ABSTRACT
Soil contains an immense diversity of organisms. Soil type dictates the number and characteristics of the microsites where soil organisms live. The diverse community of soil organisms is dynamic and interacts with both the physical and chemical components of the soil habitat. The role of soil organisms in nutrient cycling is a key biological process in all ecosystems. Soil organisms are major contributors to the aggregation of soil particles. Soil animals, such as earthworms, make significant contributions to soil aggregation by increasing the microbial activity of microorganisms associated with the soil, as well as in the organic matter they ingest. Larger soil animals such as rats, spiders, and earthworms contribute to water penetrability of soils by creating pathways for water to flow. Soil organisms respond variously to disturbances caused by natural events, land management, or land misuse. Soils also contain diverse populations of organisms capable of causing plant diseases. Management of natural ecosystems can also be concerned with maximizing soil biological fertility. The selection of desirable soil organisms is a highly developed technology. Genetically engineered soil organisms appear to be of considerable interest. Various approaches have been taken for identifying indicators of soil biological fertility.
