Establishment and trends in persistence of selected perennial cool-season grasses in the western United States

Authors: Rigby, Craig; Jensen, Kevin; CREECH, J - Utah State University; THACKER, ERIC - Utah State University; Waldron, Blair; Derner, Justin

Submitted to: Rangeland Ecology and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/15/2018
Publication Date: 9/20/2018
Citation: Rigby, C.W., Jensen, K.B., Creech, J.E., Thacker, E.T., Waldron, B.L., Derner, J.D. 2018. Establishment and trends in persistence of selected perennial cool-season grasses in the western United States. Rangeland Ecology and Management. 71(6):681-690. https://doi.org/10.1016/j.rama.2018.06.008.
DOI: https://doi.org/10.1016/j.rama.2018.06.008

Interpretive Summary: Large-scale conversion of western US rangelands from a diverse, healthy, perennial plant-dominated ecosystem such as the lower-elevation Basin and Wyoming big sagebrush rangelands to invasive annual grasses, particularly cheatgrass and medusahead has been attributed to wildfires, human activities, and drier, hotter growing conditions. In the Great Basin for example, cheatgrass is estimated to have displaced approximately 10 million ha of native perennial vegetation. As a result of annual grass invasion, wildfire frequency and size are increasing. There is a loss of soil due to increased erosion, a decline in watershed quality and plant diversity. Experiments were conducted at four semiarid rangeland locations in Idaho (1), Wyoming (1), and Utah (2) addressing seedling establishment and plant persistence of 8 perennial cool-season grass species. Native grass species were able to persist after five years similar (plants m-2), check species Siberian and crested wheatgrasses, ranked from most persistent to least persistent, across the four locations were thickspike wheatgrass, Snake River wheatgrass, western wheatgrass, basin wildrye, and bluebunch wheatgrass. This study provides additional data that native grasses over multiple environments to include Sagebrush basins and slopes, sagebrush steppe valleys, woodland- and shrub environments are capable of establishing and persisting and should be considered as important seed mix components in these regions.

Technical Abstract: The rate of large-scale conversion of western US rangelands from a diverse, healthy, perennial plant-dominated ecosystem to invasive annual grasses, particularly cheatgrass and medusahead is increasing. Contributing to this increase is the use of native grasses that do not establish or persist in the presence of cheatgrass and medusahead. Recent plant breeding efforts have centered on developing native grasses with better seedling establishment and persistence (plants m-2). However, data are lacking that document newly developed native grass establishment and persistence across geographically-diverse locations. Experiments were conducted at four semiarid rangeland locations in Idaho (1), Wyoming (1), and Utah (2) addressing seedling establishment and plant persistence of 14 perennial cool-season grass species. Across all environments, native grass seedling establishment of bottlebrush squirreltail (26 seedling m-2), bluebunch wheatgrass (26), slender wheatgrass (26), and Snake River wheatgrass (26) were similar to Vavilov II Siberian wheatgrass (30). However, by year five, western wheatgrass, Snake River, and thickspike wheatgrasses were the only native grasses to have plant densities similar to Vavilov II (35) and Hycrest II crested wheatgrass (31). These data suggest that many native grasses are able to establish but stil lack the ability to persist and compete in the presence of cheatgrass and others. Despite having reduced seedling densities, rhizomatous western wheatgrass increased in plant density. Knowledge of seedling establishment and plant persistence of these new cultivars across diverse geographical locations enhance decision-making for land managers to increase the potential for greater likelihood of a successful revegetation project.