The heterogeneous role of spatial configuration in shaping aboveground carbon storage of terrestrial ecosystems: Evidence from China.

Intensive human activities have fundamentally altered the spatial configuration of terrestrial ecosystems. These changes disrupt carbon cycles and diminish terrestrial carbon sinks, thereby exacerbating climate change and challenging China's dual carbon goals. Understanding the impact of ecosystem spatial configuration on aboveground carbon (AGC) storage and identifying key thresholds is essential. This knowledge is crucial for enhancing carbon sinks and implementing Nature-based Solutions (NbS) effectively. This study utilizes multi-source time-series data from 1990 to 2023 and integrates landscape pattern analysis with machine learning algorithms. We investigate spatiotemporal changes in the spatial configuration of China's croplands, forests, and grasslands, and quantify their relationships with AGC at different scales. The findings indicate: (1) China's croplands, forests, and grasslands underwent a cumulative conversion area of 325 million hectares during the study period; (2) All three ecosystems showed decreased fragmentation and increased aggregation, with a continuous rise in patch shape complexity in croplands and forests; (3) Spatial configuration had significant nonlinear relationships and threshold effects with AGC, and explanatory power varied greatly across ecosystems: forests showed the most substantial effect (R2 = 0.75), grasslands less (R2 = 0.61), and croplands the weakest (R2 = 0.43); (4) Elevation and aggregation index were the dominant factors influencing AGC across most river basins in China. By revealing ecosystem-specific response patterns and thresholds, the study offers quantitative guidance for optimizing spatial configurations in diverse regions. It also provides essential data support and a theoretical basis for ecological engineering planning and NbS implementations.