Date of Award:
Master of Science (MS)
Sagebrush communities in the Great Basin face many threats. Cheatgrass, a winter annual from Eurasia, has invaded these communities, increasing wildfire and lowering species diversity. Additionally, climate models project warmer and drier conditions throughout much of the Great Basin, likely increasing drought, cheatgrass invasion, and wildfire. Intact stands of native and introduced perennial grasses have been shown to limit invasion by cheatgrass and restore ecosystem functions. The objective of this research was to identify the functional traits and growth characteristics needed by restoration species to survive periods of drought and to evaluate varieties of commonly used restoration species for establishment, persistence, weeds, cheatgrass, and post-fire recovery over seven years in the Great Basin.
In a greenhouse experiment, I investigated the growth strategies and functional traits of cheatgrass and three species of perennial grasses under frequent and infrequent watering regimes. The perennial grasses included one native species, blue bunch wheatgrass, and two introduced species, crested wheatgrass and intermediate wheatgrass. After 48 days, roots and shoots were harvested and analyzed. Under a frequent watering regime, cheatgrass had significantly higher growth responses than the perennial grasses. However, under infrequent watering, restoration grasses had similar values of root tips, root mass, leaf mass and total productivity as cheatgrass, suggesting that restoration species may be more competitive with cheatgrass during periods of low water availability. Additionally, the results showed that blue bunch wheatgrass displayed different responses to water treatments when compared to the other species, with no change or increases in growth responses under infrequent water.
At research plots in Ephraim, UT, 52 varieties of 13 species of perennial grasses were planted in May 2015. Establishment data was collected in 2016. In November 2020, a fire burned all plots. Persistence, cheatgrass frequency, and frequency of weeds was measured in 2021 and 2022. Analyses showed that one group had significantly higher establishment and persistence and significantly lower frequency of cheatgrass than all other groups. This diverse group contained all varieties of crested wheatgrass, Siberian wheatgrass, and intermediate wheatgrass, along with some varieties of basin wildrye, bluebunch wheatgrass, Salina wildrye, Snake River wheatgrass, and thick spike wheatgrass.
The results of these studies demonstrate that a diversity of plant materials can establish, persist, and resist cheatgrass through drought and fire. This suggests the importance of understanding the functional traits possessed by each species and variety, and that species selection should be performed on the basis of functional traits that can meet management objectives.
Clifford, Adam M., "An Evaluation of Stress Tolerance in Restoration Plant Species in Response to Fire, Drought, and Invasive Plants Through the Lens of Functional Traits" (2023). All Graduate Theses and Dissertations, Spring 1920 to Summer 2023. 8886.
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