Urban forest carbon sequestration capacity was greatly enhanced during rapid urbanization in China

Urban forests play a crucial role in mitigating climate change by sequestering atmospheric carbon. However, previous studies have predominantly focused on carbon storage, while the spatial patterns and underlying drivers of carbon sequestration (CS) capacity remain insufficiently understood, particularly at large spatial scales. This gap is especially evident in rapidly urbanizing countries such as China. In this study, we reconstructed net primary productivity in built-up areas (BUA) in China to reflect urban forest CS capacity and explored the drivers of spatial variation in CS capacity. Results showed that the average CS capacity was 325.89 g·m −2 ·yr −1 , with a distinct spatial pattern of “higher in the southeast and lower in the northwest”. From 2000 to 2020, CS capacity increased steadily, especially in newly expanded BUA and the subtropical monsoon climate zone. Low and medium CS levels dominated, while the proportion of high CS areas increased, particularly in the temperate monsoon climate zone. Total CS increased from 4.12 TgC to 19.89 TgC, with its contribution to offsetting carbon emissions rising from 0.50 % to 0.74 %. The spatial variability of CS capacity was mainly driven by natural factors, with relative humidity identified as the dominant driver in both the subtropical monsoon climate and temperate monsoon climate zones, and Enhanced Vegetation Index (EVI) in the temperate continental climate zone. Urban morphological factors (e.g., construction height) were the key anthropogenic drivers, with notable socioeconomic effects in the subtropical monsoon climate zone. Threshold and interaction effects further enhanced spatial heterogeneity. These findings provide a scientific basis for developing green and low-carbon urban strategies to support carbon peaking and carbon neutrality goals.