Unveiling the drivers of carbon sequestration in Baotou shelterbelt species: A functional group perspective with...

Understanding the drivers of carbon sequestration in semi-arid shelterbelts is crucial for precision species selection and adaptive management. This study integrated multi-seasonal photosynthetic measurements of 22 species in Baotou, Inner Mongolia, with functional group classification and an explainable XGBoost-SHAP framework. Four distinct photosynthetic functional groups were identified, with XGBoost achieving high predictive skill for net photosynthetic rate (Pn) with a test set R2 of 0.897. SHAP interpretation revealed group-specific drivers: high Pn groups were primarily limited by photosynthetically active radiation (PAR), while others exhibited stronger stomatal conductance (gs) regulation. Notably, vapor pressure deficit (VPD) triggered an inhibitory transition near 2.1 kPa and a 95% confidence interval from 1.379 to 3.93 kPa. These findings provide a threshold-informed, functional group-based strategy for precision afforestation and enhancing carbon sequestration in semi-arid systems, supporting large-scale initiatives such as the Three-North Shelterbelt Program.