Vertical distribution of soil nematodes under different land use types in an aquic brown soil

A field investigation was conducted at the Shenyang Experimental Station of Ecology to study the vertical distribution of nematode communities down to a depth of 150 cm under four land use types (paddy field, maize field, fallow field and woodland) in an aquic brown soil of Northeast China. The results showed that the numbers of total nematodes and trophic groups exhibited a gradual decrease trend with depth under different land use types. The numbers of total nematodes, bacterivores, fungivores, and plant parasites were positively correlated with the contents of TOC, total N, and alkali N in the four land use types. The majority of nematodes were present in the 0-30 cm soil layers. No significant effects were found on the number of total nematodes at all depths among the maize field, fallow field and woodland. Bacterivores were found to be the most abundant group in the paddy field, while plant parasites were observed to be the most abundant group in the maize field, fallow field and woodland. The number of fungivores at the depths of 0-5 and 5-10 cm was higher in the maize field than in the other land use types. Omnivores-predators were found in relatively low numbers under each land use type, with a higher presence in the fallow field and woodland at the depths of 0-5, 5-10, 10-20 cm compared with the paddy and maize fields. 54 genera were observed throughout the four land use types in our study. The woodland treatment supporting greater basal resource inputs tended to result in a higher diversity of nematodes. The number of genera reached a maximum at the depth of 5-10 cm under each land use type. The faunal profiles showed that soil food webs in the fallow field and woodland were structured, and those in the paddy and maize fields were stressed. The faunal analysis provided a useful tool for diagnostic interpretation of the condition of upper soil layers.