Response of nitrogen mineralization to litter addition and exclusion in soils of Cinnamomum camphora plantation

Nitrogen mineralization was evaluated by controlling above-ground litter input in soils of Cinnamomum camphora plantation in the Tianjiling Forest Farm in Changsha City,southern China's Hunan Province.Nitrogen mineralization was measured using the resin-core technique from July 26 to August 23,2007.The results show that after seven months with litter treatment,there was a significant difference between the inorganic nitrogen concentrations of soils treated by litter exclusion,litter addition and control(P﹤0.05),with the order of litter addition(18.96 mg /kg) control(16.36 mg /kg)litter exclusion(10.99 mg/kg).After 28 days'incubation,the nitrate nitrogen concentrations had significant differences before and after incubation in three soil treatments(P﹤0.05),which rose from 0.67,0.51 and 0.39 mg /kg before incubation to 3.10,7.11 and 6.67 mg /kg after incubation,respectively.No significant difference was found between ammonia nitrogen concentrations before and after incubation(P﹥0.05).The net nitrogen mineralization values were positive in treatments of litter exclusion,litter addition and control,which increased by 4.83,1.45 and 1.26 mg /kg,respectively,with the order of net nitrogen mineralization rates as follows:litter exclusion(0.173 mg/(kg·d)) control(0.052 mg /(kg·d))litter addition(0.045 mg/(kg·d)).The results help us better understand the process of soil nitrogen cycle in the sub-tropical forest ecosystems.