Here I present results from three field studies and one manipulative experiment that explored some of the factors that may influence belowground communities at multiple spatial scales. In the first field study I found that the abundance of two groups of soil mites was positively related to soil pore volume in two contrasting habitats. Hence, by limiting abundance, soil pore volume could indirectly influence species richness of mites. In another field study, using a spatial design, I found that the variation in community composition of soil mites and microbes within habitats was related to the variation in soil properties and plant community composition. However, the relative influence of these factors depended on the degree to which they varied within a habitat. Similarly, using a multi-site field study I found that soil properties, plant community composition and also precipitation influenced the composition of the microbial and mite communities within the landscape. This study also showed that the species richness of soil mites within a site was related to the degree of variation in soil properties and vegetation within the site. Finally, a manipulative field experiment showed that species richness of soil fauna was related to small-scale heterogeneity in soil physical properties, and that both the abundance and composition of belowground communities was related to the organic horizon thickness. Overall, my work shows a general positive relationship between species richness of soil biota and heterogeneity across spatial scales, and that the composition of belowground communities is related to the variation in soil properties, plant community composition and climate.

Typescript (photocopy) / xii, 149 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--Dept. of Soil Science, University of Adelaide, 1982