SOCIETY FOR RANGE MANAGEMENT Rehabilitation of Cheatgrass-Infested Rangelands: Concepts by Charlie D. Clements, James A. Young, Dan N. Harmon and Robert R. Blank.
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Range Scientist, US Department of Agriculture, Agricultural Research Service 920 Valley Road, Reno, NV 89512 charlie.clements@ars.usda.gov Range Scientist, US Department of Agriculture, Agricultural Research Service (retired) Agricultural Research Technician, US Department of Agriculture, Agricultural Research Service Soil Scientist, US Department of Agriculture, Agricultural Research Service
his paper is the first of a three part series addressing the issue of rangeland rehabilitation, specifically cheatgrass-infested rangelands. We use the term “rehabilitation” rather than “restoration” because “restoration is the intentional alteration of a site to establish a defined indigenous, historic ecosystem” which implies an ecosystem with no cheatgrass. Rehabilitation, on the other hand, is an effort to “repair damaged ecosystem functions”. Producing an environment free of cheatgrass and numerous other introduced weeds is not realistic, rehabilitation recognizes this and opens the tool box to more options not available in restoration. The introduction and subsequent invasion of cheatgrass throughout millions of acres of Intermountain West rangelands has resulted in astronomical changes to many plant communities. Cheatgrass is native to the cold deserts of central Asia where humans are first thought to have domesticated animals. These native habitats are very similar to the big sagebrush/bunchgrass and salt desert ranges of the Intermountain Area of North America. Cheatgrass was first collected in Pennsylvania in 1861 and thought to be accidentally
Figure 1. Look at the enormous amount of forage produced on this given year and the astronomical fire danger provided by this cheatgrass dominated community. introduced in contaminated wheat and then dispersed from farm to farm through equipment and stock. By 1902, cheatgrass was identified in Nevada and reported to occur along railways, roadsides and croplands. By 1935, cheatgrass was abundant throughout the Wyoming big sagebrush/bunchgrass communities. Cheatgrass has the inherent potential to outcompete native perennial grass seedlings for available moisture and nutrients therefore truncating succession. Whether 1” or 12” in height, or in stature, cheatgrass has the ability to produce many more seeds than is needed to sustain the population. The seeds of cheatgrass are highly germinable at a large range of constant and alternating temperatures. The USDA, Great Basin Rangelands Research Unit Wildland Seed Laboratory tests
the germination potential of numerous native and introduced species. In our testing of 55 constant or alternating temperatures from 0° C – 40° C that cover Great Basin seedbed temperatures, cheatgrass germinates in all 55 regimes, whereas native perennial grass species do not have that potential. Even though cheatgrass has this ability to germinate at a wide range of temperatures, a portion of seeds acquire a dormancy which allows cheatgrass to build persistent seed banks. In our investigation of 100 sites from northeastern California to eastern Nevada we measured 1,000 seed bank samples. Cheatgrass was present in the seed banks of all but one site, and ranged from 0 seeds/ft² to over 1,000 seeds/ft², averaging 252 cheatgrass seeds/ft². It is a rare event to record native grass and shrubs in these measured seed banks. Raymond Evans, early Range Scientist with USDA, Agricultural Research Service in Reno Nevada pointed out in the 1970’s that as few at 4 cheatgrass plants/ft² could outcompete our most competitive perennial grasses in then seedling stage. Cheatgrass is an annual grass that provides a fine-textured, early maturing fuel that increases the chance, rate and spread of wildfires. Wyoming big sagebrush/bunchgrass habitats that were estimated to burn every 60-100 years are now burning every 5-10 years, simply too short a period of time to allow for woody species like big sagebrush to return. Controversy exists as to how to manage these degraded big sagebrush communities with an understory of cheatgrass as well as those communities dominated with this annual grass (Figure 1). One of the myths that exist and is still taught on college campuses today is that “cows do not eat cheatgrass” or that “cheatgrass only provides forage during the green period.” We have witnessed cattle foraging on cheatgrass all 12 months of the year (Figure 2). Charles Fleming, pioneer range scientist with the University of Nevada, Agricultural Experiment Station wrote in 1942, “Bronco grass (sic cheatgrass) has become a permanent source of feed on many of our most important rangelands and it will necessarily have to be taken into consideration in the determination of seasonal use and in making grazing capacity estimates.” The lack of understanding by agencies and scientists to recognize the abilities of cheatgrass, as well as not recognizing it as a forage species, may very well have exacerbated the problem by allowing cheatgrass fuels to increase which has resulted in large astronomical wildfires. What is frustrating is that these early pioneer researchers and their work are often discarded as out of date, done without state of the art equipment, etc., yet their words ring more true today than they did decades ago. A. C. Hull and J. F. Pechanec published a paper in 1947 titled “Cheatgrass: A Challenge to Range Research” in which they point out “…we have tried grazing management for 20 years to aid perennial grasses and have increased cheatgrass seed production and dominance.” Howard Leach, a wildlife biologist with the California Department of Fish and Game during the late 1940s to the late 1970s, reported to us an interesting story concerning cheatgrass as wildlife forage. Howard told us that in the mid 1950s he was collecting mule deer stomach contents from road-killed deer in the Doyle area of northeastern California. He informed his supervisors mule deer were consuming sagebrush and was reprimanded. The next year he reported mule deer were consuming cheatgrass, and he was transferred. These biases still exist today. The problem is, that even though cheatgrass is a nutritional forage, it provides many more empty plate than full plate scenarios through its sporadic yearly growth/production patterns and its promotion of frequent wildfires. In 1994, we presented a paper at a scientific meeting where we showed a slide of sage grouse in dense cheatgrass at the edge of a degraded Wyoming big sagebrush/bunchgrass community (Figure 3). We pointed out that we met with the land managers and all involved parties, and discussed that simply protect-
The Society for Range Management (SRM) is “the professional society dedicated to supporting persons who work with rangelands and have a commitment to their sustainable use.” SRM’s members are ranchers, land managers, scientists, educators, students, conservationists – a diverse membership guided by a professional code of ethics and unified by a strong land ethic. This series of articles is dedicated to connecting the science of range management with the art, by applied science on the ground in Nevada. Articles are the opinion of the author and may not be an official position of SRM. Further information and a link to submit suggestions or questions are available at the Nevada Section website at http://www.ag.unr.edu/nsrm/. SRM’s main webpage is www. rangelands.org. We welcome your comments.
30 July / August 2013
The Progressive Rancher
www.progressiverancher.com