氮沉降对森林土壤主要温室气体通量的影响

Effects of nitrogen deposition on the greenhouse gas fluxes from forest soils

大气氮沉降已经并将继续对森林土壤主要温室气体(CO2、CH4和N2O)通量产生影响。综述了国内外氮沉降对森林土壤主要温室气体通量影响及其机理的研究现状。由于森林类型、土壤N状况、氮沉降量及沉降类型等不同,氮沉降对森林土壤主要温室气体通量的影响主要表现为抑制、促进和不显著3种效果。在N限制的森林中,氮沉降对土壤主要温室气体通量无显著影响,或促进土壤CO2排放;在"N饱和"的森林中,氮沉降可减少土壤CO2排放,抑制对大气CH4的吸收,增加N2O排放。分析了产生以上影响效果的作用机理,介绍了氮沉降对森林土壤主要温室气体通量影响的研究方法,探讨了该领域存在的问题及未来研究的方向。

Human activities such as combustion of fossil fuels, intensive agriculture and stockbreeding, have significantly altered the global nitrogen cycling in the last several decades, resulting in increasing concentrations of nitrogenous compounds in the atmosphere and increasing N deposition several fold. Nitrogen deposition can lead to changes in N-status of forest soils, species composition, and possible decline in the function and primary productivity of forest. In addition, nitrogen deposition can alter the rates of microbial N- and C- turnover, and thus, can affect the fluxes of greenhouse gases （ e. g. CO2, CH4, and N2O） from forest soils. The effects of N deposition on the fluxes of greenhouse gases from forest soils are reviewed in this paper. The effects of N deposition on greenhouse gas fluxes from forest soils range from positive to negative depending on forest type, N-status of the soil, and the rate of N deposition. In forest ecosystems where biological processes are limited by N supply, N additions either stimulate soil respiration or have no significant effect, whereas in ＂N saturated＂ forest ecosystems, N additions decrease CO2 emission, reduce CH4 oxidation, and elevate N2O flux from the soil. The mechanisms and research methods about the effects of N deposition on greenhouse gas fluxes from forest soils are also reviewed in this paper. Finally, the present and future research needs about the effects of N deposition on the fluxes of greenhouse gases from forest soils are discussed.