摘要：Understanding natural variability in precipitation and drought, and the resulting effects on Sierra Nevada forests, is crucial for successful resource management in this environmentally sensitive area of California. This study assessed the species-specific influence of precipitation variations on radial growth, recruitment, and mortality patterns for three conifer species ( Pinus jeffreyi , Juniperus occidentalis , and Pinus contorta ) in two mid-elevation lake catchments over the past 550 years. The P. jeffreyi chronology was the most highly correlated with winter precipitation patterns, although the other two species also exhibited significant correlations. Ring-width patterns suggest the influence of the Pacific Decadal Oscillation (PDO) and El Niño–Southern Oscillation (ENSO) on winter precipitation over the length of the records. Recruitment patterns displayed significant, though directionally distinct, correlations with winter drought: P. contorta exhibited increased recruitment during extended drought periods, while P. jeffreyi and J. occidentalis showed increased recruitment during wetter intervals. Finally, a ring of dead trees around both lakes is evidence of a late 20th century water level rise, likely caused by earlier snowmelt and/or wetter conditions. Moisture availability has exerted a strong influence on Sierra Nevada forests through time, but the strength of tree-growth response, and even the sign of tree population response, has been species-specific.
