Mastication and Prescribed Fire Influences on Tree Mortality and Predicted Fire Behavior in Ponderosa Pine

Abstract

Despite the recent surge in the use of mastication as a fuel treatment option, few studies have been conducted on potential fire behavior or fire effects associated with mastication or combined masticated/fire treatments (Stephens and Moghaddas 2005, Glitzenstein et al. 2006, Kobziar et al. 2009). Fuel models representing masticated fuel conditions for use in fire behavior modeling have not been well developed at the time of this publication (Glitzenstein et al. 2006, Kane et al. 2009, Battaglia et al. 2010). Fires in masticated fuels when soil is dry can produce heat above lethal levels for plant roots (Busse et al. 2010). An understanding of likely ecological effects should be made available to managers planning to use mastication as a fuel treatment. Mastication used in combination with prescribed burning can reduce both canopy and surface fuel loads (Stephens and Moghaddas 2005, Reiner et al. 2009). However, in young, dense plantations, such as the one in this study, managers are often concerned with whether tree mortality associated with burning residual mastication fuels outweighs the benefits of further reductions in potential fire behavior. Managers are also interested in whether pulling masticated fuel away from tree boles would decrease mortality from prescribed burning. This study should aid in decisionmaking regarding these management options. This study quantified tree mortality and compared potential wildfire behavior between treatment conditions in a young ponderosa pine (Pinus ponderosa C. Lawson) plantation in the southern Sierra Nevada in California. Tree mortality results were based on field data. Baseline tree mortality data were gathered after the mastication treatment but before the prescribed burn treatment (postmastication/preburn). Postmastication-and-fire tree mortality data were gathered for two growing seasons after the prescribed fire treatments were completed, allowing for conclusions to be drawn on the tree mortality effects of prescribed burning residual mastication fuels. Modeled results were intended to reflect potential wildfire behavior immediately posttreatment to allow land managers to weigh the risk of potentially extreme wildfire behavior against tree mortality from these types of these treatments.