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.