LRES M.S. Thesis Defense
- Wednesday, May 2, 2018 at 2:00pm
- Animal Biosciences Building, 134 - view map
Restoring Semiarid Lands with Microtopography
Water is often limiting to plant establishment in semi-arid lands, and this limitation can be especially pronounced in restoration contexts where poor soils and/or non-native plants are present. The application of herbicide and mulch are two techniques that can help retain soil moisture by either killing unwanted plant species or lowering evaporative losses, respectively. Creation of microtopography, or soil surface variation, is a third technique that could alleviate growing season water shortages. Here we report findings from a randomized block design used to explore the absolute and relative advantages of these three techniques at three co-located sites in a semi-arid region of northern Yellowstone National Park. We found plant cover in control plots averaged 60%. Across the plots treated singly with herbicide, mulch, or microtopography, we found that only mulch and microtopography improved cover (74% and 72%, respectively), although the increase consisted mostly of non-native species. Herbicide applications, not surprisingly, reduced plant cover to 35% the first growing season after imposing treatments. Treatment combinations yielded some surprises including unexpected interactions between sites and treatments. For example, herbicide efficacy at reducing canopy cover was similar across all sites (~40%), although only at our Cinnabar site did herbicide reduce canopy covers to near 0%; when combined with mulch, however, these herbicide treatments were even more effective at reducing canopy covers of non-native dominated plots. Conversely, mulch as a single restoration treatment increased plant densities, but only at Cinnabar, which had a plant community dominated by winter annual plants as opposed to the Reese Creek sites, which had both winter and spring annuals. Taken together, our results highlight some of the challenges and complexities of restoration efforts in areas with legacy grazing and management effects as well as non-native species pressures; these same sites are also likely to experience increasing aridity. Of course, these challenges also represent opportunities, not just for insights into how best to combine ecologically sound restoration strategies, but also for improved tracking and reporting of both treatment histories as well as treatment outcomes that together can help quantify fidelity of implementation, a necessary precursor to broader adoption of cost-effective specific restoration approaches.
- Department of Land Resources and Environmental Sciences