Effects of pasture management on the natural regeneration of neotropical trees.
Natural regeneration of forest trees in grazed pastures could potentially contribute to the conservation of tree diversity within the fragmented and agricultural landscapes that dominate much of the tropics. To understand this potential, we evaluated the effects of several widely used pasture management practices on tree regeneration in pastures in a tropical dry forest (subhumid) region of central Nicaragua. Species richness, density, diversity and composition of seedlings, saplings and adult trees were compared in 46 pastures under different management conditions. The management conditions included three different types of grasses (Brachiaria spp., Cynodon spp. and naturalized pastures) and two categories of fire history (recently burnt and not recently burnt). Thirty-seven of the 85 tree species present in the pastures were regenerated under the current management conditions. The remaining 48 species may have had reduced natural regeneration because of limitations in either germination, dispersal, establishment or growth, as well as because of negative effects of pasture management practices. The richness, density and species composition of tree seedlings within pastures were explained by grass species composition, the density and richness of adult trees, cattle management and the distance of the pasture to forest. In contrast, no clear effect of fire history was found. Synthesis and applications. Current management practices allow the regeneration of almost half of the tree species in grazed pastures. However, to enhance the regeneration of species that show limited regeneration, management strategies, such as the retention of adult trees, protection of saplings and seedlings from weeding and grazing and use of enrichment plantings, may be necessary. These changes in pasture management would help contribute to the long-term conservation of tree diversity within agricultural landscapes across the tropics.