Effects of Substrate on Dendrochronologic Streamflow Reconstruction: Paria River, Utah; With Fractal Applications to Dendrochronology

Two piñon ( Pinus edulus ) tree-ring chronologies developed on each of three substrates (sandstone, shale, and alluvial fan deposits) in southern Utah for the period 1702 to 1997 demonstrate that geologic substrate affects dendrochronologic streamflow reconstructions. Chronologies from alluvial fan deposits explain the most variance of cool-season (October 1 to May 31) flow with an adjusted coefficient of determination (R a 2 ) equal to 0.59. Chronologies from sandstone deposits account for 52 percent of the variance, while those on shale deposits account for 45 percent. The highest single-site annual discharge reconstruction (October 1 to September 30), R a 2 = 0.25, is provided by chronologies from shale deposits. The highest substrate-pair annual discharge reconstruction, R a 2 = 0.27, is provided by chronologies from alluvial fan deposits. The highest summer discharge reconstruction (July 4 to September 3), R a 2 = 0.14, is provided by chronologies from sandstone. The different substrate response is attributed to varying amounts of clay in each substrate affecting infiltration and available water for tree growth. The fractal parameters (fractal dimension and Hurst exponent), calculated using the roughness-length method, describe the long-term persistence of each tree-ring series and of the hydrologic record. The fractal dimensions range from 1.739 to 1.939 for the tree-ring series for the calibration period, and from 1.884 to 1.946 for the entire chronology periods. The fractal dimension for the annual hydrologic record is 1.802, and 1.819 from October 1 through May 31. Modification of each tree-ring series based on the ratios of the Hurst exponent of each series forced the fractal dimensions of the tree-ring series to be closer to that of the hydrologic series. (Abstract shortened by UMI.)