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United States Department of Agriculture

Agricultural Research Service

Title: South Mountain Juniper Control Study Annual Report, 2003

Author
item Bates, Jonathan

Submitted to: Agricultural Research Service Publication
Publication Type: Other
Publication Acceptance Date: January 10, 2004
Publication Date: June 1, 2004
Citation: Bates, J.D. 2004. South Mountain juniper control study annual report, 2003. Eastern Oregon Agricultural Research Center. 18 p.

Interpretive Summary: 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. We estimated that on the Deep Soil sites the fire killed all remaining live juniper. On the Dry Soil sites we estimated that the fire killed 85-100% of the remaining live trees. Results indicate that cutting about 25% of mature trees was sufficient to remove the remainder of the juniper stand with fire. Post-fire vegetation monitoring will be performed in 2004-2006, 2008, and 2010. Seeding trials were established on both plant community types, evaluating 6 species (3 grass; Idaho fescue, Sherman big bluegrass, & Goldar bluebunch wheatgrass and 3 forbs; arrow-leaf balsamroot, Lewis flax, and western yarrow). Species are being evaluated individually and in combination at several application rates.

Technical Abstract: In the past 20 years western juniper has mainly been controlled by cutting, using chainsaws, and by prescribed fire. Cutting is commonly used to remove trees in plant communities that lack sufficient fuel to carry a fire through a stand. Woodlands that lack adequate fuel loads are those in mid to late successional stages where juniper competition has eliminated the shrub component and reduced understory production. Burning has been used in stands where sufficient shrub and understory fuels are available to carry fire through the woodland and remove the majority of trees. Burning is most successfully applied in early to mid woodland successional stages. Recently BLM districts in Alturas, California and Burns, Oregon have employed combinations of cutting and fire to remove juniper. The 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.. Study sites were set up on along the Juniper and Corral Creek drainages on South Mountain, Idaho in summer 2002. Sites are located on lands with private (Lowery property) and public (Idaho Department of Lands) ownership. Two plant community types were selected for treatment. They include western snowberry-mountain sagebrush/Idaho fescue-western needlegrass (Deep Soil Sites) and mountain big sagebrush/western needlegrass (Dry Soil Sites) communities which are representative of the main community types found between 5000 and 6500 feet. Pre-treatment measurements of understory and overstory vegetation were completed in summer 2002. All sites were dominated by post-settlement juniper woodlands (trees are < 100 yrs old). On the Dry Soil Sites juniper cover averaged 49.5%, shrub cover averaged 3.0%, and herbaceous cover averaged 9.3%. On the Deep Soil Sites juniper cover averaged 70.5%, shrub cover averaged 3.9%, and herbaceous cover averaged 10.9%. There are old trees scattered across the Dry Soil Sites with cover between1-4%. The two treatment components to the project include cutting manipulations and prescribed burning. Tree cutting manipulations were chainsaw cutting 25%, 50% and 75% of the post-settlement trees. Uncut (control) woodlands are located adjacent to cut areas. Control plots will remain as intact woodlands for comparing herbaceous and shrub response to the cutting and burning treatments. Each treatment plot was 1.2 acres in size and was replicated 5 times (40 plots total). Total area used per community type was 24 acres (48 acres in total). Juniper trees were cut in October 2002. Temporary livestock exclusion fences were built around plots in May and September 2003. Fences are 3-strand barb wire with steel posts placed every 20-25 feet. Total perimeter area of the fences are approximately 2.5 miles. Fences are scheduled to be in place through the 2005 grazing season. Prescribed fire was applied October 21-22, 2003. The objective of the prescribed fire was to kill as many remaining live trees as possible using the cut trees as a fuels base. Regardless of cutting treatment the fire application was uniformly successful at removing remaining live junipers. We estimate that on the Deep Soil sites the fire killed all remaining live trees. On the Dry Soil sites we estimate that the fire killed 85-100% of the remaining live trees. Results indicate that cutting about 25% of mature trees was sufficient to remove the rest of the stand with fire. Two control plots were lost on the Juniper Creek location (Deep Soil Site) when fire crowned through standing trees. Post-fire vegetation monitoring will be performed in 2004-2006, 2008, and 2010. Seeding trials were established on both plant community types, evaluating 6 species (3 grass - Idaho fescue, Sherman big bluegrass, & Goldar bluebunch wheatgrass; 3 forb - arrowleaf balsamroot, Lewis flax, and western yarrow). Species are being evaluated individually and in combination at several rates.

Last Modified: 9/20/2014
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