Submitted to: Extension Reports
Publication Type: Experiment Station
Publication Acceptance Date: May 1, 2008
Publication Date: June 1, 2008
Citation: Davies, K.W. 2008. Medusahead establishment and dispersal in sagebrush-bunchgrass communities. Extension Reports. Range Field Day 2008 Progress Report. Oregon State University Agricultural Experiment Station, Special Report 1085. Burns, OR. pp. 31-34. Interpretive Summary: Medusahead is an invasive annual grass that reduces biodiversity and production of rangelands. To prevent medusahead invasion land managers need to know more about medusahead seed dispersal and establishment. Medusahead seed dispersal was measured using seed traps and medusahead establishment was evaluated by introducing medusahead at non-infested sites. Medusahead dispersed relatively short distances (= 2 m) from established infestations. The establishment of medusahead decreased as large perennial bunchgrasses density increased. These results suggest that containment efforts around medusahead infestations would only have to be a few meters wide to be effective and that promoting or maintaining large perennial bunchgrasses can reduce the establishment success of medusahead. Land managers can use this information to contain medusahead infestations, increase the resistance of plant communities to medusahead invasion, and identify plant communities that are susceptible to medusahead invasion.
Technical Abstract: Medusahead is an invasive annual grass that reduces biodiversity and production of rangelands. To prevent medusahead invasion land managers need to know more about its invasion process. Specifically, 1) the timing and spatial extent of medusahead seed dispersal and 2) the establishment rates and interactions with plant communities being invaded. Medusahead seeds dispersed between July and October and did not disperse more than 6.6 feet from their source, without human or animal transport, suggesting relatively narrow containment barriers around medusahead infestations may be sufficient to significantly slow spread. The ability of medusahead to establish in a plant community was negatively correlated to large perennial grass density. Thus, maintaining large perennial grass is critical to preventing medusahead invasion and increasing large perennial grass density should reduce the susceptibility of a site to medusahead invasion.