Abstract: Soil microbial communities may respond to anthropogenic increases in ecosystem nitrogen (N) availability, and the microbial response may ultimately feed back on ecosystem carbon and N dynamics. We examined the effects of nitrogen deposition on soil microbial community structure composition in a Chinese poplar plantation subject to simulated nitrogen deposition for two years at Dongtai Forest Farm of Jiangsu Province, China. Nitrogen loadings were designed at 5 levels as N0 (control), lowN (50 kg·hm^-2·a^-1), mdeiumN (100 kg·hm^-2·a^-1), highN (150 kg·hm^-2·a^-1), ultra highN (300 kg·hm^-2·a^-1), respectively. Nitrogen addition was carried out within the forest monthly during May and August in 2012-2013. Soil samples were collected at 0-10 cm depths in October 2013. Soil microbial community structure composition was measured using phospholipid fatty acid (PLFA) analysis. Nitrogen additions did not change the total content of PLFAs but increased the amount of bacterial and grampositive bacterial PLFAs. The content of fungal PLFAs did not change significantly, except under the medium level N addition. Nitrogen additions of medium, high, ultrahigh levels decreased the amount of arbuscular mycorrhizal fungal and protistic PLFAs. Principal component analysis (PCA) of microbial PLFA data showed that microbial community structure were changed in all Nadded plots except the lowN trreatment. Our findings indicated that soil community structure can be influenced by shortterm N additions in the poplar plantation.

Key words: soil microbial community, forest restoration, Picea asperata plantation, phospholipid fatty acid