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Accueil du site → Doctorat → Mexique → Aspectos funcionales y biogeográficos en desiertos cálidos de América : desierto Sonorense (México) y desierto del Monte (Argentina) - 2005 - Centro de Investigaciones Biológicas del Noroeste, S.C.

Centro de Investigaciones Biológicas del Noroeste (CIBNOR) 2005

Aspectos funcionales y biogeográficos en desiertos cálidos de América : desierto Sonorense (México) y desierto del Monte (Argentina) - 2005 - Centro de Investigaciones Biológicas del Noroeste, S.C.

Perea Gamboa, María Cristina

Titre : Aspectos funcionales y biogeográficos en desiertos cálidos de América : desierto Sonorense (México) y desierto del Monte (Argentina) - 2005 - Centro de Investigaciones Biológicas del Noroeste, S.C.

Auteur : Perea Gamboa, María Cristina

Etablissement de soutenance : Centro de Investigaciones Biológicas del Noroeste (CIBNOR)

Grade : Doctorado en Ciencias en el Uso, Manejo y Preservación de los Recursos Naturales 2005

Résumé
In this work a functional study of desert vegetation was done under two levels of analysis, one relative to the general behavior of the vegetation communities and the other directed to identify particular aspects in the function of the species that grow under certain environmental conditions. To accomplish this purpose, the work was divided in two parts. The first part contains the functional morphology study of the sarcocaulescent scrub in the Baja California peninsula, which was done to identify the functional plant types. The work was done in three different physiographic units within the sarcocaulescent scrub ecological areas : open scrub, clustered scrub, and closed scrub. We found 41 perennial species which were characterized using 122 morphology-functional characteristics, corresponding to parts of the plant (stem and leaf), reproductive parts (flower and fruit), and functional phases (phenology, pollination, and dispersion). Our analysis allowed the clear identification of four morphological groups in our study area : (a) crasicaulescent plants and succulent cacti, (b) sarcocaulescent species, (c) woody trees, and (d) woody shrubs. Our results indicate that Forrest’s classification of desert communities based on the external morphology of the plants is statistically robust and reflects a significant underlying pattern. The second part includes a comparative study of the morphology and leaf anatomy of four woody species growing in two warm deserts in America : two species in the Sonoran Desert in Mexico, near sea level, and another two species in an intermountain valley in Argentina. The situation of species with disjunct distribution was considered. That is, those taxa, whose areas of distribution are separated by great distances and the situation of ecological equivalents, which are different species that display functional and structural likelihood due to similarities in their niches. The object of the study was to know the area of distribution of these species in both desert environments and find differences and similarities in functional, morphological and anatomic traits that would represent adaptive advantages of these species. A tendency was observed, in the same species to present greater organs in the species that grow in the Sonoran desert. Whereas greater thicknesses of leaves are found mainly in the species of the Monte desert. For the species studied, the Sonoran desert would have greater soil water availability, and those from the Monte, in the intermountain valleys, would endure more sun radiation. We conclude that the “phenotypic plasticity” identified for the species with disjunct distribution can be interpreted like a functional response that gives these species capacity of adaptation to different environments, gradually increasing their distribution areas and physiognomy dominance of these species in their respective habitat. For the ecological equivalents, the anatomic convergence observed, relative to “centric” arrangement in the mesophylls, is in functional adjustments that would tend to favor the species in particular environments.

Mots Clés : functional types, sarcocaulescent scrub, Shreve’s classification, Baja California, disjunction area, ecological equivalent, Sonoran desert, Monte desert

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