Final Report, Forest Restoration of Sun Creek, Crater Lake National Park
Fire frequency was measured using fire scar samples cut from sample trees. The method did not allow using composite fire intervals (combining the records of several adjacent scarred trees). In the sugar pine area, all trees located had much of the early record burned out by later fires. In the ponderosa pine area, most of the record was found on stumps cut about 50 years ago, and cross-dating would have been very difficult.
Fire frequency was conservatively estimated at 15-18 years; due to the fact that individual fire scars do not record every fire, true fire frequency is probably in the range of 10-15 years.