Freeze-thaw cycle is ubiquitous phenomenon at high elevations and temperate zone. On North-hemisphere, 55% terrestrial area experienced seasonal freeze-thaw cycles.

Recent years, along with the global warming, the warm winter and thin snow-pack may change the pattern of freeze-thaw cycles. For example, in snow-free areas, where the warm winter may decrease the soil freeze-thaw and in areas with snow cover, the warm winter may result thinner snow pack, reduce its isolation effect and increase in the strength, frequency and sustainability of the freeze-thaw cycle.

These changes may affect soil N cycling by changes in soil structure, soil microbes, plant root system and litter input. However, till now, the effect has been seldom synthetically analyzed.

Prof BAI E and Dr GAO Decai in the research group of Bio-geo Chemistry in IAE collected a data set containing 1519 numbers about Nitrogen cycles in 63 publications and made meta-analysis for the effect of freeze-thaw cycles.

The results show that the treatment of freeze-thaw cycle significantly increased leaching of Ammonium N, Nitrate N, Nitrite N and release of Nitrous Oxide to 18.5%, 18.3%, 66.9% and 144.9%，reduced 26.2% total soil N and 4.7% microbe N, but had no significant effect on net rate of N mineralization and nitrification.

Meanwhile, the temperate and farm ecosystemhave responses higher than that of North-pole tundra ecosystem.

So, the changes in freeze-thaw cycle resulted from climate changes may increase the release of in-organic N, and N loss by leaching.

The analysis helps to understand the responses of N cycle to freeze-thaw cycles and the relations of freeze-thaw cycle to N release.

The work has published entitled as Responses of Terrestrial Nitrogen Pools and Dynamics to Different Patterns of Freeze-Thaw Cycle：A Meta-analysis in Global Change Biology.

The work was supported from 973 Project, NNSFC CAS Front Key project and CAS Strategy Key Project.