Demographic, spatial, and ecological aspects of Peltogyne mexicana - a threatened species – Under different extraction conditions in southern México

Abstract

Peltogyne mexicana Martínez is a commercially attractive purple-hued hardwood tree of demographic, environmental and biogeographic rarity in southern Mexico. Despite P. mexicana’s status as a threatened species in Mexico, its populations are rarely managed and subject to open harvesting. Due to the limited number of P. mexicana studies that account for the influence of local tree extraction, we analyzed population-level parameters and community-level associations in two sites - one site called Tepehuaje with active P. mexicana extraction and another called Acahuizotla without extraction due to an ongoing P. mexicana moratorium. Using three 500 m2 plots per site, we characterized P. mexicana population size structure, abundance, spatial distribution, composition, and diversity of associated flora. In both sites, P. mexicana populations exhibited a type one size structure dominated by seedlings. Tepehuaje had 52% fewer saplings and juveniles and three times fewer adults when compared to the site without extraction. P. mexicana juvenile survival in Tepehuaje, a site with warmer climate and lower canopy cover, occurred mainly under trees with heavy foliage (including conspecifics). In Acahuizotla, a site with cooler climate and greater canopy cover, sapling and juvenile abundance was higher in open spaces and under small trees like Cascabela ovata. Although species richness was greater in Acahuizotla, species diversity was higher in Tepehuaje likely due to regularly opened gaps from artisanal logging that limited dominance of certain species. An importance value index (IVI) analysis based on dominance, abundance, and foliar coverage of associated P. mexicana plant communities revealed differences between Acahuizotla (Tetrapterys spp., followed by Plumeria rubra L) and Tepehuaje (Citharexylum affine D. Don, and Bauhinia ungulata L). All species associated with P. mexicana were found to be characteristic of tropical subdeciduous forests. Studying P. mexicana demography and ecology expands the limited knowledge we have of a rare, yet biologically important, species, and sheds light on local practices that can improve persistence.