Forest structure, regeneration, and fuels in unburned, once-burned and twice-burned mixed-conifer forests of the Bob Marshall Wilderness

Since the middle 1980s, managers have allowed many naturally ignited wildfires to burn with minimal interference in the Bob Marshall Wilderness, Montana, USA. This contemporary active fire regime has produced a mosaic of recent burn histories comprising various combinations of fire frequency and fire severity, the effects of which are not confounded by past management (e.g., timber harvest) or suppression. Our study area was the valley floor and lower sidewalls of the main South Fork Flathead River valley and major tributaries between 1233 and 1740 meters above sea level. We used a stratified random sampling design to ensure adequate sampling of topographic and fire severity gradients, which we hypothesized would influence post-fire fuel loads, forest structure, and tree regeneration. Included in this publication are data from 224 plots distributed among long-unburned (n = 15), once-burned (n = 89), and twice-burned (n = 120) fire histories. Woody surface fuels were sampled using the planer intercept method; herbs, graminoids and shrubs were sampled using Keane’s photoload technique; and forest structure, composition, and canopy fuels were sampled with tree measurements in concentric, fixed-area plots. Field sampling occurred during the summers of 2015, 2016, and 2017. Plot-level data include treatment type (unburned, once-burned, twice-burned), year of fire(s), fire severity (dNBR), and date of sampling, plot locations (UTM), in addition to field-measured fuels and forest structure data.
The purpose of this study was to investigate the comparative effects of single and repeat wildfires occurring between 1985 and 2013 on surface fuels, canopy fuels, forest structure, and tree regeneration, asking if wildfires function as fuel reduction treatments. We also sought to determine if and under what conditions short-interval reburns cause transitions to a putative non-forest state.
The metadata for this package was published on 02/01/2019 (data were under embargo and available via authors). On 10/17/2022 this embargo was lifted and the data became available for download.