Comparison of tree species sensitivity to high and low extreme hydroclimatic events

We present here a six-species comparison of tree-ring growth response to ex tremes (below the 30th and above the 70th percentile) in temperature, preci pitation, and corresponding streamflow. The species compared are Pinus edul is (PIED), Pseudotsuga menziesii (PSME), Pinus ponderosa (PIPO), Pinus flex ilis (PIFL), Pinus aristata (PIAR), and Picea engelmannii (PCEN). Sensitivi ty was determined using contingency scores obtained by comparing tree-ring growth at different lags with hydroclimatic observations from the Upper Col orado River Basin in the southwestern United States. The scores were comput ed using dual scaling methods in which the higher scores are assigned to st ronger relationships between tree-ring growth and severe hydroclimatic occu rrences. At lag 0, PIED and PSME present the greatest sensitivity to severe streamflow events. For precipitation and temperature the most sensitive sp ecies at lag 0 are PIED and PIPO. PIAR and PCEN show no significant relatio nship with extreme hydroclimatic events. PIFL shows more uniform lag-to-lag scores, suggesting a higher year-to-year persistence for this species. In general, tree-ring growth for all sensitive species is more responsive to h ot-dry than to cool-moist extreme conditions. The scoring method proposed i n this study for the analysis of tree-ring records proved to be a useful to ol for evaluating ring-width sensitivity to extreme climatic forcing.