氮沉降对陆地生态系统关键有机碳组分的影响

土壤有机碳不仅可以为植物生长提供营养元素,维持土壤良好的物理结构,而且库容巨大,其储量的微弱变化会导致大气圈中CO₂浓度发生较大变化,从而直接影响全球碳平衡格局。氮是影响陆地生态系统植物生长的首要营养元素,大气氮沉降以及人为氮肥施入作为陆地生态系统氮的重要来源,其变化会深刻改变陆地生态系统的植物生长和净初级生产力,并进而影响全球碳循环和其他生态系统过程。欧美等国的生态学者近20年来就氮输入对不同生态系统碳库的影响进行了广泛而深入的研究,我国学者近年来也逐渐开始关注氮输入对陆地碳循环相关过程的定量研究,并取得了一系列的研究进展。但尽管如此,氮沉降以及人为氮输入对陆地生态系统碳循环的影响效应与作用强度依然是目前四大碳汇机制研究最为薄弱的一个环节。鉴于此,本文综述和分析了近年来氮沉降对陆地生态系统土壤总有机碳(total organic carbon,TOC)、溶解性有机碳(dissolved organic carbon, DOC)、微生物量碳(microbial biomass carbon,MBC)等不同土壤碳组分影响的相关研究结果,并针对目前氮沉降增加对陆地生态系统土壤碳库影响研究存在的问题提出了几点展望,以期对我国未来相关领域研究的进一步开展起到一定的参考作用。

Effects of nitrogen deposition on critical fractions of soil organic carbon in terrestrial ecosystems

Soil organic carbon can provide the nutrient for plant growth and maintain soil physical structure well, and soil organic carbon (C) pool is so large to lead to big changes in CO₂ concentration in atmosphere even its changes are small, thus soil organic C pool has a direct effect on the global C balance. Nitrogen (N) is recognized as the primary limiting nutrient for plant growth in terrestrial ecosystems. Atmospheric N deposition and anthropogenic N input are important N sources to terrestrial ecosystems, whose alteration will profoundly change plant growth and net primary production in terrestrial ecosystems, accordingly impacts global C cycles and other ecosystem processes. Ecological scholars in European countries and the United States have carried on a series of extensive and in-depth studies on the effects of N input on various types of ecosystem C pools during the past 20 years. Chinese scholars, in recent years, also turned their attention to the study of N input’s impacts on the terrestrial C cycle processes, and have made a lot of research advances. Nevertheless, the effect of N deposition and anthropogenic N input and its intensity on C cycles are still a weakest part among the studies on the four main C sink mechanisms. In view of this, this article reviews and analyses the influences of atmospheric N deposition on the total organic C (TOC), dissolved organic C (DOC) and microbial biomass C (MBC) in the soil pool of terrestrial ecosystem, and puts forward some prospects on the problems existed in present researches, which had the potential to be a reference for the further study carried out in the future in China.