The Greater Yellowstone Ecosystem, revered its beauty and its vastness as one of the most intact temperate ecosystems in the world, is threatened by massive wildfires, insect infestations, and millions of annual tourists. But perhaps the greatest threat to the ecosystem is the spread of invasive species; over 15% of documented flora in Yellowstone National Park is non-indigenous. Invasive plants in a particularly invaded area in the northern, semi-arid elk range of the park, the Gardiner Basin, have been targeted with an ambitious and comprehensive revegetation pilot project. Launched in 2008, native grass establishment success been plagued by variable spring water conditions. This study looks at microtopography (human-made surface roughness, creating microclimates of topographic highs and lows) on four revegetation sites as a means for improving soil water storage, and thereby reducing drought-stress and emerging native grasses competition with non-native plants. Soil moisture measurements are being constantly tracked in micro-highs and micro-lows. During peak growing season, native versus invasive plant densities will be measured and compared to precipitation, temperature, and soil moisture data. Microtopography has the potential be an inexpensive and relatively simple fix for building soil water storage and lessening plant establishment reliance on early spring moisture.
Large-scale microtopography using a chain disker or a diker bar has been shown to nearly triple grass densities in field experiments. Results presented will include soil moisture data from micro-highs and micro-lows, as well as revegetation establishment of native grasses versus invasive plants from the 2017 growing season. Combinations of treatments (microtopograhy, herbicide applications, and surface soil amendments) will also be addressed for their efficacy of reducing invasive plant densities and encouraging native grass growth. A separate greenhouse study mimicking drought conditions will help clarify the water use efficiency relationships (isotopic analyses of δ13C) between native and non-native species under stress-inducing environmental conditions. In addition, microbial respiration analyses can be used to implicate soil moisture conditions as microbial communities strongly correlate with temperature and moisture. These data, collected over several field seasons, can help land managers decide if surface roughness might be a potent restoration tool for semi-arid landscapes that may become more susceptible to invasion in the face of climate change.