Responses of soil fauna community to simulated N deposition

Nitrogen deposition is a serious global problem and will likely have a significant effect on ecosystem structure and functions. The responses of soil fauna to a simulated N deposition were studied in man-made plots of subtropical China in July and October, 2003, and February and May, 2004. Dissolved NH4NO3 was sprayed twice per month onto the soil since January, 2003, equivalent to 0 (CK), 5 (low), 10 (medium), 15 (high) and 30 (double high) g/(m2·a). After 18 months’treatment, bacteria and fungi communities increased significant continually with the increased N deposition, and it was the similar case of the content of available N, but pH decreased. The individuals, group abundance and diversity of soil fauna were significantly related with sampling date, and they increased during the year on the whole. For the vertical distribution, soil fauna individuals, group abundance and diversity were significantly higher in layer I than in layer II and III. Soil fauna community was obviously developed by the N deposition addition, and at the same time there was a threshold among the effects of different treatments. Compared with CK treatment, it appeared a larger soil fauna community of the N treatment, and the difference was enlarged with the time. There were significant interaction between N treatment and sampling date. Except for February, 2004, soil fauna community laid the highest level all the time, but CK treatment the lowest on the contrary, and the trends were clear mostly at the last sampling;There was also clear interaction between N treatment and the vertical distribution of soil fauna: in layer I, soil fauna developed firstly and decrease then obviously with the increased N deposition addition, and the peak laid at medium treatment. But under the highest N treatment, soil fauna were concentrated into deep soil, and the community developed significantly in layer III and the negative effects of the treatment was indicated. It was suggested that the effects of different N treatments must have been related with the level of N saturation, especially the content of NO3. -