Canopy functional traits directly drive tree radial growth in subtropical forests

Subtropical forests are important carbon sink areas, and the factors affecting tree radial growth in this area are complex and diverse. Previous studies primarily focused on the effects of single factors on radial growth, but how multiple factors affect tree radial growth and their internal relations have not been clarified. In this study, by constructing 16 tree-ring chronologies and combining four potential variables (climate, soil, spatial factors, and canopy leaf functional traits), we established radial growth models of coniferous and broad-leaved trees using a partial least squares path model (PLS-PM). We found that canopy functional traits directly drive tree radial growth in subtropical forests. However, the direct effect of climate on radial growth is partially offset by the indirect effect of climate on radial growth through canopy. Moreover, in all models, spatial factors and soil indirectly affect radial growth through different paths, although the influence is weak. Together, our work provides evidence for assessing the growth dynamics and carbon sink potential of subtropical forests based on canopy monitoring.