退耕还林（草）对农牧交错区小流域景观格局的影响——以神木县六道沟小流域为例

为了解退耕还林（草）工程对黄土高原农牧交错区小流域土地利用及景观格局的影响，利用RS、GIS技术和景观生态学方法，选择景观格局指数，对研究区退耕还林（草）前（1995--2002年）后（2002--2010年）的土地利用和景观格局时空变化特征进行分析研究。结果表明：1）退耕还林（草）前，景观格局变化幅度较小，具体表现为研究区面积比例、聚集度指数以及各景观类型的变化幅度比较小，退耕还林（草）后，小流域景观格局发生了剧烈演变，具体表现为耕地面积比例急剧减小，林草地面积比例迅速增加以及斑块边界复杂性下降；2）1995--2010年，研究区景观蔓延度指数从46．26升高到47．54，多样性指数从1．67下降到1．65，从以耕地、草地和林地为主的景观生态系统转变为以草地和林地景观为主的景观异质程度较低的景观生态系统；3）退耕还林（草）工程是研究区景观格局良性演化的主要驱动力。

Effect of Grain for Green on the landscape pattern of small watershed in the farming crisscross region:A case study in Liudaogou Watershed

Based on the remote sensing images, the impact of the Grain for Green project on the spatial- temporal variability of land use and landscape pattern in the recent 15 years in the farming crisscross region on the Loess Plateau were analyzed using RS, GIS technology and landscape ecological methods. The results showed that the landscape pattern changed little before Grain for Green （1995 -2002） with the small range of A （percentage of land area） , IA （ aggregation index） and landscape patterns. After Grain for Green （2002 -2010） , small watershed landscape pattern occurred a dramatic evolution with the sharp decrease of the percentage of arable land, rapid increase of the percentage of forest and grassland area and the decrease of plaque border complexity. From 1995 （before Grain for Green ） to 2010 （after Grain for Green） , the contagion index increased from 46.26 to 47.54, and the landscape diversity index decreased from 1.67 to 1.65. The farmland, meadow and woodland matrix landscape ecosystem in 1995 changed into meadow and woodland matrix landscape ecosystem, with the lower heterogeneous landscape in the study area. Through the analysis of two phases of landscape pattern before and after the implementation of the Grain for Green, it can be concluded that Grain for Green campaign was the main driving force for positive evolution of the landscape pattern in the study area.