1975-2020年疏勒河流域绿洲时空变化研究

掌握内陆河流域绿洲时空动态是内陆河流域实现水资源优化配置和动态管理的基本前提。基于Landsat系列数据，结合面向对象随机森林和目视解译方法，分析了1975-2020年疏勒河流域绿洲的时空格局、结构变化及其成因，并探讨了人工/天然绿洲比例变化对生态环境的影响。结果表明：（1）2020年疏勒河流域绿洲面积为5790.24km²，占流域面积比例的4.65%，其中人工绿洲、自然绿洲和过渡带分别占绿洲总面积比例为45.29%、51.07%和3.64%；（2）疏勒河流域绿洲分布模式主要为内陆河沙漠区模式和干流模式；（3）1975-2020年疏勒河流域绿洲面积整体上呈扩张趋势，且绿洲变化以人工绿洲扩张、天然绿洲和荒漠-绿洲过渡带减少为主要特征，土地类型的主要变化为草地和荒漠被开垦，绿洲变化可分为1975-2000年缓慢扩张和2000-2020年迅速扩张2个阶段，主要原因为流域径流量增加和外来移民输入；（4）随着人工与天然绿洲面积之比由3：7（1975年）增加到5：5（2020年），流域绿洲生态环境质量呈现先上升后下降趋势，2005年达到最高。研究可为疏勒河流域绿洲生态系统稳定发展提供数据支撑和科学依据。

Spatiotemporal change of oasis in Shule River Basin during 1975-2020

Grasping spatial-temporal dynamics of oasis in the inland river basin is the basic premise for realizing optimal allocation and dynamic management of water resources for the inland river basin. Shule River Basin, located in the west of Hexi Corridor, is a typical sensitive area in the fragile zone of ecosystem. In recent years, with the warming of the climate, the diameter flow out of the mountains has increased year by year, providing a good environmental background for the expansion of artificial oases and the restoration of natural oasis. Many scholars had carried out a lot of research work on ecological quality, service function and carrying capacity in this basin. However, there were relatively few studies on the spatio-temporal changes of oasis pattern and structure in long time series at watershed scale. Therefore, based on Landsat data of years 1975, 1990, 1995, 2000,2005, 2010, 2015 and 2020 combining object-oriented random forest and visual interpretation method, this paper analyzed the spatio-temporal pattern, structure change and causes of oasis in Shule River Basin from 1975 to 2020. And it also discussed the impact of artificial oasis area to natural oasis area ratio on the quality of ecological environment. The results showed that:(1) The total area of oasis was 5790.24 km² in the Shule River Basin in 2020, accounting for 4.65% of the total area of the basin, of which the artificial oases, natural oases and desert-oasis ecotone accounted for 45.29%, 51.07% and 3.64%, respectively; (2) The distribution patterns of oasis in Shule River Basin are mainly the inland river desert region model and the mainstream flow model. (3) The oasis area in Shule River Basin showed an overall trend of expansion from 1975 to 2020. The oasis changes were mainly characterized by the expansion of artificial oases and the decrease of natural oasis and desert-oasis transition zones. The main changes of land cover types were the reclamation of grassland and desert. And the land cover types of artificial oasis in Shule River Basin showed an increasing trend from 1975 to 2020. The oasis changes could be divided into two stages:slow expansion from 1975 to 2000 and rapid expansion from 2000 to 2020. (4) As the ratio of artificial to natural oases area increased from 3:7 (1975) to 5:5 (2020), the eco-environmental quality of oases increased firstly and then decreased, reaching the highest value in 2005. This study can provide data support and scientific basis for the steady development of oasis ecosystem in Shule River Basin.