Description

Three data-intensive studies were conducted to examine the fire history of the Kenai Peninsula on three different time scales. The Kenai Peninsula has two distinct fire regimes: a high frequency regime in black spruce (Picea mariana) and a low frequency regime in white (P. glauca) and Lutz (Picea x lutzii) spruce. A mean fire return interval (MFI) of 79 years in black spruce forests was estimated from the analysis of 189 fire scars, death dates of fire-killed trees, and age class analysis. 121 radiocarbon-dated soil charcoal samples were used to estimate an MFI of 400-600 years for extensive Lutz spruce stands over the last 2500 years, at 22 sites. Times-since-last-fire ranged from 90 to approximately 1500 years. Using dendrochronology and growth releases, it was determined that Lutz spruce forests are thinned to varying degrees by spruce bark beetles (Dendroctonus rufipennis) with an estimated mean beetle return interval of 52 years. To assess the entire post-glacial fire record, a high-resolution analysis of sedimentary charcoal was conducted for a 9-meter core from Paradox Lake in an area of mixed white and black spruce forests. Charcoal was measured at 1-cm intervals which provided a 13,000 year record of fire activity. Fire frequency was lowest during the initial shrub tundra period with an MFI of 130 years beginning 13,000 years before present (BP), increased after the arrival of birch (Betula papyrifera), willow (Salix spp.), and Populus to a MFI of 77 years at 10,700 years BP, and decreased slightly to a MFI of 81 years with the arrival of white spruce at 8500 years BP. When black spruce arrived at 4500 years BP, fire activity declined to the present MFI value of 138 years, presumably reflecting the onset of a cooler and wetter climate.