Understanding forest regeneration in bracken-dominated areas of tropical montane forest: a trait-based approach

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Tropical montane forests are among the most important biodiversity hotspots of the world. However, many forest areas have become highly fragmented due to land-use change, especially caused by human-induced fires. The remaining forest remnants are surrounded by strongly disturbed habitats dominated by bracken fern (Pteridium spp.). Since bracken usually dominates the vegetation for long periods and across large areas, disrupting forest succession and ecosystem services, science-based strategies to accelerate forest regeneration are urgently needed. We will combine observational and experimental studies in tropical bracken-dominated montane communities of the Bolivian Andes in order to: a) identify the major abiotic and biotic filters that explain species coexistence and performance during forest regeneration; b) determine the functional traits of the tree species that can coexist with bracken. Our project is structured in four work packages (WP): In WP1, we will study the natural regeneration of tree species in areas with different ages since fire to predict the likely temporal pattern, as well as characterize the changes in environmental conditions and functional traits of the community, using a chronosequence approach (space-for-time substitution). To test our hypothesis that seed limitation, rather than establishment limitation, is the most important filter delaying forest recovery in bracken-dominated areas, we will experimentally assess regeneration-related plant-plant interactions (WP2: competition, facilitation) and plant-animal interactions (WP3: seed dispersal). In WP2, we will evaluate the performance of native tree species with different functional traits under different experimental bracken treatments and test the potential allelopathic effects of bracken on plant development in a common garden. In WP3, we will assess seed dispersal effectiveness of birds and bats, and the potential value of perches and bat roosts to increase seed dispersal and seedling recruitment. In WP4, we will study the main bottlenecks for the recruitment of tropical montane tree species by considering direct and indirect effects of abiotic and biotic variables on different stages in their life cycles, using structural equation models. Finally, in an integrative approach, our data will be combined to form ecological trait-based models that predict species abundances and test alternative community pathways according to bracken presence and climate change predictions. Our project will substantially enhance our understanding of the dynamics of tropical montane forest regeneration, and will provide essential information for accelerating forest restoration in bracken-dominated areas, which are common throughout tropical regions.