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Submitted to: The Progressive Rancher
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 7/7/2013 Publication Date: 9/5/2013 Citation: Clements, C.D., Young, J.A., Harmon, D.N., Blank, R.R. 2013. Rehabilitation of cheatgrass-infested rangelands: applications and practices. The Progressive Rancher. 13(7):30-31. Interpretive Summary: This is the second part of a three part series specifically addressing lessons learned in the process of applications and practices used to rehabilitate cheatgrass-infested rangelands. The best known method at suppressing cheatgrass densities and fuel loads requires the establishment of long-lived perennial grasses. Moreover, one must tailor rangeland rehabilitation practices to site-specific realities to assure success. For example, compare post-wildfire conditions between a fire occurring in a Wyoming big sagebrush community, and one occurring in a previously burned area now dominated by cheatgrass. In general, the presence of big sagebrush portends a better rehabilitation opportunity. In a big sagebrush-dominated community fires are hot and a sizable portion of cheatgrass in the seed bank is killed. Subsequent rehabilitation efforts can be more successful because newly recruiting sown seeds will face less competition from cheatgrass. Also, following these big sagebrush-dominated fires there is a decrease in available nitrogen, which is not advantageous to cheatgrass. A wildfire in a cheatgrass-dominated community, on the other hand, burns fast and is relatively cool; cheatgrass litter is not completely consumed and enormous levels of viable cheatgrass seed remain in the seed bank. We investigated the rehabilitation of big-sagebrush communities by taking advantage of a 2006 wildfire in a degraded Wyoming big sagebrush/bunchgrass community north of Reno, Nevada. We report that seeding the first fall following the wildfire is significantly more successful than seeding the second fall even though the second fall seeding received 9.3” of precipitation compared to 5.7” of precipitation the first fall seeding treatment. How does one rehabilitate cheatgrass-dominated sites? Successful rehabilitation requires deft use of all tools available mechanical implements, herbicides, and a variety of native and introduced plant materials. Discing cheatgrass in the spring before it heads out can provide an open window/opportunity to establish long-lived perennial grasses in an effort to suppress cheatgrass. What this discing effort does is kill the standing crop of cheatgrass before seed production, but at the same time bury a large portion of the remaining cheatgrass seed in the seed bank to deeper depths that decreases the active cheatgrass seed bank and germination. We have routinely measured an 80% decrease in cheatgrass seed bank densities following discing. Following the discing application (@ about 4” depth), the site is then fallowed all summer storing soil moisture and valuable nutrients and then seeded to the desirable selected species of long-lived perennial grasses that fall. The next spring the seedlings of seeded species are emerging and competing against a significantly lower cheatgrass population, more available soil moisture and nutrients, therefore increasing the seedling survivability and establishment of seeded species to actively suppress cheatgrass. In our replicated plots, we measured a 300% increase in seeded species, 0.4/ft² in the undisced compared to 1.2/ft² in the disced plots. Herbicides can be a very useful tool available to land owners and resource managers when attempting cheatgrass control and rehabilitation practices in an integrated approach, but using herbicides must be approached using the upmost caution; misuse of these chemicals can result in certain herbicides being taken off the market and out of the tool box. The first thing to understand is that these soil-active herbicides are not selective. At proper rates and proper timing these herbicides will not kill established perennial grasses, but at the seedling stage they can effectively kill annual or perennial seedlings. That is why we apply these herbicides in the fall of the year, fallow the site for 1-year, and then seed the site th Technical Abstract: The challenges that land owners and resource managers face when trying to attempt applications and practices when attempting to rehabilitate rangelands infested with cheatgrass (Bromus tectorum) are over-whelming. Simply purchasing seed and spreading it throughout the rangelands is doomed for failure. In this paper, second of a three part series, we provide on-the-ground realities that we hope will lead to better approaches when attempting these rehabilitation practices. Following summer and late summer wildfires, it is not uncommon to have the seeding operations occur in sites that are doomed for failure or practices that have the same fate. We investigated the importance of proper timing of seeding operations as well as proper seed selection. Our results point out that seeding the first fall following the wildfire and the use of native and introduced species in a mix are significantly more successful than using native species by themselves, 3/ft² compared to the best performing native species, bottlebrush squirreltail (Elymus elymoides), at 0.4/ft². Also, the suppression of cheatgrass was significant as Crested wheatgrass (Agropyron cristatum) effectively suppressed cheatgrass by decreasing above-ground densities: 2/ft², compared to bottlebrush squirreltail, 52/ft². How does one rehabilitate cheatgrass-dominated sites? Such sites are now the norm over much of the northern Great Basin and are most difficult to rehabilitate following wildfires. Indeed, many habitats are not even seeded and those that are, are often a waste of effort and money with little or no suppression of cheatgrass, yet they are important habitats for wildlife, grazing resources, etc. Successful rehabilitation requires deft use of all tools available including mechanical implements, herbicides, and a variety of native and introduced plant materials. Discing cheatgrass in the spring before it heads out can provide an open window/opportunity to establish long-lived perennial grasses in an effort to suppress cheatgrass. What this discing effort does is kill the standing crop of cheatgrass before seed production, but at the same time bury a large portion of the remaining cheatgrass seed in the seed bank to deeper depths that decreases the active cheatgrass seed bank. We have routinely measured an 80% decrease in cheatgrass seed bank densities following discing. Following the discing application (@ about 4” depth), the site is then fallowed all summer storing soil moisture and valuable nutrients and then seeded to the desirable selected species of long-lived perennial grasses that fall. The next spring the seedlings of seeded species are emerging and competing against a significantly lower cheatgrass population, more available soil moisture and nutrients, therefore increasing the seedling survivability and establishment of seeded species to actively suppress cheatgrass. In our replicated plots, we measured a 300% increase in seeded species, 0.4/ft² in the undisced compared to 1.2/ft² in the disced plots. Our latest experiments have been focusing on the testing of three separate herbicides, 1) Imazapic (Plateau), 2) Rimsulfuron (Matrix), and 3) Sulfometuron Methyl (Landmark) and their possible effectiveness at controlling cheatgrass and improving rehabilitation success. Matrix did not perform well as it does not control Russian thistle, resulting in overly dense Russian thistle (Salsola tragus) populations in our plots that significantly contributed to the mortality of seedlings of seeded species. In our other replicated experimental plots, however, cheatgrass above-ground densities were decreased by 95.6% using Plateau (@ 6oz/ac rate), and 98.7% using Landmark (@ 1.75oz/ac rate). Using these herbicides, along with seeding long-lived perennial grasses, we have experienced a 700% increase in seeded species success, 0.3/ft² in the control plots v |
