Effects Of Simulated Nitrogen Deposition On Soil Active Organic Carbon In Poplar Plantations In A Coastal Area, China

The impacts of nitrogen deposition on soil labile carbon at different age poplar plantationswere examined in this study. Beginning in May2012, we conducted a field experiment tosimulate nitrogen deposition with five treatments at Dongtai forest farm in Jiangsu province. Theresults are showed below:(1) The content of soil total organic carbon in all poplar plantations had no significantdifference under the different nitrogen levels. The content of soil total nitrogen increased with theincreasing of nitrogen levels.(2) The soil microbial biomass carbon decreased after an initial increase with the increasingnitrogen level in the5and9years old poplar plantations, and increased with the increasednitrogen level in15years old poplar plantations. Nitrogen increasing enhanced the content of soildissolved organic carbon in all poplar plantations.(3) The soil MBC and DOC exhibited obvious seasonal patterns. Overall，the contents ofsoil MBC and DOC were higher in summer and autumn，but lower in winter and spring.(4) There was a significant correlation between the soil MBC and DOC. Furthermore, thesoil MBC and DOC were significantly correlated with the soil TN, MBN, DON, NH4+-N,NO3--N，respectively. The MBC had a significant positive correlation with soil temperature(p<0.01). The DOC did not correlated with soil temperature (p>0.05).Our results implicate that the seasonal variations of soil labile organic in poplar plantationswere affected by soil temperature. In addition，nitrogen deposition might enhance the content ofsoil labile organic carbon, and then, affect the dynamics of soil organic carbon in the poplarplantations.