Tree-ring Growth in High-altitude Bristlecone Pine as Related to Meteorological Factors

Important climatic information may be contained in long tree-ring records from the upper treeline of mid-latitude mountains. Preliminary work and the results of related research suggest that the variation in annual ring-width series from bristlecone pine (~. aristata) at the upper treeline is related to year-to-year differences in the temperature regime, in contrast to the "drought sensitivity" of this species near the lower forest border. Therefore~ the establishment of a quantitative relationship between meteorological factors and tree-ring growth at the upper treeline may permit the extension of temperature records, and would provide an additional tool for evaluating certain environmental characteristics of remote, high-mountain regions. Direct comparison of tree-ring chronologies from 11drought-sensitive" conifers at the lo~;rer forest border with those from "cold-sensitive" trees at the nearby upper treeline might also lead to the separation of precipitation and temperature effects in paleoclimatic· reconstruction. The basic approach involves the empirical comparison of tree-ring chronologies with concurrent meteorological time series in a few areas in the western United States, selected for the proximity of a bristlecone pine treeline to one or more high altitude weather stations. A number of replicated tree-ring samples will be dated, measured, standardized, and evaluated to form the basic tree-ring chronologies. Testing the association between the ring-widths and meteorological factors will proceed through the development of progressively refined empirical models. Consistency with available biological data will serve as a general guide in the development of a meaningful model.