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

The temperature measurements at 10 cm soil depth in the plots with E. wettsteinii
showed a higher temperature (~0.5­1 °C) in comparison to the plots without E.
wettsteinii, however, the t­test showed no significance.
One patch of E. wettsteinii was found at Colesdalen in 1998 and nine patches were
discovered in 2002 (Alsos & Lund 1999, Alsos et al. 2004). This increase in patches
correlates with the temperature diagram which shows a peak in 1998 and one in 2002
due to increased summer temperature. By July 2007 the nine patches had spread to
one big continuous patch. Is the spread of E. wettsteinii in Colesdalen a consequence
of increased mean summer temperature on Svalbard? It is worth noting on the
mountain Sandalsnuten at Finse in Norway, growth and seed production of E.
wettsteinii were largely temperature dependent (Nyléhn & Totland 1999). However,
the effect of temperature on the spread of E. wettsteinii must be indirect due to
increased growth and quality of the host plant caused by elevated temperature. As a
consequence, the population of E. wettsteinii could actually decrease due to increased
competition if we assume that a warmer climate leads to a denser vegetation cover.
However, temperatures on Svalbard may have to rise substantially before this process
will take effect. Increased temperatures and changes in species composition can lead
to disappearance of some of the host species of E. wettsteinii and introduction of new
species. Due to the broad host range of E. wettsteinii one can assume that this might
not influence the ability to have proper species in the surroundings to parasitise
(Nyléhn & Totland 1999, Seel & Press 1993).
Dense patches of E. wettsteinii in Colesdalen were observed near bare ground mainly
caused by frost disturbance. Open soil patches are needed for seed establishment
(Molau 1993, Seel & Press 1993). Long­term consequences of climatic changes may
lead to less frost disturbance and, consequently, fewer open soil patches. The resulting
dense vegetation cover may limit the growth of E. wettsteinii in some places.
The thermophilic annual E. wettsteinii has not only the potential to spread when mean
July temperatures are rising by 1 degree Kelvin, this being the temperature increase
being observed for the last ten years, but is already expanding its habitat.
Conclusion
Species on Svalbard and Greenland possess the same ecological amplitudes,
regardless of their occurrence in the Low or High Arctic. Widespread species on
Svalbard do not necessarily possess wide ecological amplitudes and widespread plants
do not naturally display wide ecological amplitudes. These conclusions may be of
major interest when considering species responses to climate change. A variety of
arctic species may have ecological amplitudes large enough to accommodate for
climate change. A population of the thermophilic annual Euphrasia wettsteinii seems
to be spreading, perhaps due to rising temperatures on Svalbard, thereby indicating
early signs of climate change in the Arctic.
References
ACIA. 2006: Arctic Climate Impact Assessment: Scientific Report Cambridge.
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