Pacific Southwest Research Station

Silvicultural Prescriptions to Restore Forest Health

Full title: Silvicultural prescriptions to restore forest health

Lead Researchers: Patricia N. Manley and Malcolm North, US Forest Service, Pacific Southwest Research Station; Dennis D. Murphy and T. Will Richardson, University of Nevada

Abstract

Many uncertainties exist in the effects and effectiveness of fuel treatment prescriptions being planned in the Lake Tahoe basin on various forest health objectives. In the basin, forest health objectives include restoring a greater proportion of the landscape to old forest conditions, restoring forest composition (e.g., greater predominance of Jeffrey pine), structure (e.g., more open forest structure and multi-aged forests), conserving and restoring biological diversity, and reducing the risk of catastrophic wildfire. The lack of information combined with the urgency to act is potentially forming a perfect storm in the Lake Tahoe basin, where extensive treatments are planned over a short period of time (5-10 years), thereby creating the opportunity for significant unforeseen negative ecological consequences. Fuel treatments are typically designed to reduce crown bulk density and canopy contagion, resulting in the remaining trees having a fairly regular spacing. Historical records indicate that forests with an active fire regime had clustered tree spacing with gaps and heterogeneous understory plant cover. This study will design and test a silvicultural prescription that leaves a clustered distribution of trees that more closely mimics historical distributions while also reducing fuels to determine the benefits gained in ecological restoration and the sacrifices made in altering fire behavior. It will also test the relative effects of the two prominent slash treatments: pile and burn and mastication. We will examine the interaction of two overstory (regular canopy tree spacing [fire emphasis] and clustered tree retention [restoration emphasis]) and two understory (mastication and pile and burn) treatments and a control on measures of forest function (vegetation, soil properties, truffles), biological diversity (birds, small mammals, ants, invertebrates), and habitat and prey for key wildlife species of special concern (Northern Goshawk [Accipiter gentilis], California Spotted Owl [Strix occidentalis], and American marten [Martes americana]). A factorial design will be used to test overstory and understory treatment effects on forest functions, biological diversity and select prey species. Sampling will use a Before-After-Control-Impact (BACI) design, with clustered treatment (n = 4) and control (n = 1) sites. The cluster of five sites will be implemented within a similar set of environmental conditions, and then replicated in at least 4 different locations, for a total of 20 sample sites.