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

different among the three bioclimatic zones; 2) mean species richness per site is not
significantly different among zones; and 3) species density is different among zones.
Important when discussing biodiversity is the scale on which investigation is made.
Comparing biodiversity among sites is only possible when using the same scale. All
three of our measures of biodiversity are records of α­diversity, defined as the
diversity within a stand or community. To make a meaningful comparison between
regions, it is important to operate on the same scale.
The total species list showed an increase in numbers when moving from bioclimatic
zone A to C. This trend, though not significant in our study, is in line with previous
studies from Svalbard (Marteinsdòttir & Arnesen 2006) and the Arctic in general
(Young 1971, Walker 1995). This is a measure of the diversity at landscape level,
including several sites with different vegetation types. Comparing our data with the
database for vascular plants found on Svalbard (Svalbarddatabasen), there is a total of
110 vascular plants recorded from Colesdalen, situated in bioclimatic zone C, while
Gustav V Land (zone A) has a record of 85 species, although the area is significantly
larger. See also Table 4 for comparison with other arctic areas.
On a smaller scale, when looking at mean species richness per site, there is no
significant difference between sites in different regions in our study. Most sites
contain between 17 and 27 species, which is correlating very well with a study from
the Canadian Arctic by Franzen & Molau (1999). They found no trends of changes in
species richness when going from latitude 62° to 78°. In our study, covering a large
gradient, we visited a restricted number of different vegetation types, and hence could
not capture the full plant diversity of every site. In the field the plots were chosen to
cover one particular kind of habitat (vegetation type) in each site.
Species density (mean per site) is increasing when going from zone A to C (Table 2,
Figure 2). This can be explained by more scattered vegetation in bioclimatic zones A
and B compared to C (Table 2), as supported by ANOVA analyses showing significant
relations between species density and bare ground, as well as the fact that fewer plants
are adapted to the harsh conditions present there (Körner 2003).
Our results largely supported our first prediction, that biodiversity is correlated with
bioclimatic zone and highlight the importance of scale when discussing biodiversity,
as shown in the discussion above. From our results, and also when comparing with
Franzen & Molau (1999), it seems likely that most vegetation types in the Arctic
contain roughly the same number of species, but differences among regions remain on
a larger scale (among bioclimatic zones), due to the degree of landscape heterogeneity
and the number of different habitats available for plant species (see Table 4).
The first part of our second prediction, concerning community biovolume and
bioclimatic zone also gained support from our data. We found community biovolume
to decrease with bioclimatic zone, but increased biovolume did not significantly relate
to any measure of biodiversity. This is consistent with the work of van der Welle et al.
(2003), and Gough & al. (2000), which showed no correlation of biodiversity and
productivity in the Arctic. On the other hand, a large number of studies support the
view of a ‘hump back’ relationship of productivity and species richness in alpine and
arctic areas (Grytnes 2002, Theodose & Bowman 1997, Jonasson 1992). Constanza et
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