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

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them supporting his theory (e.g., Huston 1979, Tilman 1982, Taylor 1990). In summary, the majority of theories and hypotheses accentuate intermediate levels of productivity, disturbance, pH and other abiotic factors as yielding the highest levels of species richness. The issue is, however, very complex, and more than 100 hypotheses on variables controlling species richness have been presented throughout the years (Palmer 1994), and variance in species density is often poorly explained by predictor variables (Grace 1999). Although containing a vascular plant flora of about 2000 taxa of vascular plants (Elven et al. 2007), and at least another 1000 taxa of bryophytes and lichens, the arctic flora contains fewer species than ecosystems of lower latitudes (Gaston et al. 1998). Walker (1995) propose that there is a finepored filter of the extreme environmental conditions present in the Arctic, effectively excluding many plant species from establishment in this region. Studies on variation of species richness along abiotic gradients in arctic and alpine communities point out temperature (Young 1971, Rannie 1986, Walker 1995), soil moisture (Gould & Walker 1999, Michalet et al. 2002), soil acidity (Gould & Walker 1999, Gough et al. 2000, Roem & Berendse 2000), productivity (Fox 1992, Jonasson 1992, Theodose & Bowman 1997, Gough et al. 2002, Grytnes 2002, van der Welle et al. 2003, Constanza et al. 2007) as important factors for species richness, and that local conditions play a crucial role (e.g., Gough et al. 2000). Our aim was to investigate the major factors determining vascular plant diversity in different communities along a latitudinal gradient in the High Arctic, expecting a decrease in species richness moving northwards through the bioclimatic zones C, B, and A (CAVM Team 2003). From our general hypothesis, the following predictions were outlined: Biodiversity is correlated with bioclimatic zone, community biovolume (as a substitute for biomass) is correlated with bioclimatic zone and species richness, and species richness is correlated with soil moisture and soil acidity. Material and methods Study sites and data collection Sites were chosen according to latitude, bioclimatic zone (Elvebakk et al. 1999, CAVM team 2003, Elvebakk 2005), vegetation type, and microclimatic conditions along the western and northern coast of Svalbard (Table 1; Figure 1). In our study we included Florabukta as bioclimatic zone A, even though it is in the border between zone A and B. For vegetation analysis three different measures were used for biodiversity; 1.) Species density: noting every vascular plant individual hit when using a needle and point frames (50x50 cm 2 ; 25 points; see Bråthen & Hagberg 2004), 2.) Species richness: noting all vascular plant species found within the frame and 3.) Total species list: noting all vascular plant species found in each site, an area of roughly 300 x 300 m, consisting of the same vegetation type. For each frame the following abiotic factors were measured; slope angle, exposure, organic soil depth, soil temperature, soil moisture, and soil pH. Slope angle was measured with an inclinometer with the precision of 2°; exposure was recorded with a compass, defined as the direction in which the slope was facing; organic soil depth was measured with a ruler after digging a soil profile, soil temperature was measured with a thermometer at approximately 10 cm depth to calibrate for recent and rapid changes. Soil moisture was estimated in the field by digging the fingers in the soil and determining moisture 12
along a scale where 1 = dry, 2 = mesic, and 3 = wet. For soil pH, soil samples were taken in the field and analyzed indoors with a pH meter. Cover was estimated in the field as percentage of the frame, for vascular plants, lichens, bryophytes, cryptogam crust, and bare ground. In addition, mean canopy height of vascular plants was estimated (in centimetres) in the frame. As a substitute for biomass, vascular biovolume was calculated for each site and frame as the canopy height (cm) multiplied by vascular plant cover (%). It has been shown in a study by Lindblad (2007), that vascular plant height was a better measure than biomass to explain vascular plant diversity in a midalpine, SubArctic plant community. Similarly, Gough et al. (2000), found a unimodalshaped correlation of canopy height and species richness and density. This suggests that using biovolume is a measure at least as good as biomass. Lady Franklinfjorden Biscayarhuken Florabukta Reinsdyrflya Mayerbreen Fjortende julibreen Ossian Sarsfjellet Colesdalen Kapp Thordsen Figure 1. Sites included in this study. At each site, at least three replicate frame analyses were made (Table 1). For some of the measures (cover and soil moisture), subjective estimations were used. This was carried out by a large group of people taking turns and the preceding calibration of methods may have been insufficient to make sure that everybody carried out measurements in the exact same way. This should be kept in mind when interpreting the data. 13
Page 1 and 2: Arctic plant ecology: From tundra t
Page 3 and 4: Arctic plant ecology: From tundra t
Page 5 and 6: localities in western and northern
Page 7 and 8: seamed to decrease from zone C to A
Page 9: Raup, H. M. 1965: The flowering pla
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
Page 54 and 55: Walker, M., Wahren, C., Hollister,
Page 56 and 57: northern hemisphere (Brochmann et a
Page 58 and 59: an enclave of bioclimatic zone C wi
Page 60 and 61: Table 3. Formulas of the different
Page 62 and 63:
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
Page 98 and 99:
Table 2. Ranking of examined plant
Page 100:
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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