Sapwood Area as an Estimator of Leaf Area and Foliar Weight in Cherrybark Oak and Green Ash

The relationships between foliar weight/leaf area and four stem dimensions (dbh, total stem cross-sectional area, total sapwood area, and current sapwood area at breast height) were investigated in two important bottomland tree species of the southern United States, cherrybark oak (Quercus falcata var. pagodifolia EN.) and green ash (fraxinus pennsylvanica Marsh.). In all models tested and for both species, total sapwood area was consistently more highly correlated with foliar weight and leaf area than were the other three measures. However, there was little difference in accuracy among simple linear, multiple, and nonlinear models that used total sapwood area to predict either foliar weight or leaf area. Accuracy was improved slightly through the addition of total height and live crown ratio to the linear model. Foliar weight of both species was best described as a function of total sapwood area and live crown ratio (3 = 0.97, n = 16 for both species). Leaf area of cherrybark oak was best described as a function of total sapwood area, total height, and live crown ratio (?= 0.96, n = 16), whereas leaf area of green ash was best described as a nonlinear function of total sapwood area (? = 0.95, n = 16). In contrast with other studies on upland oaks in relatively cool climates, we found that current sapwood area was only a fair estimator of foliar weight and leaf area in cherrybark oak and was a poor estimator in green ash. These results lead to the speculation that more of the sapwood than just the most recent one or two growth rings may be active in water conduction in bottomland species in warm climates. Specific leaf area was highest in the lower crowns of trees of both species and was highest among trees of the lower crown classes. Although based on a limited sample size of four trees per crown class per species, we found that the vertical distribution of foliage within the crown differed among crown classes in both species. Most of the foliage on dominant and codominant trees of both species was concentrated in the upper one-third of the crown, with only a very small proportion of the foliage in the lower one-third of the crown. Intermediate and overtopped cherrybark oaks and intermediate green ash trees had a more even distribution of foliage throughout their crowns, while the foliage of overtopped green ash trees was highly concentrated in the lower onethird of the crown. The leaf area:sapwood area ratio did not differ significantly among crown classes in either species, but averaged 0.67 m2 cm-* in cherrybark oak and 0.24 m* crne2 in green ash. FOR. SCI. 48(1):69-76.