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Community involvement is critical for the continued vitality of the urban forest. To encourage this involvement, an understanding is needed of what promotes shared stewardship as well as of different cultural perspectives regarding trees. A survey of the general public in 109 large metropolitan areas across the continental U.S., a culturally and ethnically diverse group, was conducted. Two thousand adults were surveyed to assess the extent of their childhood experiences with nature, their current attitudes toward urban forests, and their demographic backgrounds. Respondents were questioned particularly about their earliest experiences with nature and their current understanding and appreciation of the urban forest. Other researchers have examined the relationship between childhood contact with nature and attitudes toward nature among professionals in environmental fields, but this relationship has not been explored in the general public. Correlations between survey respondents' memories of childhood contact with nature, their current perceptions of the urban forest, and the influence of their cultural and ethnic backgrounds will be presented. For example, respondents who reported very easy access to nature as children were likely to agree strongly that trees should be planted in business districts to reduce smog. Results from this survey may be applied in programs to teach children about trees and gardening, thus better tailoring these programs to engender future appreciation for the urban forest. Raw data from this survey will be made available to other researchers.

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Heightened awareness of ecological concerns have prompted many municipalities to promote water conservation through landscape design. In central Arizona, urban residential landscapes containing desert-adapted plant species are termed xeriscapes, while those containing temperate or tropical species and turf are termed mesoscapes. Research was conducted to ascertain landscape plant species diversity, tree, shrub, and ground cover frequency; landscape canopy area coverage; and monthly irrigation application volumes for xeric and mesic urban residential landscapes. The residential urban landscapes were located in Tempe and Phoenix, Ariz., and all were installed initially between 1985 and 1995. Although species composition of xeric and mesic landscapes was generally dissimilar, both landscape types had comparable species diversity. Mesoscapes had significantly more trees and shrubs and about 2.3 times more canopy area coverage per landscaped area than xeriscapes. Monthly irrigation application volumes per landscaped surface area were higher for xeriscapes. Even though human preference for xeric landscape plants may be ecological in principle, use of desert-adapted species in central Arizona urban residential landscape settings might not result in less landscape water use compared with mesic landscapes.

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Shade acclimation response of Emerald Queen Norway maple street trees to variable urban irradiance levels was investigated. Specific leaf area, trunk growth, and crown density were measured from trees in 13 sites ranging from urban canyons in the business core to open exposures in residential areas of Seattle, Wash. Percentage of potential seasonal input of global shortwave radiation for each site was modeled based on the azimuth and elevation angles of the surrounding horizon topography. Building height in the business core reduced estimated irradiance to a range of 27% to 90% of that for an unobstructed horizon topography, while those outside the business core had 90% to 95% irradiance. As estimated potential irradiance decreased, growth of these maple street trees exhibited responses characteristic of shade acclimation in a dose-response pattern. Specific leaf area increased and trunk growth and crown density decreased to acclimated levels at -70% of potential irradiance. These acclimation responses did not degrade the function of the trees in their urban-canyon locations. Their foliage was healthy, and reduced crown density was not apparent since there were no full-sun-grown trees for comparison.

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More than 70 biogenic hydrocarbon (BHC) compounds are known to be emitted by plants, but only a few are emitted in relatively large quantities. The magnitude of BHC emissions from individual trees is affected by ambient light and temperature, species-specific emissions rates, and leafmass. Like other volatile organic compounds (VOC), BHC emissions react with oxides of nitrogen (NOx) to form ozone and, thus, can contribute to urban air pollution. On average, BHC emissions are as reactive or more reactive than the VOC emissions from automobiles and can have higher ozone-forming potential. An accurate estimate of the overall magnitude of BHC contributions is important in formulating strategies to reduce peak ozone concentrations because an effective strategy will take into account the relative strengths of NOx and VOC emissions. The choice between NOx and VOC controls is crucial since an incorrect emphasis may result in non-attainment of ozone-reduction goals and control measures for either NOx or VOC involve enormous costs. As part of a program to develop a reliable BHC emission inventory for the Central Valley of California, a quantitative investigation of the leafmass of urban trees was conducted. Twenty-one trees in Bakersfield, Calif., were harvested and leaves removed, dried, and weighed. Leaf masses per tree ranged from 1.5 to 89.6 kg. Leaf mass densities (dry leaf mass per area of crown projection) ranged from 150 to 3200 g·m-2, as much as eight times greater than leaf mass densities for deciduous forests and more than twice those for coniferous forests. These data suggest the BHC contributions of urban trees may be underestimated if their foliar masses are calculated using forest-based leaf mass density data.

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Abstract

Two jicama (Pachyrrhizus erosus Urban) or yam bean cultivars were grown for 0, 30, or 65 days of natural daylength prior to placement under short days (9-hour natural light, 0800 to 1700 hours) and long days (short day plus 87 watts/m2 incandescent light, from 2200 to 0200 hours). After 10 weeks, fleshy root growth was more rapid and extensive under short days for both cultivars in all pretreatment exposures. After 20 weeks, the relative differences in root dry weight were greater for 0- and 30-day pretreatment and in ‘Cristalina’ than in ‘Agua Dulce’.

Open Access

The effects of incorporation of compost to a disturbed urban soil on turfgrass establishment, growth, and rust severity were assessed in a replicated field study. A blend of two locally available composted biosolids (sewage sludge) was incorporated into a nutrient-deficient subsoil at a rate of 130 m3·ha-1, adding NO3-N, P, and K at 126, 546, and 182 kg·ha-1, respectively, to each compost-amended plot. Kentucky bluegrass (Poa pratensis L.), perennial ryegrass (Lolium perenne L.), and a mixture of these two species were seeded into both compost-amended and nonamended plots and observed for 1 year. Turfgrass establishment estimated from visual assessments of percentage cover and growth measured by clipping yields were significantly (P < 0.05) enhanced by the incorporation of the composted biosolids. These effects were first observed and most pronounced on plots seeded with perennial ryegrass and were apparent for the duration of the study. The severity of leaf rust caused by Puccinia sp. was significantly (P < 0.05) less on perennial ryegrass seeded on the compost-amended plots. This study demonstrates the feasibility and potential benefits of amending disturbed urban soils with composted biosolids to enhance turfgrass establishment and is the first report of the suppression of a foliar turfgrass disease through the incorporation of compost into soil.

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Dairy manure compost (DMC) may be an effective soil amendment when establishing new urban landscapes. The objective of this study was to evaluate the bioavailability of DMC nutrients to typical urban landscape plants. In March 2003, DMC rates of 0, 9, 18, and 27 kg/m2 (0, 1.25, 2.5, 5 cm) were incorporated into the top 10 to 15 cm of Austin silty clay soil. Half of each 6 x 6-m plot was established with bermudagrass sod and the other half with six types of ornamental plants consisting of annual, perennial, and woody species. During the third 2005 growing season, plant tissue was harvested from selected landscape plants to measure biomass production and nutrient uptake. Plant growth and nutrient contents were compared to plant available soil nutrients that were measured during fall 2004 and 2005. Plant available P in the upper 7.5 cm of soil ranged from 89 to 170 mg/kg in September 2004 and from 31.3 to 105.5 mg/kg in August 2004. Potassium and trace elements (Fe, Cu, and Zn) were also increased in the upper 7.5 cm by DMC applications. Increased concentrations of plant available soil nutrients in DMC-amended plots were correlated to overall increases in plant growth and nutrient uptake. Bermuda grass exhibited increased growth and increased tissue concentrations of N, P, K, and Zn. Penta biomass and nutrient uptake were also increased by DMC applications. Lantana stem weights significantly increased with DMC application rate up to 18 kg/m2, but no additional increases were obtained with the 27 kg/m2 rate. Results of this study show that, after three growing seasons with no additional fertilization, a 1- to 2-cm application of dairy manure compost is sufficient to provide continued fertility to landscape plants.

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Bedding plant growers have the opportunity to utilize urban waste compost in their growing media, but variation in substrates that constitute the compost could influence the efficacy of growth regulator drenches. This experiment investigated the effect of 0%, 30%, 60%, and 100% compost made from biosolids and yard trimmings on the efficacy of a paclobutrazol drench on Impatiens wallerana Hook.f. `Accent Red'. Paclobutrazol was applied at a.i. drench rates of 0, 0.016, 0.032, 0.060, or 0.125 mg/pot. Growth of control plants (0 mg) increased linearly as the percentage of compost in the medium increased from 0% to 100%. Growth of plants in all media decreased as paclobutrazol concentration increased to ≈ 0.016 mg with no further decreases at higher concentrations. The efficacy of paclobutrazol varied with the medium. For example, paclobutrazol at 0.016 mg reduced shoot dry mass by 31 % relative to control plants in the presence of 100% compost but only 17% in the absence of compost. The percentage of growth reduction, relative to control plants, increased as the percentage of compost in the medium increased. Chemical name used: β-[(4-chloro-phenyl)methyl]-α(1,1-dimethylethyl)-1H-1,2,4-triazole-1-ethanol (paclobutrazol).

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Urban areas are typically 2 to 3°C warmer than surrounding rural areas throughout the year. Winter minimum temperatures are often 4 to 5 °C warmer in the city and, during extreme episodes may exhibit differences of 12 to 13°C. Because the USDA Hardiness Maps compile readings from individual stations in an area, temperature differences may not be apparent at the local scale. This study was conducted to compare ornamental plant damage during Winter 1995–96 in Fort Worth, Texas. AVHRR 1-km thermal satellite imagery was used to determine the warmest and coolest portions in Fort Worth, Texas. Each temperature area was divided into five 0.5-km blocks on the basis of similar landscape features and plant types. During Mar. 1996, these areas were evaluated on the basis of plant damage to several species. Asian jasmine (Trachelospermum asiaticum), indian hawthorn (Raphiolepis indica), St. augustine turf (Stenotaphrum secundatum), southern magnolia (Magnolia grandiflora), and Live Oak (Quercus virginiana) were the primary species damaged. Asian jasmine and St. Augustine turf were either completely killed or severely damaged in the coldest areas but suffered only moderate or light damage in the warmest areas. Indian hawthorn, live oak, and southern magnolia suffered leaf and stem damage in the coldest areas but little to no damage in the warmer areas.

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Abstract

Airborne pollen concentrations (grains/m3) within and near trees of 2 cultivars of Olea europaea L. were studied during the 30-day pollination period at 2 urban sites in Tucson, Ariz. ‘Manzanillo’, the dominant horticultural cultivar, was compared to the fruitless ‘Swan Hill’. Air sampling using a Burkard trap was undertaken from 2 Apr. until 1 May 1985; during this period, 95% of the 1985 Olea pollen was airborne. Peak atmospheric Olea pollen concentrations at both sites occurred on 14 Apr. 1985. Pollen concentrations around the ‘Manzanillo’ site ranged from 7 grains/m3 to 6196 grains/m3 per day. At the ‘Swan Hill’ site, daily totals were an order of magnitude less, from 5 to 309 grains/m3 per day. Hourly pollen concentrations for the ‘Manzanillo’ site on the peak day varied from 1000 to 18,133 grains/m3 per hr. Hourly values at the ‘Swan Hill’ site on the peak day varied from 7 to 896 grains/m3 per hr. Both sites exhibited rapidly increasing pollen concentrations at sunrise with a sharp increase for the ‘Manzanillo’ site between 1100 to 1300 hr. Both cultivars produced about 85,000 pollen grains per anther. An unknown anatomical or physiological factor in ‘Swan Hill’ inhibits stomial rupture, resulting in 85% inhibition of anther dehiscence and pollen-shedding.

Open Access