中文摘要：

2007年11月28日-12月1日对云雾山4类天然草地,以及不同生长年限的人工紫花苜蓿（Medicago stativa L.）草地、沙棘（Hippophae rhamnoides Linn.）灌木、农田进行土壤有机碳、全氮分布分析,以期为该地区的草地生态系统的合理利用和减排温室气体提供科学依据。结果表明：土壤有机碳、全氮含量的排序为：天然草地（人工草地（灌木（农田。对0-40 cm土壤每10 cm土层土壤有机碳、全氮含量测定发现：除9年生人工苜蓿草地在20-30 cm土层的有机碳含量相对10-20 cm无降低外,其他均表现为随土层深度的增加而依次降低。有机碳、全氮含量天然草地10-20,20-30,30-40 cm,以及5年、7年、9年人工草地土层之间差异水平基本达到显著水平。天然草地和人工草地土壤有机质含量与其全氮含量呈极显著线性相关（P〈0.01）。人工草地土壤有机碳,全氮含量随种植年限增长而增加,全氮含量增加程度大于有机碳。因此,云雾山天然草地有机碳、全氮含量最高,人工草地随着生长年限的延长也是碳氮积累的过程,农田含量最低,天然草地在碳氮储存方面发挥着更积极的作用。土壤有机碳、全氮在土壤表层（0-10 cm）含量最高,在云雾山地区通过退耕还草,加强植被恢复管理,有利草地生态系统的健康发展。

英文摘要：

Distribution of organic carbon（C） and total nitrogen（N） in different natural grassland,artificial Medicago stativa L.grassland with different growth years,Hippophae rhamnoides Linn.shrubland and farmland in Yunwu Mountain of the Loess Plateau were studied.Results show that the ranking of organic carbon and total nitrogen contents in four studied samples are： natural grassland〉artificial grassland〉shrubland〉farmland.As soil depth increased,except in the 10～20 cm of nine-year artificial alfalfa grassland,the contents of soil organic carbon and total nitrogen generally decreased in every 10 cm of 0～40 cm soil depth.The soil organic carbon and total nitrogen contents show significant differences among 10～20 cm,20～30 cm and 30～40 cm soil depth in all natural grassland types,and every 10 cm of 0～40 cm soil depth among 5,7,and 9 growth years for artificial alfalfa grassland.There is a significant linear correlation（P〈0.01） between soil organic carbon and total nitrogen in natural grassland and artificial grassland.In artificial grassland,the contents of organic carbon and total nitrogen increased with the growth years increased,and the increment of total nitrogen is higher than that of soil organic carbon.Therefore,natural grassland plays a more essential role for the accumulation of the soil organic carbon and total nitrogen contents.