Seed rain and seed bank along an alpine altitudinal gradient in ...

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Seed rain and seed bank along an alpine altitudinal gradient in Swedish Lapland Ulf Molau and Eva-Lena Larsson

Abstract: We studied the seed flux, including seed rain and seed bank (germinable and total), at twelve sites along an altitudinal gradient in the Abisko area in northernmost Swedish Lapland during a period of 3 years with contrasting summer climates. The study sites were evenly spaced in altitude from the timberline at 700 m above sea level to the highest peaks in the area (1560 m). A subalpine birch forest site was included for comparison. Each site was equipped with seed traps, replaced and emptied directly upon snow-melt each summer. Soil samples for seed bank assessment were taken at all sites, and inventories of the vascular plant flora were carried out in the 10 m radius neighborhood of the traps. The results revealed high variation among years with regard to seed rain and its partitioning over various functional types of plants. Even though most of the seed rain could be attributed to species present in the plant community of the trap sites themselves, some more long-distance dispersal takes place every year. A number of extrazonal recoveries are reported, often several hundred m above the distributional limit of the species. Even though seed number and species diversity declined rapidly from seed rain over total seed bank to germinable seed bank, the correlation among all three aspects of the seed pool was high. The dominant species in the seed flux at moderate altitudes, Empetrum hermaphroditum Hagerup, has a persistent seed bank with an average turnover of more than 200 years. Key words: seed rain, seed bank, total seed bank, germinable seed bank, alpine, dispersal. Résumé : Les auteurs ont étudié le flux de semences, comprenant la pluie de graines et la banque de graines (viable et totale), sur 12 sites le long d’un gradient altitudinal, de la région d’Abisko, dans la partie la plus septentrionale de la Laponie suédoise, au cours d’une période de 3 ans, sous des climats estivaux différents. Les sites d’études étaient uniformément distribués en altitude, à partir de la ligne des arbres, à 700 m du niveau de la mer, jusqu’aux pics les plus hauts de la région, à 1560 m. Les auteurs ont inclus une forêt de bouleaux subalpine, pour fin de comparaison. Chaque site comportait des trappes à graines, replacées et vidées directement à la fonte des neiges chaque été. Sur chaque site, des échantillons de sols ont été prélevés pour évaluer la banque de graines, et des inventaires de la flore vasculaire ont été effectués dans un rayon de 10 m autour des trappes. Les résultats montrent de fortes variations entre les années dans la pluie de graines et dans sa répartition selon divers types fonctionnels de plantes. Bien que la majeure partie de la pluie de graines puisse être attribuée à des espèces présentes dans la communauté des sites où se trouvent les trappes elles mêmes, on observe une certaine dispersion sur de longues distances chaque année. On note également un nombre de présences extrazonales, souvent à plusieurs centaines de mètres au dessus de la limite de distribution de l’espèce. Bien que le nombre de graines et la diversité des espèces diminuent rapidement, de la pluie des graines à la banque totale de graines puis à la banque de graines viables, la corrélation entre les trois parties de la réserve de graines est élevée. L’espèce dominante dans le flux de semences à des altitudes moyennes, l’Empetrum hermaphroditum Hagerup, possède une banque persistante de graines ayant un cycle de renouvellement de plus de 200 ans. Mots clés : pluie de graines, banque de graines, banque de graines totale, banque de graines viables, alpin, dispersion. [Traduit par la Rédaction]

Molau and Larsson

Introduction All vascular plants in the arctic and alpine tundra have at some stage been part of the seed bank s.lat., although the period of time varies. The dynamics of the vegetation and the recruitment of plant individuals are still poorly known in these environments. There are a few minor studies available from Swedish alpine areas (Diemer and Prock 1993; Nielsen 1997), and the most extensive studies in the published record to date emanate from polar semi-deserts in the Canadian Received November 17, 1999. U. Molau and E.-L. Larsson.1 Botanical Institute, Göteborg University, P.O. Box 461, SE 405 30 Göteborg, Sweden. 1

Author to whom all correspondence should be addressed (e-mail : [email protected]).

Can. J. Bot. 78: 728–747 (2000)

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High Arctic and tussock tundra in Alaska (see below). The arctic and alpine flora is regarded as highly sensitive to the impacts of climate change (e.g., Callaghan et al. 1996; Henry and Molau 1997), and the anticipated change in species structure inevitably has to be mediated by the seed rain and the seed bank. A better understanding of the role of the tundra seed bank is therefore crucial for the study of induced succession processes under the impacts of directional environmental change, and will strongly affect the forecasts for future redistribution of plant species and communities. Recruitment of tundra plant individuals from seed is a slow and seemingly almost negligible process, at least in the Low Arctic and in the lower alpine zones in mountain ranges outside the Arctic (Thompson 1978; Bell and Bliss 1980; Archibold 1981). Instead, vegetative means of propagation is the dominant mode of reproduction sustaining pop© 2000 NRC Canada


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ulations of species in situ (cf. Grime 1979). Nevertheless, seed production is immense, at least in years with favorable summer weather (Molau 1993; Khodachek 1997). It is evident that the tundra plants’ ability to disperse by seed and other diaspores (bulbils, spores) must have been, and still is, of crucial importance for the colonization of land areas in primary succession following deglaciation events. Without alloctonous seed influx and the establishment of a seed bank, most of the arctic and the alpine regions would still be barren land. The tundra seed bank is often neglected because of the general view that sexual reproduction becomes less important with increasing latitude or altitude (Thompson 1978; but see Bliss 1958). In recent years, however, there has been a growing awareness of the importance of seed flux in the tundra (e.g., McGraw 1980; Freedman et al. 1982; Gartner et al. 1983; Lévesque and Svoboda 1995). Therefore, we added a seed flux project to the International Tundra Experiment manual (cf. Lévesque et al. 1996; Molau 1996). As a first attempt, the suggested project was implemented in the subarctic–alpine surroundings of Abisko in northern Swedish Lapland. Many species exhibit seed dormancy that lasts longer than to the next growing season, and sometimes more than one winter of stratificationis needed to break dormancy (Gutterman 1993). With regard to tundra plants, the genus Empetrum plays an important role in the persistent seed bank (Vieno et al. 1992; Thompson et al. 1997; Baskin and Baskin 1998). In northern Fennoscandia, Empetrum hermaphroditum Hagerup is often dominant in subalpine and low alpine dwarf-shrub communities, and the turnover of seeds of that species is emphasized in the present study. Thompson (1993) suggested that three elements are needed in any study to understand the role of the seed bank, and thereby, the dynamics of the vegetation: (i) estimation of buried seed density (total and germinable seed bank), (ii) seed production and seed rain, and (iii) sources of colonists after disturbance. Thus, we address the following questions in our study: (1) How does the seed rain fluctuate among years? (2) What is the potential for seed from lower vegetation zones to spread upwards? (3) Is there any correlation between the present seed bank and the current seed rain? (4) Is there any correlation between the total and the germinable seed bank?

Materials and methods Site description The field work was centered at the Latnjajaure Field Station (LFS; 68°21′N, 18°29′E) in northernmost Swedish Lapland (Fig. 1). The Latnjajaure valley is covered by snow for most of the year, and the climate is characterized by cool summers and relatively mild, snow-rich winters (annual minimum temperature ranging from –27.3 to –21.7°C), with a mean annual temperature of −2.0 to –2.9°C (data from 1993–1998). Annual precipitation ranges from 605 (1996) to 990 mm (1993); the mean for 1990–1998 was 809 mm. July is the warmest month with a mean temperature ranging from +5.4 (1992) to +9.9°C (1997). The variability in summer climate is shown in Table 1, which demonstrates the extreme differences among the study years 1995–1997.

729 The vegetation in the valley comprises a wide range of communities varying from dry to wet and from poor and acidic to rich and basic. Even though the geographical situation is subarctic–alpine, the vegetation of the area is representative of the Low Arctic, with Cassiope tetragona, Dryas octopetala, and Carex bigelowii among the dominant species (Molau and Alatalo 1998).

Equipment and sampling The transect employed in the present study ranged from the timber-line in the valley of Kårsavagge (700 m above sea level (asl)) to the high alpine ridges surrounding Lake Latnjajaure (Table 2). We established a set of seed flux stations (trap cohorts) at 100 m intervals of altitude from 700 to 1400 m asl and, in addition, some outpost stations, including the typical subalpine birch forest at Abisko (380 m asl) as a control for mountain birch seed set and the summits of two of the highest peaks of the area (Mt. Kårsatjåkka and Mt. Kieron). The Mt. Kieron station (1540 m asl) was abandoned after the 1996 season because frequent fog restricted accessibility by helicopter and the rocky terrain makes seed trap implementation difficult. Instead, we doubled the trap area at the Mt. Kårsatjåkka station (1560 m asl) in 1996; this peak has easier access and a deeper soil, making seed-trap attachment easier. Sites were assigned to vegetation zones according to the standard classification for the Scandiavian mountain area (e.g., Sjörs 1967). The distribution of sites over the zones is given in Table 2. The border between the subalpine and alpine region is the tree-line ecotone, located at 650–700 m asl in our area. In the alpine region, the low alpine zone is dominated by luxuriant dwarf-shrub heaths. The mid-alpine zone still has a ± continous vegetation cover, but graminoid-rich meadows and snowbeds are abundant; a good indicator species is Cassiope tetragona, which is dominant in this zone in the northernmost Scandes (Sjörs 1967). The high alpine zone (1300 m and above in our area) is characterized by a discontinuous vegetation cover with a dominance of cryptogams and a large cover of open fell fields. The trap stations were put out in late July 1995, well ahead of seed dispersal of any species in the area. Geographical positioning system co-ordinates were stored in the helicopter’s navigation computer to facilitate recovery each year. Each station consisted of four 0.25 m2 plastic FinnTurf™ doormats, spaced about 1 m apart and fixed to the ground by 13 cm nails through each corner. This material had worked well previously for trapping birch seed at Abisko and has also been used successfully for seed dispersal studies with Bartsia alpina and Pedicularis lapponica (Molau et al. 1989; Eriksen et al. 1993). Plastic doormats of this kind are now the standard for seed rain assessments across the polar regions within the International Tundra Experiment (see Molau 1996). Indeed, they turned out to be highly efficient for diaspores of most sizes, and even worked well for Selaginella macrospores and tiny Cassiope seeds (see below). For simplicity in this study, we use the term “seed” for all kinds of diaspores, including Polygonum bulbils and Selaginella macrospores. Plant nomenclature follows Nilsson (1986). Seed traps were exchanged after final snowmelt at each site in the summers of 1996–1998. The samples represent dispersal in late summer and autumn of the preceding year, plus winter dispersal. Thus, the annual figures reported in this study (1995–1997) all resulted from samples taken in the subsequent season (1996–1998). All traps were analyzed in the laboratory of the LSF at an altitude of 990 m. There was a specific replacement set of traps for each station, ensuring that traps were never moved between sites; thus, contamination among sites was avoided. Traps were carried horizontally to LSF in sealed plastic bags (by helicopter from all stations except 1000–1300 m), dried, and emptied in the lab. The resulting debris containing the diaspores was stored in paper bags for later analysis at the Botanical Institute of the Göteborg University. Here, seeds, bulbils, and macrospores were separated from © 2000 NRC Canada



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Fig. 1. The location of the study site in northern Sweden.

all other debris using a dissection microscope. The vascular plant diaspores were identified using a reference collection of diaspores from all species recorded in the study area, gathered by U. Molau in 1995 and 1996. A few taxonomic groups could not be determined to species level and were treated as bulk taxa. These were Luzula spp., Pedicularis hirsuta/lapponica, and Salix spp. Seeds of Salix are impossible to assign to species in the study area (cf. Berggren 1981). In cases where Carex nutlets were found devoid of the utricle or where the utricle (where the species-specific characters are seen) was heavily abraded, they were filed as “Carex sp.” Samples for assessing the seed bank were collected at all sites in early August, 1997. At each seed trap site, five replicate soil samples were taken to investigate the total and germinable seed banks. Each sample was divided into three layers. The top layer consisted of non-decomposed litter, the second layer consisted of partly decomposed, but not humified litter, and the third layer consisted of the underlying soil. The samples from the sites at 1300, 1400, and 1560 m asl were impossible to divide into more than two layers (humus and mineral soil). At each site, subsamples from the five spots were pooled, resulting in a 2-L sample from each layer. Each of these samples was divided into two parts. A total of 2 × 30 L of soil was processed. For assessing the total seed bank, 1 L was sieved under water using a 0.2-mm gauge. After drying, seeds were picked out under a dissection microscope. For assessing the germinable seed bank, the second litre of soil from each site was put in the freezer for three months at –4°C to break dormancy. After thawing, the samples were spread out on sterilized soil, topdressed with sand, and grown in the greenhouse under 24-h light (natural and artificial light) at 20°C. Emerging seedlings were replanted separately in small pots. Seedlings perform differently when germinating in situ than they do when germinating in a greenhouse, where light, nutrients, water, and space are not limiting factors for growth and establishment. This was particularly evident for the graminoids (e.g., Carex bigelowii), which were greener and had longer leaves in the greenhouse than in nature. To ensure proper species identification, the seedlings were kept alive for almost a year. The original results (Appendices A and B) were multiplied with a conversion factor to express results as seeds or seedlings per square metre (Lévesque et

Table 1. Summer climate (June–August) in the Latnjajaure study area during the period from 1995 to 1997. Year

Mean temperature (°C)

Precipitation (mm)

1995 1996 1997

5.19 6.83 8.02

268 201 99

al. 1996); in our study, the conversion factors for total and germinable seed bank were 178 and 80, respectively. The method outlined above (one single stratification period) yields results that are comparable among sites and samples since the samples were all treated equally. However, the persistent seed bank contained a fraction of seeds that needed more than one freezing period to germinate. Thus, to cover this proportion of the seed bank (in particular Empetrum hermaphroditum), a few soil samples (top and mid-layer soil from the 900 m station where Empetrum had peak abundance in the seed bank) were re-frozen after the first germination period and put back in the greenhouse for a second germination trial. The whole process was then repeated a third time. To age the Empetrum seeds in the bottom layer of the soil profile, a batch of five seeds (the minimum number required for reaching the lower biomass limit of analysis samples) from the 900 m site was sent for 14C analysis at the Ångström Laboratory, Uppsala, Sweden. At the same time as the seed bank sampling, an inventory was made of all vascular plant species present within a 10-m radius from the outline of each trap cohort. The resulting floristic lists represent the potential autoctonous diaspore source. In the study area, upper altitudinal limits for all species that appeared in the traps are well-known from an ongoing (1991–) extensive phenological study and inventory within the International Tundra Experiment programme at LFS. The among-year variation in propagule production is best understood when the data are separated into different life forms (i.e., functional types; cf. Chapin et al. 1996). The following functional types were represented in our material: deciduous trees (T), evergreen dwarf shrubs (E), deciduous dwarf shrubs (D), graminoids (G), and herbs (forbs) (H). © 2000 NRC Canada



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Table 2. Locations of the sites in the seed flux study in the Abisko area in northern Sweden. Site No.

Location

Co-ordinates

1 2 3 4 5 6 7 8 9 10 11 12

Abisko Kårsavagge Kårsavagge Kårsavagge Latnjajaure heath Latnjajaure meadow Latnjavagge Latnjavagge Latnjacorru Latnjacorru Mt. Kårsatjåkka Mt. Kieron

68°21.29′N; 68°20.31′N; 68°20.49′N; 68°20.57′N; 68°21.47′N; 68°21.61′N; 68°21.57′N; 68°21.50′N; 68°21.46′N; 68°21.75′N; 68°20.92′N; 68°16.02′N;

18°48.76′E 18°32.53′E 18°32.51′E 18°32.79′E 18°29.42′E 18°29.59′E 18°29.55′E 18°30.28′E 18°31.11′E 18°30.84′E 18°20.05′E 18°38.99′E

Data analysis As in most seed bank studies, the lack of replicates prevents hypothesis testing. Therefore, with few exceptions, only descriptive statistics were employed, using the StatView™ 5.0 package (SAS Institute 1998) for MacIntosh™ computers.

Results Seed rain The door mats served well as seed traps for the most abundant diaspore size classes expected to occur in the seed rain. Particles of size down to Selaginella macrospores (0.58-mm diameter) and the tiniest Ericaceae seeds (e.g., Loiseleuria, Phyllodoce, and Cassiope, 0.33- to 0.50-mm diameter) were trapped in numbers that seemed to be in an adequate relation to what could be expected from the inventories of surrounding vegetation. So-called dust seeds (diameter total seed bank > germinable seed bank. These components of seed flux all reflected the structure of various plant communities at study sites along the transect. This supported previous evidence from tundra habitats that seed dispersal is extremely local, showing a leptocurtic distribution with regard to distance from the source plant: most seeds fall within the first meter but a few are dispersed into other vegetation belts.

Acknowledgements We thank the Abisko Scientific Research Station and its staff for their support during the field work. Laboratory assistant Vivian Aldén fractioned the samples from the seed traps and Margit Fredrikson assisted with the analysis of the soil samples for total seed bank. The greenhouse staff at the Kungälv municipal greenhouse are gratefully acknowledged for their help during the germination of soil seed bank. We thank Elisabeth Cooper, Olga Khitun, and helicopter pilot Lars “Lidas” Lidström for field assistance with the seed traps and Olle Nordell for practical advice. Financial support for this study was received from the Swedish Natural Sciences Research Council (to U.M.; grant No. B-BU 08424), the Royal Academy of Arts and Science in Göteborg (to E.L.L.) and Wilhelm och Martina Lundgrens Vetenskapsfond and P. A. Larssons Stipendiefond (to E.-L.L.). Finally, we thank Åslög Dahl, Uno Eliasson, and Bente Eriksen for critical reading of earlier drafts of this paper.

References Archibold, O.W. 1981. A comparison of seed reserves in arctic, subarctic, and alpine soils. Can. Field Nat. 98: 337–344. Baskin, C.C., and Baskin, J.M. 1998. Seeds. Ecology, biogeography, and evolution of dormancy and germination. Academic Press, San Diego, Calif. Beerling, D.J. 1998. Biological flora of the British Isles. Salix herbacea L. J. Ecol. 86: 872–895. Berggren, G. 1981. Atlas of Seeds. Part 3. Salicaceae–Cruciferae. Swedish Museum of Natural History, Stockholm. Bell, K.L., and Bliss, L.C. 1980. Plant reproduction in a high Arctic environment. Arct. Alp. Res. 12: 1–10. Bliss, L.C. 1958. Seed germination in arctic and alpine species. Arctic, 11: 180–188. Callaghan, T.V., Maxwell, B., Molau, U., Oechel, W.C., and Panikov, N.S. 1996. Terrestrial ecosystems and feedbacks on climate change. In Arctic systems: natural environments, human actions, nonlinear processes. Edited by J. Lloyd Wright and C.W. Sheehan. International Arctic Science Committee, Oslo. pp. 68–82. Chambers, J.C., MacMahon, J.A., and Haefner, J.H. 1991. Seed and trapment in alpine ecosystems: effect of soil particle size and diaspore morphology. Ecology, 72: 1668–1677.

Can. J. Bot. Vol. 78, 2000 Chapin, F.S., III, Bret-Harte, M.S., Hobbie, S.E., and Zhong, H. 1996. Plant functional types as predictors of transient responses of arctic vegetation to global change. J. Veg. Sci. 7: 347–358. Diemer, M., and Prock, S. 1993. Estimates of alpine seed bank size in two Central European and one Scandinavian subarctic plant communities. Arct. Alp. Res. 25: 194–200. Drake, D.R. 1998. Relationship among the seed rain, seed bank and vegetation of a Hawaiian forest. J. Veg. Sci. 9: 103–112. Eriksen, B., Molau, U., and Svensson, M. 1993. Reproductive strategies in two arctic Pedicularis species (Scrophulariaceae). Ecography, 16: 154–166. Freedman, B., Hill, N., Svoboda, J., and Henry, G. 1982. Seed banks and seedling occurrence in a high Arctic oasis at Alexandra Fjord, Ellesmere Island, Canada. Can. J. Bot. 60: 2112–2118. Gartner, B.L. Chapin, S.F., and Shaver, G.R. 1983. Demographic patterns of seedling establishment and growth of native graminoids in an Alaskan tundra disturbance. J. Appl. Ecol. 20: 965–980. Grime, J.P. 1979. Plant strategies and vegetation processes. John Wiley and Sons, Toronto. Gutterman, Y. 1993. Maternal effects on seeds during development. In Seeds. The ecology of regeneration in plant communities. Edited by M. Fenner. CAB International, Oxon, U.K. pp. 27–60. Hatt, M. 1991. Samenvorrat von zwei alpinen Böden. Ber. Geobot. Inst. Rübel, 57: 41–71. Henry, G.H.R., and Molau, U. 1997. Tundra plants and climate change: the International Tundra Experiment (ITEX). – Global Change Biol. 3 (Suppl. 1): 1–9. Khodachek, E.A. 1997. Seed reproduction in arctic environments. Opera Bot. 132: 129–135. Lévesque, E., and Svoboda, J. 1995. Germinable seed bank from polar desert stands, Central Ellesmere Island, Canada. In Global change and arctic terrestrial ecosystems. Edited by T.V. Callaghan, U. Molau, M.J. Tyson, J.I. Holten, W.C. Oechel, T. Gilmanov, B. Maxwell, and B. Sveinbjörnsson. European Commision: Ecosystems research report, 10: 97–107. Lévesque, E., Desforges, M.N., Jones, G.A., and Henry, G.H.R. 1996. Germinable seed/propagule banks monitoring at ITEX sites. In ITEX manual. Edited by U. Molau and P. Mølgaard. Danish Polar Center, Copenhagen. pp. 43–45. Marchand, P.J., and Roach, D.A. 1980. Reproductive strategies of pioneering alpine species: seed production, dispersal, and germination. Arct. Alp. Res. 12: 137–146. McGraw, J.B. 1980. Seed bank size and distribution of seeds on cottongrass tussock tundra, Eagle Creek, Alaska. Can. J. Bot. 58: 1607–1611. McGraw, J.B., and Day, T.A. 1997. Size and characteristics of a natural seed bank in Antarctica. Arct. Alp. Res. 29: 213–216. Miller, G.R., and Cummins, R.P. 1987. Role of buried viable seeds in the recolonization of disturbed ground by heather (Calluna vulgaris (L.) Hull) in the Cairnorm mountains, Scotland, U.K. Arct. Alp. Res. 19: 396–401. Molau, U. 1993. Relationships between flowering phenology and life history strategies in tundra plants. Arct. Alp. Res. 25: 391–402. Molau, U. 1995. Reproductive ecology and biology. In Parasitic plants. Edited by M.C. Press and J.D. Graves. Chapman & Hall, London. pp. 141–176 Molau, U. 1996. Seed rain monitoring at ITEX sites. In ITEX Manual. Edited by U. Molau and P. Mølgaard. Danish Polar Center, Copenhagen. p. 42. Molau, U., and Alatalo, J.M. 1998. Responses of subarctic-alpine plant communities to simulated environmental change: biodi© 2000 NRC Canada



Molau and Larsson versity of bryophytes, lichens, and vascular plants. Ambio, 27: 322–329. Molau, U., Carlsson, M., Dahlberg, A., and Hill, Ö. 1989. Mating system and pollen-mediated gene flow in Bartsia alpina. Oikos, 55: 409–419. Morin, H., and Payette, S. 1988. Buried seed population in the montane, subalpine, alpine belts of Mount Jacques-Cartier, Québec. Can. J. Bot. 56: 101–107. Nielsen, A.L. 1997. Seedling establishment in a frost disturbed subarctic environment. M.Sc. thesis, Botanical Institute, University of Copenhagen. Nilsson, Ö. 1986. Nordisk fjällflora. Bonniers, Stockholm. [in Swedish]. SAS Institute Inc. 1998. StatView 5.0. SAS Institute Inc., Cary, N.C. Sjörs, H. 1967. Nordisk växtgeografi. 2nd ed. Bonniers, Stockholm. [in Swedish].

737 Spence, J.R. 1990. Seed rain in grassland, herbfield, snowbank, and fellfield in the alpine zone, Craigeburn Range, South Island, New Zealand. New Zeal. J. Bot. 28: 439–450. Thompson, K. 1978. The occurrence of buried viable seeds in relation to environmental gradients. J. Biogeogr. 5: 425–430. Thompson, K. 1993. The functional ecology of seed banks. In Seeds. The ecology of regeneration in plant communities. Edited by M. Fenner. CAB International, Oxon, U.K. pp. 231–258. Thompson, K., Bakker, J., and Bakker, R. 1997. The soil seed bank of North West Europe: methodology, density and longevity. Cambridge University Press, Cambridge, U.K. Vieno, M., Komulainen, M., and Neuvonen, S. 1992. Seed bank composition in a subarctic pine-birch forest in Finnish Lapland: natural variation and the effect of simulated acid rain. Can. J. Bot. 71: 379–384.

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Appendix A Table A1. Total seed bank at the sites along the altitudinal gradient in the Abisko area in 1997. For site numbers and locations, see Andromeda

Arabis

Astragalus

Betula

Betula

Betula

Carex

Carex

Cassiope

Cerastium

Diapensia

Empetrum

polifolia

alpina

alpinus

nana

tortuosa

spp.

bigelowii

spp.

tetragona

alpinum

lapponica

hermaphroditum

— — —

— — —

2 — —

15 5 —

3 3 —

— — —

— — —

— — —

— — —

— — —

152 211 8

— — —

— — —

— — —

— — —

6 — —

— — —

— — —

— — —

— — —

— — —

— — —

744 32 1

— — 1

— — —

— — —

4 — —

— — —

— — —

— — —

—

— — —

— — —

9 — —

53 12 10

— — —

— — —

— — —

10 7 —

— — —

— — —

— 2 —

—

— — —

— — —

— — —

1118 452 19

— — —

— — —

— — —

— — —

— — —

— — —

2 2 —

—

— — —

1 — —

— — —

—

6 1

5

— — —

1 — —

1 — —

— — —

1 — —

— — —

6 6 —

711 1 1

— — —

— — —

— — —

— 1

— — —

— — —

— — —

— — —

— — —

— — —

9 9 —

5 13 —

— — —

— — —

— — —

— — —

— — —

— — —

— — —

— — —

11 4 —

11 8 1

54 — —

— — —

— — —

— —

— —

— —

— —

— —

— —

— —

— —

— —

— —

— —

— —

— —

— —

— —

— —

— —

— —

— —

— —

— —

— —

— —

— —

— —

Abisko (1) Top layer — Middle layer — Bottom layer — 700 m (2) Top layer — Middle layer — Bottom layer — 800 m (3) Top layer 10 Middle layer — Bottom layer — 900 m (4) Top layer — Middle layer — Bottom layer — 1000 m heath (5) Top layer — Middle layer — Bottom layer — 1000 m meadow (6) Top layer — Middle layer — Bottom layer — 1100 m (7) Top layer — Middle layer — Bottom layer — 1200 m (8) Top layer — Middle layer — Bottom layer — 1300 m (9) Upper layer — Lower layer — 1400 m (10) Upper layer — Lower layer — 1560 m (11) Upper layer — Lower layer —

3 1

4 —

—

—

Poaceae

15 15

— — —

11 8 —

— — —

— —

— —

— —

— —

— —

— —

— —

— —

— —

— —

— —

—

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Table 2. Loiseleuria

Luzula

Phyllodoce

Polygonum

Potentilla

Salix

Saxifraga

Selaginella

Silene

Tofieldia

Vaccinium

Vaccinium

Viola

procumbens

sp.

coerulea

viviparum

sp.

sp.

stellaris

selaginoides

acaulis

pusilla

myrtillus

uliginosum

biflora

Indeterminate

— — —

— — —

— — —

— — —

— — —

— — —

— — —

— — —

— — —

— — —

13 6 —

— — —

— — —

— — —

185 225 8

— — —

— — —

— — —

— — —

— — —

— — —

— — —

— — —

— — —

— — —

— — —

— — —

— — —

— — —

750 32 2

10 — —

— — —

2 — —

— — —

— — —

— — —

— — —

— — —

4 — —

— — —

13 — —

— — —

— — —

114 21 237

— — —

— — —

— — —

— — —

— — —

— — —

— — —

— — —

— — —

— — —

— — —

— — —

— — —

— 1 —

1128 466 19

— — —

1 — —

— — —

12 — —

— 2 —

— — 1

— — —

— — —

— — —

— — —

— — —

— — —

— — —

— — —

16 15 2

— — —

2 — —

— — —

32 — —

— — —

— — —

1 — —

205 851 3185

— — —

— — —

— — —

— — —

10 — —

— — —

— — —

— — —

22 — —

— — —

1 — —

— — —

—

14 — —

— — —

— — —

— — —

— — —

— — —

66 38 36

— — —

— 13 —

— — —

11 — —

— — —

— — —

— — —

— — —

— — —

— — —

— — —

— — —

— — —

— — —

98 33 1

— —

— —

— —

— —

— —

— —

— —

— —

— —

— —

— —

— —

— —

— —

— —

— —

2 —

— —

— —

— —

— —

— —

— —

— —

— —

— —

— —

— —

— —

—

— —

2 —

— —

— —

— —

— —

— —

— —

— —

— —

— —

— —

— —

— —

—

9 6 226

1 36

Sum

970 859 3186

2

2

© 2000 NRC Canada



740

Can. J. Bot. Vol. 78, 2000

Appendix B Table B1. Germinable seed bank at the sites along the altitudinal gradient in the Abisko area in 1997. For site numbers and locations, Betula tortuosa Abisko (1) Top layer — Middle layer — Bottom layer — 700 m (2) Top layer — Middle layer — Bottom layer — 800 m (3) Top layer 1 Middle layer 1 Bottom layer — 900 m (4) Top layer — Middle layer — Bottom layer — 1000 m heath (5) Top layer — Middle layer — Bottom layer — 1000 m meadow (6) Top layer — Middle layer — Bottom layer — 1100 m (7) Top layer — Middle layer — Bottom layer — 1200 m (8) Top layer — Middle layer — 1300 m (9) Upper layer — Lower layer — 1400 m (10) Upper layer — Lower layer — 1560 m (11) Upper layer — Lower layer —

Cardamine bellidifolia

Carex bigelowii

Carex spp.

Deschampsia flexuosa

Empetrum hermaphroditum

Eriophorum cf. angustifolium

Luzula arcuata

— — —

— — —

— — —

— — —

2 — —

— — —

— — —

— — —

— — —

— — —

1 — —

3 — —

— — —

— — —

— — —

1 — —

— — —

— — —

5 — —

— — —

— — —

— — —

— — 6

— — —

— — —

18 22 —

— — —

— — —

— — —

1 1 —

— — —

— — —

— — —

— — —

— 2 —

— — —

— — —

— — —

— — —

— — —

5 — —

— — —

— — —

1 — —

— — —

— 1 1

— — —

— — —

— — —

— —

— 1

— —

— —

— —

— —

— 1

— —

— 1

— —

— —

— —

— —

— 1

2 —

— —

— —

— —

— —

— —

— —

— —

— —

— —

— —

— —

— —

— —

© 2000 NRC Canada



Molau and Larsson

741

see Table 2. Luzula parviflora/ wahlenbergii

Polygonum viviparum

Saxifraga foliolosa

Silene acaulis

cf. Solidago virgaurea

Vaccinium vitis-idaea

Vaccinium uliginosum

Plants that died as seedlings

Contamination

Sum

— — —

— — —

— — —

— — —

— — —

— — —

— — —

— — —

— — —

2 — —

— — —

— — —

— — —

— — —

— 1 —

— — —

— — —

— 1 —

— — —

4 2 —

— — —

— — —

— — —

— — —

— — —

1 — —

— 1 —

— — —

— 1 —

8 3 —

— — —

— — —

— — —

— — —

— — —

— — —

— — —

3 2 —

— 1 —

21 25 6

— — —

— — —

— — —

— — —

— — —

— — —

— — —

— — —

1 — 1

2 3 1

— — —

1 — —

— — —

1 — —

— — —

— — —

— — —

— — —

— — —

7 — —

— — —

7 1 1

— — —

— — —

—

— — —

— — —

— 1 —

— — —

8 6 2

— 1

1 —

— —

— —

— —

— —

— —

— —

— —

3 3

— —

— —

— —

— —

— —

— —

— —

— —

— —

— 2

— —

— —

— —

— —

— —

— —

— —

— —

2 —

4 —

— —

— —

— —

— —

— —

— —

— —

— —

— —

— —

© 2000 NRC Canada



742

Can. J. Bot. Vol. 78, 2000

Appendix C Table C1. Comparison between species structure of the plant community present at each trap station (within a 10-m radius), the seed rain, and the total and germinable seed banks. For site numbers and locations, see Table 2.

Species

Functional typea

Altitudinal range along transect (m)

Andromeda polifolia Anthoxanthum alpinum Arabis alpina

E G H

380–1050 380–1200 380–1050

Astragalus alpinus

H

380–1200

Bartsia alpina

H

380–1200

Betula nana

D

380–1200

Betula tortuosa

T

380–700(–1150)

Calamagrostis lapponica

G

380–1200

Campanula rotundifolia

H

380–1000

Cardamine bellidifolia

H

1100–1560

Carex atrata

G

380–1200

Carex bigelowii

G

700–1400

Carex fuliginosa

G

800–1300

Seed bank (× 103)c Site No.

Seed rain

3 6 6 7 6 7 6 7 1 2 3 4 5 6 8 9 10 11 1 2 3 5 6 1 2 4 5 7 8 9 2 3 5 6 7 9 10 7 10 3 4 3 4 5 6 7 8 9 3 4 5 6 7 8

9.0 1.3 0.3 0.7 6.0 0.3 49.0 0.7 6.0 3.3 39.0 5.3 5.0 0.7 18.3 0.3 0.3 0.3 423.3 38.3 0.7 0.3 0 2.7 4.0 0.7 1.0 0.3 2.3 0.3 0.3 1.0 1.3 0.3 0.7 1.7 0.3 1.7 0 0.3 0.3 0.3 1.3 5.7 7.0 24.0 3.7 11.0 0.3 0.3 5.3 11.0 24.3 4.0

b

Total 2.0 0 0.2 0 0.2 0 0 0 0.4 0 0.7 3.0 0 0 0 0 0 0 3.6 1.0 0 0 0.2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.4 0.7 2.1 3.2 2.7 0 0 0 0 0 0 0

Germinable

Inventoryd

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.2 0 0 0.1 0.5 0.2 0 0.3 0.2 0.1 0 0 0 0 0 0

x x x — x — x x x x x x x x — — — — x x — — — x x x x x x — — — — — — — — x x — — x x x x x x x — — — x x x © 2000 NRC Canada



Molau and Larsson

743

Table C1 (continued). Species

Functional typea


Carex juncella Carex lachenalii

G G

380–500 380–1300

Carex Carex Carex Carex

G G G G

380–450 800–1200 380–1100 380–1200

macloviana norvegica parallela vaginata

Carex sp.

G

Cassiope hypnoides

E

700–1560

Cassiope tetragona

E

750–1400

Cerastium alpinum Cerastium sp. Deschampsia alpina Deschampsia flexuosa

H H G G

380–1200

Diapensia lapponica

E

700–1400

Draba fladnizensis

H

800–1500

Dryas octopetala

E

700–1300

Empetrum hermaphroditum

E

380–1250

900–1400 380–1200

Seed bank (× 103)c Site No. 9 1 7 8 9 11 1 6 6 3 6 7 3 4 5 6 7 8 2 3 5 6 7 8 10 3 4 5 6 7 8 9 10 5 9 5 5 7 3 4 5 6 7 8 6 7 8 10 11 5 6 7 8 1 2 3 4

Seed rain 11.0 0.7 1.0 1.7 0.3 0.3 0.3 8.3 0.3 0.7 0.3 2.0 1.3 0 0.3 0.7 0 0 0.3 1.3 11.7 1.3 1.7 0.3 1.0 4.3 0.7 21.0 8.7 1.7 101.3 36.3 0.7 0 0.3 0.3 0 0 7.3 0.7 3.3 2.0 2.0 1.0 0.3 1.0 3.3 3.3 0.3 0.3 11.3 2.7 0.7 324.7 290.0 85.3 84.3

b

Total 0 0 0 0 0 0 0 0 0 0 0 0 0.7 0.7 1.2 1.1 3.2 3.6 0 0 0 0 0 0 0 0 0 0 0 0 9.6 0 0 0.2 0 0 0 0 1.6 0 0 0 0 0 0 0 0 0 0 0 0 0 0 66.0 138.3 13.3 282.9

Germinable 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.1 0.1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.2 0.3 0.4 3.2

Inventoryd — — — — — — — x x x x x

— — x x x — x — — x x x x x x — — x — x x x x x x — — — — — — x x — x x x x

© 2000 NRC Canada



744

Can. J. Bot. Vol. 78, 2000


Functional typea


Epilobium anagallidifolium

H

800–1300

Eriophorum angustifolium Eriophorum scheuchzeri

G G

380–1000 380–1300

Euphrasia frigida Festuca ovina

H G

400–1200 380–1400

Festuca vivipara

G

800–1400

Gentiana nivalis

H

700–1200

Hieracium alpinum coll.

H

700–1200

Juncus trifidus

G

600–1400

Kobresia myosuroides

G

800–1200

Loiseleuria procumbens

E

700–1300

Luzula arcuata

G

900–1560

Luzula parviflora/wahlenbergii Luzula sp.

G G

900–1250

Minuartia biflora

H

900–1300


Seed rain 1.3 3.0 0.7 0 0.3 0.3 0.7 0.3 0 1.3 0.3 0.7 15.7 7.7 3.0 17.0 14.3 2.0 1.0 7.0 9.0 2.7 1.0 0.3 0.3 0.3 0.3 0.3 1.3 2.3 1.7 0.3 3.0 4.3 5.0 2.0 1.0 0.7 0.3 0.3 118.7 0.7 0.3 ? ? ? ? 0.7 0.3 8.7 7.7 7.7 6.0 37.3 10.7 2.7 5.0

b

Total 0.2 0.9 5.3 3.4 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1.8 0 0 ? ? 0.1 ? 0 0 0.2 0.4 0 2.3 0 0.4 0.4 0

Germinable 0 0 0.1 0 0 0 0 0 0.4 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.2 0.1 0.1 0 0 0 0 0 0 0 0 0 0

Inventoryd x x x x — — — — — — — x — x x x x x x — x x x — — — x — — — x x x x x — — — x — — — x x x x x

x © 2000 NRC Canada



Molau and Larsson

745


Functional typea


Minuartia rubella Oxyria digyna

H H

1000–1200 800–1300

Oxytropis lapponica Pedicularis hirsuta/lapponica

H H

800–1150 380–1350

Phyllodoce coerulea

E

380–1200

Pinguicula vulgaris

H

380–1200

Poa alpina

G

600–1300

Poa arctica Poaceae, indet. Polygonum viviparum

G G H

900–1400

Potentilla crantzii

H

380–1200

Potentilla sp. Ranunculus glacialis Ranunculus nivalis Rhinanthus minor Rhodiola rosea Salix spp.

H H H H H D

1000–1560 800–1300 380–500 500–1300

380–1400


Seed rain 2.3 0.3 0.3 0.3 0.3 0.7 0.3 1.0 1.3 1.7 0.7 2.3 8.7 35.3 1.3 43.7 5.3 0.2 33.7 0.7 6.7 8.0 2.7 2.0 20.3 2.0 0.2 31.7 0.7 0.7 0.3 0.3 7.7 0 5.0 105.3 192.3 86.7 10.7 0.5 0.3 1.0 0.3 — 0.3 0.7 0.3 0.3 0.3 3.3 7.0 1.3 45.0 4.3 8.3 21.7 131.3

b

Total 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.4 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.2 2.1 6.0 3.9 2.0 0 0 — 0 0 0.4 0 0 0 0 0 0 0 0 0.2 0 0.2 0 0

Germinable 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.1 0.6 0.1 0 0 — 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

Inventoryd — — — — — — — x x x x x x x x x x — x — x x — — — — — x x — — — — x x x x x x — x x x x —

© 2000 NRC Canada



746

Can. J. Bot. Vol. 78, 2000


Functional typea


Saxifraga aizoides

H

380–1150

Saxifraga foliolosa Saxifraga oppositifolia

H E

900–1400 800–1400

Saxifraga rivularis Saxifraga stellaris

H H

900–1400 800–1200

Saxifraga tenuis

H

800–1300

Selaginella selaginoides

E

700–1100

Silene acaulis

E

700–1400

Silene wahlbergella Solidago virgaurea

H H

900–1200 380–1100

Taraxacum croceum coll.

H

380–1000

Thalictrum alpinum

H

700–1200

Tofieldia pusilla

H

800–1200

Trisetum spicatum

G

600–1200

Trollius europaeus

H

380–1200

Vaccinium myrtillus

D

380–1200

Vaccinium uliginosum

D

380–1300

Veronica alpina/fruticans

H

700–1300

Viola biflora

H

600–1200

Seed bank (× 103)c Site No. 10 11 6 7 7 6 7 9 3 6 6 7 3 4 5 6 7 10 6 7 8 6 1 2 2 12 6 7 3 6 7 3 5 6 7 8 6 8 1 2 3 4 1 3 4 6 3 4 5 7 6 10 12

Seed rainb 14.0 0.3 0.3 1.0 0 4.7 3.3 0.7 1.7 0 1.7 0.3 0.3 0 0.3 23.7 0.3 1.0 5.0 3.0 1.0 0.3 0.3 0 0.3 0.3 0.3 1.0 16.7 3.3 1.3 4.7 0.7 9.0 3.0 0.3 1.0 0.3 168.7 0.7 9.7 7.7 72.7 3.0 0.3 1.0 2.3 3.3 0.7 0.3 7.0 0.3 6.0

Total 0 0 0 0 0 0 0 0 0 0.2 0 0 42.9 0 0 755.9 6.6 0 0 2.5 0 0 0 0 0 0 0 0 0.7 0 0 0 0 0 0 0 0 0 3.4 0 0 0 0 0 0 0 0 0 0 0 0.2 0 —

Germinable 0 0 0 0 0.1 0 0 0 0 0 0 0 0 0 0 0 0 0 0.1 0 0 0 0 0.1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.1 0 0 0 0 0 0 0 0 —

Inventoryd

— — — x x — — — — — — x — x x — x x x x — x — — x x x x x — — x — — x — x x — — x x x x — — — — x — —

Note: Nomenclature according to Nilsson (1986). a D, deciduous shrub or dwarf shrub; E, evergreen dwarf shrub; G, graminoid; H, herb; T, tree (deciduous). b Seed rain data are averages over 3 years, given as diaspores per year per square metre. c Seed bank data are from the 1997 survey of the transect in the Abisko area, given as diaspores or seedlings per square metre. d Presence in the 1997 site inventory is marked with “x.” © 2000 NRC Canada



Molau and Larsson

747

Table C2. Vascular plant species found in the 1997 inventory of the seed rain stations (10-m radius) in the Abisko area that were neither recovered in the seed rain nor in the seed bank. For site numbers and locations, see Table 2. Species

Site number where present

Agrostis mertensii Antennaria alpina Arctospaphylos alpinus Campanula uniflora Carex capillaris Carex buxbaumii ssp. mutica Carex rupestris Carex saxatilis Cerastium arcticum Cerastium glabratum Erigeron uniflorum Eriophorum vaginatum Equisetum arvense Geranium sylvatica Gymnadenia conopsea Huperzia selago Juncus biglumis Juniperus communis Linnaea borealis Luzula multiflora Luzula spicata Lycopodium annotinum Parnassia palustris Pinguicula alpina Pyrola minor Rhododendron lapponicum Rubus chamaemorus Saussurea alpina Scirpus caespitosus Vaccinium oxycoccos Vaccinium vitis-idaea

6 6 (1–4, 6) 6, 7 3, 4, 6 3 4, 6 3 4, 6, 7 6 6 4 1–3, 6, 7 3 3 3–11 3 2–4 1 6, 7 6 3, 7 6 3, 6, 7 6 4, 6 3 3, 4, 6 3, 4 3 1, 2, 5–10

Note: Nomenclature according to Nilsson (1986).

© 2000 NRC Canada
