中文摘要：

【目的】基于生态平衡视角，研究“退耕：还林还草”工程与能源重化工基地建设对陕西省榆林市碳源／汇平衡及其生态效应的影响过程与机制，以期为研究区制定碳减排与碳增汇政策提供科学依据。【方法】采用研究区能源消费统计数据、归一化植被指数（NDVI）、遥感数据、气象数据等，利用碳排放模型、CASA模型、固碳释氧模型等进行估算与分析。【结果】（1）2005--2009年，榆林市化石能源消费碳排放总量大幅增加，累计碳排放规模为8576．66×104t；原煤消费是最主要的碳源；神木县、府谷县、榆阳区的碳排放量合计占到整个区域的95％以上。（2）2005—2009年，榆林市逐年植被净第一性生产力（NPP）平均值呈小幅增加趋势，年均增加6gC·m-2，佳县、米脂县和子洲县一带NPP增长显著；榆林市NPP平均值表现出“南高北低、东高西低”的格局，低值区域集中在以榆阳区为中心的呈东北一西南走向的区域。（3）2005—2009年，榆林市植被累计固定11429．3×10。tCO：。（4）2005--2009年，总体上榆林市各年份碳固定总量均大于碳排放总量，且其差额逐年增加，呈现生态盈余等级升高的趋势；同时碳源／汇平衡与生态盈余特征存在显著内部空间分异，神木县、府谷县和榆阳区的生态盈余等级波动明显，生态状况逐年下降，是榆林市碳减排与碳增汇的重点区域。【结论】实施“退耕还林还草”工程，对增加植被碳汇作用显著，提高碳汇林比重是区域碳增汇的有效措施，对促使区域生态环境持续好转与减小生态压力具有现实意义。

英文摘要：

[ Objective ] From the perspective of ecological balance, this paper mainly studied the influences and mechanism of carbon source and sink and its ecological effect under the ＇Grain for Green Project ＇ and the key base construction of energy and chemical industry in Yulin so as to provide a scientific basis for reduction of carbon emission and increase of carbon sink. [Method] The estimation and analysis in this paper are based on carbon emission model, CASA model, carbon sequestration and oxygen release model as well as energy consumption statistics, MODIS-NDVI, meteorological data, etc.. [Result] Carbon emission of fossil energy consumption increased significantly in Yulin, with a cumulative emission of 8 576.66 1 oat from 2005 to 2009. Raw coal consumption was the main carbon source. The total carbon emission in Shenmu, Fugu and Yuyang counties accounted for more than 95% of the whole area. The mean value of NPP （net primary productivity, NPP） increased slightly at the average speed of 6 gC m2 each year from 2005 to 2009. NPP of Jiaxian, Mizhi and Zizhou counties grew significantly. The mean value of NPP showed a pattern of higher in the south and east, while lower in north and west and the regions which had lower value of NPP centered around Yuyang from northeast to southwest. The amount of CO2 fixed by vegetation was 11 429.3 × 104 t in Yulin from 2005 to 2009. Overall,the amount of carbon fixation was greater than that of carbon emission in Yulin from 2005 to 2009 and the differences would increase year by year, showing an increasing tendency of ecological surplus levels. Meanwhile, tile balance between carbon source and sink and its ecological surplus displayed significant space differences. Shenmu, Fugu and Yuyang counties were the major areas of reducing carbon emission and increasing carbon sink and its ecological surplus level fluctuated significantly and ecological state declined year by year. [Conclusion]The ＂Grain for Green Project＂ would help to increase carbon fixation significantly b