Simulated climate change affecting microorganisms,nematode density and biodiversity in subarctic soils

Arctic terrestrial ecosystems are strongly dominated by temperature, and global warming is expected to have a particularly strong impact in high latitudes. The Arctic will therefore be an important region for early detection of global change. In the present study the effects of environmental manipulations simulating climate change on soil microorganisms and nematode populations were investigated. Study sites were a dwarf shrub dominated tree-line heath (450 m a.s.l.) and a high altitude fellfield (1150 m a.s.l.) at Abisko, Swedish Lapland. Soil temperature was enhanced by using passive greenhouses and the impact on soil organisms with and without NPK fertilizer addition was assessed. The nematode community was strongly affected by warming and nutrient application. Population density was twice as high for all treatments at the fellfield as compared to controls. At the heath temperature enhancement with or without fertilizer application also led to a doubling of the population density, whereas fertilization alone caused an increase of about one third. The environmental manipulations resulted in a greater microbial biomass C and active fungal biomass in the heath soil. Increased density was also recorded for bacterial and fungal feeding nematodes at both sites. The results suggest that nematodes have an important impact on microbial biomass and turnover rates in the two subarctic systems. Elevated soil temperature apparently will lead to increased grazing on microorganisms, contributing to enhanced net N and P mineralization rates and plant nutrient availability. However, biodiversity was generally affected negatively by the environmental manipulations. The effects were more severe at the high altitude fellfield indicating that the influence of elevated temperature will be more pronounced in systems already stressed by extreme climatic conditions. This revised version was published online in June 2006 with corrections to the Cover Date.