Abstract: Soil nematode is an important component of soil ecosystem, and plays important roles in litter decomposition and nutrient cycling. In May, July, and September 2007, investigations were made to study the effects of disturbances on the diversity of soil nematodes in secondary forest and larch plantation of Northeast China, with bare land as the control. The results showed that the individual number and richness of soil nematodes decreased with the increase of disturbance intensity, being in the order of secondary forest < larch plantation < bare land. Based on nematode faunal analysis, which is helpful to understand the status of nematode food web under disturbances, the environment of bare land was under stress, and the nematode food web was threatened and disturbed most heavily. On the contrary, the structures of the food web in secondary forest and larch plantation were relatively mature and disturbed less heavily. Disturbances changed the species composition of soil nematode community, i.e., the nematode diversity decreased with the increase of disturbance. All of the results suggested that the disturbance of aboveground part (forest vegetation) had irdluenced underground ecosystem.

Key words: Loess hilly and gully region, Alfalfa, Soil water