近20 a新疆南部植被覆盖度时空特征及对气候因素的响应——以塔什库尔干塔吉克自治县为例

植被覆盖度是反映生态环境质量的评价指标,掌握植被覆盖度的变化有助于实现生态文明建设与区域农牧业规划及生态环境保护。基于2001—2020年归一化植被指数（Normalization difference vegetation index,NDVI）,以耕地、林地、草地植被类型为研究对象,采用混合像元二分模型计算植被覆盖度,应用空间稳定性分析、Sen+Mann-Kendall空间趋势分析、线性回归等方法,分析塔什库尔干塔吉克自治县植被覆盖度的时空特征;同时,结合气温、降水量数据,利用Spearman相关分析、GIS空间分析等方法,分析气候因素对植被覆盖度的影响。结果表明：（1） 近20 a植被覆盖度以中植被覆盖区为主,植被覆盖度减小了4.79%。（2） 植被覆盖度的空间稳定性波动较小,以波动变化（37.3%）、中等波动变化（32.7%）为主;植被覆盖度呈显著减少和不显著减少面积分别占总面积的3.8%、54.5%。（3） 耕地、林地、草地植被状况均呈现不同程度的轻微退化,在植被覆盖度上分别减少了4.57%、6.32%、4.24%,在空间稳定性上,不显著减少分别为51.28%、54.48%、52.29%。（4） 2001—2020年耕地比林地、草地空间稳定性和退化程度更为稳定和缓慢,林地退化比耕地、草地严重。研究区植被覆盖度变化较小,呈微弱下降趋势,人类活动是影响植被生长的主要因素。

Temporal and spatial characteristics of fractional vegetation coverage and its response to climatic factors in southern Xinjiang in recent 20 years: A case of Taxkorgan Tajik Autonomous County

Fractional vegetation coverage (FVC) is an evaluation index that reflects the quality of the ecological environment. Understanding changes in fractional vegetation coverage is a critical part of developing a more ecological civilization, as well as regional agriculture, animal husbandry planning, and environmental protection. Based on the normalized difference vegetation index from 2001 to 2020, and taking into consideration the types of vegetation on cultivated land, forested land, and grassland, the mixed pixel dichotomy model is used to calculate fractional vegetation coverage. The spatial and temporal characteristics of fractional vegetation coverage in Taxkorgan Tajik Autonomous County of Xinjiang, China are analyzed using methods of spatial stability analysis, Sen+Mann-Kendall spatial trend analysis and linear regression. At the same time, combined with temperature and precipitation data, the impact of climate factors on FVC is analyzed using Spearman correlation analysis and GIS spatial analysis. The results showed that (1) over the past 20 years, fractional vegetation coverage was concentrated in the middle fractional vegetation coverage area, and fractional vegetation coverage decreased by 4.79%. (2) The spatial stability of fractional vegetation coverage fluctuated slightly, with fluctuations (37.3%) and moderate fluctuations (32.7%); The fractional vegetation coverage decreased both significantly and not significantly, with decreases of 3.8% and 54.5% of the total area, respectively. (3) The vegetation status of cultivated land, forested land, and grassland showed slight, varying degrees of degradation. Fractional vegetation coverage decreased by 4.57%, 6.32%, and 4.24% respectively. In terms of spatial stability values, which were 51.28%, 54.48%, and 52.29%, respectively, there was no significant reduction. (4) From 2001 to 2020, degrees of spatial stability and degradation on cultivated land were slower and more stable than on forested land and grassland, and forested land saw more significant degradation than cultivated land and grassland. Changes in fractional vegetation coverage observed in the study area were small and showed a slight downward trend. Human activity was the main contributing factor affecting vegetation growth.