Population responses of oribatid mites and collembolans after drought

To compare the effects of a drought disturbance on species of Oribatida and Collembola, and subsequent recovery of their populations after the drought, we examined a Norway spruce, Picea abies, stand in south-western Sweden, where 6 years of experimentally induced summer droughts had resulted in major changes in the soil faunal communities. We followed the population densities during a 4-year period and sought correlations between the species' drought responses and their ecological characteristics. Data on depth preference, habitat choice and reproductive mode were collected from the literature. Surface-living species, which tended to have narrow habitat width, were less negatively affected by the drought. However, among species showing negative population responses to drought, species with large habitat widths tended to recover faster after the drought. Furthermore, parthenogenesis was more common among the oribatid species that showed a population recovery than among those that did not. Overall, collembolan species recovered faster than oribatids, and among the species that did not recover, Oribatida were over-represented. No general differences in characteristics between oribatids and collembolans were observed that could explain their different responses. Possibly, traits other than those examined were more important, such as differences in dispersal rates between the two groups.