Conclusions
A 10-year field N-loading experiment was conducted and the responses of soil nematode communities to N addition were investigated in a subtropical Chinese fir forest. We first found that long-term N loading affected the abundance and community structure of soil nematodes in the surface soil layer. N addition increased the abundances of total nematodes, bacterial-feeding nematodes, and fungal-feeding nematodes, but decreased the abundance of plant-feeding nematodes at 0-20 cm soil depth. Secondly, SEM and network analyses verified that N addition changed the nematode community structure. N addition directly affected plant-feeding nematodes and weakened the importance of the plant-based energy channel and enhanced the importance of the fungal-based energy channel. Effects of N addition on soil bacterial-, fungal- and plant-feeding nematodes were contributed the resource inputs and soil physico-chemical variations indirectly. These responses of community structure and trophic groups of soil nematodes may therefore affect soil processes and food web functions under N addition in forest ecosystems.