Soil and herbaceous plant responses to summer patch burns under continuous and rotational grazing

This paper examines if post-fire deferment and periodic rests provided by rotational grazing allowed for more rapid recovery of soil cover, soil chemical and physical parameters, and vegetation composition after summer patch burning than continuous grazing. We evaluated the recovery of native rangeland vegetation and soils subjected to summer patch burns in continuously and rotationally grazed pastures in 2002, 2003 and 2004. Each year, 12% of each treatment replicate was burned as a single patch in a different, non-adjacent area under continuous grazing, and as a single paddock of a rotationally grazed 8-pasture-1-herd system. Recovery of vegetation and soils on burned patches were measured annually until the summer of 2006 and compared to those in immediately adjacent unburned areas in both grazing treatments. Herbaceous cover and biomass took 2 years to recover to control levels on soils with greater mesquite cover and more C3 grasses, and 3 years on soils with more C4 grasses. The rotational grazing treatment had less bare ground and lower soil temperatures on both unburned and burned areas than the continuously grazed treatment, which has significant implications for infiltration rates, runoff and erosion in favor of the rotational management. Soil C and C to N ratios were also higher with rotational grazing. Soil physical parameters were not affected by either the burn or grazing treatments but the presence of trees reduced soil temperature, improved soil physical parameters and infiltration rate relative to open grassland.