Trends and disparities in vegetation restoration and soil & water conservation in Loess Plateau, China

Abstract:

China has implemented an ambitious ecological project Grain for Green Project (GGP) on the Loess Plateau (LP) at the end of last century. The GGP was aimed to increase vegetation coverage, reduce soil and water erosion, and store carbon by converting croplands on steep slopes, barren hills, and wasteland to forests and grasslands. Assessing ecological effects of GGP comprehensively would benefit vegetation restoration activities worldwide. In this study, two major ecological indicators (vegetation restoration and soil & water conservation) were used to evaluate the ecological consequences of GGP from 1982 to 2017. Our results show that the vegetation growth for most LP region have significantly increased in the 21-century with the highest annual growth rates of fraction of absorbed photosynthetically active Radiation (FPAR), leaf area index (LAI) and normalized difference vegetation index (NDVI) in summer for 0.45%, 2.0% and 0.25%, respectively. Meanwhile, soil and water conditions has improved as well with the highest annual growth rates of soil moisture (SM) of 4.46% in summer. These results suggest the overall improvement of ecological conditions in the LP region since the implementation of the GGP project, especially during summer. However, the magnitude differences in the responses of vegetation and soil & water conditions suggest the existence of nonlinearity and heterogeneity of the various biophysical processes during restoration that deserve more detailed process-level analysis to understand the benefits of ecological engineering works more comprehensively.