A Model to Account for Potential Correlations between Growth of Loblolly Pine and Changing Ambient Carbon Dioxide Concentrations

Abstract

Continuously increasing concentrations of atmospheric carbon dioxide (CO2) may be leading to enhanced growth rates for loblolly pine. In order to plan effectively silvicultural regimes and harvesting schedules, managers of loblolly pine plantations may wish to account for these potential changes when making growth and yield projections. Data from 94 unthinned plots across the Southeast were used to develop an equation that utilizes change in ambient CO2 concentration and initial site quality to predict change in site index (ΔSI). For a given change in CO2 concentration, a greater increase in site index is afforded to lower quality sites. The ΔSI equation was incorporated into a loblolly pine growth model. Simulations with and without site index adjustments were performed and plot volume estimates were compared to observed values. Mean percent residual dropped from 9.7% with no adjustment to -0.5% when ΔSI was employed. Forest managers can use this model to evaluate how possible CO 2-induced growth increases may affect long-term Timber yields and management strategies.