中文摘要：

在陈巴尔虎旗具有代表性的草原类型,选择自由放牧和围封样地,采用壕沟法进行野外取样,研究放牧和围封下的根系以及土壤的碳密度及碳贮量。结果表明：围封后羊草草原和草甸草原地下碳储量增加,差异显著;针茅草原地下碳储量增加,差异不显著。其中围封草甸草原根系固碳量和土壤碳储量最大,分别为79.74 g/m2和21 150.49 g/m2;其次为围封羊草草原,分别为53.12 g/m2和14 643.65 g/m2;针茅草原最小,分别为47.90 g/m2和11 273.52 g/m2。与放牧样地地下碳储量相比分别增长了35.89%、50.17%、3.74%。虽然根系固碳量只占土壤碳储量的极少部分,但根系通过改良土壤结构,对增强碳源汇集和贮存、积累碳素具有重要的影响。自由放牧样地的根系碳密度和土壤碳之间没有显著相关性（R=-0.61）。围封样地根系生物量也随土壤深度增加呈递减趋势,但根系碳密度和土壤碳储量显著相关（R=0.98）。根系生物量、根系固碳量、土壤碳储量均随土壤深度增加呈递减趋势。

英文摘要：

In this experiment,free grazing plots and enclosure plots are selected on representative grassland in Chenbaerhu Banner.Samples have been taken by trench method.It aims at studying root system and carbon density and storage in soil under free grazing and enclosure condition.In condition of enclosure,underground carbon storage of Leymus chinensis steppe and meadow steppe was increased with significant difference.Underground carbon storage of Stipa capillata steppe increase without significant difference.The highest values of carbon sequestration in root system and carbon storage in soil are in enclosed meadow steppe with 79.74 g/m2 and 21 150.49 g/m2 respectively,and then the carbon sequestration in root system and carbon storage in soil are in enclosed Leymus chinensis steppe with 53.12 g/m2 and 14 643.65 g/m2 separately,and the ones in Stipa capillata steppe are the lowest with 47.90 g/m2 and 11273.52 g/m2 separately.Compared with the grazing plot,they have risen by 35.89%,50.17% and 3.74% respectively.Although carbon sequestration in root system only account for a slight part of carbon storage in soil,root system can play an important role on enhancing carbon source sequestration and storage as well as carbon accumulation through improving soil texture.There is no significant correlation between carbon sequestration in root system and soil carbon under free grazing（R=-0.61）.The root biomass in enclosure is also declining with the increase of soil depth,but the correlation between carbon sequestration in root system and soil carbon is significant（R=0.98）.The research indicates that the biomass of root system,carbon sequestration in root system and soil carbon storage decrease with the increase of soil depth.