Diversity, structure and dynamics of tropical montane forests: Insights from permanent-plot monitoring in the Venezuelan Andes

Abstract

Tropical montane forests in the Andes are hotspots for species diversity and constitute important ecosystems for the provision of numerous services critical for local populations, including biomass/carbon accumulation and hydrological regulation. Additionally, in many countries in the region, these forests are being lost or degraded at alarming rates. Understanding their dynamics in terms of the composition, diversity, structure and function is a key challenge in the region that can inform policies for their sustainable management and conservation. This study focused on the use of monitoring data from ground-based permanent plots (part of the Andean Forest Network) in the two main mountain ranges of the Venezuelan Andes to analyze forest structure, diversity and dynamics over six years (2016-2023), and their potential drivers. We found that although the we�er forests of La Mucuy (northeast) and the more seasonal stands of San Eusebio (northwest) are very similar in terms of overall species richness, they show substantial differences in their species assemblages and their biogeographic origins. Both sites share similarities in tree dispersal strategies and stem turnover rates (mean=1.16%/year), but forests in La Mucuy are significantly more productive, with a mean annual woody productivity rate of 3.09±1.42 Mg C.ha-1.y-1, while this rate was 0.73±0.48 Mg C.ha-1.y-1 in SEU plots. Interestingly, although species richness and composition has not shown significant changes during this 6-year period, both sites have increased their total aboveground biomass, acting as a significant carbon sink, which appears to be largely driven by the growth of large trees in these forests. These results emphasize the need of maintaining long-term monitoring efforts to be able to link more explicitly changes in composition, biodiversity and ecosystem services with changes in environmental drivers under climate change scenarios.