高寒草地生长季/非生长季植被盖度遥感反演

植被盖度是刻画陆地生态系统植被覆盖的重要生态参量。以当雄县Landsat-8OLI为数据源，从10种常用植被指数中筛选出适合反演高寒草地生长季/非生长季草地植被盖度的植被指数，引入像元三分法确定端元特征值，通过不同植被指数基于像元二分模型反演植被盖度的对比分析，确定适合生长季/非生长季植被盖度最优植被指数，根据反演结果分析了研究区草地生长季/非生长季植被盖度的时空变化特征。结果表明：1）由可见光-近红外波段构建的植被指数适用生长季植被盖度反演，由短波红外构建的植被指数适用于非生长季植被盖度反演。2）基于MSACRI的像元二分模型适合非生长季植被盖度反演，基于NDVI的像元二分模型则最适用于生长季植被盖度的反演。3）研究区草地植被盖度随海拔增加呈现先增加后减少的单峰变化格局，草地集中分布于海拔4300~5100 m处。生长季植被盖度主要集中于20%~80%，非生长季绝大部分的草地盖度小于40%。研究结果可为草地生态系统碳存储、植被生产力、土壤侵蚀、生态水文等研究提供参考依据。

Remote sensing estimation of vegetation cover in alpine grassland in the growing and non-growing seasons

Vegetation cover is an important ecological parameter for describing vegetation status of terrestrial ecosystems. Using Landsat-8OLI data for Dangxiong County as the data source， the most suitable vegetation index for estimation of vegetation cover in Alpine Grassland in the growing and non-growing seasons was selected from 10 commonly used vegetation indices. A three-pixel linear mixed model was used to estimate the end element values. The optimal vegetation index for inversion of vegetation cover in the growing and non-growing seasons was determined by comparison of results obtained using the different vegetation indices， based on the pixel bisection model. The selected model was then used to analyze the temporal and spatial distribution of vegetation cover in the growing and non-growing seasons. The results showed that： 1） A vegetation index constructed from the visible-near infrared band performed best for the inversion of vegetation cover in the growing season， and an index constructed from the shortwave infrared was suitable for the inversion of vegetation cover in the non-growing season. 2） The modified soil-adjusted corn residue index （MSACRI） pixel dichotomy model was the best model to invert the vegetation cover in the non-growing season， and the normalized difference vegetation index （NDVI） pixel dichotomy model was the best for inversion of the vegetation cover in the growing season. 3） Across a gradient of increasing altitude， the vegetation cover presented a single-peak pattern with the peak at mid-altitude. Grassland was mainly found at 4300-5100 m above sea level. The vegetation cover in the growing season typically ranged from 20% to 80%， while cover in the non-growing season was mostly less than 40%. This research results provides reference data for studies on grassland ecosystem carbon storage， vegetation productivity， soil erosion， and ecological hydrology.