Vegetation changes were evaluated over a 13 year period (1988-2000) on moderately grazed and lightly grazed rangelands in the Chihuahuan Desert of south central New Mexico. During the study period, grazing use of primary forage species averaged 49 and 26% on moderately and lightly grazed rangelands, respectively. Autumn total grass and black grama (Bouteloua eriopoda Torr.) standing crop were consistently higher on the lightly than moderately grazed rangeland throughout the study. Total grass standing crop declined on the moderately grazed rangeland when the last 3 years of study were compared to the first 3 years (10 versus 124 kg ha"1), but showed no change on the lightly grazed rangeland (320 versus 357 kg ha"1). Black grama, the primary perennial grass in the Chihuahuan Desert, increased in autumn standing crop on the lightly grazed rangeland, but decreased on the moderately grazed rangeland. Dropseed (Sporobolus spp.) autumn standing crop decreased on both rangelands during the study. However, this decrease was greater on the moderately grazed rangeland (97% decline) than on the lightly grazed rangeland (67% decline). Perennial grass survival following a 3-year period of below average precipitation was higher on the lightly grazed (51%) than the moderately grazed rangeland (11%). Severe grazing intensities on the moderately grazed rangeland during the dry period (1994-1996) appear to explain differences in grass survival between these 2 rangelands. Our study and several others show that light to conservative grazing intensities involving about 25-35% use of key forage species can promote improvement in rangeland ecological condition in the Chihuahuan Desert, even when accompanied by drought.
Figure 1. Basal area of black grama on meter-square quadrats protected from grazing and at 3 intensities of grazing on the Jornada Experimental Range, southern New Mexico, 1916-1953 (from Paulsen and Ares 2).
uring the past 5 years grazing capacity surveys have been increasingly used in range management decisions on both public and private lands in the western United States. They are also becoming more used in developing countries such as South Africa, Australia, Brazil, and Mexico. Range professionals and ranchers are better recognizing that successful range management depends on stocking rangelands so adequate vegetation residues remain to protect rangeland health, maintain multiple values, and insure economic viability. Recently there has been growing support for changes in existing government programs as well as new programs that would ellcourage conservative grazing on both public and private rangelands. Sound stocking rate and grazing capacity the number of animal units that will be assigned to the allotment. This is the basis for value o f the permit and grazing fees the rancher will pay. The best approach to determining safe stocking rate on rangelands is knowing the numbers of animals actually grazing a ranch or allotment over a period of years together with utilization levels, range trend analyses, and precipitation records. Incomplete andlor uncertain information on livestock numbers actually grazed, grazing use, and trend has created the demand for formal grazing capacity surveys to better establish the appropriate permit number. Increasingly, environmental groups are participating in the permit renewal process. They are prepared to challenge any decision not based on sound information and, in some Generally, grazing capacity is considered to be the average number o f animals that a particular range or ranch will sustain over time. It is based on stocking rate. Stocking rate is defined by the Society for Range Management as the amount o f land allocated to each animal unit for the gi-azable period of the year. Determination o f stocking rate and graring capacity involve the same procedures, except that grazing capacity estimates require adjustment of forage production to the hypothetical average year. W e define this hypothetical average year as the average forage production for the previous 10 year pei-iod. Ideally, at least 3 years of forage production data should be collected to establish grazing capacity. However, in reality this is often not possible due to management requirements for immediate information and/or funding limitations. Regression equations relating forage production to monthly and annual precipitation have been developed for specific range types. We have found them to be reasonably reliable if no major aberrations occur in precipitation during the survey year. We do caution that grazing capacity is part myth and part reality: The average number of livestock a ranch has carried over the previous 5, 10, or 20 years may have little relevance to what it will support in any given year or group of years. Applications of Grazing CapacityUnder present policy, livestock grazing permits on federal lands in the U S A are reviewed for renewal every 10 years. They also undergo review when the perm...
No abstract
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.