DECOMPOSITION AND NITROGEN MINERALIZATION IN NATURAL AND AGROECOSYSTEMS - THE CONTRIBUTION OF SOIL ANIMALS

The present article centres on the contribution of soil animals to organic matter decomposition and nitrogen mineralization in natural and agro-ecosystems. Criteria are presented for the categorisation of the soil fauna in functional groups in order to be able to quantify the contribution of the soil fauna. Three types of classifications: size, habitat and food, are discussed. For various natural ecosystems, such as prairies and forests, and for agro-ecosystems a rather similar outcome of the faunal contribution to nitrogen mobilization of approximately 30% appears to exist. This value is dependent on various types of interactions among functional groups, changes in population density of microorganisms and soil fauna, seasonally changing abiotic factors and management, such as fertilization, harvesting and addition of harvest residues to the soil. Finally, to improve management of ecosystems as related to soil faunal activity in decomposition, lines are set out for further research such as the development of dynamic models, studies concerning the effects of perturbation in relation to microbial dominance and the integration of the study of below-ground food webs with ecological theories.