METHODS FOR ASSESSING THE EFFECTS OF BIOTA ON SOIL STRUCTURE

Soil biota participate in the genesis of the habitat wherein they live. Together with climate, topography, parent material, and time, vegetation and soil organisms comprise one of Jenny's five interactive soil-forming factors. Only recently has a conceptual framework for investigating the interrelationships of soil biota with soil structure been outlined. This view of soil emphasizes the hierarchical nature of soil structure, which transcends at least four orders of magnitude. Because of the feedback relationship between biota and the development of soil structure, methods of quantifying soil structure will differ with the question being asked. This review briefly considers various methods that have been used to assess the effects of biota, their by-products, and their activities on soil structure. Included are methods tied to the mechanical separation of aggregates, the quantification of pore space, and the evaluation of soil microenvironments using soil micromorphology techniques. Also discussed are important considerations for the sampling, preparation, and application of generally accepted basic methods for quantifying aggregate size distributions and stability. Lastly, a demonstration is presented of how a conceptual framework can be coupled with the use of path-analysis techniques to provide a means for determining the relative importance of various biotic factors in the development of soil structure.