The history and influence of fires was studied at the forest-grassland ecotone in high valleys of southwestern Montana. Investigations were focused upon several sites having early landscape photographs and modern retakes that allow for detection of vegetational changes. Fire intervals were determined for these sites by analyzing fire scars on trees. Prior to 1910, mean fire intervals at Pseudotsuga forest-grassland ecotones were 35 to 40 years, and probably shorter in grassland proper. No fires were detected on the study areas after 1918. Photographic comparisons and field inspections show a substantial increase in mountain big sagebrush (Artemisia tridentata subsp. vaseyana) and conifers since 1900.
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Arno et al. (1983) studied this question.
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