Wildfire Ecology and Management at Grand Canyon, USA: Tree-Ring Applications in Forest Fire History and Modeling

Wildland fire has been a key selective force through evolutionary time, influencing the development of characteristic adaptations of forest trees ranging from the serotinous cones of lodgepole pine (Pinus contorta) to the vigorous sprouting of Canary Island pine (Pinus canariensis) (Keeley and Zedler 1998). In the semi-arid southwestern United States, forest fires play complex ecological and social roles. Ecologically, the southwestern U.S. encompass forests adapted to severe, stand-replacing fires, those adapted to frequent surface fires, and forests with a mixture of fire intensities. Overlaid on this natural mosaic, however, modern industrial society has consistently sought to suppress fire (Pyne 1982). An unintended consequence of fire exclusion, however, is the accumulation of fuel horizontally across contiguous tree canopies and vertically through the crowns of small understory trees. Coupled with warming climate, more droughts, less snow, and longer fire seasons, there is little doubt that severe fires will increase (Westerling et al. 2006). For forest ecosystems not adapted to severe burning and already stressed by non-native species, human impacts, and climate change, the likelihood of substantial irreversible degradation appears high (Savage and Mast 2005; Strom and Fulé 2007). Early proponents of taking an ecological approach to fire, such as Leopold (1924) and Weaver (1951), were lonely voices in their time. Today, however, the attention of scientists and forest managers is focused on the restoring of the naturally fire-resilient characteristics of native ecosystems (Falk 2006). In order to have a chance to accomplish this goal, it is vital that we have the best possible understanding of historical forest characteristics: fire regimes, forest structure, species composition, and dynamics.