Arboriculture & Urban Forestry 32(5): September 2006 207 face area (Table 2). Four components explained 88% of the total variation for Q. macrocarpa, whereas three components explained 86% of the variation for Q. prinus (Table 4). In both species, the growth factors and water use seedling−1 loaded positively on the first component, whereas the other water use factors loaded negatively except in Q. prinus in which water use seedling−1 loaded negatively on the first principal component. Like in experiment 2, there was little consistency between the two species in which factors loaded positively and negatively on the other principal components. Experiment 4 Evapotranspiration during the three 48 hr water use periods was 3, 9, and 5 mm (0.12, 0.36, 0.20 in) for the periods of 19 to 21, 21 to 23, and 20 to 22 July, respectively. Therefore, water use was standardized by dividing the water use statis- tics by the corresponding ET values, which generated the following water use statistics: g water use seedling−1 cm–1 ET day–1 and g water use cm−1 height cm–1 ET day–1. To sim- plify the presentation of water use data, the cm –1 ET day–1 term will be dropped. The resulting water use statistics were subjected to analysis of variance using a fixed-effects model. The authors note that although greenhouse compartments were kept as similar as possible, microclimate differences among the greenhouse compartments and differences in en- vironmental conditions among the three water use study pe- riods are confounded. We refer to a “greenhouse compart- ment effect” for convenience, recognizing that statistical dif- ferences may be the result of differences in the adjacent compartments and/or differences in environmental conditions affecting ET. For the two Q. rubra families common to all three greenhouse compartments, there were no significant family by greenhouse compartment effects for water use cm−1 height (P0.81) or water use seedling−1 (P0.06). There were two additional families (one Q. rubra and one Q. palustris) that were grown in two greenhouse compartments. For those seedlings, there were no significant greenhouse compartment effects for water use (either water use seed- ling−1 or cm−1 height, data not presented). Thus, adjusting daily water use by ET and time was an effective method of standardizing water use. For the two families common to all greenhouse compartments, there was a significant family by greenhouse compartment effect for seedling height (P 0.001); seedlings of the Q. rubra family 27 were shorter in one greenhouse compartment than in the other two (30.5 versus 51.7 and 49.8 cm [12.2 versus 20.7 and 19.9 in]). For seedlings of the other Q. rubra family (family 35), average height among the compartments was similar: 52.1, 59.1, and 49.2 cm (20.8, 23.6, and 19.7 in, SE Å 4.6 cm [1.8 in]). Thus, height and ET-adjusted water use data from all the half-sib families were combined over greenhouse compartments and analyzed by species using the one-way analysis of variance (ANOVA) procedure within SPSS using a completely ran- dom design with single plant replications in a fixed-effects model. A two-way ANOVA (species by family) was not pos- sible because of the low number of Q. macrocarpa and Q. palustris families. There were no significant differences between species in seedling height. Average seedling height for Q. macrocarpa, Q. palustris, and Q. rubra were 36.5, 49.9, and 46.9 cm (14.6, 20, 18.8 in Table 5). There were significant differences in the water use characteristics (g water seedling−1 and cm height–1) among the species (P 0.001, and 0.001, respectively). Water use seedling−1 for Q. macrocarpa, Q. palustris, and Q. rubra was 391.3, 562.6, and 466.4 g (13.7, 19.7, 16.3 oz), respectively (Table 5) and water use cm−1 height was 12.7, 12.6, and 12.2 g (0.445, 0.441, 0.427 oz in–1 height), respec- tively (Table 5). Within all three species, there were signifi- Table 4. Principal component matrixes for Quercus macrocarpa and Q. prinus seedlings in experiment 3. Component Q. macrocarpa Variable Height Leaf area Root area Dry weight shoot Root Total plant Water use seedling−1 cm−1 cm−2 cm−2 height leaf area root area Shoot-to-root ratio Cumulative percent of total variation explained 0.87 0.40 0.57 0.01 0.46 0.54 −0.84 −0.82 −0.19 0.43 37.7 0.13 0.30 −0.20 −0.54 −0.89 −0.75 0.64 0.26 0.08 0.54 0.45 62.9 −0.26 −0.17 −0.71 0.52 −0.13 −0.17 0.46 0.31 −0.01 0.17 0.21 −0.40 0.59 88.3 −0.01 −0.42 −0.09 0.03 0.09 0.65 0.47 78.4 −0.36 0.12 0.14 0.26 0.80 0.74 0.67 0.79 Q. prinus 1234123 0.90 0.91 0.83 −0.07 0.39 −0.37 −0.65 −0.78 −0.69 0.40 37.6 −0.26 0.06 0.88 −0.08 0.01 0.64 0.70 68.6 −0.26 −0.31 −0.26 0.50 0.56 0.60 0.13 0.55 0.55 0.23 0.24 85.8 ©2006 International Society of Arboriculture
September 2006
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