玛纳斯河流域耕地时空变化及其生态环境效应

Temporal and spatial changes of cropland and its ecological environment effects in Manas River watershed

以干旱区典型流域一玛纳斯河流域为研究区，利用1976、1989、20005年三期遥感影像结合GIS软件，探查近30年玛纳斯河流域耕地时空变化及其生态环境效应。结果表明：该流域耕地资源在时间和空间上都发生了较大的变化。耕地总量在不断增加，由1976年3418．71km^2增至2005年5907．62km^2，且1989—2005年间耕地年均增长较1976—1989年更快。矩阵分析则表明了耕地的增加是依靠开垦草地与盐碱地。耕地的减少主要是由于建设占用耕地、耕地撂荒转变为盐碱地或沙地以及退耕还林。空间上流域耕地范围扩大，在绿洲区分布趋于连片，而绿洲边缘的耕地破碎性有所增强，耕地成为流域最主要的景观。由于耕地的不断扩大，致使流域生态环境发生了剧烈的变化，出现了如尾闾湖干涸、草场退化、土地退化、生物多样性降低等一系列的生态环境问题。

The arid continental river watersheds of northwest China, have been damaged to different degrees in long term drought and water shortage, and especially formed a arid land use/land cover pattern. This research studied cropland changes and its ecological environment effects in a watershed of arid area - Manasi river watershed in last 30years since 1976a, by using GIS with remote images in 1976a, 1989a, and 2005a. The results showed that the universal change of cropland changed mostly in the watershed. Area of cropland and residence land increased continually, from 3418.71km^2 in1976 to 5907.62km^2 in 2005. The significant spatial expansion in cropland led to rapid decrease of grassland and saline - alkali land. The decrease of cropland was mainly due to cropland abandoned, mandatory conversion of cropland to forestland and grassland, desertification and salinization, et al.. The distribution of cropland inside of oasis was more centralized and the fragmentation became lower, but to the cropland near edge, its fragmentation increased. Some unreasonable rapid expansions of cropland had brought the land coverage changes exerting enormous influence on the eco - environmental, including land desertification, the vegetation destroy, the area of saline land and sand land was enlarged quickly, et al. ,which made the eco -environmental more fragile in the region, will take bad effect to the local people.