Spatial patterns of Mexican beech seedlings (Fagus grandifolia subsp. mexicana (Martínez) A.E. Murray): influence of canopy openness and conspecific trees on recruitment mechanisms

Abstract

Recruitment strategies of Mexican beech seedlings depend on mother tree distribution and light incidence in early stages of development. Spatial patterns are also affected by the structure and composition of tree species within Mexican beech forests. Canopy openness and conspecific trees play a key role in Mexican beech spatial distribution and might strongly influence ecosystem functioning in the Tropical Montane Cloud Forest. The observed relationship between diameter at breast height of conspecific trees and the spatial distribution of beech seedlings indicates that structure and composition of tree species are crucial for the establishment and survival of seedlings, providing protection during the first developmental stages. To describe the spatial patterns of beech seedlings’ distribution after a masting event and to evaluate the association of these patterns with canopy openness, conspecific tree distribution, and occurrence of other canopy species. We sampled individual Mexican beech seedlings on two highly conserved beech forests. We selected 100 subplots (10 × 10 m) on each one to measure seedlings and spatial attributes. We counted the number of beech seedlings and number of mature trees species on each subplot. In addition, we measured the levels of canopy openness and the diameter at breast height for all mature trees in each subplot. Spatial pattern of beech seedlings and their association with adult trees and other species were examined. Mexican beech seedlings showed significant pattern of spatial aggregation. Significant associations were found between beech seedlings, canopy openness, and beech tree adults, while significant disassociations exist among beech seedlings and other species of trees such as Quercus meavei, Q. delgadoana, Q. trinitatis, and Magnolia schiedeana. The presence of oak species and Magnolia schiedeana in the surroundings and the structure and composition within forests may play a key role in the maintenance of the specific micro-environmental conditions required by Mexican beech recruitment after a masting event.