Journal of Arboriculture 31(4): July 2005 195 Table 3. Effect of commercial parking lot planting location (landscape median and perimeter) and time of year (April and August 2002) on leaf carbon assimilation (A), stomatal conductance (gs Tree species/ /s) Parking lot location Australian bottle tree Median Perimeter Arizona ash Median Perimeter Argentine mesquite Median Perimeter Chinese elm Median Perimeter Apr 6.0z by 9.5 a 9.2 a 7.9 a 8.2 a 6.7 a 7.1 a Aug 5.7 b 6.2 a 7.4 b 11.6 a 12.2 a 5.3 a 6.5 a 8.6 b 10.9 a Apr gs (µmol/m2 /s) Ci/Ca Chl (mg/g) Aug 82.1 b 112.5 a 64.7 a 59.5 a 117.0 b 178.0 b 156.9 a 241.6 a 73.6 a 75.9 a 85.6 a 103.6 a 121.2 b 110.0 a 110.2 a 123.9 b Apr Aug 0.60 a 0.55 a 0.58 a 0.50 a 0.58 a 0.76 a 0.58 a 0.70 b 0.46 a 0.67 a 0.47 a 0.66 a 0.66 b 0.57 a 0.69 a 0.54 b Apr 5.6 a 5.1 b 4.2 b 4.6 a 3.6 b 5.4 a 3.6 b 4.2 a Aug 4.0 b 4.3 a 4.3 b 4.7 a 4.5 a 4.7 a 4.0 b 5.0 a zValues are treatment means. For gas exchange variables; n = 24. For chlorophyll concentration, n = 168, except for Argentine mesquite, n = 10. yTreatment means followed by the same letter within columns by tree species are not significantly different, Fisher’s LSD test, α = 0.05. trees in landscaped areas along the parking lot perimeter but that the magnitude of these effects was species specific. Since all trees at each parking lot site were regularly irrigated, any inhibitions of tree size and physiological function caused by parking lot median planting location was not likely due to a lack of available soil water. Specific tree responses to Phoenix parking lot microenvi- ronments may have been related to patterns of tree growth and habit. The evergreen Australian bottle tree has a largely indeterministic habit of growth in the southwest United States throughout the warmer months of the year, usually beginning in early spring. Data from Table 3 show that the physiological function of bottle trees in commercial parking lots was sensitive to the intense summer heat of Phoenix and that narrow landscaped medians further impaired physi- ological function manifested by reductions in leaf A, gs and chlorophyll concentration compared to the bottle trees in surrounding landscape perimeter areas. These photosynthetic inhibitions may have been caused in part by the relative instability of chlorophyll at high temperature (Martin et al. 1995) and/or stomatal regulation of water loss (Mott 1988) and become a likely explanation for why height and dbh of bottle trees in landscaped medians was about 30% less than for those in surrounding perimeter landscape beds. Arizona ash and Chinese elm are two winter deciduous trees with deterministic growth habits. Both tree species are commonly used as shade trees in Phoenix urban landscapes. For Arizona ash, an upland canyon riparian tree from the southwestern United States, height, dbh, and canopy diameter of trees in landscaped medians was about 30%, 42%, and 20%, respectively, less than for those in surround- ing perimeter landscaped areas. These reductions in size may have been caused in part by concomitant reductions in carbon and nitrogen assimilation as evidenced in Table 3. Reduced leaf A, gs , and chlorophyll concentrations for Arizona ash may have been caused in part by stomatal regulation of water loss, the relative instability of chloro- phyll at high temperature, and the effect of supraoptimal rhizosphere temperatures on nitrogen uptake and/or root respiration (Foster et al. 1991; Ruter and Ingram 1991; Adam et al. 2003; Celestian and Martin 2004). Of the four landscape trees studied, the size of Chinese elm was most adversely impacted by landscape median placement. Height, dbh, and canopy diameter of Chinese elm in landscaped medians were found to be about 60%, 52%, and 57%, respectively, less than for those trees in surrounding perimeter landscape beds. These reductions in Chinese elm size were accompanied by inhibitions of physiological function. Although A and chlorophyll levels of the more physiological mature leaves in August were higher than that of the relatively immature leaves in April, leaf A and chlorophyll levels of trees within the landscaped medians were significantly less than for trees within the landscaped perimeter areas (Table 3). Moreover, median trees had greater leaf gs eter trees in August. Supraoptimal root zone temperatures above 40°C (104°F) around the landscaped medians in summer (Celestian and Martin 2004) might have in part caused these inhibitions in physiological function for trees in the landscaped medians. In support of this hypothesis, previous research has shown that elevated root zone temperatures above 40°C (104°F) can inhibit leaf photosyn- thesis and conductance of Chinese elm (Martin et al. 1989). than perimeter trees in April but lower gs ©2005 International Society of Arboriculture than perim- concentrations (Ci/Ca), and leaf chlorophyll concentration (Chl) of four landscape tree species in Phoenix, Arizona. A (mol/m2 ), internal leaf to ambient CO2
July 2005
| Title Name |
Pages |
Delete |
Url |
| Empty |
Ai generated response may be inaccurate.
Search Text Block
Page #page_num
#doc_title
Hi $receivername|$receiveremail,
$sendername|$senderemail wrote these comments for you:
$message
$sendername|$senderemail would like for you to view the following digital edition.
Please click on the page below to be directed to the digital edition:
$thumbnail$pagenum
$link$pagenum
Your form submission was a success.
Downloading PDF
Generating your PDF, please wait...
This process might take longer please wait
