NOAA/WDS Paleoclimatology - Heyerdahl fire data from Potholes, central Oregon - IMPD USPOT002

STUDY NOTES: This site was sampled as part of a project to reconstruct historical fire regimes in central Oregon. Ring-boundary fire scars were assigned to the preceding calendar year. Several metadata files are provided with the FHX file. -999 in any file indicates no data. Ring-boundary fire scars were assigned to the preceding calendar year. Several metadata files are provided with the FHX file. -999 in any file indicates no data. Four supplemental information files are located at URL - http://www.ncei.noaa.gov/pub/data/paleo/firehistory/firescar/northamerica/supplemental/ : (1) uspot002-plot-data.csv provides information on the plots. (2) uspot002-saplings.csv provides information on small trees that we did not attempt to remove wood samples from. These trees were tallied in each plot by species and diameter class (measured at breast height, 1.4 m) in 5.6-m radius plots. Diameter classes: 2.5 (0-5 cm), 7.5 (5-10 cm), 15 (10-20 cm). (3) uspot002-scarred-tree-info.csv provides information on fire-scarred trees, including ones we also sampled for recruitment date. (4) uspot002-undatable-trees.csv provides information on trees from which it did not appear that we could obtain intact wood samples.
ABSTRACT SUPPLIED BY ORIGINATOR: In parts of central Oregon, coarse-textured pumice substrates limit forest composition to low-density lodgepole pine (Pinus contorta Douglas ex Loudon var. latifolia Engelm. ex S. Watson) with scattered ponderosa pine (Pinus ponderosa Lawson & C. Lawson) and a shrub understory dominated by antelope bitterbrush (Purshia tridentata (Pursh) DC.). We reconstructed the historical fire regime from tree rings and simulated fire behavior over 783 hectares of this forest type. For centuries (1650-1900), extensive mixed-severity fires occurred every 26 to 82 years, creating a multi-aged forest and shrub mosaic. Simulation modeling suggests that the historical mix of surface and passive crown fire were primarily driven by shrub biomass and wind speed. However, a century of fire exclusion has reduced the potential for the high-severity patches of fire that were common historically, likely by reducing bitterbrush cover, the primary ladder fuel. This reduced shrub cover is likely to persist until fire or insects create new canopy gaps. Crown fire potential may increase even with current fuel loadings if the climate predicted for mid-century lowers fuel moistures, but only under rare extreme winds. This study expands our emerging understanding of complexity in the disturbance dynamics of lodgepole pine across its broad North American range.