional zone between areas covered by L gmelinii and L. cajanderi in the Vilyui River basin is 200-250 km, in the middle flow of the Lena River - 350 km, and near the southern border of the Russian Federation - 500 - 600 km (see Fig. 6). Average statistical indexes of the feature vary within 40° - 66° in transitional populations, and values of variation coefficients (C = 11.6 - 29.0 percent) show the moderate or increased level of the feature variability (Fig. 5).

As a whole, the limits of the average values of the angle of seed-scale vary: in L. gmelinii from 24° to 39° (C = 11.2 - 28.6 percent), in L. cajanderi from 63° to 86° (C = 7.4 -18.5 percent), in the contact zone between the above species in hybrid complexes from 38° to 66° (C = 11,6 - 29.0 percent), in L sibirica from 32° to 44° (C = 12.4 - 21.3 percent), and in L. x czekanowskii from 28.4 to 44.0° (C = 6.7 - 29.0 percent).

The obtained experimental data allow to conclude that the angle of seed-scale expresses a high independence of environment, is inherited and enough reliable at L. gmelinii and L. cajanderi diagnostics (Abaimov & Koropachinsky 1984). This also enables to suppose that compact cones is an ancient phylogenetical phenomenon.

Number of parastichies. Dylis (1947) concluded that number of rows situated spirally along the cone from the left upward to the right (parastichies) is a suitable feature for diagnostic purposes in larch. It was found (Dylis, 1961; Kruklis & Milyutin, 1977; Abaimov & Karpel, 1978; Abaimov, 1980; Milyutin, 1983; Abaimov & Koropachinsky, 1984) that the number of parastichies in cones of L. sibirica varies from 3 to 7 (most often 4); in L. gmelinii from 2 to 5, (most often 3, 64.0 - 91.3 percent); in L cajanderi - predominantly 3(61-88 percent). In L x czekanowskii this feature is more variable than in other larch taxons, varying from 2 to 7 (most often 4 or 3). Thus, in Siberian larch species a certain specifity is observed according to this feature.

Seed-scale size. Study on seed-scale width and length in cones of various larch species (Kruklis & Milyutin, 1977) showed that endogenic variability of these

26 features is low. In most cases, the variability in all studied species ranges between 2 and 3 mm, while the population variability of seed-scale size is a little bit higher (most often 3-5 mm), but still low.

Seed-scale length and width variability in various species is quite close to each other, since the variability greatly coincide. However, the lowest variability (especially in the scale length) is observed in L. gmelinii, while the highest one - in Lx czekanowskii. It was found that the seed-scale size is the feature with very stable heredity (Dylis, 1947).

Cone form. This feature is widely used in dendrological descriptions of larch taxons and usually it is considered as additional for species diagnostics. At comparative study of mature cones, 5 main groups that cover the whole variety of the feature have been distinguished: 1. oval - cone width is much smaller that its length; 2. ovate - cone width is less than its length and the widest part of cone is located nearer to the cone base; 3. wide-ovate - cone length is somewhat more than its width or is equal to it and the widest part is located at the cone base; 4. round - cone length equals to its width, the widest part is in the middle of the cone; 5. flattened-round - cone width is always more than cone length (Dylis, 1961).

The main portion of cones in any tree belongs to one of the above mentioned groups L gmelinii has the ovate cone form (45.0 - 86,3 percent), and L. cajanderi has flattened- round cone form (75 -100 percent). Only insignificant number of cones in both species represents other groups (Fig. 2 and 3). As far as L cajanderi is concerned, its cone form is explained by a large angle of seed-scale that leads to a large cone width - both features being of high distinctive value of this species (Abaimov, 1980; Abaimov & Koropachinsky, 1979, 1984).

Differenciation of ecological and geographical regimes does not result in any larger deviations in terms of the cone form, e.g. various populations of L sibirica, L. gmelinii and L. x czekanowskii occurring in the Zabaikalie region do not differ so much from each other in terms of the cone form (Kruklis & Milyutin, 1977; Milyutin, 1983). Ovate and wide-ovate mature cone forms dominate in this region.

Quantitavely this feature is described as a width/length ratio of the mature, dry cones. In the most of populations of L. sibirica and L. x czekanowskii the cone width is somewhat smaller than their length. The average ratio makes 0.7 - 0.8 (Milyutin, 1983). Within the whole variety, the ratio in the L. gmelinii populations varies from 0.62 to 0.96; in the populations of L. cajanderi from 1.03 to 2.22, and in the contact zone between these species from 0.92 to 1.26 (Abaimov & Koropachinsky, 1979).

Thus, being an inherited character (Dylis, 1947), the cone form is of a certain taxonomic importance. Flattened-ovate cones that dominate in L cajanderi differenciate this species from other Siberian larch species. Ovate and wide-ovate mature cones are characteristic of the others species.

A comparison of the main cone and seed feature in Siberian larch species is shown inn the Table 1.

27 Table 1. Cone and seed features in Siberian larch species (average values). (Dylis, 1961, 1981; Pozdnyakov, 1975; Karpel’& Medvedeva, 1977; Kruklis & Milyutin, 1977; Abaimov, 1980; Milyutin, 1983; Abaimov & Koropachinsky, 1984; Abaimov & Milyutin, 1995)

Larch species Features L. sibirica L. gmelinii L cajanderi Average cone length (mm) 19.0-39.0 12.0-19.6 12.4-19.0 Average cone width (mm) 15.2-32.0 8.8-17.8 13.2-23.3 Cone width/length ratio 0.70-0.90 0.62-0.96 1.03-2.22 Cone form in open state wide-ovate ovate flattened-round Angle of seed-scale (°) 20-50 15-45 45 - 90 Form of seed-scale round slightly deeply upper edge hollow hollow Shape of seed-scale surface spoon-shaped flat or flat or transitional transitional Seed-scale downiness downy not downy not downy Number of parastichies 3 - 7 2-5 2-4 in autumn at the end of in autumn Cone opening for dissemination and at the spring and during beginning of at the 3-5 days, winter beginning only of summer Seed dormancy no yes no Weight of 3.8 - 9.6 1.5 - 5.0 1.1 - 6.5 1000 filled seeds (g) (8.0)

Anther colour. This feature was poorly studied in the genus Larix, while it was broadly investigated in other conifers, e.g. in the genus Pinus. Studies carried out in some populations of L. sibirica, L gmelinii, and L. x czekanowskii in southern Siberia (Kruklis & Milyutin, 1977; Milyutin, 1983) showed predominance of trees with green- yellow anthers. Only a few these trees had yellow-pink anthers. Near the north-eastern border of distribution of L sibirica the trees with green, yellow, and green-yellow anthers made only 0.5 percent, and the absolute majority of trees (99.5 percent) had pink and yellow-pink anthers (Iroshnikov & Fedorova, 1974). Thus, the distribution of trees according to the colour of anther was quite opposite there, when compared with more southern regions. Possibly, when growing in more severe climatic conditions of the North larch trees with pink-red anthers are more frequent, as it is also a case in Pinus sylvestris L.

28 2.2.1.2 Vegetative organs

Annual shoot colour. This feature is of great importance in larch systematics and phytogeny (Sukachev, 1924; Dylis, 1961). However, larch species that occur in Siberia do not express any special differences in the colour of annual shoots. In all species of concern, the young shoots are commonly considered as "light-coloured". However, analysis of the populations of L. sibirica, L gmelinii, L cajanderi, and L. x czekanowskii gives evidence about differentiation in respect to this feature both between different larch taxons and localities (Kruklis & Milyutin, 1977; Abaimov, 1980; Milyutin, 1983; Abaimov & Koropachinsky, 1984).

Trees from the populations of L. sibirica and L x czekanowskii have most often the straw-coloured shoots of different nuances of this colour. Trees from populations of L. gmelinii and L. cajanderi with ochre and yellowish-brown pigmentation of young shoots prevail obviously. Their share was 68 and 56 percent, respectively. Some 13 percent of shoots of L gmelinii and 21 percent of shoots of L. cajanderi were brown- coloured. Dominance of dark pigmented shoots in trees growing near the Sea of Okhotsk coast seem to corroborate assumption made by Bobrov (1972) about contacts between L cajanderi and L kamchatica.

Downiness of annual shoots. The annual shoots may be not downy at all or show sparse, dispersed or heavy downiness. There is no common opinion about the diagnostic importance of this feature. According to Kruklis and Milyutin (1977) the downiness of annual shoots in individual trees is stable. However, this feature is extremaly labile at characterizing of populational and interpopulational variability. The frequency of this feature in populations depends on growth rate and age of trees as well as some other factors (Dylis, 1961). Trees with different degree of downiness can be met practically in any stand in different combinations (Abaimov & Koropachinsky, 1984) what, of course, hampers use of this feature at larch diagnostics.

Needle length. Studies on needle length in Siberian larch species were under ­ taken quite late (Milyutin, 1971; Kruklis & Milyutin, 1977; Milyutin, 1983; Abaimov, 1977, 1980; and others). It was found that endogenic (within individual tree) variability of needle length in L sibirica, L gmelinii, L cajanderi, and L. x czekanowskii is similar (variation coefficients are equal to 16.8 - 26.6 percent, 17.6 - 31.3 percent, 13.1 - 31.5 percent, and 16.9 - 31.8 percent, respectively. Thus, the variability levels in this feature may be considered as moderate to increased in each taxon.

It should be noted that the increased variability of hybrids, such as L x czekanowski is revealed only by those features which respond to environmental conditions (needle length, growth rate, duration of seasonal growth etc.).

The variability of needle length within populations of L. sibirica, L cajanderi and L. gmelinii is characterized by tow, but more often by moderate or increased levels (C are equal to: 6.0 - 20.4 percent, 22.0 - 38.5 percent, and 22.9 - 36.6 percent, respectively). Close values of populational variability are observed also in L. x czekanowskii (C = 5 - 25 (31) percent).

29 Needle size is affected by their location on the shoot. The needles growing on 2-years old shoots are usually shorter than those covering older shoots. Damage caused by insect attacks as well as some other factors may also affect the needle length.

As a whole, the needle length in L sibirica varies from 10 to 58 mm, in L. gmelinii from 5 to 42 mm, in L. cajanderi from 4 to 38 mm, and in L. x czekanowskii from 7 to 49 mm. The occurrence of trees with needles of different length in populations of various larch taxons growing in different geographical locations gives oportunity to distinguish short-needle and long-needle forms in larch.

Needle number in bundles. This feature is characteristic of the genus Larix since other conifers e.g. from the genus Pinus have practically stable number of needles in the bunch. This feature is used larch diagnostics only in the last decades (Milyutin, 1971; Abaimov, 1977).

Endogenic variability of the needle number in the bundles is not stable within a tree, and may vary from the low, through moderate to increased level (variation coefficients in L. sibirica, L. gmelinii and L. x czekanowskii are equal to 5 - 30 percent, 7-22 percent and 6-26 percent, respectively). Needle location in bundles is less affecting the needle number than needle length. However, it should be noted that the higher number of needles in one bundle is observed in older shoots (7-years old or more). Population variability in terms of needle number in the bundle is characterized by low and moderate levels and is quite similar in L. sibirica, L gmelinii, and L. x czekanowskii (variation coefficients are 6 - 19 percent, 6-17 percent and 8-17 percent, respectively). As a whole, needle number in the bundle in L sibirica ranges from 7 to 52, in L. gmelinii from 10 to 54, in L cajanderi from 5 to 59, and in L. x czekanowskii from 9 to 47.

Generalizing the results of comparative studies on polymorphism of Siberian larch species according to main morphological features, it should be noticed that variability levels of quantitative characteristics in populations of these species do not have essential difference. The range of endogenic (individual) and of populational variability does not differ by species specificity and is, mainly, characterized by low and moderate levels.

Hybrid populations from the contact zones of the L. sibirica, L. gmelinii and L. cajanderi distribution are somehow an exception. The features which are strongly affected by ecological factors (needle length, trunk size, etc.) show, as a rule, increased variability there (Abaimov, 1980; Milyutin, 1983; and others). Qualitative features are observed in the hybrid populations not only in unusual combinations, but in some cases they look totally different from primary species (e.g. angle of seed-scale or downiness of seed-scales). Thus, evaluation of generative and vegetative organ variability allows to make following conclusions:

* The entire series of quantitative (seed-scale number, number of parastichies, angle of seed-scale bending outside, cone width/length ratio) as well as qualitative features (shape of seed-scale surface, their downiness, upper edge form, cone form) show high independence degree from growing conditions, are inherited and genetically determined;

30 * L. sibirica differs from L. gmelinii and L. cajanderi by larger cones, shape of seed- scale surface, form of seed-scale upper edge and seed-scale downiness. These features are very specific for each species;

* Angle of seed-scale bending outside, width and form of mature cones and cone width/length ratio in cones are reliable morphological features when diagnosting L. gmelinii and L cajanderi in natural populations. Hybrid complexes in the contact zones of these species take intermediate position according to the above mentioned features. Seed-scale number and needle number in the bundle can be used as additional morphological distinctions.

* Some features which are not typical for this or that species are later revealed in posterity and in "pure" populations remoted from the present-day borders of their distribution. It supports the idea of hybridization in the past and expansion being continued, as e.g. expansion of L. gmelinii westwards. According to variability of some qualitative features (shape of seed-scale surface, form of seed-scale upper edge, pigmentation of annual shoots) observed in L. cajanderi near the western line of its distribution confirm contacts of this species with the Far Eastern larch species, namely with L. kamchatica in the past.

2.2.2. Karyotypes

All karyologically studied larch species have identical chromosome numbers (n = 12 or 2n = 24), and the same is also number of symmetric and assymetric chromosomes. They differ only in number of secondary constrictions and their localization. None of the Siberian larch species reveals polyploid forms (Kruklis, 1974; Kruklis & Milyutin, 1977; and others). L. sibirica and L. sukaczewii have two chromosome pairs in their karyotypes (IE and IV) with secondary constriction, L gmelinii and L. cajanderi have three pairs of chromosome (in, IV and VII) with secondary constriction (Simak, 1964; Kruklis, 1974; Kruklis & Milyutin, 1977; and others), but L. cajanderi has two extra pairs of chromosome with constrictions (Muratova, 1995). B-chromosome is revealed for the first time for Larix sp. in L gmelinii growing in Zabaikalie (Muratova, 1991).

Karyological study of L. x czekanowskii (Kruklis, 1974) showed that this natural hybrid does not not have a specific karyotype: both mature trees and their offspring are characterized by karyotypes of one of the parent species, either L. sibirica or L gmelinii. Similar conclusion was made on karyotype of natural hybrids L. gmelinii and L. cajanderi (Muratova, 1995).

L. sibirica revealed deviations from the normal chromosome morphology which are expressed in availability of ring structures of different type, polycentric chromosomes and fragments. Chromosome anomalies are met in populations at the southern boundary of this species distribution more often than elsewhere. Different chromosome anomalies (acrocentric, ring and dicentric chromosomes) are revealed in L. gmelinii occurring in Evenkia (Muratova, 1995).

31 2.2.4. Biochemical features

Study of chemical compounds variability in larch - mainly those concerning terpenes and isoenzymes - increased in number in the last decades. Results of studies on mono- terpenes present in three Siberian larch species are given in the Table 2.

Table 2. Composition of monoterpenic hydrocarbons in Siberian larch species

C o n t e n t, percent

L. sibirica L. gmelinii L x cze- Compounds kanowskii Volsky Stairs Deryu- Volsky Stairs Deryu- Volsky et al. (1968) zhkin et al. (1968) zhkin et al. (1968) et al. (1968) et at. (1968) (1971) (1971)

santene trace 0.42 trace 0.86 trace a-pinene 9.7 30.0 21.74 17.8 27.3 28.27 19.1 p-phenchene - - - trace - - trace camphene 0.6 1.1 2.02 0.7 0.8 3.33 2.0 p-pinene 5.2 14.1 16.43 6.8 24.4 23.06 11.1 A3-carene 72.7 49.0 37.74 62.8 39.6 19.29 53.0 sabinene - - - trace - - 2.1 a-phellandrene 4.0 - 2.32 2.8 - 1.3 3.0 myrcene - 2.0 3.31 trace 1.8 5.65 trace a-terpinene trace - 3.34 trace - 4.00 1.1 Iimonene 1.0 3.7 4.21 1.3 6.0 6.37 0.9 P-phellandrene 3.4 - 1.05 2.4 - 1.88 0.3 y-terpinene 0.2 - 4.24 3.8 - 3.82 1.2 terpinolene 2.6 - 3.28 1.6 - 2.17 trace

para-tsimole 0.6 trace - - - 6.2

The main components of essential oils in Siberian larch species are some hydrocarbons, such as: A3-carene, a-pinene, and (J-pinene. Large share of A3-carene is, obviously, a distinctive feature for the indivdual larch species since the content of this component sharply decreases in other species (Stairs, 1968) and varies from 0 (in L. decidua and L. kaempferi) to 9.1 - 9.4 (L. laricina and L. occidentalis).

Composition of monoterpenic hydrocarbons in different larch species allowed to suggest the method of chemotaxonomic diagnostics (Deryuzhldn & Latysh, 1975; Latysh et al, 1979). According to their data the essential oil extracted from annual shoots the quantitative ratio of a-pinene to A3-carene in L. sibirica is as 1:2, in L dahurica 1:1, in L. sukaczewii 1:5, and in L. decidua 5:1.

Distinction of larch species within the former USSR area on chemotaxonomic basis, the ratios between a-pinene, (i-pinene, A3-carene in different larch taxons was of great interest (Chudnyi, 1982). Evolutional and taxonomical information increases greatly

32 when - instead of secondary components - proteins and nucleic acids are taken into consideration (Tachtajan, 1974). The use of proteins is of highest priority in studies on biochemical variablity. Biochemical studies of woody plants based on protein research is carried out mainly by applying isoenzyme ferment spectrum analysis.

Investigations on genedcal (isoenzymic) polymorphism of L. sibirica and L. sukaczewii carried out recently by Larionova (Milyutin, Muratova & Larionova, 1993) and by Matveev (Matveev, 1995; Semerikov, Matveev, 1995) did not reveal genetic differences between species studied. Matveev considers them as subspecies: L sibirica Ledeb. ssp. sukaczewii Dyl. and L sibirica Ledeb. ssp. sibirica Bob. Transitional zone between the "European" and "Siberian" subspecies in the Northern Urals is considered to be about 100 km wide.

According to Larionova (Milyutin, Muratova & Larionova, 1993), only 2.1 percent of the total genedcal diversity of L. sibirica and L sukaczewii fall on the share of interspecific differentiation, while the main part of variability (97.9 percent) is found within species (91 percent - within populations, and 6.9 percent between populations).

Study on nucleotic DNA composition of L sibirica and L. gmelinii carried out by Skripachenko (1985) showed that interspecific variability in terms of this character is rather low. At the same time the distinctions between northern and southern ecotypes within species studied were revealed.

Recent investigations on genetic relationships among larch species based on analysis of restriction fragment variation for chloroplast DNA (Tang Qian et al„ 1995) are of great importance. L sibirica and L. gmelinii were studied, but L cajanderi was not taken into consideration. It was found that L. sibirica is related to the North-American species L laricina and L occidentals, while L gmelinii is close to L. potaninii, L kaempferi and L decidua.

33 3. Range of natural distribution

Some 263.4 million hectares or circa 37 percent of the forest area in Russia is occupied by forests that are either pure larch forests or mixed ones, i.e. with trees of the genus Larix in their species composition. Growing stock of all larch taxons is as high as about 22.9 billion m3, what makes 30.4 percent of the total growing stock of Russian forests.

The largest massives of larch forest are met in Siberia and the Far East. In fact, some 97 percent of the total area of larch forests in Russia is covered with Siberian taxons of the genus Larix. The share of individual species (including related hybrid complexes) is as follows: L sibirica - 14 percent, of L. gmelinii - 35 percent, and L. cajanderi - 48 percent (Milyutin, 1983). In total, all larch taxons occupy some 50 percent of the forest area in Siberia. L sibirica occurs on some 3.2 million km2 (Koropachinsky, 1983), while forests of L. gmelinii and L cajanderi cover 1.9 million km2 and 2.6 million km2, respectively (Abaimov et al„ 1980).

Distribution of larch taxons in matter is shown on Fig. 6. There were two main sources of data used to develop the presented map. The first one consists of numerous herbarium samples that through decennia have been collected from different localities by many researchers, and the second includes a high number of own records collected during long-term investigations carried out in Siberia and put into the data bases by Abaimov and Milyutin.

Detailed descriptions of natural range of distribution of each larch taxon in Siberia are presented below. There are also some evidences showing an extent of hybridization processes within contact zones between individual species.

3.1. Larix sibirica Ledeb.

The eastern borderline of the L. sukaczewii range of distribution can be considered as the western borderline of the area in which L. sibirica occurs (Putenikhin & Martinsson, 1995). The available information on hybrid zone between these species (Igoshina, 1963; Dylis, 1947; Iroshnikov, 1980; and others) are not proved satisfactoiy. The results of analysis of hybridization between these - as Matveev (1955) considers - subspecies give evidence that the hybrid forms of L. sukaczewii and L. sibirica are met in the northern ­ most part of the Urals (at creeks Sob ’ and Shchuch’ya), while typical L sibirica occurs in West Siberia (Tazovsky and, maybe, Yamal Peninsulas). However, Matveev’s records have not been confirmed by anybody else.

According to Putenikhin and Martinsson (1995) the western borderline of the L. sibirica range, streching from the towns of Kurgan and Yalutorovsk to the north-east reaches the Ishim River and along its valley it turns to the Irtysh River. Dylis (1947) drew this approximate boundary farther to the east, viz. to the Tara River mouth at Irtysh. However, Putenikhin and Martinsson assume, that this boundary should be drown from the Irtysh River northwards thus including sites mentioned by Dylis, i.e. environs of the town of Tobolsk and the Demyanka River lower flow (Long. E 71°30'). Along the Irtysh

34 the line reaches the Ob River, and close to its left bank goes downstream. The boundary goes from Yalutorovsk along the Tobol River to its mouth at the Irtysh River. Then it continues along the right bank to the Ob River. In the Ob River valley the boundary goes on its left side at some distance from the river bank (approximately 30 - 50 km) practically along the whole stream (especially in its northern part where it keeps to the Malaya Ob River). At last in the Labytnangi region opposite to the town of Salekhard - located north of the Polar Circle - the eastern borderline of L. sukaczewii range of distribution joins the northern one.

The south-eastern border of the L. sibirica range goes through the environs of the village of Orlovka at the Ua Creek and the village of Kyshtovka at the Tara River (Dylis, 1947; Krylov, 1962). The southern border of L sibirica - that begins at the above mentioned points - turns eastwards and goes along the Ob/Irtysh watershed and comes close to the town of Novosibirsk. Then, it crosses the southern part of the Novosibirsk Province and comes to the Altai Republic (Krylov, 1962; Taran, 1969). This species is widely spread out over the Altai Mountains as well as in the Verkhneobsky forest-steppe formations where occurs as admixture in stands dominated by Scots pine. Going through the valleys of the rivers Belaya, Charysh and Alei, the southern border continues in south-eastern direction towards the Kholzunsky Ridge and the Katun Mountains. Then, it turns south­ wards and goes along the slopes of the Southern Altai and Saur Ridges towards the Markakol Lake (Lat. N 86°) in Kazakhstan.

The southern borderline of the L sibirica range crosses the Mongolian border and goes there along a main ridge of the Mongolian Altai. There thisspecies forms small, isolated forests on northern slopes. Such forests occur also on the Khar Azargyn Nuru Ridge (Lat. N 45°50' and Long. E 96°10') and in Baitag-Ula Mountains (Lat. N 45° 10' and Long. E 91°). These sites are the southernmost points where L- sibirica can be met (Dugaijav, 1995).

From the main ridge of the Mongolian Altai the southern border of L. sibirica turns northwards and then goes through the Kharkhira and Turgene Ridges and continues along the northern macro-slope of the Khan-Khukhy Ridge. Then, turning to the east it goes through the western edge of the Khangai Plateau, sharply turns southwards and moves along the Khangai Ridge (Dugaijav, 1995). From the Khangai Ridge, southern borderline of the L. sibirica range proceeds eastwards along the Orkhon River right bank where small patches of larch forests are met. Then, going along the Orkhon/Selenga watershed the southern border of L. sibirica turns to the north and north-east, continues along the southern and south-eastern edge of the reserve Bogdo-Ula and gradually turns to the south-east Farther this border proceeds along the large Kherlen River bend and then along the southern edge of the Khentey Ridge. In general, the eastern edge of the Khantai Ridge coincides with the eastern borderline of the L. sibirica range in Mongolia. This is another example of larch distribution borders being related to the large geo- morphological frontiers (Milyutin, 1983).

So far, the northern borderline of the L. sibirica range of distribution is known insufficiently. According to Dylis (1947) this border goes from the northernmost part of the Urals (the upper flow of the rivers Shchuch’ya and Pederaty) to the south-east,

36 towards the lower flow of the Shchuch’ya River and then it continues through the valley of the Yada River middle flow and almost to the Khobit-Yag River upper flow (Lat N 67°50'). Farther to the east, L. sibirica occurs on several islands located in the Ob River inlet. Then, going somewhat back from the bank of the Ob Bay the northern borderline of L. sibirica goes northwards, continues on the Tazovskiy Peninsula through the upper flow of the rivers Yalovaya and Perlovaya (Lat. N 67°40'). Obviously, L. sibirica comes close to the bank of the Tazovskaya Bay between the rivers Taz and Pur.

The northern border of the L. sibirica range between the rivers Taz and Yenisei is also uncertain. Nevertheless, from the upper and middle flow of the Myaso-Yaga River it continues eastwards. L. sibirica is met in the Bolshaya Kheta River valley. The northernmost "island" stands of this species occur in the Yenisei valley at the Lat. N 69°40' (Dylis, 1947). However, there ate herbarium samples also from isolated small groves located farther north (Lat N 71° 53').

The eastern borderline of L sibirica range of distribution has been studied rather well (Dylis, 1947, 1959; Milyudn & Kutaf ev, 1967; Kruklis & Milyudn, 1977; Abaimov et al., 1980; and others). This line goes southwards a little bit east of the Yenisei River valley between the town of Dudinka and Pyasino Lake and comes to the upper flow of the Pyasina River. More to the south the eastern borderline goes through the Norilsk hollow and the Nizhnyaya Tunguska River (Dylis, 1947, 1961; Vodop ’yanova, 1976). When passing by the Putoran Mountains, the border outlines its western edge thus becoming more sofisdcated. The reason of this behaviour is that L. sibirica comes deep into these mountains only in valleys of such great Yenisei tributaries as Dudinka, Khantaika, Kureika, etc.

Kuvaev (1971) and Vodop ’yanova (1976) assume that in opposite to their behaviour in the southern part of Siberia, in the Putoran Mountains L. sibirica and L. gmelinii occur very close to each other, often replacing each other on altitudinal transects. It is assumed that the hybrids of these species occur there, as well. However, according to our data these statements are false. Abaimov has been carried out long-term investigations within large area of the Putoran Mountains (in the basins of rivers Kotui, Kochechum, Tembenchi, Vivi, Sevemoe). According to his data, there were not found either L. sibirica and L. gmelini or hybrid complexes within the same forest types. On the other hand, within one population of L. gmelinii in individual elevation zones of the Vivi Lake basin (geographical centre of Russia), some signs of hybridization occur. In a few trees it was found that the seed-scales in cones are round and deep downy.

Obviously, it may be stated that in the northern part of Siberia the hybridization zone is rather narrow (up to 200 km) while its borders are more or less distinct. This may be explained by different ecological demands of both species (L. sibirica and L. gmelinii ) and by different degree of hybridization processes. However, more reliable evidence on these phenomena is still needed.

In the mouth of the Nizhnyaya Tunguska River, near the Turukhansk settlement no other larch species but L. sibirica is met First, some 50 km east of Turukhansk the weak signs of hybridization may be seen in L. sibirica. Crossig Nizhnyaya Tunguska River

37 more to the east from Turukhansk (Long. E 89°), the eastern border of L. sibirica turns to the south-east towards the Podkamennaya Tunguska basin. Less is known about the course of this borderline between the rivers Nizhnyaya Tunguska and Podkamennaya Tunguska. There is just known that L. sibirica grows in the Bakhta River basin (some 90 km north from its flow to the Podkamennaya Tunguska River). In the Podkamennaya Tunguska River basin, the boundary of L. sibirica goes farther (about 300 km) to the east of the Yenisei River Valley when passing by the settlement of Baykit somewhat to the west. From Baykit this borderline goes to the south-east along the Podkamennaya Tunguska River to the Vanavara settlement. Above the Chunya River flow to the Pod ­ kamennaya Tunguska no larch hybrids have been found (at least within borders of the Krasnoyarsk Territory).

According to Razumova (1965), in the Katangsky District of the Irkutsk Province in the basin of the Nizhnyaya Tunguska upper flow L. sibirica occurs approximately as far as at the Verkhnyaya Kochema mouth (Lat. N 61°30'). In Yakutiya, the eastern borderline of the L. sibirica range of distribution coincides quite well with watersheds of the Nizhnyaya Tunguska and Vilyui rivers, i.e. with a border drawn earlier by Drobov (1916).

Beginning from the Vitim River mouth (Long. E 113°), L. sibirica eastern boundary turns to the south, towards the area between the rivers Lena and Vitim. The exact boundary is not known here, but it is commonly known that in regions close to the Lena River within Irkutsk Province no other larch species occurs but L. sibirica. Its boundary there may be drawn east of the Lena River not so far from its valley.

The eastern border of L. sibirica approaches the western Baikal Lake shore near the Olkhon Island (Lat.E 52°40' and Long. E 107°30'). Crossing Olkhon this borderline comes to the eastern Baikal shore where it passes through the Bolshoy Chivyrkui River mouth (Tyulina, 1954), then it goes between the Ulan-Ude town and the Khorinsk village and continues towards the Chita Province. Within Chita Province L. sibirica borderline passes by the town of Petrovsk-Zabailcalsky somewhat west of the village Krasny Chikoi, later continues to the south-east to the Ingoda upper flow (Long. E 108°) and then to Mongolia. In Mongolia, the eastern border of L. sibirica goes southwards beginning from the Ingoda River upper flow and rounding the Khentai Ridge from the eastern side then reaching southern borderline of the species at the village Tsenkher-Mandal (Milyutin et ai., 1988).

It should be noted that borderlines between distribution of Siberian larch species are of very great importance for the plant geography. Characterizing the map of Siberia, Komarov (1953, p. 121) wrote: " The enclosed map shows clearly that besides zonal lines which delimit tundra, taiga and steppe with their subdivisions three more lines are distinguished here. The first and the most important of them I consider the line which goes obliquely from the north-west to the south-east and delimits L. sibirica and L. dahurica growing areas". Kuznetsov (1912) suggested to approve the borderline between distribution of L sibirica and L. dahurica as the frontier between the West and East Siberia. Importance of the contact zones between these two larch species with respect to genetics and phytogeography has been pointed out also by Dylis (1959).

38 3.2. Larix gmelinii Rupr.

According to current concepts the western border of L. gmelinii and the eastern border of L. sibirica range of distribution are separated from each other by a large stripe occupied by hybrid larch taxon L. x czekanowskii (Dylis, 1959; Kruklis & Milyutin, 1977; and others). The western borderline of L. gmelinii goes from the Khatanga lower flow (Taimyr Peninsula) through the upper Kheta River basin, crosses the eastern edge of the Lama Lake (Long. E 91°) and continues southwards. Farther to the south it reaches the central part of the Khantaiskoye Lake basin and comes close to Nizhnyaya Tunguska, some 300 - 350 km to the east from the settlement of Turukhansk (located at the Nizhnaya Tunguska River mouth at Yenisei), Long. E 93° (Abaimov, 1980).

Then the western border of L. gmelinii comes to the area between rivers Nizhnyaya Tunguska and Podkamennaya Tunguska coinciding closely with the boundary of perma­ frost. At Lat. N 60° it crosses the Nizhnyaya Tunguska River for the second time - this time at its upper flow - and continues towards the Lena River basin. Here the line goes some 20 - 25 km north of the town of Lensk (south-western part of Yakutia) and, sharply turning to the south-west, passes the Lena right bank near the settlement of Batamai. Then it goes farther towards the Vitim River basin (Abaimov et al., 1980).

In the Vitim River basin, the western borderline of L. gmelinii turns to the south-west and reaches the northern shore of the Baikal Lake south-west of the settlement of Nizhne-Angarsk. Later the borderline comes to the eastern shore of the Baikal where it reaches the Shangnanda River mouth (Tyulina, 1954) and passing by Eravnenskie Mountains from the west side it continues towards the Chita Province.

In the Chita Province, L. gmelinii western borderline passes by the town of Khilka from the east side, then crosses the way Chita-Arei south of the village of Nikolaevskoye and goes to the south to the frontier with Mongolia (Long. E 112°30'). Extreme south­ western limits of L. gmelinii in Russia are quite close to the frontier with Mongolia, i.e. some 30 - 40 km to the east from the village of Kyr (Milyutin, 1983).

I opposition to earlier opinions (Dylis, 1961), L. gmelinii occurs in Mongolia, too. However, it occupies there the very limited area in the north-eastern part of the country (Eren-Daba Ridge). The easternmost sites of L. gmelinii are known from the basins of the Yama-Gol and Duchin-Gol rivers, both being left tributaries of the Uldza River in the basin of the Onon River (approx. 115° E Long, and 50° N Lat.) (Savin et al., 1978). Since the range of distribution of L. gmelinii in Mongolia forms just a narrow stripe, so its southern border goes in the Uldza River basin as well.

In the same basin, approximately some 50 km east of the village Bayan-Ula the western limit of the "pure" stands of L. gmelinii is located. This limit looks as if it prolongs southwards the western border of L gmelinii in Russia and then turning eastwards another 100 - 120 km. As in Russia, the western border of this species as well as the eastern border of L. sibirica are divided in Mongolia by the stripe of L. x czekanowskii hybrid populations stretching from the west to the east for about 250 km (Milyutin et al., 1988).

39 The southern borderline of L. gmelinii continues from Mongolia towards China, however its exact description is unknown for us. There are evidences (Yen-Chu Wang, 1995) that L. gmelinii occurs in China in the Great Khingan Mountains at the altitude 300 - 1200 m a.s.l., from the wetland (swamp) at the bottom to the summit areas containing pure forest stands which cover about 70 percent of the whole mountain area. In the Lesser Khingan Mountains Region, L. gmelinii can grow up to the altitude 4(H) - 600 m a.s.l on gentle slopes and river banks as pure stands or mixed with some deciduous species. L. gmelinii grows well in Heilongjiang, the eastern part of the Jilin Province and in the eastern and western parts of Liaoning Province.

The northern borderline of L. gmelinii is the same as climatic timberline which is conditioned by warmth deficit and short vegetation period. Within the Central and East Siberia this line very closely coincides with the July isotherm +10° C and with isolines of air temperature sum 300° for the period with the temperature more than +10° C during 80 days long vegetation period (Abaimov & Koropachinsky, 1984).

The northernmost forests on the Earth are the open forests formed by L. gmelinii in the northern part of the Krasnoyarsk Territory. One of them, the stow of "Ary-Mas" occurs in the basin of the Novaya River, which is the right tributary of the Khatanga River (72°28' N Lat) (Fig. 7).

Figure 7. Open stand of Larix gmelinii in the Novaya River basin, Taimyr Peninsula, (photo: A.J. Bondarev, 1995)

40 Another one (Dylis, 1981) is located in the lower flow of the Lukunskaya River - the right tributary of the Khatanga River (72°40' N Lat.). Dwarf, shrub-like forms of L. gmelinii are found in the Popigai River valley (Alexandrova, 1937) in the far north-east of the Krasnoyarsk Territory (72°50 z N Lat.). Recently, these sites are isolated from the main L. gmelinii area by the tundra plant associations.

The northern border of L. gmelinii goes farther to the east from the Khatanga and Popigai rivers through the upper flow of the Anabar River to the Olenyok River basin, in the right bank of which begins the eastern border of this species (Long. E 120°) (Fig. 8). More to the south, the eastern borderline of L gmelinii comes to the Vilyui River, somewhat to the west from its right tributary, the Tonguo River (Long. N 121°). Then, going southwards the eastern borderline of L gmelinii crosses the Lena River some 40 - 50 km west of the Olyokminsk settlement and, bending somehow to the south-east, approaches the Olyokma River basin (at Long. E 122°) (Abaimov et al., 1980). According to Dylis (1961), L. gmelinii is largely spread out in the upper flow of the Olyokma River.

In the south of Siberia the eastern borderline of this species goes nearby the Amazar settlement at the border between theChita and Amur provinces (Long. E 122°), and then continues southwards to the central part of the Great Khingan in China.

It is remarkable that the eastern limit of L. gmelinii range of distribution coincides in the large distance with the January isotherm -30° C, and the eastern limit of L. cajanderi coincides with January isotherm -40° C. In the mountains of the Siberian south this regularity is broken because of vertical vegetation zonality and latitudinal zonality overlap each other.

3.3. Larix cajanderi Mayr

Generally, the western border of L cajanderi area goes in the north along the left bank of the Lena River at the distance not more than some 70 - 100 km from its valley. In this area, it coincides closely with the western limit of Pirns pumila (Pall.) Regel and Betula middendorjfii (Trautv.) Mey. This phenomenon is not observed more to the south, neither in the Lena - Vitim watersheds nor in the mountains of Siberian south (Sokolov et.al., 1977; Koropachinsky, 1983). This borderline goes somewhat to the east of the Kysylsyr settlement, then - crossing Lena at 124°30' E Long. - it continues towards the basin of the Aldan River upper flow (Abaimov et al. 1980). Dylis has found that L. cajanderi grows in the southern part of Yakutia along the road Yakutsk - Bolshoi Never. In the Amur Province, L. cajanderi western borderline passes through the areas along the right bank of the Zeya River and then approaches China at the town of Shimanovsk (124°30z).

The southern boundary of L. cajanderi is not so well known. Furthermore, hybridization processes of this species both with L. gmelinii and with the Far East Larix species make drawing of the distinct border even more complex. In general, it can be said that the

41 southern border of L cajanderi goes through the lower flow of the Amga River, and the upper flows of the Aldan and Zeya rivers.

The northern borderline of the L. cajanderi range of distribution goes through the Lena River delta (Polozova, 1961; Shcherbakov, 1975), then it crosses the Verkhoyansk Ridge at 70° N Lat, and continues eastwards through the mouths of the Yana, Indigirka and Kolyma rivers.

Till now the eastern borderline of L. cajanderi range is less known. Reaching in the far north-east the middle flow of the Anadyr River at Long. E 173° it turns to the south­ west, crosses Penzhinskiy Ridge and in the point of Long. E 160° it comes to the Okhotsk Sea shore (Fig. 6). In opinion of Bobrov (1978), in environs of the Pribrezhny Ridge and somewhat to the south of it, L. cajanderi meets L. kamtschatica, and maybe, also some hybrid forms of the Far-Eastern Larix species. It is proved with respect to some morphological features, since those appearing in L. cajanderi from the coastal regions differ from those found in this species from the inland areas. Our investigations (Abaimov, 1980) prove the correctness of the Bobrov ’s supposition. However, additional studies are necessary to assess interrelations between L cajanderi and the Far-Eastern larch species and to draw the hybrid zone borderline properly.

Taking into account all these limitations, the eastern borderline of L. cajanderi range can be drawn from the point located south of the Uda River mouth. Population analysis made in the lower flow of the Zeya River basin and at the Chul’mikan settlement (Udskaya Bay region) showed that according to the main diagnostic features the local larch is more close to L cajanderi than to any Far-Eastern larch species.

3.4. Hybrid complexes

Geographical distribution of hybrid larch complexes in Siberia were studied in different degree. The area of L. sukaczewii x L. sibirica hybrid populations has not practically been studied. It is known only that these populations occur in the north of the Urals and Western Siberia (Fig. 6).

The area of L. x czekanowskii, the hybrid of L. sibirica and L gmelinii, is described in a more detailed way (Dylis, 1959, 1961; Milyutin & Kutafev, 1967; Kruklis & Milyutin, 1977). Approximately, the L x czekanowskii forests growing in Russia occupy some 9 600 thousand ha (or about 11 percent of the area, covered with its parent species), and their growing stock makes some 1143 million cubic meters (Kruklis & Milyutin, 1977).

Making wide stripe streching some 3000 km from the north-west (Taimyr Peninsula) to the south-east (Mongolia) and delimited by the eastern borderline of L. sibirica and the western borderline of L. gmelinii, the area occupied by L. x czekanowskii forms the largest hybrid zone among all known plant taxons. The width of L. x czekanowskii range of distribution is not the same in different regions. In the north the zone width is about

42 80 - 100 km, in the central Yakutia (Republic of Sakha) 250 - 300 km, and in the southern Siberia it is 500 - 550 km wide (Abaimov & Koropachinsky, 1979, Abaimov et al., 1980; Abaimov & Koropachinsky, 1984). Differences in the hybrid zone width may be explained by biological and evolutional features of different larch climatypes as well as by specifity of local ecological (geomorphology, climate, soil) conditions in the contact zone of both parent species (Fig. 6).

The hybrid zone, i.e. range of distribution of L. x czekanowskii , can be practically divided into three subzones. In the first subzone, which can be conditionally called the "eastern" one, L. gmelinii prevails and its allied hybrids are met, mainly. In the second, central subzone, both parent species are phenotypically presented as well as all the possible combinations of parent features that makes the casual crossing limitless. In the third, "western" subzone, L. sibirica prevails and its allied hybrids can be met. The borderlines between these subzones are rather conventional and they are often affected by various ecological and anthropogenic factors (Kruklis & Milyutin, 1977).

Thus, delimitation of geographical distribution of L x czekanowskii enables division between areas that are occupied with the "hybrid forms" and "pure species", i.e. L. sibirica and L. gmelinii, though the introgression of these species causes sometimes appearing of hybrid forms within range of natural distribution of "pure" species .

L. gmelinii and L cajanderi hybridize introgressively also in their contact zone (Fig. 6). As it was already mentioned, Bobrov (1978) assumes that L cajanderi hybridizes, possibly, with L kamtschatica and other Far-Eastern larch species in the coastal zone of the Okhotsk Sea near the Pribrezhny Ridge, and also more to the south of it. However, neither geography of such a hybrid zone nor the hybridization processes in this region have been studied at all.

Finaly, it should be stressed that the boundaries between individual taxons are strongly determined by ecological factors. First of all, geomorphological features of the zones where individual larch species meet each other. They play the role of ecological barriers between these species rather than of mechanical ones (Kruklis & Milyutin, 1977). For example, the north-eastern part of the area occupied by L sibirica is delimited to the east of Yenisei by steep terrace of the Putoran Mtns. The border between L sibirica and L. gmelinii near Baykit village coincides with geomorphological line separating a flat area between the rivers Nizhnyaya Tunguska and Podkamennaya Tunguska from a belt of the Soboliny Ridge. The borderline between ranges of L sibirica and L. gmelinii in the upper flow of Nizhnyaya Tunguska River goes along the southern edge of the Erbo- gachen Plain.

The examples of coinciding of larch area boundaries and different climatic isolines were given already in this chapter. There are also evidences on relatively close coinciding of the borderlines for L. sibirica and L. gmelinii and permafrost limits (Anon., 1962; Anon., 1967).

43 4. Growing conditions

The vast geographical larch area stretching in Russia from the White Sea to the Pacific Ocean as well as from tundra (Lat. 72° N) to the southern border of Siberia (Lat. about 48° N) testifies a large ecological plasticity of larch species and their high adaptability to different natural conditions of boreal Eurasian zone.

The species of Larix genus are characterized by fast growth, energetic assimilation and transpiration, and high productivity. Growing stock of natural larch stands can be as high as 1000 m3/ha (e.g. in the Northern and Central Altai Mountains, Khakassiya or Pri- angarie), and it can be even higher when larch is grown in commercial plantations, such as Lindulovskaya roshcha where growing stock is 1600 m3/ha. When growing on similar sites, the larch stands are often more productive than the pine and spruce stands. Larch superiority in relation to pine and spruce with respect to growing stock ranges from 1 to 2 and from 2 to 3 site quality classes, respectively.

As a rale, fast growth of larch species depends directly on their high photophily. Larch species are more light demanding than any other main tree species in Russian forests. Light demands within Larix genus increase successively from the west to the east in a following order: L. sukaczewii - L. sibirica - L. gmelinii - L. cajanderi but then it decreases in the Far-Eastern larch species. Within one species light demands increase from the south to the north, i.e. exactly as it is in other tree species.

Siberian larch species are well adapted to continental climate. They are less susceptible to frost, temperature inversions, winters with shallow snow cover and they demand less heat than any other main tree species in Russia. They grow both at the altitudinal and northern timberlines, at vegetational period as short as 65 - 80 days, at sum of active temperature decreased down to 500 - 600° C (on plains) and even to 250 - 300° C (in mountains). Montane forests of L. cajanderi - characteristic of the altitudinal timberline in the northernmost latitudes - can be formed at the temperature sum about 200° C. Montane forests of L. sibirica grow in extremaly continental regions of the southern Siberia at elevations of some 2300 - 2400 m a.s.l.

Siberian larch species have rather low demands as far as water supply is concerned. They can grow even at average annual precipitation of 200 - 300 mm, e.g. in the south­ eastern regions of the Altai Mountains, western Tuva, southern Zabaikal’e, and the central part of Yakutiya.

Siberian larch species can grow on soils of all types with exception for very poor and dry ones. L. cajanderi and L. gmelinii, and to some extend L. sibirica, exceed all other tree species in their ability to grow on cold and frozen soils and to use water from both the cold and relatively dry soils.

Close relation of larch forest distribution in Siberia with climate continentality level is observed (Sochava, 1956; and others), i.e. with increasing continentality and permafrost increases also larch capacity to supplant other main tree species. The ecological optimum of Siberian larch species is undoubtedly far from the cold contrasting climate

44 and frozen soils but in the mild climatic conditions they are supplanted by stronger competitors thus pushed out to the less favourable sites, first of all to the north.

Dependence of growing conditions of individual larch species on climate continentality level is well observed when using continentality index (Cc). The continentality index (Conrad, 1947) is a function of differences in July and January mean temperatures and latitude. L sibirica replaces dark-needle forest types when Cc equals to 60 - 65; L gmelinii replaces L sibirica formation when Cc is close to 72; and L cajanderi becomes the absolute dominant forest species under the most continental climate, Cc is equal to 85 - 100 (Nazimova & Polikaipov, 1996).

Table 3. Area covered with larch forests and their growing stock in Siberia (Filimonov et al., 1995)

Forest area Growing stock Administrative in of which in of which unit total larch forests total larch forests thou. thou. per min. min. per ha ha cent m3 m3 cent Yamal-Nenets A.D. 15 709.4 6 625.8 42.18 1 229.70 488.69 39.74 Khanty-Mansi A.D. 26 717.1 858.7 3.21 3 108.27 72.91 2.35 Tyumen' Province 5 043.8 0.3 0.01 669.76 0.04 0.01 excl. Yamal A.D. Omsk Province 2 574.3 2.1 0.08 356.97 0.30 0.08 Altai Territory 2 713.8 70.8 2.61 395.07 12.73 3.22 Novosibirsk Pr. 2 605.0 3.0 0.12 278.16 0.43 0.15 Tomsk Province 16 769.7 9.5 1.43 2 561.97 1.43 0.06 Kemerovo Pr. 4 265.7 6.3 0.15 538.08 0.70 0.13 Rep. of Khakassiya 2 795.9 413.6 14.79 436.20 59.92 13.74 Krasnoyarsk Terr. 50 019.6 6 442.2 12.88 7 555.66 1 055.56 13.97 excl. Taimyr A.D. Republic of Altai 2 359.5 624.9 26.48 472.01 116.37 24.65 Republic of Tuva 7 865.0 3 701.1 47.06 1 090.87 565.24 51.82 Irkutsk Province 56 853.5 17 240.1 30.32 8 754.15 2 576.52 29.43 Ust’-Orda-Buryat 755.1 191.1 25.31 125.73 34.91 27.77 A.D. Rep. of Buryatiya 20 039.2 9 845.0 49.13 1 919.11 987.94 51.48 Chita Province 26 722.6 15 240.3 57.03 2 425.35 1 616.89 66.67 Agin-Buryat A.D. 499.4 247.0 49.46 60.71 39.66 65.33 Taimyr A.D. 3 183.3 1 474.6 46.32 91.10 71.29 78.25 Evenkiya A.D. 47 625.4 34 761.5 72.99 3 657.35 2 588.79 70.78 Republic of Sakha 145 268.3 115 022.9 79.18 9 229.29 7 788.28 84.39 (Yakutiya) Siberia 440 385.6 212 780.8 48.32 44 955.51 18 078.60 40.21

Abbreviations: A.D. - Autonomous District; Pr. - Province; Rep. - Republic

45 Considering larchspecies distribution in different regions it should be noted that in West Siberia L. sibirica stands occupy recently only a little portion of the forest area in the southern and middle taiga sub-zones, while as much as about 40 percent in the northern taiga sub-zone (Yamal-Nenets Autonomous District) (Table 3).

Larch taxons, such as L sibirica, L gmelinii, and L. x czekanowskii become in the central part of Siberia the main species occupying very large portion of the area covered with forests. They are met in all zones and sub-zones from the tundra in the north to the southern taiga sub-zone. However, they dominate only in the northern and middle taiga sub-zones (e.g. 73 percent of the forest area in the Evenkia Autonomous District), while their share in the southern taiga subzone varies from 15 percent in the Republic of Khakassiya to 57 percent in the Province of Chita (Table 3).

Absolutely dominant position have L. gmelinii and L. cajanderi in East Siberia in the northern taiga sub-zone and in pre-tundra forests where their share in forest area varies from 80 to 90 percent (e.g. average value for the Republic of Sakha is 79 percent) (Table 3).

Considering individual Siberian larch species variability one should pay more attention to the ecologically related features than to the morphologic ones since the latter ones are less clearly expressed (Sochava, 1956).

4.1. Larix sibirica Ledeb.

Within L. sibirica range of natural distribution, two regions where L. sibirica is themain species can be distinguished. These regions are situated very far away from each other, the first one in the far north in the pre-tundra and northern-taiga sub-zones and the second one in the far south in the southern taiga and transitional forest-steppe sub-zones. Growing in more severe climatic conditions than L. sukaczewii, L. sibirica expresses much higher frost resistance than the above mentioned larch species, but in its turn, it is greatly exceeded in frost resistance by L. gmelinii. As it was said already (see section 3.1. ), the eastern borderline of L. sibirica coincides with the permafrost limit in the south-western part of its range of natural distribution. In opinion of Bobrov (1978, p. 104), L. sibirica was connected in the past with "areas which were never affected by either overground or underground glaciation". Sharp weakening of reproductive ability of L sibirica in the pre-tundra and generally in the permafrost zone also differentiates this species from L. gmelinii and L. cajanderi.

In opinion of Popov (1982), L. sibirica adaptability to severe climate undoubtedly is related to the frost resistance of its root system. However, in terms of its adaptability to cold soils, well developed root system of L. sibirica is less plastic than not only root systems of Pinus sylvestris and L. gmelinii but also of Pinus sibirica. Hence, L. sibirica badly tolerates soils with shallow located frozen horizons. In such conditions, l. sibirica does not grow better than Pinus sibirica, while otherwise it grows much faster. At

46 excessive moistening L. sibirica forms shallow root system and can give secondary roots.

Very wide ecological niche is characteristic of L. sibirica. It streches from climatic conditions typical for northern and alpine tundras to those of steppe formation. Even within the southernmost part of the range of this species distribution (where L sibirica forms pure stands) the sum of active temperatures varies from 2000° C in the southern Altai foothills to 300° C in continental alpine elevations in the mountains of the southern Siberia.

Nevertheless, L. sibirica is more heat-demanding species than L. gmelinii and especially as L cajanderi. It may be easily observed when comparing temperatures at the start of some phonological phases in these species. In Zabaikal’e, where three larch taxons occur together, flowering of L. sibirica begins at temperature sum 18 - 20 C°, flowering of L gmelinii at 17 - 19° C, and flowering of L. x czekanowskii at 9 - 13° C. Needle bursting in these species begins at temperature sums 50 - 60°C, 30 - 35°C, and 27 - 45° C, and seed ripening at temperature sums 392°, 346°, and 312° C, respectively. (Kruklis & Milyutin, 1977).

The main forest massives of L. sibirica are related to the mountain ranges occurring in the southern part of Siberia and in Mongolia which are known of their high climate continentality index. These regions are characterized by the low air humidity with possible decrease of the average monthly indexes of the relative moisture (at 13.00 hours) down to 35 - 40 percent. Transpiration intensity decrease in L. sibirica takes place only at the decrease of relative air moisture down to 35 percent. At the same time, with increase of air humidity up to 60 - 65 percent the transpiration intensity becomes almost two times lower in montane ecotypes of L. sibirica (Sudachkova et a/.. 1967).

As an exception with respect to air humidity, montane larch forests growing at the middle and alpine elevations in the Central Altai Mountains should be noted. In spite of humid or even excessively humid local climate conditions, L sibirica occupies there a large share of the Pinus sibirica and partly of Abies sibirica ecological niche. Such an unusual phenomenon can be explained by historical reasons and by the long-term anthropogenic effects, such as fires and herding. Besides, the ecological niche of L. sibirica is wider than that of Pinus sibirica and Abies sibirica, therefore such an overlapping is inevitable. However, it should be stressed that in the most of other mountain ranges of the southern Siberia L. sibirica does not fill in the whole its ecological niche since it is supplanted by stronger competitors, first of all by Pinus sibirica.

On burned and clear-cut areas of the Far North L sibirica loses its position as the main species to the advantage of Betula sp. It regains its dominance only after some 50 - 100 years (Tyrtikov, 1974, 1979). In the central and southern regions of Siberia L. sibirica is also often replaced by other coniferous and deciduous species (Sokolov e al„ 1994).

As being a species that sheds needles L. sibirica is well adapted to the low air humidity in winter and early spring (Popov 1982). Moreover, needle bursting of L sibirica takes

47 place rather late. The late needle bursting, however, not always saves its needles of L. sibirica from drying up at the beginning of vegetation period. In some regions of the central Siberia, the drying up and getting brown of the young larch needles at forest edges, on the southern slopes and in open forests is observed. In very dry years, the above described phenomenon described is very common over large massives of larch forests, especially in June.

As it was said earlier, light demands of all larch species are very high. However, it should be added that light demands in larch increase with the age of trees (Sukachev, 1938, and other). Therefore, L. sibirica advance growth is relatively shade resistant which was observed in many regions of Siberia: in the south-western Yakutia (Abolin, 1929), in Tuva (Tikhomirov et al., 1961), in the central part of Siberia (Popov, 1982).

As was noted already, morphological, physiological and ecological features of L. sibirica from different regions of its natural range of distribution were the used as a base to distinguishing of the intraspecific taxons (subspecies, ecotypes, etc.) in this species.

4.2. Larix gmettnii Rupr.

L. gmelinii is the main species of pure dense and open forests in the country between the rivers Yenisei and Lena. Visual appearance of L. gmelinii varies from the tall and straight trees 30 - 35, sometimes 40 m high occurring on the well drained rich sites in large river valleys (Povamitsyn, 1937, 1949; Tyulina, 1954, 1957; Chugunov, 1961; Shcherbakov, 1975; Dylis, 1981) to the dwarf semi-trailing- and trailing shrubs at the northern and altitudinal timberlines (Tyulina, 1937; Polozova, 1961; Vodop ’yanova, 1975; Kuvaev, 1975; Norm et al., 1986). Different life forms of it are met sometimes in the same sites in the Putoran Mountains.

In favourable conditions, such as on sites of site quality class I - II, L. gmelinii forms tree stands of high productivity. In the south-eastern Yakutia and in mountain valleys of the Chita Province, growing stock in its stands is 400 - 500 m3/ha or even more (Tikhomirov et al., 1961; Panarin, 1965; Pan arm et al., 1980). In the permafrost zone, where site quality is most often low (classes V - Vb), L. gmelinii forms typical for the Far North relatively dense and open forests with growing stock from 15 - 49 to 80 - 120 m3/ha (Sochava, 1956; Cheremkhin, 1961; Shcherbakov, 1975; Abaimov et al., 1995). Beyond the Polar Circle - on well warmed sites where frozen horizons in soils are rather deep - some clusters and curtains of larch trees are met. The DBH of trees reaches there up to 40 cm and their up to height to 24 m.

The life longevity of the species in extreme conditions is extremaly high. According to Nedrigailov (1932), some trees of L. gmelinii met in the Olenyok and Anabar River basins were 526 years old. The maximum age of L gmelinii (600 years) was noted by Bondarev (1995) on the Taimyr Peninsula.

In its light demands L. gmelinii exceeds L. sibirica. Nevertheless, it the advance growth

48 Figure 8. Open stands ofLarix gmelinii in the Putoran Mountains, 68° N. (photo A.P. Abaimov, 1996)

Figure 9. Stands of Larix gmelinii in the Tembengi River valley in the central part of Evenkiya, 64°5ff N. (photo: A.P. Abaimov, 1996)

49 develops very well under sparse overstorey ’s canopy. Also on burned and clear-cut areas it regenetares successfully. Besides, L. gmelinii has quite a good ability to regenerate in a vegetative way, mainly through branch rooting.

The range of natural distribution of L. gmelinii is characterized by adverse average annual temperatures (as low as -15° C). Thus, this species is very cold resistant and in this respect exceeds L. sibirica. In its frost resistance it gives up somehow only to L. cajanderi. However, there is no difference between L. gmelinii and L. cajanderi with respect to the climate continentality. L. gmelinii can form forests on the plain areas at the active temperature sum beginning from 550° - 600° C, and in the mountains - beginning from 250° C.

As Pozdnyakov wrote (1975, p. 75 ), "L. dahurica (that includes both L. gmelinii and L. cajanderi) was formed as the plant species parallely with permafrost development". Its root system experiences the same strong and long-term freezing as the above-ground parts of a tree. Moreover, the cold from the shallow located frozen soil horizon affects them during the whole vegetation period. For example, in larch forests of Evenkiya, the temperature of frozen soils in the depth 20 cm varies depending on exposition from 3° to 6° C and seldom reaches 9° - 10° C in the middle of vegetation period (Abaimov et al., 1996). Permafrost determines the very large temperature amplitude between air and soil. In this context, Dylis (1981, p. 58 - 59) supposed that "this large temperature amplitude, from once being the forced condition of survival turned into the necessary condition of normal development and became inherited in L. dahurica".

L. gmelinii endures dry soils worse than L sibirica. However its demands with respect to the soil fertility and heat providing are much lower than those in L. sibirica. It may grow on very different soils, such as dry sandy, cold paludified, stony, acid podzolic, rich alluvial, etc., however rather fertile and well drained soils, with relatively deep frozen horizon are preferable.

Adaptation of L. gmelinii to paludified soils with thick moss is higher than that of L. sibirica. It is owing to ability of this species of developing the secondary root system instead of the primary roots, which are stepwise overgrown with moss and die off in the frozen soil (Timofeev & Dylis, 1953). On river banks being periodically damaged by floods in the Siberian permafrost zone, L. gmelinii often has two or three level root systems formed by secondary roots. Their main root mass is concentrated in the upper, 20 cm deep soil layer. On the other hand, on warmed up and well drained plots the roots of L gmelinii can penetrate to the depth of 0,8 - 1,0 m.

As it was already said (see section 2.2.1.1.), the angle of seed-scale in cones of L. gmelinii is moderate. It determines not only the form and structure of cones but also the time and character of seed dispersion. It begins only in spring or in summer of this year which follows the crop year. Nevertheless, some portion of seeds may remain in cones during 3-4 years (Egorov, 1961; Karpel’, 1971, 1974; Abaimov & Koropachinsky, 1984; and others). This phenomenon of L gmelinii is of a great economic importance. On the one hand, dense, badly dehisced cones make seed extraction difficult when needed for silvicultural purposes. On the other hand, considering a good seed year

50 periodicity L. gmelinii trees have practically always a certain seed stock in natural populations. Since wild fires are considered as the main destabilizing factor in the permafrost zone and due to that they may affect the same forest plots once and once again with the periodicity of 40 - 100 years then it seem to be quite resonable to suppose that the ability of prolonged seed supply by saving them in cones is an inherited response of L. gmelinii to forest fires.

During investigations carried out in the south-western Yakutiya it was found (Karpel’, 1974) that seeds dormancy in L. gmelinii is very high. They become mature in the spring next year after crop year. For example, seeds colected in the natural tree stands when sown in September 1963 showed germination ability as low as 13.3 percent. When sown in May 1964 it was as high as 42.7 percent.

Similar results were obtained when seeds of this species collected in the Central Evenkiya were sown in 1994 (Abaimov, unpublished). In November 1994 - gemination ability was as low as 12-16 percent, next spring (May) it was 49.5 - 76.3 percent. Of course, this confirms long-term dormancy in this species and should be taken into consideration when growing L. gmelinii and when comparing its seed with other larch species.

L. gmelinii expresses very high plasticity with respect to growing conditions. There is evidence that this species is expanding during the last decades at the northern timberline, both towards tundra zone on the plain areas (Tolmachev, 1931; Vinogradova, 1937; Tyulina, 1937; Kryuchkov, 1973) and upwards in the mountains of the Far North (Mironenko, 1970; Kuvaev, 1975; Vodop ’yanova, 1976; Abaimov et al„ 1995).

4.3. Larix cajanderi Mayr

Depending on latitude, altitude, and site conditions, an appearance of L. cajanderi varies from the straight stem trees up to 35 - 40 m tall to the trailing dwarf shrubs 30 - 50 cm high.

As other Siberian larch species, L. cajanderi is characterized by the high life longevity. Trees of the age up to 500 and even older years are met in different places. In the Yana River basin, the mean age of stands was found to be 300 - 320 years (Pozdnyakov, 1983). On the major part of its range of natural distribution, L. cajanderi forms typical for the Far North open forests, with growing stock 10 - 60 m3/ha. On the rich alluvial soils of river valleys it forms high productive dense taiga stands with growing stock of 500 - 700 m3/ha (Starikov, 1958; Tikhomirov et al., 1961; Pozdnyakov, 1986; Shcherbakov, 1975).

L. cajanderi is not heat-demanding species owing to what it occupis ecological niche in the extremely severe conditions of characteristic of the mountain ranges in the north­ eastern extremity of Asia. From all the tree species on the Earth L. cajanderi is the most

51 adapted species to the extremaly continental climate and soil permafrost. Within the main part of its range of distribution the amplitude of annual temperature is as high as 38° - 66° C.

Beyond the Polar Circle L. cajanderi reaches altitudes of 600 - 650 m a.s.l. In the southern part of its distribution area this larch species penetrates to the zones of mixed and deciduous forests as well as dry steppe. Having such a wide ecological niche L. cajanderi forms mainly pure forests on the vast area between Lat from 40° to 71 ° N and Long, from 125° to 170° E.

L. cajanderi ecological area is characterized by extremaly low heat providing. The sums of active temperatures vary from 200° C in the subalpine forests to maximum 1500° C in the southern part of its range of distribution. In the sualpine forests, the vegetation period can be as short as 65 - 68 days, and adverse average annual air temperatures are no higher than -11° to -17° C. The sum of adverse average monthly temperatures - which shows cold resistance of the species - reaches maximum value of -220° C. The temperature of the soil layer being penetrated by the root system does not exceed, as a rule, 3° - 6° C in the middle of summer (Stepanov, 1988; Tarabukina & Savvinov, 1990).

According to observations made in the Central Yakutia (Utkin, 1958,1965; Pozdnyakov, 1975), L. cajanderi forms a shallow root system. The main portion of physiologically active roots are concentrated in the upper 30 - 40 cm soil layer. Their roots penetrate the soil profile to the depth of 70 - 90 cm. In the excessively watered soils as much as 82 percent of all the roots biomass are located in a 10-cm deep soil layer (Pozdnyakov, 1963). Because of water deficit and low temperature of active soil horizon the density of root systems can be of higher importance for stand formation than the density of tree canopy (Pozdnyakov, 1961 a). When the heat-isolating layer of the moss-lichen cover (15 - 20 cm thick) increases and when the permafrost horizon comes to the soil surface, L. cajanderi alike L. gmelinii forms secondary roots. Obviously, this capacity of the both larch species appeared in the evolution process and in result of their adaptability to permafrost. This allows these species to secure their role as the main tree and compete successfully with other tree species.

L. cajanderi does not demand fertile soils. Within the vast area it grows on stony screes, poor cobble soils on mountain slopes, humus carbonate and acid podzolic soils as well as on alluvial soils of river valleys. Only on dry sands of the Central Yakutiya it becomes outcompeted by Pinus sylvestris.

Alike other Larix species, L cajanderi is highly light-demanding tree species. Never­ theless, advance growth survives and developes successfully under overstorey trees for a long time. Sometimes saplings of the advance growth expressing symptoms of heavy depression and stunted growth are able to survive as long as up to the age of 80 - 100 years. Then, under favourable conditions they replace successfully the dying off over- storey trees.

Water supply in stands of L. cajanderi is often low and its indicators are similar to those

52 of dry steppe. In the permafrost zone, the survival and development of forests is extremaly dependent on water supply from the frozen soils smelting during vegetation period (Pozdnyakov, 1975).

One more species peculiarity of L cajanderi should be noticed. As it was said already (see section 2.2.1.1.), theangle of seed-scale in cones of rather low. This causes that the seed dispersion takes place just after 3-5 days after seed ’s ripening (Egorov, 1961; Pozdnyakov, 1968,1975; Medvedeva, 1971; and others). Such a rapid dispersion of ripe seeds is supposed to be a genetically fixed adaptive response of L cajanderi to severe climate of its range of natural distribution. These climate conditions are characterized, as it was said earlier, by a harsh continental climate with the hot summer and the low precipitation in the early vegetation period. Dispersing its seeds before sheding needles, L. cajanderi provides the most favourable opportunity for seed germination and rooting of the seedlings since the limited but still available water resources in the soil can be utilised.

Seeds of L. cajanderii do not dormant thus differing from seeds of L. gmelinii with this respect (Pozdnyakov, 1975). The differences in the seed behaviour between L. cajanderi and earlier described behaviour of the seeds of L. gmelinii may be seen as respective permanented life strategies of each species.

It was found experimentally that seeds of L. cajanderii from the central Yakutiya originating from self-polination do not differ in terms of seed quality from freely polinated seeds of this species (Pozdnyakov, 1975). In average, germinability for self- polinated seeds was 67 percent, while in freely polinated seeds - 69 percent, and in turn, germination energy was 64 and 49 percent, respectively. That is why, even single trees that survived after harvest or fire, are able to produce a high quality seeds, thus securing the species position even in the stress situation.

L. cajanderi is the main species in forests of the north-eastern Siberia. It regenerates well on burned and claer-cut areas. Besides, it competes rather successfully both with conifers and deciduous species in the southern part of its range of distribution. Only seldom it gives up its dominance to Betula sp. on the clear-cut areas. On the other hand, it is not able to win competition with Pinus pumila at the upper timberline in mountains. Besides, L. cajanderi is often supplanted by fast growing Chosenia arbutifolia behind the Verkhoyansky ridge when colonizing plots formerly affects by floods. Nevertheless, the continuous character of the vast area where L cajanderi dominates proves its high ecological plasticity and phytocoenotical stability.

4.4. Hybrid complexes

Ecology of Siberian larch hybrid complexes is considered on example of L. sibirica and L. gmelinii hybrids (L. x czekanowskii ) since other hybrid complexes were not studied in this respect Specific relating of these or those hybrid forms of Lx czekanowskii to different sites is revealed. For example, at the Baikalsky ridge (the north-western Baikal

53 shore), L. gmelinii and its allied hybrids prevail somehow when moving towards south­ west along the Baikal in the upper and middle mountain belt To thecontrary, L. sibirica dominates moving to the north-east in the lower slope belt and at the Baikal lake shore (Sukachev & Poplavskaya, 1914; Koropachinskiy & Milyutin, 1964). A comparison of two larch populations can illustrate the described regularity. One of them (very open larchforest at the upper timberline, 30 km north-west of the village of Baikalsk) consists up to 25 percent of L. gmelinii and its allied hybrids. However, composition of another population (larch forest of the cowberry-Alpenrose type, near the same village) is following: hybrids allied to L. sibirica make 10 percent, hybrids with equal ratio of both parents ’ species characters make 39 percent, hybrids allied to L gmelinii - 48 percent, and L. gmelinii itself - 3 percent. Thus, altitudinal population consists entirely of L. gmelinii and its allied hybrids, and in the forests growing in the Baikal shore these species form only 51 percent of the population.

This regularity can be observed only at larch stand composition studies carried out on the large area, meaning that a sharp difference between composition of two stands located close to each other, e.g. on adjacent slopes of different expositions, cannot be expected.

Even more clear regularities between site conditions and hybrid character are observed in Zabaikal’e (Dylis, 1959; Koropachinsky & Milyutin, 1964). L. sibirica and L. gmelinii contact each other in this region according to sites clearly demarcated in ecological regard: L. gmelinii is met in cold bottoms of small valleys, on bogged terraces or on the northern slopes with frozen ground, while L. sibirica occurs in well drained larger river valleys, along the southern moutain slopes, etc. For example, in environs of the town of Petrovsk-Zabaikalsky (Chita Province), hybrids allied to L. gmelinii are met only in the wet ravines at the eastern border of the L. sibirica range of distribution. L. gmelinii is absent on the southern slope near Osinovka village (Khantai-Chikoi Plateau, Chita Province), while it makes 77 percent in the tree stand on the north-western slope, and as much as 88 percent on the northern one. Obviously, in Zabaikal’e region with its sharp variations of microclimatic conditions, the dependence between larch species as well as their hybrids and site conditions is seen especially clearly. Certain regularities in altitudinal distribution of L sibirica, L gmelinii and their hybrid forms have been revealed in the Putoran Mountains (Kuvaev, 1971).

Generally, it can be said that within L. sibirica and L gmelinii contact zone availability of hybrid forms allied to L sibirica increases in warm and dry sites, while the forms allied to L. gmelinii are met in cold and wet sites. As Iroshnikov (1980) considers, the similar regularity is observed in the contact zone of L sukaczewii and L. sibirica.

It can be added that forests of the Baikal Lake - of which one third consist of stands of L. sibirica, L. gmelinii and L. x czekanowskii - play an important environmental role of the water-protecting zone for this unique lake.

54 5. Stand structure and dynamics

The origin of a tree-stand and processes determining its dynamics reflect an integral effect of biotic and abiotic factors. Hence, a large variation of stand ’s age structure and species composition are observed. Thus, tree-stands may become even-aged or uneven- aged, pure or mixed, i.e. consisting of a number of tree species. Between these extremes - even within one geographical region - a range of transitional variants can be observed. Besides, the DBH, height, volume increment, survival or mortality of trees, etc. change over each forest generation life-span. In turn, this time dependent variability of individual features affects the main parameter of stands, i.e. their growing stock.

Larchforests of Siberia develop under different climatic conditions and are distinguished by a great variety of structure and composition. High productive tree stands are formed under ecological optimum, open forests of low productivity - under unfavourable regime. The low productive forests have no commercial interest, but they play an important ecological, biospheric and social role. The northern open forests ensure livelihood for the sparse aboriginal human populations.

The behaviour of individual larch species in Siberia varies depending of their living conditions. In the permafrost zone, Larix gmelinii and L. cajanderi have no competition from other tree species and form pure tree stands on vast areas. In the contrary, Pinus sylvestris L. is a strong competitor for L sibirica on sandy and warm soils of Siberian taiga. On rich and well water saturated soils, a number of competitors increases including Picea obovata Ledeb., Abies sibirica Ledeb., Pinus sibirica Du Tour as well as deciduous such as Betula sp. and Populus tremula L. Hence, climatic and edaphic conditions impact on stand composition, structure, regeneration ability, etc. Materials presented in this capital will illustrate major regularities and trends in this respects.

5.1. Age structure and stratification

Age structure shows history of origin and dynamics of stands in the certain temporal stages of their development. Many Russian researchers apply such expression when the order of combination and presence of trees of the certain age are determined. With respect to age structure three main classes of tree-stands has been distinguished. They are as follows: even-aged, relatively even-aged and uneven-aged stands.

Even-aged stands are those stands where trees are of even age with a precision of one year. Such stands practically are not met in nature, and only stands established by means of sowing or planting can be considered as the strictly even-aged ones.

Relatively even-aged stands are those in which the limits of age variation of individual trees does not exceed 20 years, i.e. one age class (as applied for most of coniferous species growing in Russia).

55 As uneven-aged are considered such stands where the range of age variation exceeds oneage class. These stands are highly variable since the age amplitude among trees may vary from 30 to 100 years or even exceed some 200 years in extremal cases. In such stands, several detached generations may be distinguished. However, many uneven-aged stands consist of trees which age is spread out over the whole age amplitude for the stand.

The described age structures seem to need more precise criteria than those presented above. Thus, within uneven-aged stands meant in a broader sense many authors also categorize purely (Shanin, 1965; Shurduk, 1979; and others) or absolutely (Komin, 1963) uneven-aged tree stands. The scientists often suggest to categorize age structure according to the age amplitude among individual trees and with respect to the coefficient of variation of this parameter (Bogdanov, 1971; Kudelya, 1988). Therewith, such larch stands in which the age amplitude does not exceed 40 years and the variation coefficient (C or V) make less than 5 percent are considered to be even-aged. Correspondingly, the relatively even-aged stands are distinguished at the age amplitude of 41 - 70 years and variation coefficient C = 5 - 12 percent, and uneven-aged at the age amplitude higher than 70 years and variation coefficient C = 35 - 40 percent.

Falaleev (1985) suggested to divide the whole variety of Siberian conifers to even-aged, relatively even-aged, and uneven-aged ones considering the growing stock per ha as a main parameter. According to the Falaleev’s criteria, the even-aged stands are those in which the trees are of the same generation, meaning that they differ in age not more than by one age class. In turn, the relatively even-aged stands are those in which not less than 90 percent of the growing stock is formed by the trees of any age group, such as: middle-aged, pre-mature, mature or over-mature trees. The uneven-aged stands are those in which less than 90 percent of the growing stock is made by trees of this or that age group.

Hence, in spite of some differences in methodological approaches various researchers obtain rather comparable results with respect to the age structure of larch stands and therefore, according to other features being measured.

Already the first studies carried out in larch forests of Siberia showed that - in spite of high light demands of Larix sp. - they are mostly uneven aged (Drobov, 1927; Abolin, 1929; Nedrigailov, 1932). Later on, it was found that wild fires are the main factor which influences the age structure of larch stands (Tikhomirov et al., 1961; Utkin & Isaev, 1962; Pozdnyakov, 1963, 1975; Chugunova, 1964; Shanin, 1965; Shcherbakov et al., 1979; Falaleev, 1985; Abaimov et al., 1990). According to Utkin (1965, p. 33) the pyrogenic factor "determines not only forest status but the whole course of their development beginning from regeneration to the stand decline". Both relatively even-aged and uneven-aged larch stands can be formed under forest fire impact depending on periodicity of reiterated fires in the same place, intensity of fire influence on tree stand, biological features of larch species revealed in fruiting specificity, site conditions, combination of climatic and weather regimes, etc. (Anon., 1994 a; Abaimov et al., 1996; Abaimov & Sofronov, 1996).

56 Figure 10. Even-aged, thicket of Larix gmelinii that regenerated after forest fire in the Putoran Mountains, Lat. 65° N. (photo: A.P. Abaimov, 1996)

Figure 11. Uneven-aged open stand of Larix gmelinii close to the northern timberline, Lat. 72°2ff N, Taimyr Peninsula, (photo: Bondarev, 1995)

57 On burned areas with the totally dead tree stand left, L. gmelinii and L. cajanderi form, as a rule rather successfully, even-aged or relatively even-aged young forests. A high reproductive potential of these species provides regeneration of the burned areas as soon as under 2-5 years, most often. Such post-fire larch thickets are characterized by an extremely high density. Approximately 250 - 300 thousands, sometimes 1.5 million larch seedlings per ha can grow there (Pozdnyakov, 1980,1986). Then, the stand density step­ wise decreases but it can be still 50 - 100 thousand trees per ha after some 40 - 50 years since fire. This high stand density is due to the process of self-thinning is strongly hampered in the permafrost zone.

At above described variant of succession the stand remains even-aged or relatively even-aged even when it becomes mature. However, this process is most often interrupted during consecutive 40-100 years period by the consecutive fire. In case of weak or moderately intensive ground fires, the only partial destruction of trees takes place thus the uneven-aged tree stand is formed later on this place. In different permafrost regions of Siberia, the stands with the oldest trees which have experienced 3-5 forest fires are often met.

It should be noted that the age structure of larch forests has been studied insufficiently with exception for the central and southern regions of Siberia. As far as the distant regions are concerned, the information with this respect to age structure is scant or does not exist at all. In most of papers the authors do not even distinguish the larch species, obviously not paying attention to it For example, in one of the first works concerning the relative distribution of larch trees in uneven-age stands (Shanin, 1965) is presented without taking into account the tree species (Table 4). These materials show that in uneven-aged and extremely uneven-aged stands of Siberia and the Far East the extend of distribution series makes 199 - 259 years while the age amplitude for some 90 percent of larch trees in even-aged stands does not exceed 40 years.

Table 4. Relative distribution (percent) of trees in individual age classes. Data concern both Siberian and Far East larch stands of different age structure (Shanin, 1965)

Stand Age classes, years age structure 41-80 81-120 121-160 161-200 201-240 241-300 even-aged - 1 91 8 - - relatively - 8 58 34 - - even-aged uneven-aged 3 11 51 31 4 - extremely 3 26 32 26 9 5 uneven-aged

An understanding of the age structure in stands formed by Siberian larch species may be enlarged when studying data put into Table 5. The evidences show that the even-aged or relatively even-aged larch thickets and stands are formed in different geographically

58 located burned areas. Both the age amplitude values and variation coefficients prove this statement

Table 5. Age structure of larch stands occurring in various regions of Siberia

Larch taxon Limits Mean Standard Variation Absolute Locality of age age deviation coefficient series’ age (Reference) years years years percent amplitude years

Larix cajanderi 7- 11 9 1.0 - 4 Yakutiya 10- 16 14 1.7 - 6 Lena River basin 6- 39 20 8.6 - 33, (Pozdnyakov, 32- 66 50 1.9 - 34 1975) 60 - 148 80 4.4 - 88 65 - 211 112 13.5 - 146 Larix cajanderi 14- 26 22 2.9 13.0 12 Yakutiya 24- 40 36 2.9 8.0 16 Lena River basin 32- 42 38 3.4 9.0 10 (Anon., 1994)

Larix gmelinii 105 - 152 126 2.7 - 47 Yakutiya, Olekma 92 - 153 132 11.0 61 River basin (Pozdnyakov, 1975) Larix gmelinii 12- 17 14 1.6 11.4 9 Krasnoyarsk 16- 24 20 2.0 10.0 8 ■ • ■ Territory 72- 92 86 5.9 9.7 20 ; middle flow of the 162 - 296 190 24.1 12.7 134 Nizhnaya Tunguska 178 - 260 190 28.3 15.6 82 River basin 145 - 273 195 34.6 17.7 128 (Abaimov, 148 - 286 229 45.5 19.9 138 unpublished data) Larix gmelinii 34 - 174 60 29.0 49.0 140 Krasnoyarsk 44 - 252 100 48.0 48.0 208 Territory 52 - 332 140 67.0 48.0 280 Khatanga River 59 - 387 180 85.0 47.0 328 basin 65 - 448 220 104.0 47.0 383 (Bondarev, 1995) 71 - 506 260 122.0 47.0 435

The majority of mature and over-mature stands are characterized by uneven age and by high variability of this feature. The higher the mean age the larger the absolute extent of the distribution series is observed. The absolute series’ age amplitude reaches its highest value, i.e. 435 years in the stand occurring on the Taimyr Peninsula, which average age makes 260 years, only (Bondarev, 1995). Also higher values of the variation coefficients which illustrate the feature variability are characteristic of extremely uneven-aged tree stands.

59 The data put into Table 5 do not confirm the supposition made by Pozdnyakov (1975) about decrease of of the share of uneven-aged larch stands and increase of the share of even-aged ones moving from the south to the north.

An interesting regularity has been revealed for Siberia by Andreev (1956). According to his data, the mean age in tree stands increases southwards. Based on this observation he drawn a conclusion that the forest vegetation displaces tundra over about 500 years, already. At the same time Morin (1958) - who has carried out his investigations in the northernmost sites of West Siberia - found that the mean age of the open L. sibirica forests is more or less the same there.

Shiyatov (1967) - who has studying the age structure of the larch stands in the Polar Urals - found that they consist of tree generations. He has drawn a conclusion that the reason for this phenomenon are cyclic climate variations which either support spreading out and regeneration or hamper regeneration and cause die-back of these forests.

An opposite opinion expresses Bondarev (1995). He says that the stands of of L. gmelinii at the northern timberline (Lat. 71-72° N) are characterised by a maximum uneven age. Their age structure shows clearly (Table 5) that supplementing of the stands with new generations is a continuous process and under extreme climatic and site conditions of high latitudes of northern Siberia is stretched over a long time. At the same time he did not find any essential variations in age structure of stands located south of the northern timberline.

Thus, formation of age structure of larch stands in Siberia is determined by a complex of factors the main of which are forest fires. Sometimes they result in even-aged but more often in uneven-aged tree stands. Selective cuttings and other anthropogenic activities also affect the age structure in the larch forests. However, these activities are not comparable in scale with forest fires which are the major destabilizing factor for the larch forests of Siberia.

5.2. Diameter structure

The diameter structure of larch stands is closely related to their age structure. The complexity of the latter makes DBH series larger and, usually, predetermines availability of some better or less clearly expressed maximums. In spite of absolute or relative distribution of trees with respect to DBH, the Russian scientists determine also the rank of the mean tree in stand. This index expresses in percent form the distance from the mean DBH tree and the thinnest one in the stand.

Many researchers assume that in relatively even-aged larch stands of Siberia the series of the DBH distribution resemble the standard curve with one peak and do not depend on tree species (Bogdanov, 1971; Shanin, 1965; Pozdnyakov, 1975; Falaleev, 1985; Kudelya, 1988; and others). The variation coefficient of the DBH distribution usually makes 25 - 32 percent, and the rank of the mean tree seldom exceeds 57 - 58 percent.

60 Mean DBH

□ 24 cm

W 28 cm

■ 36 cm

48 cm

Figure 12. DBH distribution in uneven-aged stands of Larix sibiricafrom the Eastern Sayan Mountains (Popov & Tikhomirov, 1940)

Figure 13. DBH distribution in uneven-aged stands of Larix cajanderi from the central Yakutiya (Kudelya, 1988; Anon., 1994 a)

61 Figure 14. DBH distribution in uneven-aged stands of Larix gmelinii from the Kheta River basin, Lat. 71° N, Taimyr Peninsula. (Abaimov, unpublished data)

Mean DBH

□ 6 cm | S3 8 cm j 110 cm j @ 12 cm !

Figure 15. DBH distribution in uneven-aged stands of Larix gmelinii from the central part of the Putoran Mountains, Lat. 68° N. (Abaimov, unpublished data)

62 The DBH distribution in uneven-aged and in absolutely uneven-aged larch stands is more variable than it is in relatively even-aged stands, and it periodically suffers essential disturbances from fire influence (Popov & Tikhomirov, 1940; Dzedzyulya, 1969; Korotkov & Dzedzyulya, 1969; Kudelya, 1988; Anon., 1994 a, Bondarev, 1995; Abaimov, unpublished data).

Under favourable climatic conditions, e.g. in the southern mountains ranges of Siberia (Popov & Tikhomirov, 1940) and in the central Yakutiya (Kudelya, 1988; Anon., 1994 a) the DBH distribution series are quite similar to those in the relatively even-aged stands, meaning that they also resemble a standard, one peak curve (Fig. 12 and 13). A number of thick trees in these series is limited and a mean tree rank seldom exceeds 58 - 60 percent, thus resembling the DBH series in the relatively even-aged stands even with respect to this index. With increase of the mean DBH in tree stands the number of thin trees decreases, while the relative frequence of trees which take an intermediate position in the series increases (Fig. 12 and 13).

Under less favourable climatic conditions in the northern part of Siberia, the DBH distribution series reflect a much more clear dominance of thin trees, especially in stands in which the mean DBH is low (Fig. 14 and 15). In some geographical points the rank of the mean DBH tree reaches 72 - 84 percent what shows absolute prevailing of thin trees. According to observations made by Bondarev (1995) this index varies in such stands from 46 to 66 percent The DBH series in stands with very low mean DBH (5 - 8 cm) are unimodal with sharply expressed right-side assymetry. As the mean DBH increases up to 10 cm, the series get polymodal with more or less clearly expressed frequency peaks (Bondarev, 1995).

In spite of presented differenciation of the DBH structure in larch stands, some general regularities should be noted. They are as follows:

* with increase of the mean DBH the series become longer * large differenciation of the age structure of the stands growing in the permafrost zone are not always reflected in their DBH series; the reason for this discrepances might be periodical fires which affect mostly the thinner trees; * with increase of the mean DBH the series become more flat symetric.

Generally, the three patterns of the DBH structure may be distinguished for the larch stands of Siberia:

1. A close to the normal (standard) distribution - characteristic of relatively even-aged stands; 2. Distribution described with decreasing curve and with sharply expressed right-side assymetry (converted J-shape) - characteristic of absolutely uneven-aged stands in which the age generation series cannot be distinguished; 3. Distribution taking the intermediate position between the two first, in which some weakly expressed frequency peaks may be identified - characteristic of stands which are periodically affected by forest fires.

63 5.3. Species composition

Species composition of larch stands of Siberia is determined in many respects by climatic and edaphic conditions, edificator role of the species as well as by influence of different natural and anthropogenic factors on forest ecosystems.

The term "edificator role" of given species is broadly applied in the Russian forest science, but it may be less known by foresters from abroad. According to the Forest encyclopedia (Anon., 1986) an edificator may be also called "creator" ."builder", and most often "main species". The "builders" are those plant species that determine the structure and to some extent the species composition of this phytocenosis in which they occur. A builder often dominate in the overstorey, have largest share in growing stock and expresses very high regeneration potential. In respective phytocenoses the builders are the successful competitors which supplant other species. In some cases, more than one tree species may be considered as a phytocenosis builder, e.g. in coniferous and mixed forests of West Siberia. There, Picea obovata, Abies sibirica, and Pinus sibirica together form the natural climax forest associations, thus are considered as a "collective phytocenosis builder", while forests consisting of deciduous species, such as Betula sp., Alnus sp. and Populus tremula that also occur in the same site conditions are of secondary character. Some species - which within their range of natural distribution are considered as poor competitors - may become very successful ones when occurring in special site conditions, e.g. Pinus sylvestris on sandy or peat bog soils or Larix gmelinii within the permafrost zone. A builder function is not given to any species for ever; it can be replaced by another species when the climate or edaphic condition get changed or if species in matter enlarges its ecological niche, thus becoming more expansive. A change of the builder species with another one is known in forest science as "change of the main species".

Individual larch species occurring in Siberia differ to some extent with respect to their role as a phytocenosis builder. L. sibirica is the main tree species only at the northern and the southern border of its range of distribution. In the north, large massives of low productive open or relatively dense forests (TV - V site quality classes) occupy vast areas there. Shares of Picea obovata, Pinus sibirica, Abies sibirica, birch and aspen usually do not exceed 20 - 40 percent.

In the south, the share of L. sibirica in species composition of stands increases with elevation above sea level. In different mountain regions, beginning from 700 to 900 m a.s.I. to the upper timberline (1900 - 2400 m), L. sibirica forms pure or mixed stands with small admixture of Pinus sibirica. For example, pure larch forests occupy slopes of different expositions in the Altai and Sayan Mountains at elevations higher than 900 m a.s.l. At lower altitudes, L. sibirica is successfully replaced with more shaddow- resistant conifers. On southern slopes L. sibirica is supplanted by Pinus sylvestris and Betula sp. Tree stands with Pinus sylvestris prevailing are formed also in lower parts of slopes of other expositions, however the share of L. sibirica, Pinus sibirica, Betula sp. and Populus tremula is usually large in their composition (Tikhomirov el al., 1961; Anon., 1969; and other).

64 In the contrary to the above described northernmost and southernmost sites, the role of L sibirica as a phytocenosis builder in a major part of its range of distribution is very low. Only seldom it forms small patches of larch forests. Such forests occur e.g. within basins of the Ob and Yenisei tributaries. Most often the share of L sibirica in mixed stands with prevalence of Pinus sylvestris, Pinus sibirica and Picea obovata is very low.

General presentation of species composition and productivity of stands of L sibirica in different parts of Siberia and in various forest types is given below (Table 6).

Table 6. Species composition and productivity of stands of L sibirica in different parts of its natural range of distribution (Tikhomirov et al., 1961)

Region Species composition Site Growing and forest type percent quality stock class m3/ha Tvumen ’ Province: Green-mossy 60 L.s., 40 P.o. + B.sp. IV 60- 110 Lichenous 100 Ls. V 40-60 Sphagnum 100 Ls. + P.o., B.sp. V 40-50 Republic of Altai: Riparian 100 Ls. n 559 Complex 100 Ls. n 444 Broadleaf-grassy 100 Ls. in 391 Lichenous 90 Ls., 10 P.s. V 100 Republic of Tuva: Grassy 90 Ls., 10 P.sp. ffl 275 Cowberry-grassy 100 Ls. + B.sp. m 260 Cowberry 70 Ls., 30 P.s. + P.o. in 257 Iris-grassy 80 Ls., 20 B.sp. IV 376 Wild rosemary 50 Ls., 40 P.s., 10 B.sp. V 180 Krasnoyarsk Territory Eastern Savan Mountains: Riparian 100 Ls. i 582 Green-mossy 100 Ls. + P.o., P.s. i 620 Grassy 70 L.s., 30 P.sylv. + B.sp. ii 445 Krasnoyarsk Territory Angara River basin: Grassy 100 Ls. + P.sylv. n 427 Green-mossy 50 Ls., 40 P.s„ 10 P.o. m 245 Long-mossy 60 Ls., 20 P.O., 10 P.s., rv 107 10 B.sp.+ P.t.

Explanations: Ls. - Larix sibirica Ledeb.; P.s. - Pinus sibirica Du Tour.; P.sylv. - Pinus sylvestris L„ P.o. - Picea obovata Ledeb.; B.sp. - Betula sp. "+" - share less than 10 percent

65 In mountain ranges of the Baikal Lake basin pure and mixed stands with larch prevailing are formed by two larch species (L sibirica and L. gmelinii) and their hybrid L. x czekanowskii. There are different combinations of the same coniferous and deciduous tree species in mixed tree stands as in other regions of Siberia (Anon., 1969; Panarin, 1977; Falaleev, 1985; and others). Larch share decreases sharply on dry sandy soils of southern slopes where it is replaced by Pinus sylvestris, while Pinus sibirica, Picea obovata and Abies sibirica dominate on fertile and well drained soils. Wild fires and cuttings cause the replacement of natural mixed forests with secondary ones. The restitution of the primary coniferous forests with dominance or with some share of larch species takes some 70 - 100 years.

Pure larch forest dominate in the major part of the Middle-Siberian Plateau. In the western part of this vast area tree stands are formed by L. sibirica. In the south, i.e. in the Angara River basin - where permafrost has "insular" character - occurrence of the l. sibirica stands is limited to small patches. Pinus sylvestris is the main species, there. Mixed stands consisting of Picea obovata, Pinus sibirica and Abies sibirica prevail only in river valleys and on flat watersheds.

In the permafrost zone - i.e. in the central, northern and eastern parts of the Middle- Siberian Plateau as well as within the North-Siberian (Taimyr Peninsula) lowland and in the lower flow of the Lena river - L. gmelinii dominates absolutely. In these areas it has no competitors practically and forms large massives of pure forests of different density. Picea obovata forms tree stands only in river valleys and on flat watersheds. L gmelinii occupies very different sites: watershed slopes of all expositions, plain areas, paludified lowlands as well as river valleys. Depending on site quality class the growing stock varies from 30 to 450 m3/ha (Table 7).

Both L. gmelinii and L. cajanderi supplant the admixed species on cold soils with shallow permafrost location and form pure larch forests. In the southern mountain area, L. cajanderi forms mixed stands together with Pinus sylvestris, Pinus sibirica, Picea obovata, Picea ajanensis, and Betula sp. (Anon., 1969; Anon., 1994 a). Mixed stands are formed on fresh or wet, rich soils with favourable temperature regime.

In the mountain regions of the north-east of Russia - i.e. in basins of the rivers Yana, Indigirka, Kolyma, and Anadyr - L cajanderi is as a main species in the major part of forest area. It forms open stands on slopes and dense forests in river valleys. Only in periodically inundated flood-plains it hasto compete with Chosenia arbutifolia (Pall) A. Skvorts.). However, the latter species does not grow in stands occurring on terraces of high flood-plains.

L. cajanderi stand structure and productivity depends on latitude and site conditions. The most productive forests occur in river flood-plains and on islands. On such places, L. cajanderi forms stands with growing stock from 220 to 450 m3/ha (Table 7).

Species composition is not stable even in virgin forests of Siberia. The change of the main species within natural range of distribution of Siberian larch species is determined by the complex of climatic, edaphic, biotic, and abiotic factors.

66 Table 7. Species composition and productivity of stands ofL. gmelinii and L. cajanderi in different parts of its natural range of distribution (Tikhomirov et al., 1961; Pozdnyakov, 1961 a, 1975; Utkin, 1965, Shcherbakov, 1975; Anon., 1994 a)

Region Species composition Site Growing and forest type percent quality stock class m3/ha Krasnoyarsk Territory Nizhnava Tuneuska River Basin: Green-mossy 100 Lg. + P.sylv., P.o. m 234 Wild rosemary 80 Lg., 10 P.s., 10 P.o. V 62 Lichenous 100 Lg. V 30 - 40 Renublic of Burvativa: Riparian 100 Lg. + P.o., P.s. n 380 - 450 Green-mossy 90 Lg., 10 P.o. in 345 Lichenous 100 Lg. V 70 Sphagnum 100 Lg. V 54 Renublic of Sakha Vilyui River basin: Cowberry 100 Lg. HI 150 - 320 Wild rosemary 100 Lg. IV 190 - 240 Sphagnum 100 Lg. V 70 Renublic of Sakha Indigirka River basin: Riparian 100 Lc. IV 220 Grassy 100 Lc. IV 250 Sphagnum 100 Lc. V 60

Renublic of Sakha Aldan River basin: Riparian 100 Lc. ra 190 - 415 Alpen rose 80 Lc., 20 P.sylv. m 200 - 250 Renublic of Sakha Lena River basin: Cowberry 100 Lc. ra-iv 150 - 320 Cowberry 100 Lc. + B.sp. rv-v 140 - 300

Explanations: Lg. - Larix gmelinii (Rupr.) Rupr.; Lc. - Larix cajanderi Mayr; P.s. - Pinus sibirica Du Tour.; P.sylv. - Pinus sylvestris L., P.o. - Picea obovata Ledeb.; B.sp. - Betida sp. "+" - share less than 10 percent; Republic of Sakha - Yakutiya

Not going so deep into a high number of theoretical problems reflecting various opinions of researchers about different forms of the change of the main species, its directions and

67 b

Figure 16. Some 20 thou, ha of larch forest perished in 1993 by wildfire in the central part of Evenkiya. (photo: A.P. Abaimov, 1995)

Figure 17. After two consecutive fires in 1902 and 1990, former larch (Larix gmelinii) stand has been replaced with birch which now regenerates by means of sprouts, central Evenkiya. (photo: A.P. Abaimov, 1995)

68 rates (Sukachev & Dylis, 1964; Kolesnikov, 1958; Smagin, 1965; Furyaev, 1996) we consider only some of them, such as the most typical scenarios depending on aging of stands and changes caused by forest fires. As it was said earlier, forest fires play the most substantial role in destabilisation of forest ecosystems. It should be noted that in Siberia arise annually about 30 thousand wild fires on the area approximately 5 million hectare (Valendik, 1996). Larch and pine forests are subjected to wild fires much more than other forests.

The collective monography "Structure and dynamics of taiga forests" (Sokolov et al. 1994) gives some information about aging effects on species composition in mixed stands with L. sibirica prevailing. For example in the Angara River basin the share of this species increases with time both in grassy and green-mossy forest types (Table 8). Nevertheless, even by maturity age L. sibirica does not provide the absolute prevalence in mixed tree stands. Moreover, wild fires and clear cuts result in change of such associations by secondary stands in which Betula sp. dominates. The reverse species change takes no less than 60 - 100 years when undisturbed by any factors. In the

Table 8. Aging related changes of species composition in the Angara River basin (Sokolov et al., 1994)

Forest types Age, Grassy Green-mossy years Species composition, percent 1 - 20 39 L.s., 5 P.sylv., 16 P.o. 34 L.s., 7 P.sylv., 8 P.o., 1 A.s., 38 B.p., 1 P.t 44 B.p., 6 P.t 21 - 40 42 L.s., 8 P.sylv., 8 P.o. 41 L.s., 7 P.sylv., 8 P.o., 2 A.s., 41 B.p., 1 P.t. 35 B.p., 7 P.t. 41 - 60 47 L.s„ 10 P.sylv„ 8 P.o. 44 L.s., 7 P.sylv., 6 P.o., 2 A.s., 33 B.p., 2 P.t. 34 B.p., 1 P.t 61 - 80 47 L.s., 10 P.sylv., 11 P.o., 48 L.s., 7 P.sylv., 7 P.o., 2 A..t„ 1 P.s., 33 B.p., 2 P.t. 28 B.p., 8 P.t 81 - 100 48 L.s„ 11 P.sylv., 13 P.o., 49 L.s., 9 P.sylv., 7 P.o., 1 A.s., 1 P.s., 24 B.p., 3 P.t 24 B.p., 10 P.t. 101 - 120 49 L.s., 10 P.sylv„ 16 P.o., 51 L.S., 10 P.sylv., 8 P.o., 1 A.s., 1 P.s., 21 B.p., 3 P.t 19 B.p., 11 P.t 121 53 L.s., 10 P.sylv., 14 P.o., 53 L.s., 11 P.sylv., 8 P.o., 2 A.s., and more 1 P.s., 16 B.p., 6 P.t. 15 B.p., 11 P.t.

Explanations: L.s. - Larix sibirica Ledeb.; P.s. - Pinus sibirica Du Tour.; P.sylv. - Pinus sylvestris L„ P.o. - Picea obovata Ledeb.; A.s. - Abies sibirica Ledeb.; B.p. - Betula pendula Roth.; P.t. - Populus tremula L.; "+" - share less than 10 percent;

69 northern part of West Siberia wild fires cause replacement of pure stands of L. sibirica by Betula sp. and Populus tremula stands as well (Tyrtikov, 1983).

In the central and southern regions of Yakutiya, where L. gmelinii and L cajanderi are the main species, the effects of fire and of aging with respect to species composition differ from those described for L. sibirica. Burned areas with dead trees left regenerate successfully and, as a rule, very fast In some cases the share of L. gmelinii or L. cajanderi in mixed species composition is high in other cases low, at the beginning. Nevertheless, larch species achieve a dominant role already at the age of 17 - 22 years (Table 9) and further maintain its position as a main species both in even-aged and unevenaged stands ((Fig. 18 and 19).

Table 9. Dynamics of species composition on burned areas in the central and southern regions of Yakutiya (Anon., 1994 a)

Duration Type Subsequent natural regeneration since and effects fire, of fire Species composition Density Mean age years percent thou./ha years I. Aldan River basin - L cajanderi 1 low fire, 10 Lc., 90 B.sp. 362.0 1 dead trees left 3 " 30 Lc., 70 B.sp. 172.0 3 5 " 20 Lc., 80 B.sp. 26.5 4 12 " 40 Lc., 60 B.sp. 3.9 10 17 " 80 Lc., 20 B.sp. 164.0 15 n. Lena River basin - L gmelinii 2 low fire, 70 Lg., 10 P.s., 10 P.sylv., 7.0 1 dead trees left 20 B.sp. 6 " 60 Lg., 30 P.o., 10 P.s. 12.5 4 9 50 Lg., 20 P.o., 10 P.sylv., 6.2 7 20 B.sp. 22 " 70 L.g„ 30 P.s. 9.0 14

Explanations: Lg. - Larix gmelinii (Rupr.) Rupr.; Lc. - Larix cajanderi Mayr; P.s. - Pinus sibirica Du Tour.; P.sylv. - Pinus sylvestris L., P.o. - Picea obovata Ledeb.; B.sp. - Betula sp.

In the permafrost zone, pure stands of L gmelinii or stands with low share of Picea obovata and Betula sp. are usually regenerated after wild fires without any change of the main species. Only sometimes L. gmelinii is replaced by Betula sp. on the flat ridges

70 20000 18000 16000 Larch 14000 I H Birch 12000 g 10000 * 3 Pine 8000 f 6000 § Density 4000 ° 2000 0

class,

Figure 18. Changes of species composition in even-aged, stands of Larix gmelinii from south-western part ofYakutiya (Anon., 1994 a)

800 700 600 a

t 400 % 300 |

200 ° 100 0

Age class, year

Figure 19. Changes of species composition in even-aged stands of Larix gmelinii from south-western part of Yakutiya (Anon., 1994 a)

71 that are up to 400 m a.s.1. high (Shcherbakov, 1992; Abaimov, 1995 b; Abaimov et al., 1996; Abaimov & Sofronov, 1996). As a whole L. gmelinii and L. cajanderi are adapted to permafrost conditions better than any other tree species of Siberia (Pozdnyakov, 1986) and they keep successfully this ecological niche which they succeeded to occupy in the evolution process.

Materials presented in this chapter do not pretend to detailed interpretation of the problems concerning species composition of Siberian larch stands and its changes. The aim was to show that species composition vary depending on growing conditions, age structure and such abiotic factors as forest fires. On the other hand, many problems are poorly studied till now, and available reference data are hardly comparable because of differences in the objectives and methods of study.

5.4. Growth rates

Seasonal growth in larch from East Siberia expresses the same general trends for each larch species studied (Batsenko et al., 1964). Stunted growth at the beginning and at the end of the growing period is characteristic of them. A similar phenomenon has been revealed in provenance trials carried out in the European part of Russia (Timofeev, 1961). Hence, the suggestion made by Leibundgut (1961) about distinguishing the period of a basic growth in larch seem to be reasonable. The basic growth in larch begins when some 10 percent of the height growth is realized and ends at the moment when some 95 percent of the whole seasonal increment is accomplished.

In the taiga regions of Siberia, such as Republic of Khakassiya, regions of Priangarie and Zabaikalie and the southern part of Yakutiya this period begins at the end of June (24 - 29.06), and is over by July 31 - August 3. The height growth in larch usually begins there at average daily temperature +15°C. Duration of the period of seasonal growth stepwise decreases when moving from the south-west towards the north-east.

Studies of growth rates in terms of DBH, height, basal area, growing stock and volume increment are of importance both for revealing optimal structures of stands growing in different site conditions and for planning such measures as thinnings and final cuttings. The first tables of growth rates for the larch stands in Siberia were made by Tikhomirov and Timoshchenkov in 1929. These tables reflected main features of growth dynamics in stands of L sibirica stands from Khakassiya. Somewhat later similar tables were made for stands of L gmelinii and L x czekanowskii growing in basins of the rivers Vitim and Olyokma (Galinovsky, 1938) and for stands of L. sibirica growing in the Altai mountains (Zolotukhin, 1958). Growth dynamics studies in stands of L. cajanderi growing in the Yana River basin were carried out for the first time by Pozdnyakov in 1961 (a). Later on, similar works took also place in other regions of Siberia. Never­ theless, it should be pointed out that until now there are no data from many regions where Siberian larch species grow.

Data presented in Figures 20 - 23 reveal very large differenciation in growth dynamics

72 4

I ooooooooooooooooooooooo <’3'frtnOv- fffr*PT*rpft*NNNWNN Age. years '1 Figure 20. Height growth in stands formed by Siberian larch species.

I - Larix sibirica, the Angara River basin, site quality class II (Anon., 1975) II - Larix sibirica, the Angara River basin, site quality class V (Anon., 1975) III - Larix gmelinii, the Lena River basin, site quality class I (Galinovsky, 1938) IV - Larix gmelinii, the Lena River basin, site quality class III (Galinovsky, 1938) V - Larix cajanderi, the Yana River basin, site quality class V (Pozdnyakov, 1961 a) i

!

10 -

5 - 0 -i—I—I—* —!—: I —■—!—<-----.----- 1 ■■!■■■ !-)—;■■■■ oooooooooooooooooooo n'tU)(ONCOO)0'*Nn'ttO(ON(SO)0'*CM Age. years Figure 21. Basal area in stands formed by Siberian larch species.

I - Larix sibirica, the Eastern Sayan Mountains, site quality class I (Anon., 1975) II - Larix sibirica, the Eastern Sayan Mountains, site quality class V (Anon., 1975) i III - Larix gmelinii, the Lena River basin, site quality class III (Galinovsky, 1938) IV - Larix gmelinii, the Lena River basin, site quality class V (Galinovsky, 1938) V - Larix cajanderi, the Yana River basin, site quality class V (Pozdnyakov, 1961 a)

I 73

WW7 A-..# It: 800

0------:------oooooooooooooooooooo o^ifliof^ooo^wco^iflior^coroOfN ^-T— T— V— ^T— «— CNOJCNJ Age. years Figure 22. Growing stock in stands formed by Siberian larch species.

I - Larix sibirica, the Eastern Sayan Mountains, site quality class I (Anon., 1975) II - Larix sibirica, the Eastern Sayan Mountains, site quality class V (Anon., 1975) III - Larix gmelinii, the Lena River basin, site quality class III (Galinovsky, 1938) IV - Larix gmelinii, the Lena River basin, site quality class V (Galinovsky, 1938) V - Larix cajanderi, the Yana River basin, site quality class V (Pozdnyakov, 1961 a)

8 -

0 ------:------:------,------,----- —r-, ooooooooooooooooooooooo C3^-«3C0fs*000)O'-C^C0^-lO

Age, years Figure 23. Average annual volume increment in stands formed by Siberian larch species.

I - Larix sibirica, the Eastern Sayan Mountains, site quality class I (Anon., 1975) II - Larix sibirica, the Eastern Sayan Mountains, site quality class V (Anon., 1975) III - Larix sibirica, the Angara River basin, site quality class II (Anon., 1975) IV - Larix gmelinii, the Lena River basin, site quality class III (Galinovsky, 1938) V - Larix cajanderi, the Yana River basin, site quality class V (Pozdnyakov, 1961 a)

74 of larch stands depending on geographic position and site quality class. For example, in different places L. sibirica forms stands which productivity expresses site quality classes from I to V. In the Eastern Sayan Mountains growing stock can make as much as 712 m3/ha on site of the quality class I by the age of 200 - 220 years (Fig. 23), while in the lower basin of the Angara River it is only 360 m3/ha in the same site conditions (Anon., 1975). Nevertheless, this larch species can form even more productive stands when grown on fertile and well moistened soils. At the same time in the northern part of its distribution - in the Khantayka river basin - the maximum growing stock at the age of 140 years does not exceed 128 m3/ha on site of the quality class V (Dzedzyulya, 1969).

Similar phenomena in growth dynamics are characteristic of L gmelinii , L. cajanderi and the hybrid L. x czekanowskii. Most of sites in the permafrost zone are evaluated as quality classes V and Va, thus the maximum growing stock of stands does not exceed 90-180 m3/ha at the age of 160 years (Galinovsky, 1938; Pozdnyakov, 1961 a; Shurduk 1979). However, in these extremely severe climatic conditions L cajanderi forms in river valleys high productive stands with growing stock up to 500 - 700 m3/ha (Pozdnyakov, 1975, 1986; Shcherbakov, 1975; and others).

More or less clear stabilisation of growing stock in stands formed by Siberian larch species is usually observed at the age of about 140 years but real decrease of the current annual volume increment begins later at higher site quality class and at lower latitudes (Tikhomirov & Tishchenkov, 1929; Galinovsky, 1938; Popov & Tikhomirov, 1940; Petrov, 1959; Pozdnyakov, 1961 a, b; Anon., 1975; Sokolov et al., 1994; Anon., 1994 a). Materials obtained by Russian scientists in different years prove that when growing under favourable conditions the Siberian larch species have high growth potential which is maintained up to 200 - 230 years and they may form stands with growing stock up to 700 - 800 m3/ha. Urns, the introduction of these species beyond the borders of their natural distribution should be successful.

75 6. Silviculture

6.1. Felling systems

Silvicultural measures as applied in the Russian Federation differ from each other in different bioecological zones. Forest management is organized according to both national and regional regulations. All forests are state owned, however they are administered and managed by individual administrative units of the Federation, such as republics, territories, provinces, autonomous districts, etc. (Anon., 1993). In terms of forest functions regarding biophesperic, ecological, social, and commercial importance, there are three categories of forests distinguished.

The first category consists of different kind of protective forests, such as: forests occurring in environs of towns and spas (health-resorts),forests of national parks, nature reserves and monuments, forests playing role of genetical reserves, etc. In Siberia, the open larch forests occurring within wide belt (50 - 300 km) south of the zonal tundra are also included to the first category. Their function is to protect the continent from cold arctic winds.

The second category consists of forests occuring in densely populated territories where also the network of roads, rail-roads, and other infrastructure is dense. Besides, water- protective forests along rivers and creeks and around water-reservoirs, forests at the altitudinal timberline, and forests within forest/steppe transitional zone are included to this category.

The third category consists of commercial forests in which takes place exploitation of forest resources as well "reserve" forests, i.e. forests which at the moment are inacessible to exploitation but which can become of commercial value in a future. Reserve forests occur in areas where population density is low and where infrastructure is poor. In Siberia, the harvest of timber takes place in commercial forests, exclusively.

Distinguishing of Russian forests into the above mentioned functional categories is of crucial importance, since felling and regeneration systems as well as utilisation of minor forest products in individual forests depends on their function.

There are not special regulations concerning felling systems in larch forests. Both thinnings and final cutting are the same both for pine and larch forests.

Within forests of the first category all kinds of felling systems, i.e. clear-cutting, shelter- wood and selective cutting, are accepted on condition that they are carried out in a way which strengthens ecological function of given forest and increases its stability.

In Siberian larch forests of the first category, the clear-cut system is applied only in plain areas. The area of harvest operations is limited to 5 ha, and its width should be no more than 50 m. A successful natural regeneration with sub-sequent growth is demanded. If there is risk of unsuccessful subsequent regeneration, then in even-aged larch forests the two-step shelterwood systems are applied. Besides, the two-step

76 shelterwood are the only systems which are accepted for even-aged larch forests of the first category growing on slopes. On gentle slopes (inclination less than 20°), at the first attempt the harvest should not exceed some 40 percent of growing stock and stand density should not become lower than 0.4 after this harvest The second attempt takes place, as a rule, after some 6-8 years, i.e. when new satisfactory advance growth of conifers is achieved (criteria defining "satisfactory stocking" vary in different regions, but generally it should be no less than 3 - 5 000 saplings/ha). If regeneration after the first attempt is not satisfactory, the interval between consecutive harvests may be prolonged and some additional measures, such as soil scarification, may be ordered. The total area of forests managed under this system in one place should not exceed 20 ha. On steep slopes, i.e. with inclination 21 - 30°, this area should be no larger than 10 ha, and the second attempt should take place after some 8-10 years (Anon., 1994 b).

Selective cutting is applied in uneven-aged larch forests. Harvest intensity at each attempt is some 20 - 40 percent of growing stock on plain areas and on gentle slopes (inclination less than 20°) and harvested area should not exceed 25 ha. Next attempt takes place after some 30 - 40 years. On steep slopes, in forests of the taiga/steppe transitional zone and permafrost zone the intensity should not exceed some 25 percent of growing stock. The interval between consecutive fellings is the same as in forests on plain territories, while maximal area is limited to 15 ha. Stand density after harvest should not be lower than 0.5.

Choice of the management (felling) system, maximal area and intensity of fellings, duration of intervals, etc. is related not only to the age structure and exposition but also is decided upon a number of other factors, such as species composition and health condition of the overstorey, as well as quality (stocking, spatial distribution, vertical sturucture, vigour, etc.) of already existing natural regeneration. Still, all the chosen system has to guarantee a successful implementation of the protective functions of these forests. Thus, the first goal to be achieved is a good quality of regeneration and the second - improvement or at least maintenance of age structure, spatial structure, species composition, etc. of the forest being exploited as they were before fellings.

In the forests of the second category, in even-aged larch forests which are equipped with successful advance growth (3-5 thou, saplings/ha), the clear-cutting is implemented. The width of clear-cut areas is 100 - 200 m, and their area varies from 10 - 20 ha, depending on site conditions. The consecutive harvest in close neighbourhood of given area can take place after some 4-5 years (Anon., 1994 b). In the permafrost zone, the clear cut area should not exceed 7 ha and its width is decreased to 70 m.

In uneven-aged forests, alike in forests of the first category, the two-step shelterwood fellings and selective cuttings take place. The only difference is the harvested area, which in this case varies from 20 to 50 ha. In forests of this category, the preservation of their functions is of highest importance, however they should also satisfy (at least to some extent) the needs for timber, that may be high in areas where forests of this category are distinguished.

In the commercial forests of the third category, the main goal is to satisfy demands for

77 goods of forest origin, first of all timber. In recent years the new regulations taking into consideration different forms of forest management have been developed. For example, the arenda system to the state and different forms of ownership, are deliberated. However, the control of the management rules and demands, regeneration, and protection against fires is still in responsibility of the local forest administration. They decide, in particular, upon ecological and silvicultural requirements limiting the choice of felling systems being implemented.

In Siberia, the main felling system applied in commercial forests is clear cutting. In even-aged larch and mixed forests occuring on plains and on gentle slopes, which are satisfactorily supplied with advance growth, the maximal with of clear cut areas should not exceed 500 m, and its area should be no larger than 50 ha. The interval between consecutive harvest in close neighbourhood should not be shorter than 4 years. In the mountain permafrost patches and in taiga/steppe transitional zone, the width of clear cut areas decreases varies from 250 m to 350 m, and their area from 25 ha to 35 ha, respectively. The next cutting may take place after 4-5 years.

In even-aged forests growing in such conditions as described above, which are not satisfactorily covered with advance growth of conifers, also clear cutting system is implemented. However, in such cases the attention is paid on achievement of good regeneration. Such measures, as seed trees left on clear-cut area (up to 50 trees/ha), soil scarification, enrichment planting or sowing of conifers, may take place.

On steep slopes of the Siberian mountain ranges, the two-step shelterwood felling is recommended. In such cases, the harvest intensity may be as high as 50 percent of the previous growing stock. The maximal area to be harvested is, even in this category of forests, 50 ha. Besides, the two-step curtain-shelterwood systems are implemented in such forests. The area of operation may be up to 30 ha in this case. The second attempt takes place after some 8-10 years. Harvest intensity is as above, i.e. 50 percent

In uneven-aged forests on plain and mild slopes conditions, the long-term sheterwood system is recommended. The maximal area is 50 ha, harvest intensity - up to 60 percent of the growing stock. However, after the first harvest the number of immature trees should be no less than 400/ha. The next harvest may take place no earlier than the trees which have been left become mature to harvest. In larch forests from the central and southern Siberia, the harvest age varies from 121 to 140 years.

The (regular) selective cutting are recommended for uneven-aged forests. Maximal area should not exceed 50 ha, harvest intensity should be no higher than 40 percent of the growing stock, and acceptable decrease of stand density after harvest 0.4. Next cutting in the close neighbourhood may take place after some 30 - 40 years.

In uneven-aged forests susceptible to wind damage also clear cutting is recommended. However, care have to be paid for a careful maintenance of existing saplings and poles (’tonkomer ’) from the understorey. The harvested area should not be larger than 25 ha, its width - no more than 250 m, and cutting in the close neighbourhood no earlier than after 5 years.

78 Slash is collected in form of small mounds or walls. The rules for the slash collection are decided by the local forest administration upon site conditions, quality of the advance growth, felling system, harvest season and other factors. On wet sites, the slash may be collected on skidding paths, and then pressed down with tractors. On dry, sandy soils, the slash is usually cut into small chips and distributed over whole area.

In order to achieve a better natural regeneration on clear cut areas, the collected slash is burnt. This measure is implemented when fire risk is as lowest. In many forest types, including those occurring in the permafrost zone, such a measure speeds up slash mineralisation which result in abundant regeneration. After winter season harvest, the slash is mixed with soil in a mechanic way.

In forests of the first and second category, the thinnings are implemented in order to regulate species composition (e.g. remove improper hardwoods, when regeneration of conifers is not achieved) according to the function of given forest and in order to increase their stability, improvement of ecological, esthetic and recreational values of these forests. The choice of thinning methods and intensity is related to the function of given forests.

The goals with thinnings in commercial forests are: to form an appropriate species composition and to secure good conditions for the fast growth of conifers. Thinning systems as applied within European part of Russia have a long-term expertise, while thinning operations in the Scots pine, stone pine and larch forests in Siberia are carried out during just a few decades.

There are four kinds of thinnings, two first of them being of a pre-comercial character. The goal with the first one is to clean, i.e. get rid of fast growing, mainly hardwood species, which otherways shaddow slower growing conifers. The goal with the second one is to make the thickets more open (Anon., 1994 b). Pre-commercial thinnings are implemented before the thicket is 40 years old. Their intensity depends on the thicket’s species composition and its primary density. Decrease of the latter should not exceed 0.5 - 0.4.

The goal with the third thinning (the first commercial felling) is to promote those trees which stem and crown are considered appropriate. They take place at the older of 41 - 60 years. The density after felling operation should be no lower than 0.8, but no more than 20 - 25 percent of primary growing stock may be extracted. Thinned trees in mixed stands are recruited from both higher and lower layer, while in pure larch forests - only from the lower layer.

The fourth thinning take place in stands 61-80 years old, which density is not lower than 0.9. The goal with this thinning is to maximize growth rates in conifers. The trees for felling are recruited mainly from below. Thinning intensity should not exceed some 15 - 20 percent of the primary growing stock.

All kinds of thinnings are planned in advance for a 10-year long period. Types and intensity of thinnings depend on silvicultural demands as well as on technical and

79 economic (no money to pay for the work, no possibility to sell) capacity of the forest administration.

Thinnings include even sanitary silvicultural measures. However, they are implemented in spite of the age of the forest. Most often, such thinnings are carried out in a selective way, however, in some cases even clear cut of affected stands may be necessary. In general, the intensity of such thinnings is lower than 30 - 40 percent of the primary growing stock.

6.2. Natural regeneration

Up to now, a lot of data on regenerative potential of the larch species have been accumulated. These materials allow to consider the main trends in their natural regeneration depending on geographical and edaphic conditions.

In the Altai and Sayan mountains forest of L. sibirica, the regeneration under overstorey depends mainly on the local climatic conditions influencing seed ripening and survival of germinants and seedlings, however species composition and forest type are also of a great importance (Tikhomirov et al., 1961; Anon., 1969; Falaleev, 1985; and others).

In the Altai Mountains, the most successful regeneration is observed in the cowberry and cowberry-herbaceous forest types (Lashchinsky, 1958, 1960; Rechan & Krylov, 1965) Number of advance growth individuals may be there as high as 20 - 40 thouVha. On the contrary, larch regeneration in the grassy-herbaceous and broad-herbaceous forest types is unsatisfactory. At the upper timber-line regeneration in the larch open forests runs rather well on slopes of the western and eastern expositions. In these sites, 10 - 25 years old advance growth may reach 2-3 thou, individuals/ha. In the mixed stands, advance growth of L sibirica is usually supplanted by more shaddow tolerant coniferous species, first of all by Pinus sibirica. Post-fire larch stand regeneration runs without change of species or with the short-term replacing of conifers by birch (Krylov & Krylov, 1969).

In general, natural regeneration of L sibirica in the Western Sayan and Eastern Sayan Mountains as well as in Kuznetsky Alatau is rather poor (Tikhomirov et al., 1961; Anon., 1969). It is mainly owing to strong competition from Pinus sibirica, Picea obovata, and Abies sibirica. About 3-5 thou, saplings of conifers per ha occur usually under overstorey of mixed species composition, however, as a rule, the larch share does not exceed 10-20 percent of the whole number of advance growth.

In the north of the West-Siberian lowland, natural regeneration of L. sibirica is also rather poor (Norin, 1958; Tyrtikov, 1979). In open and relatively dense forests of the Yamal Peninsula, the number of advance growth individuals varies from 800 to 7 000 but more often is no higher than 1 500 - 2 000 individuals/ha. Its species composition is determined by species composition of the overstorey. In the lichenous and mossy- lichenous types of open forests, the larch share varies from 90 to 20 percent, and is always less than its share in the main canopy structure. In result of forest fires and clear

80 cuts L sibirica is supplanted by Betula sp. and such secondary stands can be replaced with L sibirica no earlier than after some 100 - 150 years (Tyrtikov, 1979). According to opinion of this author, fires and clear cuts may also cause a replacement of the forest formations by the tundra bush associations for a long time.

In the Angara River basin L. sibirica occurs just as an admixture in species composition of mixed coniferous forests (see section 5.3.) It is reflected also in its regenerative potential under different ecological conditions. Number of advance growth in forests with prevalence of L. sibirica varies there from 9 to 14 thou, individuals/ha (Anon., 1969; Popov, 1982; Anon., 1994 b), however it is represented mainly by Abies sibirica, Pirns sibirica, and Picea obovata as well as by Betula sp. and Populus tremula. Advance growth of L sibirica is there extremely low in number. In larch forests of the green-mossy type 50 - 90 percent of advance growth fall on other conifers than L sibirica itself (Popov, 1982), while in some other forest types L. sibirica does not regenerate, practically. On burned and clear cut areas of the Middle Priangarie, a successful regeneration with conifers takes place in 50 percent of cases, with deciduous species in 25 percent of cases, and in 25 percent there is no regeneration at all (Farber & Sokolov, 1991). Overgrowing of cuttings and burned areas by shrubby vegetation supresses the natural regeneration not only that of L. sibirica but also of other conifers or it stretches out this process over a very long period. More often, L. sibirica regenerates only after preceding replacement by Betula sp.

According to Panarin (1965), L. gmelinii and L. x czekanowsUi regeneration runs most successfully in the Alpen rose (5 - 16 thouVha), cowberry (7 - 12 thouVha), and alder (3 - 10 thouTha) forest types in the mountains of the Baikal Lake basin. Natural regeneration is much poorer under unsufficient or excessive soil moistening. Advance growth under dense overstorey occurs in form of curtains and in clumps, while in open stands it is distributed rather evenly.

Regeneration of the clear cut areas is achieved owing to maintenance of the advance growth existing before felling operations and it usually secures dominance of the conifers. Ground fires, repeated periodically, stimulate the regenerative potential which result in successful forest regeneration with Larix sp. dominating already 3-5 years since harvest

Larch forests of the cowberry type occupy the major part of the forest area of the central and southern regions of Yakutiya. Number of advance growth individuals in the cowberry and cowberry-herbaceous forests types varies there from 3 to 19 thou, individuals/ha (Pozdnyakov, 1975,1986; Shcherbakov, 1975; Anon., 1994 a; and others). In the basin of the Lena River middle flow it is often even higher reaching 20 and more thouVha.

Soil moisture availability as well as root competition tensity are the main factors which determine the number and quality of advance growth of L. gmelinii and L cajanderi. The clumpy distribution of the advance growth points out a high importance of the root competition.

81 Figure 24. A successful regeneration of Larix gmelinii six years after ground fire, the central part of Evenkiya. (photo: A.P. Abaimov, 1996)

Figure 25. Vegetative regeneration of Larix gmelinii near northern timberline, Lat. 72°28> N, Taimyr Peninsula, (photo: A.I. Bondarev, 1995)

82 Natural regeneration of L. gmelinii and L. cajanderi on clear cut areas runs successfully and without any change of the main species. Sometimes this process stretches out for the period of 20 - 30 years. Burned areas are regenerated by these species much shorter, i.e. during some 3-5 years under condition that there are some seed trees left. The replacement of these species by Betula sp. is observed only if the fire was preceded by a number of poor seed years in Lari:c sp. and if the soil conditions got very favourable for regeneration of birch.

Within the Middle-Siberian Plateau in the permafrost zone, regeneration of L gmelinii is also determined by root competition for mineral substances and moisture in the active soil horizon between overstorey trees, ground vegetation and advance growth seedlings. The number of advance growth individuals varies there from 200 to 7 000 but more often it is 1 500 - 2 000/ha in the dwarf shrubby-green mossy and dwarf shrub-lichenous forest types (Abaimov, 1978, 1980, 1991; Abaimov et al., 1990; Shcherbakov, 1975, 1992). TTie importance of the root competition is proved there by a clumpy and curtain distribution of the advance growth as well as by its stunted growth. Nevertheless, this number of advance growth is high enough to replace gradually the dying off overstorey trees and to maintain a dominant position of L. gmelinii , if there are not any other destabilizing factors.

In comparison with not exploited forests, the forests in which limited in size (up to 10 ha) clear fellings took place, as well as the forests in which selective fellings were implemented do regenerate more successfully. This is owing to the decreased root competition from the overstorey trees. Number of the subsequent growth individuals on cut areas is most often as high as 5 - 10 thou./ha (Abaimov & Bondarev, 1992).

Ground fires are the very important ecological factor affecting not only the stand structure even promoting so called periodical "regeneration waves" (Utkin, 1965; Pozdnyakov, 1975). In forest affected by fires the natural regeneration with density as high as from 20 - 50 to 500 and more thouTha can arise during 3-5 years as a result of faster mineralization and thermal melioration of frozen soils (Matveev & Abaimov, 1980). Only seldom L gmelinii can be replaced for 40 - 60 years by Betula sp. in those sites where it is able to compete with L. gmelinii , i.e. the main phytocenosis builder on frozen soils of the central Siberia.

In the extreme climatic conditions at the northern and upper timberline, L. gmelinii paralelly with seed regeneration expresses the potential of regenerating in a vegetative way, mainly by rooting of the lower branches (Fig. 25).

In basins of the Yana, Indigirka, and Kolyma rivers, where climate continentality reaches its maximum and where permafrost is continuous, the natural regeneration of L cajanderi is most often satisfactory. Advance growth in different forests of different density can vary from 200 to 20 thou, individuals/ha (Pozdnyakov, 1975, 1986; Shcherbakov, 1975; Abaimov, 1980). However, its density usually makes only 1 500 - 3 000/ha in the cowberry forest type.

As in a case of L. gmelinii, clear cut and burned areas are regenerated by L cajanderi

83 during the first 3-5 years if there are seed trees. The number of seedlings of sub­ sequent growth may, in some cases, exceed 1 million individuals/ha (Pozdnyakov, 1986). However, if the seed crop in the year of cutting or fire is low, then the regeneration of L. cajanderi can be prolonged for many decades. A secondary tundra bush formation can be formed on large burned areas if all overstorey trees are dead because of fire. At such scenario, the recover of L. cajanderi can be impossible for a long time. In such a case only artificial regeneration by means of sowing or planting is needed (Boichenko et al, 1995).

As it was presented in this chapter, individual Siberian larch species express rather differentiated regeneration potential. L. sibirica endures competition of admixed conifers and deciduous species almost everywhere. Besides, wild fires and clear cuttings badly influence its ability to regenerate. In the southern part of their range of distribution L. gmelinii and L cajanderi win in competition with other tree species and, as a rule, keep their position as the main species successfully. In the permafrost zone, these larch trees practically have no competitors. In the evolution process they have adapted well to periodical fires and seldom lose the ecological niche occupied by them in favour for other species.

6.3. Artificial regeneration

6.3.1. Regionalisation of seed sources

Regions of seed sources for growing all main tree species, including larch, have been distinguished (Prokazin et al., 1982). As a rule, for artificial regeneration of larch species within each region, seeds from the same region should be used. However, in case of deficit, seeds from the adjacent regions can be accepted. In the mountain regions, transfer of seeds between elevations of their origin and their use should not exceed 300 - 400 m.

The seed source regions for all larch species occurring in the former Soviet Union are presented below (Fig. 26). Several of them are divided into subregions. The regions distinguished forL. sibirica are as follows: 12. Nizhneobsky, 13. Nizhneyeniseisky, 14. Nizhneirtyshsky, 15. Sredneobsky, 16. Sredneyeniseisky, 17. Angarsky, 18. Verkhne- lensky, 19. Tarsko-Chulymsky, 20. Yuzhneangarsky, 21. Kuznetsky, 22. Sayansky, 23. Pribaikal’sky, 24. Zaisansky, 25. Yuzhnoaltaisky, 26. Altaisky, 27. Yuzhnotuvinsky, 28. Buiyatsky. At present, a major part of these regions are within borders of the Russian Federation, while two of them (24 and 25) are in Kazakhstan. In the southern regions (21, 22, 26, 27, and 28) altitudinal subregions have been distinguished.

In spite of relatively narrow belt being occupied by L. x czekanowskii, as many as five seed source regions have been distinguished. They are as follows: 29. Putoransky, 30. Tungussky, 31. Prilensky, 32. Severobaikal ’sky, and 33. Yuzhnozabaikal ’sky. All of them have been divided into subregions either on areal or altitudinal basis.

84 - regions with the most favourable growing conditions where the most valuable larch genotypes occur 28 (Prokazin et al„ 1982) Within the range of natural distribution of L. gmelinii the following seed source regions have been distinguished: 34. Kotui-Olenyoksky, 35. Tungussko-Vilyuisky, 36. Nizhne- vilyuisky, 37. Srednelensky, 38. Vitimo-Olekminsky, 39. Shilkinsky, and Zeisko- Bureisky. In the southern regions (38, 39, and 40) altitudinal subregions have been distinguished.

Five seed source regions have been distinguished for L. cajanderi. They are as follows: 41. Nizhnelensky, 42. Yano-Indigirsky, 43. Kolymsky, 44. Centralnoyakutsky, and Aldano-Maisky.

The regions with the most favourable growing conditions are believed of being also the regions where the most valuable larch genotypes occur. Such regions (or subregions) for seeds of L. sibirica are 18a, 20, 21, 22, and 25a, while for seeds of L. gmelinii - 38, 39, and 40 (Fig. 26).

6.3.2. Seed cron and seed quality

Seed crop. Seed crops depend on many factors, such as: climatic zone, elevation, weather conditions in given year, soil fertility, stand age, stand density, tree position within the stand, etc. For example, seed crops in L sibirica from the Altai Mountains strongly varied depending on elevation above sea level (Lashchinsky, 1960). In years of high seed production, the seed crop was as high as 63 kg/ha at the elevation of 1100 - 1350 m, while at 1700 m a.s.1. it was only 12 kg/ha. In the Easterh Sayan (the Krasnoyarsk Territory), the seed crop in L sibirica substantially varied even within the same forest type depending exclusively on density of the tree-stand: from 47.7 kg/ha at the density 0.8 to 190.4 kg/ha at the density 0.3 (Verkhovtsev, 1940).

According to Danilov (1952) there are large differences in periodicity of seed crop in larch. Differences in this respect between West and East Siberia on the one hand, and between Altai Mountain and Zabaikalie on the other hand, are explained by this Author by different growing conditions as well as by specificity of larch species and ecotypes (Table 10).

However, the presented data are too schematic and not exact. In fact, L. sibirica does not occur in the European part of Russia (where it is replaced by L sukaczewii), neither in the Zabaikalie region (where instead occur L. gmelinii and L. x czekanowskii).

The long-term studies on the seed crop in L. sibirica, L. gmelinii and L. x czekanowskii from the Zabaikalie region were carried out by Milyudn (1983, 1984). It was found that seed crop in larch from this region was determined by both the features of given species and ecological factors. As a rule, L. gmelinii produces more seeds than L. sibirica, and years with high seed crop in L. gmelinii are more frequent than in L. sibirica. For 21 years (1961-1981), high seed crops were observed in L. sibirica only three times: in 1962, 1973, and 1980. At the same time L. gmelinii had 6 high seed crops: in 1962, 1967, 1971, 1973, 1977, and in 1980.

86 Table 10. Seed crops frequencies in L sibirica in different parts of its natural distribution. Avarage data for one decade (Danilov, 1952)

Region Seed crop high moderate low The European part of Russia 1-2 3-4 5 including the Urals West Siberia 1 4 5 East Siberia 2-3 4 4 Altai Mountains 1-2 4 4-5 Zabaikalie 3-4 4 2-3

L. gmelinii and L. sibirica occurring in the Zabaikalie region differ from each other in cone abundance even in the moderate crop years. However, in the high crop years L. gmelinii produces up to 18 thousand cones/tree. The highest number of cones once recorded on one tree of this species exceeded 38 thousand. At the same time L sibirica from Zabaikalie produced about 2000 cones per tree. Also in other regions, L sibirica (as well as L sukaczewii) seldom produced more than 1500 cones/tree (Pozdnyakov, 1975). However, the maximum 11.4 thousand cones/tree in L sibirica was recorded in the Altai Mountains (Lashchinsky, 1960).

The variation in the seed crop in larch in Zabaikalie is not larger than it is in other regions. For example, seed crop in L sibirica at the Baikal experimental station of the Sukachev Institute of Forest (the southern macroslope of Khamar-Daban) was in years 1971 - 1977 respectively: 2.1, 5.5, 30.9, 0.0, 7.7, 3.4, and 3.0 kg/ha; the average value for many years was 7.5 kg/ha (Milyudn, 1984).

In years with high seed crop in larch, the trees in most stands are covered with high amounts of cones. However, there are exceptions, e.g. in 1973 seed crop in forests of L. sibirica occurring in Predbaikalie (the basin of the Lena River upper flow) was low (less than 1 kg/ha), while to the contrary, in Khamar-Daban (Zabaikalie) it was very high (more than 30 kg/ha).

It is interesting that the seed crop in larch occurring at the Baikal Lake shore is high, practically, each year. The conventional scale of seed crop made for larch forests of the Baikal Lake basin is as follows: 0 kg/ha - nonexisting, 1-4 kg/ha - low, 5-10 kg/ha - moderate, 11-20 kg/ha - high, 21-30 kg/ha and more - very high.

Seed crop within the upper part of crown is most often higher than in other crown parts, but in trees of large diameter the middle part of crown is superior in this respect

The effect of tree size on cone production is remarkable. In larch stands of Zabaikalie in the years of average seed crop the cones are produced by some 40 - 60 percent of all trees, therewith the share of thicker trees (i.e. with DBH exceeding average) equals about 70 percent while the share of thiner trees makes 10 - 20 percent only.

87 In contrast to other larch taxons, the seed crop in Lx czekanowskii varies in a very large amplitude, which may range in the same year from 2 kg/ha in one region to 120 kg/ha in other one. Extremely high seed crop in L. x czekanowskii - reaching some 120 kg/ha - was once observed in forests of the park type (density 0.4 - 0.5) occurring in southern part of the Chita Province (Milyutin, 1984).

Populations of Lx czekanowskii as well as its parent populations occurring nearby characterizes poor and long-term seed dissemination due to their cones badly dehisce (Burovskaya, 1966; KarpeF, 1969; Kruklis & Milyutin, 1977; and others).

Burovskaya (1966) found that seed crop in L. x czekanowskii from the Podkamennaya Tunguska River basin substantially depends on seed damage degree caused by pests. Such damage make 70 - 90 percent in some years. So, at almost equal cone yield in 1963 and 1965 (38.5 and 39.3 thousand cones/ha, respectively) the seed crop in 1963 was as high as 6.5 kg/ha or 1.01 million seeds, and only 2.4 kg or 0.60 million seeds in 1965.

The percentage of seed craping trees as well a cone yield per hectare increase with increase of the stand age. In average, in stands 61-80 years old seeds were produced by some 40.4 percent of trees, in stands 141 - 160 years old 64.2 percent, and in stands older than that - 66.2 percent of trees. Cone crop in the same age classes was 25.5, 39.6 and 52.4 thousand/hectare, respectively. Cone production in L. x czekanowskii ends at the age of some 300 - 350 years (Burovskaya, 1966).

Seed crop in L. sibirica from the upper Lena River basin was studied by Shcherbatyuk (1969). During the 6 year study period (1959-1964), twice - in 1959 and 1964 - there were no cone production observed in this region, very poor cone yield in 1961; moderate in 1960 and 1963, and good in 1962. In the high crop year 1962, the amount of seeds produced varied from 12-38 kg/hectare.

Seed crop in L. cajanderi at the Yakutsk Experimental Station of the Sukachev Institute of Forest has been investigated for many years by Pozdnyakov (1975). The results of these studies showed that there were 14 crop years for the period since 1952 till 1974. During this period, the seed cropping of different intensity took place there in three (1959 - 1961) and even four (1967 - 1970) years in succession. In the high crop years, L cajanderi produced more than 65 kg of seeds per hectare.

Seed weight This parameter is widely used in respect to growing of seedling in nurseries, while in plant ecology it is, so far, considered as of minor importance. The weight (mass) of seed is closely related to the local climatic and site conditions. The weight of 1000 full seeds of L sukaczewii was found to be in close correlation with geographical latitude of stands where seed collection took place (r = - 0,78). The weight of 1000 seeds of L sibirica in Khakasiya, Tuva and Altai was found to be related to altitudinal zones and forest types (Deryuzhkin, 1970).

Kuzmina and Cherepnin (1973) found close connection between the weight of full seeds of L sibirica and the sum of effective temperatures higher than 5° (r = 0,84). This

88 allowed to calculate the regression equation: Y = 2.21 + 0.0033x, where "Y" is the weight (g) of 1000 filled seeds, and "x" is the sum of effective temperatures higher than 5°. These relationships are presented below (Table 11). The yield of seed crop in a given year does not have so high effect on the seed weight, e.g. in the southern part of the Krasnoyarsk Territory the average seed weight for the period 1949 - 1963 was 8.2 g, varying from 7.6 g in 1950 to 8.9 g in 1956. Thus, the highest deviation from the average seed weight was 0.7 g or 8,5 percent

Table 11. Relationships between the sum of effective temperatures higher than 5° and the weight of 1000 filled seeds of L sibirica

Sum of effective temperatures Weight of seeds, g 860-1160 5-6 1160-1460 6-7 1460-1760 7-8 1760-2060 6-9 2060-2300 9 and more (up to 10)

The highest seed weight in L sibirica (8.9 g) was observed in the southern taiga zone, i.e. in the Lena-Angara and Priangarie Plateaus, eastern Sayan Mountains, Kuznetsk Alatau and Salair. In some populations from these regions the seed weight was even higher reaching 9.3 - 9.6 g. The lowest seed weight in L. sibirica (3.8 g) was found in the Khantayka River basin at 68° N Lat The highest weight of L. gmelinii seeds (3 - 4 g) was observed in the southern Zabaikalie, and the lowest one (1,5 g) - in the Khatanga River basin (Taimyr Peninsula), in Putoran Mountains, and in the north­ western regions of Yakutia (Burovskaya, 1966; Medvedeva, 1971; Milyutin, 1984). The highest seed weight in Lx czekanowskii (5.6 g) was noted in populations of the southern Zabaikalie, while the lowest one (3.3 g) - in the Podkamennaya Tunguska River basin.

The seed weight in L cajanderi from the lower flow of the Lena River basin varies from 1.12 to 1.42 g (Medvedeva, 1971), while it is much higher (3.5 - 8.0 g) in populations of this species from the Central Yakutia (Pozdnyakov, 1961 b).

Endogenic variability of weight of 1000 full seeds of all the Siberian larch species is very low or low. Variation coefficients usually vary from 6 to 13 percent (Milyutin, 1983). Interrelation of seed weight with cone location within the crown has not been revealed. The heaviest seeds in the cone itself are formed more often in its middle part.

Weight variability of 1000 seeds within population is characterized by moderate levels (C = 16 - 24 percent). Besides, the variability of this index in different larch species populations is more or less the same. The relative high level of populational variability of 1000 larch seed weight is explained by large differences between individual trees in respect to the share of full seed.

89 Seed quality. Germination energy, technical germinating ability and share of full seeds depend on many factors and are extremely variable (Table 12).

Table 12. Seed quality of the Siberian larch species

Seed quality i n d i c e s, % Larch taxon germination technical share of energy germination filled seeds ability L sibirica 17-70 24-73 24-73 L gmelinii 11-76 18-77 23-84 L x czekanowskii 11-73 12-77 11-87 L cajanderi 49-64 45-81 33-69

Within the distribution range of L. sibirica has been distinguished a zone (streching from 52° to 58° N) in which the germination and germination energy of seeds are the highest (Deryuzhkin, 1970). In spite of large variability in seed quality of L gmelinii , this variables were found to decrease from the South to the North and from the West to the East In the latter case, this trend is less distinct (Milyutin, 1980). The influence of ecological conditions on seed germination is not proved but it was found to decrease under adverse conditions. Seed quality depends also on time of seed collection, though this is expressed less clearly than at seed weight.

Populational variability in seed quality is more or less the same in all Siberian larch species, and is characterized by the high variability level. Variation coefficients are equal to: for germination energy C = 19 - 47 percent, for germination ability C = 20 - 45 percent, and for share of filled seeds C = 18 - 58 percent.

6.3.3. Seed orchards

The Russian scientists and foresters are very experienced in larch selection as well as in seed-growing. In particular, the experience of establishing of the larch seed orchads in the former USSR is generalized by Veresin and others (1985). At the same time the significant specifity of species is likely not revealed. To establish the clonal seed orchards of different larch species the sites favourable for productive growth and with optimal hydrological as well as microclimatic regime should be chosen. In the forest zone weakly-podzolized, loamy forest soils rich in humus, nitrogen as well as in exchange bases, well drained, without gleyification and ortstein intercalation signs are well suited. Larch trees grow poorly at temporary stagnant surplus wetting, therefore a special attention should be paid to hydrological soil regime.

Ground waters must not be higher than 1,5 m. Before the orchard establishing the preliminary lime application is necessary if soil acidity is high. It is reasonable to enrich

90 the soil with 50 - 80 ton/ha of peat-mineral fertilizer in plots where mineral elements content is low and soil horizon structure is damaged because of stubbing and planning.

Such biological larch features as fast growth in the young age, wide crown, weak pollen dispersion should be taken into account at the seed orchard establishing. The trees are usually planted more far-between than the trees in spruce and even pine orchards. The most often the larch trees are planted 7 x 8 or 8 x 8 m, but therewith the orchard area is used not enough efficiently during the first 15 - 20 years. The distance between the tree rows should be wide, but in the row the trees should be planted more densely because of the weak pollen dispersion (such a tree planting is called the lane one). Tree planting in doubling rows in the chess-board order (the distance between the rows is 5 m, the distance between trees in the row is 6 m, which makes 278 trees/ha), provides the free crown development up to 20 years, and the yield per area unit is by 1,8 times higher than at 8 x 8 m tree distribution.

Forming of empty seeds at self-fertilization is typical of larch, therefore all the conditions for the cross pollination should be provided in orchards. The schemes of clone mixing can be very simple, it is necessary only that the trees of one clone are surrounded by the trees of others clones. The value of spatial isolation can be minimum, since the pollen disperses in the average at the distance equaled to one and a half of a tree height

The best method for establishing of larch clone orchards is the planting of engrafted young plants with closed root system. Sphagnous peat with fertilizers or mixing it with mineral soil is used as a substrate for stock growing. During one year annual seedlings reach the necessary size to be engrafted. After the engrafting they continue to be grown one more season. The digged out 2 - 3 year larch seedlings can be as stocks and engrafting can be realized also in the room during their winter rest. The age of seedlings must be 3 - 5 years in orchards made by engrafting on stocks.

Larch grafts (cuttings) are engrafted by different ways: by putting of their core close to cambium or cambium to cambium, by putting of graft to splitted place, by improved copulation (on the seedlings digged out). Grafts both with the top bud and without it (from the lower part of shoot) are used what increases the number of grafts by 2 - 3 times. The best time for grafting is the period of maximum cambium graft activity (beginning from April - May to August - September) except the period of intensive linear growth of shoots (June - July). Those cuttings prepared in winter as well as summer half-lignificated shoots are used as grafts. At grafting in the open place they are covered with the polyethilene bags.

As stocks for engrafting of different larch species the same or allied species can be used. In particular, there are good results when different larch species are engrafted on L sibirica. The grafts grow fast in the first years, up to 80 - 100 cm/year. To keep the engrafted cuttings they must be tied up to stakes.

Trees in the clone orchards begin to bloom in 3-5 years after engrafting, both female and male generative organs are formed. Differences between clones in blooming degree

91 and in seed harvest are large. Seed harvest in the orchards is small in the first decade, it makes 10 - 15 kg/ha in the second decade. Seed harvest is 20 - 25 kg/ha in the 15 - 20-year age of larch trees as the observations in Estonia show. In the orchards of the older age (up to 30 years) more than 70 kg/ha can be formed in productive years.

When establishing forest-seed larch orchards of the seed origin the planting of the 3 - 4-year young plants being distributed 8 x 8 m is the most efficient method. Tree fruiting begins in the age of 8 years. Seed harvest is 11 kg/ha at the age of 17 years, and from 12 to 29 kg/ha at the age of 20 years.

Establishing of the hybrid-seed orchards, i.e. orchards consisting of different species (or of various ecotypes of the same species) with the aim of mass obtaining of hybrid seeds resulted from natural interbreeding, is of very high importance. The method of obtaining of the first generation hybrid seeds (FI) from the specially selected tree species inter­ breeding of which gives the fast growing generation is based on the wide use of heterosis.

The methods of establishing of hybrid-seed larch orchards are successfully developed in Lithuania. Only abundantly blooming high productive plus larch trees are selected for the orchard establishing. For the abundant macro- and microstrobile forming on the grafts they should be taken from 80 - 120 year old trees, from the upper and the middle part of crown. The thorough selection of tree pairs according to agreement of blooming time both in the beginning and in maximum of pollen dispersion is necessary. Spatial isolation of the orchard from undesirable larch species must be not less than 50-100 m. Larch seedlings are distributed and planted in rows, the distance between rows is 8 m, between the trees in the row it is 6 - 8 m. The site should be open from all sides for better pollination of the whole tree crown by the wind and for prevention of fungal diseases. Annual cut of top shoots is applied for the trees are not more than 8 - 15 m high. The fertilizers are brought in, too. Tree protection from birds that may steal seeds, for example crossbills, as well as preventive measures against different pests are necessary as well.

There is a great experience for establishing of hybrid-seed larch orchards in the Southern Siberia (Avrov, 1977). The productive orchard is founded in Uzhursky region of the Krasnoyarsk Territory in spite of severe climatic conditions: damage of larch grafts by spring and autumn frosts and resulted from it losses of potential seed harvest as well as delay and late blomming, fruiting of grafts. Based on experimental study of many years L sibirica from the low mountain forests of the Kuznetsk Alatau, L. sukaczewii from the Middle Zauralie as well as some larch species from the Far East (L. lubarskii, L olgensis) are considered to be the most suitable for hybrid seed production in the Southern Siberia.

6.3.4. Seedling production in nurseries

There is a good experience of growing larch seedlings, mainly of those of L. sibirica. This species is grown, as a rule, on sandy-loamy and loamy soils since it grows poorly

92 on salinized, solonetz and surplus wetted soils. Organic fertilizers, sand and lime are brought into heavy cleyey soil.

Seeds before sowing are prepared in different ways, i.e. either by keeping under snow, or by soaking in water, or by staining. Keeping of seeds in 1 percent lime solution and in 0,03 - 0,05 percent potassium manganate solution during 1-2 days gives good results.

Larch should be sown in the early spring or in autumn. Sowing method is called the band, 6-line method. The norm of seed sowing is 3 g per 1 linear meter. Granulated superphosphate is brought into the soil together with seeds. The grooves are covered by loose substrate or by sand. During summer the weeds should be removed in the sown plants using herbicides and cultivation, fertilizers are brought in. Seedlings reach standard size at the age of 2 - 3 years in the taiga zone, and at the age of 1 - 2 years in the zone of mixed forests. The amount of standard seedlings is 1 - 2.2 millions/ha. These seedlings are used for establishing provenance trials as well as for growing young plants (during 3-4 years) in nurseries.

Larch seedlings are often grown in green-houses covered with the polyethilene. About 700 - 800 seeds per 1 square meter are normally sown. However, Kogan and Mosin (1988) suggest quite a low number of seeds - only 250 germinating and kept under snow - to be sown in green-houses. Optimal depth of seed sowing is 5 - 10 mm. The seedlings should be regularly watered, fertilized and loosened. Time for seedling growing makes 1 year. 10 millions of standard seedlings per ha can be obtained in this case. The growth of larch seedlings in the green-house is longer by 14 - 16 days than in open air, however this difference increases up to 20 days in the dry years (Gabeev, 1992).

There are not so many data concerning technology of planting material growing of other Siberian larch species and existing ones do not reveal the specificity of species in this technology except some details. So, it is recommended at growing of L. gmelinii seedlings in the Eastern Zabaikalie region to bring in the fertilizers to nurseries consisting of: nitrogen 80 kg/ha, phosphorus 80 kg/ha and potassium 80 kg/ha (1:1:1) (Bobrinev et al., 1988). Rooting of young plants grown from fertilized seedlings increases by 20 percent

Detailed study of growing L. cajanderi seedlings was carried out in the south of the Magadan Province. It was found that larch seeds should be sown in the given region in an open ground in the first decade of June, when soil surface gets heated up to 5° C, and in the sheltered ground - in the second decade of May, when the soil is heated so that air temperature in the night does not fall lower than 0° C. Larch seedling growth directly depends on soil temperature. In an open ground it is better to grow seedlings in beds, since the soil is heated here quicker and temperature remains by 2° C higher than in the flat area. Seed sowing with wetted fertilizer mixture is considered optimal. By doing so, 2-year old seedlings of L cajanderi should be suitable for use in commercial plantations.

93 6.3.5. Commercial plantations and provenance trials in the former Soviet Union

6.3.5.I. Within the range of natural distribution

Commercial plantations of larch species are much less common than those of pine. For example, in 1959 - 1968 larch cultures made 3.1 percent, and pine 84.9 percent of the total forest area in the Chita Province area, and in 1969 - 1978 they were 7.1 percent and 87.7 percent, respectively (Bobrinev et al., 1988). Among the reasons of this discrepance a shortage of larch seeds caused by rare seed years and harvest and their unsatisfactory quality should be mentioned fist of all.

Larch cultures began to be established in Siberia in the late years of the XIX century (experiments made by Gribanov near town of Omsk). The most favourable conditions for larch growing are, however, in the northern subzone of the forest-steppe transitional zone and in an altitudinal belt of light-needle coniferous forests of low mountains. Frost susceptible sites should be avoided, since early and late frost may damage the seedlings. A systematic damage may last untill the saplings will be 1.0 - 1.5 m high.

In Sibiria, L. sibirica is used for establishing of the commercial plantations more often than other Sibirian larch species. Larch cultures are established on fertile, moderately wet or fresh and air permeable soils. The abandoned arable lands can be used for this purpose as well. Larch cultures are most often established by means of planting. Sowing is applied rather seldom. Duration of the planting period in spring is strongly limited since larch begins to grow very early. Clear cut areas are regenerated in a regular way, while enrichment planting is a rule on those areas where occurs well maintained advance rowth or which are already covered by successful subsequent growth. Ordinary soil preparation consists of malting stripes or furrows. Complete soil preparation takes place only on bare places, in gaps, and on abandoned arable lands. Sites for sowing and/or planting are formed in rows.

Some 3 300 - 4 400 seedlings per ha are planted when establishing pure cultures. Commercial plantations of mixed species composition - in which a share of light­ demanding and fast-growing larch might be as high as 25 percent - are founded together with shade-tolerant and slower growing species, such as spruce, fir and other. Mixing is made by alternating larch seedlings with seedlings of the shade-tolerant species in the first row, and leaving the second row exclusively for the shade-tolerant species.

In spite of larch high competitiveness against weeds (Ogievsky & Medvedeva, 1977), regular weeding operations result in a much higher growth rate of larch seedlings. Since larch growth decreases almost twice at sod formation and soil compaction, soil loosening, is of high importance when growing this species in artificially made plantations.

In commercial plantations of the Eastern Siberia, seedlings of L. sibirica create a close canopy after some 5-10 years since planting. At this stage, the number of saplings varies from 900 to 2 800/ha and their height ranges from 0.7 to 1.8 m (Matveeva et al., 1986).

94 1

In terms of the average height, larch growing on soddy-podzolic loamy and grey forest ■V soils exceeds pine growing in similar conditions. On sandy soils larch grows at the same A rate or more slowly than pine. High productivity of the commercial larch plantations in many regions of Siberia lets suppose that being planted on the fertile soils these cultures can give artificial stands with growing stock of 800 m3/ha and more (Ogievsky, 1962).

Larch cultures characterized by high productivity occur in many places of Siberia. One :! of many examples could be the Bogotolsky leskhoz situated in the western part of the Krasnoyarsk Territory. A commercial plantation of L. sibirica at the age of 51 year had the average height 26.4 m, the average DBH was 20.5 cm, and the growing stock made 817 mVha. Another larch culture at 19 year of age (occurring in the same leskhoz) had the average height 11.3 m, the average DBH 8.6 cm, and growing stock 143 m3/ha.

It should be noted that a number of larch provenance trials have been established in Siberia during the last decades. Referring to the results shown in some published papers (Iroshnikov, 1967, 1977, 1984; Milyutin, 1967, 1995; Varaksin & Milyudn, 1996), a tentative conclusion may be drawn that in the most trials the local and neighbouring provenances express the best growth rate as well as the highest survival. Nevertheless, in a few cases some provenances of L. sukaczewii at the age of approximately 15 years 4 demonstrated better growth rate than the local provenances.

6.3.5.2. Beyond the range of natural distribution

The Siberian larch species began to be grown beyond its area as early as in XVIII century, however commercial planting in a larger scale took place first in the second half of the XIX century. Beginning from the second part of the current century the Siberian larch species are grown very wide (Timofeev, 1961,1977), e.g. during only five years (1951 - 1955) the commercial larch plantations of Siberian origin have been established on the area of 8.7 thou, ha in Ukraine and more than 5 thou, ha in Belarus’ (Tseplyaev, 1958). Among all Siberian larch species, L sibirica was of highest interest

L. sibirica was found as a very high productive species in many regions beyond its range of natural distribution. For example, in the Orel Province the 53-year old trees growing on the chernozem soils were in average 25 m high, their average DBH was 32 cm, and growing stock 612 m3/ha. At the age of 120 years, larch trees growing in the same conditions reached 37 m, 52 cm, and 895 m3/ha, correspondingly. In the Smolensk Province, the 87-years old larch stands growing on the thick-soddy loamy soils had the average height 33.5 m, average DBH 41.6 cm, and growing stock 567 m3/ha.

In 1961, Timofeev wrote: (p. 5 - 6) "The long-term experience of native silviculture ,~>i shows that in mixed coniferous/broadleaved forests as well as in the forest/steppe transitional zone of the European part of the USSR, larch is the highest productive tree species when establishing commercial, soil-protective, water-protective and recreation :3 forests. It does not grow here naturally, but it grows very well when introduced. Under these climatic conditions larch is characterized by durability, fast growth and high wood quality. Larch clearly expresses its excellent wind-resistance, its high capability to

95 a

X i:V '-.AV protect soil and water resources, its ornamental values as well as its resistance against wild fires, undesirable climatic phenomena, fungal diseases, and noxious insects.

When grown in the zone of mixed coniferous/broadleaved forests, larch exceeds by 20 - 50 percent all main local tree species - pine, spruce, oak, and birch regarding growth rate and wood quality".

L. sibirica that originates mainly from the Krasnoyarsk Territoiy and Khakassia, grows well in Latvia and other Baltic countries. However, Salinsh noted (1968) that larch grows not everywhere so well. Possibly, it could be explained by badly made selection of the ecotype for introduction. Besides, he noted that larch is growing well under strongly pronounced continental climate, therefore its growth is stunted in maritime humid climate, it is attacked by fungal diseases, and damaged by spring frosts.

Geographical regions within the European part of the former USSR that might be suitable for introduction of larch species were primarily distinguished by Tol ’sky (1938). Based on studies of average air temperature, total precipitation, and snow cover depth in the area of the most favourable growing conditions for larch within its range of natural distribution he determined three zones that border the west, south-west and south border-lines of the natural distribution of L sukaczewii. According to Timofeev (1961), these zones could be essentially enlarged.

As it was said already, mainly L sibirica was planted beyond its area of natural distribution. L gmelinii were grown there very seldom, and L. cajanderi practically was not grown at all (with exception for provenance trials). Having available data from just a few attempts in establishing of commercial plantations of L. gmelinii in the Vologda Province, Iroshnikov and Fedorova (1961) showed a lesser resistance of this species seedlings to early autumn frosts in comparison with L. sibirica and L. sukaczewii.

Special attention should be paid to numerous attempts in establishing of larch provenance trials in the former Soviet Union. The first such attempts were made in 1911 - 1915 (Ogievsky, 1916; Samofal, 1929). Later on, larch provenance trials (including its Siberian species) were established near Moscow (Timofeev et al„ 1947, 1961, 1977;), in the Moscow Province (Dementiev, 1969; Nadezhdin, 1971), in the Voronezh Province (Deryuzhkin, 1970), in the Arkhangelsk Province (VoichaT, 1967), in the Sverdlovsk Province (Khasanov, 1969), in Ukraine (Gursky & Dobrovolsky, 1967), in Kazakhstan (Lagov & Gavrilov, 1969), and in other regions of the former Soviet Union.

96 7. Existing experience and perspectives for introductions in northwest Europe

7.1. Commercial plantations

The genus Larix Mill, is a main tree component of the boreal forest of Eurasia. Over the Eurasian continent the proportion of larch is decreasing eastwards. Today, in northwest Russia the local species of larch is only a minor element of the natural forest and in Fennoscandia the natural occurrence of larch has been absent during historic time. However, recent geological findings has proved that larch was a natural component of the northern Scandinavian flora as late as 9 000 years ago (Wentzel, 1996). Similar findings from northern Finland indicate the same pre-historic presence of larch, west of its present range of natural distribution (Hirvas, 1983).

Larch of various species have attracted interest from foresters in Finland, Scandinavia and Iceland for a long time. Larch of central European origin (Larix decidua Mill.) was introduced into southern Scandinavia in the 1750s. Larch from Russia was introduced some 100 years later. Larix sukaczewii Dyl. - that only to some extent may be called the Siberian larch species (see chapter 3 and Putenikhin & Martinsson, 1995) - has been the only eastern larch species of any practical importance in the nordic countries. The earliest and the best known man-made larch commercial culture west of its present natural distribution, is the larch forest named Lindulovskaya Roshcha. In Finland, this site is called Raivola Forest Planting of larch there was initiated by the Tsar of Russia Peter the 1st in 1734 (Ilvesallo, 1923).

The earliest recorded proposal to introduce "Siberian" larch in Sweden was done by Carl von Linnd (Linneus, 1754). Most of the genetic material of Larix sukaczewii used in Finland, Scandinavia and Iceland during the last 200 years originates directly or indirectly via second generation seed crop in Finland, from the Raivola Forest or from the northern Arkhangelsk Province, which was a seed source for the Raivola Forest.

In the nordic countries, there is no official statistics over area covered with commercial cultures of larch species of Russian origin. In Finland, the total production of larch seedlings was 1.1 million during the period 1958 - 1976, which is corresponding to a planted area of approximately 1 000 ha (Hagman, 1987). Also in northern Sweden, larch cultures were established in the same period. The total area may have been of the same magnitude as in Finland. However, for many reasons (mainly shortage of seed sources) only a few of these plantations have been successful.

Before the 1960s Raivola Forest was the main seed source of "Siberian larch" used in the nordic countries. In addition to the Raivola some seed sources from the Arkhangelsk Province, were used, i.e. Mezen’, Pinega, Pechora, Shenkursk. Other seed sources used in a smaller scale in Finland and Sweden were Olonets in Karelia, Vologda, and Nizhny Tagil and Ufa in the Urals. From the end of the 1950s, also L sibirica Ledeb. that originated from Eastern Siberia was introduced in Finland and Scandinavia. These seeds were collected in the southern part of the Krasnoyarsk Territory, in Khakassia and in the Sayan Mountains. These seed sources were not tested under Scandinavian growing

97 conditions before use. Unfortunately, forest cultures established from these seeds were not successful. In Iceland, larch species from Russia are the most importrant among tree species used for afforestation. After 1951 more than 2 000 ha of larch plantations has been established in this country. The greater part, or more than 1 800 ha, have been afforested with L sukaczewii, mainly originating from seed orchards in Sweden or Finland, which means the genetic origin Raivola. L. sibirica, mainly from southern part of the Krasonyarsk Territory, was used on ppproximately 10 percent of this area.

In northern Sweden 21 small stands of Larix sukaczewii have been followed by repeated measurements (Martinsson, 1995). The main results of these investigations are presented in Fig. 27 and Table 13.

Hdom.m ^ ^ioo ,rn

100 Total age, yr

Figure 27. Course of development for dominant height growth of Larix sukaczewii in northern Sweden in 4 different site quality classes (Martinsson , 1995)

98 Table 13. Stem volume production ofLarix sukaczewii in northern Sweden (Martinsson, 1995)

Site index, H100, m Total age L27 L30 L33 L36 years Stem volume inch bark, m3/ha 25 30 55 91 141 30 57 94 143 211 35 88 135 197 282 40 120 177 252 353 45 153 220 307 423 50 186 262 361 491 55 219 304 413 556 60 252 345 465 621 65 284 385 515 684 70 316 424 564 745 75 348 463 612 804 80 379 500 659 862 85 409 538 704 918 90 439 574 749 973 95 467 609 792 1 026 100 496 643 835 1 078

In suitable sites, i.e. in forests of Vacccinium myrtillus type having a good drainage, the dominant tree height of larch could reach 36 m over a 100 years period, and the growing stock could be close to 1 000 m3/ha including bark (or some 800 m?/ha excluding bark). The height growth rate of 90 years old trees is still high.

The quality of site has a greater effect on the stem volume production of L sukaczewii than it has on the productivity of Scots pine (Pinus sylvestris L.). On sites suitable for larch growing in northern Sweden, the growing stock of larch exceeds that of Scots pine with 25 percent, but on dry, poor soils the productivity of Scots pine is superior to larch. Suprisingly good results of growth and survival were found at high altitude sites.

7.2. Provenance trials

Representative provenance trials of Siberian larch species does probably not esist anywhere outside the former Soviet Union (see chapter 6.3.S.2.). The provenance trials of Siberian larch existing in Scandinavia is a result of access to seed from certain areas and certain personal contacts. The biggest provenance trial of Siberian larch in Sweden is experiment plot 1881 in Stugun, that was established in 1964 and includes 30 various

99 sources of larch seeds, 8 of which L. sukaczewii and 22 of L. sibirica. As indicated in Fig. 28 the origins of seeds of the latter species are from the Krasnoyarsk Territory with a few exceptions.

After 32 growing seasons the mean tree height in this experiment is 10 m. Significant differences in growth rate between individual provenances may be easily revealed. As indicated in Fig. 29 most of the provenances of L sibirica are superior to those of L. sukaczewii, however they have poor survival. These two parameters may be negatively correlated to each other since few surviving trees achieve a large space on the plot. Another reason for the poor growth of L. sukaczewii provenances was an early attack by Chermes sp. In this case there was a clear difference in the attack intensity between the two larch species.

Figure 28. Seed origin for the experimental material used in experiment 1881, Stugun, Central Sweden

100 n rj I331 yrs 0 : [ M M |. 822 yrs 1 i 1 ~nT ! mu i ..I. It.lit j. tit II1 ritfi in t tt 1

42 54 • 5 10 11 12 54 5 4 15 14 15 16 17 15 10 20 21 24 25 21 27 20 50 51 55 30 40 42 55 Pa Lsuk(S) Larix sukaezewii Uuix siblrica

Fig. 29. Mean height of larch provenances in experiment 1881, Stugun, Lat. N 63°08', Long. E 15°2T, Alt. 385 m a.s.1, 31 years after planting. Lsuk (S) are non- autochtonous provenances, P.s. = Finns sylvestris

2.00 1.80 7 1-60 a. i.4o 8 1.20 s S 1-°° I °-8 ° t 1 Hi I 0.60 t t Tt tt tz t tt 0.20 tr 4 It 4- 0.00 1 JL_L 1 1 1 l 4__ L 1 1 4. 4. 1 1 4. 4- JL 1 |B|i| + 4—41 42 54 6 9 10 11 12 34 3 4 13 14 IS 16 17 IS 19 20 21 24 25 2S 27 28 30 31 33 39 40 58 Pa

Lsuk(S) Larix sukaezewii Larix sibirica

Figure 30. Stem straightness of trees in experiment 1881, Stugun. Degree of straightness: 0 indicates a straight stem, 3 means a severely crooked stem

101 Stem straightness is an important character for breeding and selection of seed source. When comparying various provenances that are tested in experiment 1881, significant differences may be found (Fig. 30). Unfortunately, there seem to be a positive correlation between slow growth and straight stem. The local alloctone seed source 54 Visingso demonstrates good combination of straight stem and fast growth in the experimental plot 1881, Stugun. This seed source is the result of a seed import more than 100 years ago. In 1982, some 80 kg of larch seeds was imported from Arkhangelsk and then distributed to 67 different sites all over Sweden. The more than 100 years old larch stand in Visingso in southern Sweden is one of a few still existing larch forests originating from this introduction.

A younger larch trial that was established in northern Finland, also demonstrated a better survival of L sukaczewii than of L. sibirica from south-central Siberia. The relation of mean height was the opposite (Table 14).

Table 14. Survival and mean height of L. sibirica and L. sukaczewii in experiment 46 near Rovaniemi, Lat. N 66°29 r, Long. E 26°42', Alt 220 m a.s.l., 18 years after planting (Hagman, 1987)

Species Origin Survival Mean percent height, m Altai 6.7 3.21 LatN 52°, Long.E 85°, Alt 700 m a.s.1. Altai 14.7 4.58 LatN 52°, Long.E 85° L. sibirica Khakasiya 8.0 4.70 LatN 53°, Long.E 90° Khakasiya 10.6 4.77 LatN 54°50', Long.E 89° 10' Ekaterinburg (Sverdlovsk) 34.7 3.75 L sukaczewii LatN 54°50', Long.E 89°10' Arkhangelsk 81.3 3.61

Also in Iceland L. sukaczewii show a better adaptation to local growing conditions than L. sibirica, most often (see Fig. 31). However, in some cases provenances of L. sibirica havedemonstrated high production and a good stem form, e.g. high altitude seed sources from the Altai Mountains and those from Irkutsk.

102 k

4

,1 103 7.3. Conclusions and practical advice

Some cultures of L. sukaczewii in Finland, northern Scandinavia and Iceland were successful and are good examples of man-made larch forests, especially those established during the period of 1900 - 1930. In most cases the seed source is unknown, but probably of the second generation Raivola origin. Nevertheless, none of them has been established with seeds originating east of the Urals. The main conclusions to be drawn from existing experience in growing larch in this part of Europe are:

Larch has a positive influence on the ground vegetation and the soil conditions. The ground vegetation gets changed into a grass or herb cover, while the corresponding vegetation in Scots pine forests consists mainly of dwarf shrubs. Under a larch canopy, the pH-value of soil horizons just under a surface and on the depth of 15 cm is significantly higher than under a Scots pine canopy.

Timber quality in terms of branchiness, stem straightness and annual ring width, are characters which could be improved in larch. Untill now, larch was grown mainly in single-species plantations. A mixture with other tree species, for instance spruce, could have a positive effect on branchiness, especially on fertile soils. Pruning of dry branches is probably a necessary measure for elimination of dry knots in lumber, which is a common defect of larch timber at present. Stem straightness in larch could be improved by a carefully selection of seed sources. An early elimination of individual trees with a bad growth habit is another measure needed.

Larch is a typical pioneer species. When grown under too favourable conditions, larch demonstrates very fast growth rate at the beginning, which results in too wide annual rings. Thus, if planted on fertile soils, e.g. on former farm lands, larch should be exposed to a hard competition at an early stage. This can be achieved by direct sowing of larch seeds or by establishing cultures with mixed species composition. Norway spruce (Picea abies), Douglas fir (Pseudotsuga menziesii), maple (Acer platanoides and/or A. pseudoplatanus) or linden (Tilia cordata) are shade tolerant tree species, which could be intermixed with larch. A result of such a mixture could be two-storey stands.

A big size lumber is a preferable high quality larch wood product In order to achieve a continuous and even growth rate over a long rotation period, early and frequent thinnings are of high importance. The green tree crown should be kept vital and it should not be too small.

104 8. Concluding remarks

Considering Siberian larch species ecology, the extremely important environmental role of larch forests of Siberia cannot be forgotten. Recently, the significance of larch forests in a carbon balance and in other processes connected with global warming on the Earth is widely discussed (Schulze et al., 1995, and others). It is stressed that the boreal forests of Siberia - consisting of larch on more than a half of their area - are about two times larger than their North American counterpart (Gower & Richards, 1990). These forests make about 35 percent of wood resources of Russia (Sominsky & Melnichenko, 1985) and some 16 percent of carbon captured by the world terrestrial ecosystems are concentrated in their biomass and soils (Kolchugina & Vinson, 1993).

It should be also mentioned that larch trees are very sensitive to any environmental change and respond to them by variation in diameter growth as well as in tree-ring structure. In this connection larch species are an optimal subject for dendrochronological studies connected with problems of climate change and with other ecological issues (Vaganov, et al., 1996; and others).

105 References

Abaimov, A.P. 1977. Morfologicheskaya izmenchivost’ khvoi listvennitsy v basseine r. Vilyui, In: Listvennitsa [Morphological variability of larch needles in the Vilyui River basin. In: Larch], 8:38-48, Sib. Techn. Inst., Krasnoyarsk, Russia. (In Russian) Abaimov, A.P. 1978. Some pecularities of natural forest regeneration at the head of the Vilyui River. In: Larch and its use. 9:38-44, Krasnoyarsk, Russia Abaimov, A.P. 1980. Listvennitsy Gmelina i Kayandera (sistematika, geografiya, izmenchivost’, estestvennaya gibridizaciya) [Larix gmelinii and Larix cajanderi (systematics, geography, variability, and natural hybridisation)]. PhD Thesis, 24 pp., Krasnoyarsk, Russia. (In Russian) Abaimov, A.P. 1991. Estestvennaya i antropogennaya dinamika vozobnovleniya pri- tundrovykh lesov Srednei Sibiri. In: Ekologicheskie problemy sokhraneniya i vos- stanovleniya lesov Severa [Natural and antropogenic dynamics of pre-tundra forest regeneration in the central part of Siberia. In: Ecological aspects of preservation and restoration of forests in the North], 56-59, Arkhangelsk, Russia. (In Russian) Abaimov, A.P. 1995 a. Struktura prirodnykh populyacii listvennitsy Gmelina po okraske molodykh shishek v kriolitozone Srednei Sibiri. In: Botanicheskie issledovaniya v Sibiri [Structure of Larix gmelinii natural populations from the permafrost zone of the central part of Sibiria in terms of the young cone colour. In: Botanical studies in Sibiria], 4:4-11, Krasnoyarsk, Russia. (In Russian) Abaimov, A.P. 1995 b. The larches of Siberian permafrost zone and their species pecularities in progressive successions. Proc. IUFRO S2-02-07 Workshop: Larch genetics and breeding (Ed. O. Martinsson). Swedish Univ. Agri. Sci., Dept, of Silvi­ culture, Reports, 39:11-15, July 31 - Aug. 4, 1995, Umea, Sweden Abaimov, A.P. & Bondarev, A.I. 1992. Lesovodstvennaya otsenka rubok v pritundro- vykh lesakh Srednei Sibirii [Silvicultural assessment of fellings carried out in pre- tundra forests of the central part of Siberia], Lesn. Khoz., 8-9:26-28. (In Russian) Abaimov, A.P., Bondarev, A.I. & Tsvetkov, V.F. 1990. Kratkii ocherk listvennichnykh lesov severo-vostoka Evenkii. In: Sevemye lesa: sostoyanie, dinamika, antropogennoe vozdeistvie [Brief description of larch forests of the nort-eastem part of Evenkiya. In: Boreal forests: state, dynamics, antropogenic impact], Proc. Int. Symp., 2:3-12, Moscow, Russia. (In Russian) Abaimov, A.P. & Karpel’, B.A. 1978. Ob izmenchivost! shishek listvennitsy v zapadnykh raionakh Yakutii. In: Listvennitsa i ee ispol ’zovanie [About variability of larch cones in the western Yakutia. In: Larch and its use]. Trudy Sib. Techn. Inst., 9:38-44, Krasnoyarsk, Russia. (In Russian) Abaimov, A.P., Karpel’, B.A. & Koropachinsky, I. Yu. 1980. O granitsakh arealov sibirskikh vidov listvennitsy [On range of natural distribution of Siberian larch species]. Bot. Zhum., 65,1:118-120. (In Russian) Abaimov, A.P. & Koropachinsky, I. Yu. 1979. O polimorfizme listvennits Gmelina i Kayandera [About variability of Larix gmelinii and Larix cajanderi]. Izv. Sib. Otd. AN SSSR, series Biol., 5,1:38-44, Novosibirsk, Russia. (In Russian) Abaimov, A.P. & Koropachinsky, I. Yu. 1984. Listvennitsy Gmelina i Kayandera [Larix gmelinii and Larix cajanderi]. 120 pp., Izd. "Nauka", Novosibirsk, Russia. (In Russian)

106 Abaimov, A.P. & Milyutin, L.I. 1995. Sovremennye predstavleniya o listvennitsakh Sibiri i problemy ikh izucheniya. In: Problemy dendrologii [Recent ideas on Siberian larch species and research needed. In: Issues of dendrology]. Proc. Xllth Sukachev Memorial Conf., 41-60, Novosibirsk, Russia. (In Russian) Abaimov, A.P., Prokushkin, S.G. & Zyryanova, O.A. 1996. Ecologo-fitocenoticheskaya otsenka vozdeistviya pozharov na lesa kriolitozony Srednei Sibiri [Eco-phytocoeno- logical estimation of wild fires effect on forests of the permafrost zone in the central part of Siberia]. Sib. Ecol. Zhum., 1:51-60. (In Russian) Abaimov, A.P. & Sofronov, M.A. 1996. The main trends of post-fire succession in near­ tundra forests of Central Siberia. In: Fire in ecosystems of boreal Eurasia. (Eds. J.G. Goldammer & V.V. Furyaev). Forestry Sciences, 48:372-386, Dortrecht - Boston - London Abaimov, A.P., Zyryanova, O.A. & Korotkov, LA. 1995. Tipologicheskaya struktura pri- tundrovykh lesov Krasnoyarskogo kraya. In: Problemy pritundrovogo lesovodstva [Typological structure of pre-tundra forests in the Krasnoyarsk Territory. In: Silvi­ culture in pre-tundra forests]. 104-115, Arkhangelsk, Russia. (In Russian) Abaimov, A.P., Zyryanova, O.A., Mikhailova, LA., Moroz, S.N. & Shitova, S.A. 1995. Kompleksnoe kartografirovanie pritundrovykh lesov centralnoj chasti plato Putorana [Complex mapping of pre-tundra forests in the central part of the Putoran Mountains]. Geogr. i Prir. Resursy, 3:158-165. (In Russian) Abolin, R.L 1929. Geobotanicheskoe i pochvennoe opisanie Lensko-Vilyuiskoi ravniny [Geobotany and soils of the Lena-Vilyui Plain], Trudy Komm. po Izuch. YaSSR, 10, 378 pp., Izd. AN SSSR, Moscow, Russia. (In Russian) Aleksandrova, V.D. 1937. Tundry pravoberezhiya reki Popigai [Tundras of the Popigai River basin]. Trudy Arkt. Inst, series Geobotanika, 63:181-207. Leningrad, Russia. (In Russian) Andreev, V.N. 1956. Zaselenie tundry lesom v sovremennuyu epokhu. In: Rastitel’nost ’ Krainego Severa i ee osvoenie [Colonisation of tundra with forest under recent times. In: Vegetation of the Far North and its management], 1:27-46, Izd. AN SSSR, Moscow - Leningrad, Russia. (In Russian) Anon. 1962. Atlas Irkutskoi oblasti [Atlas of the Irkutsk Province]. 182 pp., Gl. Upr. Geod. i Kartogr., Moscow-Irkutsk, Russia. (In Russian) Anon. 1967. Atlas Zabaikal’ya [Atlas of Zabaikal’e]. 176 pp., Gl. Upr. Geod. i Kartogr., Moscow-Irkutsk, Russia. (In Russian) Anon. 1969. Lesa SSSR [Forests of the Soviet Union], 4, 768 pp., Izd. "Nauka", Moscow, Russia. (In Russian) Anon. 1975. Khod rosta osnovnykh lesoobrazuyushchikh porod Sibiri, chast’ II [Growth rates in main tree species of Siberia, 2nd part]. 196 pp., Krasnoyarsk, Russia. (In Russian) Anon. 1993. The Forestry Act as applied in the Russian Federation. 63 pp., Izd. Ekos- inform, Moscow, Russia. (In Russian) Anon. 1994 a. Lesa srednetaezhnoi podzony Yakutii [Forests of the middle taiga sub­ zone in Yakutiya]. 140 pp., Yakut Nauch. Centr, Yakutsk, Russia. (In Russian) Anon. 1994 b. The forest systems recommended for East Siberia. 38 pp.. Federal Forest Service of Russia, Moscow, Russia. (In Russian) Avrov, F.D. 1977. Rost privoev listvennitsy razlichnogo proiskhozhdeniya. In: Geo- graficheskie kul’tury i plantacii khvoinykh v Sibiri [Growth of larch grafts of

107 different origin. In: Geographical cultures and plantations of conifers in Sibiria], 124- 153, Izd. "Nauka", Novosibirsk, Russia. (In Russian) Batsenko, A.A., Milyutin, L.I., Petrenko, E.S. & Kruklis, M.V. 1964. Dinamika sezonnogo prirosta listvennitsy v vysotu v razlichnykh raionakh Vostochnoi Sibiri [Dynamics of seasonal height growth of larch from various regions of East Sibiria]. Bot Zhum., 49,11:1629-1632. (In Russian) Beissner-Fitschen. 1930. Handbuch der Nadelgeholzkunde. 3 Auflage, 765 pp., Berlin, Germany Bobrinev, V.P., Kotel ’nikov, A.M., Rylkov, V.F., Bondar ’, P.A., Sekachev, G.V. & Bobrovnikova, N.D. 1988. Vosproizvodstvo lesnykh resursov v usloviyakh Vostochnogo Zabaikal’ya [Restoration of forest resources under conditions of the eastern Zabaikal’e]. 112 pp., Izd. "Nauka", Novosibirsk, Russia. (In Russian) Bobrov, E.G. 1961. Introgressivnaya gibridizaciya vo flore Baikal’skoi Sibiri [Natural hybridisation in the flora of the Baikal region in Sibiria]. Bot. Zhum., 46,3:313-327. (In Russian) Bobrov, E.G. 1972. Istoria i sistemadka listvennits [History and systematics of larch species]. 95 pp., Izd. "Nauka", Leningrad, Russia. (In Russian) Bobrov, E.G. 1978. Lesoobrazuyushchie khvoinye SSSR [Main conifers in forests of the Soviet Union]. 188 pp., Izd. "Nauka", Leningrad, Russia. (In Russian) Bogdanov, V.M. 1971. Osobennosti vozrastnoi struktury listvennichnykh nasazhdenii Yugo-Zapadnoi Yakutii. In: Issledovaniya po lesnomu khozyaistvu [Age stmcture of larch stands in the south-western part of Yakutiya. In: Investigations on forestry issues]. 39-55, Izd. "Lenizdat", Pskov, Russia. (In Russian) Boichenko, A.M., Isaev, A.P. & Protopopov, A.V. 1995. Pritundrovye listvennichnye redkolesiya na mezhdurech’e Yany i Indigirki i voprosy lesopoFzovaniya. In: Problemy pritundrovogo lesovodstva [The pre-tundra open larch forests growning between Yana and Indigirka rivers with respect to their utlisation. In: Silviculture in pre-tundra forests]. 138-146, Arkhangelsk, Russia. (In Russian) Bondarev, A.I. 1995. Stroenie i normativy taksacii pritundrovykh lesov severo-vostoka Krasnoyarskogo kraya [Structure and mles of inventorisation of the pre-tundra forests in the north-eastern part of the Krasnoyarsk Territory], PhD Thesis, 22 pp., Krasno ­ yarsk, Russia. (In Russian) Burovskaya, E.V. 1966. Plodonoshenie listvennichnykh drevostoev v basseine srednego techeniya Podkamennoi Tunguski [Seed crop in larch stands from the Podkamennaya Tunguska River basin], PhD Thesis, 22 pp., Krasnoyarsk, Russia. (In Russian) Cheremkhin, S.S. 1961. Lesa verkhnego techeniya reki Vilyuya. In: Materialy o lesakh Yakutii [Forests at the head waters of the Vilyui River. In: Forests of Yakutiya], 7:243-260, Izd. AN SSSR, Moscow, Russia. (In Russian) Chudnyi, A.V. 1982. Sostav terpentinnykh masel i taksonomiya listvennitsy v SSSR [The composition of terpen oils and taxonomy of larch in the Soviet Union]. Leso- vedenie, 3:32-40 (In Russian with English summary) Chugunov, B.V. 1961. Vozobnovlenie lesa v Yugo-Zapadnoi Yakutii. In: Materialy o lesakh Yakutii [Forest regeneration in the south-western part of Yakutia. In: Forests of Yakutiya]. 7:260-323, Izd. AN SSSR, Moscow, Russia. (In Russian) Chugunova, R.V. 1964. Gari Yuzhnoi Yakutii i ikh vozobnovlenie. In: Lesa Yuzhnoi Yakutii [The burned areas of the southern part of Yakutia and their regeneration. In: Forests of the southern part of Yakutia]. 32-40, Izd. "Lesn. Promyshl.", Moscow,

108 Russia. (In Russian) Conrad, V. 1947. Usual formulas of continentality and their limits of validity. Transact, of Amer. Geophys. Union, 27,5:663-664 Danilov, D.N. 1952. Periodichnost ’ plodonosheniya i geograficheskoe razmeshchenie urozhaev semyan khvoinykh porod [The periodicity of seed crop and geographical distribution of seed sources for coniferous species]. 60 pp. "Goslesbumizdat", Moscow, Russia. (In Russian) Dement ’ev, P.I. 1969. Zapiski lesnichego [Forest ranger ’s notes]. 2nd Ed., 101 pp., Moscow, Russia. (In Russian) Deryuzhkin, R.I. 1970. Selekciya i kul’tury listvennitsy v Centralnoi lesostepi. In: Lesnaya genedka, selekciya i semenovodstvo [Selection and larch cultures in the central part of the forest/steppe zone. In: Forest genetics, selection and seed management]. 203-209, Petrozavodsk, Russia. (In Russian) Deryuzhkin, R.L & Latysh, V.G. 1975. Efimoe maslo kak diagnosticheskii priznak vidov i raznovidnostei listvennitsy. In: Nekotorye voprosy genetiki i selekcii rastenii [Terpen oils as a diagnostic character in larch species. In: Some aspects of genetics and plant selection]. 12-19, Voronezh, Russia. (In Russian) Deryuzhkin, R.I., Livadin, M.V. & Latysh, V.G. 1971. Khimicheskii sostav efimykh masel nekotoiykh vidov listvennitsy [Chemical composition of terpen oils in some larch species]. Sbor. Trudov Voronezh. Lesotechn. Inst, 33:86-88, Moscow, Russia. (In Russian) Drobov, V.P. 1916. Obshchii ocherk rasdtel ’nosti v basseinakh rek Nizhnei Tunguski i Vilyuya [Vegetation of the Niznaya Tunguska and Vilyui river basins. A general description]. 101-119, Izd. Pereselencheskogo Upr., Petrograd, Russia. (In Russian) Drobov, V.P. 1927. Kratkii ocherk rastitel’nosti Lensko-Aldanskogo plato [Vegetation of the Lena-Aldan Plateau. A brief description]. Mat Kom. po Izuch. Yakutskoi ASSR, 60 pp., Izd. AN SSSR, Leningrad, Russia. (In Russian) Dugaqav, C. 1995. Larch forests of Mongolia. PhD Thesis, 392 pp., Krasnoyarsk, Russia Dylis, N.V. 1947. Sibirskaya listvennitsa [Siberian larch. Materials on taxonomy, geography, and history], Moskov. Obshch. Issled. Prir., Series "Botany", 2:1-137, Moscow, Russia. (In Russian) Dylis, N.V. 1959. O genedko-selekcionnym i botaniko-geograficheskom znachenii kontakta arealov listvennits sibirskoi i daurskoi [About genetic and geobotanical consequences of the neighbourhood of Larix sibirica and Larix dahurica ranges of natural distribution], Soobshch. Inst Lesa AN SSSR, 11:3-13, Moscow, Russia. (In Russian) Dylis, N.V. 1961. Listvennitsa Vostochnoi Sibiri i Dal’nego Vostoka [Larch species of East Siberia and the Far East]. 209 pp., Izd. AN SSSR, Moscow, Russia. (In Russian) Dylis, N.V. 1981. Listvennitsa [Larch] 96 pp., Izd. "Lesn. Promyshl.", Moscow, Russia. (In Russian) Dzedzyulya, A. A. 1969. Lesovodstvenno-taksacionnye osobennosd listvennichnykh lesov basseina reki Khantaiki [Silviculmral and inventory features of larch forests of the Khantaika River basin]. PhD Thesis, 28 pp., Krasnoyarsk, Russia. (In Russian) Egorov, O.V. 1961. Ekologiya i promysel yakutskoi belki [Yakutian squirrel: Ecology and hunting], 266 pp., Izd. AN SSSR, Moscow, Russia. (In Russian) Falaleev, E.N. 1985. Lesa Sibiri [Forests of Siberia]. 135 pp., Krasnoyarsk, Russia. (In Russian)

109 Farber, S.K. & Sokolov, V.A. 1991. Analiz khoda lesovosstanovitel ’nykh processov na vyrubkakh i garyakh Ust’-Ilimskogo lesopromyshlennogo kompleksa po tipam lesa. In: Ispol ’zovanie i vosstanovlenie resursov Angaro-Eniseiskogo regiona [Analysis of regeneration processes on clear cut and burned out areas in respect to various forest site conditions in the Ust’-Dim Forest District. In: Exploitation and regeneration of forest resources in the Angara-Yenisei region], Conf. Proc., 240-247, Krasnoyarsk - Lesosibirsk, Russia. (In Russian) Filimonov, B.K., Kukuev, Yu.A„ Strakhov, V.V. et al. 1995. Lesnoi fond Rossii (po uchetu na 1 yanvarya 1993 g.) [Forests of Russia (State on Jan., 1st, 1993)]. 280 pp„ All-Russian Research and Inform. Centre for Forest Resources, Moscow, Russia. (In Russian) Furyaev, V.V. 1996. Rol ’ pozharov v processe lesoobrazovaniya [Role of fires in restitution of forests]. 253 pp., Izd. "Nauka", Novosibirsk, Russia. (In Russian) Gabeev, V.N. 1992. Ekologiya vyrashchivaniya khvoinykh [Ecology of growing conifers]. 187 pp., Inst. Lesa i Drev. Sib. Otd. AN SSSR, Krasnoyarsk, Russia. (In Russian) Galinovsky, V.N. 1938. Listvennichnaya taiga Vostochnoi Sibiri [Larch forests of East Siberia]. Lesn. Ind., 4,5:19-23. (In Russian) Gower, S.T. & Richards, J.H. 1990. Larches: deciduous conifers in an evergreen world. BioScience, 40:818-826 Gursky, V.V. & Dobrovolsky, V.I. 1967. Geograficheskie kul’tury listvennitsy [Provenance trials of larch], Lesov, i Agrolesomelior., 9:116-122, Kiev, Ukraine. (In Russian) Hagman, M. 1987. Experiences with Larix species in northern Finland. Proc. IUFRO Sl.05-12 Symp., Aug. 12-22, 1987, Rovaniemi, Finland Hirvas, H. 1983. Correlation problems of interglacial deposits in Finnish Lapland. In: Quartemary glaciations in the northern hemisphaere. (Eds. A. Kelty, O. Cochon & S.W. Shutton) IGCPS-session, 14 Sept. 1983, Paris, France Igoshina, BLN. 1963. Listvennitsa na Urale [Larch in the Urals]. Mat. po Istorii Flory i Rastit SSSR, 4:462-492, Izd. AN SSSR, Moscow - Leningrad, Russia. (In Russian) Evessalo, L. 1923. Raivolan lehtikuusimesta. Referat: Der Larchenwald bei Raivola. Comm. For. Finn., 5, 100 pp. (In Finnish) Iroshnikov, A.I. 1967. Opyt geograficheskikh posevov listvennitsy v Sibiri. In: Geo ­ graficheskie aspekty gomogo lesovedeniya i lesovodstva [Expertise in larch provenance trials in Sibiria. In: Geographical aspects of mountain forestry], 116-119, Chita, Russia. (In Russian) Iroshnikov, A.1.1977. Geograficheskie kul’tury khvoinykh v Sibiri. In: Geograficheskie kul’tury i plantacii khvoinykh v Sibiri [Provenance trials of conifers in Siberia. In: Provenance trials and commercial plantations of conifers in Siberia], 4-110, Izd. "Nauka", Novosibirsk, Russia. (In Russian) Iroshnikov, A.I. 1980. Problemy selekcii i vnutrividovoi differenciacii lesnykh drevesnykh rastenii v rabotakh V.N. Sukacheva. In: Problemy lesnoi biogeocenologii [Problems of breeding and intraspecific variability of forest woody plants in the research works carried out by V.N. Sukachev. In: Problems of forest biogeo ­ cenology]. 15-33, Izd. "Nauka", Novosibirsk, Russia. (In Russian) Iroshnikov, A.I. 1984. Introdukciya listvennitsy v Yuzhnoi Sibiri. In: Izmenchivost’ i introdukciya drevesnykh rastenii Sibiri [Introductions of larch in the southern part of

110 Siberia. In: Variability and introductions of woody plants of Siberia]. 19-31, Krasno ­ yarsk, Russia. (In Russian) Iroshnikov, A.I. & Fedorova, A.I. 1961. K voprosu o vyzhivaemosti khvoinykh porod na vyrubkakh Severa pri ikh kul’ture posevom. In: Voprosy lesovodstva i leso- vedeniya [Survival rates in conifers on clear cut areas of the North after regeneration by means of sowing. In: Perspectives in silviculture]. 49-63, Krasnoyarsk, Russia. (In Russian) Iroshnikov, A.I. & Fedorova, A.I. 1974. Nekotorye mekhanizmy adaptacii listvennitsy sibirskoi k usloviyam Severa [Some mechanisms of Siberian larch adaptation to the northern conditions]. Tezisy dokl., 5:5-13, Izd. Yakut Filial Sib. Otd. AN SSSR, Yakutsk, Russia. (In Russian) Isaev, A.P. 1993. Listvennichnye lesa srednetaezhnoi podzony Yakutii i leso- vozobnovlenie na vyrubkakh [Larchforests of the middle taiga subzone in Yakutiya and subsequent natural regeneration on clear cut areas], PhD Thesis, 21 pp., Krasno ­ yarsk, Russia. (In Russian) Karpel’, B.A. 1969. Sbor, obrabotka i khranenie semyan zapadnoi formy listvennitsy daurskoi (prakticheskie rekomendacii) [Collection, processing and storage of seeds of the western form of Larix dahurica (practical recommendations)]. 7 pp., Yakutsk, Russia. (In Russian) Karpel’, B.A. 1971. Plodonoshenie i kachestvo semyan listvennitsy daurskoi v Yugo- Zapadnoi Yakutii. In: Issledovanie rastitel’nosti i pochv v lesakh Severo-Vostoka SSSR [Seed crop and seed quality in Larix dahurica from the south-western part of Yakutiya. In: Studies on vegetation and soils in forests of the nort-eastem part of the Soviet Union]. 52-68, Yakutsk, Russia. (In Russian) Karpel’, B.A. 1974. Plodonoshenie daurskoi listvennitsy v Yugo-Zapadnoi Yakutii [Seed crop in Larix dahurica from the south-western part of Yakutiya]. PhD Thesis, 22 pp., Krasnoyarsk, Russia. (In Russian) Karpel’, B.A. & Medvedeva, N.S. 1977. Plodonoshenie listvennitsy daurskoi v Yakutii [Seed crop in Larix dahurica from Yakutiya]. 119 pp., Izd. "Nauka", Novosibirsk, Russia. (In Russian) Kashin, V.I. & Kozobrodov, A.S. 1994. Listvennichnye lesa Evropeiskogo Severa Rossii [Larch forests of the European North of Russia], 221 pp. Izd. Arkh. Fil. Russ. Geogr. Obshch. RAN, Arkhangelsk, Russia. (In Russian with English summary) Khasanov, N.H. 1969. Geograficheskie posevy listvennitsy na Srednem Urale. In: Lesnaya selekciya, semenovodstvo i introdukciya v Kazakhstane [Provenance trials in the Central Urals. In: Forest selection, seed management and introduction of tree species in Khazakhstan], 50-54, Alma-Ata, Kazakhstan. (In Russian) Kogan, A.M. & Mosin, V.I. 1988. Vyrashchivanie seyantsev khvoinykh porod v teplitsakh s polietlenovym pokrytiem. In: Problemy lesovosstanovleniya v taezhnoi zone SSSR [Growing seedlings of conifers in greenhouse with polyethylen cover. In: Forest regeneration in the taiga zone of the Soviet Union], Tezisy dokl. konf., 112- 113, Krasnoyarsk, Russia. (In Russian) Kolchugina, T.P. & Vinson, T.S. 1993. Equilibrium analysis of carbon pools and fluxes of forest biomes in the former Soviet Union. Can. J. For. Res., 23:81-88 Kolesnikov, B.P. 1946. K sistemadke i istorii razvitiya listvennits sekcii Pauciseriales Patschke. In: Materialy po istorii flory i rastitel’nosti SSSR [Systematics and development history of Larix sp. sect. Pauciseriales Patschke. In: Materials on history of flora and vegetation of the Soviet Union], 2:321-364, Izd. AN SSSR, Moscow, Russia. (In Russian) Kolesnikov, B.P. 1958. O geneticheskoi klassifikacii dpov lesa i zadachakh lesnoi nauki v vostochnykh raionakh strany [On genetic classification of forest types and about goals of forest science in the eastern part of the country]. Izv. Sib. Old. AN SSSR, 4:3-15. (In Russian) Kolycheva, E.N. I960. Plodonoshenie i posevnye kachestva semyan daurskoi listvennitsy [Seed crop and seed quality in Larix dahurica]. Trudy po Lesn. Khoz. i Lesn. Promyshl. Zabaikal’ya, 1:117-120, Chita, Russia. (In Russian) Komarov, V.L. 1934. Klass Coniferales. In: Flora SSSR [Class Coniferales. In: Flora of the Soviet Union]. 1:130-195, IZD. AN SSSR, Leningrad, Russia. (In Russian) Komarov, V.L. 1953. Kratkii ocherk rastitel’nosti Sibiri. Izbrannye sochineniya [A brief description of vegetation of Siberia. Selected works]. 9:9-215, Izd. AN SSSR, Moscow, Russia. (In Russian) Komin, G.E. 1963. K voprosu o tipakh vozrastnoi struktury nasazhdenii [On types of age structure of tree-stands]. Lesn. Khoz., 3:37-41. (In Russian) Koropachinsky, LYu. 1983. Drevesnye rasteniya Sibiri [Woody plants of Siberia]. 383 pp„ Izd. "Nauka", Novosibirsk, Russia. (In Russian) Koropachinsky, LYu. & Milyutin, L.I. 1964. Introgressivnaya gibridizaciya listvennits sibirskoi i daurskoi v yuzhnoi chasti ikh arealov. In: Selekciya drevesnykh porod v Vostochnoi Sibiri [Natural hybridisation of Larix sibirica and Larix dahurica in the southern part of their ranges of natural distribution. In: Selection of tree species in East Siberia]. 20-31, Izd. "Nauka", Moscow, Russia. (In Russian) Korotkov, LA. & Dzedzyulya, A.A. 1969. Lesa basseina reki Khantaiki. In: Tipy lesov Sibiri [Forests of the Khantaika River basin. In: Forest types in Siberia]. 2:230-242, Krasnoyarsk, Russia. (In Russian) Kruklis, M.V. 1974. Kariologicheskie osobennosti listvennitsy Chekanovskogo (Larix x czekanowskii Szafer). In: Izmenchivost ’ drevesnykh rastenii Sibiri [Karyological features of Larix x czekanowskii Szafer. In: Variability of woody plants in Siberia], 11-19, Krasnoyarsk, Russia. (In Russian) Kruklis, M.V. & Milyutin, L.L 1977. Listvennitsa Chekanovskogo [Larix x czekanowskii Szafer], 210 pp„ Izd. "Nauka", Moscow, Russia. (In Russian) Krylov, G.V. 1962. Lesnye resursy i lesorastitel ’noe raionirovanie Sibiri i Dal’nego Vostoka [Forest resources and forest regions in Siberia and the Far East]. 240 pp„ Izd. Sib. Old. AN SSSR, Novosibirsk, Russia. (In Russian) Krylov, G.V. & Krylov, A.G. 1969. Lesa Zapadnoi Sibiri. In: Lesa SSSR [Forests of West Siberia. In: Forests of the Soviet Union], 4:157-247, Izd. "Nauka", Moscow, Russia. (In Russian) Kryuchkov, V.V. 1973. Krainii Sever: problemy racional ’nogo ispol ’zovaniya prirodnykh resursov [The Far North: problems of the rational use of natural resources], 184 pp„ Izd. "Mysl’", Moscow, Russia. (In Russian) Kryuchkov, V.V. 1987. Sever na grani tysyachiletii [The North at the boundary between Millenia], 268 pp., Moscow, Russia. (In Russian) Kudelya, V.A. 1988. Listvennichnye drevostoi Centralnoi Yakutii (stroenie, tovamost ’, osobennosti taksacii) [Larchstands of the central Yakutiya (structure, yield and other inventory data)]. 220 pp., Krasnoyarsk, Russia. (In Russian)

112 Kuvaev, V.B. 1971. Listvennitsa na yuge gor Putorana [Larchon southern slopes of the Putoran Mountains]. Lesovedenie, 5:37-45. (In Russian with English summary) Kuvaev, V.B. 1975. Rastitel’nost ’ basseina oz. Nyakshingda i ee vysotnoe raspredelenie. In: Putoranskaya ozemaya provinciya [Vegetation of the Nyakshingda Lake basin and its altitudinal distribution. In: The Putoran Lake Province]. 160-186, Izd. "Nauka", Novosibirsk, Russia. (In Russian) Kuvaev, V.B. 1980. Vysotnoe respredelenie rastenii v gorakh Putorana [Altitudinal distribution of plant species in the Putoran Mountains]. 264 pp., Izd. "Nauka", Lenin ­ grad, Russia. (In Russian) Kuznetsov, N.I. 1912. Opyt deleniya Sibiri na botaniko-geograficheskie provincii [The expertise in distinguishing geobotanical provinces in Siberia]. Izv. Akad. Nauk, Series IV, 14:871-897. (In Russian) Kuz’mina, N.A. & Cherepnin, V.L. 1973. Geograficheskaya izmenchivost’ vesa semyan listvennitsy sibirskoi v Srednei Sibiri [Geographical variability in seed weight of Siberian larch species in the central part of Sibiria]. Lesovedenie, 3:35-39. (in Russian with English summary) Lagov, LA. & Gavrilov, V.V. 1969. Geograficheskie posevy listvennitsy v Zailiiskom Alatau. In: Lesnaya selekciya, semenovodstvo i introdukciya v Kazakhstane [Provenance larch trials in the Zailiisky Alatau. In: Forest selection, seed manage ­ ment and introduction of tree species in Khazakhstan]. 50-54,Alma-Ata, Kazakhstan. (In Russian) Larionova, A.Ya. & Milyutin, L.I. 1981. Issledovanie vnuhividovoi differenciacii sibirskoi listvennitsy s pomoshchyu metoda izoenzimnykh spektrov [Investigations of intrapopulation variability of Larix sibirica by means of izoenzyme spectra]. Leso ­ vedenie, 2:3-11. (In Russian with English summary) Lashchinsky, N.N. 1958. Vozobnovlenie listvennitsy sibirskoi v gomykh lesakh Altaya [Regeneration of Larix sibirica in forests of the Altai Mountains]. Trudy po Lesn. Khoz. Sibiri, 4:461-478, Novosibirsk, Russia. (In Russian) Lashchinsky, N.N. 1960. Estestvennoe vozobnovlenie listvennitsy sibirskoi v glavneishikh dpakh lesa Gomogo Altaya [Natural regeneration of Larix sibirica in main forest types of the Altai Mountains]. PhD Thesis, 270 pp., Novosibirsk, Russia. (In Russian) Latysh, V.G., Deryuzhkin, R.I., Kolesnikova, R.D. & Krasnoboyarova, L.V. 1975. Sposob khemotaksonomicheskoi diagnostiki vida listvennitsy [Chemo-taxonomic method of larch species diagnostics]. Avt Svid. No 457922 (SSSR). Byul. Izobret., 3. (In Russian) Latysh, V.G., Deryuzhkin, R.I., Kolesnikova, R.D., Krasnoboyarova, L.V. & Chemo- dubov, A. 1979. Chemosystematism of the larch and pine in connection with composition and properties of essential oils. Proc. VII InL Congr. on Essential Oils, 1:194-197, Kyoto, Japan Leibundgut, H. 1961. Untersuchungen fiber europaische Larchen verschedener Herkunft. Schweiz. Zeitsch. ffir Forstwesen, 110,5: Linneus, C. 1754. Carl Linnei tankar om nyttiga vaxters planterade pa de Lappska Fj alien [Thoughts of Carl Linneus on useful plants grown on the mountains of Lappland], Kungl. Vet Akad. Handlingar, 15:182-189. (In Swedish) Malyshev, L.I. (Ed.) 1976. Flora Putorana [Flora of the Putoran Mountains], 243 pp., Izd. "Nauka", Novosibirsk, Russia. (In Russian)

113 Mamaev, S.A. 1969. O problemakh i metodakh vnutrividovoi sistematiki drevesnykh rastenii. II. Amplituda izmenchivosti [Intraspecific systematics of woody plants: problems and methods. Part 2: The amplitude of variability]. Trudy Inst. Ekol. Rast. i Zhiv. Ural Filial AN SSSR, 64:3-38, Sverdlovsk, Russia. (In Russian) Mamaev, S.A. 1972. Formy vnutrividovoi izmenchivosti drevesnykh rastenii [Forms of intraspecific variability of woody plants], 283 pp., Izd. "Nauka", Moscow, Russia. (In Russian) Martinsson, O. 1995. Yield of Larix sukaczewii Dyl. in northern Sweden. Stud. For. Suec., 195, 20 pp. Matveev, A.V. 1995. Ekologo-geneticheskayaizmenchivost ’ listvennitsy sibirskoi (Larix sibirica Ledeb.) na sevemom predele areala [Ecological and genetical variability of Larix sibirica Ledeb. at the northern border-line of its natural range of distribution], PhD Thesis, 16 pp., Ekaterinburg, Russia. (In Russian) Matveev, P.M. & Abaimov, A.P. 1980. K otsenke roll ognya v listvennichnykh drevo- stoyakh na merzlotnykh pochvakh. In: Lesnye pozhary i ikh posledstviya [An assess­ ment of the wild fire effect on larch forests occurring in the permafrost zone. In: Forest fires and their effects], 123-129, Krasnoyarsk, Russia. (In Russian) Matveeva, R.N., Butorova, O F. & Ovchinnikov, F.M. 1986. Ob otsenke kachestva lesnykh kul’tur Vostochnoi Sibiri. In: Ekologicheskaya rol ’ gomykh lesov [An asses- ment of the quality of larch commercial plantations in East Siberia. In: Ecological role of mountain forests]. Tez. Dokl. Konf., 138-140, Inst. Lesa i Drev. Sib. Otd. AN SSSR, Babushkin, Russia. (In Russian) Mayr, H. 1906. Fremlandische Wald- und Parkbaume in Europa. 662 pp., Berlin, Germany Medvedeva, N.S. 1971. Plodonoshenie listvennitsy daurskoi na severe Yakutii. In: Issledovaniya rastitel’nosti i pochv v lesakh Severo-Vostoka SSSR [Seed crop in Larix dahurica from the northern part of Yakutiya. In: Studies on vegetation and soils in forests of the nort-eastem part of the Soviet Union]. 69-75, Yakutsk, Russia. (In Russian) Middendorf, A. 1867. Puteshestvie na sever i vostok Sibiri. Chast’ 1. Sever i vostok Sibiri v estestvennoistoricheskom otnoshenii [A study trip to the northern and eastern parts of Siberia. Part 1. The North and the East of Siberia: natural and historical aspects]. 756 pp., St Petersburg, Russia. (In Russian) Mikhailenko, M.A. & Deryuzhkin, P.I. 1970. Razvitie i stroenie pokrovnykh tkanei u listvennitsy. In: Voprosy anatomo-morfologicheskikh i ekologo-fiziologicheskikh osobennostei stroeniya rastenii [The development and structure of the surface tissue in larch. In: Plant structure features in terms of anatomy, morphology, ecology, and physiology]. Izv. Voronezh Gos. Ped. Inst, 112:36-45, Voronezh. (In Russian) Milyutin, L.I. 1967. Nekotorye rezul’taty geograficheskikh posevov khvoinykh porod v Zabaikal’e. In: Geograficheskie aspekty gomogo lesovedeniya i lesovodstva [Some results from provenance trials of conifers in the Zabaikal’e region. In: Geographical aspects of mountain forestry], 119-122, Chita, Russia. (In Russian) Milyutin, L.I. 1971. Ob izmenchivosti morfologicheskikh priznakov listvennits Zabaikal’ya. In: Geograficheskie aspekty gomogo lesovedeniya i lesovodstva [On variability and morphological features of larch in the Zabaikal’e region. In: Geo ­ graphical aspects of mountain forestry], 1:87-90, Chita, Russia. (In Russian)

114 Milyutin, L.I. 1974. Introgressivnaya gibridizaciya listvennits sibirskoi i daurskoi i struktura populyacii. In: Teoreticheskie osnovy vnutrividovoi izmenchivosti i straktura populyacii khvoinykh porod [Natural hybridisation of Larix sibirica and Larix dahurica and the structure of populations. In: The fundamentals of intraspecific variability and structure of population in conifers]. 102-107, Sverdlovsk, Russia. (In (i Russian) Milyutin, L.I. 1980. V.N. Sukachev - issledovatel ’ listvennits Sibiri. In: Problemy lesnoi biogeocenologii [Studies on Siberian larch species carried out by V.N. Sukachev. In: Problems of forest biogeocenology]. 72-82, Izd. "Nauka", Novosibirsk, Russia. (In Russian) Milyutin, L.I. 1983. Vzaimootnosheniya i izmenchivost’ blizkikh vidov drevesnykh rastenii v zonakh kontakta ikh arealov (na primere listvennits sibirskoi i daurskoi) [Interrelations and variabiliy of allied species of woody plants in the contact zone of their natural range of distribution (on example of Larix sibirica and L dahurica)]. I PhD Thesis, 418 pp., Krasnoyarsk, Russia. (In Russian) Milyutin, L.I. 1984. Semenonoshenie i kachestvo semyan listvennitsy v Zabaikal’e. In: Ekologiya semennogo razmnozheniya khvoinykh Sibiri [Seed crop and seed quality in larch from Zabaikal’e. In: Ecology of seed reproduction of conifers in Siberia]. 88- ::-A 95, Inst Lesa i Drev. Sib. Otd. AN SSSR, Krasnoyarsk, Russia. (In Russian) Milyutin, L.I. 1995. Provenance trials of larch in Siberia. Proc. IUFRO S2-02-07 Work ­ shop: Larch genetics and breeding (Ed. O. Mardnsson). Swedish Univ. Agri. Sci„ Dept of Silviculture, Reports, 39:5-9, July 31 - Aug. 4, 1995, Umea, Sweden Milyutin, L.I. & Kutafev, V.P. 1967. O granitse mezhdu arealami listvennits sibirskoi i daurskoi [On boundary between natural range of distribution of Larix sibirica and L. dahurica], Izv. Sib. Otd. AN SSSR, series Biol-Med. Nauk., 10,2:91-97. (In Russian) Milyutin, L.I., Muratova, E.N. & Larionova, A. Ya. 1993. Genedko-taksonomicheskii analiz populacii listvennits sibirskoi i Sukacheva [Genedcal and taxonomic analysis of natural populations of Larix sibirica and L sukaczewii], Lesovedenie, 5:55-63. (In t i Russian with English summary) ■i Milyutin, L.I., Suntsov, A.V. & Zhamyansuren, S. 1988. Genetiko-selekcionnye osoben- nosti osnovnykh lesoobrazuyushchikh porod Vostochnogo Khanteya. In: Lesa Mongol ’skoi Narodnoi Respubliki. Listvennichnye lesa Vostochnogo Khanteya [Genetic and selection related features of main forest tree species of the Eastern Khantai. In: Forests of the Mongolia People ’s Republic. Larch forests of the Eastern 1 Khantai], 75-120, Izd. "Nauka", Moscow, Russia. (In Russian) 1 Milyutin, L.I. & Vishnevetskaya, K.D. 1995. Larch and larch forests of Siberia. Proc. Int. Conf.: Ecology and Management of Larix Forests: A Look Ahead, 50-53, Ogden, USA Mironenko, O.N. 1970. Rastitel’nost ’ basseina verkhnego techeniya r. Komi (Severnaya Evenkiya) [Vegetation of the Komi River head waters basin (the northern part of Evenkiya)]. PhD Thesis, 31 pp., Krasnoyarsk, Russia. (In Russian) Mironenko, O.N. 1975. Rastitel’nost ’ yugo-vostochnogo sektora gor Putorana. In: Puto- ranskaya ozemaya provinciya [Vegetation of the south-eastern part of the Putoran Mountains. In: The Putoran Lake Province], 141-159, Izd. "Nauka", Novosibirsk, Russia. (In Russian)

115 ;{ 3

mm 4- % -V- .-vm Muratova, E.N. 1991. Dobavochnye khromosomy u listvennitsy Gmelina Larix gmelinii (Rupr.) Rupr. [Additional chromosomes in Larix gmelinii (Rupr.) Rupr.]. Dokl. AN SSSR, 318,6:1511-1514. (In Russian) Muratova, E.N. 1995. Kariosistematika semeistva Pinaceae Lindl. Sibiri i Dal’nego Vostoka [Karyosystematics of the family Pinaceae Lindl. from Siberia and the Far East]. PhD Thesis, 32 pp., Novosibirsk, Russia. (In Russian) Nadezhdin, V.V. 1971. Vliyanie geograficheskogo proiskhozhdeniya semyan listvennitsy na ee rost [The effect of geographical origin of seeds on growth rate in larch]. 129 pp., Izd. "Nauka", Moscow, Russia. (In Russian) Nazimova, D.I. & Polikarpov, N.P. 1996. Forest zones of Siberia as determined by climatic zones and their possible transformation trends under global change. Silva Fennica, 30(2-3):201-208 Nedrigailov, S.N. 1932. Lesnoi pokrov i lesnye resursy severo-zapadnogo kraya YaASSR. In: Lesnye resursy Yakutii [The forest cover and forest resources of Yakudya. In: The forest resources of Yakutiya]. 3:121-124, Moscow, Russia. (In Russian) Norin, B.N. 1958. K poznaniyu semennogo i vegetativnogo vozobnovleniya drevesnykh porod v lesotundre. In: Rastitel’nost ’ Krainego Severn i ee osvoenie [Contribution to the knowledge of seed and sprout regeneration of woody plants in the forest-tundra zone. In: Vegetation of the Far North and its management], 3:154-244, Izd. AN SSSR, Moscow - Leningrad, Russia. (In Russian) Norin, B.N. et al. 1986. Gomye fitocenoticheskie sistemy Subarktiki [Montane phyto- cenotic systems of the sub-arctic zone]. 292 pp., Izd. "Nauka", Leningrad, Russia. (In Russian) Ogievsky, V.D. 1916. K voprosu o proiskhozhdenii semyan [About the origin of seeds], 207-226, Petrograd, Russia. (In Russian) Ogievsky, V.V. 1962. Iskustvennoe lesorazvedenie v Sibiri [The artificial reforestation in Siberia]. 175 pp., "Goslesbumizdat", Moscow, Russia. (In Russia) Ogievsky, V.V. & Medvedeva, A.A. 1977. Osobennosti rosta kul’tur listvennitsy sibirskoi v razlichnykh lesorastitel ’nykh raionakh Sibiri. In: Listvennitsa [Growth rate of larch cultures established in different growing conditions of Siberia. In: Larch], 8:18-23, Sib. Techn. Inst, Krasnoyarsk, Russia. (In Russian) Ostenfeld, C.H. & Larsen, C.S. 1930. The species of genus Larix and their geographical distribution. Danske Videnskab. Selskab, Biol. Meddelser, 9,2:1-107 Panarin, I.I. 1965. Tipy listvennichnykh lesov Chitinskoi oblasti [Larch forest types of the Chita Province]. 104 pp., Izd. "Nauka", Moscow, Russia. (In Russian) Panarin, LI. 1977. Lesa Chidnskogo Zabaikal'ya [Forests of Zabaikal’e], 232 pp., Izd. "Nauka", Novosibirsk, Russia. (In Russian) Panarin, I.I., Mitrofanov, D.P. & Isaeva, L.N. 1980. Gomye lesa zony BAM [Montane forests of the Baikal-Amur railway zone]. 223 pp., Izd. "Nauka", Novosibirsk, Russia. (In Russian) Parmuzin, Yu.P. 1962. Srednesibirskaya strana. In: Krasnoyarsk!) krai [The middle Siberia country. In: The Krasnoyarsk Territory], 138-244, Krasn. Krai. Gos. Izd., Krasnoyarsk, Russia. (In Russian) Patschke, W. 1913. Uber die extratropischen Coniferen und ihre Bedeutung fur die pflanzengeographische Gliederung Ostasiens. Bot. Jahrbuch fur Systematic und Pflanzengeographie, 158:651-655, H.V., Leipzig, Germany

116 Petrov, S.A. 1959. Khod rosta listvennitsy sibirskoi v usloviyakh yuzhnogo Altaya [Growth rate of Larix sibirica grown in the southern part of the Altai Mountains]. Lesn. Khoz., 12:16-17. (In Russian) Pilger, R. 1926. Gymnospermae. Die natiirlichen Pflanzenfamilien, 2,13:1-147, Leipzig, Germany Polozova, T.G. 1961. O samykh sevemykh mestonakhozhdeniyakh listvennitsy (Larix dahurica Turcz.) i kustamoi ol ’khi (Alnaster fruticosa Ledeb.) v nizov ’yakh reki Leny. In: Materialy po rastitel’nosti Yakutii [The northernmost site of Larix dahurica Turcz. and Alnaster fruticosa Ledeb. in the downstream Lena River lowland. In: Materials on vegetation of Yakutiya]. 291-294, Leningrad, Russia. (In Russian) Popov, L.V. 1982. Yuzhnotaezhnye lesa Srednei Sibiri [Southern taiga forests of the central part of Siberia]. 330 pp., Izd. Irkutsk Univ., Irkutsk, Russia. (In Russian) Popov, V.V. & Tikhomirov, B.N. 1940. Listvennichnye lesa basseina rek Many i Kana v Vostochnykh Sayanakh. In: Listvennitsa sibirskaya [Larch forests in the Mana and Kan Rivers basin in the eastern Sayan Mountains. In: Siberian larch]. 3-37, Sib. Techn. Inst, Krasnoyarsk, Russia. (In Russian) Povamitsyn, V.A. 1937. Pochvy i rastitel’nost ’ r. V. Angary [Soils and vegetation at the Angara River head waters]. Trudy Sov. po Izuch. Proizv. Sil AN SSSR, series Vost- Sib., 4:7-137, Moscow, Russia. (In Russian) Povamitsyn, V.A. 1949. Lesa daurskoi listvennitsy SSSR [Larix dahurica forests of the Soviet Union], Byul. MOIP, Old. Biol., 54,3:53-67. (In Russian) Pozdnyakov, L.K. 1961 a. Listvennichnye i sosnovye lesa verkhnego Aldana [Larchand pine forests of the Aldan River head waters basin]. 175 pp., Izd. AN SSSR, Moscow, Russia. (In Russian) Pozdnyakov, L.K. 1961 b. Plodonoshenie i posevnye kachestva semyan daurskoi list­ vennitsy. In: Listvennitsa i ee ispol ’zovanie v narodnom khozyaistve [Seed crop and seed quality of Larix dahurica. In: Larch and its use in national economy]. CB71 Lesn. PromyshL, 51-57, Moscow, Russia. (In Russian) Pozdnyakov, L.K. 1962. Biologiya plodonosheniya daurskoi listvennitsy v Central’noi Yakutii [Biology of fructification of Larix dahurica in the central part of Yakutiya], Bot 22ium., 47.7:1000-1006. (In Russian) Pozdnyakov, L.K. 1963. Gidroklimaticheskii rezhim listvennichnykh lesov Central ’noi Yakutii [Hydroclimatic regime in forests of the central part of Yakutiya]. 146 pp., Izd. AN SSSR, Moscow, Russia. (In Russian) Pozdnyakov, L.K. 1968. Posevnye kachestva semyan vostochnoi rasy daurskoi list­ vennitsy. In: Listvennitsa [Seed quality of the eastern race of Larix dahurica. In: Larch]. 3:139-151, Sib. Techn. Inst., Krasnoyarsk, Russia. (In Russian) Pozdnyakov, L.K. 1975. Daurskaya listvennitsa [Larix dahurica]. 310 pp., Izd. "Nauka", Moscow, Russia. (In Russian) Pozdnyakov, L.K. 1980. Stroenie peregushchennykh listvennichnykh molodnyakov v Yakutii [Structure of dense larch thickets in Yakutiya]. Lesovedenie, 4:46-55. (In Russian with English summary) Pozdnyakov, L.K. 1983. Les na vechnoi merzlote [Forests of the permafrost zone]. 96 pp., Izd. "Nauka", Novosibirsk, Russia. (In Russian) Pozdnyakov, L.K. 1986. Merzlotnoe lesovedenie [The permafrost forestry], 130 pp., Izd. "Nauka", Novosibirsk, Russia. (In Russian)

117 Pravdin, L.F. 1975. El’ evropeiskaya i el’ sibirskaya v SSSR [Picea abies and P. obovata in the Soviet Union], 177 pp., Izd. "Nauka", Moscow, Russia. (In Russian) Prokazin, E.P., Kurakin, B.N., Iroshnikov, A.I., Krechetova, N.V., Shutyaev, A.M., et al. 1982. Lesosemennoe raionirovanie osnovnykh lesoobrazuyushchikh porod v SSSR [Regionalisation of seed sources of the main tree species occurring in forests of the Soviet Union]. 368 pp., Izd. "Lesn. Promyshl.", Moscow, Russia. (In Russian) Pugach, E.A. 1968. O novoi forme listvennitsy Sukacheva. In: Listvennitsa [About a new form of Larix sukaczewii. In: Larch], 3:89-100, Sib. Techn. Inst., Krasnoyarsk, Russia. (In Russian) Putenikhin, V.P. 1993. Listvennitsa Sukacheva na Yuzhnom Urale [Larix sukaczewii in the southern Urals (Variability, population structures, and gene pool preservation)]. 195 pp., Ufa Nauch. Centr RAN, Ufa, Russia. (In Russian) Putenikhin, V.P. & Martinsson, O. 1995. Present distribution of Larix sukaczewii. Swedish Univ. Agri. Sci., Dept, of Silviculture, Reports, 38:1-78, Umea, Sweden Razumova, V.A. 1965. Obshchie zakonomemosti raspiedeleniya rastitel’nosti v verkhnei chasti basseina Nizhnei Tunguski (Katangskii raion Irkutskoi oblasti) [General vegetation distribution patterns at the head waters of the Nizhnaya Tunguska], Dokl. Inst Geogr. Sib. i Daln. Vost, 8:48-57, Irkutsk, Russia. (In Russian) Rechan, S.P. & Kiylov, A.G. 1965. Lesorastitel ’noe raionirovanie i tipy lesa. In: Lesa Gomogo Altaya [Forest regions and forest types. In: Forests of the Altai Mountains]. 22-143, Izd. "Nauka", Moscow, Russia. (In Russian) Regel, E. 1871. Revisio Speciorum Generis Laricis. Trudy St.-Petersburg Bot. Garden, 1,1,4:155-161 Ruprecht, F.I. 1845. Flores samojedorum cis-uralensium. Beitr. zur Pflanzenkunde das Russ Reiches, 2:1-67 Salin’sh, S. Kh. 1968. Opyt razvedeniya listvennitsy v Latviiskoi SSR. In: Listvennitsa [Expertise in larch commercial plantations in the Latvian Republic. In: Larch], 3:201- 201, Sib. Techn. Inst, Krasnoyarsk, Russia. (In Russian) Samofal, S. 1929. K izucheniyu klimaticheskikh ras sibirskoi listvennitsy [Studies on climatic races of Siberian larch]. Trudy po Lesn. Opyt Delu, 75,1:95-115. Leningrad, Russia. (In Russian) Savin, E.N. Semechkin, I.V. & Dugarzhav, Ch. 1978. Osnovnye lesoobrazuyushchie porody. In: Lesa Mongol ’skoi Narodnoi Respubliki. Geografiya i tipologiya [Main forest tree species. In: Forests of the Mongolia People ’s Republic. Geography and typology]. 22-35, Izd. "Nauka", Moscow, Russia. (In Russian) Schulze, E-D., Schulze, W„ Kelliher,F.M., Vygodskaya, N.N., Ziegler, W„ Kobak, K.I., Koch, H„ Ameth, A., Kuznetsova, V.A., Sogachev, A., Issaev, A., Bauer, G. & Hollinger, D.Y. 1995. Above-ground biomass and nitrogen nutrition in a chrono- sequence of pristine Dahurian Larch stands in eastern Siberia. Can. J. For. Res., 25,6: 943-960 Semerikov, V.L. & Matveev, A.V. 1995. Izuchenie geneticzeskoi izmenchivosti list­ vennitsy sibirskoi (Larix sibirica Ledeb.) po izofermentnym lokusam [Studies on genetic variability in Larix sibirica Ledeb. with respect to izoenzymatic loci]. Genetika, 31,8:1107-1113. (In Russian) Shanin, S.S. 1965. Stroenie sosnovykh i listvennichnykh drevostoev Sibiri [The structure of pine and larch stands in Siberia]. 105 pp., Izd. "Lesn. Promyshl.", Moscow, Russia. (In Russian)

118 Shcherbakov, I.P. 1975. Lesnoi pokrov Severe-Vostoka SSSR [The forest cover of the north-eastern part of the Soviet Union], 344 pp., Izd. "Nauka", Novosibirsk, Russia. (In Russian) Shcherbakov, I.P. 1992. Lesa verkhnego i srednego techeniya reki Vilyui. In: Botanicheskie issledovaniya v kriolitozone [Forests in the upper and middle parts of the Vilyui River basin. In: Botanical investigations in the permafrost zone]. 91-104, Yakutsk, Russia. (In Russian) Shcherbakov, I.P., Zabelin, O.F., Karpel’, B.A. et al. 1979. Lesnye pozhary v Yakutii i ikh vliyanie na prirodu lesa [Forest fires in Yakutiya and their effects on forest life]. 226 pp., Izd. "Nauka", Novosibirsk, Russia. (In Russian) Shcherbatyuk, A.S. 1969. Plodonoshenie listvennitsy sibirskoi v travyanykh listven- nichnikakh verkhnei Leny [Seed crop in Larix sibirica in grassy type larch forests of the Lena River head waters]. Izv. VosL Sib. Otd. Geogr. Obshch. SSSR, 66:132- 137, Irkutsk, Russia. (In Russian) Shevelev, E.I. 1975. Vyrashchivanie seyantsev listvennitsy daurskoi na yuge Magadan- skoi oblasti [Growing seedlings of Larix dahurica in the southern part of the Magadan Province]. PhD Thesis, 21 pp., Ural Techn. Inst., Sverdlovsk, Russia. (In Russian) Shiyatov, S.G. 1967. Kolebaniya klimata i vozrastnaya struktura drevostoev list- vennichnykh redkolesii v gorakh Polyamogo Urala. In: Rastitel’nost ’ lesotundry i puti ee osvoeniya [Climatic fluctuations and age structure of open larch forests in the montane forest-tundra zone of the northern Urals. In: Vegetation of the forest-tundra zone and perspectives of its utilisation]. 271-278, Izd. "Nauka", Leningrad, Russia. (In Russian) Shurduic, I.F. 1979. Stroenie, rest i tovamost ’ drevostoev listvennitsy v Yuzhnoi Sibiri [Structure, growth rate and yield of larch stands of the southern part of Siberia], PhD Thesis, 21 pp., Krasnoyarsk, Russia. (In Russian) Simak, M. 1964. Karyotype analysis of Siberian larch {Larix sibirica Ledeb. and Larix sukaczewii Dyl.). Stud. For. Suec., 17, 15 pp. Skripachenko, G.A. 1985. IspoTzovanie metodov genosistematiki dlya issledovaniya listvennits Sibiri [Use of the methods of genosystematics for studies of the Siberian larch species]. PhD Thesis, 17 pp., Inst. Lesa i Drev. Sib. Otd. AN SSSR, Krasno ­ yarsk, Russia. (In Russian) Skripachenko, G.A. & Milyutin, L.1.1977. Nukleotidnyi sostav DNK razlichnykh vidov listvennits. In: Operadvnye informacionnye materialy Sibirskogo instituta fiziologii i biokhimii rastenii [Nucleotic composition of DNA in various larch species. In: The data base of the Siberian Institute of Physiology and Biochemistry of Plants]. 32-33, Irkutsk, Russia. (In Russian) Skripachenko, G.A. & Milyutin, L.I. 1982. Ispol ’zovanie metodov genosistematiki v issledovaniyakh roda Larix Mill. In: Khemosistematika i evolyucionnaya biokhimiya rastenii (tezisy dokladov) [Use of the methods of genosystematics in studies of the genus Larix Mill. In: Chemosystematics and evolutionary biochemistry of plants (abstracts)]. 92-94, Moscow, Russia. (In Russian) Smagin, V.N. 1965. Lesa basseina r. Ussuri [Forests of the Ussuri River basin], 271 pp., Izd. "Nauka", Moscow, Russia. (In Russian) Smagin, V.N., Nazimova, D.I. Cherednikova, Yu.S. et al. 1980. Tipy lesov gor Yuzhnoi Sibiri [Forest types in the mountains of the southern part of Siberia]. 334 pp., Izd.

119 "Nauka", Novosibirsk, Russia. (In Russian) Sochava, V.B. 1956. Listvennichnye lesa. In: Rastitel’nyi pokrov SSSR [Larch forests. In: Vegetation of the Soviet Union. Explanatory text to the Geobotanical Map of the Soviet Union]. 1:249-318, Izd. AN SSSR, Moscow - Leningrad, Russia. (In Russian) Sokolov, S.Ya., Svyazeva, O.A. & Kublin, V.A. 1977. Arealy derev ’ev i kustamikov SSSR [Ranges of natural distribution of tree and shrub species in the Soviet Union], 1:1-162, Izd. "Nauka", Leningrad, Russia. (In Russian) Sokolov, V.A. et al 1994. Struktura i dinamika taezhnykh lesov [Structure and dynamics of taiga forests]. 168 pp., Izd. "Nauka", Novosibirsk, Russia. (In Russian) Sominsky, V.S. & Mel’nichenko, E.D. 1985. Problems of using larch wood in the pulp and paper industry. Bum. Promyshl., 10:7-8 Stairs, G.R. 1968. Monoterpene composition in Larix. Silvae Genetica, 17,5-6:182-186 Starikov, G.F. 1958. Lesa Magadanskoi oblasti [Forests of the Magadan Province]. 223 pp., Magadan, Russia. (In Russian) Stepanov, G.M. 1988. Temperatumyi rezhim merzlotnykh pochv na garyakh sevemoi Yakutii [Temperature regime of forest soils on burned areas of the permafrost zone in northern Yakutia], Lesovedenie, 5:67-71. (In Russian with English summary) Sudachkova, N.E., Rastorgueva, E.Ya. & Kolovsky, P.A. 1967. Fiziologiya podrosta kedra [Physiology of the advance growth of Pinus sibirica Ledeb.]. 122 pp., Izd. "Nauka", Moscow, Russia. (In Russian) Sukachev, V.N. 1924. K istorii razvitiya listvennits. In: Lesnoe delo [About the history of the genus Larix Mill. In: The forest issues], 12-44, Izd. "Novaya Derevnya", Moscow - Leningrad, Russia. (In Russian) Sukachev, V.N. 1934. Dendrologiya s osnovami lesnoi geobotaniki [Dendrology with basic knowledge on forest geobotany]. 614 pp., "Goslestekhizdat", Leningrad, Russia. (In Russian) Sukachev, V.N. 1938. Dendrologia (Dendrology]. 574 pp., 2nd Ed. "Goslestekhizdat", Leningrad, Russia. (In Russian) Sukachev, V.N. & Dylis, N.V. (Eds.) 1964. Osnovy lesnoi biogeocenologii [The fundamentals of forest biogeocenology]. 364 pp. Izd. "Nauka", Moscow, Russia. (In Russian) Sukachev, V.N. & Poplavskaya, G.I. 1914. Botanicheskoe issledovanie sevemogo poberezh’ya Baikala v 1914 g. [Botanical investigations in the northern part of the Baikal Lake basin carried out in 1914]. Izv. AN, series V, 8,17:1309-1328. (In Russian) Szafer, W. 1913. Przyczynek do znajomoSci modrzewi euroazjatyckich ze szczegdlnym uwzglgdnieniem modrzewia w Polsce [Contribution to the knowledge of Eurasian larch species with particular attention paid to larch species occurring in Poland], Kosmos, 38,1012:1281-1315, Cracow, Poland. (In Polish) Tachtajan, A. 1974. The chemical approach to plant classification with special reference to the higher taxa of Magnoliophyta. In: Chemistry in Botanical Classification. 17-26, Acad. Press, Stockholm - New York - London Tang Qian, Ennos, R.A. & Helgason, T. 1995. Genetic relationships among larch species based on analysis of restriction fragment variation for chloroplast DNA. Can. J. For. Res., 25,7:1197-1202 Tarabukina, V.G., & Sawinov, D.D. 1990. Vliyanie pozharov na merzlotnye pochvy [Fire effect on permafrost soils], 120 pp., Izd. "Nauka", Novosibirsk, Russia. (In

120 Russian) Taran, I.V. 1969. Listvennitsa v Novosibirskoi oblasti. In: Pud i metody obogashcheniya dendroflory Sibiri i Dal’nego Vostoka [Larch in the Novosibirsk Province. In: How to enrich the Siberian and Far East dendroflora], 142-145, Izd. "Nauka", Novosibirsk, Russia. (In Russian) Tikhomirov, B.N., Koropachinsky, I.Yu. & Falaleev, E.N. 1961. Listvennichnye lesa Sibiri i Dal’nego Vostoka [Larch forests of Siberia and the Far East]. "Goslesbum- izdat", Moscow - Leningrad, Russia, (in Russian) Tikhomirov, B.N., Tishchenkov, I.A. 1929. Khod rosta sibirskoi listvennitsy po issledo- vaniyam v Khakasskom okruge Sibirskogo kraya [Growth rates of Larix sibirica in Khakasiya], Trudy po Lesn. OpyL Delu, 12,1-3:87-167, Omsk, Russia. (In Russian) Timofeev, V.P. 1947. Listvennitsa v kuVture [Larch commercial plantations]. 295 pp„ "Goslesbumizdat", Moscow - Leningrad, Russia, (in Russian) Timofeev, V.P. 1961. Rol ’ listvennitsy v podnyati produktivnosti lesov [The role of larch in increasing productivity of forests], 159 pp„ Izd. AN SSSR, Moscow, Russia. (In Russian) Timofeev, V.P. 1977. Lesnye kul’tury listvennitsy [Larch commercial plantations]. 215 pp., Izd. "Lesn. Promyshl.", Moscow, Russia. (In Russian) Timofeev, V.P. & Dylis, N.V. 1953. Lesovodstvo [Silviculture], 552 pp., "Sel’khozgiz", Moscow, Russia. (In Russian) Tolmachev, A.I. 1931. O rasprostranenii drevesnykh porod po sevemoi granitse lesov v oblasti mezhdu Yeniseem i Khatangoi [The distribution of tree species at the timberline between the rivers of Yenisei and Khatanga], Trudy Polyar. Kom. AN SSSR, 5:1-29, Moscow, Russia. (In Russian) Tol ’sky, A.P. 1938. Analiz klimaticheskikh uslovii proizrastaniya sibirskoi listvennitsy [Analysis of growing conditions of larch forests in terms of climate]. Trudy po Sel’skokhoz. Meteorol., 25:138-174. Moscow - Leningrad, Russia, (in Russian) Tseplyaev, V.P. 1958. Sostoyanie i perspektivy rabot po razvedeniyu bystrorastushchikh i khozyaistvenno cennykh drevesnykh i kustamikovykh porod. In: Bystrorastushchie i khozyaistvenno cennye drevesnye porody [State and perspectives of growing the fast-growing and valuable tree species. In: Fast-growing and valuable tree species]. 9-22, Izd. Min. Sel. Khoz. SSSR, Moscow, Russia. (In Russian) Tyrtikov, A.P. 1974. Dinamika rastitel’nogo pokrova i razvitie vechnoi merzloty v Zapadnoi Sibiri [The dynamics of vegetation cover and the development of perma­ frost in West Siberia], 108 pp., Izd. Mosk. Gos. Univ., Moscow, Russia. (In Russian) Tyrtikov, A.P. 1979. Dinamika rastitel’nogo pokrova i razvitie merzlotnykh form rel’efa [The dynamics of vegetation cover and the development of permafrost relief forms]. 116 pp., Izd. "Nauka", Moscow, Russia. (In Russian) Tyrtikov, A.P. 1983. Redkostoinye lesa i redkoles ’ya severa Zapadnoi Sibiri. In: Ekologo-cenoticheskie i geograficheskie osobennosti rastitel’nosti [Open larch forests in the northern part of West Siberia. In: Ecocenotic and geographical features of vegetation]. 210-217, Izd. "Nauka", Moscow, Russia. (In Russian) Tyulina, L.N. 1937. Lesnaya rastitel’nost ’ Khatangskogo raiona u ee sevemogo predela [Forest vegetation in the northern part of the Khatanga region], Trudy Arkt Inst, 63:83-180, Leningrad, Russia. (In Russian) Tyulina, L.N. 1954. Listvennichnye lesa severo-vostochnogo poberezh’ya Baikala i zapadnogo sklona Barguzinskogo khrebeta [Larch forest of the north-eastern part of

121 the Baikal Lake basin and on western slopes of the Barguzin Range], Trudy Bot. Inst. AN SSSR, series Geobotanika, 9:150-209. (In Russian) Tyulina, L.N. 1957. Ocherk lesnoi rastitel’nosti verkhnego techeniya r. Aldana [Forest vegetation at the head waters of the Aldan River], Trudy Inst. Biol. Yakut. Fil. AN SSSR, 3:83-138, Yakutsk, Russia. (In Russian) Ukhanov, V.V. 1949. Larix Mill. - Listvennitsa. In: Derev’ya i kustamiki SSSR [Larix Mill. - Larch. In: Tree and shrub species of the Soviet Union]. 1:153-176, Izd. AN SSSR, Moscow - Leningrad, Russia. (In Russian) Utkin, A.I. 1958. Nekotorye osobennosd rasprostraneniya komevykh sistem drevesnykh porod v kholodnykh pochvakh [Some features of tree species’ root system distribution in cold soils], 64-71, Soobshch. Inst. Lesa AN SSSR, Moscow, Russia. (In Russian) Utkin, A.I. 1965. Lesa Central ’noi Yakutii [Forests of the central part of Yakutiya]. 208 pp., Izd. "Nauka", Moscow, Russia. (In Russian) Utkin, A.I. & Isaev, A.S. 1962. Nizovye pozhary v listvennichnykh lesakh Vostochnoi Sibiri i ikh vliyanie na sostoyanie drevostoev. In: Listvennitsa [Ground fires in larch forests of East Siberia and their effect on condition of stands. In: Larch], 60-69, Krasnoyarsk, Russia. (In Russian) Vaganov, E.A., Shiyatov, S.G. & Mazepa, V.S. 1996. Dendroklimaticheskie issledova- niya v Uralo-Sibirskoi Subarktike [Dendroclimatic investigations in the Ural-Siberian sub-arc tic zone]. 243 pp., Izd. "Nauka", Novosibirsk, Russia. (In Russian) Valendik, E.N. 1996. Ekologicheskie aspekty lesnykh pozharov v Sibiri [Ecological aspects of wild fires in Siberia]. Sib. Ekol. Zhum., 3,1:1-8. (In Russian) Varaksin, G.S. & Milyutin, L.I. 1996. Geograficheskie kul’tury listvennitsy v levo- berezh’e Yeniseya [Larch provenance trials in the area west of the Yenisei River]. Lesovedenie, 2:89-92. (In Russian with English summary) Veresin, M.M., Efimov, Yu.P. & Arefev, Yu.F. 1985. Spravochnik po lesnomu selekcionnomu semenovodstvu [Handbook on seed management for forest selection purposes]. 245 pp., "Agropromizdat", Moscow, Russia. (In Russian) Verkhovtsev, E.P. 1940. Razmer plodonosheniya i kachestvo semyan listvennitsy sibirskoi v redinakh. In: Listvennitsa sibirskaya [Seed crop and seed quality in Siberian larch from open stands. In: Siberian larch]. 89-96, Krasn. Krai. Gos. Izd., Krasnoyarsk, Russia. (In Russian) Vinogradova, A.N. 1937. Geobatanicheskii ocherk olenikh pastbishch raiona reki Pyasiny [Geobotanical description of raindeer pastures in the Pyasina River basin], Trudy Arkt. Inst, series Geobotanika, 63:5-45, Leningrad, Russia. (In Russian) Vodop ’yanova, N.S. 1975. Rastitel’nost ’ yugo-zapada gor Putorana. In: Putoranskaya ozemaya provinciya [Vegetation of the south-western part of the Putoran Mountains. In: The Putoran Lake Province]. 122-140, Izd. "Nauka", Novosibirsk, Russia. (In Russian) Vodop ’yanova, N.S. 1976. Rastitel’nost ’ Putorana. In: Flora Putorana [Vegetation of the Putoran Mountains. In: Flora of the Putoran Mountains]. 11-31, Izd. "Nauka", Novo ­ sibirsk, Russia. (In Russian) Voichal’, P.I. 1967. Kul’tury sosny, eli i listvennitsy iz vostochnosibirskikh semyan v Arkhangelskoi oblasti. In: Geograficheskie aspekty gomogo lesovedeniya i leso- vodstva [Pine, spruce and larch cultures in the Arkhangelsk Province established using seeds originating from the East Siberian sources. In: Geographical aspects of

122 mountain forestry]. 119-122, Chita, Russia. (In Russian) Vol ’sky, L.N. & Pentegova, V.A. 1968. Izuchenie sostava efimykh masel nekotorykh vidov khvoinykh Sibiri metodom gazozhidkostnoi khromatografii. Soobshchenie 2. Larix sibirica Ledeb., Larix dahurica Turcz., Larix x czekanowskii Szafer [Studies on terpen oils composition in some coniferous species of Siberia by means of gas chromatography. Report 2. Larix sibirica Ledeb., Larix dahurica Turcz., Larix x czekanowskii Szafer]. Izv. Sib. Otd. AN SSSR, series Khim. Nauk., 12,5:115-117. (In Russian) Vorob ’ev, G.I. et al. (Eds.). 1986. Lesnaya enciklopediya [Forest encyclopedia], II, 631 pp„ "Sov. encykl.", Moscow, Russia. (In Russian) Wentzel, A.K. 1996. Gammelgran med rotter i istiden [Old spruce with roots in the Ice Age]. Forskning & Framsteg, 8:50-51. (In Swedish) Yen-chu Wang. 1995. Physical ecology and regulation measurement for establishment of fast-growing and high-yield larch forests in Northeastern China. Proc. Int Conf.: Ecology and Management of Larix Forests: A Look Ahead, 79-80, Ogden, USA

123 djupets och planteringspunktens betydelse for 24. Pehap, A., Henriksson, G. & Sahlen, K.: planters etablering i ett omrSde medlSg humiditet Respiration ofgerminatingspruceseeds: Further isodra Sverige. (Effects of scarification, planting investigations and measurements with the depthandplantingspotonseedlingestablishment Warburg direct method. in alow humidity area in southern Sweden).

1989 1992 25. Jeansson, E., Bergman, F., Elfving, B., Falck, 34. Hdnell, B.: Skogsfomyelse pS hogproduktiva J. & Lundqvist, L.: Natural regeneration of pine torvmarker - plantering av gran p&kalhygge och and spruce. - Proposal for a research program. underskarmtrad. (Forest renewal on productive Faculty of Forestry. Swedish University of peatlands-.PlantingofNorwayspruceonclearcuts Agricultural Sciences. and inshelterwoods).

1990 35. Silvicultural alternatives. Proceedings from 26. Orlander, G., Hallsby, G. & Sundkvist, H.: an intemordic workshop June 22-251992. Editor: dverlevnadochtillvaxthostall(/ ’z/7itf jy/vetim) MatsHagner. och gran (Picea abies) samt naringsforhSllanden 23 Sr efter plantering pS helplojd resp brand 1993 tallhedsmark. 36. Andersson, B.: Lovtradens inverkan pi smi tallars (Pinus sylvestris) overlevnad, hOjd och 27. Gemmel, P. & Nilsson, U.: Competition dimeter. (The influence ofbroad-leaved trees on between originally planted and beeted seedlings survival, height and diameter of smallScotspine in stands of Norway spruce and Scots pine. (Pinus sylvestris L.) trees).

28. Lundqvist, L.: Biadningsytan i Gammels-torp - 1994 en demonstrationsyta skott med stamvis blad- 37. Valinger, E. & Lundqvist, L.: Reducing wind ning. (The selection plot in Gammelstorp - a and snow induces damage in forestry. permanent plot with single tree selection). 1995 29. Martinsson, O.: Den ryska larkens hojd- 38. Putenikhin, V.P. & Martinsson,O. Present utveckling och volymproduktion i norra Sverige. distribution of Larix sukaczewii Dyl. in Russia (Height growth andvolume production of Russ­ ian larch (Larix sukaczewii Dyl.) in northern 39. Larch genetics and breeding. Research findings Sweden). and ecological-silvicultural demands. Proceedings. IUFRO WORKING PARTY S2.02-07. July 30. Fries, C.: Utveckling hos bestSndsforyngrad 31 -August 4,1995. Remningstorp and Siljans- gran och kompletteringsplanterade granar och fors. tallar i ett karvt klimatlage. (Developement of advance growth of Norway spruce and 40. Petursson, J.G. Direct seeding of Sitka spruce supplementaryplanted spruce and Scotspine in (Picea sitchensis (Bong.) Carr.), lodgepole pine a harsch climate). (PinuscontortaDougl. v. contorta) and Siberian larch (Larix sibirica Ledeb.), on scarified seed 31. Sugg, A.: Seedling establishment results from a spots in southern Iceland, using various methods. site preparation study in southern Sweden: The first fouryears survival and growht of Scots pine 1996 (Pinussylvestris L.)andNorway spruce (Picea 41. Mehari, A. Establishing Fuelwood plantation abies (L.) Karst.) and Fire wood Tree Crop Performance on the Highlands of Ethiopia: The case of Eucalyptus 1991 globulus Labill.ssp. globulus 32. H5nelI,B.: Fomyelse av gransumpskog pi bor- digatorvmarkergenom naturlig foryngring under 1997 hdgskarm. (Shelterwoodregeneration of spruce 42. Albrektson, A., Valinger, E., Leijon, B., forests on productive peat lands). Sjogren, H. & Sonesson, J. Indications on 33. Orlander, G., Gemmel, P. & Wilhelmsson, continued nitrogen uptake in Scots pine roots C.: Markberedningsmetodens, planterings- afterclear-felling. DISTRIBUTION: Pris: 200:- Sveriges lanbruksuniversiet Institutionen for skogsskotsel 901 83 UMEA, Sweden Tel: 090-786 62 74 ISSN 0348-8969 Fax: 090-786 76 69 ISRN SLU-SSKTL-R--43-SE