Application of tree-ring data from the Bear River Range, Northern Utah to reconstruct drought variability

Population centers in semi-arid northern Utah are sensitive to drought as a result of their dependence on winter precipitation for water supply. Unfortunately, relationships between precipitation and Pacific Ocean conditions such as the Pacific Decadal Oscillation and EI Nino Southern Oscillation are complex in this region and long-range forecasts are further hindered by the short length of the instrumental record relative to decadal-scale climate cycles. Tree-ring data collected from moisture sensitive sites can be used to extend precipitation and stream discharge records (Carson and Munroe, 2005; Knight et aI., 2010). However, there are no published tree-ring data from the Bear River Range of northern Utah. The goals of this research are to 1) create an up to date tree-ring master chronology using Douglas-fir from moisture sensitive sites, 2) assess the precipitation sensitivity of the chronology by comparing it to climate data, and 3) reconstruct natural flows of the Logan River. High elevation Douglas-fir were sampled from rocky, south and west facing slopes on Mt. Naomi in the Bear River Range, Utah. Tree-ring widths were measured and standardized. These standardized values were compared to, and used to update, an existing tree-ring chronology created by Woodhouse (1989). Preliminary crossdating results indicated a good correlation between the newly collected tree-ring data and the Woodhouse chronology. The combined chronologies contain sufficient sample depth to extend back 650 years before present. Preliminary results relating these tree-ring data to precipitation and stream discharge are presented