全球森林土壤N_2O排放通量的影响因子

Factors affecting global forest soil N_2O emission flux

森林生态系统在全球变暖格局下的地位和作用,尤其是土壤氮库对大气氮沉降增加的响应逐渐成为全球变化研究的热点。本文通过对已有文献资料的调研和整理,分析了1984—2009年间全球38个森林土壤N2O排放通量的野外原位观测结果的分布特征,评估了森林土壤N2O年排放累积通量对大气氮素沉降量和水热条件等因子变化的响应。结果表明,全球森林土壤N2O排放通量的平均值为0.47kgN·hm-2·a-1,而且土壤N2O释放通量随着纬度增加逐渐降低。作为一个复杂的生态过程,土壤N2O累积释放量同样受到年均温、年降水量以及土壤属性的显著影响。其中全球森林土壤N2O释放温度敏感性系数(Q10值)约为1.5。另外,森林土壤N2O排放通量也随着氮沉降量的增加而显著增大,大气氮沉降量可解释土壤N2O排放通量在不同区域之间53%的差异;土壤pH、年均温和大气氮沉降量可以解释区域森林土壤N2O排放通量变化的55%。

The role of forest ecosystem under global warming, especially the response of forest soil nitrogen （N） pool to increased atmospheric N deposition, has become one of the hotspots in global change study. Through investigating and systematizing published data, this paper analyzed the distribution patterns of forest soil N2O emission fluxes from 38 in situ observations at global scale in 1984-2009, and assessed the response of forest soil annual cumulative N2O flux to atmospheric N deposition and to the variations in water and heat conditions. In global scale, forest soil N2O flux was averagely 0.47 kg N·hm-2·a-1, and declined gradually from low to high latitude. As a complex ecological process, forest soil cumulative N2O flux was also significantly affected by mean annual temperature, annual precipitation, and soil properties. The temperature sensitivity index of soil N2O flux （Q10 value） in global forest ecosystem was about 1.5. Moreover, forest soil N2O flux increased significantly with increasing atmospheric N deposition. The atmospheric N deposition could explain 53% of the variations in the forest soil N2O flux across different regions, while the soil pH, mean annual temperature, and atmospheric N deposition could explain 55% of the variations within regions.