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Accueil du site → Doctorat → États-Unis → 1994 → Ecological effects of exploitation on Olneya tesota Gray and associated species in the Sonoran Desert

Arizona State University (1994)

Ecological effects of exploitation on Olneya tesota Gray and associated species in the Sonoran Desert

Suzan-Azpiri, Humberto

Titre : Ecological effects of exploitation on Olneya tesota Gray and associated species in the Sonoran Desert

Auteur : Suzan-Azpiri, Humberto

Université de soutenance  : Arizona State University

Grade : Doctor of Philosophy (PhD) 1994

Résumé
The biotic role of ironwood, Olneya tesota (Leguminosae) and the effects of its exploitation in the Sonoran Desert was evaluated with three projects. Project one was an analysis of nurse plant relationships between O. tesota and Peniocereus striatus. Project two was an evaluation of exploitation impacts on O. tesota and associated woody legume populations, and project three was a description of the role of O. tesota as a nurse plant in the region. Project one. Peniocereus striatus, a rare cactus of the Sonoran Desert, was detected to be strongly associated with nurse plants, including Olneya tesota and Larrea tridentata. Because of the harvesting of O. tesota and mesquite (Prosopis velutina and Prosopis glandulosa) over a 20,000 km$\sp2$ area of its range, Peniocereus striatus is vulnerable to habitat degradation. The temporal and local scarcity of sphingid moths available for pollination caused by pesticides and small flower numbers produced low recruitment rates. These important threats to the biotic associates of this cactus have increased its rarity. Project two. Contrasting land uses, ecological discontinuities and an increasing trend of exploitation in Sonora of Olneya tesota for charcoal and carvings have modified its population structure, growth, and recruitment. One case study of particular interest is situated near the international boundary of Organ Pipe Cactus National Monument (ORPI) with Mexico, where a "boundary effect" was detected for the legume tree populations inhabiting both sides of the border. This "boundary effect" was a result of extraction of firewood, charcoal, and carving wood with greater effects within Mexico and the first 200 m in ORPI than further inside ORPI. Project three. The role of Olneya tesota as a nurse plant in the Sonoran Desert was evaluated in Sonora and Arizona. Beneath the canopies of O. tesota seventy-seven perennial plant species were found. A principal component ordination created three groups of the study sites (southern, protected, and disturbed sites). A strong dependency of columnar cacti and shrubs with berry fruits with O. tesota was detected. Significant differences of soil surface temperatures and stem temperatures of P. striatus were detected for plants beneath the shade of the tree and those in open spaces.

Mots clés : Ecology, Mexico, Arizona, Peniocereus striatus, Biological sciences, Botany

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