The Sagebrush Cooperative

Management Issues: Weeds

Invasive plants, especially those classified as noxious weeds, are of particular concern in sagebrush steppe ecosystems. They disrupt native communities, diminish populations of at-risk native species, and threaten the economic productivity of resource lands. Movement and colonization of invasive plants has been on the increase during the last 20 years (ODFW 2006).

Invasive alien plants can affect native plants directly by monopolizing the landscape, or indirectly, by increasing soil nutrients, altering soil stability; promoting erosion; affecting the accumulation of litter, salt, or other soil resources; and promoting or suppressing fire (Vitousek 1990, Richardson et al. 2000). The effect of invaders is particularly dramatic in sage steppe communities where they alter disturbance regimes beyond the range of variation to which native species are adapted, resulting in community changes and ecosystem-level transformations (D’Antonio et al. 1999, Mack and D’Antonio 1998). In Wyoming big sagebrush habitat, the spread of cheatgrass (Bromus tectorum) and medusahead (Taeniatherum caput-medusae) increases the frequency, intensity, and spread of fires, replacing sagebrush and native bunchgrasses which are adapted to relatively infrequent fires. Invaders that alter fire regimes are widely recognized as some of the most important system-altering species on the planet (Vitousek 1990, D’Antonio and Vitousek 1992, D’Antonio 2000). An estimated 7.5 million acres of sagebrush steppe in Oregon is either invaded by invasive annual grasses or at high to moderate risk of imminent invasion (J. Rose, pers. comm.).

Restoration of habitats affected by invasive plants is difficult, slow, and expensive. Current efforts to address this issue emphasize prevention, risk assessment, early detection and quick control to prevent new invasives from becoming fully established (ODFW 2006). Land managers today are cooperating with partners through cooperative weed management areas and county weed boards, prioritizing efforts to focus on key invasives, and using a variety of appropriate tools (mechanical, chemical and biological) to control the most damaging invasive species. Key audiences and the general public are being educated to identify noxious weeds and take appropriate steps to mitigate habitat degradation (ODFW 2006). Programs such as the Ecologically-Based Invasive Plant Management (EBIPM) techniques developed by the Eastern Oregon Agricultural Research Center-USDA ARS provide methods for managing invasive weeds using science-based solutions to treat the true causes of invasion. This particular program combines state and transition models and successional management as a framework to make the best management decisions for a given landscape based on ecological principles.