明晰三江源国家公园(唐北区域)2000—2023年草地植被覆盖度(FVC)的变化规律与分布格局,量化不同FVC的草地植被动态变化情况,探究植被覆盖变化与降水量变化之间的相关性,可为该区域的草地生态保护与可持续发展提供科学依据。以MODIS的NDVI指数产品为数据源,结合布设的草地样地,测量草地FVC,并提取样地对应的NDVI值作为模型变量,采用回归分析拟合地面数据与遥感数据,选择最优方程反演研究区近20年(2000—2023年)的FVC。结果表明:1)高植被覆盖度草地主要分布在研究区的东南部。2)草地FVC总体呈改善趋势,高、中高植被覆盖度的草地面积占比呈增高趋势,同比分别增长65.14%和15.77%,中、中低和低植被覆盖度草地的面积占比呈降低趋势,同比分别降低18.87%、26.24%和18.45%。3)FVC在一定程度上受降水量变化的影响,其中,高、中高植被覆盖度草地面积占比的变化与年降水量呈现正相关,皮尔逊相关系数分别为0.37和0.28,中、中低和低植被覆盖度草地面积占比的变化与年降水量呈负相关,皮尔逊相关系数分别为0.34、0.31和0.12。2000—2023年三江源国家公园(唐北区域)草地生态状况显著改善,高、中高植被覆盖度草地面积大幅增加,中低及以下植被覆盖度草地面积缩减,反映出生态保护与修复工程的积极成效。植被覆盖变化与降水量呈现显著相关性,除低植被覆盖度草地外,其他草地对降水增加的响应较为敏感。

To clarify the spatiotemporal changes and distribution patterns of grassland fractional vegetation cover(FVC)in the Three-River-Source National Park(Tangbei Area)from 2000 to 2023,we quantified the dynamic variations in grassland vegetation under different FVC levels,and explored the correlation between vegetation changes and precipitation variations the sake of for grassland ecological conservation and sustainable development in the region.Using MODIS NDVI products as the data source and combining them with field measurements from established grassland plots,the corresponding NDVI values were extracted as model variables.Regression analysis was employed to fit ground-based measurements with remote sensing data,and the optimal equation was selected to invert FVC in the study area over the past two decades(2000-2023).The results indicate that:(1)High-FVC grassland vegetation is primarily distributed in the southeastern part of the study area.(2)Grassland FVC shows an overall improving trend.The proportion of high and medium-high FVC grassland areas increased by 65.14% and 15.77% respectively,while the proportion of medium,medium-low,and low FVC grassland areas decreased by 18.87%,26.24%,and 18.45% respectively.(3)Vegetation coverage is influenced to some extent by precipitation variations.The proportion of high and medium-high FVC grassland areas shows a positive correlation with annual precipitation(Pearson correlation coefficients of 0.37 and 0.28 respectively).In contrast,the proportion of medium,medium-low,and low FVC grassland areas exhibits a negative correlation with annual precipitation(Pearson correlation coefficients of 0.34,0.31,and 0.12 respectively).From 2000 to 2023,the ecological condition of grasslands in the Three-River-Source National Park(Tangbei Area)improved significantly.There was a substantial increase in high and medium-high FVC grassland areas and a reduction in medium-low and low FVC grassland areas,reflecting the positive effects of ecological protection and restoration projects.Additionally,vegetation changes exhibited a significant correlation with precipitation.Grasslands of different coverage levels,except for low-FVC areas,showed a sensitive response to increased precipitation.