干旱区生态环境知识资源中心

Vegetation composition and forage productivity were studied on two Chihuahuan desert ranges with different management histories. They involved the conservatively grazed New Mexico State University College Ranch, and adjoining intermediately grazed Bureau of Land Management(BLM) ranges north of Las Cruces in southcentral New Mexico. Conservative and intermediate grazing involved about 30 and 50% average use by livestock of the key forage species, respectively. A major focus of this study was the influence of stocking rate on recovery of native perennial grasses on rangeland with moderate amounts of honey mesquite (Prosopis glandulosa Torr.) (College Ranch) compared to areas heavily dominated by mesquite (BLM). In fall of 1982 total perennial grass standing crop averaged 182 kg/ha and 36 kg/ha on the long-term conservatively (CG) and intermediately grazed (IG) ranges, respectively. By the fall of 1990 perennial grass standing crop had increased to 349 kg/ha and 159 kg/ha on the CG and IG ranges, respectively. Mesa dropseed (Sporobolus flexuosus Thurb. Rybd.) and black grama (Bouteloua eriopoda Torr.), two important Chihuahuan Desert forage species, had greater standing crop on the CG than IG range throughout the 1982-1991 study period. Our data indicate that some mesquite-dominated ranges in the Chilhuahuan Desert are responsive to both favorable rainfall and conservative stocking if residual perennial grasses remain, and that livestock grazing is sustainable under utilization levels that involve removal of one-third of the current year’s growth of key forage species (black grama, dropseeds, threeawns). On coarse sandy soils with a high canopy cover of honey mesquite, brush control may be necessary to initiate range recovery.