The soil microflora and fauna complement each other in the comminution of litter, mineralization of essential plant nutrients, and conservation of these nutrients within the soil system. Harvesting directly affects these processes through the reduction and redistribution of organic matter, compaction, changes in plant cover, and modification of microclimate, all of which affect the distribution, composition and activity of the soil biological communities. However, all practices generally affect soil organisms over the short term. Changes over the longer-term are less obvious because of gradual recovery of most biological components with canopy closure. Long-term impacts are more difficult to interpret because these are often influenced by natural changes in population dynamics of soil organisms with forest succession, drought, and the invasion of exotic species.
Responses are complex, with various groups being affected differently.
Even within a taxon, individual species may behave differently. Although the relationships among floral composition, faunal diversity and sustained soil fertility are not always clear, there are indications that a simplified soil biological system will adversely affect nutrient cycling, tree growth, and forest health. Decomposition rate is generally positively correlated with faunal biomass, and a diverse fauna is required for interacting with microorganisms to enhance microbial diversity. Also, feeding on microflora by the fauna concurrently controls certain plant pathogens. Destruction of mycorrhizae, essential for the establishment of coniferous seedlings, can lead to serious reforestation problems.