Effect of focal trees on the regeneration of tree species in pastures of southwest Mexico

Trees that facilitate the establishment of seedlings under their canopies (focal trees), and favor the creation of tree recruitment nuclei, have been used in ecological restoration projects in pastures and abandoned agricultural lands. However, it is important to know the influence of the variety of tree species in pastures and the effect of cattle grazing on the vegetation under the tree crown. The objective of the study was to analyze the composition, diversity and growth of seedlings of tree seedlings established under focal trees in pastures. The hypothesis was that focal tree species and the fencing effect influence the structure and growth of the seedling community established under focal tree crowns. The experimental design was as follows. Thirty-one trees were selected: five each of Andira inermis, Cordia alliodora, Tabebuia rosea, Sabal mexicana, Sapium lateriflorum and Zanthoxylum riedelianum plus an individual of the Coccoloba barbadensis species was added. Two individuals of each species were fenced (to exclude cattle) for 11 months. The composition of tree seedlings with respect to the focal species and fencing factor was evaluated using multivariate statistics (ANOSIM test and ordination and clustering graphs), height increase was analyzed with ANOVA and the relationship of focal tree crown variables with diversity of plants was analyzed through correlation. The species of focal tree and the fencing effect influenced the structure of the established tree seedling community. Seedling growth depended on the focal tree and richness was related to the focal tree crown variables. These findings demonstrate the importance of selecting diverse focal trees species that vary in their tree architecture in order to promote natural tree repopulation.