[Change of vegetation ecological quality and the driving force in the Manas River Basin, China].

内容摘要

Ecosystems in inland river basins of arid regions are highly sensitive to climate change and human disturbance. Scientifically assessing the evolution of vegetation ecological quality and clarifying its driving mechanisms are crucial for regional ecological security and water resource management. We constructed a vegetation ecological quality index (VEQI) of Manas River Basin based on 250 m resolution remote sensing and meteorological data from 2000 to 2022. Using trend analysis, correlation analysis, and residual analysis, we examined the spatiotemporal variations of VEQI and quantitatively analyzed the driving effects and relative contributions of climate change and human activities. The results showed that vegetation in the Manas River Basin exhibited a significant improvement trend. During 2000-2022, the VEQI showed fluctuated increases with a rate of 0.4·a-1. Improved areas accounted for 55.1% of the total area, primarily concentrated in the mid- and downstream oases, while degraded areas were sporadically distributed in urban expansion zones and high-mountain areas. The multiple correlation between VEQI and climatic factors was generally positive (R=0.3). Although rising temperature led to an increase in vapor pressure deficit and intensified atmospheric water stress, the increase in precipitation and artificial water resource regulation effectively compensated for such negative effect, facilitating a macroscopic trend of ecological improvement. Human activities played a dominant role in vegetation evolution with a contribution rate of 61.3%, while climate change contributed 38.7%. However, the driving mechanisms exhibited significant spatial differentiation. Human activities dominated vegetation evolution in the mid- and downstream oases (contribution rate >90%), while climate change mainly affected the southern mountains and northern deserts (contribution rate >70%). Our results indicated that the ecological improvement in the Manas River Basin was essentially a fragile improvement model, highly dependent on water resource regulation and human intervention. This study provides important implications for future water resource management and regional ecological security. 干旱区内陆河流域生态系统对气候变化及人类干扰高度敏感,科学评估其植被生态质量演变规律并厘清其驱动机制,对区域生态安全和水资源管理至关重要。本研究以玛纳斯河流域为例,基于2000—2022年250 m分辨率遥感和气象数据,构建植被生态质量指数(VEQI),采用趋势分析、相关分析及残差分析等方法,揭示流域VEQI的时空演变特征,并定量分析气候变化和人类活动的驱动效应及相对贡献。结果表明:2000—2022年间,玛纳斯河流域内植被整体呈显著改善趋势,VEQI以0.4·a-1的速率波动上升,改善区域占研究区总面积的55.1%,主要集中在中下游绿洲,退化区零星分布于城镇扩张带及高山区。VEQI与气候因子的复相关整体呈正向(R=0.3),升温虽导致饱和水汽压差增大进而加剧大气水分胁迫,但研究期内降水增加与人工水资源调控有效代偿了这一负面效应,促成了宏观上的生态向好态势。人类活动在植被演变中起主导作用,贡献率达61.3%,气候变化的贡献率为38.7%;驱动机制存在显著空间分异,其中,人类活动主导了中下游绿洲植被的演变(贡献率>90%),气候变化主要影响南部山区和北部荒漠(贡献率>70%)。玛纳斯河流域的“生态改善”本质上是一种高度依赖水资源调控与人工干预的脆弱型改善模式,本研究结果对未来水资源管理和区域生态安全具有重要启示。.