Soil faunal response to land use: effect of estuarine tideland reclamation on nematode communities

Effects of reclaiming estuarine tideland on soil fauna biodiversity were studied in the Yangtze river estuary of China, focusing on nematodes. The responses of the nematode community to the disturbance caused by reclamation can be summarized as: (1) there was no distinct decline in the density of nematodes, but the community structure changed greatly; (2) the proportions of plant feeders and omnivorous nematodes increased after reclamation, whereas the proportions of bacterial feeders and predators decreased; (3) more apparent patchiness of nematode distribution was found in the reclaimed terrestrial environment than in intertidal marshes. Generally, agrocenoses have been characterized by low proportions of predator-omnivores. Our study indicated that omnivorous dorylaimids can be markedly abundant in agroecosystems, depending on the annual crop rotation and tillage practices. The predominant trophic group in cultivated land shifted between omnivorous nematodes and plant feeders, implying that the food chain path changed with agricultural processes. The maturity index (MI) provides little information in the present study, probably because the MI value embraced information of many disturbances including vegetation succession and changes in soil features. The faunal profile, representing both enrichment and structural conditions, is believed to be effective and more informative for analyzing the nematode successional trends.