A Review: Response of soil CO2 and N2O emissions to freeze-thaw pattern change
冻融交替对土壤CO2及N2O释放效应的研究进展

In high latitude and altitude ecosystems, surface soil is subjected to experience freeze-thaw cycles during alternating autumn and winter or spring period. As the role of freeze-thaw alternation can change the hydrothermal properties of soil, and produce the effects on soil physicochemical properties and biological characteristics, which led to the breakdown of soil aggregates and the deaths of some micro-organisms and fine roots, release a certain degree of active organic matter and nutrients to enhance the remaining anti-microbial nitrification and respiration, thus can affect soil biological, biochemical process and bio-geochemical cycle. The conducted studies on the tundra, taiga and other Arctic and sub-Arctic ecosystems showed that the number of alternate freezing and thawing, freeze-thaw extreme temperatures, soil moisture, soil aggregates structure and other factors had significant effects on the release of CO2 and N2O fluxes, generally during several previous freeze-thaw cycles greenhouse gas emissions increased, then dropped to a more stable level. The current research of freeze-thaw cycle is mainly targeted to the northern high-latitude areas, but with inadequate attentions on the mechanism of the effect of alternate freezing and thawing that lead to greenhouse gas emissions. The Qinghai-Tibet Plateau of China is the vast high-altitude zone, a slight warming maybe increase the times of alternate freezing and thawing of seasonal frozen soil layer, even lead to the seasonal disappearance of permafrost, so in the context of global warming strengthening the research on the effects and processes of sub-alpine mountains of China's seasonal freeze soil ecosystem studies, particularly the changes of greenhouse gas emissions and the mechanism of these changes, plays an important role in revealing the regional effects of global change as well as high-altitude ecosystem management