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University of Arizona (1976)

Grass production changes with mesquite (Prosopis juliflora) reinvasion in southern Arizona

Williams, Patrick Thomas

Titre : Grass production changes with mesquite (Prosopis juliflora) reinvasion in southern Arizona

Auteur : Williams, Patrick Thomas

Université de soutenance : University of Arizona

Grade : Master of Science (MS) 1976

Résumé
Mesquite density crown cover, and grass production were used to evaluate the rate and effect of mesquite reinvasion at five study areas. The mesquite elimination study consisted of sixteen 1-acre plots of which eight were cleared of mesquite in 1940. The four thinning study areas each consisted of one control plot and plots where the mesquite was thinned to leave 25, 16, 9, or 0 trees per acre in 1945. Analysis of variance and regression analysis were used to aid in the evaluation. All mesquite trees were counted. Crown cover was based on a sample of ten trees per acre. Grass production on the elimination study was determined by clipping four randomized belt transects (4" x 33’) per plot. Grass production on the thinning study was determined by double sampling using ocular estimates on two 5-plot samples per 2-acre treat ment plot. Herbage from one plot in each sample was clipped and weighed. In the mesquite elimination study, more grass was produced in 1974 on the treated areas than on the untreated. In the mesquite thin ning study, grass yields generally were negatively related to thinning density. These results show retreatment following mesquite control is not needed for at least 30 years if all of the mesquites are killed by the initial control job. Retreatment would be needed sooner following the average mesquite control project where about half of the mesquites re sprout vigorously soon after treatment.

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