新疆渭干-库车河流域土地利用变化空间耦合及其生态效应

Change in Land Use and Its Consequence for Ecological Systems in Weigan-Kuqa River Basin in Xinjiang

土地利用/覆盖变化已成为全球生态环境变化研究不可缺少的部分。由于全球变暖以及人类活动对水土资源利用强度加大,1990年以来,位于新疆干旱区的渭干-库车河流域水资源和生态问题突出,生态环境与经济发展之间的用水矛盾不断加深。【目的】土地利用/覆盖变化被认为是全球环境变化的主要原因之一,随着社会的快速发展,耕地的扩张,水资源的匮乏导致渭干-库车河的生态环境愈发脆弱,严重威胁到流域的生态安全。兹以渭干-库车河流域为研究区,探讨渭干-库车河流域土地利用变化条件下的绿洲生态效应。【方法】采用土地利用动态度、土地利用结构信息熵和均衡度方法,结合生态系统服务价值基于1990-2014年TM遥感影像目视解译,从空间耦合角度分析了渭干-库车河流域土地利用变化及其生态效应。【结果】1990-2014年,渭干-库车河流域土地利用变化显著,耕地变化十分明显,增长率为53.10%,草地面积以255.70 km^2/a的速度减少,减少了近23.44%。新增耕地主要源于草地和未利用地,这一现象在渭干河中游和库车河下游区域最为明显。信息熵和均衡度均有所上升,伴随着人口数量的增加,土地利用程度不断提高,绿洲的扩张致使研究区生态服务价值25 a内下降19.78%。绿洲系统不稳定性也有所升高,对渭干-库车河流域的生态安全造成威胁。【结论】在全球变暖背景下,随着耕地面积的扩张,生态服务价值不断下降,导致渭干-库车河流域生态逐渐恶化,加剧草地退化,甚至引发沙漠化问题,严重危及绿洲系统安全与稳定,对渭干-库车河流域的生态安全和可持续发展造成了极大威胁。

【Background】Land use change and its determinants are important in understanding the global environment change and have attracted increased attention over the past few decades.Exacerbated by global warming and exploitation of water and soil since 1990,water resource scarcity and ecological system deterioration in Weigan-kuqa River Basin has become a major issue in Xinjiang Uygur Autonomous Region.The conflict between protecting ecosystem functions and developing economy raised concern.With the rapid socioeconomic development and the consequent increase in anthropogenic activities,a significant part of grasslands and vacant lands in this basin had been converted to cropland.This has substantially increased the demand for the already dwindling water resource,making the local ecosystems even more fragile.【Objective】The objective of this paper is to study the change in land use and vegetation coverage as well as its consequence for ecology in oasis in the Weigan-Kuqa River Basin in order to improve water resource use efficiency and develop sustainable land use in this region.【Method】The data used in the analysis were derived from visual interpretation of the Landsat TM remote sensing imageries at resolution of 30m from 1990 to 2014,and accuracy of the data was verified against ground-truth data.Spatiotemporal change in land use and vegetation coverage as well as their ecological consequence were analyzed based on the land use dynamic index,entropy and equilibrium degree of the land use structure,and the ecosystem service value.【Result】Land use in the basin had changed greatly from 1990 to 2014,with the croplands increasing at 53.1%at rate of 255.70 km2/year and the grasslands reducing by 23.55%.The greatest change was in the middle reaches of the Weigan River and the downstream reaches of the Kuqa River,where significant parts of grasslands and vacant lands had been converted to arable land.It was also found that the information entropy and equilibrium,along with the population,both had increased,with the expansion of the oasis reducing the ecological service value by 19.78%from 1990 to 2014.However,the oasis had become increasingly unstable,endangering ecological security of the basin.【Conclusion】Along with global warming,converting grasslands and vacant lands to farmlands had reduced the ecological service value and given rise to ecological degradation in the basin.This had aggravated grassland degradation and even led to desertification,endangering safety and stability of the oasis and the ecological security and sustainable development of the basin.