Tree size inequality as a driver of growth dominance across climatic gradients in managed silver fir forests in Europe

Résumé fourni par la source

Competition for limited resources is a key driver of forest structure and dynamics. While growth dominance and tree size inequality are widely used to describe competitive interactions, their relationship remains poorly understood in managed forests. This study examines the links between growth dominance, tree size inequality, stocking density, and climatic conditions in silver fir (Abies alba Mill.) dominated stands. Using data from circular 109 plots established across four sites in Germany, Italy, and Poland, and incre­ment cores from 386 silver fir and 77 European beech trees, we fitted generalized additive models (GAM) to reconstruct individual tree growth and a piecewise structural equation model (SEM) to disentangle the direct and indirect effects of stand structure and climate aridity on growth dominance. The fitted GAMs showed moderate to high explanatory power (adjusted R² = 0.48–0.77). The SEM ex­plained a substantial proportion of variance in growth dominance (marginal R² = 0.57). Growth dominance increased strongly with tree size inequality (standardized estimate = 0.635), while climate aridity reduced it directly (–0.321) and indirectly through negative effects on tree size inequality (–0.324) and stocking density (–0.404). The total effect of climate aridity on growth dominance was substantial (–0.472). These findings demonstrate that growth dominance is an emergent property shaped by resource competi­tion, disturbance, and management legacies. Recognizing this is crucial for forest science and management, as it helps disentangle competition modes and highlights the need to integrate stand structure and com­petitive dynamics into silvicultural planning to sustain the stability and productivity of silver fir dominated stands.

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