Fire regime on a cultural landscape: Navajo Nation

Abstract

Fire has played an important role in the evolutionary environment of global ecosystems, and Indigenous peoples have long managed natural resources in these fire‐prone environments. We worked with the Navajo Nation Forestry Department to evaluate the historical role of fire on a 50 km2 landscape bisected by a natural mountain pass. We used fifty 5‐ha circular plots to collect proxy fire history data on fire‐scarred trees, stumps, logs, and snags in a coniferous forest centered on a key mountain pass. The fire history data were categorized into three groups: All (all 50 plots), Corridor (25 plots closest to Buffalo Pass drainage), and Outer (remaining 25 plots, farther from pass). We assessed spatial and temporal patterns of fire recurrence and fire‐climate relationships. The landscape experienced frequent fires from 1644, the earliest fire date with sufficient sample depth, to 1920, after which fire occurrence was interrupted. The mean fire interval (MFI) for fire dates scarring 10% or more of the samples was 6.25 years; there were 13 large‐scale fires identified with the 25% filter with an MFI of 22.6 years. Fire regimes varied over the landscape, with an early reduction in fire occurrence after 1829, likely associated with pastoralism, in the outer uplands away from the pass. In contrast, the pass corridor had continuing fire occurrence until the early 20th century.Synthesis. Fires were synchronized with large‐scale top‐down climatic oscillations (drought and La Niña), but the spatially explicit landscape sampling design allowed us to detect bottom‐up factors of topography, livestock grazing, and human movement patterns that interacted in complex ways to influence the fire regime at fine scales. Since the early 20th century, however, fires have been completely excluded. Fuel accumulation in the absence of fire and warming climate present challenges for future management.

Diné kinship as a framework for conserving native tree species in climate change

“…We selected fire scenarios at 10-and 20-yr fire return intervals (RX10 and RX20) using the Fire and Fuels Extension to FVS (Rebain 2010, Shive et al 2014). The 10-yr interval is similar to the historical fire regime prior to the mid-19th century (Savage and Swetnam 1990, Guiterman et al 2016, Whitehair et al 2018). The 20-yr interval may be more practical for management due to funding and smokeproduction constraints.…”

“…It is important to address this risk by replicating small‐scale natural disturbances such as the historical frequent fire regime (Whitehair et al. ) by breaking up the homogenous landscape to create fuel breaks through tree thinning and fire management. Assisted migration can help prevent the extinction of a tree species, particularly ponderosa pine and Douglas‐fir.…”

“…, Whitehair et al. ). The 20‐yr interval may be more practical for management due to funding and smoke‐production constraints.…”

“…Modeling may imply that the no-management scenario would be a reasonable action to retain forest basal area and species; in real life severe wildfires, such as the nearly 6,000-ha Asaayi Lake Fire in the Din e forest in 2014, are likely to rapidly degrade native forests. It is important to address this risk by replicating small-scale natural disturbances such as the historical frequent fire regime (Whitehair et al 2018) by breaking up the homogenous landscape to create fuel breaks through tree thinning and fire management. Assisted migration can help prevent the extinction of a tree species, particularly ponderosa pine and Douglas-fir.…”

Spatiotemporal variability of fire regimes in adjacent Native American and public forests, New Mexico, USA

“…Geographical differences in fire regime were reported by Savage and Swetnam () and Whitehair et al. () on the Navajo Nation, the largest sovereign Native American nation in the United States, where landscapes differed from public lands in fire regime as early as the 1830s likely due to differences in sheep pastoralism. Apache lands in Arizona were considered examples of continued fire regimes into the 20th century (Weaver , Cooper ), and the San Carlos Apache Tribe is a national leader in applying wildland fire as a management tool (Pyne ).…”