Description

More than 5.4 million acres (2.2 million hectares) of Alaska tundra have burned over the past 60 years (Figure 2), indicating its flammable nature under warm, dry weather conditions. Tundra fires have important impacts on vegetation composition (Racine et al. 1987, 2004), permafrost dynamics, nutrient and carbon cycling (Wookey et al. 2009), and wildlife populations (Jandt et al. 2008, Joly et al. 2010). Despite the impacts of tundra burning, relatively little is known about natural variability in fire occurrence and links to climate and vegetation change. This lack of knowledge hinders land-management and resource-planning efforts. Increasing evidence suggests that Arctic environmental change is affecting tundra fire regimes. In 2010 for example, 37 fires burned more than 106,696 acres (43,180 ha) in Noatak National Preserve (Figures 1, 2b), the largest number of fires occurring in this area since record keeping began in 1950. Three years prior, the Anaktuvuk River Fire on Alaska's North Slope more than doubled the total area burned north of 68 degrees N in Alaska since 1950 (Figure 2) (Hu et al. 2010, Jones et al. 2009). This event, associated with record-high temperatures and record-low precipitation and sea-ice extent, marked the first time this area burned in at least 5,000 years (Hu et al. 2010). Changes in fuel characteristics associated with increased shrub density over the past several decades (e.g., Tape et al. 2006) may also be changing tundra flammability. Paleoecological evidence from ?ancient? shrub tundra in and around Gates of the Arctic National Park and Preserve (Figure 2) indicates the high flammability of birch shrubs that dominated this region circa 13,000-11,000 calendar years before present (cal. yr BP) (Higuera et al. 2008). In combination with studies documenting increased birch abundances in recently-burned areas (e.g., Joly et al. 2010), these patterns raise the possibility of positive feedbacks between increased shrub density and increased tundra burning. We investigated fire history of the past 6,000 years in the Noatak National Preserve, with the goal of understanding how fire regimes varied in relation to climate and vegetation. This work places modern tundra fire occurrence in the context of natural variability, provides critical fire-history information for fire managers, and elucidates drivers of tundra fire regimes with relevance to past, present and future tundra ecosystems.