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 - Production data for 1967-1969 and 1971

The file pex09.xls refers to production data from plots in USFS Study FSRM 1706-09 that were not formally included in that study. A copy of the Study Plan may be obtained at http://ag.arizona.edu/SRER/study09/study09.txt. The file contains net aboveground production data for perennial and annual grasses. During Study 1706-09 measurements were taken on 12 pairs of sample plots in each of 6 pastures. Two permanent 100-ft. line transects were established at each plot location. Estimates were on two 8x24 ft. subplots centered over each transect (with long axis along the transect). Each pair of plots was located at one of three distances from water and on one of two kinds of soil. Each pasture was subjected to one of three livestock grazing treatments. Pastures 3 and 5N were grazed during the winter dormant season (approximately November through April). Pastures 5S and 12B were grazed during the summer growing season (approximately May through October). Pastures 2N and 6B were grazed yearlong. One transect in each plot was a control, but all mesquite (Prosopis velutina) within 50 ft. of the other was killed. This file contains measurements taken from 1967-1969 and in 1971. In 1967-1969 only the sample plots containing live (untreated) mesquite were read (12 per pasture). In 1971 four sample plots with live mesquite were read in each pasture. Herbage production was estimated in autumn as soon as possible after the end of the summer growing season. Production estimates were adjusted for utilization where necessary. Field weights were estimated in grams, then converted to dry weights using factors developed from double sampling. Dry weights were then converted into air-dry pounds per acre (to the nearest pound). Taxa were recorded separately to the species level in most cases and sometimes to the genus level only. The OTHERPG code refers to unidentified perennial grass species; ANNGRASS to all annual grass species. In this study ARIS refers to the Aristida genus (specifically tall threeawns). A value of -9999 in a field means that no data were available because a reading was not made for that date. A value of -99 in a field means that the datum is unknown. Due to the method used to calculate air-dry pounds per acre a zero entry may have one of two meanings: 1) The species did not occur at all in the plots, or 2) The species occurred in a quantity too small to round up to one pound per acre. The significance of a particular zero entry cannot be inferred from the table; field sheet review would be necessary. Sources of data were original field data sheets with the following exception: Air-dry pounds per acre were not calculated for 1968-1969 and 1971, so these amounts were calculated by applying the factors to grams per 96 sq. ft. plot on the field data sheets