Functional reassembly of tree communities: from tropical drylands to rainforests

Understanding how plant functional strategies vary across environmental gradients is central to predicting community responses to environmental change. While aboveground functional traits in tropical forests are well-documented, their belowground counterparts remain virtually unknown in the context of climate change. Here, we investigate patterns of functional differentiation and trait coordination along a steep precipitation and topographic gradient in the Marañón valley (northern Peru), a biodiversity hotspot forming a transitional ecotone between dry forests and Amazonian rainforests. We combined species abundance data from 96 plots of the Peruvian National Forest Inventory with newly collected leaf, wood, and root traits for 113 tree species to calculate community-weighted mean trait values. We found two main trends in tree functional traits with a first component, associated primarily with leaf traits, showing weak differentiation among forest types and environmental factors, and a second component linked with wood density and root tissue density, varying significantly among forest types and rainfall gradients. Our results show that functional strategies and their coordination respond differently to environmental drivers, highlighting the importance of considering multiple trait dimensions and spatial scales to understand community assembly across tropical environmental gradients.