Impacts of climate change and vegetation greening driven by natural and anthropogenic factors on carbon sink in Chinese Loess Plateau after ecological restoration

Abstract

The Loess Plateau (LP) has been recognized as a significant hotspot for vegetation greening in China since 2000. However, the influence of vegetation greening driven by various factors on carbon sinks in changing environments remains unclear due to the lack of high-precision datasets on carbon stock changes and effective attribution analysis methods. In this study, a time-series dataset of vegetation total carbon density (VTCD), soil organic carbon density (SOCD), and ecosystem total carbon density (ETCD) in the LP was estimated using a combination of multi-source data and machine learning algorithms. The impact of vegetation greening on carbon sinks was further decomposed by considering the effects of climate change and human activities on vegetation dynamics. Our findings indicate that the Extra Trees Regressor performs best in estimating VTCD (RMSE = 0.42 kgC m^–2) and SOCD (RMSE = 2 kgC m^–2). Across the entire landscape, the average carbon sequestration rate (CSR) is 37 gC·m^–2·a^–1, comprising 26 gC·m^–2·a^–1 from soil and 11 gC·m^–2·a^–1 from vegetation. The highest CSR is found in naturally restored forests (55.26 gC·m^–2·a^–1), followed by grassland converted to forest (G-F) at 50 gC·m^–2·a^–1, and cropland converted to forest and grassland (C-Fg) at 38.23 gC·m^–2·a^–1. Compared to natural recovery areas, human-induced restoration demonstrates a significant carbon sink benefit (70 %–303 %), exhibiting distinct spatial heterogeneity. The direct impact of climatic factors on carbon sinks is 3.44 gC·m^–2·a^–1, contributing 9.3 % to the overall carbon sink. Vegetation greening accounts for 83.4 % of the carbon sink, with contributions of 44.5 % from climate-driven natural recovery, 24.7 % from cultivation management, and 14.2 % from human-induced vegetation type change. Additionally, the positive impacts of other human activities (e.g., terracing, check dams) on carbon sinks should not be overlooked. This study provides new insights into the effects of climate change and human activities on carbon sinks in the Loess Plateau.