Spatio-Temporal Evolution of NPP in Helan Mountain from 2012 to 2021 Based on MODIS Satellite Data

In order to evaluate the methods and results of remotely sensed estimation of net primary productivity (NPP) in Helan Mountain, this article uses the MODIS NPP product data and land cover type product from years of 2012–2021 to analyze the ecological quality changes of the Helan Mountain Nature Reserve. The results showed that (1) the mean value of NPP in the study area decreases from 145.68 gC/(m2·a) in 2012 to 122.77 gC/(m2·a); the mean NPP of Helan Mountain from 2012–2021 is 141.32 gC/(m2·a); the total NPP changes in the range of 1.46~1.96 TgC/(m2·a); the NPP is slowly decreasing during 2016 and showed an opposite trend during 2016–2019; (2) The Helan Mountain is mainly covered by annual herbaceous vegetation followed by evergreen coniferous forest, and the area of annual herbaceous vegetation reaches more than 2300 km2, accounting for about 88% of the total area of the study area; (3) The NPP is mainly concentrated in the western part of Helan Mountain, and the main land cover categories are evergreen coniferous forest and annual herbaceous vegetation; the NPP shows a decreasing trend from 2012 to 2021. The total NPP reaches the maximum in 2019, the vegetation carbon sequestration capacity increases significantly, and the ecological quality of vegetation has been improved accordingly since the defense of 2017. The above study analyzed the remote sensing estimation of NPP in Helan Mountains in the past 10 years and sorted out the development trend of vegetation NPP in Helan Mountains, in order to provide theoretical basis for ecological protection and economic construction in Helan Mountains.