The Role of Soil Invertebrates in Turnover of Organic Matter and Nutrients

Abstract

Substantial proportions of organic substances which originate in plants or animals eventually reach the soil,where they may remain for only a few hours or days if they are readily decomposable, or as long as several decades if they decay slowly. The plant material ranges from bacteria, fungal hyphae and soft leaf tissue to tough woody substances. Animal materials range from single-celled protozoa, nematodes, soft-bodied worms and insect larvae through arthropods with tough exoskeletons to large vertebrate animals and excreta.\rPlants ans small animals with soft tissues usually are decomposed by soil microflora alone, byt tougher ane more chemically stable tissues usually are broken down by a complex series of events involving both soil fauna and microflora. Some tissues decompose at the soil surface and their products leach into the soil, or raw organic matter may be incorporated directly into the soil and decay there.\rSoil animals contribute to the breakdown of organic matter in several ways:\r1. they disintegrate plant and animal tissues and make them more easily invaded by microorganisms;\r2. they selectiveely decompose and chemically change parts of organic residues;\r3. they transform plant residues into humic substances;\r4. they increas the surface area available for bacterial and fungal action;\r5. they form complex aggregates of organic matter with the mineral part of soil; and\r6. they mix the organic matter thoroughly into the upper layers of soil.