title: Average Stand Age from Forest Inventory Plots Does Not Describe Historical Fire Regimes in Ponderosa Pine and Mixed-Conifer Forests of Western North America.
abstract: Quantifying historical fire regimes provides important information for managing contemporary forests. Historical fire frequency and severity can be estimated using several methods; each method has strengths and weaknesses and presents challenges for interpretation and verification. Recent efforts to quantify the timing of historical high-severity fire events in forests of western North America have assumed that the "stand age" variable from the US Forest Service Forest Inventory and Analysis (FIA) program reflects the timing of historical high-severity (i.e. stand-replacing) fire in ponderosa pine and mixed-conifer forests. To test this assumption, we re-analyze the dataset used in a previous analysis, and compare information from fire history records with information from co-located FIA plots. We demonstrate that 1) the FIA stand age variable does not reflect the large range of individual tree ages in the FIA plots: older trees comprised more than 10% of pre-stand age basal area in 58% of plots analyzed and more than 30% of pre-stand age basal area in 32% of plots, and 2) recruitment events are not necessarily related to high-severity fire occurrence. Because the FIA stand age variable is estimated from a sample of tree ages within the tree size class containing a plurality of canopy trees in the plot, it does not necessarily include the oldest trees, especially in uneven-aged stands. Thus, the FIA stand age variable does not indicate whether the trees in the predominant size class established in response to severe fire, or established during the absence of fire. FIA stand age was not designed to measure the time since a stand-replacing disturbance. Quantification of historical "mixed-severity" fire regimes must be explicit about the spatial scale of high-severity fire effects, which is not possible using FIA stand age data.
authors.affiliation: John Muir Institute of the Environment, University of California, Davis, CA, 95616, United States of America.
authors.forename: Jens T
authors.initials: JT
authors.lastname: Stevens
authors.affiliation: USDA Forest Service, Pacific Southwest Region, Vallejo, CA, 94592, United States of America.|Department of Environmental Science and Policy, University of California, Davis, CA, 95616, United States of America.
authors.forename: Hugh D
authors.initials: HD
authors.lastname: Safford
authors.affiliation: John Muir Institute of the Environment, University of California, Davis, CA, 95616, United States of America.|USDA Forest Service, Pacific Southwest Research Station, Davis, CA, 95616, United States of America.
authors.forename: Malcolm P
authors.initials: MP
authors.lastname: North
authors.affiliation: USDA Forest Service, Forest Inventory and Analysis Program, Pacific Northwest Research Station, Portland, OR, 97205, United States of America.
authors.forename: Jeremy S
authors.initials: JS
authors.lastname: Fried
authors.affiliation: USDA Forest Service, Forest Inventory and Analysis Program, Pacific Northwest Research Station, Corvallis, OR, 97331, United States of America.
authors.forename: Andrew N
authors.initials: AN
authors.lastname: Gray
authors.affiliation: Rocky Mountain Tree-Ring Research, Fort Collins, CO, 80526, United States of America.
authors.forename: Peter M
authors.initials: PM
authors.lastname: Brown
authors.affiliation: Biology Department, Mercyhurst University, Erie, PA, 16546, United States of America.
authors.forename: Christopher R
authors.initials: CR
authors.lastname: Dolanc
authors.affiliation: Dept. Forest Management, University of Montana, Missoula, MT, 59812, United States of America.
authors.forename: Solomon Z
authors.initials: SZ
authors.lastname: Dobrowski
authors.affiliation: School of Natural Resources and the Environment, University of Arizona, Tucson, AZ, 85721, United States of America.|Laboratory of Tree-Ring Research, University of Arizona, Tucson, AZ, 85721, United States of America.
authors.forename: Donald A
authors.initials: DA
authors.lastname: Falk
authors.affiliation: National Park Service, Pacific West Region, Fire and Aviation Management, Klamath Falls, OR, 97601, United States of America.
authors.forename: Calvin A
authors.initials: CA
authors.lastname: Farris
authors.affiliation: School of Environmental and Forest Sciences, University of Washington, Seattle, WA, 98195, United States of America.
authors.forename: Jerry F
authors.initials: JF
authors.lastname: Franklin
authors.affiliation: School of Forestry, Northern Arizona University, Flagstaff, AZ, 86011, United States of America.
authors.forename: Peter Z
authors.initials: PZ
authors.lastname: Fulé
authors.affiliation: School of Environmental and Forest Sciences, University of Washington, Seattle, WA, 98195, United States of America.
authors.forename: R Keala
authors.initials: RK
authors.lastname: Hagmann
authors.affiliation: USDA Forest Service, Pacific Southwest Research Station, Redding, CA, 96002, United States of America.
authors.forename: Eric E
authors.initials: EE
authors.lastname: Knapp
authors.affiliation: USDA Forest Service, Pacific Southwest Region, Fire and Aviation Management, McClellan, CA, 95652, United States of America.
authors.forename: Jay D
authors.initials: JD
authors.lastname: Miller
authors.affiliation: Yosemite National Park, Yosemite, CA, 95389, United States of America.
authors.forename: Douglas F
authors.initials: DF
authors.lastname: Smith
authors.affiliation: Laboratory of Tree-Ring Research, University of Arizona, Tucson, AZ, 85721, United States of America.
authors.forename: Thomas W
authors.initials: TW
authors.lastname: Swetnam
authors.affiliation: Department of Geography and Earth and Environmental Systems Institute, The Pennsylvania State University, University Park, PA, 16802, United States of America.
authors.forename: Alan H
authors.initials: AH
authors.lastname: Taylor
mesh_terms: D005390:Fires; D065928:Forests; D009656:North America; D041604:Pinus ponderosa; D064028:Tracheophyta