Rangelands are characterized by more arid climates than forested regions; therefore, establishing fire histories using traditional methods (e.g. fire-scars from trees or charcoal in lake sediments) is problematic. This study uses radiocarbon dating of charcoal preserved in alluvial fans and stream deposits to reconstruct a record of fire and geomorphic response in rangelands of southwestern Idaho. Samples indicate three primary periods of fire-related activity: 4400 – 4000, 2000 – 1400, and 650-400 cal yr BP. Charcoal macrofossil identification and comparison with other regional climate and fire records indicate this area has likely switched between a "fuel-limited" system (fires limited by lack of fuels), and a "moisture-limited" system (fires limited by too much moisture) with changes in Holocene climate. Over the past ~2000 yr, samples from this rangeland site indicate most fires occurred during wetter times than the record average. During overall wetter periods, (e.g. LIA; 600-100 cal yr BP) tree density may have increased, and fires occurred during intervals of relative drought. During times of prolonged drought (e.g. MCA 1025-650 cal yr BP) fire was recorded during a wetter interval. After ~600 cal yr BP, fire activity is similar to the record of low intensity fires in a nearby ponderosa pine-dominated drainage, and sagebrush is common in charcoal samples. Inferred shifts in the forest-rangeland ecotone are consistent with those reported elsewhere in the Great Basin. A comparison of OSL and 14C ages shows good correspondence between charcoal ages and the charcoal containing sediments, indicating fire-related sedimentation occurs soon after fire.
Nelson, Nathan A. and Pierce, Jennifer. (2010). "Late Holocene Relationships Among Fire, Climate, and Vegetation in Rangeland Ecosystems of Southwestern Idaho". The Holocene, 20(8), 1179-1194. http://dx.doi.org/10.1177/0959683610371992