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Abstract The effects of vertebrate seed predation on the regeneration of restored forests are not well understood because most past studies have focused on seed predation within the first few years after restoration and have measured seed removal without quantifying subsequent seedling establishment of seeds that avoid predation. Quantifying the establishment of seeds that escape predation in restored forests at later stages of regrowth is crucial for anticipating longer‐term recovery trajectories. Here, we evaluated the potential role of vertebrate seed predators in limiting recruitment of later‐successional tree species in nine forests actively restored ≥15 years prior and in four paired remnant forest fragments embedded in an agricultural landscape in southern Costa Rica. We conducted seed addition experiments with four tree species inside and outside vertebrate exclosures and used camera trapping to detect seed predators. To determine the fate of seeds that avoided predation, we also measured seedling establishment after 1 year, given that other mortality factors may compensate in the absence of vertebrate seed predation. We detected two species of birds and five species of granivorous mammals removing seeds. Seed tagging indicated that most removal resulted in predation. For three of the four tree species tested, vertebrate seed predation reduced seedling establishment. The magnitude of this effect depended on species' susceptibility to other causes of mortality during the seed‐to‐seedling transition. Our study demonstrates that vertebrate seed predators can substantially reduce later‐successional seedling recruitment in restored forests and should be considered alongside dispersal limitation and microsite conditions as factors slowing forest recovery. Abstract in Spanish is available with online material.
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Seed‐to‐seedling transitions exhibit distance‐dependent mortality but no strong spacing effects in a Neotropical forest
Abstract Patterns of seed dispersal and seed mortality influence the spatial structure of plant communities and the local coexistence of competing species. Most seeds are dispersed in proximity to the parent tree, where mortality is also expected to be the highest, because of competition with siblings or the attraction of natural enemies. Whereas distance‐dependent mortality in the seed‐to‐seedling transition was often observed in tropical forests, few studies have attempted to estimate the shape of the survival‐distance curves, which determines whether the peak of seedling establishment occurs away from the parent tree (Janzen–Connell pattern) or if the peak attenuates but remains at the parent location (Hubbell pattern). In this study, we inferred the probability density of seed dispersal and two stages of seedling establishment (new recruits, and seedlings 20 cm or taller) with distance for 24 tree species present in the 50‐ha Forest Dynamics Plot of Barro Colorado Island, Panama. Using data from seed traps, seedling survey quadrats, and tree‐census records spanning the 1988–2014 period, we fit hierarchical Bayesian models including parameters for tree fecundity, the shape of the dispersal kernel, and overdispersion of seed or seedling counts. We combined predictions from multiple dispersal kernels to obtain more robust inferences. We find that Hubbell patterns are the most common and Janzen–Connell patterns are very rare among those species; that distance‐dependent mortality may be stronger in the seed stage, in the early recruit stage, or comparable in both; and that species with larger seeds experience less overall mortality and less distance‐dependent mortality. Finally, we describe how this modeling approach could be extended at a community scale to include less abundant species.
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- PAR ID:
- 10454752
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Ecology
- Volume:
- 101
- Issue:
- 2
- ISSN:
- 0012-9658
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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