physiological approach to dendroclimatic modeling of oak radial growth in the midwestern United States

This paper describes the development of OAKWBAL, a physiologically based model that integrates daily weather data with site and species-specific ecophysiological data to estimate climate effects on physiology and radial growth of oak (Quercus) species. This model generates relative physiological response indices for cumulative canopy net photosynthesis and woody tissue respiration during the season of radial growth and the season of carbohydrate storage. These indices are entered as predictor variables in regression models, with detrended annual basal area increment as the response variable. Separate analyses were performed for seven similar sites located from northwest Arkansas to eastern Ohio. The analyses showed that (i) individual physiological response indices produced by the OAKWBAL model were better correlated with radial growth of black oak (Quercus velutina Lam.) and white oak (Quercus alba L.) than were monthly climate variables; (ii) coefficients of determination for dendroclimatic regression models based on monthly weather variables were slightly higher than those for models based on physiological indices, but the monthly weather models included an average of three more predictor variables; and (iii) dendroclimatic regression models using physiological indices exhibited greater consistency across sites and were more amenable to biological interpretation than models using monthly climate variables.