Effects of nitrogen enrichment on the greenhouse gas fluxes in natural wetlands and the as-sociated mechanism: A review

Natural wetlands are an important source,sink and convertor of greenhouse gases,and play an important role in stabilizing global climate change. In recent years,the nitrogen(N)enrichment in natural wetland ecosystems through intensive fossil fuel combustion,N fertilizer application and industrial sewage discharge have affected directly or indirectly the production,consumption and flux of nitrous oxide(N2O),carbon dioxide(CO2),and methane(CH4). Effects of nitrogen input on greenhouse gases have been increasingly received attention. In this paper,the main research progress of effects of nitrogen enrichment on the greenhouse gas fluxes in natural wetlands and the associated mechanisms are reviewed. The effects of nitrogen enrichment on the greenhouse gas fluxes in natural wetlands have positive,negative and ineffective patterns,due to differences in nitrogen fertilizer types and input levels,physical and chemical properties of soil,microbial activity,environmental factors,redox potential and so on. Finally,the problems of current research and some future topics are discussed.