The objective of this project is to determine the effect of multiple stressors (grazing and shrub removal) on the decline and recovery of perennial grasses in a black grama-mesquite savanna on sandy soils. The initial savanna state represents an intermediate and possibly stable state between black grama grassland and mesquite shrubland.
The experimental manipulations removed about 60% of aboveground herbaceous biomass over 24-36 hour periods in each of four years (from summer 1996-winter 2000). One grazing treatment applied grazing in winter and the other in summer. Including controls (ungrazed and shrubs left intact), this results in 6 treatment combinations. Treatments were applied in a randomized complete block design within 3 replicate blocks resulting in 18 experimental units. Experimental units were 0.5 ha (70 x 70 m) areas that have remained ungrazed by livestock after manipulations were completed in 2000.