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

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.