Evaluating the impact and invasiveness of cheatgrass in rangelands and dryland wheat systems
Research and management of cheatgrass (Bromus tectorum) is especially important as its distribution and abundance in Montana is predicted to increase with decreasing regional precipitation and increasing mean temperatures. The purpose of this research is to gain a greater understanding of climate and disturbance factors leading to cheatgrass invasion in Montana’s rangelands and wheat fields, and how to prevent and control it.
While much research has been conducted on cheatgrass in the intermountain west, very little has been conducted in Montana. Recently, members of the MSU Weed and Invasive Plant Ecology and Management Group have conducted studies on cheatgrass biology and management. Noelle Orloff, Jane and Fabian (2013) investigated the effects of nitrogen fertilizer on competition between cheatgrass and bluebunch wheatgrass. This study found that young bluebunch wheatgrass was more competitive with cheatgrass when given even a small (~two weeks) advantage in emergence timing, but was suppressed when cheatgrass emerged earlier – as it does under natural conditions, and this advantage may increase under warmer winter conditions. Tanya Skurski, Lisa and Bruce (2012) assessed the impacts of cheatgrass and herbicide management on rangeland in southwestern Montana. Her research generally showed no or minimal relationships between cheatgrass presence and native species richness and diversity. However, the research did show that in many cases where spotted knapweed was successfully controlled with herbicide, cheatgrass invaded or increased – thus swapping one noxious weed for another potentially even less desirable species. Krista Elhert and others in the group (in press) conducted a greenhouse study where herbicide was combined with the soil-borne pathogenPyrenophora semeniperda in an effort to enhance cheatgrass control, and results suggested P. semeniperda can be used to reduce cheatgrass emergence while herbicide can be used to kill those individuals that escape pathogen-induced mortality. Most recently, we have analyzed cheatgrass response to fire around the intermountain west and found that cheatgrass is more invasive and responsive to fire where winters are warmer and precipitation falls more as rain than snow, which is currently the climate to the south and west of us where cheatgrass is especially problematic (Kimberley Taylor and others in the group (accepted)).
Notably lacking is research conducted in Montana that evaluates cheatgrass populations after fire, and how a warming climate may change the competitive advantage to cheatgrass rather than our current desired vegetation. Our preliminary results show cheatgrass cover is similar before and after fire, except along fire containment lines where there is greater cover of cheatgrass and reduced cover of native bunchgrasses, likely a result of soil disturbance. Christian Larson is evaluating the effect of climate on the invasiveness of cheatgrass in sagebrush steppe using open top chambers (see photos below); and, we are conducting a similar experiment in a wheat system. Krista’s research on P. semeniperda will increase our understanding of its ability to reduce cheatgrass emergence and growth in relation to off-target impacts on desirable grasses. We believe such research is essential for managing cheatgrass and maintaining healthy grazing lands as it will provide information to guide future grazing and prescribed burn practices in Montana to best control and minimize the spread of cheatgrass, particularly as our climate continues to change.
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