长江上游退耕还林工程的农业生产和水环境效益评价——以四川省为例

Evaluation of "Grain for Green" Project's Effects on Agricultural Production and Water Environment in the Upper Yangtze River:A Case Study in Sichuan

退耕还林工程是我国大规模的土地利用方式的改变。以四川省为例,基于退耕还林工程实施后粮食产量、粮食作物播种面积、化肥用量以及水质和水土流失状况变化的分析,讨论了退耕还林工程对环境保护的贡献和可能存在的问题。退耕还林工程导致粮食作物播种面积、粮食产量和化肥用量的减少,在退耕还林工程实施前,这三者之间有很好的相关性,但自工程实施后,这三者的下降幅度与退耕还林面积的增加幅度有较大的差异。几种原因可能造成这种不一致性,值得进一步研究。退耕还林工程实施后河流径流量、泥沙含量以及输沙量的下降充分证实了退耕还林工程对长江上游水土保持的重要贡献,同时进一步证实长江上游的泥沙主要来源于坡耕地的耕作。

＂Grain for Green＂ Project in China involves large-scale land use/cover change. Implementation of this project causes reduction in grain production and chemical fertilizer consumption as a result of declining croplands. Based on data of sown areas, grain production, consumption of chemical fertilizers of Sichuan and the runoff, sediment data from the upper Yangtze River, the ＂Grain for Green＂ project is revisited. The result indicates that the ＂Gain for Green＂ project has contributed considerably to reducing sediments and runoff in the upper Yangtze River. The data have also revealed disparities among the sown areas, grain production and consumption of chemical fertilizers which were statistically closely correlated prior to the project but not so since the implementation of the project. Apart from other reasons, false figures of land areas under the project might be an important factor contributing to the disparities.