Tuesday, August 5, 2008

PS 18-24: Environmental heterogeneity and conservation status in the Abies religiosa forest in Magdalena river basin

Santibañez A. Gabriela1, Castillo A. Silvia1, Nuñez C. Oswaldo1, and Martinez O. Yuriana2. (1) Universidad Nacional Autonoma de México, (2) Universidad Nacional Autónoma de México

Background/Question/Methods Mexican Temperate forests represent an important habitat rich in plant diversity as well as in endemisms. Abies religiosa forest of Magdalena river basin in the valley of Mexico shows a very heterogeneous topography and a characteristic microclimatic variability that create environmental features that determine a patchy distribution of species. Ecological information about the status of this area which includes detailed environmental data (biotic and abiotic) that influence and maintain diversity at different scales is basic in conservation and management projects.The aim of this work was to analyze the environmental heterogeneity of Abies religiosa community in order to know the distribution patterns of the different groups of vegetation and to characterize the conservation status of the system. With the use of GIS’s, to create thematic maps were elaborated and with aerial photographs, landscape units were determined. In each unit 5 plots (25 x 25m) were established where physical parameters such as: altitude, aspect slope, humidity, temperature, light incidence and canopy cover were measured. Biotic parameters measured were plant cover and bare soil percentages, regeneration and reforestation were registered. Herbaceous species and trees were measured in cover and height. Multivariate analysis were applied to find a relation between physical parameters and species presence.  Results/Conclusions   Eleven units were obtained at landscape level as a result of the environmental heterogeneity analysis, where main factors were orientation, slope and plant cover. These units represent a different composition that reflects the degree of conservation of the studied area. With relation to the identification of sites with different degrees of perturbation, data show six of these are perturbed sites and five conserved ones. On the other hand conservation status at plot level is being determined by the density and richness of trees, indicating that in more conserved sites Abies religiosa density is higher and the presence of other species is less important, independently of the landscape unit. With relation to the understory we found that distribution patterns of the species of this forest are related to abiotic factors variation, which contribute to the existence of diverse groups of vegetation in the community. These results represent the basic information needed to establish an adequate conservation and restoration plan of the Abies religiosa forest in the Magdalena river basin.

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