Landscape trees are becoming increasingly important in urban and suburban environments as a result of the values and benefits they provide by virtue of their aesthetic nature, ability to purify ambient air, use in providing shade, and service as
Manuela Baietto and A. Dan Wilson
Tamara Wynne and Dale Devitt
, Sun et al. (2012) reported that woody species categorized as low water users from xeric habitats actually consumed almost as much water as mesic plants when grown under well-watered conditions. ET of urban landscape trees have been estimated using
Kathleen C. Ruppert and Gregory L. Davis
In his State of the Union Address (1990), President Bush proposed planting a billion trees annually for the next 10 years. Organizations such as Global ReLeaf are planning to plant 400 to 600 million trees by the year 2000. A review of science education periodicals and general information available on tree planting and care reveal little directed to children. Science education tends to focus on the nature, not the handling of trees, and where planting ideas are suggested, they tend to be about growing trees from seed. To determine the level of landscape tree care knowledge of 4th–6th graders, a questionnaire addressing how trees grow, site and tree selection, proper planting, and other areas was administered by 4-H agents and Univ. of Florida students throughout the state during five camps, involving 211 children during the summer of 1995. The questionnaire was revised with additional topics such as irrigation and mulching added and administered during three 4-H camps involving 77 4th–6th graders. Answers to these questionnaires were used to develop materials targeted for this age group and their teachers.
D.G. Levitt, J.R. Simpson, and J.L. Tipton
Although water conservation programs in the arid southwestern United States have prompted prudent landscaping practices such as planting low water use trees, there is little data on the actual water use of most species. The purpose of this study was to determine the actual water use of two common landscape tree species in Tucson, Ariz., and water use coefficients for two tree species based on the crop coefficient concept. Water use of oak (Quercus virginiana `Heritage') and mesquite (Prosopis alba `Colorado') trees in containers was measured from July to October 1991 using a precision balance. Water-use coefficients for each tree species were calculated as the ratio of measured water use per total leaf area or per projected canopy area to reference evapotranspiration obtained from a modified FAO Penman equation. After accounting for tree growth, water-use coefficients on a total leaf area basis were 0.5 and 1.0 for oak and mesquite, respectively, and on a projected canopy area basis were 1.4 and 1.6 for oaks and mesquites, respectively. These coefficients indicate that mesquites (normally considered xeric trees) use more water than oaks (normally considered mesic trees) under nonlimiting conditions.
Granier style thermal dissipation probes (TDP) have been used to estimate whole plant water loss on a variety of tree and vine species. However, studies using TDPs to investigate water loss of landscape tree species is rare. This research compared containerized tree water loss estimates of three landscape tree species using TDPs with containerized tree water loss estimates as measured by load cells. Over a three-year period, established, 5.0 cm caliper Bradford pear (Pyrus calleryana `Bradford'), English oak (Quercus robar), and sweetgum (Liquidambar styraciflua `Rotundiloba') trees in 75 L containers were placed on load cells, and water loss was measured for a 60-d period. One 3.0 cm TDP was placed into the north side of each trunk 30 cm above soil level. To reduce evaporation, container growing media was covered with plastic. Each night, plants were irrigated to soil field capacity and allowed to drain. To provide thermal insulation TDPs and tree trunks (up to 30 cm) were covered with aluminum foil coated bubble wrap. Hourly TDP water loss estimates for each species over a three-day period indicate TDP estimated water loss followed a similar trend as load cell estimated water loss. However, TDP estimates were generally less, especially during peak transpiration periods. In addition, mean, total daily water loss estimates for each species was less for TDP estimated water loss when compared to load cell estimated water loss. Although TDP estimated water loss has been verified for several plant species, these data suggest potential errors can arise when using TDPs to estimate water loss of select landscape tree species. Additional work is likely needed to confirm estimated sap flow using TDPs for many tree species.
Christina Wells, Karen Townsend, Judy Caldwell, Donald Ham, E. Thomas Smiley, and Michael Sherwood
Landscape trees are frequently planted with their root collars below grade, and it has been suggested that such deep planting predisposes trees to transplant failure and girdling root formation. The objective of the present research was to examine the effect of planting depth on the health, survival, and root development of two popular landscape trees, red maple (Acer rubrum) and `Yoshino' cherry (Prunus ×yedoensis). Trees were transplanted with their root flares at grade, 15 cm below grade or 31 cm below grade. Deep planting had a strong negative effect on the short-term survival of `Yoshino' cherries. Two years posttransplant, 50% of the 15-cm- and 31-cm-deep planted cherries had died, whereas all the control cherries had survived (P< 0.001; 2). Short-term survival of maples was not affected by planting depth. Deep-planted trees of both species exhibited little fine root regrowth into the upper soil layers during the first year after transplant. Four years posttransplant, control maples had 14% ± 19% of their trunk circumference encircled by girdling or potentially-girdling roots; this number rose to 48% ± 29% and 71% ± 21% for 15-cm- and 31-cm-deep planted maples, respectively (P< 0.01; ANOVA main effect). There were no treatment-related differences in girdling root development in the cherries.
N. E. Pellett and D. W. Elvin
Repetitive exposure to plant morphology and characteristics is necessary for students to learn to identify woody landscape plants. We developed a computer operated video program which will supplement what students learn in outdoor labs and in lecture.
The interactive video tutorial allows the computer integration of script with control of a large collection of video images that come from 35 mm slides, video images, photographs, drawings and actual plant specimens. We have tried the less expensive still video floppy technology (Kodak SV7500 Still Video Multidisk Recorder) and the Write-Once laser disc technology (Panasonic TQ-3031F Optical Disc Recorder). Both systems have advantages, but the latter offers more options at a much higher cost. Motivation for use of the program comes from self tests and the possibility to review visual examples.
Ramzy Khoury and Jimmy Tipton
Evergreen elm (Ulmus parvifolia), southern live oak (Quercus virginiana), and South American mesquite (Prosopis alba) were irrigated at 75%, 50%, and 33% of reference evapotranspiration for 2 years in Phoenix, Arizona. Each tree was irrigated with twenty-nine 3.8-L·h–1 drip emitters to a depth of 90 cm. Initial trunk diameters were about 4 cm. Water use was monitored by heat balance sap flow gauges and related to canopy volume, projected canopy area, and total leaf area. Oak used more water than elm, and elm more than mesquite under all irrigation regimes. Irrigation regimes had a greater effect on oak and elm water use than on mesquite, but all trees maintained an acceptable canopy regardless of treatment.
Ramzy Khoury and Jimmy L. Tipton
Evergreen elm (Ulmus parvifolia), southern live oak (Quercus virginiana), and South American mesquite (Prosopis alba) were irrigated at 75%, 50%, and 33% of reference evapotranspiration for 2 years in Phoenix, Ariz. Each tree was irrigated with twenty-nine 3.8-L·h–1 drip emitters to a depth of 90 cm. Initial trunk diameters were about 4 cm. Water use was monitored by heat balance sap flow gauges and related to canopy volume, projected canopy area, and total leaf area. Oak used more water than elm, and elm more than mesquite under all irrigation regimes. Irrigation regimes had a greater effect on oak and elm water use than on mesquite, but all trees maintained an acceptable canopy regardless of treatment.