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Submitted to: Meeting Abstract
Publication Type: Abstract Only Publication Acceptance Date: 11/11/2013 Publication Date: N/A Citation: N/A Interpretive Summary: Technical Abstract: It has long been acknowledged the drastic change in fire cycles of the Great Basin rangelands due to cheatgrass (Bromus tectorum) invasion (Billings 1952, Young and Evans 1974, Wright 1980). An annual grass fire cycle now exists with return intervals less than 5 years compared to historical 60 to110 years (Whisenant 1990). This is simply too short of a period of time to allow for the return of critical browse species (succession). This leaves most habitats in a perpetual state of early succession dominated by cheatgrass. The chance, rate, spread and season of wildfires must be addressed; hence the reduction of cheatgrass associated fuels. There are various methodologies to decrease cheatgrass in the short-term (1-2 years) and “open a window of opportunity” to seed degraded rangelands. Mechanical (disking), fire, grazing and herbicide applications can reduce cheatgrass competition and fuels, but are not a sustainable means to reduce cheatgrass. The establishment of competitive long-lived perennial grasses (closed community) is the most reliable means to reduce cheatgrass invasion through soil drought (Robertson 1945). Along with using multiple tools, goals should be clearly stated to judge the successfulness of efforts. We believe that monitoring should occur for more than 5 years or at least greater than the short fire cycle (<5 years) causing the problems. If less than 5 years is not allowing the ecosystem to function or succession to occur we should then judge our rehabilitation effectiveness beyond that time period. The Agricultural Research Service (ARS) has the benefit of having multiple long-term dedicated research sites throughout the northwestern part of the Great Basin. This gives ARS a valuable breadth of knowledge when it comes to plant community change over- time. We present two case studies of integrated cheatgrass management research with monitoring occurring for 10 and 7 years. We contrast and compare similarities and differences of plant material testing, cheatgrass control (prior to seeding), cheatgrass suppression (seed banks) and the ultimate fate of each site after 3 years monitoring and then beyond five years. One study occurred at Orovada, Nevada and involved herbicide treatment and plant material testing in 1999 and 2000. We report the 2nd year perennial grass establishment (usually the only data reported in similar studies); 2002 perennial grass maximum = 2.3/ft²) and compare that to 2010 survival of perennial grasses = 1.4/ft². Cheatgrass suppression for 2002 = 1ft², 2010 = 9/ft², whereas the control plots = 62 and 92/ft², respectively). The other study occurred at Empire, Nevada in 2006 and involved plant material testing after a wildfire with mechanical (disking) control treatments. This site had very similar results to Orovada in the first 2 years; perennial grass = 9.3/ft², cheatgrass suppression = 1.3/ft²compared to 57.6 cheatgrass plants/ft² cheatgrass in 2008. Longer-term results though differed as the Empire site experienced a significant loss of perennial grass densities, 0.65/ft², which resulted in an enormous increase in cheatgrass, 69/ft². The loss of perennial grass dominance at the Empire site can be attributed to the extreme drought of 2011 and 2012 in combination with over-utilization. |
