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.