Tree-Ring Evidence for Long-Term Climatic Change: Yosemite National Park

Abstract

Tree -ring data were collected from two sites within Yosemite National Park: a western juniper stand near Juniper Ridge and a lodgepole pine stand near Gaylor Lakes. Analyses of standardized and prewhitened tree-ring indices from the two sites indicate that at both sites winter (January through March) precipitation is the factor most limiting to tree growth. Using regression analysis a model predicting winter precipitation as a function of tree growth was developed and tested. The model explains 32% of the variance of the precipitation data. While the model is statistically significant, the explanatory (and hence predictive) power of the model could be enhanced by further core collection. When the model is applied to the early portion of the tree -ring record, a reconstruction of precipitation extending back to AD 1620 is obtained. Extended droughts are common in the record and include the following periods: 1650 -1648, 1700 -1720, 1749 -1758, 1807 -1824, 1842- 1851, 1885 -1893, and 1911 -1934. Further funding is being sought to expand the tree-ring data base allowing for more accurate climatic reconstruction and a longer temporal extent of the reconstruction.