The advent of modern forest land uses often coincided with the removal of indigenous people or alteration of their traditional way of life. A key consequence of modern management has been the disruption of disturbance regimes of frequent, low-severity fires in many pine forest ecosystems worldwide, contributing to problems such as severe wildfires, pathogen outbreaks, or drought-facilitated tree mortality. There is great interest in restoring the historical role of fire and learning from rare “relict” sites where fires continue. Northern Mexico contains a few isolated forests relatively unaffected by logging or fire suppression; one such site, Pino Gordo, Chihuahua, is occupied by Tarahumara, or Rarámuri as they refer to themselves, a Uto-Aztecan speaking people living in their traditional manner through agriculture, pastoralism, and management of native plants and wildlife. We reconstructed forest fire regime from fire-scarred trees, measured the structure of the forest (which has never been commercially logged), and interviewed Rarámuri community members about fire use.
Results/Conclusions Fire occurrence was consistent throughout the 19th and 20th centuries through 2004, the most uninterrupted surface fire regime reported to date in western North America. Even studies from other relict sites such as nature reserves in Mexico or the USA, while finding relatively less-disrupted fire regimes, have all shown some recent alterations associated with industrialized society. At Pino Gordo, fires recurred frequently at the three study sites, with a composite mean fire interval of 1.9 years (all fires) to 7.6 years (fires scarring 25% or more of samples). Per-sample fire intervals averaged 10-14 years. Approximately two-thirds of fires burned in the dormant season, probably the pre-monsoonal drought. Forests were relatively dense; basal area averaged 24.7 m2 ha-1 but structure varied from plots dominated by large pines (diameter > 60 cm) to plots dominated by small, young trees. Community residents reported applying fire for many purposes, most of which are consistent with previous literature on fire use (e.g., clearing brush, improving forage). Pino Gordo is an important example of a continuing frequent-fire regime in a never-harvested forest. People conserved this forest because of their emphasis on maintaining a traditional life, as opposed to logging the forest. People also facilitate the fire regime by burning. The data contribute to a better understanding of the role of humans and grazing animals in affecting pine forest fire regimes, a topic that has been controversial and difficult to assess from historical or paleoecological evidence.
