中文摘要：

冻融交替是作用于土壤的非生物应力,对土壤的理化和生物学性质均产生直接或间接影响.在气候变暖条件下,冻融作用对冻土区土壤碳库关键生物地球化学循环过程的影响已成为当前研究的热点.经过室内冻融模拟结合野外观测,大量研究结果表明不同冻融温度、速率、次数对土壤有机碳和微生物的影响不同.冻融作用能改变土壤理化性质,降低土壤团聚体稳定性和土壤容重,增加营养元素释放.冻融作用对活性有机碳影响较显著,可加剧可溶性有机碳的流失,抑制土壤微生物量碳的产生;此外,冻融作用能改变土壤微生物的生理活性和群落结构,使微生物的数量降低,细胞破裂,释放碳氮营养物质以供存活的微生物利用.以往研究主要集中在冻融作用对土壤活性有机碳、土壤微生物群落等单方面过程,缺乏对土壤酶活性及其与土壤碳组分相结合的生物过程研究.在综述冻融作用对土壤活性有机碳、土壤呼吸和土壤微生物特性影响的基础上,提出未来的研究应集中于全球变化与冻融的联系,冻融作用下土壤碳释放的机理以及对生态系统的影响等方面.

英文摘要：

As an abiological effect on soil environments,the freeze-thaw process directly or indirectly influences the physical,chemical and biological properties of soils.Under warming climate,increasingly attention has been paid to the effect of soil freezing-thawing alternation on carbon and nitrogen biogeochemical cycles.Through controlled laboratory experiments and in-situ observations of the freeze-thaw process,many studies have demonstrated that different temperature changing rates and frequencies of the freeze-thaw process have various effects on soil organic carbon and microorganisms.First of all,they alter soil physical properties,decrease soil aggregate stability and bulk density,and increase the nutrients release.Secondly,they influence the stability of the available organic carbon and inhibit soil microbial biomass carbon production.Finally,they change microbial activity,shift the microbial community composition,disrupt a large fraction of the microbial biomass,and lyse a substantial proportion of microbial cells,resulting in C and N releases for living microorganisms.However,previous studies mainly focused on the effects of the freezing-thawing alternation on dissolved organic matter and microorganisms,while soil enzyme activity,soil carbon fractions and their relationships are largely neglected.Based on the previous studies and the remained questions,the following prospects in this field are proposed： improving the study on the relationships between climate warming and freeze-thaw process,the mechanisms of carbon release under influences of freeze-thaw process,and the impacts of freeze-thaw processes on ecosystems.