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Insect herbivory is one of the major drivers of seedling mortality in the tropics and influences plant abundances and community composition. Anthropogenic disturbance can alter patterns of insect herbivory with potential consequences on plant communities in restored forests. We planted seedlings of early‐ and later‐stage successional tree species in 13–15‐year‐old restored and remnant tropical forests. We then either excluded insect herbivores or left seedlings exposed to examine how insect herbivory‐affected seedling mortality. Early‐successional seedlings experienced similar decreases in mortality when insect herbivores were excluded from both restored and remnant forest sites, but this effect was smaller and driven by only a few species in restored forests. Later‐successional seedlings experienced a stronger decrease in mortality between open and insect‐excluded treatments in remnant than restored sites. Our results suggest that herbivory‐driven seedling mortality is lower in restored forests, particularly for later‐successional seedlings. Results are encouraging from a restoration perspective because recruitment of later‐successional seedlings is a key component of ecosystem recovery. However, if reductions in seedling mortality continue over the long term, this may affect tree community composition as succession progresses.
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Vertebrate seed predation can limit recruitment of later‐successional species in tropical forest restoration
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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- PAR ID:
- 10543869
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Biotropica
- Volume:
- 56
- Issue:
- 6
- ISSN:
- 0006-3606
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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