Effects of Fuel Management Treatments in Pinon-Juniper Vegetation at a Site on the Colorado Plateau. Final Report for Joint Fire Science Project No. 03-3-3-58
(Englisch)
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This project was designed as the first of two phases at a site on the western Colorado Plateau dominated by Utah juniper (Juniperus osteosperma) and two-needle pinon pine (Pinus edulis). Phase 1 focused on comparing the cost effectiveness of different types of thinning treatments targeting 80% of the post-settlement juniper and pinon pine trees: two chain saw treatments (cut; cut, limb, scatter) and one herbicide treatment (15% Tordon 22K applied at the base of the tree). The cut treatment was evaluated alone and when combined with seeding of the native understory grass species bottlebrush squirreltail (Elymus elymoides) at 3 pounds per acre and blue grama (Bouteloua gracilis) at 2 pounds per acre. The second phase, pending additional funding beyond the scope of the current project, will add fire as a treatment and compare fire behavior among previous thinning treatments, and vegetation response during the immediate postfire years. The results of the current study are still preliminary, but a few items can be reported at this time. The percent reduction of post-settlement juniper density varied from 68% to 92% among thinning treatments, and the reduction of post-settlement pinon pine density varied 64% to 77% among treatments. Thus, implementation of the treatments resulted in actual thinnings that varied somewhat above and below the target of 80%. The cost of each treatment also varied, but to a much greater degree: $400/acre (cut), $500/acre (cut, limb, scatter), and $70/acre (herbicide). Tree thinning resulted in significant increases in shrub density, forb cover, plant species richness, and surface fuel cover within the first 2 post-treatment years. In general, all three thinning methods produced similar results after 2 years. Results are still pending on the thinning plus seeding experiment, and they will be delivered to the JFSP at a later date. Our preliminary results indicate that similar effects on understory vegetation and fuelbed characteristics can be achieved during the first 2 post-treatment years by using any one of the three methods tested. The one exception is the coarse woody fuel load which is significantly higher in the two chain saw treatments compared to the herbicide and control treatments. These results suggest that the least expensive method (herbicide) may be preferable, at least in the short-term. However, we do not know at this time what the longer-term effects may be, and plans are in place to monitor these plots to document future changes. We also have plans for a followup study to address the objectives of phase 2 of this project.
Effects of Fuel Management Treatments in Pinon-Juniper Vegetation at a Site on the Colorado Plateau. Final Report for Joint Fire Science Project No. 03-3-3-58