A natural resource condition assessment for Sequoia and Kings Canyon National Parks: Appendix 21 – altered fire regimes

Battles, John; Moody, Tadashi; Saah, David

A suite of abiotic and biotic stressors poses risks to the ecological integrity of Sequoia-Kings Canyon National Parks (SEKI, Exline et al. 2009). Foremost among these is the alteration of temporal and spatial characteristics of fires, or the fire regime. Disruption of fire regime in Sequoia-Kings Canyon National Parks since 1860 has created the potential for large, uncharacteristically severe fires in forests where such catastrophic events happened rarely, if ever, in the past (Caprio and Graber 2000). Because the Sierra Nevada encompasses such wide latitudinal and elevational ranges, its ecological communities vary dramatically. Grasslands and woodlands occur in the foothills; conifer forests dominate the midslopes; and alpine barrens cover the mountain peaks. However, in virtually all zones where burnable vegetation is present, fire plays an important role (Skinner and Chang 1996). Various reconstruction methods such as sediment records, pollen and macrofossils, and tree fire scar records on the long-lived giant sequoia (Sequoiadendron giganteum) and other species indicate that fire has been present for millennia in the Sierra Nevada (Sugihara et al. 2006). Evidence of Native American use of fire for cultural purposes dates back nearly 9,000 years (Anderson and Moratto 1996). Settlement in the Sierra Nevada in the mid-19th century by European Americans started the shift in the natural fire regimes. However the policy of comprehensive fire exclusion applied throughout the first half of the 20th century has caused widespread changes in Sierra Nevada vegetation (Gruell 2001). The impact of this policy on the fire regime for particular vegetation types is evident in many lines of fire history evidence. Lower- and middle-elevation montane forests are of particular concern. Here, the lack of periodic low- and mixed-intensity fires has led to an increase in tree density, a buildup of forest fuels, and a more continuous fuel supply (Sugihara et al. 2006, Collins et al. 2011). As a result, many of these forests are at risk today of large, uncharacteristically severe wildfires that may impose long-term damage to these ecosystems (Miller et al. 2009). Current research also suggests that some of the observed trends in fire frequency, timing and severity may be tied to ongoing shifts in the climate (Westerling et al. 2006). Managers and scientists from Sequoia-Kings Canyon (SEKI) and Yosemite National Parks were among the first public land managers to recognize the dangers caused by comprehensive fire exclusion and suppression. In 1968, the US National Park Service adopted a policy that included fire management as an approach to ―preserve natural conditions‖ as stipulated in the 1964 Wilderness Act (Stephens and Ruth 2005). As a result, programs were started in these parks in the late 1960’s and early 1970’s that not only incorporated management ignited prescribed fire, but also allowed fires in certain designated regions to burn, in order to achieve management goals such as fuels reduction and ecosystem process restoration (Caprio and Graber 2000, Collins and Stephens 2007). A joint federal program in the late 1990’s defined these management fires as ―Wildland Fire Use for Resource Benefit‖ (WFU fires), but adoption of these principles and techniques outside of the National Parks has been slow to take hold. For example, in the National Forests, the emphasis has been on mechanical fuel treatments as a way to restore ecosystem structure and protect resources, guided by such planning processes as the National Cohesive Wildland Fire Management Strategy (Forest and Rangelands 2011) and the Sierra Nevada Forest Plan Amendment (SNFPA 2004). Both management fires and mechanical fuel treatments face serious obstacles, as land managers in the Sierra Nevada attempt to use them as tools to treat millions of at-risk acres (Sugihara et al. 2006, Keeley et al. 2009).

A natural resource condition assessment for Sequoia and Kings Canyon National Parks: Appendix 21 – altered fire regimes

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