中文摘要：

对宁夏干旱区的沙枣一芨芨草群落进行调查，分析土壤有机碳含量与地下生物量、土壤水分等因子的关系，以及土壤有机碳的积累机制．结果表明：在沙枣．芨芨草群落中，随着土层深度的增加，土壤有机碳含量逐渐减少，且在水平和垂直方向上的变化格局较为平缓．不同区位土壤有机碳含量与其影响因子的相关性具有明显差异．0～30cm层中，土壤有机碳含量与土壤含水量呈显著负相关；60～150cm层中，土壤有机碳含量与根系生物量及土壤含水率呈显著正相关．经偏回归分析，0～30cm层土壤中芨芨草根系生物量密度对土壤有机碳含量具有显著贡献；60～150cm层中土壤有机碳格局主要受沙枣根系和土壤含水率的影响；而30～60cm层土壤有机碳含量与根系生物量密度和土壤含水率的关系不显著．在沙枣-芨芨草群落内，不同层次、不同区位的土壤有机碳积累机制具有明显的差异．

英文摘要：

An investigation was conducted to study the relationships of soil organic carbon （SOC） content with root biomass and soil moisture content as well as the accumulation mechanisms of SOC under the Elacagnus angustifolia-Achnatherurn splenden community in Ningxia Hui Autonomous Re- gion of Northwest China. The results showed that the SOC content decreased gradually with increas- ing soil depth, and changed gently in both horizontal and vertical directions. The correlations of the SOC content and its affecting factors varied with soil depth. In 0-30 cm layer, the SOC content was significantly negatively correlated with soil moisture content; in 60-150 cm layer, the SOC content was significantly positively correlated with soil moisture content and root biomass. Partial regression analysis indicated that the root biomass density in 0-30 cm soil layer contributed significantly to the variance of SOC content. In 60-150 cm layer, the SOC content was mainly affected by root system and soil moisture content; in 30-60 cm layer, no significant correlations were observed between the SOC content and the root biomass and soil moisture content. There was an obvious difference in the accumulation mechanism of SOC in different soil layers A. splendens community. and at different locations of E. angustifolia-