Dendrochronological Reconstruction of Climate and Fire in a Ponderosa Pine Forest Near the Bogus Basin Area, Boise Front, Idaho
Dr. David Wilkins
In an effort to better understand past climates, fire regimes, and vegetation response to climate in the Boise Front, tree cores were collected from ponderosa pine (Pinus ponderosa) on south-facing slopes near Bogus Basin along the East Side Trail. Nineteen viable cores were collected, with at least two series dating back to 1732. Tree rings were counted and widths measured, and the data were run through the program COFECHA for cross-checking. These measured cores produced an interseries correlation of 0.523, indicating moderate similarities in their ring-width variability, and an average mean ring-width sensitivity of 0.266, indicating a moderate to high sensitivity to environmental variability. While collecting cores, fire-scarred trees were noted in the study area – partial cross-sections of several of these trees were collected using a chainsaw. Rings were counted and measured using the same procedure as with the cores, and cross-checked with the dated series from the cores. Cross-checking and examination of the scars indicates that they are from the same fire event in the 1860s. This provides the first record of a fire event prior to 1900 in the Boise Front. The tree ring measurements correspond very well (r=0.9) with the ten-year record from the Bogus Basin SNOTEL (SNOwpack TELemetry) site, which collects snowpack and related climatic data. Correlation with precipitation and other climate records, together with implications for the fire regime, will be discussed.