CONSTRUCTION OF A MASTER TREE-RING CHRONOLOGY FOR THE BOISE FRONT RANGE, IDAHO

Changes in an area's wildfire regime over time may relate to climate and/or anthropogenic activity. Understanding the past and present role of fire can aid in the interpretation of historic conditions for a particular ecosystem, thus highlighting possible variables associated with any local or regional fire regime changes. A study proposed to begin over the summer of 2004 in the Boise Front Range, Idaho, would use Douglas fir (Pseudotsuga menziesii) and pondorosa pine (Pinus pondorosa) tree rings as a proxy for reconstructing fire and general climate history of the area. The master tree-ring chronology discussed in this poster was developed in anticipation of the proposed fire-history study.

Increment cores were taken from Douglas fir and pondorosa pine in the upper Crane and Dry Creek drainages in the Boise Front Range, respectively. The Eighth Street Fire burned with stand-replacing intensity in approximately 90% of the upper Crane Creek drainage and the upper portions of adjacent drainages to the north and south; the upper Dry Creek drainage has not burned in the last century (1900-present). At the upper Crane Creek site only live, unscarred trees outside of the burn perimeter were chosen for sampling.

Both study sites yielded useful data sets in the increment cores collected. Tree species were analyzed separately and compared. Ring-width sensitivity and variability were examined for each sample set. Local climate records were compared with the (currently) 100-year chronology in order to determine the extent to which climate-related variables have influenced tree-ring width. Current limitations of this chronology include the absence of any old-growth (greater than 200-year-old) trees from either sample set, and a limited number of samples representing certain time periods. Future steps in the development of this chronology include adding older trees to each sample set and comparing pre-historic ring-widths to those developed during periods with recorded climate data, as well as increasing the depth of each sample set in general.