Abstract
Pasture and crop lands restrict seed dispersal near remnant forest fragments, especially by restricting the movements of dispersal agents and limiting propagule dispersal. Some factors can improve seed dispersal in open areas, such as the presence of high numbers of isolated trees in close proximity to forest fragments. We sought to determine if: (i) the structural characteristics and (ii) densities of isolated trees in pasture lands, and (iii) their distances from the forest fragments, influence seed dispersal. We installed 18 seed traps in each of six pastures (total=108 traps) bordering forest fragments distributed over 6 distance classes from the forest edges (0, 5, 10, 20, 40 and 80 m). We determined the characteristics of the plants surrounding the traps. GLM and GLMer analyses were performed and the best model was selected by AIC. We collected 8162 seeds (4722 anemochorous, 3304 epizoochorous, 72 autochorous, and 64 endozoochorous) belonging to 26 species. Our results showed that plants with high crown coverage close to forest fragments and at high densities in the pastures increased seed dispersal. These results may aid future restoration of pasture lands by improving seed dispersal in this harsh habitat and promoting better connectivity between forest fragments.
Highlights
Seed dispersal is crucial to plant regeneration (Janzen 1970) but can be negatively impacted by forest fragmentation – which has direct effects on animal populations and plant biodiversity (Galetti et al 2003)
Our results showed that plants with high crown coverage close to forest fragments and at high densities in the pastures increased seed dispersal
The structural characteristics of plants that growing in pastures will influence seed dispersal as tall, broad trees can provide shelter, nesting, and foraging sites (McDonnell 1986; Dean et al 1999)
Summary
Seed dispersal is crucial to plant regeneration (Janzen 1970) but can be negatively impacted by forest fragmentation – which has direct effects on animal populations and plant biodiversity (Galetti et al 2003). The isolation of populations in forest fragments creates difficulties for the movement of pollination and dispersal agents (Tischendorf & Fahrig 2001), restricting functional landscape connectivity (Roland et al 2000; Ricketts 2001; Baum et al 2004) and seed dispersal (Laurance et al 2002). The presence of isolated trees in open pastures can help maintain biodiversity by facilitating the Isolated trees with high crown coverage and densities increase pasture seed rain movements of dispersal agents between habitats (Benayas et al 2008; Arroyo-Rodríguez et al 2009; Cole et al 2010). Trees with a larger diameters and hollows in their trunks are important for many bird species (Mazurek & Zielinski 2004), and trees with larger diameters have greater crown coverage and more branches, and will produce more flowers and seeds (Chapman et al 1992; Greene & Johnson 1994)
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