Progress of Freeze-thaw Effects on Carbon,Nitrogen and Phosphorus Cyclings in Soils

As a ubiquitous non-biological stress in high latitudes,freeze-thaw effects are sensitive to climate change.Along with global climate warming,freeze-thaw phenomenon is receiving ever-significant attention.The biogeochemistry processes in soils keep notable response to freeze-thaw influence.Here we review the primary researches about carbon,nitrogen,phosphorus cyclings under freeze-thaw treatment in soils.We mainly focus on changes of dissolved organic carbon,greenhouse gas emission,nitrogen and phosphorus turnover in soils.On the basis of available literature,freeze-thaw effects could damage microbes and root cells,lead their internal carbon and nitrogen release which increase corresponding concentration in soil solution.Macroaggregates in soils could be destroyed into microaggregates with successive freeze-thaw cycles,which increase the availability of nutrients to soil microorganisms by larger surface area.During freeze-thaw period,nutrients and substrates produced in above-mentioned mechanisms would stimulate metabolisms of microbes and turnover of carbon,nitrogen and phosphorus in soils which however increase potential nutrients run-off in turn.Because of differences in soil types,vegetation constitutes and microorgnisms diversity,there are still debates on how continuous freeze-thaw effects influence nutrients cyclings in soils.Besides,our review points out the weakness of research methods in freeze-thaw studies.The recommendations for future freeze-thaw researches are also indicated.