Submitted to: Eastern Oregon Agricultural Research Center
Publication Type: Experiment Station
Publication Acceptance Date: March 15, 2005
Publication Date: March 30, 2005
Citation: Jon Bates, Roger Sheley, Rob Sharp. 2005. South mountain juniper control study, annual report, 2004. Eastern Oregon Agricultural Research Center. 22p. Interpretive Summary: In the past 30 years efforts to restore plant communities in eastern Oregon have focused on removing juniper by mechanical means (chainsaws, bulldozers, chaining) and with prescribed fire. The purpose of this study has been to evaluate the use of cut juniper to increase cured surface fuels to carry a fire, kill remaining live trees, and restore the native plant community. Three cutting levels (25, 50, 75% of juniper trees) followed by prescribed burning were evaluated on plant communities on South Mountain, southwestern Idaho. The results showed that; (1) cutting only 25% of the trees was required to carry fire and removing remaining juniper, and (2) understory species cover was equal too or greater than cover prior to treatment. Reducing the level of cutting prior to applying prescribed fire will substantially reduce the cost per acre for removing juniper and would allow larger areas to be treated more cost effectively by private landowners and public land management agencies.
Technical Abstract: : Western juniper expansion into the sagebrush steppe diminishes forage production, reduces plant and wildlife diversity, and negatively impacts hydrologic function. In the past 30 years western juniper has mainly been controlled by cutting, using chainsaws, and by prescribed fire. Recently combinations of selective juniper cutting followed by prescribed fire have been used to remove juniper. The selective tree cutting is used to create a fuels base to carry prescribed fire through the remainder of the juniper stand. A main objective of the research was to assess what level of cutting is required to eliminate remaining juniper trees by fire in plant communities on South Mountain Idaho. The treatment components consisted of several levels of cutting manipulations followed by prescribed burning. Tree cutting manipulations were chainsaw cutting 25%, 50% and 75% of the post-settlement trees. Uncut (control) woodlands were located adjacent to cut areas. Control plots will remain as intact woodlands for comparing herbaceous and shrub response to the cutting and burning treatments. Plots were 1.2 acres in size and each treatment was replicated 5 times. Juniper trees were cut in October 2002 and allowed to dry for one year. Temporary livestock exclusion fences were built around plots in spring 2003. Prescribed fire was applied in October 2003. Regardless of cutting treatment the fire application was uniformly successful at removing remaining live junipers. On the Deep Soil sites the fire killed 95-99% of remaining live trees and juniper cover was reduced by 99%. On the Dry Soil sites the fires killed 85-100% of the remaining live trees and juniper cover was reduced by 90-94%. Results indicate that cutting about 25% of mature trees was sufficient to remove most remaining trees in a stand with fall prescribed fire. On the Dry Soil sites herbaceous cover increased across all treatment applications. On the Deep Soil sites results showed no significant change in herbaceous cover across all treatments. All treated sites had increased levels of bare ground as a result of reduced litter cover. Seeding trials were established in the fall of 2003 on both plant community types. Species seeded included Idaho fescue, Sherman big bluegrass, Goldar bluebunch wheatgrass, arrowleaf balsamroot, Lewis flax, and western yarrow. Species were evaluated individually and in combination at several rates. In 2004, there were extremely high establishment rates for all species except arrowleaf balsamroot. Establishment was enhanced by above average winter and summer precipitation.