Long-Term observations of soil mesofauna

General problems connected with planning, sampling, and data processing of long-term research of soil mesofauna are discussed, based on two case studies: (i) the Bremen study of predatory mites (Gamasina) covering 20 years of secondary succession on a ruderal site in northern Germany and (ii) the Mazsalaca study of the effects of climate warming on Collembola of coniferous stands in the North Vidzeme Biosphere Reserve, Latvia, covering 11 years. The findings from both sites are embedded in an array of environmental data. The results from Bremen document the asynchrony of different biota in successional dynamics. The long-lasting increase of the species numbers of soil predatory mites (Gamasina) is contrasted by a decrease in plant species numbers. In the Baltic forests, climate change is indicated by the dynamics of collembolan community. Gradual decline in species richness has been observed from 1992 to 2002 attributed to global warming. The 'temporal window' or time unit to discern changes in soil mesofauna communities seems to span approx. 5 years, highlighting the necessity of long-term observations.