A Spitsbergen : With Observations on the Ecological Phenomena Attendant on the Emergence of Land from the Author(s): John Walton Source: Journal of Ecology, Vol. 10, No. 1 (May, 1922), pp. 109-121 Published by: British Ecological Society Stable URL: http://www.jstor.org/stable/2255433 Accessed: 27-06-2016 09:30 UTC

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A SPITSBERGEN SALT MARSH: WITH OBSERVATIONS ON THE ECOLOGICAL PHENOMENA ATTENDANT ON THE EMERGENCE OF LAND FROM THE SEA1

BY JOHN WALTON, B.A. H'utchinson Research Student, St John's College, Cantab.

(With Plates VI, VII and six Figures in the Text.)

The area of land where these observations were made lies near the centre of the western portion of the of Spitsbergen in lat. 780 39' N., long. 160 45' E. at the head of Klaas Billen in the angle between it and its branch Adolf Bay (Fig. 1). Klaas Billen Bay opens into Ice , one of the large of the west of Spitsbergen.

PRINCE CHFARLES FORELANID

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THE GREENLAND SEA

< ICE FJORD ,.,-la1,1z8W"""' (CAPE NAPIER, T H S HORDsENC; DICKSSONLAND

SOUND AoOLF I

50 KILOMiETRES

FrG. 1. Map of Ice Fjord, West Spitsbergen.

The main object of these investigations was to obtain some data for a detailed comparison of an arctic salt marsh with a salt marsh in Britain (5). The plane table survey which was made will make it possible for a future observer to determine the rate at which the vegetation develops.

1 "Results of the Oxford University Expedition to Spitsbergen 1921," No. 8.

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Raised are a common feature in the topography of Spitsbergen and a great deal of the vegetation is found on this type of ground. It was therefore a matter of interest to trace the development of the vegetation from its initial stages at a place where the land was just emerging. The slope of the emerging land is slight, so that a small vertical rise exposes a large area for colonisation (P1. VI, Fig. 1). A line of boulders shelters the outer mud flats of the marsh from waves from the bay (Fig. 2). In addition the middle and inner mud flats on which the land flora is developing are sheltered by the shingle banks which leave the main bank at X, Y, Z (Fig. 2) and extend landwards across to the heavily silted area on the other side of the mud flats

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eCAPE NAPIRIE BA KLAPS BILLEN BAY

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M U D FLA.T S ."OO VEGETATION / /

FIG. 2. Diagram of the central portion of P1. VI, Fig. 1. The positions of Napier and Adolf Bay are marked in Fig. 1. The length of -line represented is about 1 kilometre.

(Fig. 2). To the N.E. about a kilometre distant from the marsh the Norden- skj old Glacier reaches Adolf Bay and the proximity to this large mass of ice and to the ice-covered interior beyond is an impgrtant factor in the tempera- ture relations of the area. The mountains on each side of the Bay are on an average about 2500 ft. high and cause the direction of the wind to be either from the south and the Atlantic or down off the cold interior of the Archipelago. The effect of this can be seen on plants such as Dryas octopetala (1) which grow on the exposed parts of the raised shingle beaches. The plants develop their branch system horizontally, spreading towards the south prostrate over the ground, and bearing leaves and flowers on the margin of the plant facing south. In some places the plants of Dryas form a system of parallel lines at right angles to the prevalent wind and give the appearance of waves (P1. VII,

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w L

FIG. i. View from Mt Campbell, taken hromna point 8oo ft. above sea-level. Above the centre Cape Scott and the raised shingle system; in the foreground banded sedimentary rocks; between the twvo the silted areas showinor the courses of the streams.

Photos by .7 W. FIG. 2. Pool between Pools V and VI, showing indications of colonisation by Eriophorum sckeuckzeri and Dufiontiaflskeriz In the background tussocks of Salix are evident.

WALTON-A SPITSBERGEN SALT MARSH.

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Fig. 3). The origin of this formation is probably due to the fact that seedlings are only able to establish themselves among the prostrate branches of an already established plant (Fig. 3). Plants which shelter one another at the sides in a continuous wave front will be in a more advantageous position to withstand desiccation than isolated plants, so that if two or three plants happen to get into this formation their arrangement will tend to be conserved, while isolated plants will tend to die off. Soundings have been made in Adolf Bay and a depth of 108 fathoms has been recorded near the middle. The depth gradually diminishes until the line of boulders is reached (Fig. 2). These are covered only at high tide. Opposite the line of boulders on the other side of the mud flats the shore consists of a steep bank of clay overlaid with relatively well irrigated silt having a

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FIG. 3. The small circles represent the point of establishment of a plant of Dryas; -the shaded area the portions of the plant bearing living leaves and the part enclosed by the broken line the prostrate branch system which becomes covered with Lichens. richer growth of plants than the raised shingle beach system. From the top of this bank the land gradually rises to the base of the mountains about half-a-mile distant. The mud flats which lie to the landward of the line of boulders are uncovered at low tide when they appear as flat stretches of clayey silt with shallow pools. The raised shingle beach which extends for many miles down this side of Klaas Billen Bay comes to an end at Cape Napier (Fig. 2). In this portion of its length it consists essentially of an inclined plane which slopes gradually from Bruce City (Fig. 2), where it is about 15 ft. above the sea-level, to Cape Napier, where it is 4 or 5 ft. above sea-level. Opposite Bruce City there is a flat lower beach which on the average is about 3 ft. above tide-level. Lateral arms of shingle running more or less at right angles to the main bank extend on to the mud flats and are continued by a series of shingle banks across to the other side where they are covered

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RAISED BEACHI OF CLAY AND *:rTTTI:TIT TITTTTTN7?T STuN ES ?0 OUTER MUD FLATS

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with silt brought down by the streams from the mountains. These shingle banks have acted as barriers by which a certain amount of water is retained when the tide falls, forming permanent pools. Of these permanent pools I, II, III, IV (Fig. 4) are still flooded by the tide whereas those at the upper end of the series of pools (Fig. 2)' V, VI, VII are now removed from tidal influence and contain fresh water. The raised shingle beaches are sculptured on the surface by slight depressions which run from the landward side across to the seaward side following a curved course. These are due to wave action when the beach was rising at an earlier stage in its history. The depressions appear darker than the rest of the shingle as they afford a certain amount of shelter to plants. The streams of water from the mountains carry silt towards the shore and tend to fill up the lower lying area to the landward of the shingle bank. However, this silt is not carried right up to the bank as the is deflected towards the right (Fig. 2), and a region comparatively free from silting exists immediately to the landward of the main beach (P1. VI, Fig. 2). The soil is derived principally from the limestone and sandstones of the adjacent mountains and the shingle bank consists of small angular fragments of these comparatively soft rocks. The marsh is dotted here and there with erratic blocks of stone, some of which were doubtless deposited by stranded icebergs from the Nordenskj old Glacier before the marsh had risen above the sea. The larger boulders are represented by black spots in Fig. 4. The chief factor which determines the density of the vegetation seems to be the water supply. The total precipitation is very small, probably less than 8 inches per annum at this end of Klaas Billen Bay. Another very important factor is the depth of the snow in winter. On the raised shingle beach there is probably hardly any snow left owing to drifting, and hence only very prostrate plants can escape desiccation by the wind. But on the moor a constant supply of water is forthcoming from the snow which gradually melts on the mountain slopes during the summer. The plants on the shingle areas are probably de- pendent on the slow melting of the ground ice which occurs everywhere at a depth of about 18 inches below the surface of the ground. Temperature records (6) for Ice Fjord show that July and August are the only months normally free from frost, while June, July, August, and probably the first half of September, form the period in which plant growth can occur. The map (Fig. 4) xepresents a plane-table survey of a portion of the land seen in Fig. 2. It represents the most newly emerged portion of the series of mud flats and pools (Fig. 2, dotted area) and adjacent shingle banks, and more particular attention will be given to the flora of this part of the area. The position of the base line was determined with reference to the survey cairns in the neighbourhood. Diggings were made along a line drawn between the inner and outer mud flats at points marked with asterisks and the results obtained are given diagrammatically in Fig. 5. The strata in the bed of the nmarsh are seen to form a very complicated system. Digging F (which was the

Journ. of Ecology X 8

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deepest made) gives the best indication of the sequence followed in the laying down of these beds. At the bottom of F was found boulder clay mixed with stones and masses of Lithothamnion spp. This was most likely laid down under almost entirely marine conditions at a depth of probably 10 fathoms, at which depth the Lithothamnion Zone usually occurs (4). On being raised it came

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PLAN OF DIGGINGS.. IlORIZONTALSCALE,i"=1O7' . VERTICAL. SCEALET | -13'| _ Q'TEMUD LARTS m D EEMOULFR CLAY S X SHELLS a ^ ~AHI AND 51LT ..:. L IH TU^ r lGNSPP. G? 5 ANDb,S,lLT A tB _ PLAM-r IWPAikS OF OlCA ATTCRxS

EGr . 5. Plan of Diggings. under the influence of silt-bearing streams from the mountains, and its sub- sequent history depended on the rate at which this silting occurred. Small bands of peat occur near the top of the series consisting principally of the remains of Carex (Sautna?). These alternate with silt bands coloured black with organic matter, probably originating from the growth of Cyanophyceae and Diatoms on the surface of a mud flat.

SUBAERIAL SUCCESSION. (a) The zonation of vegetation from the intertidal muld flat to the raised shingle beach, i.e. to about 4 ft. above highest tide mark.

The most complete series of zones of vegetation on this side of the marsh occurs between the Pool III and the summit of the bank on its north-west' side. The silting here is at a minimum.

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Zone 1. At the very edge of the pool. ALGA: Enteromorpha sp. with Glyceria vilfoidea Fr. (a growth form near that of Glyceria maritima but of smaller stature). No panicles were found in Klaas Billen Bay. Advent Bay is the only locality in lee Fjord where it has been found in panicle (2). Zone 2. Musci: Bryum sp. (probably an abnormal form of Bryum nitidulum Lindb.) with a certain amount of stranded Enteromorpha id. sp. Zone 3. Musci: Distichium capillaceum (L.). LICHENES: Stereodon vaucheri (Lesq.) Lindb. (Hypnum vaucheri Lesq.), Lecanora tartarea Ach., Solorina spongiosa Carroll, with occasional globules of CYANOPHYCEAE: Nostoc sp. This zone must be very nearly fresh owing to the leaching out by water percolating through the base of the shingle bank. The zone is marked by the occurrence of debris of wood and seaweeds left by the highest tides which have occurred within the last year or so. This line of drift material is indicated (Fig. 4) by alternating dots and dashes. (Pool II has no supply of fresh water and in character is analogous to a pan (7). It is only flooded by the highest tides of the year. There is no apparent vegetation close to it and the first zone to appear seems to be the Distichium-Stereodon Zone, succeeded by the shingle bank flora.) Zone 4. Slope of shingle with Saxifraga oppositifolia L. var. reptans And. and Hessel., Dryas octopetala L. LICHENES: Stereocaulon paschale Fr. Zone 5. Top of main shingle beach. LIcEENES Dryas octopetala L. (in isolated tussocks). Cetraria islandica Ach. Saxifraga oppositifolia L. var. reptans. ,, nivalis Ach. Pedicularis lanata Willd. f. dasyantha Trautv. Thamnolia vermicularis Ach. Draba alpina var. oblongata R. Br. Stereocaulon pa-schale Fr. Papaver radicateum Rothb. Lecanora tartarea Ach. Leptogium sp.

A later stage in the succession is seen between Pool V and the raised shingle bank to its north-west. The tides never reach this pool now and it is nearly filled with a growth of Carex salina Whlnb. var. subspathacea Warmsk., Juncus biglumis L., Salix polaris Whlnb., Nostoc sp. The moss zone has formed a certain amount of humus and Salix polaris has become established on it (Zone E, Fig. 4). Zone D is drier and has a considerable growth of Dryas. It is probably a development of the Distichium-Stereodon Zone. Right at the top of the series near the huts of Bruce City near Pool VI (Fig. 2) there is in a corresponding position a patch of Cassiope tetragona Don., Salix polaris Whlnb., and Carex misandra R.Br. The mosses build up humus and on this substratum Salix polaris can flourish. By this time the land level has risen well above tidal influence and the water table is lower with respect to the plants. The Salix forms tussocks and together with mosses and lichens increases the depth of the humus. Where this type of soil is well drained and fairly dry Cassiope can become established in sheltered spots. Cassiope-Heath seems to be the climax association under the conditions obtaining in this locality.

8-2

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On the top of the raised shingle banks as far as the phanerogamic vegeta- tion is concerned the vegetation is never closed except in depressions (Plate VII, Fig. 4). The only plants which can be said to flourish on the exposed parts are Dryas octopetala and Saxifraga oppositifolia which both form isolated tussocks.

(b) Zonation on the S.E. side of the marsh from the pools to the moor vegetation on silt and boulder clay.

The series of zones is taken from the right-hand side of the Inner Mud Flats (Fig. 4). In this portion of the area the master factors are, first: the heavy silting' which occurs in the early months of -the summer when the snow on the lower slopes melts, and second: the constant supply of fresh water which flows during the summer in the small streams from the snow on the higher parts of the mountains and the more sheltered corners. The silting apparently inhibits to a large extent the growth of mosses and those plants predominate which are adapted to keep pace with a heavy deposition of silt. At times even these plants are overwhelmed (probably in an exceptionally warm spring or when one of the silt-bearing streams changes its course) as can be seen by examining the stratification of the bed of the marsh (Fig. 5). In some of these diggings (e.g. in F, Fig. 5) there are, as has been already mentioned, layers of Carex (salina?) peat. This has grown in situ as there can be seen well preserved roots in the normal position. There are also mixed with it detached fragments of moss. Zone I. Glyceria vilfoidea Fr. (without panicles), Enteromorpha sp. These occur on the edges of the pools. Zone II. Carex salina Whlnb. var. subspathacea Warmsk. and a certain amount of a moss (probably Bryum nitidulum Lindb.), Dupontiafisheri R. Br. Zone III. In this zone (Fig. 4), extending above the line of highest drift: Carex salina Whlnb. var. subspathacea Warmsk. is gradually dominated by: Eriophorum scheuchzeri Hoppe, Luzula hyperborea R. Br., Eriophorum poly- stachyum L. f. triste Th. Fr. Zone IV. This zone is characterised by the appearance of Salix polaris Whlnb. (P1. VII, Fig. 2). This tends to make a system of tussocks and pools. In the tussocks the following species predominate:

Salix polaris Whlnb. Equisetum arvense var. decumbens C. F. W. Meyer (sterile). Luzula hyperborea R, Br. Stellaria longipes Goldie. Juncus biglumis L. Saxifraga hirculus L. Polygonum viviparum L. Musmi: Hypnum scorpioides, and other mosses characteristic of wet tundra. LICHENES: Lecidea (Psora) decipiens Ach. At the edges of the pools the species represented are- Dupontia fisheri R. Br., Eriophorum scheuchzeri Hoppe, Juncus biglumis L., while Hypnum scorpioides (sterile), Ranunculus hyper-

L This silting process, which interrupts true development, is analogous to the drifting of wind-blown on to the mud flats colonised by Salicornia spp. at Holme, Norfolk (5).

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boreus Rottb., Nostoc sp. often occur totally submerged. This stage is ap- parently fairly permanent owing to physical processes connected with the presence of ground ice at a depth of about two feet which causes the formation on the surface of Polygon-marks (3) which tend to conserve this type of vegetation. This occurs to the right hand of Pool V (Fig. 4), where an idea of the scale of this configuration is given by the outline of a few of these Polygon-marks (the centre of each is shaded).

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These two series of zones, tlie one from brackisli pool to raised sliingle beacli, tlie otlier from pooi to wet "tundra" vegetation, are probably in tlie process of converging to a final Cassiope-Heath Association. In tlie first series tliis climax is reached relatively soon but in the case of the vegetation on silt it is retarded indefinitely by the excessive supply of surface water. Fig. 6 shows diagrammatically these series and their possible convergence to a climax association.

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THE VEGETATION OF THE SHINGLE BANKS.

The vegetation of the Main Shingle Bank has already been described. The lower beach, which lies to the west of Bruce City, Fig. 2X, has a fairly uniform vegetation and is probably at a stage of development comparable to a zone lying above the Distichium-Stereodon Zone of the series between mud flat and shingle bank. But it is in a more favourable position as it is sheltered to the north and east by the main raised shingle bank. The phanerogamic flora is represented by the following species. Near the slope of the main in the relatively damper area of the lower beach: Phippsia algida R. Br., Saxifraga oppositifolia (L.) var. reptans And. and ilessel., S. nivalis L., S. cae- spitosa L. are characteristic of the flora. While out on the drier portions:

Cerastium alpinum L. Wahlbergella apetala Fries. caespitosum Malm. (C. regelii Osten.). Sawifraga caespitosa L. Arenaria ciliata (L.) ,, oppositifolia (L.) var. reptans A. & H. Where this beach rises to a higher level at its southern end Salix and Dryas appear and it seems highly probable that this area is developing rapidly in the direction of a Cassiope-Heath Association. The shingle banks which lie between the middle and outer mud flats are destitute of vegetation, while those lying between the middle and inner mud flats have a zone of Glyceria vilfoidea Fr. at their base where they slope down to the surface of the middle mud flat. The more elevated portion of this small system of banks (indicated with slope marks Fig. 4) has in addition a zone of Carex salina var. subspathacea Warmsk. above the Glyceria zone and is capped with a layer of silt on which occur a few plants of Salix polaris Whlnb., Potentilla pulchella R. Br., Cochlearia ojflcinalis f. arctica, Draba hirta var. arctica Vahl. ALGAL SUCCESSION.

The flora of the bay and brackish pools (4). In the Bay, at a depth of 8-10 fathoms there is a rich vegetation of Litho- thamnion spp. with occasionally Polysiphonia sp. The Laminaria Zone, which occurs at depths of 3-4 fathoms, consists of a rather sparse flora of:

Laminaria (prob. L. Agardii Kjell.). Ceramium rubrum (Huds.) Ag. Desmarestia aculeata (L.) Lamour. Polysiphonia sp. Fucus sp. Sphacelaria arctica Harv. The represented by the line of boulders (Fig. 2) is characterised by the following flora:

Fucus sp. ( Vesiculosus group). Phloeosphora tortilis (Rupr.) Areshoug. Pylaiella litoralis (L.) Kjell. (attached to Chordaria flagelliformis Mill. var. chordae- Fucus). formis Kjell. Rhodomela subfusca Ag. (Rhodomela lycopo- Ulva (cra8sa Kjell. ?). dioides f. tenuissima Kjell.). Characium sp. The flora of the Outer Mud Flats consists of Diatoms and Cyanophyceae. No collections were made of these. The Middle Mud Flats and pools had a more important algal flora of: Enteromorpha sp., Spirulina sp., Oscillatoria sp.

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The Inner Mud Flats were rarely covered by the tide and as they were on the whole unaffected by the small amount of water flowing in from the streams they became caked and dry, showing a crystalline deposit of salt on the surface wetted by the last extra high tide (P1. VII, Fig. 1). Probably as a result of this high concentration of salt they were destitute of vegetation except in the shallow fresh-water channels by which they were traversed. In places in these channels plants of Glyceria vilfoidea Fr. were established in a half-submerged state. On examination of the flora in the Pools III and IV, particularly in the latter, the influence of the fresh water flowing into it was obvious. Sir Nicolas Yermoloff kindly undertook the identification of the diatoms from these pools. In this series of pools a plankton crustacean which occurs in the arctic in the form called Mysis oculata was found in an attenuated form which is known as Mysis oculata var. relicta. C. S. Elton thinks that in this series of pools the transition from the salt to the fresh form is actually occurring. This made me hope that in the case of diatoms which have the animal characteristic of motility and which are able to withstand sudden changes in salt concentration there might be illustrations of the same kind of ecological forms. Sir Nicolas Yermoloff pointed out to me on examination of the diatoms that there are in the samples many transitional forms of the group Navicula radiosa, N. Cincta and N. gracilis, forms closely connected with Navicula gracilis var. schizonemoides V. H. and that he thought that these transitionals were adaptations from a brackish to a fresher environment. The dominating species in these pools were:

Surirella ovalis Bre. Navicula cryptocephala Ktz. Synedra pulchella Kutz. ,, cincta Ehr. Scoliopleura tumida Bre. ,, cincta Heufleri Grun. Navicula viridula var. rostellata transitional ,, Grevillei Ag. to Nav. polaris Lagerst. ,, (Diploneis) interrupta Ktz.

Fresh water species are represented, but by few individuals. In Pool III: salinity (chloride), low tide 0-5674 grm. per litre.; high tide 15-23 grms. per litrel, there occur: ALGAE: Enteromorpha sp. (in large masses), Spirulina sp., Oscillatoria sp. DIATOMS: Synedra pulchella Kutz. (dominating). In Pool IV: salinity high tide, at fresh end 0 5530 grm. per litre, at bottom end 9*101 grms. per litre, there are types characteristic of fresh and brackish conditions as one would expect from the salinity data: Zygnema sp., Ulothrix sp., Rivularia sp., Oscillatoriacsp., Spirulina sp. A small stream of fresh water which sinks into the ground near Pool V (Fig. 4) and wells out of the shingle at S supplies Pool IV with a constant flow of fresh water. At S there are considerable quantities of algae. The actual mouth of the spring is black with a growth of Oscillatoria sp. and round about there occurs a mass of green algae consisting of Ulothrix sp. and others. Among these algae there is

1 These determinations were made by H. C. Mills of Oxford.

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a rich flora of diatoms which are almost exclusively fresh water. The domi- nating species is Diatoma elongatum Ag. while the following are frequent:

Ceratoneis arcus Ktz. Navicula limosa Lagst. Odontidium mutabile W. Sm. Stauroneis minutissima Lagst. Diatoma tenue Ag.

Navicula polaris Lagst. is frequent and can be regarded as a probable sea- escape derived from a closely related brackish or marine form N. peregrina Ehr. Pool V is almost filled with a vegetation of Carex salina, Juncus biglumis L., Nostoc sp. with ocasional tussocks of Salix polaris Whlnb. Above Pool V extending to Pool VI there are a series of smaller pools of much the same character as Pool V. Pool VI is a-large pool with a level bottom of fine mud. It appears to be too deep for colonisation by Phanerogams. Euroglena sp. is an abundant plankton constituent. Occasionally near the margins there are submerged plants of Ranunculus hyperboreus L. which develop flowers of quite normal form under the water. The margins of the ponds away from the shingle banks are composed of a dense turf of mosses with: Musci Saxifraga hirculus L. Timmia austriaca var. arctica (Kindb. Arn.) Chrysosplenium tetrandrum Lund. extreme form. Saxifraga cernua L. Mnium affine var. inteyrifolium Lindb. oppositifolia L. var. reptans A. & H. Webera nutans Hedw. Cardamine pratensis L. Camptothecium nitens (Schreb.) Schimp. It is evident that this turf forms a barrier of vegetation over the mouth of the pool and it is possible that these large pools were formed by a retro- gressive process from a pool in the condition of Pool V by the choking up of its drainage and by the formation of a barrier of vegetation. On the other hand it is possible that they were originally pans like Pool II and have always had a depth of water too great for the development of vegetation, and as there is no silt reaching them they are practically permanent. I am rather inclined to think that the first hypothesis is the most probable as the shingle banks slope abruptly to the water edge in these pools as if the water level had risen since the pool was cut off. The relatively rich flora of these moss banks can be accounted for by the fact that birds frequent these places and the soil must receive a large amount of nitrogenous material. Pool VII is very much of the same type as VI only it has not such a rich flora on its bank. All round the banks of these pools the mosses appear to be encroaching gradually over the pool though the progress must be extremely slight. The silting from the mountain sides is gradually advancing over this area and it is possible that in time the whole of the raised shingle beach will be covered by silt. I am particularly indebted to Mr C. S. Elton of New College, Oxford, who was working at the ecology of the animals, for much assistance in the field in the preparation of the survey and for much stimulating criticism.

This content downloaded from 137.99.31.134 on Mon, 27 Jun 2016 09:30:20 UTC All use subject to http://about.jstor.org/terms JOHN WALTON 121

I take this opportunity to express my thanks to Sir Nicolas Yermoloff, to Miss A. Lorrain Smith and to Mr H. N. Dixon for much kindness in identifying the Diatoms, Lichens and Mosses respectively, and to Mr A. J. Wilmott for much advice in the identification of the Phanerogams.

SUMMARY AND CONCLUSIONS.

1. A portion of a raised beach system in Klaas Billen Bay is described. There are various indications that the land is rising relatively fast. The inclination of the emerging land to the sea at the place described is small, so that a given vertical rise exposes a relatively large area of land for possible colonisation by plants. 2. A plane-table survey of a portion of this area, made in order that changes may be recorded in later years in the topography and vegetation, is figured and described. 3. The zonation of subaerial vegetation is described. It is thought that the succession of vegetation from intertidal mud flat to raised shingle beach is continued until a possible climax is reached in a Cassiope-Heath Association. The succession from the intertidal area on land undergoing silting seems to be arrested by the phenomena of polygon-marks which tend to conserve a swampy type of moor association and which are due to an excess of soil water, the well-drained shingle showing no signs of this polygon formation. 4. The succession from marine, through brackish, to fresh water condi- tions is described. Transitional forms in the diatom flora of the brackish pools are recorded. A retrogressive process is indicated by the occurrence of certain large fresh-water pools.

REFERENCES.

(1) Andersson, G. "Om Vdxlifet i de Arktiska Trakterna." Nordisk Tidskrift, Stockholm, Fig. 10, p. 244, 1900. (2) Asplund, E. "Beitrage zur Kenntnis der Flora des Eisfiordgebietes." Arkiv for Botanik, Band 15, No. 14 (communicated 5th June 1918). (3) Holmsen, Gunnar. "Spitsbergens Natur og Historie." Reprint from Ymer, H.I. 1909. (4) Kjellrnan, F. R. "The Flora of the Arctic Sea." Kong. Sv. Vet.-Akad. Handlingar, Band 20, Stockholm, 1883. (5) Marsh, A. S. "The Maritime Ecology of Holme-next-the-Sea." This JOURNAL, 3, 1915. (6) Nathorst, A. G. "Nya Bidrag till Kannedomen om Spitsbergens Kirlvixter, etc." Kong. Sv. Vet.-Akad. Handlingar, Band 20. Stockholm, 1883. (7) Yapp, R. H., Johns, D., Jones, 0. T. "The Salt Marshes of the Dovey ." This JOURNAL, 5, 1917

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