IMPACT OF SOIL FAUNAL STRUCTURE ON DECOMPOSITION AND N-MINERALIZATIONIN RELATION TO TEMPERATURE AND MOISTURE IN FOREST SOIL

Physical factors, decomposer community and soil processes such as deco mposition and mineralisation are connected with each other by complex interactions. The aim of this study was to test how the impact of the community structure on the mineralisation processes differs with respe ct to temperature and moisture. The experiment was carried out in micr ocosms with defaunated raw humus and litter that were reinoculated wit h a) microflora, microfauna and enchytraeids, or b) the same together with a diverse microarthropod community. The soil was adjusted to wate r contents 40, 53 or 62% of fresh mass, and incubated at +2, +6 or +15 degrees C for 27 weeks. The experiment revealed complex interactions between physical conditions in soil and faunal community structure in relation to decomposition and mineralisation. At low and medium moistu res the presence of microarthropods reduced the populations of nematod es and enchytraeids, as well as the net N mineralisation. Amount of NH 4+ in soil was in positive correlation with enchytraeid biomass. It wa s concluded that the diverse community of microarthropods affects the mineralisation indirectly by regulating the enchytraeid populations. H owever, at high moisture the microarthropods failed to control enchytr aeid numbers, and mineralisation showed no relation to the community s tructure.