Effects Of Nitrogen Addition On Soil Fauna Community Structure In The Poplar Plantations In A Coastal Area Of Eastern China

Anthropogenic nitrogen(N) deposition is a major threat to biodiversity and ecosystem services around the world. As soil fauna are sensitive to environmental changes, increasing nitrogen deposition may profoundly influence the structure and function of soil faunal communities. We have conducted a field experiment to simulate nitrogen deposition with 5 nitrogen addition treatments(i.e. 0、5、10、15、30 g N·m-2·a-1) at Dongtai Forest Farm in a coastal area of Jiangsu Province since May 2012.To investigate the effects of nitrogen addition on soil faunal communities and their inter-relationships,soil fauna in the poplar plantations was assessed in 3 growing seasons after addition. Results showed that:(1) With increasing stand age, the individual density of total soil fauna and dominant groups(Oribatida, Prostigmata) increased obviously, but richness of species decreased. The individual density of soil fauna in litter layer was significantly lower than in soil layer. 6-year-old poplar plantations had the biggest number of soil faunal density in the litter layer, while the soil layer was opposite. There were higher density and number of groups in topsoil layer than that in subsoil layer.(2) The group number of soil fauna with different sampling date : June>September>March>December. Soil faunal density of different aged stands differed in sampling date. In December, there was the lowest density in three stands, and highest in June or September.(3) The individual density of soil fauna decreased after an initial increase with the increasing nitrogen level. Furthermore, there was a significant reduction in the diversity and evenness of soil fauna species in N3 and N4 treatment. N addition(especially N2 and N3 moderate treatment) had a promoting effect on soil faunal density of each layer. Whatever, N addition did not affect the surface aggregation of soil fauna.(4) There was a tendency of the value of soil p H and C/N to be lower in N-treated than in control plots. The contents of NO3--N and TN were higher in high-level N treatment. The response of soil properties could have a negative impact on the total density, group number and diversity of soil fauna. The variation of soil faunal diversity was coincident with the seasonal variation pattern of the air temperature and precipitation.