How will European Arctic ecosystems respond to projected global environmental change?

A high arctic polar semidesert and a subarctic dwarf-shrub heath were subjected to increases in the concentration of nutrients, elevated temperatures and greater summer precipitation over five growing seasons. The aim of the study was to determine the sensitivity and resilience of the two contrasting European arctic ecosystems to components of projected global environmental change. Both ecosystems were sensitive to environmental change, with nutrient eliciting the greatest responses, followed by temperature, and then water, which exerted little measurable influence. The direction, magnitude and timing of responses differed markedly between ecosystems and species responded individualistically. Some of the observed responses were similar to those from parallel studies in Alaskan wet tussock tundra and other European subarctic communities, but underlying mechanisms may not always be the same. Community level changes at the subarctic dwarf-shrub heath were mediated through the responses of a few key species which were already present in the community, whilst at the high Arctic polar semidesert, responses were determined by both existing and invading species. Responses of arctic plants and communities to nutrient enrichment and temperature are greater than those reported in response to elevated CO, or enhanced fluxes of UV-B radiation, although interactions between variables may be important in determining responses to current environmental change scenarios.