Effects of Climate on Growth of Shortleaf Pine ( Pinus echinata Mill.) in Northern Georgia: A Dendroclimatic Study

Abstract

Recent applications of dendroecological techniques in the southeastern United States have focused upon the analysis of forest health to assess the rate, timing, and magnitude of changes in recent (<30 years) growth rates of southern pine species. However, knowledge of the pine growth/climate relationship is necessary before such assessments can be made. We developed a tree-ring index chronology from shortleaf pine growing in north-central Georgia and investigated the pine/growth relationship using correlation and response function analyses and multiple regression techniques. We found that shortleaf pine have a significant positive response to above-normal precipitation and a significant negative response to above-normal temperature during the current growing season, especially from May to July. We also found a strong time-dependent response by shortleaf pine to climate during the period studied (1910-1986). A regression model using certain monthly climatic variables as predictors explained 46% of the variability in the index chronology. However, climate variables do not adequately model growth beginning in 1963 as the residuals from the climate/growth model show increased variability over the previous periods. This change in pine growth rates since 1963 must therefore be due to nonclimatic factors.