Effects of different nitrogen additions on soil microbial communities in different seasons in a boreal forest

In the global change scenario, nitrogen (N) deposition has the potential to affect the soil microbial communities that play critical roles in ecosystem functioning. Although the impacts of N deposition on soil microbial communities have been reasonably well studied, microorganism responses to the N addition combined with the seasonal change have rarely been reported. This study was conducted to evaluate the effects of different levels of N addition (0, 2.5, 5.0, and 7.5 g N.m(-2).yr(-1)) on soil microbial communities in different seasons (spring, summer, and autumn) in a boreal forest. Our results showed that the soil physical-chemical properties were found to be changed by N addition and seasonal changes were correlated with microbial community structure. The N addition and seasonal changes significantly affect the diversity and abundance of the microbial community, while their interactions only affect the bacterial abundance and the fungal diversity. In addition, our results also provided clear evidence for specific responses of microorganisms to the different N additions and each season. Our findings suggest that the microbial community response to N deposition could be the seasonal change and will strongly correlate with environmental change.