The Trend of Grassland Restoration and Its Driving Forces in Ningxia Hui Autonomous Region of China from 1988 to 2018

Abstract

Since the implementation of the grassland ecological protection policy of prohibition grazing on natural grasslands throughout the territory in 2003, the growth of grasslands in Ningxia has improved. This study investigated the spatial differentiation mechanism of normalized vegetation index (NDVI) in Ningxia grasslands from 1988 to 2018, analyzed the relative contributions of climate change (CC) and human activities (HA) to NDVI changes, and predicted the future trend of grassland changes. The results show that except in winter, the annual, seasonal and monthly average values of NDVI after grazing prohibition were higher than those before grazing prohibition. After grazing prohibition, the growth rate decreased by 17.91%, but the degradation rate increased by 3.92%. After grazing prohibition, the proportion of medium coverage increased by 16.15%, mainly in the path of “lower coverage grassland→medium coverage grassland”. The transformation trend was mainly positive, and the ecological construction project has achieved remarkable results. The main factors affecting NDVI differentiation in Ningxia grassland were snow depth, potential evapotranspiration, radiation, and precipitation. After grazing prohibition, the explanatory power of each factor and the interaction between the factors decreased significantly, but the explanatory power of wind speed was greatly improved. After the grazing prohibition, 53.22% of the total area was affected by human activities and climate change. The relative contribution of human activities decreased in NDVI-increased areas but increased in NDVI-decreased areas.

Response of Vegetation Dynamics in the Three-North Region of China to Climate and Human Activities from 1982 to 2018

“…At first, a multiple linear regression equation is constructed based on climate factors to predict the NDVIs only affected by climate change. By analyzing the trends of measured NDVIs, NDVIs only affected by climate changes, NDVIs only affected by human activities, and the relative contributions of climate changes and human activities to vegetation development are quantified [42,43]. The NDVI values only impacted by human activities are calculated as follows [44,45]:…”