Arctic plant ecology: From tundra to polar desert in Svalbard - Unis

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It is expected that northward expansion of southern species dominating in the Low Arctic, could cause problems to high arctic species with low competitive abilities. However, retreating glaciers may provide new habitats in which the high arctic species may colonise and persist during periods of warmer climate . The ability to colonise newly deglaciated terrain varies among species (Matthews 1992). In project 3 we studied glacial succession patterns in the three bioclimatic zones to identify high arctic species that are not represented in up to 100 years old successional stages and therefore might be at risk of extinction in a warmer climate. Low temperatures during a short growing season reduce soil nutrient availability. Since low temperature and low nutrient availability may interact, it is difficult to distinguish the impact of each of these variables (Körner 2003). Counterintuitively, leaves from plants from extremely cold climates had been found to be richer in macronutients (N, P) than plants from warmer environments, which had been explained as 'luxurious consumption' (Körner 1989). Locally, the input of nutrient can be high in Svalbard due to birds or mammals. Especially high levels of nutrients are found under bird cliffs. The aim of study 4 was to test whether temperature per se controls plant growth or whether growth is constrained by temperatureinduced nutrient shortage. In cold climates, plants are generally smaller than in warm climates, and as life conditions become more adverse miniaturization of plants progresses. Are the vegetative and reproductive structures similarly affected (isometric allocation), or do plants give priority to one of the two (asymmetric allocation), which would hint at selective pressure (evolutionary adaptation)? In alpine environments it has been found that the allocation of resources shifts towards the reproductive structures as altitudes increases (Fabbro & Körner 2003). In study 5, we explore this for the first time in the Arctic. Climate change is not only expected to result in warmer conditions in the arctic, but also more extreme weather. This may even include more frequent or more intense freezing events during the growing period due to changed atmospheric circulation, despite overall (mean) warming. Freezing resistance is the first and most fundamental environmental filter plant species have to pass to establish sustainable growth in the Arctic. However, even arctic plants are susceptible to freezing when they are active, i.e. during the growing season. Tissues of arctic and alpine plants may tolerate almost any temperature (some even liquid nitrogen) when they are dormant, but might be killed by temperatures between 2 and 9 °C, when actively growing and flowering. Hence, it is well established that extreme summer events are the critical issue to look at (for a review see Körner 2003). During the course, we tested the freezing resistance of 12 species. Material and methods Thirteen students from Norway, Sweden and Germany, studying at nine different institutions, participated in the course. The students worked in groups of two or three. All students participated in data collection for all projects, whereas each group was responsible for study design, analysing and writing about their study. Data were collected during a seven days cruise with M/S Stockholm. We visited 10 different 4
localities in western and northern Svalbard. We visited one bird cliff and one glacier foreland in each bioclimatic zone as well as sites with vegetation typical for each zone. Two to six sites were visited within each of the ten localities, and a total of 88 plots were analysed among sites. The plots were randomly chosen for unbiased application of plot sampling. The point intercept method was used to record the vascular species within each plot (Bråthen & Hagberg 2004). At each site, 50 cm x 50 cm quadrats with 25 points of equal intercepts of 10 cm were used. In most cases three replicates were analysed per sites but sometimes two or four replicates were recorded depending on time and heterogeneity of the vegetation. Additional species in the plot were also recorded. The percentage cover of vascular plants, bryophytes, lichens, bare ground/rocks, and cryptogram crust was estimated for each plot. The following environmental factors were recorded at each plot: soil temperature, soil moisture, soil pH, exposure, slope angle, bioclimatic zones, and productivity. Species list for each site were compiled. These data were shared among project 1 (all sites except the glacier forelands), 2 (all sites) and 3 (only glacier foreland sites). To explore whether high nutrient input could compensate for low temperatures, and to find out how plants allocate resources into growth and reproduction, biometric plant traits were collected for as many species as possible. Data were collected from 18 species below bird cliffs and in areas with no additional nutrients input. For the reproduction project, data were collected for a total of 37 species: 17 species in bioclimatic zone A, 19 species in bioclimatic zone B and 23 species in bioclimatic zone C. Aboveground plant height, longest leaf length (without petiole) or width (if the width was larger than the length), and largest blossom diameter (or length of the whole inflorescence for graminoids) were measured. At least three samples of each herbaceous species were harvested. In addition, 18 samples of aboveground biomass was harvested in representative full cover 10 x 10 cm plots, dried and weighed. For the cold resistance test, at least five mature leaves and five nonsenescent, fully open inflorescences of 12 species were collected for each of the following treatments: a cool room at +5 °C (control), a freezer set at 18 °C (guaranteed freezing damage) and a freezer set to the expected critical range of 7 °C. Damage was visually inspected. The students had ten days for analysing all data and writing their reports. Some modifications were made on the reports after the course. Results and discussion Species diversity, on a landscape as well as at a more local scale, tended to decrease from bioclimatic zone C to A (Antonsson, Jørgensen and Tange). This can be explained by a decrease in vegetation cover from bioclimatic zones C to A, as supported by ANOVA analyses showing significant relations between species density and the proportion of bare ground to plant cover. In addition, fewer plants are adapted to the harsh conditions present there (Körner 2003, PAF 2007). This decrease, though not significant, agrees with previous studies from Svalbard (Marteinsdòttir & Arnesen 2006) and the Arctic (Young 1971, Walker 1995). The relation between species diversity and the other environmental factors was less clear. 5
Page 1 and 2: Arctic plant ecology: From tundra t
Page 3: Arctic plant ecology: From tundra t
Page 7 and 8: seamed to decrease from zone C to A
Page 9: Raup, H. M. 1965: The flowering pla
Page 12 and 13: them supporting his theory (e.g., H
Page 14 and 15: Site ID Table 1. Sites analysed in
Page 16 and 17: Table 2. Kendall’s τ correlation
Page 18 and 19: The RDA ordination (Fig. 4) showed
Page 20 and 21: al. (2007) found that at low temper
Page 22 and 23: Franzèn, D. & Molau, U. 1999: Vasc
Page 24 and 25: Tilman, D. 1982: Resource Competiti
Page 26 and 27: Juncus biglumis L. Luzula confusa L
Page 28 and 29: Puccinellia phryganodes (Trin.) Scr
Page 30 and 31: #Saxifraga nivalis L. *Saxifraga op
Page 32 and 33: *Coptidium lapponicum (L.) Tzvelev
Page 34 and 35: esponse curve. With rising temperat
Page 36 and 37: N Biscayarhuken Florabukta Reinsdyr
Page 38 and 39: of cold summers can be terminal for
Page 40 and 41: Results Ecological amplitudes of va
Page 42 and 43: A potential substrate area could be
Page 44 and 45: no. of districts 30 25 20 15 10 5 0
Page 46 and 47: tetragona, Erigeron humilis, Minuar
Page 48 and 49: with the species occurring on Svalb
Page 50 and 51: and substrate map show a clear occu
Page 52 and 53: Alsos, I. G. 2007: Frequent LongD
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Walker, M., Wahren, C., Hollister,
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northern hemisphere (Brochmann et a
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an enclave of bioclimatic zone C wi
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Table 3. Formulas of the different
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Figure 2. a: Cumulative number of s
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Figure 4. Presence and absence of a
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(2003), from which a highly signifi
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The intermediate stages seem to hav
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Svalbard in general. Moreover polyp
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Svoboda, J., Henry, G. H. R. 1987:
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limited by nutrient availability ra
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flower. Care was taken to measure o
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Biomass Biomass per unit land area
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Luzula nivalis Juncus biglumis Drya
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References Arft, A. M., Walker, M.
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partly lose their high altitude/lat
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preferably grow in rosettes, which
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Forbs Graminoid Graminoids In grami
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latitude plants on Svalbard to keep
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Elvebakk A. 1999: Bioclimatic delim
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a climate description see Rønning
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Results and Discussion The minimum
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Table 2. Ranking of examined plant
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References Biebl, R. 1968: Über W
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Arctic plant ecology: From tundra to polar desert in Svalbard - Unis

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