Author
|
Submitted to: Meeting Abstract
Publication Type: Abstract Only Publication Acceptance Date: 1/29/2013 Publication Date: 1/29/2013 Citation: Clements, D.D., Harmon, D.N., Blank, R.R., Young, J.A. 2013. Rehabilitation of degraded rangelands: lessons learned. Meeting Abstract. 13:1. Interpretive Summary: Technical Abstract: The introduction and subsequent invasion of cheatgrass (Bromus tectorum) has had astronomical effects to Great Basin rangelands. Cheatgrass has truncated secondary succession by outcompeting native plant species for limited resources, thus building persistent seed banks that take advantage of conditions that occur in arid environments. The presence of cheatgrass has increased the chance, rate, spread and season of wildfires from an estimated 60-110 years down to as frequent as every 5-10 years, simply too short of a period of time to allow native shrubs and other desirable species to return to the site. The wildfire storms that occurred in 2012 on Great Basin rangelands are a result of fuel buildups of cheatgrass from 2010-2011. The implementation of rest rotation grazing significantly contribute to these fuel buildups. Rest rotation grazing was developed for perennial grass communities; the presence of annual grasses such as cheatgrass completely changes the opportunity for perennial grasses to benefit from rest rotation grazing simply because cheatgrass outcompetes native perennial grass seedlings with or without grazing. Ray Evans pointed out more than three decades ago that as little as 4 cheatgrass plants/ft² can outcompete native and introduced perennial grass seedlings. It is not uncommon to have more than 100 cheatgrass planta/ft² throughout the Great Basin. The establishment of long-lived perennial grasses is the key at suppressing cheatgrass densities and fuel loads. The use of natural and prescribed fires in big sagebrush (Artemisia tridentata) communities can open a window for successful rehabilitation efforts as these fires burn hot enough for a long enough period of time to kill the majority of cheatgrass in the seed bank. On the other hand, a wildfire in a cheatgrass dominated community burns so fast that live seeds are numerous in the seed bank as well as on the surface of the soil. The decrease in available nitrogen also limits cheatgrass germination the 1st fall and spring following the wildfire, therefor decreasing the competition that desirable seeded species will face the following spring. Seeded species experienced 152% increase in seedling establishment when seeded the 1st fall versus 2nd fall following the wildfire. If you miss seeding the 1st fall following a big sagebrush wildfire, the window drastically closes and any success is very limited. Mechanical and herbicide treatments are also tools that can be used in decreasing cheatgrass seed bank densities. Mechanical fallows decreased cheatgrass seed banks by 89% therefor reducing the cheatgrass competition that seeded species faced in the seedling stage. Herbicide treatments reduced cheatgrass above-ground densities by as much as 99% and also experienced increased seedling establishment of desirable seeded species. The rehabilitation of degraded rangelands shows promise when all the tools in the management tool box are available for an integrated approach. |
