Natural regeneration of tree species in pastures on peasant land in Chiapas, Mexico

In recent decades, large forested areas in southern Mexico have been degraded and even eliminated, often due to conversion of these areas to pastures for cattle grazing. Silvopastoral systems combine livestock raising with tree use, favor conservation of biological diversity, and provide a variety of services to the environment and to farmers. In this study, we evaluated tree regeneration in cattle pastures in the Tulija River Valley of Chiapas, Mexico. We argue that density of seedlings/saplings in the pastures studied is associated with the density of adult trees, with the type of dominant grass (induced or introduced), and with the practice of weeding around seedlings and saplings. We sampled trees in pastures according to categories of size, as well as herbaceous vegetation in 35 cattle pastures, and interviewed farmers with respect to their practices of weeding around seedlings and saplings. We evaluated species capacity for regeneration, and classified species as having adequate or limited natural regeneration capacity (ANR and LNR, respectively). Furthermore, we constructed a generalized least squares model to identify whether density of adult trees, type of grass cover (induced vs. introduced), and farmers practice of weeding affect the density of seedlings and saplings of tree species. Finally, we identified dispersal agents of each tree species recorded and then compared the relative abundance of seedlings/saplings with adult trees for each dispersal agent, using chi-square goodness-of-fit test. In the 35 cattle pastures, we found 17 species (28%) with ANR capacity, 90% of which belonged to secondary vegetation, and 44 species (72%) with LNR capacity; most of these belonged to late successional tree species. Density of seedlings/saplings was positively associated with density of adult trees and the practice of manual weeding. The greatest abundance of seedlings/saplings corresponded to species dispersed by cattle, followed by those dispersed by wind. For adult trees, the most common type of dispersal was by wind, followed by cattle. These results suggest that native tree species are principally dispersed by cattle and wind, and cattle have a positive effect on the regeneration capacity of the most abundant tree species in the pastures studied. We conclude that Chol Mayan silvopastoral management practices in the study communities in Chiapas, Mexico allow for and promote regeneration of native tree species, most of which belong to secondary vegetation, although some belong to late successional species. These simple management practices allow for harvesting some trees in the pasture while also maintaining the regeneration process.