We studied the effects of elevated concentrations of carbon dioxide ([CO2]) and ozone ([O3]) on growth, biomass allocation and leaf area of field-grown O3-tolerant (Clone 4) and O3-sensitive clones (Clone 80) of European silver birch (Betula pendula Roth) trees during 1999-2001. Seven-year-old trees of Clones 4 and 80 growing outside in open-top chambers were exposed for 3 years to the following treatments: outside control (OC); chamber control (CC); 2 x ambient [CO2] (EC); 2 x ambient [O3] (EO); and 2 x ambient [CO2] + 2 x ambient [O3] (EC+EO). When the results for the two clones were analyzed together, elevated [CO2] increased tree growth and biomass, but had no effect on biomass allocation. Total leaf area increased and leaf abscission was delayed in response to elevated [CO2]. Elevated [O3] decreased dry mass of roots and branches and mean leaf size and induced earlier leaf abscission in the autumn; otherwise, the effects of elevated [O3] were small across the clones. However, there were significant interactions between elevated [CO2] and elevated [O3]. When results for the clones were analyzed separately, stem diameter, volume growth and total biomass of Clone 80 were increased by elevated [CO2] and the stimulatory effects of elevated [CO2] on stem volume growth and total leaf area increased during the 3-year study. Clone 80 was unaffected by elevated [O3]. In Clone 4, elevated [O3] decreased root and branch biomass by 38 and 29%, respectively, whereas this clone showed few responses to elevated [CO2]. Elevated [CO2] significantly increased total leaf area in Clone 80 only, which may partly explain the smaller growth responses to elevated [CO2] of Clone 4 compared with Clone 80. Although we observed responses to elevated [O3], the responses to the EC+EO and EC treatments were similar, indicating that the trees only responded to elevated [O3] under ambient [CO2] conditions, perhaps reflecting a greater quantity of carbohydrates available for detoxification and repair in elevated [CO2].

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The paper presents a general method for predicting the stem curve, volume, and merchantable height of a tree if breast height diameter (DBH) is measured, or if DBH and total height (H) as well as diameters at any heights are measured. Estimates for prediction variances are obtained both for diameters and volumes. The approach is multivariate and nonparametric. At the estimation stage, a multivariate model is developed for the total height and a fixed set of diameters: four diameters at absolute heights below breast height and eight diameters at relative distances between the breast height and the top of the tree. The expected values and variances of the dimensions and the correlations between dimensions are expressed as functions of DBH. These functions were estimated using smoothing splines. The model is applied by predicting unobserved dimensions from the observed dimensions using a linear predictor. If total height is not measured, then prediction is done using an approach based on two-point distributions. Correlation of total heights of different trees in the same stand is also modeled, and with this model, measured total heights in a stand can be used to predict unmeasured total heights. The approach provides both a detailed analysis of variation and covariation of stem curves and a practical prediction method.