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Accueil du site → Doctorat → Mexique → Análisis de gradiente y dinámica sucesional de bosques de encino (quercus) en la Sierras Madre Oriental y Occidental de México

Universidad Autónoma del Estado de San Luis Potosí (UASLP) 2008

Análisis de gradiente y dinámica sucesional de bosques de encino (quercus) en la Sierras Madre Oriental y Occidental de México

Flores Cano, Jorge Alberto

Titre : Análisis de gradiente y dinámica sucesional de bosques de encino (quercus) en la Sierras Madre Oriental y Occidental de México

Auteur : Flores Cano, Jorge Alberto

Etablissement de soutenance : Universidad Autónoma del Estado de San Luis Potosí (UASLP)

Grade : Doctorado en Ciencias Ambientales 2008

Résumé
The altitudinal distributions of oak species (Quercus spp.) were quantified in the Sierra Madre Oriental (state of San Luis Potosí) and Occidental (sta tes of Chihuahua, Durango and Aguascalientes) with the idea of detemining patterns of spatial replacement and coexistence. The fundamental hypothesis was that two or more oak species with similar morphological characteristics could not coexist, and that the species, best adapted to the conditions of a site would displace the other species present. Oak species were classified into three functional groups based on their morphological and ecological characteristics which could affect their ability to either colonize open sites or compete with members of the other functional groups. Eight species of Quercus were present in the study sites of the Sierra Madre Oriental. Depending on the locality, four species were members of the colonizing guild, three species members that replace members of the previous functional group and one species, that given sufficient time dominates the forest. In the Sierra Madre Occidental, ten species of Quercus were common enough to quantify, three pioneers, six intermediate-stage species and one late succession species. In both regions, the forests were at sub-climax dominated by early and intermediate stage oak species. The pioneer and intermediate stage species occupy a wide range of altitudes in comparison to the climax stage, where the species require relatively more humid environmental conditions. As a result the climax oak species are relicts, populations of which are small and isolated. The successional replacement of oak members of the three functional groups was studied along one such gradient in the Sierra de Álvarez (San Luis Potosí). The pioneer species in this area was Quereus eoeeolobífolía, seedlings of which establish in abandoned agricultural fields next to the oak forest. Seedlings of the other three members of this community (Q. era ssífo lía , Q. obtusata, Q. affínís) only establish at the immediate edge of the forest or within the forest. Using measurements of canopy asymmetry, the sequence of species replacements was inferred within the forest. In this site the pioneer species, Q. eoeeolobífolía, was replaced by Q. erassífolía, Q. erassífolía replaced by Q. affínís, and Q. obtusata, the only member of the white oak group present, replaced by the dominant Q. affínís. Trees with asymmetric canopies tend to grow away from the dominant individual and tend to have more damage to their trunks than individuals growing symmetrically.

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Page publiée le 28 septembre 2017, mise à jour le 10 janvier 2020