Christopher J. Crawford* - UMn Center for Dendrochronology, Department of Geography, University of Minnesota
Six open-canopy high-elevation northern red oak (Quercus rubra L.) ring-width records were evaluated along the Southern Appalachian mountain range for a common climate-driven growth signal. Ring-width records show significant correlations over the past two centuries with principal component one (PC-1) accounting for 50% of the common variance. Spectral analysis revealed that the relative variance in ring-width is concentrated at decadal timescales. Ring-width records show positive correlations (p<0.05) with prior fall - early winter and current summer mean temperature, and negative correlations (p<0.05) with prior late summer – winter total precipitation. Yet, temperature-precipitation covariance along the Southern Appalachian mountain range during winter and summer seasons undergoes a significant reversal with intervening spring and fall seasons showing weak association. As a result, ring-width-climate signal strength exhibits time-dependence over the instrumental period, although the temporal change is not statistically significant. This temporal change suggests that both temperature and precipitation can have a marked influence on ring-width variability depending on the degree of seasonal covariance. Finally, obtaining a stable interannual climate-growth calibration for these particular ring-width records remains a foremost challenge, and is a primary consequence of mixed temperature-precipitation signal strength and little power at higher frequencies.