生态植被建设对黄土高原农林复合流域景观格局的影响

自1999年以来,黄土高原大规模地实施了退耕还林工程,生态环境呈显著恢复态势。采用2002年和2008年两期Spot5遥感影像,评估了退耕还林工程实施前后黄土高原典型农林复合流域土地利用与景观格局的动态变化。结果表明:在退耕还林工程实施的驱动下,流域土地利用变化剧烈,总变化率高达36.77%,主要变化的土地利用类型包括耕地、果园、幼林地、林地等。28.95%的耕地转为其他土地利用类型,其中48.83%转为果园,44.69%转为幼林地。景观格局变化呈明显的空间分布规律,山腰缓坡区以转化为果园为主,中、高海拔多转化为幼林地。退耕后流域生态景观得以优化,呈现良好发展态势。

Impact of ecological vegetation construction on the landscape pattern of a Loess Plateau Watershed

Due to loose soil property and sparse vegetation coverage, the Loess Plateau is a famous soil erosion region in China or even the world. Although widespread ecological restoration efforts have been devoted in past decades, little progress could be seen in the loess region as a result of its unique natural environments. The ecological environment has not been significantly restored until 1999 with the introduction of the Grain for Green Project. As the largest program in history to restore ecological environment, this project has attracted the participation of huge number of farmers. Furthermore, it has involved the most extensive area and the largest amount of domestic investment and as a result, the degraded ecological environment has been gradually restored. With the implementation of the project, it is expected the land use/landscape has been changed accordingly. Prior studies have widely investigated the spatial-temporal dynamics and their driving forces of landscape patterns in medium-to-large watersheds by analyzing Landsat TM remote sensing data. In contrast, studies on landscape patterns in small watersheds through high-resolution remote sensing images are lacking, in particular on the land use dynamics resulted from various ecological restoration projects. Up to now, the Grain for Green projects has been implemented for more than 10 years, and it is now in the benefit consolidation phase. Therefore, an urgent need at present is to quantitatively evaluate the impacts of the ecological restoration project on land use change and landscape patterns through remote sensing and GIS techniques, with which to provide guidelines for future policies and decision making. Based on the Luoyugou watershed in Tianshui (Gansu Province), this study evaluated the dynamic changes of land use and landscape patterns between 2002 and 2008 by analyzing Spot5 remote sensing images. The results show that its land use and landscape patterns have been substantially changed due to the implementation of the Grain for Green project, with a total change of 36.77%. Major changed land use categories were cropland, orchards, young forest plantation, and forestland. In particular, 28.95% of the cropland had been converted to other land use patterns during the study period, of which, 48.83% had been converted to orchards and 44.69% to young forest plantation. The changes of landscape patterns showed an obvious spatial distribution, with most of the gentle slope regions being converted to orchards and the medium-to-high altitudes mainly to young forest plantation regions. After the implementation of the Grain for Green project, the ecological landscape in the Luoyugou watershed has been greatly improved, indicating a good sign for future development.