TEMPORAL PREDICTABILITY IN FOREST SOIL COMMUNITIES

1. The predictability (specifically, constancy) of soil fauna communities in temperate forests were analysed using data on the relative abundances of species and higher taxa, respectively, gathered from the literature. As the measure of community predictability Kendall's coefficient of concordance, W, was used. The data derive from 67 studies or plots, spanning a maximum of 23 years. 2. Predictability of forest soil communities was generally high, but species within organism groups had a lower mean W-value (0.80) than organism groups (0.89). In the complete data set, there were no significant relations between predictability and the number of taxa or the duration of studies. 3. In single studies of species within organism groups, predictability tended to decrease over time. Also within single studies, predictability varied when rarer species were successively deleted, but no consistent trend in any direction was evident. 4. Mean predictability of species' relative abundances did not differ significantly between collembola, coleoptera, mites, myriapods and molluscs, nor was it related to an index of the body size of the organism groups. However, predictability of higher taxa decreased with mean body size of the organism groups under study. 5. Predictability of higher taxa was higher in coniferous than in deciduous forests. This may be associated with differences in the size structure of the fauna between the habitats, coniferous forests having fewer groups of macrofauna which have lower and more equal densities. Predictability of species within organism groups did not differ between forest types. 6. Possible mechanisms behind the high degree of predictability in temperate forest soil fauna communities are briefly discussed, but the detailed studies of population dynamics, species interactions and food web structure needed to resolve this issue are lacking.