Submitted to: Restoration Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/6/2009
Publication Date: 3/2/2011
Citation: Davies, K.W., Sheley, R.L. 2011. Promoting native vegetation and diversity in exotic annual grass infestations. Restoration Ecology. 19:159-165.
Interpretive Summary: Exotic annual grass invasions are exceptionally difficult to control and manage because reestablishment of native perennial vegetation is often unsuccessful. We evaluated the potential of different treatments to promote native perennial vegetation still remaining in exotic annual grass infestations. Our results showed that native perennial vegetation could be promoted in exotic annual grass infestations by controlling annual grasses with imazapic herbicide and prescribed burning combinations. This suggests that exotic plant infestations with some native perennial vegetation remaining should receive higher priority for management than infestations that are lacking or have very limited native vegetation.
Technical Abstract: Exotic annual grass invasions are especially problematic because reestablishment of native perennial vegetation is rarely successful. It may be more appropriate to treat exotic annual grass infestations that still have some remaining native vegetation. The purpose of this study was to determine if prescribed burning, imazapic herbicide, and their combinations would promote native vegetation remaining in exotic annual grass infestations. We evaluated the effects of spring burning, fall burning, fall applied imazapic, spring burning with fall applied imazapic, and fall burning with fall applied imazapic on the exotic annual grass, medusahead (Taeniatherum caput-medusae (L.) Nevski), and native vegetation at six sites in Oregon for two years post-treatment. Medusahead infestations included in this study had some residual native perennial bunchgrasses and forbs. Burning followed by imazapic application provided the best control of medusahead and resulted in the greatest increases in native perennial vegetation. However, imazapic application decreased native annual forb cover the first year post-treatment and density the first and second year post-treatment. The spring burn followed by imazapic application produced an almost 2-fold increase in plant species diversity compared to the control. The fall burn followed by imazapic application also increased diversity compared to the control. Results of this study indicate native plants can be promoted in medusahead invasions; however, responses vary by plant functional group and treatment. Our results compared to previous research imply that restoration of plant communities invaded by exotic annual grass may be more successful if efforts focus on areas with some residual native perennial vegetation.