Competition and temperature could drive radial growth of Schima superba in humid subtropical forests of China

• The competition index (NGR) best explained the 20-year accumulative radial growth (G 20 ); • Temperature in April had significant positive effects, while temperatures in the coldest month (January) and September, and relative humidity in May, had significant negative effects on tree radial growth; • The combination of NGR, Tmin9, Tmin1, and RH5 explained 64% of the variance in G 20 , with relative contributions of 71.24%, 11.24%, 13%, and 4.5%, respectively. Competition and climate are two crucial factors influencing tree growth, particularly in densely populated and canopy-closed forests. The Chinese subtropical evergreen broadleaved forest, a region with a high net carbon sink rate, is currently experiencing climatic warming and changes in precipitation patterns that may increase aridity and alter stand structure. Understanding how competition and climate impact the radial growth of evergreen broadleaved tree species in this region remains unclear. To address this gap, we collected data on competition and tree-ring width from 15 natural Schima superba stands across a large subtropical region using dendroclimatology. We simulated multi-year accumulative radial growth (G T ) over the most recent 5, 10, 15, and 20 years using six distance-independent competition indices in linear mixed-effects models. Our findings revealed that the competition index representing the number of greater competitors than the focal tree (NGR) best explained the 20-year accumulative radial growth (G 20 ) in linear mixed-effects models, with the highest marginal and conditional R 2 values (0.39 and 0.70, respectively). Additionally, we found that temperatures in April had significant positive effects on tree radial growth (T4, r = 0.674, P < 0.05; Tmax4, r = 0.655, P < 0.05), while temperature in the coldest month (January) and September and the relative humidity in May had significant negative effects on tree radial growth (T9, r = − 0.434, P < 0.05; Tmin9, r = − 0.465, P < 0.05; Tmin1, r = − 0.349, P < 0.05; RH5, r = − 0.412, P < 0.05), respectively. The best model, which included NGR, Tmin9, Tmin1, and RH5 explained 64 % of the variance in G 20 , with relative contributions of 71.24 %, 11.24 %, 13 %, and 4.5 % respectively. These results suggest that competition and temperature are key drivers of radial growth in Schima superba within these humid subtropical forests. Our findings also indicate that appropriate thinning practices targeting large trees could enhance radial growth, helping these forests adapt to climatic warming and increasing aridity.