Recent growth increases in old-growth longleaf pine
Abstract
Pinus palustris tree-ring data were obtained from an old-growth stand in Thomas County, Georgia. The chronology from the pine stand is composed of a collection of cores extracted from 26 trees ranging in age from 100-400 yr. Beginning around 1950 and continuing to the present, annual increments of all age classes examined have increased, resulting in an average annual ring increment c40% greater in 1987 than in 1950. When compared with expected annual increment, the increase for 100- to 150-yr-old trees is c45%, while the increase for 200- to 400-yr-old trees is c35%. In terms of stand-level aboveground biomass accumulation, the increased growth has resulted in c5% more biomass than expected. The increased growth cannot be explained by disturbance, "stand history', or trends in precipitation, temperature, or Palmer drought severity index over the last 57 yr. Increased atmospheric CO2 is a possible explanation for initiation of the observed trend, while SOx and NOx may be augmenting continuation of this phenomenon. -from Authors