A Dendroecological Assessment of Whitebark Pine in the Sawtooth Salmon River Region Idaho

Whitebark pine (Pinus albicaulis Engelm.) tree-ring chronologies of 700 to greater than 1,000 years in length were developed for four sites in the Sawtooth-Salmon River region, central Idaho. These ring-width chronologies are used to (1) assess the dendrochronological characteristics of this species, (2) detect annual mortality dates of whitebark pine attributed to a widespread mountain pine beetle (Dendroctonus ponderosae Hopk.) epidemic during the 1909 to 1940 period, and (3) establish the response of whitebark pine tree ring-width growth to climate variables. Crossdating of whitebark pine tree-ring width patterns was verified. Ring-width indices had low mean sensitivity (0.123-0.174) typical of high elevation conifers in western North America, and variable first order autocorrelation (0.206-0.551). Mortality of dominant whitebark pine caused by mountain pine beetle had a maxima at 1930 on all four sites. Response functions and correlation analyses with state divisional weather records indicate that above average radial growth is positively correlated with winter and spring precipitation and inversely correlated with April temperature. These correlations appear to be a response to seasonal snowpack. Whitebark pine is a promising species for dendroclimatic studies.