GRAZING INFLUENCES ON WATERING POINT VEGETATION IN THE CHIHUAHUAN DESERT

Long-term influences of livestock grazing on vegetation around watering points was studied on 2 upland Chihuahuan desert ranges in southcentral New Mexico using regression analysis. One range had been conservatively stocked since the 1950's while the other was more heavily stocked. About 45% of the climax vegetation occurred on the heavily stocked range compared to 70% on the conservatively stocked range. During 3 years of study, both ranges were stocked conservatively so annual utilization of the key forage grasses was 30-35%. Regression analyses showed black grama (Boueteloua eriopoda Torr.), mesa dropseed (Sporobolus flexuosus Thurb, Rybd.), threeawn (Aristida sp.), and total perennial grass standing crop increased as distance from water increased on the good condition range (P < 0.05). However, black grama and threeawn standing crop showed no association with distance from water on the fair condition range. Broom snakeweed (Xanthocephalum sarothrae Pursh.), the primary poisonous plant found on both ranges, was associated (r2 = 0.35) with distance from water only on the good condition range in April. Poisonous plants other than broom snakeweed decreased as distance from water increased with the exception of the fair condition range in October. No livestock losses from poisonous plants were noted on either range over the 3 years. We attribute this to the present conservative stocking rates. Our study supports the recommendation that downward stocking rate adjustments be made for the zone more than 1,600 m from water.