Spatial Distribution of Soil Animals
Soil animals are not uniformly distributed in soil. Unlike the soil microflora, which could be considered ubiquitous, the proliferation of soil animal communities is more sensitive to environmental disturbances and ecological interactions. Gross climatic differences afford opportunities for unique assemblages of organisms. Even within a specific climatic region, large differences occur in the community of organisms present based upon type of vegetation, soil, availability of water, land use, and presence of xenobiotics. Within the confines of a seemingly uniform pedon, “hot spots” of soil organism activity can be isolated based on localized availability of resources and environmental conditions (Figure 23.3).
Influence of Soil Animals on Soil Functions
Decomposition and Nutrient Cycling
Soil animals work directly and indirectly with the soil microflora (i.e., bacteria, actinomycetes, fungi, and algae) to decompose organic matter and mineralize nutrients.И The primary consumers of organic materials are the soil microflora. Soil animals, like many of the microflora, are heterotrophs and therefore consume organic materials to gain energy for growth and activity. Soil animals make important contributions to decomposition by
FIGURE 23.3 Key locations of soil organism activity. Source: From Beare et а1Я
- 1. shredding organic materials, thereby exposing a greater surface area for enhancing the activities of other organisms, especially microorganisms;
- 2. consuming resistant plant materials that would decompose slowly otherwise, such as wood, roots, and dung, and transforming these materials into more decomposable constituents;
- 3. dispersing soil microorganisms (i.e., inoculation) within the soil profile by transporting them on their bodies and through their intestinal tracts;
- 4. creating burrows in soil to increase aeration, which stimulates microbial activity;
- 5. transporting organic materials from the soil surface to deeper in the soil profile, thereby improving environmental conditions for decomposition and increasing biological interactions deeper in the soil profile;
- 6. consuming bacteria and fungi, thereby releasing nutrients and stimulating the regeneration of microbial populations; and
- 7. providing unique food sources themselves for consumption by other soil fauna and microflora.