A model of air-tree-soil system for ozone impact analysis

PGSM is a model of air-tree-soil system, that simulates plant growth subject to the combine influence of stress and stimulus factors from air and soil. The input parameters of tree, soil, and air allow the model to be adapted to any tree, planted at a specific location. Previously, the model was developed to simulate ponderosa pine (Pinus ponderosa L) exposed to high ozone and drought stresses in Southern California. This paper evaluates the robustness of the model by applying it to loblolly pine (Pinus taeda L.) in North Carolina. The model was first calibrated with the experimental data of loblolly pine seedlings. The simulated diameter, height, and biomass of canopy, roots and stem were comparable to measured values. The simulated photosynthetic rate was suppressed 15–30% by ozone approximately two times the concentration of ambient air. The measured suppression was 21–27%. After the calibration with seedling data, the model was extended to simulate the growth of mature trees in Duke Forest over a period of 55 years, under the estimated historic time series of meteorology and air quality. The simulated stem diameter and tree height were comparable to the observed. Hypothesis testing with the model suggested that the needle life span might be important to the sensitivity of a pine species to ozone damage.