Stable biomass accumulation driven by conservative traits in Brazil’s tropical montane forests

Abstract

While tropical forests are key CO2 sinks, local drivers of aboveground biomass (AGB) dynamics in diverse systems like the Brazilian Atlantic Forest remain uncertain, constraining ecological references for restoration and long-term carbon sequestration. This study evaluates how biotic and abiotic variables influence AGB dynamics in a diverse montane rainforest. Eight permanent plots were monitored (2012–2022) along an elevational gradient in Caparaó National Park, Brazil. In the second inventory (five years post-El Niño drought), we recorded tree mortality and measured all individuals with DBH ≥ 5 cm. AGB was estimated by employing an allometric equation, and its dynamics between inventories were assessed. Environmental factors, forest structure, functional traits, species diversity, and functional diversity variables were related to ecological hypotheses. We found that AGB increased significantly over 10 years, with a higher increase in communities presenting species with more conservative traits. More plant mass results in faster or more efficient ecosystem functioning. The AGB varied substantially between the communities along the elevation and slope exposure gradients. Our results suggest that the environmental filter (drought and canopy opening) and biomass ratio hypothesis drive AGB dynamics, with AGB gain (main agent of net biomass change) being mainly related to initial growth of tree species rather than by the increment of large trees in the face of adverse environmental challenges. Conservative functional traits facilitate adaptation to harsh environments, ensuring steady AGB accumulation. Such stable carbon sequestration highlights the need to protect and restore tropical montane forests as reference systems against growing climate change threats.