Analysis of 20 years of monitoring data reveals insufficient carbon sequestration potential of planted forests in dryland regions

Ecological restoration has been widely regarded as an essential strategy to enhance carbon sequestration in ecologically fragile areas. However, the long-term sustainability and dynamics of carbon sequestration induced by afforestation remain uncertain, particularly in dryland river basins. Clarifying long-term carbon sequestration trends and understanding the impact of planted forests on these trends are crucial for ecological management and achieving carbon neutrality targets. In this study, we evaluated the dynamics of vegetation carbon sequestration and soil carbon storage in the Yellow River Basin (YRB) over the past two decades using annual Net Primary Production (NPP) and Soil Organic Carbon (SOC) datasets. Our results indicated that afforestation significantly enhanced NPP during the initial restoration phase (NPP increased by 34%), but subsequently NPP declined (NPP decreased by 10%), whereas SOC exhibited a modest increase with a gradually decreasing growth rate over time. Increased frequencies of extreme temperature and drought events negatively affected soil moisture availability and the sustained growth of planted forests. Furthermore, land-use transitions contributing to enhanced carbon sequestration and storage approached saturation, constrained by environmental limitations and cultivated-land protection policies. Given water-resource constraints, realizing future carbon sequestration benefits in dryland ecosystems requires more strategic vegetation spatial planning within ecological restoration initiatives. Our findings provide valuable insights for carbon management strategies in the YRB and similar dryland river basins.