冻融交替对土壤氮素循环关键过程的影响与机制研究进展

冻融交替是由于季节或昼夜热量的变化,在表土及以下一定深度形成的反复冻结和解冻的过程,是普遍存在于中、高纬度及高海拔地区的一种自然现象。在全球变暖的背景下,部分地区的土壤环境将经受更广泛和频繁的冻融交替作用,这将对土壤氮素循环关键过程产生深远的影响。冻融交替主要通过改变土壤的理化性质使土壤微生物量、微生物群落的组成和结构发生改变,进而影响氮素在土壤中的迁移与转化,是陆地生态系统氮循环的重要影响因素。目前,关于冻融交替对土壤氮素循环关键过程影响的研究结果还不尽一致,其影响机制尚不明晰,研究方法也还有待进一步创新。重点论述了冻融交替对土壤氮素循环各个关键过程的影响效应,归纳总结了冻融交替对土壤氮素循环的影响机制,简要指出了目前研究过程中存在的一些不足,并对未来研究中值得重点关注和深入研究的科学问题进行了探讨与展望。

A review of freezing-thawing cycle effects on key processes of soil nitrogen cycling and the underlying mechanisms

Freeze-thawing cycle, the repeated freezing-thawing process at surface and a certain depth below soil due to seasonal or diurnal changes in heat, is a widespread natural phenomenon in the soil of middle to high latitude and high altitude. In the context of global warming, the extension and frequency of soil freezing-thawing cycle may be enhanced in some regions due to the increased occurrence of discontinuous snow cover and rain-on-snow events. These changes in freezing-thawing cycle may strongly affect soil physical and chemical properties, as well as soil microbial biomass, microbial composition and structure, which in turn would have profound impacts on the key processes of soil nitrogen (N) cycling. At present, available results of the effects of freezing-thawing cycle on the key processes of soil N cycling remain inconsistent. The underlying mechanism is still not clear and the research methods need to be further explored and innovated. Moreover, a comprehensive understanding of the key processes of soil N cycling in response to different patterns of freezing-thawing cycle is not available. Therefore, on the basis of extensive review of the existing research results, this paper summarized the research progresses and underlying mechanisms of the effects of freezing-thawing cycle on key processes of soil N cycling, including mineralization, immobilization, nitrification and denitrification, N leaching and gaseous loss. Additionally, some deficiencies in current research were pointed out. The possible key topics in the future study were also suggested.