Arboriculture & Urban Forestry 38(4): July 2012 and in 2004, the difference had dropped to 4% (Table 4). Some of the differences in transpiration rate may have been due to higher volumetric water content and saturated hydraulic flow (greater water availability) in the MODERATE-density soils (Table 1). As saturated hydraulic flow increased, transpiration increased (P < 0.01, R2 = 0.73) for the MODERATE-density soils (Figure 2). There was a weak linear relationship for the HIGH-density treat- ment, but, as expected, transpiration declined as nLog(Ks) de- clined (Figure 2). Kay et al. (2006) found a reduction in whole plant transpiration due to an increase in soil density and the change in water content in a clay type soil. Other research has found significant relationships between soil water content, soil 155 texture, and soil density (Kay et al. 2006; Imhoff et al. 2010). In a study exploring the effects of compaction on transpiration of an entire forest community, Komatsu et al. (2007) also found a reduction in transpiration due to an increase in pedestrian traf- fic. In 2002, there was a significantly different response (P = 0.06) between the maple species, with ‘Brandywine’ red maple transpiring 129% more per day than ‘Armstrong’ Freeman ma- ple (Table 4). In 2004, ‘Brandywine’ transpired 47% more per day than ‘Armstrong’ maple, which was significantly different at P = 0.10 (Table 4). It is unlikely that species plays much of a factor in transpiration rates (Table 3). Transpiration based on leaf area (mL·cm-2 ) was 200% greater for trees in MODERATE- Table 3. Analysis of Variance (ANOVA) results showing significance for mean daily transpiration, daily transpiration per leaf area, leaf area, leaf dry weight, stem dry weight, caliper growth, height growth, root dry weight, root volume, and root:shoot ratio for two compaction treatments, two maple species, and three years, including interactions between soil treatment, species, and year. Speciesy Water use measures Mean daily transpiration (mL) Mean daily transpiration per leaf area (mL·cm2 ) Biomass Measures Leaf area (cm2 ) Leaf dry weight (g) Stem dry weight (g) Caliper growth (cm·yr.-1 Height growth (cm·yr.-1 Root dry weight (g) Root volume (cm3 Root:shoot (ratio) ) ) ) ns ns * ns *** * *** ** * * *** ns * ns ns * *** *** * *** * *** *** *** ns ns ns ns * ns ns ns *** *** ns ns ** ns ns ns z ANOVA results indicate that asterisks (*, **, ***) represent statistical significance at P ≤ 0.05, P ≤ 0.01, P ≤ 0.001 levels; ns indicates not significant. y ns ns ns ns ns ns ns ns Species Acer × freemanii ‘Armstrong’, Armstrong Freeman maple and Acer rubrum ‘Brandywine’, Brandywine red maple; the species by soil treatment by year interac- tion is not shown as it was insignificant for all measurements. Table 4. Mean daily transpiration (mL·day-1 year by species. Year byz 2002 / Soil treatmenty MODERATE-density (n = 14) HIGH-density (n = 28) 2003 MODERATE-density (n = 10) HIGH-density (n = 20) 2004 MODERATE-density (n = 4) HIGH-density (n = 8) z Year study period was 2002, 2003, and 2004. y MODERATE = mean bulk density for three-year study of 1.64 g·cm-3 x , HIGH = mean bulk density for the three-year study of 1.77 g·cm-3 . Species were Acer × freemanii ‘Armstrong’, Armstrong Freeman maple, and Acer rubrum ‘Brandywine’, Brandywine red maple; sample sizes reflect the total number of trees available for sampling at the end of each year. At the end of 2002, 12 total trees were destructively harvested to determine stem weight and root growth. At the end of 2003, 18 total trees were destructively harvested, and at the end of the study, all remaining trees were harvested (n = 12); Means ± mean standard error followed by differ- ent letters indicate a significant difference between soil treatments at P ≤ 0.05 for each year. Differences between species were found only at P ≤ 0.10 (P = 0.06 in 2002, and P = 0.10 in 2004). ©2012 International Society of Arboriculture 56.9 ± 11.4 a 54.4 ± 8.1 a 25.0 ± 6.3 a 7.8 ± 3.2 b 66.9 ± 8.3 a 13.5 ± 6.9 b ) for interactions between main treatments of year by compaction treatment and Mean daily transpiration (mL·day-1 ) Year by / Speciesx 2002 ‘Armstrong’ (n = 21) ‘Brandywine’ (n = 21) 2003 ‘Armstrong’ (n = 15) ‘Brandywine’ (n = 15) 2004 ‘Armstrong’ (n = 6) ‘Brandywine’ (n = 6) 65.7 ± 4.5 a 44.8 ± 10.7 b 11.4 ± 6.1 a 15.6 ± 2.8 a 19.0 ± 7.4 b 43.6 ± 10.4 a ns ns *** ** *** *** ns ns ** ns ** ns Soil Analysis of Variance Resultsz Year treatment Species soil treatment Species year* Soil treatment year*
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