Summary1. The effects of experimental long-term summer drought and irrigation on soil fauna were studied in a Norway spruce stand in south-western Sweden. The treatments, carried out over 8 and 10 years respectively, were chosen to simulate two scenarios of climate change, involving drier and wetter summers. 2. Different microarthropod communities developed in the different treatments. The abundances of enchytraeids, mesostigmatid mites and macroarthropod predators were all lowest in the drought plots. Drought decreased and irrigation increased the abundance and diversity of Oribatida. Drought decreased the abundance of Collembola. 3. The dominance structure of Oribatida and Collembola also changed, but less markedly. Drought affected community composition of both groups more than irrigation. 4. The study confirms that soil microarthropods can be useful environmental indicators, but their responses did not support the widely held view that deviations from a lognormal dominance structure indicates a stressed community. 5. The results also indicate that a drier climate with summer drought will lead to the local extinction of some soil animal species in this region.

No abstract

J. 2006. Recovery of forest soil fauna diversity and composition after repeated summer droughts. Á Oikos 114: 496 Á506.To examine the resilience of soil animal communities to large-scale disturbances. we studied the recovery of total abundance, diversity and community composition of forest soil mesofauna after a 6-year climatic disturbance. This was done in a pre-established experiment in a Norway spruce Picea abies stand in southern Sweden in which longterm summer droughts had been experimentally imposed and had caused large changes in soil fauna communities. We included both predators (mesostigmatid mites) and fungivores/detritivores (oribatid mites, collembolans) in the study because of the likelihood that they would differ in recovery ability due to differences in their feeding habits, dispersal ability and reproductive strategies. Total abundances of Collembola, Oribatida and Mesostigmata were similar in recovery and control plots after three years, but species richness, the Shannon-Wiener diversity index, and community composition recovered more slowly, particularly among the Oribatida. To only use total abundance of higher taxonomic groups was thus not sufficient when measuring community recovery. There was a tendency for more mobile groups to recover faster than the slow-moving oribatids, indicating the importance of dispersal ability for the resilience of soil communities.

No abstract

No abstract