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University of Arizona (1981)

Sensitivity of frequency and canopy cover to changes in vegetation

Mirreh, Mohamed Mohamud

Titre : Sensitivity of frequency and canopy cover to changes in vegetation

Auteur : Mirreh, Mohamed Mohamud

Université de soutenance : University of Arizona

Grade : Master of Science (MS) 1981

Résumé
Comparison of the sensitivity of frequency and canopy coverage as methods for monitoring condition and trend in rangelands were made in five stands having different management histories and representing a sandy loam range site at Santa Rita Experimental Range. The number of significant, differences detected for the species between the five stands at the 95% level was slightly higher for frequency than canopy coverage. Both methods were highly correlated to the importance value at the 95% level of significance. The canopy coverage method was a more sensitive measure of difference resulting from utilization between those areas excluded from grazing and those open to grazing* even though there was no apparent condition difference between them. The ephemeral nature of canopy cover reduces the value of using the canopy cover method for trend.analysis. Using the same sampling time allowed more frequency quadrats to be run and precision increased from 55 to 63 at the a .05 level for detecting differences between the location. Adequate sample size for the canopy cover method in desert grassland was estimated as 6 to 8 transects of 20 quadrats for total cover.. Sample size for individual species was highly variable. Bias in estimates of canopy cover with increasing quadrat size was negligible for com monly used quadrat sizes.

Mots clés : Rangelands — Research — Arizona. ; Rangelands — Arizona. ; Santa Rita Experimental Range (Ariz.)

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