20a来延安示范区土地利用景观格局动态分析

Landuse Pattern Dynamic Changes Over Last 20 Years in Yan'an Demonstration Area

利用1986,1997和2006年的TM影像,获取延安示范区土地利用基础数据。分析了研究区20a来各土地利用景观类型的数量变化特征,并从水土保持角度出发,从土地利用结构相对合理性、平均斑块面积、斑块粒级结构、面积分布标准差等方面对耕地、草地和林地的斑块变化进行了分析评价。(1)1986年以来,耕地呈减少趋势,1997—2006年间减少幅度较大;草地、林地和居民点及工矿用地呈增加趋势,1997—2006年间增加幅度较大;(2)土地利用结构有所好转,但总体格局没变,25°以上仍分布较多的坡耕地;(3)耕地破碎度增加,分布更加零散,草地更加集中连片分布,林地中小斑块数量增加较多,斑块数量结构差异更加明显。

The landuse information was extracted from the remotely sensed imagery in the years of 1986, 1997, and 2006, automatically. Based on the thematic maps, the quantitative change over last 20 years was analyzed. At the same time, the indexes of the relative rationality of the landuse structure, mean patch area, patch particle fraction structure, and patch area standard deviation were used to analyze and evaluate the patch changes of the cropland, grassland, and forest. Analyses indicate that （1） cropland has decreased since 1986 and the decreased range was larger during the period from 1997 to 2006. On the other hand, grassland, forest, residence, and industry increased and the change range was larger from 1997 to 2006. （2） Landuse structure was improved, but the general pattern did not change. More cropland was distributed on the slope greater than 25 degrees. （3） The cropland fragmentation was continuously rising and its distribution was more dispersed. Otherwise, the distribution of grassland was more concentrated and more continuous. The small and middle patch numbers of forest largely increased, which resulted in the more obvious difference in the patch quantity structure.