Moisés Méndez-Toribio

Effect of land use on the structure and diversity of riparian vegetation in the Duero river watershed in Michoacán, Mexico

Abstract Riparian vegetation performs important ecosystem functions, since it maintains regional biodiversity and provides a range of environmental services. However, anthropogenic activity, land use type, and edge effects are factors that modify the riparian species assemblage and properties. The present study analyzes the influence of adjacent land use on the structure and diversity of riparian vegetation in four hydrographic regions that form the watershed of the river Duero, in the state of Michoacán, Mexico. Using a survey of woody plants of dbh ≥xa02.5xa0cm in ten different 0.1xa0ha sites, we found that the average number of stems and individuals was lower under agricultural (AGR) and urban (URB) land use, compared to forested areas (FOR). The proportion of multistemmed plants differs among land uses: this value was greater in AGR than in the FOR and URB categories. This proportion also differed among the four hydrographic regions. The land use type FOR presented the highest alpha and beta diversity, with a high number of native species occurring only in areas defined by this land use. The results indicate that the category FOR plays an important role in the conservation of regional flora and is a possible source of germplasm for restoration programs in sites degraded by human disturbance. This study shows how anthropogenic activities affect riparian vegetation and highlights the importance of further study of this ecosystem to apply sustainable management strategies that are compatible with its conservation.

Regeneration beneath a dioecious tree species ( Spondias purpurea ) in a Mexican tropical dry forest

In dioecious plant species different frugivore activity between genders may influence the abundance and richness of the seedling banks underneath their canopies throughout seed removal and dispersal. In the tropical dry forest of Chamela, on the Pacific Coast of Mexico, the role of S. purpurea female trees as nucleation sites of regeneration was investigated. The standing density, species richness and dispersal syndrome of woody seedlings (i.e. trees and shrubs, 10–100 cm tall) recruited underneath and outside the canopy of 10 male and 10 female S. purpurea trees were recorded in a total of 160 1-m2 plots. Total density was greater in seedling communities associated with female trees (i.e. underneath and outside their canopies) as compared with male trees (231 vs. 153 seedlings, respectively); whereas overall species richness was greater underneath female canopies. Further, the density of zoochorous species were greater underneath the canopy of S. purpurea females (range = 0–5 plants m−2), than elsewhere (outside female canopies, range = 0–3 plants m−2; underneath and outside male canopies, range = 0–2 plants m−2), suggesting a directional dispersal bias towards them. Females of dioecious plant species may act as nucleation sites of initial seedling recruitment in tropical dry forests.