Role of grazing in shrub invasion and desertification

TitleRole of grazing in shrub invasion and desertification
Publication TypeConference Paper
Year of Publication1993
AuthorsLaca E.A., Launchbaugh K.L., Fredrickson E.L., Estell R.E., Ksiksi T.
Conference NameTexas Tech University, Research Highlights: Noxious Brush and Weed Control, Range and Wildlife Management
Date Published1993
AbstractDesertification is a serious problem in vast areas of the U.S. and worldwide. Studies of shrub invasion and desertification in the Chihuahuan Desert of New Mexico generally accept that livestock can promote shrub invasion by preferentially grazing related to toxicosis. Because they remain ungrazed, shrubs invade and outcompete desirable grasses. Shrub invasion starts a cycle of erosion and nutrient loss between shrubs, which furthers the decline of grasses and promotes aridity. We started a project to study the feasibility of manipulating the toxicity of shrubs and dietary preferences of sheep to reduce shrub invasion. In our first experiment, carried out at the USDA Jornada Experimental Range, we studied the variability of tarbush intake among individuals in a flock of ewes. A flock of 32 polypay ewe lambs were moved daily through five 0.3-acre paddocks for a total of 10 days. Paddocks were similar and bad abundant by the bite-count technique. Blood was drawn from each ewe at the beginning and end of the experiment to assess toxicity effects. Preliminary observations indicate that sheep strongly preferred grasses to tarbush. Tarbush intake was low, even after grasses had been depleted considerably. Not toxicity effects were detected by blood analysis. Animals that exhibited the lowest and highest intake of tarbush will be tested later in controlled conditions to assess individual variation in ability to tolerate (or detoxify) tarbush.