Predicting ozone uptake from meteorological and environmental variables

Predictions of foliar ozone uptake rates of seedling and canopy black cherry trees (Prunus serotina Ehrh.) were made using concurrent measurements of ambient ozone concentration and other environmental and meteorological data during two growing seasons in north-central Pennsylvania. The objective of the study was to determine whether ozone uptake, which in itself is difficult to measure, could be predicted from more easily-monitored meteorological variables. Ozone uptake rates were calculated from hourly measurements of local ambient ozone concentration and stomatal conductance. Hourly averages of meteorological variables included wind speed, air temperature, relative humidity, and photosynthetically active radiation. Environmental variables included leaf temperature and leaf-to-air vapor pressure deficit. Average diurnal ozone uptake was also predicted from daily averages of predawn leaf water potential and midday leaf water potential. Calculated ozone uptake was more closely correlated with stomatal conductance than ambient ozone concentrations. Air temperature was the variable most closely correlated with ozone concentration while wind speed was most closely (negatively) correlated with stomatal conductance. The best prediction of ozone uptake was obtained using wind speed and one or two other variables depending on tree size. Prediction equations were better for seedlings (r² = 0.45) than canopy trees (r² = 0.24). If ozone concentrations were included, uptake prediction increased (r²s from 0.54 to 0.64). Wind speed, relative humidity, and vapor pressure deficit were most closely correlated with stomatal conductance. Air temperature and relative humidity were most closely correlated with local ozone concentrations. Average diurnal ozone uptake was significantly related to predawn xylem water potentials, but not to midday xylem water potentials.