Functional traits mediate the effect of environmental conditions on tree growth of common Andean trees

Abstract

Understanding how plant functional strategies interact with environmental variation is essential to predict the impacts of global change on forest communities. Here we investigated how resource-acquisition strategies, captured by branch and leaf traits, interact with environmental gradients, including climate, soil fertility, and solar radiation exposure, to influence relative growth rates (RGR) in 224 tree species from tropical montane forests in the Madidi region of the Bolivian Andes. Using data from 33 permanent forest plots and Bayesian hierarchical models, we found that the effects of environmental conditions on tree growth were modulated by species’ resource-acquisition strategies. Our findings reveal that acquisitive species, with higher specific leaf area (SLA), larger leaf size, and lower tissue density, performed better in cooler, drier, thermally variable, nutrient-rich sites with low solar radiation. In contrast, conservative species, characterized by stress-tolerant traits (higher tissue density and smaller leaves), grew better in nutrient-poor, high-radiation environments and tended to be less responsive to climatic gradients. Our analysis relied on two major PCA axes of functional trait covariation that captured distinct mechanistic pathways but aligned with survival-growth trade-off. Our results suggest that whole-plant allocation strategies, reflected by a leaf-area vs wood density trade-off may be more important than leaf-level traits (e.g., SLA) under closed canopies, highlighting the multidimensionality of trait-growth relationships. Our results underscore the role of trait–environment matching in shaping species performance and community assembly, and highlight the importance of trait-based approaches for forecasting forest responses to climate and land-use change. • Plant traits and environmental gradients interact to drive tree growth in the Andes. • Acquisitive species are more sensitive to climatic gradients than conservative ones. • Soil fertility favors acquisitive species whereas conservatives tolerate poor soils. • High solar exposure favors conservative species growth, limits acquisitive species. • Leaf area and wood density better predict growth compared to SLA in adult trees.