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Accueil du site → Doctorat → États-Unis → 1974 → CHEMICAL ECOLOGY OF A NORTHERN ARIZONA PONDEROSA PINE-BUNCHGRASS COMMUNITY

University of Arizona (1974)

CHEMICAL ECOLOGY OF A NORTHERN ARIZONA PONDEROSA PINE-BUNCHGRASS COMMUNITY

Rietveld, Willis James

Titre : CHEMICAL ECOLOGY OF A NORTHERN ARIZONA PONDEROSA PINE-BUNCHGRASS COMMUNITY

Auteur : Rietveld, Willis James

Université de soutenance : University of Arizona

Grade : Doctor of Philosophy (PhD) 1974

Résumé partiel
In addition to competition for light, water, and nutrients there is evidence for chemical interactions (allelopathy) in the ponderosa pine-bunchgrass community of northern Arizona. Seeds of ponderosa pine, cultivated wheat, and yellow sweetclover germinated in aqueous extracts of various live and dead residues of Arizona fescue and mountain muhly demonstrated specific responses in terms of percentage germination, rates of germination, and radicle extension. The dominant effects were induced by extracts of live foliage of fescue and muhly, and to a lesser extent by newer fescue litter : percentage germination and speed of germination were reduced, time for 50% germination was in creased, and radicle length and speed of elongation were retarded. Extract osmotic pressure was found to interact with the inhibitory responses to extracts of the three species. Three possible routes of release of the inhibitor were investigated : (1) leaching from live foliage, (2) root exudation, and (3) overwinter leaching from dead residues. Pine seeds incubated in leachates from 5-minute or 12-hour soakings of fescue and muhly live foliage germinated similarly to the controls, but percentage and speed of clover seed germination were retarded. Germina tion of pine seeds was not impaired by overwintering under mats of dead residues of fescue, muhly, and pine. The possibility of root exudation of toxic substances was studied in a pot experiment in which paired combinations of pine, fescue, and muhly plants were grown for 9 months in a controlled environment chamber. The grasses were superior competitors for available light, water, and nutrients, but there was no evidence for chemical interactions. The principal route of release of the inhibitor was not un covered by the studies performed.

Mots clés : Plant communities — Arizona. ; Allelopathy. ; Grasses — Arizona. ; Ponderosa pine.

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