青藏高原不同退化梯度下植被蒸散发的时空格局研究

全面深入地了解青藏高原蒸散发与植被退化的关系对陆地生态系统的稳定有十分重要的意义。本文选取MODIS16A2数据分析青藏高原及其14 个子流域蒸散发的时空格局，同时选用MODIS NDVI及GIMMS NDVI3g数据采用像元二分模型计算青藏高原植被覆盖度，进而识别青藏高原植被退化梯度和植被变化区，以此探究2001—2020 年青藏高原不同退化梯度和不同植被变化区蒸散发的变化趋势。结果表明：2001—2020 年青藏高原蒸散发呈波动上升趋势，空间上呈中部低，东南高的态势，14 个子流域中羌塘高原区的蒸散发最高，黄河流域的蒸散发最低，同时大部分地区蒸散发未来将呈现下降趋势。青藏高原各植被类型中灌木的蒸散发最高，其次是森林和草地。2001—2020 年青藏高原植被退化不断减弱，各退化区蒸散发的均值排序为：未退化区>轻度退化区>极重度退化区>中度退化区>重度退化区。青藏高原植被恢复区集中在青海湖和柴达木盆地周边区域且植被恢复区面积高于植被恶化区，各植被变化区的年均蒸散发呈波动上升趋势，总体呈植被恢复区>植被不变区>植被恶化区。识别青藏高原植被退化梯度及植被蒸散发的时空特征能为当地生态安全格局构建和高寒植被退化的恢复治理提供参考。

Spatial and Temporal Patterns of Vegetation Evapotranspiration under Different Degradation Gradients in the Qinghai-Tibet Plateau

A comprehensive and in-depth understanding of the relationship between evapotranspiration and vegetation degradation in the Qinghai-Tibet Plateau is of great significance to the stability of terrestrial ecosystems. In this paper,MODIS16A2 data was selected to analyze the temporal and spatial patterns of evapotranspiration in the Qinghai-Tibet Plateau and its 14 sub-watersheds. At the same time,MODIS NDVI and GIMMS NDVI3g data were selected to calculate the vegetation coverage of the Qinghai-Tibet Plateau using a pixel binary model,identify the vegetation degradation gradient and vegetation change areas on the Qinghai-Tibet Plateau,and to explore the changing trend of evapotranspiration in different degradation gradients and different vegetation change areas of the Qinghai-Tibet Plateau from 2001 to 2020. The results showed that:from 2001 to 2020,the evapotranspiration from the Qinghai-Tibet Plateau showed a fluctuating upward trend,with a trend of low in the middle and high in the southeast. Among the 14 sub-basins,the evapotranspiration in the Qiangtang Plateau was the highest,and that in the Yellow River Basin was the lowest. Regional evapotranspiration would show a downward trend in the future. Among all vegetation types on the Qinghai-Tibet Plateau,shrubs had the highest evapotranspiration,followed by forests and grasslands. From 2001 to 2020,the vegetation degradation on the Qinghai-Tibet Plateau continued to weaken. The average evapotranspiration in each degraded area was ranked as follows:non-degraded area > mildly degraded area > extra severely degraded area > moderately degraded area > severely degraded area. The vegetation restoration areas on the Qinghai-Tibet Plateau were concentrated in the surrounding areas of Qinghai Lake and the Qaidam Basin,and the area of the vegetation restoration areas was higher than that of the vegetation deterioration areas. Area > Vegetation Deterioration Area. Identifying the temporal and spatial characteristics of vegetation degradation gradient and vegetation evapotranspiration on the Qinghai-Tibet Plateau can provide a reference for the construction of the local ecological security pattern and the restoration and management of alpine vegetation degradation.