Mesquite cover responses in rotational grazing/prescribed fire management systems: Landscape assessment using aerial images

Abstract

Prescribed fire is used to reduce rate of mesquite (Prosopis glandulosa) encroachment and dominance on grassland ecosystems, but is difficult to apply in continuousgrazed systems because of the difficulty in accumulating sufficient herbaceous biomass (that is, ‘fine fuel’) that is needed to fuel fire. We evaluated the potential of rotationally grazing cattle as a means to defer grazing to provide fine fuel burning. Mesquite cover changes from 1995 to 2000 were compared in four systems: continuous grazing, mesquite untreated (Cont.), 4 pasture/1 herd with fire (4:1F), 8 pasture/1 herd with fire (8:1F), and 4:1 with fire + herbicide (4:1F+H). There were two replicate systems per treatment, each 1,400-2,100 ha. The initial goal in the 4:1F and 8:1F systems was to burn 25 percent of the total area each year (1 pasture in 4:1F; 2 pastures in 8:1F). Fires were conducted in late winter. Mesquite cover was measured using digitized aerial images in 1995 (pre-treatment) and 2000. Droughts limited burning over this 5-year period to half the intended area of each system. Stocking rates, while adjusted in response to droughts, were maintained at similar levels in all systems. Net change in mesquite cover, scaled to account for soil types and pasture sizes in each system, was +34 percent, +15 percent, +5 percent, and -41 percent in the Cont., 4:1F, 8:1F, and 4:1F+H systems, respectively. Cattle performance was similar for all systems during the study period. Rotational grazing and fire systems slowed the rate of mesquite cover increase but did not reduce it. Fire was easier to apply in the 8:1F than the 4:1F system during drought because total area burned could be reduced to 1/8 instead of 1/4 of the system.

Parent Publication

• Proceedings: Shrubland dynamics -- fire and water

Citation

Ansley, R. J.; Pinchak, W. E.; Teague, W. R. 2007. Mesquite cover responses in rotational grazing/prescribed fire management systems: Landscape assessment using aerial images. In: Sosebee, Ronald E.; Wester, David B.; Britton, Carlton M.; McArthur, E. Durant; Kitchen, Stanley G., comps. Proceedings: Shrubland dynamics -- fire and water; 2004 August 10-12; Lubbock, TX. Proceedings RMRS-P-47. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. p. 73-78.