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Changing gears during succession: shifting functional strategies in young tropical secondary forests

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Abstract

Adaptations to resource availability strongly shape patterns of community composition along successional gradients in environmental conditions. In the present study, we examined the extent to which variation in functional composition explains shifts in trait-based functional strategies in young tropical secondary forests during the most dynamic stage of succession (0–20 years). Functional composition of two size classes in 51 secondary forest plots was determined using community-weighted means of seven functional traits, which were intensively measured on 55 woody plant species (n = 875–1,761 individuals). Along the successional gradient in forest structure, there was a significant and consistent shift in functional strategies from resource acquisition to resource conservation. Leaf toughness and adult plant size increased significantly, while net photosynthetic capacity (A mass) decreased significantly during succession. Shifts in functional strategies within size classes for A mass and wood density also support the hypothesis that changes in functional composition are shaped by environmental conditions along successional gradients. In general, ‘hard’ functional traits, e.g., A mass and leaf toughness, linked to different facets of plant performance exhibited greater sensitivity to successional changes in forest structure than ‘soft’ traits, such as leaf mass area and leaf dry matter content. Our results also suggested that stochastic processes related to previous land-use history, dispersal limitation, and abiotic factors explained variation in functional composition beyond that attributed to deterministic shifts in functional strategies. Further data on seed dispersal vectors and distance and landscape configuration are needed to improve current mechanistic models of succession in tropical secondary forests.

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Acknowledgments

This paper is a scientific contribution to the Agua Salud Project (ASP), a collaboration between the Smithsonian Tropical Research Institute (STRI), the Panama Canal Authority (ACP), and the National Environmental Authority of Panama (ANAM) and part of the Smithsonian Institution Forest Global Earth Observatory (ForestGEO). This study complies with the current laws of Panama, where the study was performed and samples collected. At the time of this study, the ASP was supported by the HSBC Climate Partnership, STRI, the ACP, the Frank Levinson Family Foundation, and the Motta Family Foundation. DC received financial support from the Tropical Resources Institute, STRI, the Lewis B. Cullman Fellowship, and sDiv, the Synthesis Centre for Biodiversity Sciences—a unit of the German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, funded by the German Research Foundation (FZT 118). We thank the staff and personnel of the ASP for logistical support. Without the help of the following people, this project would not have been possible: Nathaly Guerrero Ramirez, Daniela Weber, Federico Davis, Demetrio Hernandez, S. Joseph Wright, Julian Moll-Rocek, Grant Tolley, Michele Abbene, Mario Bailon, Anabel Rivas, and Guillermo Fernandez. The authors also thank Walter Carson and two anonymous reviewers for helpful comments that significantly improved this manuscript.

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Craven, D., Hall, J.S., Berlyn, G.P. et al. Changing gears during succession: shifting functional strategies in young tropical secondary forests. Oecologia 179, 293–305 (2015). https://doi.org/10.1007/s00442-015-3339-x

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