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Data from: Effects of dispersal‐ and niche‐based factors on tree recruitment in tropical wet forest restoration

Citation

Werden, Leland K. et al. (2020), Data from: Effects of dispersal‐ and niche‐based factors on tree recruitment in tropical wet forest restoration, Dryad, Dataset, https://doi.org/10.7291/D15X0G

Abstract

Both dispersal‐ and niche‐based factors can impose major barriers on tree establishment. Our understanding of how these factors interact to determine recruitment rates is based primarily on findings from mature tropical forests, despite the fact that a majority of tropical forests are now secondary. Consequently, factors influencing seed limitation and the seed‐to‐seedling transition (STS) in disturbed landscapes, and how those factors shift during succession, are not well understood. We used a 3.5‐yr record of seed rain and seedling establishment to investigate factors influencing tree recruitment after a decade of recovery in a tropical wet forest restoration experiment in southern Costa Rica. We asked (1) how do a range of restoration treatments (natural regeneration, applied nucleation, plantation), canopy cover, and life‐history traits influence the STS and (2) how do seed and establishment limitation (lack of seed arrival or lack of seedling recruitment, respectively) influence vegetation recovery within restoration treatments as compared to remnant forest? We did not observe any differences in STS rates across restoration treatments. However, STS rates were lowest in adjacent later successional remnant forests, where seed source availability did not highly limit seed arrival, underscoring that niche‐based processes may increasingly limit recruitment as succession unfolds. Additionally, larger‐seeded species had consistently higher STS rates across treatments and remnant forests, though establishment limitation for these species was lowest in the remnant forests. Species were generally seed limited and almost all were establishment limited; these patterns were consistent across treatments. However, our results suggest that differences in recruitment rates could be driven by differential dispersal to treatments with higher canopy cover. We found evidence that barriers to recruitment shift during succession, with the influence of seed limitation, mediated by species‐level seed deposition rates, giving way to niche‐based processes. However, establishment limitation was lowest in the remnant forests for large‐seeded and late successional species, highlighting the importance of habitat specialization and life‐history traits in dictating recruitment dynamics. Overall, results demonstrate that active restoration approaches such as tree planting catalyze forest recovery, not only by decreasing components of seed limitation, but also by developing canopy cover that increases establishment rates of larger‐seeded species.

Methods

We conducted this study at five ~1-ha sites in southern Costa Rica, a subset of the 13 replicate restoration sites of this long-term experiment, located between the Las Cruces Biological Station (8° 47' 7" N, 82° 57' 32" W) and the town of Agua Buena (8° 44' 52" N, 82° 56' 39" W). At the start of the study, from 2004-2006, we established three 0.25-ha (50×50 m) plots separated by a ≥5 m buffer at each site. Three restoration treatments: natural regeneration, applied nucleation, or plantation, were applied to one of the plots at each of the sites. At three of the five sites selected for this study, equivalent sized plots were established in adjacent remnant forests to serve as references

Funding

National Science Foundation, Award: DEB 05‐15577

National Science Foundation, Award: DEB 09‐18112

National Science Foundation, Award: DEB 14‐56520