中文摘要：

为了探讨土地利用方式对土壤有机碳固定的影响，论文以乔木、灌木、草地和农田等不同植被类型，纯林和混交两种栽培模式的黄土台塬为研究对象，进行了土壤有机碳（SOC）和颗粒有机碳（POC）分析。结果表明：不同土地利用方式土壤SOC和POC在0～100cm土体中均存在差异，尤以0～40cm深度突出，其中灌木林地和天然草地在整个剖面上可积累更多的SOC和POC：不同土地利用方式土壤细颗粒有机碳（FPOC）含量、分配比例及其在剖面上的分布变化均小于粗颗粒有机碳（CPOC），在0～100cm土体中，CPOC敏感性指标分别为SOC、FPOC和POC总量的2．66～13．56、3．75～5．99和2．58～4．17倍；不同土地利用方式土壤SOC与POC极显著相关，耕地SOC与POC相关性相对较小，乔灌混交林地和乔木林地最大。因此，CPOC和FPOC均可作为衡量土地利用方式转变对于土壤影响的评价指标之一。

英文摘要：

In order to examine the effect of soil organic carbon sequestration under different land use types on the Loess Plateau, different vegetation types of arbor, shrub, grass and farmland, pure and mixed planting models were selected to analyze soil organic carbon, coarse particulate and fine particulate organic carbon. The results showed that： 1 ） Soil organic carbon concentration is different significantly in 0 -20 cm; in the 0 -5 cm, arbor-shrub mixed forestland and shrub forestland are higher than farmland by about 107% and 100%. 2） Particulate organic carbon concentration is different significantly in 0 -40 cm; in the 0 -5 cm, coarse particulate organic carbon concentration of natural grassland, shrub, arbor-shrub mixed and arbor forestland are higher than farmland by about 1097% , 1409% , 1271% and 865% ; in the 0 -5 cm, fine particulate organic carbon concentration of natural grassland, shrub, arbor-shrub mixed and arbor foresfland are higher than farmland by about 113% , 239% , 212% and 65% ; the proportion of particulate organic carbon is different obviously in 0 - 100 cm. Soil organic carbon and particulate organic carbon concentration and proportion of woodland and natural grassland in the whole 0 - 100 cm is more than farmland; shrub and natural grassland can get more accumulation of organic carbon and paniculate organic carbon in the whole profiles. 3 ） The change of land use type of coarse particulate organic carbon is more sensitive than the fine particulate organic carbon and organic carbon; in the 0 - 100 cm profile, sensitivity index of CPOC is 2.66 - 13.56,3.75 -5.99 and 2.58 -4. 17 times of SOC, FPOC and POC. 4） There is a very significant correlation between soil organic carbon and paniculate organic carbon; the correlation coefficient between soil organic carbon and particulate organic carbon of farmland is the smallest, natural grassland and shrub for- estland is larger, arbor-shrub mixed forestland and arbor forestland is the largest. Therefore, fine particulate and coarse pa