冻融作用对陆地生态系统氮循环关键过程的影响效应及其机制

冻融作用是中、高纬度及高海拔地区土壤普遍存在的一种自然现象，是非生长季陆地生态系统氮循环的重要影响因素.冻融作用主要通过改变土壤的理化性质及生物学性状来影响氮素在土壤中的迁移与转化.目前，冻融作用对陆地生态系统氮循环各个过程影响的研究结果不尽一致，理论机制尚不明晰，研究方法也需进一步地探索与创新，因此有必要对现有成果进行梳理和分析，以更好地把握冻融作用下的氮循环过程.本文结合国内外已有研究成果，论述了冻融作用对陆地生态系统氮循环关键过程（氮矿化、固持、硝化与反硝化过程、氮淋溶及气态损失）的影响效应及其主要机制，对目前研究中存在的不足进行了剖析，并对未来研究中迫切需要关注的重点研究方向进行了探讨与展望.

Effects and mechanism of freeze-thawing cycles on key processes of nitrogen cycle in terrestrial ecosystem.

As a widespread natural phenomenon in the soil of middle and high latitude as well as high altitude, freeze thawing cycles have a great influence on the nitrogen cycle of terrestrial ecosystem in non growing season. Freeze thawing cycles can alter the physicochemical and biological pro perties of the soil, which thereby affect the migration and transformation of soil nitrogen. The impacts of freeze thawing cycles on key processes of nitrogen cycle in terrestrial ecosystem found in available studies remain inconsistent, the mechanism is still not clear, and the research methods also need to be further explored and innovated. So it is necessary to sum up and analyze the existing achievements in order to better understand the processes of soil nitrogen cycle subjected to freeze thawing cycles. This paper reviewed the research progress in China and abroad about the effects and mechanisms of freeze thawing cycles on key processes of nitrogen cycle in terrestrial ecosystem, including mineralization, immobilization, nitrification and denitrification, N leakage and gaseous loss, and analyzed the deficiencies of extant research. The possible key research topics that should be urgently paid more attention to in the future were also discussed.