基于斑块层次的土地利用变化对土地质量影响的初步分析——以河北省张北县为例

利用SPOT2/4、SPOT5 等遥感数据源, 以人工目视解译为主, 分析了1999 年到2003 年河 北省张北县土地利用( 耕地) 变化情况; 运用GIS 和统计分析的方法, 初步分析林草地转变为耕 地、耕地转变为林草地和未变化耕地斑块等的土地退化特征。从1999 年到2003 年, 张北县耕地 减少20229.5ha, 耕地的主要流向为林草地, 其中又以旱地转化为人工草地为主, 2003 年新增耕 地的主要来源为牧草地。除耕地转为疏林地外, 耕地转为林草地的其余类型未退化斑块的面积较 大; 林草地转化为耕地的情况比较复杂: 林地转化为旱地、牧草地转化为水浇地的斑块发生了比 较明显的土地退化; 而牧草地转化为旱地、其它土地转化为旱地、牧草地转化为菜地斑块中退化 斑块数和面积比例都不大。和未变化耕地斑块的退化特征比较, 旱地转化为牧草地, 退化斑块与 未退化斑块数量比例比较接近, 但未退化斑块面积比例远远高于未变化耕地斑块; 而牧草地转为 旱地的退化与未退化斑块数量和面积比例没有明显差别。旱地转化为林地的未退化斑块数量和 面积比例要大于林地转化为旱地的斑块。说明旱地向林草地转化有助于提高区域土地质量。

The Effects of Land Use Change on Land Quality at Patch Scale &mdash|A Case Study in Zhangbei County, Hebei Province

Huge press on natural resources and environment in China requires the study of the regional land quality pertinent to land degradation.Land use,which is exhibited as patches in space,has a close relationship with land quality.The research of the relationship between land use and land quality at patch scale can improve our under standing of the effects land use changes on land quality.The Ministry of Land and Resources implemented "Remote Sensing Monitoring on Land Resources and Eco-environment in Area around Beijng" and "Remote Sensing Monitoring Study for Distribution of Cultivated Farmland and Grain for Green in Typical Regions around Beijing" projects from 2002 to 2004.With the help of the project's achievements,the cultivated farmland changes in Zhangbei County,Hebei province,from 1999 to 2003 were analyzed by using the SPOT2/4 and SPOT5 remote sensing data.The degradation character of changed patches from cultivated land in 1999 to grassland and forest land in 2003,from grassland and forest land in 1999 to cultivated land in 2003 and unchanged cultivated land were analyzed by the application of GIS and statistical methods.The cultivated land decreased by 20229.5ha in 2003 compared to 1999,most of which turned into grassland and forest land,and the main type is the change of farmland to man-made grassland.The most of newly increased cultivated land came from grassland.The area of un-degraded patches in all types from cultivated land to grassland and forest land,except the change from farmland to low-density forest land,are larger than degraded patches,indicating these change types could lead to a higher land quality.The changed patches from forest land to farmland and from grassland to irrigated farmland have an obvious degradation inclination;however,the proportion of changed patches' area and quantities from grassland to farmland,from other land to farmland and from grassland to vegetable land is not large.Compared to un-changed cultivated patches,the area proportion of undegraded patches to total changed patches from farmland to grassland is larger and the quantity proportion is similar;the area and quantity proportion from farmland to grassland is not different largely.Both area and quantity proportions of un-degraded patches from farmland to forest land are larger than those from forest land to farmland.These results indicate the transition from farmland to forest land and grassland can improve the regional land quality.