Original Source Studies

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This section provides access to the original USFS Studies FSRM 1706-09, FSRM 1706-12, FSRM 1706-15, and FSRM 1706-25, which represent the source studies for the Ongoing Vegetation Transects at the SRER.

S. Clark Martin and the Forest Service established these four experiments as early as 1953. Three of those experiments began in the 1950s and proceeded for approximately 10 years, with annual measurements of cover and biomass on permanently established plots. The experiments were designed to compare vegetation responses to different seasons of livestock grazing, the removal of velvet mesquite, and the spatial distribution of water developments for livestock use. The fourth experiment used a subset of the permanent plots from the previous three experiments and 30 newly established permanent plots to compare, on a large scale, the vegetation responses to continuous-yearlong grazing versus a three-pasture rotation grazing system called the Santa Rita Grazing System. This experiment lasted from 1972 to 1984, with measurements made every 3 years. Since 1991, Mitchel McClaran and his graduate students and assistants at the University of Arizona still continue to measure cover, density, and perennial grass basal diameter every 3 years on 131 selected plots used in the Santa Rita Grazing System experiment. 

Study contents and related data can be accessed through the following pages.