在分析了六盘山林区典型生态系统碳循环规律的基础上，结合碳汇/源的概念，综合评价了土地利用 变化对生态系统碳汇功能的影响。分析得出陆地生态系统碳汇/源功能体现在碳库的贮量、稳定性和碳库的输入 与输出强度方面；天然次生林和人工林生态系统的碳贮量汇功能较强，农田和草地较弱；土壤有机碳过程源/汇 方面，天然次生林生态系统是强汇，人工林生态系统是弱汇，草地和农田生态系统是源。提出增加生态系统碳 汇功能的措施包括增加生态系统碳输入、减少输出和增强碳库的稳定性。

Based on the analyzing of the carbon cycle under different ecosystem in Liupan mountain forest zone and the conception of carbon sink and source , the impacts of land use change on the carbon sink of ecosystem were assessed. It is found that the function of ecosystem carbon source or sink under different land uses includes carbon storage, input and output of ecosystem carbon pool, net change of carbon storage and stabilization of soil organic carbon (SOC). The ecosystem carbon storage under natural secondary forest or plantation ecosystem is higher than that under cropland or rangeland ecosystem . The storage of ecosystem carbon, SOC, active SOC pool, slow SOC, protected and unprotected fraction of SOC and labile fraction of SOC under secondary forest or plantation ecosystem are higher than those under cropland and rangeland ecosystem. Natural secondary forest ecosystem is strong carbon sink, while plantation ecosystem is weak carbon sink, and cropland or rangeland ecosystem is source. The measures of increasing ecosystem sink include increasing input of ecosystem carbon pool, decreasing output of ecosystem carbon pool and increasing stabilization of SOC in ecosystem.