7 Altitudinal Zonation of Vegetation in Continental West Greenland: A Basis for Monitoring Climate Change

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1 7 Altitudinal Zonation of Vegetation in Continental West Greenland: A Basis for Monitoring Climate Change Birgit Sieg, Institute of Plant Ecology, Münster, Germany INTRODUCTION The importance of global change monitoring in the Arctic has quite often been emphasized (e.g. Callaghan and Jonasson, 1995b; Chapin et al., 1992). On the one hand the Arctic contains important drivers of global change, which will also affect other regions of the world: the melting of glaciers and ice caps will lead to a rise in sea-level, the reduction of sea ice will allow increased absorption of solar radiation and a further increase in temperature (Hagen et al., 2001). The thawing of permafrost and increasing decomposition rates of organic soil material have the potential to release considerable quantities of methane and carbon dioxide (e.g. Oechel et al., 1993; Smith and Shugart, 1993; Thannheiser et al., 1998). The polar regions will therefore play a substantial role in driving global climate change through positive feedbacks to global warming (Hagen et al., 2001). On the regional level, climate change can lead to an altered quality of plant tissues as perceived by herbivores (e.g. reindeer and muskoxen) and decomposers (Callaghan and Jonasson, 1995b) and therefore has a great impact on food chains and nutrient cycling in arctic ecosystems. An observation of this regional level is particularly important for the people living in the Arctic who depend on its natural resources (Chapin et al., 1992). On the other hand, the Arctic can serve as an early warning system because the effects of climate change there are expected to be stronger and faster than elsewhere on Earth (Hagen et al., 2001). This can be explained by the fragility of arctic ecosystems (slow growth, low fecundity and low species richness of plants) together with a disproportional temperature rise (Callaghan and Jonasson 1995a; Chapin and Körner, 1995; Maxwell, 1992). A number of writers have also stressed that high mountains will be strongly affected by climate change and provide good opportunities to monitor it (e.g. Becker and Bugman, 2001; Callaghan and Jonasson, 1995b; Grabherr et al., 2004). Hence, it seems highly desirable to investigate mountain systems in the Arctic, as the combined effects of high latitude and altitude should provide a sensitive indication system for climate change. In the Arctic the shortage of meteorological stations with standardized, long-term data does not allow a good spatial resolution of climate change monitoring. However, the responses of plants to long-term climate in their habitat mean that they can be used as bioclimatic indicators and thus fill these data gaps (Elvebakk, 1999). In northeast Greenland such a monitoring site has

2 already been established (ZERO line, see Fredskild and Mogensen, 1997). However, the problem is that in many Arctic areas the present status of ecosystems is insufficiently described. For example, in continental West Greenland the flora and vegetation of altitudes above 700 m a.s.l. have not yet been studied. Thus, a basis for further investigations is needed. The project Altitudinal Zonation of Vegetation in Continental West Greenland, carried out by members of the Institute of Plant Ecology, is designed to provide this. CLIMATE CHANGE MONITORING IN MOUNTAIN REGIONS The investigation of altitudinal shifts of plants and communities is an important tool for climate change monitoring in mountain regions (Downing et al., 2001; see also e.g. Grabherr et al., 1995; Meshinev et al., 2000). The altitudinal temperature gradient is strong and therefore the distances for plant migrations in response to a changed climate are short. Short migration distances are important for many arctic and alpine plants because of their low migration rates (Callaghan and Jonasson, 1995a; Grabherr et al., 1995). The time lag between a change in climate and the response of vegetation is therefore reduced in mountains in comparison to the response of vegetation in latitudinal direction. Furthermore, factors which would make interpretation of shifts difficult, like migration barriers (mountain ranges) or changes in abiotic conditions (e.g. bedrock), are not likely to occur over short distances. For the detection of altitudinal shifts it is necessary to know the present altitudinal distribution of plants, communities and vegetation belts. The aim of our study is therefore to provide a model of altitudinal vegetation belts that will take into account flora, vegetation and ecological conditions. As the latitudinal vegetation zones are partly reflected in the altitudinal belts (CAVM Team, 2003; Dahl, 1986; Sieg and Daniëls, 2004), the investigation of altitudinal shifts could also lead to predictions about the changes that might occur in the latitudinal vegetation zones in the future. INVESTIGATION AREA The investigation area consists of the localities Angujârtorfik and Kangerlussuaq, which are situated a few kilometres north of the polar circle in the inland of West Greenland (Figure 7.1). They are characterized by a low-arctic continental climate and gneissic bedrock (Böcher, 1954). Mountains rise to 1,070 m a.s.l. and are built up by lake-rich, partly extensive plateaus in different altitudes. The localities are characterized by a general absence of human influence, and thus anthropogenic causes of detected changes in the vegetation can be excluded. Angujârtorfik is a target region for implementation of GLORIA sites (Grabherr et al., 2004). MODEL OF ALTITUDINAL VEGETATION BELTS The aim of the project is to provide a model of altitudinal vegetation belts in continental West Greenland covering indicator species, growth forms, vegetation communities, vegetation patterns and habitat conditions (cf. Sieg and Daniëls, 2004). An altitudinal delimitation of these vegetation belts will be given. 51

3 Figure 7.1 Investigation area Sisimiut Kangerlussuaq Søndre Strømfjord Inland ice Angujârtorfik 25 km Sukkertoppen ice-cap The characterization of the altitudinal belts will be based on approximately 500 vegetation relevés (including soil samples of the rhizosphere) carried out in all altitudes and habitats in the summers of 2000 to Following the principles of the Braun-Blanquet approach (Westhoff and van der Maarel, 1973), these relevés have been made in homogeneous stands with a plot size of 1 4 m². The cover-abundance of all species (vascular plants, bryophytes and lichens) was estimated, and the locality, UTM grid code (GPS), area of the stand, and structural parameters were noted. Altitude, slope and exposition were measured. Other factors like wind protection, water supply, snow conditions and soil moisture were roughly estimated. The analysis of the relevés allows the detection of indicator species and indicator communities for particular altitudes and shows their ecological habitat conditions. Here it should be stressed that all plant species present in a plot should be recorded, because the importance of a particular species as an indicator cannot be foreseen (see also the section below on The Role of Cryptogams ). The second part of the characterization of altitudinal belts was carried out in three mapping areas covering different altitudinal ranges ( , , m a.s.l.). These areas contain all important habitat types and dominant vegetation communities and represent distinct altitudinal vegetation belts that could be distinguished in the field. In these areas detailed vegetation maps, including information about the exposition and inclination of each vegetation stand, were constructed with help of the Global Positioning System (GPS). In each area a transect showing relief and vegetation types at single metre intervals was analysed. Additionally, representative soil profiles for all common vegetation types were described and sampled. In each mapping area, temperature data loggers (HOBO Temp Pro) were installed in four different habitats (northern

4 slope, southern slope, ridge and level ground). These measured the temperature every thirty minutes over a period of six months on the soil surface. The data indicate temperature differences between the three mapping areas, and also between habitats in a particular mapping area. This part of the characterization shows the typical vegetation pattern, the abundance of vegetation types in the different altitudinal belts, and the correlation between vegetation types and habitat conditions. THE ROLE OF CRYPTOGAMS In the Arctic, bryophytes and lichens play an important role in plant communities and ecosystems. The cover and biomass of the cryptogam layer is often higher than of the phanerogams (e.g. Oechel and Sveinbjörnsson, 1978; Ahti and Oksanen, 1990), and the species richness of bryophytes and lichens usually exceeds that of vascular plants in investigated plots. In the present study, for example, the maximum species number of phanerogams per plot was twenty-five species, while for cryptogams it was above sixty. Regularly, more than twice as many cryptogam species as vascular plant species were found in plots of 1 4 m². In some extreme plots 90 per cent of the species were bryophytes and lichens, and only 10 per cent phanerogams. From the Arctic, Lünterbusch and Daniëls (2000, 2004), Bültmann and Daniëls (2000, 2001), and Ahti and Oksanen (1990) also reported extremely high species numbers of cryptogams. These results suggest that biodiversity and vegetation studies in the Arctic should not be undertaken without taking the cryptogams into account. A similar conclusion can be drawn for the alpine zone from studies in the European Alps (e.g. Bültmann, 1992). In general, bryophytes and lichens have proved to be excellent bioindicators for monitoring microhabitat conditions (e.g. Bültmann, 2004), pollution (Frahm, 1998; Geebelen and Hoffmann, 2001; Nimis and Purvis, 2002; Wirth, 1992), and hemeroby (e.g. Tibell, 1992). There is also evidence that they respond to climate change (Frahm and Klaus, 1997; Gignac, 2001; Herk et al., 2002; Nash and Olafsen, 1995). Insarov and Schröter (2002) describe the anticipated effects of climate change on lichens and propose monitoring strategies. For further monitoring techniques and methodological aspects see Dietrich and Scheidegger (1996) and especially the synthesis of Nimis et al. (2002). Bryophytes in particular can have a strong effect on habitat conditions. The ability to maintain soil moisture and to build up an insulating organic layer affect the occurrence and the persistence of permafrost (Press et al., 1998; Longton, 1992). Together with the slow decomposition rates of bryophytes, this can also lead to a long-term accumulation of organic material and thus the site can become a sink of organic carbon (Chapin et al., 1996; Longton, 1992; Tenhunen et al., 1992). As cryptogam species respond individualistically to manipulated climate change (Press et al., 1998), future investigations should be undertaken on the species level rather than on the level of plant functional types. PROPOSAL FOR FUTURE MONITORING ACTIVITIES The detailed description of the present status of altitudinal belts forms the basis for monitoring in the future. The data provided will be helpful in many different ways for detecting changes. Shifts in altitudinal ranges of species and communities can be identified. These changes are expected to occur among the indicators of particular altitudes, and especially among the species

5 and communities which are at their boundaries of distribution in the investigation area (e.g. high arctic plants at their southern boundary) (Callaghan and Jonasson, 1995b). The study of such effects should always be accompanied by the investigation of habitat shifts, because colonization of adjacent changed habitats by migrating plants will probably take place before altitudinal shifts occur (Callaghan and Jonasson, 1995a). Studying only the presence of species regardless of their habitats would therefore not detect any changes at early stages. An example from our study is Salix herbacea, which is present at both medium and high altitudes but in remarkably different habitats in each: at medium altitudes Salix herbacea is restricted to a single special habitat type, whereas it spreads into different habitats at high altitudes. The same can be said, for example, about open ridge vegetation (Carici-Dryadetum), which is restricted to windswept ridges at medium altitudes, but also occurs on southern slopes and plains at high altitudes. It is also expected that the composition of plant communities will change, that current communities will disintegrate, and that new assemblages will be formed (Callaghan and Jonasson, 1995a). A comparison of the original and new community composition can lead to an understanding of the ecological changes which have taken place. Thus the interpretation of the ecological requirements of all species in a community leads to a more precise indication system than the interpretation of habitats by only single species. Changes in ecological conditions will also have an influence on the abundance and distribution of communities. However, it is always delicate to repeat vegetation mapping because problems with the delimitation of communities may occur. It is therefore proposed that the main emphasis should be laid on communities that can easily be mapped due to the strong gradients ruling at their borders (e.g. snowbeds, steppe and open ridge vegetation, fens). Here it should also be mentioned that mapping of only the zonal habitats (predominately influenced by climate) is not suitable for mountain regions because it is difficult to define them. Small differences in exposition and inclination can have strong effects on the microclimates of slopes. Habitats are also influenced by up-slope conditions (e.g. water regimes) and neighbouring mountains (e.g. wind protection, shade). Disregarding the time lag between climate change and the response of vegetation, a shift of an entire altitudinal belt might be expected in the next fifty years if we consider the predicted increase of summer temperature (Hagen et al., 2001) and the probable difference of 2 C between adjacent vegetation belts in our study area (Sieg and Daniëls, 2004). However, it is probable not just that the belts will shift but that the whole appearance of the plant communities and their pattern will be altered. REFERENCES AHTI, T.; OKSANEN, J. Epigeic lichen communities of taiga and tundra regions. Vegetatio, No. 86, 1990, pp BECKER, A.; BUGMAN, H. Global change and mountain regions: the mountain research initiative. Stockholm, IGBP Report 49, 2001, 88 pp. BÖCHER, T.W. Oceanic and continental vegetational complexes in Southwest Greenland. Meddelelser om Grønland, Vol. 148, No. 1, 1954, pp BÜLTMANN, H. Über Artenreichtum und Standort bei Erdflechten in den höheren Lagen der Alpen. Diploma thesis, Institute of Plant Ecology, Münster, 1992, 82 pp., unpubl.

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7 HERK, C.M.; APTROOT, A.; DOBBEN, M.F. VAN. Long-term monitoring in the Netherlands suggests that lichens respond to global warming. Lichenologist, Vol. 34, No. 2, 2002, pp INSAROV, G.; SCHRÖTER, B. Lichen monitoring and climate change. In: P.L. Nimis, C. Scheidegger and P.A. Wolseley (eds.), Monitoring with lichens: monitoring lichens. NATO Science series IV. Earth and Environmental Sciences 7, pp Dordrecht, Kluwer, LONGTON, R.E. The role of bryophytes and lichens in terrestrial ecosystems. In: J.W. Bates and A.M. Farmer (eds.), Bryophytes and lichens in a changing environment, pp Oxford, Clarendon, LÜNTERBUSCH, C.; DANIËLS, F.J.A. Vergesellschaftung und Biodiversität der Dryas integrifolia-vegetation in Nordwestgrönland. Berichte der Reinhold Tüxen-Gesellschaft, No. 12, 2000, pp LÜNTERBUSCH, C.; DANIËLS, F.J.A. Phytosociological aspects of Dryas integrifolia vegetation on moist-wet soil in Northwest Greenland. Phytocoenologia, Vol. 34, No. 2, 2004, in print. MAXWELL, B. Arctic climate: potential for change under global warming. In: F.S. Chapin III, R.L. Jefferies, J.F. Reynolds, G.R. Shaver and J. Svoboda (eds.), Arctic ecosystems in a changing climate: an ecophysiological perspective, pp London, Academic Press, MESHINEV, T.; APOSTOLOVA, I.; KOLEVA, E. Influence of warming on timberline rising: a case study of Pinus peuce Griseb. in Bulgaria. Phytocoenologia, Vol. 30, No. 3 4, 2000, pp NASH, T.H.; OLAFSEN, A.G. Climate change and ecophysiological response of Arctic lichens. Lichenologist, Vol. 27, No. 6, 1995, pp NIMIS, P.L.; PURVIS, O.W. Monitoring lichens as indicators of pollution. In: P.L. Nimis, C. Scheidegger and P.A. Wolseley (eds.), Monitoring with lichens: monitoring lichens. NATO Science series IV. Earth and Environmental Sciences 7, pp. 7 10, Dordrecht, Kluwer, NIMIS, P.L.; SCHEIDEGGER, C.; WOLSELEY, P.A. (eds.) Monitoring with lichens: monitoring lichens. NATO Science series IV. Earth and Environmental Sciences 7. Dordrecht, Kluwer, 2002, 408 pp. OECHEL, W.C.; HASTINGS, S.J.; VOURLITIS, G.; JENKINGS, M.; RIECHERS, G.; GRULKE, N. Recent change of Arctic tundra from a net carbon dioxide sink to a source. Nature, No. 361, 1993, pp OECHEL, W.C.; SVEINBJÖRNSSON, B. Primary production processes in arctic bryophytes at Barrow, Alaska. In: L.L. Tieszen (ed.), Vegetation and production ecology of an Alaskan arctic tundra, pp New York, Springer, 1978 (Ecological Studies, No. 29). PRESS, M. C.; J.A. POTTER; M.J.W. BURKE; T.V. CALLAGHAN; LEE, J.A. Responses of a subarctic dwarf shrub heath community to simulated environmental change. Journal of Ecology, No. 86, 1998, pp SIEG, B.; DANIËLS, F.J.A. Altitudinal zonation of vegetation in continental West Greenland with special reference to snowbeds. Phytocoenologia, 2004, submitted. SMITH, T. M.; SHUGART, H.H. The transient response of terrestrial carbon storage to a perturbed climate. Nature, No. 361, 1993, pp TENHUNEN, J.D.; LANGE, O.L.; HAHN, S.; SIEGWOLF, R.; OBERBAUER, S.F. The Ecosystem role of poikilohydric tundra plants. In: F.S. Chapin III, R.L. Jefferies, J.F. Reynolds, G.R. Shaver and J. Svoboda (eds.), Arctic ecosystems in a changing climate: an ecophysiological perspective, pp London, Academic Press, THANNHEISER, D.; MÖLLER, I.; WÜTHRICH, C. Eine Fallstudie über die Vegetationsverhältnisse, den Kohlenstoffhaushalt und mögliche Auswirkungen klimatischer Veränderungen in Westspitzbergen. Verhandlungen der Gesellschaft für Ökologie, No. 28, 1998, pp TIBELL, L. Crustose lichens as indicators of forest continuity in boreal coniferous forests. Nordic Journal of Botany, Vol. 12, No. 4, 1992, pp WESTHOFF, V.; VAN DER MAAREL, E. The Braun-Blanquet approach. In: R.H. Whittaker (ed.): Ordination and Classification of Communities, pp The Hague, Junk, WIRTH, V. Zeigerwerte von Flechten. Scripta Geobotanica, No. 18, 1992, pp

Global Change and Arctic Terrestrial Ecosystems

Walter C. Oechel Terry Callaghan Tagir Gilmanov Jarle I. Holten Barrie Maxwell Ulf Molau Bjartmar Sveinbjomsson Editors Global Change and Arctic Terrestrial Ecosystems With 132 Illustrations Springer Preface