LITTER COMPLEXITY AND COMPOSITION ARE DETERMINANTS OF THE DIVERSITY AND SPECIES COMPOSITION OF ORIBATID MITES (ACARI, ORIBATIDA) IN LITTERBAGS

To investigate the relationship between litter complexity and composit ion and the diversity and composition of the oribatid mite fauna inhab iting it, an experiment was carried out at a single forested site in t he mountains of North Carolina, USA. Natural litterfall was excluded f rom a series of 1 m(2) plots and replaced with treatment litters that varied in composition and complexity. Plots of pure birch, maple and o ak Litter comprised the simple litter treatments. Two complex litters were made of a mixture of these three litter species and a mixture of seven litter species. Treatment litters were applied to the plots in t he autumn of 1993 and again in 1994, The oribatid mites extracted from litterbags of the treatment litters from both years are reported on h ere. Mixed litters had a significantly greater variety of microhabitat s, as defined by substrate type and fungal growth form, than did the s imple Litters. Likewise, the oribatid mite species richness in litterb ags of mixed litter was significantly higher than that in the simple l itters. The fauna within replicates of each litter-type were more simi lar to each other than to those of other treatments. A third of the mi te species tested showed a differential response among the simple Litt er-types. These results indicate a link between heterogeneity and dive rsity of mites active in a particular horizon of Litter and some influ ence of litter-type upon species composition. Such patterns in habitat use by adult mites are strong, though not conclusive evidence of the ultimate role of heterogeneity in maintaining the diversity of oribati d mites. (C) 1998 Elsevier Science B.V.