Please join us at my dissertation defense in Anderson 22 on Thursday, July 24 at 10 am.
Dissertation Title: Historical forest conditions in frequent-fire forests on the eastern slopes of the Oregon Cascade Range
Committee: Jerry Franklin (chair), Jonathan Bakker, Stevan Harrell, Thomas Hinckley, Norm Johnson, Kristiina Vogt, and Daniel Schwartz (GSR)
Abstract: Records from a 1914-25 timber inventory reveal historical variability at the landscape-level in fire-prone forests in the eastern Cascade Range in Oregon. Live conifers >15 cm dbh (diameter at breast height) were tallied by species and size class in a 20% sample of over 180,000 hectares (ha). Forests were predominantly low density relative to current conditions (roughly a third to a quarter of current mean density). Total stand density, large tree (>53 cm dbh) density, and ponderosa pine density were relatively stable across a wide moisture gradient (40-180 cm annual precipitation). Large trees, primarily large ponderosa pine and secondarily Douglas-fir, dominated total basal area (>70% of total mean basal area) and were widely distributed across the landscape (present on 97% of transects). Currently ponderosa pine and large trees no longer dominate total basal area and large trees are not as uniformly distributed across the landscape as they were historically. Higher-density values (>120 tph, 95th percentile), although rare, were widely distributed across the mixed-conifer habitat while treeless transects (no trees >15 cm dbh) were almost entirely restricted to documented burned areas at higher elevations in colder, wetter habitat types and in association with an 80,000 ha fire that burned in 1918 in ponderosa pine and lodgepole pine habitat. Historical forest conditions in frequent-fire forests may be increasingly useful in guiding contemporary forest management given 1) projections for increased drought; 2) increases in vertical and horizontal connectivity of forest canopies related to changes in land use; and 3) documented resilience and resistance of historical forest conditions to fire and drought-related stressors in fire-prone forests. This systematic sample of a large landscape provides information about variability in species composition, densities, and structures at multiple spatial scales, which are highly relevant to management activities to restore and conserve desired ecosystem functions.