title: Integrating species composition and leaf nitrogen content to indicate effects of nitrogen deposition.
abstract: Nitrogen (N) deposition has been increasing globally and has arisen concerns of its impacts on terrestrial ecosystems. Ecological indicators play an important role in ecosystem monitoring, assessment and management in the context of an anthropogenic transformation of the global N cycle. By integrating species composition and leaf N stoichiometry, a new community N indicator was defined and validated in the understory plots of an N enrichment (as NH4NO3) experiment in an old-growth boreal forest in Northeast China. Three-year N additions showed no significant effect on the understory species richness, but an obvious shift in species composition occurred. The response of leaf N content to N additions was generally positive but varied by species. Overall, the community N indicator increased significantly with higher N addition level and soil available N content, being in the shape of a non-linear saturation response curve. The results suggest that the community N indicator could be an effective tool to indicate changes in ecosystem N availability. Critical values of the community N indicator for specific vegetation type could potentially provide useful information for nature conservation managers and policy makers.
authors.affiliation: Department of Ecology, College of Urban and Environmental Sciences, and Key Laboratory for Earth Surface Processes of the Ministry of Education, Peking University, Beijing 100871, China; College of Resources Science & Technology, and State Key Laboratory of Earth Surface Processes and Resource Ecology, Beijing Normal University, Beijing, 100875, China. Electronic address: enzaidu@bnu.edu.cn.
authors.forename: Enzai
authors.initials: E
authors.lastname: Du
mesh_terms: D002681:China; D017753:Ecosystem; D004784:Environmental Monitoring / Q000379:methods*; D009584:Nitrogen / Q000032:analysis*; D018515:Plant Leaves / Q000737:chemistry* / Q000502:physiology; D012987:Soil
chemical_list: D012987:Soil; D009584:Nitrogen
keywords: Ecological indicator; Leaf nitrogen content; Nitrogen availability; Nitrogen deposition; Species composition