JUNIPER DEBRIS BURNING IMPACTS ON PLANT SUCCESSIONAL DYNAMICS

Authors: Bates, Jonathan - Jon; Svejcar, Anthony

Submitted to: Society for Range Management Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 8/10/2006
Publication Date: 2/9/2007
Citation: Bates, J.D., Svejcar, A.J. 2007. Juniper debris burning impacts on plant successional dynamics [abstract]. Society for Range Management Meeting. Paper No.25

Interpretive Summary: Understanding the impacts of prescribed burning on the invasibility of Wyoming big sagebrush-bunchgrass communities after a short recovery period is needed to make informed management decision regarding prescribed burning. We evaluated the invasibility of six Wyoming big sagebrush-bunchgrass communities in the fourth year after prescribed fall burning by introducing cheatgrass into burned and unburned (control) treatments. Cheatgrass establishment was greater in the control than burned treatment. The burned treatment had less bare ground and inorganic nitrogen and greater total herbaceous cover, density, and production than the control treatment. Our results suggest prescribed fall burning of late seral Wyoming big sagebrush-bunchgrass communities stimulated the herbaceous component and increased the resistance of the communities to cheatgrass invasion four years post-burn. This implies that Wyoming big sagebrush-bunchgrass communities may need to be infrequently burned to maintain the balance between sagebrush and herbaceous dominance.

Technical Abstract: Prescribed fire and mechanical cutting are the main treatments used to remove western juniper and restore sagebrush-steppe in eastern Oregon. Mechanical treatments have commonly prescribed leaving cut juniper on site. Evidence has suggested that retaining cut trees (juniper debris) reduced runoff and erosion, enhanced establishment of perennial grasses, and retained nutrients on site. Disadvantages to leaving juniper debris is the increased fuel hazard, particularly in the first 2-3 years post-treatment when needles remain suspended on downed trees. Juniper debris may also enhance growth by cheatgrass and slow recovery of perennial species. Recently, efforts have shifted to removing juniper debris by burning in the late fall and winter to reduce potential fire hazards. This study evaluated the response of herbaceous vegetation to winter burning of juniper debris. Vegetation response was compared among two burning treatments (burning the first winter after cutting and burning the second winter after cutting), a control (cut and unburned juniper), and interspace. Debris was burned when soils and ground litter were frozen and/or at field capacity to minimize the impacts of fire to perennial herbaceous vegetation. We hypothesized that burning would not increase mortality of herbaceous perennials compared to the unburned control, would speed perennial herbaceous recovery compared to the unburned control, and as a result would reduce the potential for annual grasses to establish when compared to the unburned control. Debris burning did not increase perennial grass mortality when compared to unburned controls. In the 10th year after cutting, herbaceous and perennial grass cover were 1.5 to 2-fold greater under burned debris treatments compared to unburned controls. Cheatgrass cover was twice as great in the unburned control than the burned debris treatments and the interspace. Burning debris under the described conditions was concluded to have enhanced recovery of native perennials compared to leaving juniper debris unburned.