A PHYSIOLOGICAL APPROACH TO DENDROCLIMATIC MODELING OF OAK RADIAL GROWTH IN THE MIDWESTERN UNITED-STATES

This paper describes the development of OAKWBAL, a physiologically bas ed model that integrates daily weather data with site and species-spec ific ecophysiological data to estimate climate effects on physiology a nd radial growth of oak (Quercus) species. This model generates relati ve physiological response indices for cumulative canopy net photosynth esis and woody tissue respiration during the season of radial growth a nd the season of carbohydrate storage. These indices are entered as pr edictor variables in regression models, with detrended annual basal ar ea increment as the response variable. Separate analyses were performe d for seven similar sites located from northwest Arkansas to eastern O hio. The analyses showed that (i) individual physiological response in dices produced by the OAKWBAL model were better correlated with radial growth of black oak (Quercus velutina Lam.) and white oak (Quercus al ba L.) than were monthly climate variables; (ii) coefficients of deter mination for dendroclimatic regression models based on monthly weather variables were slightly higher than those for models based on physiol ogical indices, but the monthly weather models included an average of three more predictor variables; and (iii) dendroclimatic regression mo dels using physiological indices exhibited greater consistency across sites and were more amenable to biological interpretation than models using monthly climate variables.