Large-Scale Climatic Influences on Baldcypress Tree Growth Across the Southeastern United States

Abstract

Baldcypress trees native to the southeastern United States are extraordinarily sensitive to growing season rainfall amounts and can live for over 1000 years. Baldcypress tree-ring chronologies have been used to develop verifiable reconstructions of March through June precipitation totals representing some 50 to 70% of the instrumentally-recorded rainfall variance. These rainfall reconstructions are dominated by high interannual variability, but also include decade-scale fluctuations representing some 10% of the reconstructed rainfall variance. Decadal variations of similar magnitude are also evident in the instrumental March-June rainfall data, and may in part reflect secular changes in large-scale climatic forcing. To explore this possibility, we performed principal components analysis on the regional network of 11 long baldcypress chronologies from the Southeast, and compared the eigenvector amplitude series derived from the first three significant principal components of tree growth with northern hemisphere 700 mb heights for spring (March-June) from 1948 to 1980. The strongest relationship discovered was between the first principal component of baldcypress growth (PC1) and spring 700 mb height departures over the southcentral United States and northern Mexico. Significant correlations with 700 mb heights over northwestern Canada and over the western North Pacific were also identified. These mid-tropospheric teleconnections with cypress PC1 are similar to the Pacific-North America (PNA) longwave circulation pattern.