Study FSRM 1706-09 - Livestock Grazing Season

Study FSRM 1706-09: A Comparison of Vegetation Responses to Grazing Yearlong, in the Growing Season, and in the Dormant Season on Low-Value Semidesert Grass-Shrub Ranges in Southern Arizona Study plan

S. Clark Martin designed this study to compare plant cover and biomass production among three livestock grazing treatments, three distances from livestock water developments, two mesquite removal treatments, and two soil types (see Study Plan ASCII text file below). The grazing treatments were yearlong, dormant season (November through May), and growing season (June through October). The distances from water were 0.25, 0.625, and 1.0 mile from water, which provided a surrogate for grazing intensity. Complete removal and no removal were the mesquite treatments. Coarse sandy loam with low concentration of clay and loamy soil with higher concentrations of clay were the two soil types.

The 72 permanently established study plots were equally divided among six pastures (12 per pasture in Pastures 2N, 3, 5N, 5S, 6B, and 12B). There were two replicates (pastures) devoted to each grazing treatment. The stocking rate of livestock was set to maintain a 40 percent use of perennial grasses in all pastures.
Within each pasture, the locations of the 12 plots were nested within the distances from water, soil types, and mesquite treatments (all mesquite were removed from half of each plot) to produce a split-split-split plot experimental design.
On each plot, two parallel 100-foot transects were permanently established, one in the mesquite-cleared area and the other 150 feet away in the mesquite-untreated area. On each of the transects, plant cover was measured as the intercept by species along a graduated tape in increments of 0.01 foot. Perennial and annual grass biomass was measured at the end of the summer growing season by clipping, drying, and weighing (to nearest gram) all grass plants in two 8-foot by 24-foot plots placed along each 100-foot transect.
Based on the transect locations marked on aerial photographs, estimates of these locations were placed on mylar overlays of USGS 7.5' (1:24000) topographic quad maps of the SRER, and then digitized from the overlays. The UTM coordinates represent the digitized points reprojected to the NAD83 datum using the GRS1980 spheroid. During the course of the study, five plot locations were changed.

The results of the study are described in four publications. Cover and production measurements were continued on 60 of these study transects in “Forest Service Study FSRM 1706-25: Benefits of rest March–October two years out of three” (See the FSRM 1706-25 section below). Fifty-eight of those study plots are included in the Ongoing Vegetation Transects measured on the SRER since 1991.

This page provides the following contents related to the Study FSRM 1706-09.