116 Table 3. Water use of three Quercus species over three days under greenhouse conditions. Species Q. cerris Q. robur z y Height (cm) 45.3Ay Q. pubescens 46.0A 70.5B seedling-1 47.5A 44.9A 73.4B Average daily water use (g day -1 leaf area (cm-2) 0.091A 0.111B 0.084A 1.4B 1.3A 1.3A Height-adjusted water use was calculated by dividing the average daily water use by seedling height. Means within a column followed by different letters are significantly different from each other at the α = 0.05 level using the Student-Neuman-Kuels test. Each value is the mean of 72 plants. Table 4. Water use of two sources from three Quercus species over three days under greenhouse conditions. Average dailywater use (g day-1) leaf area Height- adjusted Species Q. cerris Source Sellano 54.2 Cy Amiata 36.3AB Q. pubescens Bazzano 62.2D Cerreta Q. robur z y Pineta 29.7A 67.1D Cascine 73.9E Height (cm) seedling-1 58.9B 36.0A 57.2B 32.6A 72.1C 74.7C ( cm-2 ) 0.087B 0.094C 0.104D 0.118E 0.098CD 0.070A (cm-1 1.4B )z 1.3AB 1.2A 1.5BC 1.4B 1.2A Height-adjusted water use was calculated by dividing the average daily water use by seedling height. Means within a column followed by different letters are significantly different from each other at the α = 0.05 level using the Student-Neuman-Kuels test. Each value is the mean of 36 plants. ment through sexual or asexual methods. For instance, tall seed- lings with either high or low height-adjusted water use could be identified within each seed source. Undetermined is whether the differences in an individual seedling’s height-adjusted water use are related to adaptive features such as drought resistance, that would confer increased fitness to the urban forest environment. Growth For the two Q. cerris sources, three components in a principal com- ponent analysis that used 20 variables, extracted 79% and 74% (sources 1 and 2, respectively) of the total variation. Three compo- nents extracted 80% and 77% (sources 5 and 6) and 83% and 79% (sources 7 and 8) of the total variation for Q. pubescens and Q. robur sources, respectively. In the first component, factors associated with aboveground growth and dry weight (height, leaf number and area, total shoot dry weight, and shoot-root dry weight ratio) were highly correlated (> 0.80) and loaded positively on the first principal com- ponent axis, while root system associated factors (percent of root dry weight and percent coarse root dry weight) and water use cm-2 leaf surface area, loaded negatively. In the second component, root- associated variables such as total, fine, and coarse root dry weight loaded positively while shoot factors as shoot-to-root dry weight ra- tio and percent shoot dry loaded negatively. In the third component, percent leaf area and leaf area-to-fine root dry weight ratio loaded positively while percent fine root and total shoot dry weight loaded negatively. Plotting total shoot length, total plant dry weight, and leaf area-to-fine root dry weight on the first, second, and third compo- nent axes, respectively, showed that sources 5, 6, 7, and 8 (Q. pubes- ©2009 International Society of Arboriculture ) Height-adjusted (cm-1)z Struve et al.: Relative Growth and Water Use from Seedlings Figure 2. Water use per seedlings plotted against seedling height for two sources from each of three Quercus species. cens and Q. robur) clustered together while the two Q. cerris sources were separated from each other and the other species (Figure 3). Quercus robur seedlings had greater leaf number and leaf area, greater leaf, stem and total plant dry weights and a larger shoot- to-root dry weight ratio than Q. cerris and Q. pubescens seedlings (Table 5). Quercus robur seedlings had similar coarse and total root dry weights as Q. pubescens seedlings, which was lower than that for Q. cerris seedlings. Quercus robur seedlings had greater specific leaf area than Q. pubescens seedlings, but lower than Q. cerris seedlings. As with the seedling height and water use data,
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