Role of nematodes in the biological processes of the soil

Abstract

Abstract Nematodes are a quantitatively significant component of the soil microfauna: the number of individuals per m2 is measured in millions. They belong to the trophic level of the consumers, but they influence the processes of degradation and mineralization of organic matter, mostly due to the trophic relations which they establish with fungi and bacteria. The species that feed on fungi are represented by nematodes which are furnished with a buccal stylet and, in particular, by Tylenchida. Their role in the decomposition process of litter is essentially that of rendering the nutrients contained in fungi accessible to other organisms such as bacteria. In some cases they disseminate the spores of fungi. The nematode species that feed on bacteria have no buccal stylet. Their role consists in maintaining the demographic equilibrium in the bacterial population and in favouring the spreading and the proliferation of certain species. Nematodes constitute a small fraction in terms of biomass and respiration as compared to the total mass of soil organisms but their action appears significant when compared with that of other animals. Their mechanical action has no effect, yet it has been shown that they play a remarkable role in the production of CO2 in the soil and therefore in the decomposition of organic matter, probably due to their relation with fungi and bacteria.