Ecological effects of fuels treatments

Collaborators: Chuck Rhoades, RMRS; Monique Rocca and Dan Binkley, CSU

Many areas in the Rocky Mountain west are being thinned to reduce fire hazard and spread and to restore forest structure to pre-settlement conditions. Often the most economical solution for the disposal of the thinned trees is to chip or masticate them and leave the material on site. These treatments are assumed to reduce the ability of the forest to carry a crown fire, but the effects of the added material on forest ecosystems are poorly known. Such treatments do not have natural analogues, because natural disturbances, such as fire, insect outbreaks, and blowdowns, leave woody material intact to decompose. Managers and the public are interested in understanding the impacts of the addition of this woody material on forest ecosystems so that they can evaluate the potential benefits and costs of these treatments. We have a regional study (~24 sites across 4 forest types) of the ecological effects of chipping and mastication treatments that uses a common design to answer the questions raised by forest managers currently applying these treatments. Our study will determine how chipping and mastication treatments alter the distribution of woody biomass, how these changes affect the understory (production, cover, species diversity, invasive species abundance, forest regeneration), fuels and fire behavior, and ecosystem function (nutrient, carbon and water cycling); and how treatment effects differ in relation to forest type, climate, and wood size, distribution and amount. Our study will also provide information needed to develop ‘Best Management Practices’ for these treatments for southern Rocky Mountains and the Colorado plateau. We are assessing the effects of chipping and mastication using three complementary approaches. First, we compare measures of understory, fuels and fire behavior, and ecosystem function between mechanically treated sites and paired untreated controls (variables are understory production and cover, tree regeneration, chip decomposition, fuels and modeled fire behavior, soil nutrients, moisture and temperature). This evaluation will also assess if landscape variability in the distribution of added material has an important influence on vegetation or soil processes. Second, we are using small-scale manipulations of chip depth to untangle the effects of chip additions from those of thinning, and to better control for site heterogeneity by locating treatment plots adjacent to one another. Finally, we are integrating measurements made at the study sites into a process-level ecosystem model to assess how chipping and mastication treatments and the associated thinning and changes in forest structure alter site water and carbon balance. The broad geographic scope of this study and its replicated design will allow the findings of this study to provide an authoritative assessment of the effects of fuel reduction/forest restoration projects currently underway throughout the Rocky Mountain region.

Chuck Rhoades, Mike Ryan, Brett Wolk, Mike Battaglia, Monique Rocca Forest floor after mulching small diameter trees Pepe and Hydro-Axe used for mulching

Publications or Presentations Resh SC, LA Joyce and MG Ryan.  Fuel Treatments by Mulching—A Synthesis of the Ecological Impacts.  Submitted to Western Journal of Applied Forestry (June 2008). Battaglia MA, CC Rhoades, M Rocca, N Canova, B Wolk, and MG Ryan. 2008. Mulching the forest: Mastication treatment effects on surface fuels and plant cover, ESA 2008 Annual Meeting

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