Thirty Years of Rotation Grazing in the Mojave Desert

Item Type text; Article

Authors Hughes, Lee E.

Citation Hughes, L. E. (1998). Thirty years of rotation grazing in the Mojave Desert. Rangelands, 20(4), 6-8.

Publisher Society for Range Management

Journal Rangelands

Download date 26/09/2021 17:54:37

Item License http://rightsstatements.org/vocab/InC/1.0/

Version Final published version

Link to Item http://hdl.handle.net/10150/639134 6 RANGELANDS 20(4), August 1998

Thirty Years of Rotation Grazing in the Mojave Desert Lee E Hughes

emperatures nearly reach 120 degrees F in summer which includes the spring growing season. Hughes (1982) and drought reigns supreme during May, June and reported on the effect of the first ten to twelve years of op- rfJuly. That'son a so-called normal year. On dry years, erating under the grazing system on the forage species. which are frequent, the droughts may last months with The allotment has six key areas and they showed the fol- higher than normal temperatures. On wetter than normal lowing in 1982: (Trend, from 1974 to 1982, was measured years, the ground becomes covered with filaree (Erodium in 3 X 3 foot plots, using cover as the indicator): red brome cicutarium), (Bromus rubens), and other annu- WARM SEASON GRASSES (Big galleta): Occurred in als. The creosote bush (Larrea divaricata), bursage five of the six areas. decreased in three and key Big galleta (Ambrosia dumosa), Joshua Tree (Yucca brevifolia) key areas, did not change in one, and increased in one. turn from browns, whites and pale greens to true green. The foliage is abundant and is good livestock feed in winter COOL SEASON GRASSES (Squirreltail and Indian rice- One or both these cool and spring. grass): of seasons occurred in five of six of the areas. Three the areas lost The precipitation generally ranges from3 inches per year dur- key of key ing the dry cycle to 14 inches in a wet or El Nino event. all cool season grasses. The othertwo key areas had a cycle decrease. The Mojave Desert is not prime livestock country, but slight sheep and cattle have, during the 1 BOOs and 1900s, used it BROWSE (Bursage and winterfat): Winterfat occurred for grazing, especially in the winterand spring prior to mov- and increasedin one key area. Bursage occurred in four ing to mountainpastures. of six of the key areas and increased in all key areas. NON-FORAGE SPECIES were turpentine bush (Thamnosma montana), banana yucca (Yucca bacata), goldenhead (Acamptopappus spp.), snakeweed (Gutierrezia spp.), creosotebush, white burrobush (Hymenoclea salsola), and various cactus. These are all natives to the Mojave Desert, but, none were included in the small trend plots, however, they were all present in the key area. The other study carried out on the key areas was utilization of forage species. Utilization of forage by herbivores is measured by the Grazed Class Method. The method uses photo guides of key species to make utilization estimates (Schumtz, et al.1963). The estimates reflect herbage re- moved but also show herbage remaining. The range of utilization from 1970 to 1983 was 10 to 80%. Most of this was in the light category with some heavy to nearsevere utilization levels occurringthrough the thirteen years. The Beaver Dam Slope Allotment is located in northwest The Shivwits Resource Area grazing environmentalstate- Arizona on the Arizona Strip. Like many otherareas admin- ment (ES) on the Arizona Strip was completed in 1980. istered by the Bureau of Land Management,it had a three Prescribed average utilization was set at 50%; but it was pasture deferred rotation grazing implemented on it in becoming obvious that in the hot, dry Mojave Desert, occa- 1969. This system's goal was to begin curing some of the sional high utilization, that is any use that exceeded 50%, ills of overgrazing, caused by season-long grazing or con- was harmful to forage species. The trend and utilization tinuous grazing. studies seem to indicate that an average utilization at 35% and So, the question begs an answer: Did this rotation graz- less provided an opportunity for the forage to recover ing make a difference or better yet, did rotation grazing during wet cycles. Heavy utilization during the spring grow- change the plant species frequency? ing season would put forage at a disadvantage with non- forage plants in the coming heat and drought. Also, this is Some prime desert tortoise habitat and it's listing as a threatened History would mandate the need for lower utilization The allotment is from December to June. Two species levels grazed by livestock. Utilization levels from 1984 to 1996 wentdown pastures are rested during the growing season every other One to a range from 10 to 44%, compared to the 1970 to 1983 year. pasture is used from December to March, and utilization levels of 10 to 80%. receives growing season rest for nine months every year, RANGELANDS 20(4), August 1998 7

BEAVER DAM SLOPE Frequency Trend Pasture 1 Plot 4 Pasture3 Plot 6 100

w U 40 uJ U 0C-) z 20 0uJ w 0. 0

KeySpecies \ Non-KeySpecies

100

w C-) 0z 40

C-) 0 z 20 0 a-0 0 1981 1984 1986 1990 1996 1982 1953 1990 1996 YEAR YEAR

KeySpecies Non-KeySpecies Key Species \ Non-KeySpecies

Figure 1. Plant species frequency data for key areas of Beaver Dam slope allotment. Two categories ofvegetation are shown. The dark line is key species (all forage plants) and the light line shows frequency data for the all non-key (non-forage plants).

A New Look creased while non-forage species increased, then grazing Plant species were measured by the pace frequency managementwould be the suspect cause. method as described in Despain et al. 1991 during 1982 to 1996. Vegetation data was placed in two categories: key The Findings species(all forage plants) and non-key (all non-forage Frequencydata is displayed in Figure 1. The data shows plants) to determine if there were any trend differences that all key areas show parallel trends between the forage caused by grazing or if changes were due to other factors and non-forage, increasing or decreasing generally in re- (i.e. weather). My rationale on this was if forage species sponse to the precipitation (Figure 2). There is a general showed the same trend as non-forage species it meant the correlation to the amount of precipitation.The 1982—83pe- grazing system was affording the same growth opportunity riod was wet and the frequency of all plant species in the to forage as non-forage species. If forage species de- 1982—85period increased.The frequency of the vegetation 8 RANGELANDS 20(4), August1998

Ave Shivwits Plateau Recording Ppt Gage Elevations 4590' to 5920' (12-97, R. Smith) 25 24 - .- 23 22 21 2D IS IS I? U) a) 15 • 14 I) ii12 a-S0.. ID 8 7 6 5. 4

0 -— ______— 1981 1983 1985 1987 1989 1991 1993 1995 1997 1980 1982 1984 1986 1988 1990 1992 1994 1996 Year

Total Av.raga 13.23 YearPIAverage

Figure 2. Generalyearly patterns of precipitation across the Shivvits ResourceArea of the Arizona strip for the years shown.

decreased in the drier 1988—91 period and also with the dry Bibliography year of 1996. Despain, D.W., P.R. Ogden, and E.L.Smith, 1991. Plant An as to the Frequency Sampling for Monitoring Rangelands. Pg 17—21. In: Interpretation GrazingSystem G.B. Ruyle(editor) 1991. Some methods for monitoring range- So did the grazing system work? I say yes. The trend of lands. Universityof Arizona. the forage species was similar to that of the non-forage Hughes, Lee E. 1982. A Grazing System in the Mohave Desert. species. When the non-forage species were increasing due Rangelands4(6):256—257. to favorable weather conditions so did the forage species, Schmutz, E.M.,G.A. Holt, and C.C. Michaels. 1963. Grazed even received at some class method of estimating forage utilization.J. Range Manage. though forage species grazing point 16:54—60. in the grazing cycle. Lower utilization levels seemed to U. S. of the Interior. Bureau of Land allow a trend similar to that Department Management. of ungrazed non-forage plants. Shivwits Resource Area Proposed Grazing Management Draft However, did the grazing system make a difference or in- EnvironmentalStatement. Appendix 3—3. Pg 201 —201. crease forage plant frequency? This of course was the ob- jective of the allotment management plan. The only difference between the 1982 and 1996 frequency readings is that frequency of the non-forage species was down by no- table quantities of 20% or more. The re- forage species Author is Ecologistwith the Burea of Land Management,Arizona Strip mained at the same frequency in 1996 as in 1982. The District in St. George Utah. plant community where the Beaver Dam Slope allotment exists is stable with the usual fluctuations caused by cli- mate as seen in Figure I. The grazing system appears to have little affect on the forage plant community unless utilization levels go into the heavy or severe levels; and then the effect of forage species reduction or loss occurs as reported in The Shivwits Resource Area grazing ES and Hughes (1982).