Roles of Birds and Bats in Early Tropical-Forest Restoration

Abstract

Restoration of tropical forest depended in large part on seed dispersal by fruit-eating animals that transported seeds into planted forest patches. We tested effectiveness of dispersal agents as revealed by established recruits of tree and shrub species that bore seeds dispersed by birds, bats, or both. We documented restoration of dispersal processes over the first 76 months of experimental restoration in southern Mexico. Mixed-model repeated-measures randomized-block ANOVAs of seedlings recruited into experimental controls and mixed-species plantings from late-secondary and mature forest indicated that bats and birds played different roles in the first years of a restoration process. Bats dispersed pioneer tree and shrub species to slowly regenerating grassy areas, while birds mediated recruitment of later-successional species into planted stands of trees and to a lesser extent into controls. Of species of pioneer trees and shrubs established in plots, seven were primarily dispersed by birds, three by bats and four by both birds and bats. Of later-successional species recruited past the seedling stage, 13 were of species primarily dispersed by birds, and six were of species dispersed by both birds and bats. No later-successional species primarily dispersed by bats established in control or planted plots. Establishment of recruited seedlings was ten-fold higher under cover of planted trees than in grassy controls. Even pre-reproductive trees drew fruit-eating birds and the seeds that they carried from nearby forest, and provided conditions for establishment of shade-tolerant tree species. Overall, after 76 months of cattle exclusion, 94% of the recruited shrubs and trees in experimental plots were of species that we did not plant.

Isolated trees with high crown coverage and densities increase pasture seed rain

“…Our results described some important characteristics of individual plants that tend to improve seed dispersal in open matrices of fragmented landscapes, and the positive influence of high tree densities on seed dispersal (Benayas et al 2008;Cole et al 2010;Peña-Domene et al 2014) -with high crown coverage and high plant densities (trees and shrubs) being very important to seed rains in pastures. In conclusion, seed dispersal in pastures depends primarily on crown coverage, and secondarily on pasture plant densities and the distance to the forest fragment.…”

“…Isolated trees can offer nutritional rewards (Luck & Daily 2003), good perches, singing sites, nesting sites, and protection from predators (Wegner & Merriam 1979;McDonnell & Stiles 1983;McClanahan & Wolfe 1987). Thus, pastures with isolated trees provide food resources, refuge sites, and shade for cattle and wild birds (Harvey & Haber 1999), and pastures with high tree densities should also increase seed rain and accelerate successional processes (Peña-Domene et al 2014).…”

“…The present results will help us to understand how seed dispersal occurs during the dry season and allow us to presume that the presence of isolated plants with high crown coverage and densities will promote greater seed rains in pastures. A number of authors have shown that isolated trees have important roles in pastures, such as improving microclimate conditions (Callaway 2007;Derroire et al 2016), increasing soil nutrient levels (Belsky et al 1989;Guevara & Laborde 1993;Sarmiento 1997;Rhoades et al 1998;Otero-Arnaiz et al 1999), facilitating forest recovery (Holl et al 2000;Peña-Domene et al 2014) and serving as stepping stones for species movements between forest fragments.…”

“…The presence of isolated trees or clumps of plants in pastures can increase resource availability, improve the quality of the habitat by increasing the floristic and structural complexity of the landscape (Harvey et al 2004), and increases the seed rain from neighboring forest plants (Harvey 2000;Peña-Domene et al 2014). Additionally, plants growing in pastures will increase animal and seed movements and therefore improve the structural and functional connectivity of those fragmented habitats (Bennett et al 1994;Forman 1995;Wunderle 1997;Metzger 2000;Godefroid & Koedam 2003), accelerating plant succession (Peña-Domene et al 2014).…”

“…Additionally, plants growing in pastures will increase animal and seed movements and therefore improve the structural and functional connectivity of those fragmented habitats (Bennett et al 1994;Forman 1995;Wunderle 1997;Metzger 2000;Godefroid & Koedam 2003), accelerating plant succession (Peña-Domene et al 2014).…”