|JOHNSON, DUSTIN - Oregon State University
Submitted to: Rangeland Ecology and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/5/2012
Publication Date: 3/26/2013
Citation: Davies, K.W., Nafus, A., Johnson, D.D. 2013. Are early summer wildfires an opportunity to revegetate exotic annual grass-invaded plant communities?. Rangeland Ecology and Management. 66(2):234-240.
Interpretive Summary: Medusahead is an exotic annual grass degrading wildlife habitat and decreasing forage production on rangelands. Revegetation of medusahead-invaded plant communities is needed to increase livestock forage production and improve wildlife habitat. Our objective was to determine if early summer wildfires and fall drill seeding could be used as a treatment combination to decrease medusahead and increase perennial vegetation. Perennial grass cover and density increased and medusahead decreased with this treatment. However, medusahead density was still high three years after treatment, suggesting that additional treatments may be needed to be fully successful.
Technical Abstract: Medusahead (Taeniatherum caput-medusae (L.) Nevski) is an exotic annual grass reducing biodiversity and altering ecosystem function and processes in rangelands. Revegetation of medusahead-invaded plant communities is needed to improve ecosystem function, increase livestock forage production, and improve wildlife habitat. However, successful revegetation of invaded plant communities can be prohibitively expensive, because it often requires iterative applications of integrated control and revegetation treatments. Prescribed burning has been used to control medusahead and prepare seedbeds for revegetation, but burning has been constrained by liability concerns and produced widely varying results. Capitalizing on naturally occurring wildfires to help reduce medusahead and create a favorable seedbed for establishing seeded vegetation could reduce revegetation costs and alleviate liability concerns. Thus, our objective was to determine if early summer wildfires and fall drill seeding could be used as a treatment combination to decrease medusahead and increase perennial and native vegetation. The potential for early summer wildfire and fall drill seeding to be used to revegetate medusahead-invaded plant communities was evaluated at six sites. Treatments were 1) an early summer wildfire (July 2007) combined with a seeding treatment (burn and seed) and 2) a non-treated control. Introduced and native perennial grasses, total herbaceous vegetation (excluding exotic annual grasses), and annual forbs all increased with the burn and seed treatment (P < 0.5). Perennial grass density was 4.6- to 10.0-fold greater in the burn and seed treatment compared to the control (P < 0.05). Exotic annual grass density and cover in the third year post-treatment were lower in burn and seed treatment than the control (P < 0.05). However, exotic annual grass density was still > 130 individuals'm-2 in the burn and seed treatment. The density of exotic annual grass is concerning because medusahead may overtime displace perennial grasses and annual forbs that increased with the burn and seed treatment. Though not directly tested in this study, we suggest, based on other research that the burn and seed treatment may need to incorporate a pre-emergent herbicide application to further suppress medusahead and increase the establishment of seeded vegetation. However, it appears that early summer wildfires provide an opportunity to reduce the cost of integrated programs to revegetate medusahead-invaded plant communities.