Title: Prescribed burning in mid and late successional juniper woodlands Authors
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: March 31, 2010
Publication Date: May 18, 2010
Citation: Bates, J.D., Rhodes, E., Davies, K.W., Sharp, R. 2010. Prescribed burning in mid and late successional juniper woodlands [abstract]. Central Oregon Fire Science Symposium. Technical Abstract: Western juniper woodlands of the western United States have expanded rapidly since settlement in the late 1800’s. To recover shrub steppe and other plant communities requires that invasive junipers be controlled. We have evaluated recovery of several plant associations after combinations of juniper cutting and prescribed fire treatments were applied, in mid (Phase 2) and late successional (Phase 3) juniper woodlands. Pre-burn cutting involves cutting a portion of the trees present and permitting them to dry for a month to a year prior to applying fire. The cut trees increase surface fuels to carry fire and kill remaining junipers. The objectives of these studies have been too: assess what percentage of stands require preparatory cutting to carry fire and eliminate remaining invasive juniper; monitor and compare seasonal fire applications, determine the impacts of fire to understory species; and evaluate early post-fire successional dynamics. The shrub/understory on all sites was dominated by native vegetation with trace amounts of cheatgrass. We determined that for prescribed burning in the early fall a maximum of one–quarter of the trees need to be cut in Phase 3 woodlands to carry fire and kill remaining junipers, assuming a minimum density of 75-100 mature trees per acre. However, when prescribed burning in the winter and early spring, juniper cutting levels must be increased. Prep cutting was determined to be unnecessary to burn Phase 2 woodland sites. The recovery of shrubs, aspen, and herbaceous plants has varied depending on site, woodland successional phase, and time of fire. In Phase 3 woodlands the impact of the fires to the understory and early successional stages were similar to those documented for high intensity/severity fires in forested systems. Perennial bunchgrass mortality ranged from 50% to 95%. Early succession in cut-and-burn treatments was either dominated by native annual and perennial forbs or cheatgrass. On sites dominated by native forbs remaining perennial bunchgrasses were rapidly reseeding these areas; on these sites native herbaceous plants will dominate the recovery. On sites now dominated by cheatgrass perennial bunchgrasses have been slow to reestablish; it remains uncertain whether these areas will fully recover their potential. Recovery periods of shrub species will take longer than reported in the literature because shrub cover and densities were already low as a result of western juniper dominance and the fires killed all non-sprouting species. To minimize damage to herbaceous vegetation, winter and early spring burning of Phase 3 juniper woodlands has resulted in greater recovery of shrub and herbaceous species than fall burned sites. However, recovery of quaking aspen has been greater following fall fire compared to early spring fire. Burned Phase 2 woodland sites were all dominated by native herbaceous vegetation and shrubs were recovering faster than treated Phase 3 woodlands. Burning Phase 1 and 2 woodlands likely provides the highest probability for successful recovery of shrub steppe plant communities. Early fall burning is riskier as post fire succession has the potential to be dominated by invasive annual grasses.