This project will examine the movement of seeds, by fruit-eating birds, from tropical forest to pasture habitats in Puerto Rico. Seed dispersal is critical for the reestablishment of forest species. A large majority of woody forest plants in this area rely on birds to disperse their seeds. Increased understanding of bird movement between habitats and the fate of seeds that birds disperse will provide a more mechanistic understanding of the early stages of succession and inform conservation and forest restoration efforts. Additional broader impacts will result from collaboration between the PI and a local non-governmental conservation organization in Puerto Rico, and from outreach by the PI to elementary and middle school science teachers and students.
The regeneration of tropical forests on lands degraded by human activities is highly dependent on the capacity of seeds from forest trees to reach the impacted areas. An experiment was conducted to evaluate how the process of seed-dispersal by birds into tropical pastures affected the recruitment patterns of woody plant species, and the availability of nutrients in soils. For eleven months we conducted an experiment in a tropical pasture in Puerto Rico, where we manipulated the activity of seed-dispersing birds, and monitored the availability of fruit in nearby forest fragments, the seed rain in experimental plots, the recruitment, growth, and survival of woody plants whose seeds are dispersed by birds, and the changes in soil nutrients. We found that forest species grew quickly in areas where birds were active, whereas in areas lacking bird activity the regeneration of the plant community was halted despite the manual addition of forest seeds. We also found the seed-dispersing birds increased the nutrient profile of soils via the addition of fecal matter to the sites were they were active. The increased soil nutrient availability showed a positive relationship with the presence and diversity of plant species, suggesting a novel way in which small fruit-eating birds can increase plant establishment. The conclusion is that avian frugivory networks have strong effects on the speed with which woody vegetation can disperse into, and grow, in deforested and degraded tropical lands. The findings of this study also suggest ways in which the process of forest regeneration can be accelerated by the implementation of management techniques that increase the activity of fruit-eating birds in degraded lands. As part of the project, the principal investigator organized and conducted educational activities in collaboration with local NGO's such as the Sierra Club (Puerto Rico chapter). The activities included public conferences, interpretative hikes in natural areas, and the publication of articles for the general public about the importance of plant-animal interactions for processes of forest regeneration.
