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

The percentage area of different substrate types of Svalbard was estimated by means
of the preliminary substrate map of Svalbard (Arnesen, personal communication)
using GIPM Version 2.2.1.1. The pixels of each substrate category were counted and
expressed as percentage area in relation to the pixel sum of entire Svalbard. The
dominant substrate type is weakly acidic and covers 14.1% of entire Svalbard. Acidic
substrates cover 6.1%, followed by the alkaline circumneutral type with 5.4%. The
remaining substrate consists of sediments (3.6%), saline steppe substrate (0.1%) and
undefined substrate (0.2%). Svalbard is dominated by glaciers occupying 67.5% of
the surface area.
Meteorological data
Data from the meteorological station at Svalbard Airport (MET 2007) were used to
calculate the increase in mean summer temperatures for the last ten years (1997­
2007). Figure 2 shows a simplified model of the temperature data using a linear
regression. In the period 1997­2007 mean summer temperatures increased with a rate
of 0.16 K per year. As a comparison the mean summer temperature of the last normal
period (1961­1990) is included in the diagram.
Degrees Celsius
7
6
5
4
3
2
1
0
1997
1998
Mean summer temperature at Svalbard Airport
1999
2000
2001
2002
2003
2004
37
2005
2006
2007
Mean temperatures
Regression model
Mean summer temperature
1961­1990
Figure 2. Mean summer (June, July and august) temperature at Svalbard airport (R 2 = 0.52).
Study species
The annual thermophilic Euphrasia wettsteinii G.Gusarova belongs to the family
Scrophulariaceae. The species was earlier treated as E. frigida Pugsley (PAF 2007).
Euphrasia wettsteinii is a root hemiparasite, but it is still unclear which hosts the
Svalbard­populations are parasitising (Alsos et al. 2004). Some hemiparasites are
reported with only one host. However, E. wettsteinii is found physically connected to
a variety of hosts or it may grow unconnected to a host (Seel & Press 1993).
Euphrasia wettsteinii is mainly self­pollinating. The plants are found in closed plant
communites, therefore openings in the cover are needed to expose the soil and provide
a seed bed. Some disturbance which causes small open patches in the growth sites is
needed for establishment of the seeds (Molau 1993, Seel & Press 1993). Reproducing
by seeds may be of advantage to survive unfavourable winter times, but a long series