中文摘要：

在中高纬度和高海拔地区,冻融作用影响土壤的理化性质和微生物性状,进而影响土壤呼吸过程。研究冻融作用下土壤呼吸的变化,对准确估算全球碳循环具有重要意义。以科尔沁沙地沙质草地、樟子松疏林草地和农田为研究对象,通过冻融实验比较不同土地利用方式和冻融循环对土壤呼吸的影响。结果表明：土地利用方式对土壤呼吸有显著影响,在未发生冻融作用时沙质草地土壤呼吸速率显著大于樟子松疏林草地和农田（P〈0.05）,3种土地利用方式的土壤呼吸平均速率分别为0.339、0.258和0.234μmolCO2.m-2.s-1;不同冻融循环对沙质草地和樟子松疏林草地土壤呼吸影响显著（P〈0.05）。其中,一次冻融循环条件下沙质草地、樟子松疏林草地和农田土壤呼吸平均速率分别为0.276、0.243和0.233μmolCO2.m-2.s-1,多次冻融循环条件下分别为0.314、0.274和0.259μmolCO2.m-2.s-1;沙质草地、樟子松疏林草地和农田的Q10值分别为116.0、26.2和16.4,表明冬季低温条件下土地利用方式强烈影响土壤呼吸对温度的敏感性。

英文摘要：

Soil freezing-thawing cycle is common in mid-high latitude and high altitude regions,which may affect soil physicochemical and/or biological properties,and further,soil respiration process.To study the variations of soil respiration rate under freezing-thawing cycle is of significance in accurately estimating global carbon budget.Taking the sandy grassland （SG）,Mongolian pine savanna （MPS）,and farmland （FD） in Keerqin Sandy Lands as test objects,a laboratory experiment was conducted to study their soil respiration rates under freezing-thawing.Land use pattern had significant effects on the soil respiration rate.In the control （no freezing-thawing）,the respiration rate was higher in SG than in MPS and FD （P0.05）,with the value being 0.339,0.258,and 0.234 μmol CO2·m-2·s-1,respectively;while under freezing-thawing,the soil respiration rate was significantly higher in SG and MPS than that in FD （P0.05）.The mean soil respiration rate in SG,MPS,and FD under one freezing-thawing cycle was 0.276,0.243,and 0.233 μmol CO2·m-2·s-1,and that under multi-freezing-thawing cycles was 0.314,0.274,and 0.259 μmol CO2·m-2·s-1 respectively.The Q10 value in SG,MPS,and FD was 116.0,26.2,and 16.4,respectively,suggesting the strong effects of land use pattern on the temperature dependence of soil respiration at low temperature in winter.