摘要
摘要:荒漠植被是干旱半干旱生态系统重要的组成部分, 在维护生态系统平衡方面发挥着重要的作用。及时准确地监测新疆荒漠植被的时空分布变化, 对资源可持续利用及生态恢复具有重要应用价值。本研究基于AVHRR-NDVI和MOD13A2-NDVI数据集计算了新疆1989—2017年植被覆盖度, 通过对植被覆盖度划分阈值提取计算了荒漠植被的分布及面积, 并分析了其时空变化特征。通过土地利用转移矩阵计算新疆荒漠植被与非荒漠植被、裸地类型的转化情况。利用相关系数分析法定量分析了乌伦古河、叶尔羌河及阿克苏河3个典型流域影响荒漠植被演变的驱动因素。结果表明: 1989—2017年, 新疆荒漠植被总面积呈显著增加趋势, 线性增长率为3.09万hm²?a^?1。低覆盖度荒漠植被面积呈显著增加趋势, 线性增长率为3.22万hm²?a^?1; 高覆盖度荒漠植被面积基本不变。植被转化中, 高、低荒漠植被间转化面积50.85万hm², 非荒漠植被类型转变为荒漠植被341.24万hm², 荒漠植被转变为非荒漠植被类型191.25万hm²。通过对典型流域的研究分析得出降水是影响荒漠植被演变最主要的因素, 其次是径流量和政策因素, 气温对于荒漠植被的影响存在区域性差异。
关键词:新疆/
荒漠植被/
荒漠植被演变/
覆盖度/
生态系统
Abstract:Desert vegetation is an important part of arid and semi-arid ecosystems in Xinjiang and plays a key role in the maintenance of ecosystem balance. Timely and accurate monitoring of the temporal and spatial distribution of desert vegetation is important for the sustainable utilization of the resources and ecological restoration. Based on remote sensing technology combined with two Normalized Difference Vegetation Index (NDVI) products (AVHRR-NDVI and MOD13A2-NDVI), the area of desert vegetation in Xinjiang from 1989 to 2017 was estimated. The temporal and spatial characteristics of desert vegetation in three typical river basins (Ulungur River Basin, Aksu River Basin, and Yarkand River Basin) were analyzed, and the relationships between desert vegetation and the climate factors, runoff changes, and policy factors were discussed. The NDVI products were used to calculate the vegetation coverage ( f_c), and the distribution and area of desert vegetation were determined according to the threshold of vegetation coverage. Desert vegetation was determined within the f_c threshold range of 0.1–0.35, where 0.1–0.25 indicates low-coverage desert vegetation and 0.25–0.35 indicates high-coverage desert vegetation. The transformation between desert vegetation and other vegetation types was calculated using the land use transfer matrix to explore the evolution and transformation of desert vegetation in Xinjiang from 1989 to 2017. The driving factors of desert vegetation evolution in the three typical river basins were analyzed using correlation analysis. The results showed that the total area of desert vegetation in Xinjiang significantly increased from 1989 to 2017 at a rate of 30 900 hm²?a^?1. The area of low-coverage desert vegetation significantly increased at a rate of 32 200 hm²?a^?1; whereas the area of high-coverage desert vegetation did not vary, with a multi-year average value of 2 087 100 hm². The area of desert vegetation in northern Xinjiang increased slightly, accounting for 67% of the total area of desert vegetation. This was mainly due to an increase in low-coverage desert vegetation. The area of high-coverage desert vegetation in northern Xinjiang slighly decreased. The desert vegetation area in southern Xinjiang significantly increased. During vegetation transformation, 508 500 hm² of desert vegetation transformed from high to low desert vegetation, 3.4124 million hm² of non-desert vegetation types transformed into desert vegetation, and 1.9125 million hm² of desert vegetation transformed into non-desert vegetation types. This study of typical river basins showed that the area of desert vegetation increased with increasing precipitation. Precipitation was the most important factor affecting the evolution of desert vegetation, followed by runoff and policy factors. The influence of air temperature on desert vegetation varied across regions, and the area of desert vegetation near water increased with increasing temperature.
Key words:Xinjiang/
Desert vegetation/
Desert vegetation evolution/
Coverage rate/
Ecological system



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