260 Rahman et al.: Effect of Pit Design and Soil Composistion on Performance of Street Trees Trees grown in large covered and open pits finished breaking their buds around 5–8 days earlier, between March 29 and April 5, compared to April 8–12, in the case of the trees grown in small covered pits (Table 2). Autumn color also peaked nearly two weeks later in large covered and open pits, around the third week of November versus the first week of November for small covered pits. hoc test also showed that pre-dawn leaf water potential was less negative during midsummer compared to early and late summer. Stomatal conductance of trees grown in the three types of planting pits was not significantly different for the first two measurement dates in 2010; however, the trees grown in open pits showed significantly higher stomatal conductivity through- out the measurement dates thereafter, except on May 21, 2012 (Figure 5). A two-way ANOVA showed significant dif- ferences between the planting pits [F (2, 462) = 40.316; P < 0.001], between times [F (10, 462) = 53.837; P < 0.001], and a significant interaction between the planting pits and times [F (20, 462) = 2.962; P < 0.001]. Post hoc tests showed that the stomatal conductance of trees grown in open pits was higher compared to trees grown in small and large covered pits. More- over, post hoc analysis also showed that stomatal conduc- tance was higher in late summer compared to early summer. Figure 3. LAI of Pyrus calleryana trees grown in the three pit types in 2010–2012 (n = 5). Leaf Physiology There were also significant differences in midday leaf water po- tential (Figure 4a) and pre-dawn leaf water potential (Figure 4b) of trees grown in the three different types of pits and between dif- ferent times when measurements were taken. A two-way ANOVA showed significant differences in midday leaf water potential be- tween the planting pits [F (2, 330) = 4.722; P < 0.05] and between times [F (10, 330) = 63.415; P < 0.001], but no significant interac- tion between the planting pits and time. Post hoc tests showed that midday leaf water potential of trees grown in small and large cov- ered pits were less negative compared to those grown in open pits. Post hoc tests also showed that midday leaf water potential was less negative towards the end of summer compared to early summer. Another two-way ANOVA showed significant differences in predawn leaf water potential between the planting pits [F (2, 332) = 6.008; P < 0.01], between time [F (10, 332) = 80.373; P < 0.001], and significant interaction between the planting pits and time [F (20, 332) = 10.408; P < 0.001]. Post hoc tests showed that pre-dawn leaf water potential of trees grown in open pits and small covered pits were less negative than those grown in large covered pits. Post Evapotranspirational Cooling There were large differences in evapotranspirational cooling pro- vided by the trees grown in the three different types of planting pits and also between different times when measurements were taken (Figure 6). A two-way ANOVA showed significant differ- ences in energy loss per tree between the planting pits [F (2, 462) = 60.884; P < 0.001], between times [F (10, 462) = 19.712; P < 0.001] and a significant interaction between the planting pits and time [F (20, 462) = 3.859; P < 0.001]. Post hoc analyses showed that the energy loss from trees grown in open pits was significantly higher than those grown in small and large covered pits, and energy loss from trees grown in large covered pits was higher than those grown in small covered pits. Moreover, post hoc analysis also showed that energy loss was higher during midsummer compared to the late or early summer and that the cooling ability of trees increased along with the age of the trees. Chlorophyll Fluorescence (Fv/Fm) There were also significant differences in the Fv:Fm ratio of trees grown in the three different types of planting pits and be- tween different times when measurements were taken (Fig- ure 7). A two-way ANOVA showed significant differences between the planting pits [F (2, 84) = 26.813; P < 0.001] and significant differences between times [F (6, 84) = 26.299; P < Table 2. Phenological observations on Pyrus calleryana trees grown in the three pit types. Observations were carried out between mid-March and mid-December 2011 and 2012, and between mid-September and mid-December 2010. State Small covered pit Bud break Autumn color Leaf fall Large covered pit Bud break Autumn color Leaf fall Open pit Bud break Autumn color Leaf fall ©2013 International Society of Arboriculture Started >80% ~10% ~20% ~30% Peak >15% >40% >80% Started >70% ~10% ~20% ~45% Peak >20% >50% >90% 2nd week March Started 1st week April >60% ~12% ~40% Peak >30% >80% Completed 3rd week September 3rd week October 1st week 3rd week 1st week November November December 3rd week December
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