基于植被覆盖度的宁夏灵武白芨滩自然保护区防风固沙功能时空变化研究

基于MODIS-NDVI时序数据，利用像元二分模型估算宁夏灵武白芨滩自然保护区2000-2019年的年最大植被覆盖度，分析保护区整体及不同管理站范围的植被覆盖度（Fractional Vegetation Coverage，FVC）时空变化特征，并结合气象数据计算了2000-2019年该保护区生态系统防风固沙功能，并分析了其时空格局及其变化原因，结果表明：（1） FVC在季节和年尺度上均呈上升趋势，年增长量达0.013；不同阶段的植被覆盖类型变化明显，由第一阶段以低覆盖度类型为主逐渐转变为第五阶段以中覆盖度类型为主；（2）不同管理站范围的FVC变化趋势不同，其中甜水河管理站、大泉管理站、羊场湾管理站及长流水管理站西侧的FVC增长快，且拟合好；（3）该保护区潜在风蚀量、实际风蚀量均逐渐减少，防风固沙率逐渐上升，防风固沙功能逐渐增强，明显体现在第三、四、五阶段；（4）不同管理站范围的防风固沙功能均持续增强，其中大泉管理站的防风固沙率增幅最大，从第一阶段的53.39%升至第五阶段的74.44%，增幅达21.05%；临河白芨滩和马鞍山管理站防风固沙率增幅较小，分别为15.81%、15.50%。总体来看，保护区2000-2019年的FVC增幅显著，植被空间变化规律明显，防风固沙功能整体上呈逐渐增强，一定程度上说明了该保护区的生态保护建设成效显著。

Spatio-temporal variation of windbreak and sand fixation functions based on vegetation coverage in Baijitan National Nature Reserve, Ningxia

On the basis of moderate-resolution imaging spectroradiometer-normalized difference vegetation Index (MODIS-NDVI) time-series data, the maximum annual vegetation coverage from 2000 to 2019 was estimated using the pixel binary model. The temporal and spatial variation characteristics of the fractional vegetation cover (FVC) of Baijitan National Nature Reserve in Ningxia (hereafter the Nature Reserve) and different management stations were analyzed. Combined with meteorological data, the windbreak and sand fixation functions of the Nature Reserve ecosystem from 2000 to 2019 were calculated, and the temporal and spatial patterns and the changes of the functions were analyzed. Results showed that (1) the FVC exhibited an increasing trend on the seasonal and annual scales, and the annual growth reached 0.013. The vegetation type characteristics of different stages were obvious, i.e. from the first stage mainly with low cover, which accounted for 75.22% of the total area of the Nature Reserve, to the fifth stage mainly with medium cover, which accounted for 66.13% of the total area of the Nature Reserve. (2) The FVC change trends of different management stations were different, i.e. the FVC in the west of Tianshuihe, Daquan, Yangchangwan and Changliushui management stations grew fast and was well distributed. (3) The potential and actual wind erosion amounts of the Nature Reserve gradually increased in the first stage and significantly increased in the third, fourth and fifth stages. (4) The windbreak and sand fixation functions in different management stations continuously increased, and the increase rate in Daquan management station was the largest, from 53.39% in the first stage to 74.44% in the fifth stage, with an increase of 21.05%. In general, the FVC of the Nature Reserve increased significantly from 2000 to 2019, and the spatial variation of vegetation was significant. The windbreak and sand fixation functions were gradually enhanced, which indicated that the ecological protection construction of the Nature Reserve was remarkable.