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Urban sprawl of the greater Phoenix metropolitan area is rapidly replacing agricultural and non-irrigated desert vegetation with an irrigated urban forest comprised of a mixture of woody ornamental plant materials. Our objective was to estimate and compare the carbon acquisition potential (CAP) of residential landscape plants to the dominate plant species found in adjacent agricultural and desert sites. Maximum shoot and leaf gas exchange measurements were made at monthly intervals for one year (Aug. 1998 to July 1999) using a portable photo-synthesis system. Concurrent diel gas exchange measurements were made seasonally. Gas exchange measurements were made on alfalfa at agricultural sites, blue palo verde, creosote bush and bur sage at desert sites, and on a mixture of 19 different woody ornamental tree, shrub and ground cover species at residential sites. A trapezoidal integration model was used to estimate daily CAP at each site based on maximum assimilation flux values and seasonally adjusted diel assimilation patterns. Annual landscape CAP was then calculated as the summation of estimates of daily CAP. Calculated annual CAP was highest at agricultural sites (159.0 mol/m2 per year), lowest at desert sites (35.3 mol/m2 per year), and intermediate at residential landscape sites (99.3 mol/m2 per year).

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As forests, agricultural fields, and suburban and urban lands are replaced with impervious surfaces resulting from development, the necessity to recover green space is becoming increasingly critical to maintain environmental quality. Vegetated or green roofs are one potential remedy for this problem. Establishing plant material on rooftops provides numerous ecological and economic benefits, including stormwater management, energy conservation, mitigation of the urban heat island effect, and increased longevity of roofing membranes, as well as providing a more aesthetically pleasing environment in which to work and live. Furthermore, the construction and maintenance of green roofs provide business opportunities for nurseries, landscape contractors, irrigation specialists, and other green industry members while addressing the issues of environmental stewardship. This paper is a review of current knowledge regarding the benefits of green roofs, plant selection and culture, and barriers to their acceptance in the United States. Because of building weight restrictions and costs, shallow-substrate extensive roofs are much more common than deeper intensive roofs. Therefore, the focus of this review is primarily on extensive green roofs.

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Mulches applied to landscape surfaces can moderate soil temperatures by changing the surface heat energy balance and conserve soil water by reducing evaporation rates. In the Southwest, decomposing granite is commonly used as landscape mulch. However, organic mulches, such as pine residue mulch and shredded tree trimmings, are becoming more available as industry by-products. Recent impetus toward water conservation and recycling forest and urban tree waste into urban landscapes has increased the need to better understand how such mulch types effect the temperature, moisture. and light quality of drip-irrigated landscapes typically found in the Southwest. We compared effects of three mulches, two organic (composted ponderosa pine residue and shredded urban tree trimmings) and one inorganic (Red Mountain Coral decomposing granite), turf grass, and bare soil applied to 14 drip-irrigated landscape research plots on below-ground soil temperatures at depths of 5 cm and 30 cm, temperatures at the mulch-soil interface, mulch surface temperatures, diel mulch surface net radiation, and albedo. Below-ground soil temperatures were more buffered by organic mulches, and mulch-soil interface temperatures were lower under organic mulch than inorganic mulches. Inorganic mulch daytime surface temperatures were lower than organic mulch surface temperatures. Nighttime net radiation values were less negative over organic mulches than inorganic mulches and albedo was significantly higher for the inorganic mulch and bare soil treatments. These results provide evidence to show that organic surface mulches have higher resistances to heat transfer than inorganic mulches, which could improve landscape plant water and nutrient use efficiencies by lowering high summer root zone temperatures.

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The frequency of tropical cyclones is a major factor affecting the vegetation of the Mariana Islands, where these storms are called typhoons. An average of about one typhoon per year has passed within ≈100 km of Guam during the past 50 years. The physiognomy of Guam's natural and urban forests is largely determined by these typhoons. The impact of each typhoon is determined by a long list of interacting factors such as species characteristics; environmental and horticultural conditions preceding the typhoon; the intensity, direction, and duration of winds; the amount of rainfall associated with the typhoon; and the environmental and horticultural conditions following the disturbance. Many species survive typhoons by reducing aerodynamic drag of the canopy by abscising inexpensive leaves or breakage of small stems which results in an intact major structural framework. Speed of recovery for nonlethal damage following disturbance depends on nonlimiting conditions during recovery. Thus, the most destructive typhoons are those that occur in sequence with other environmental stresses. The most common of these may be heat and high-light stress, associated with subsequent high pressure systems, and severe drought conditions. For example, the 230–298 km·h–1 winds of Typhoon Paka in Dec. 1997 were followed by the driest year on record for Guam. Typhoon debris and drought generated 1400 forest and grassland fires from Jan. through May 1998. Sequential typhoons are also severely damaging. For example, Guam experienced three direct eye passages and two more typhoons within 113 km during the months Aug. to Nov. 1992. Damage susceptibility and recovery dynamics will be discussed in relation to these and other physical, chemical, biological, and human-induced factors.

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native prairies, agricultural lands, and forests is discussed. Similarly, the inputs and retention of nitrogen in urban ecosystems are contrasted with rural environments and related to the carbon cycles in different systems. Chapter 6 covers the storage

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Hurricanes strike the Gulf Coast of the United States every few years. We briefly describe generalized hurricane tracks for the Gulf Coast and vegetation damage using NDVI satellite imagery as well as slides of damaged urban trees in Florida. The impact of recent hurricanes on both pecan defoliation and production and on initial damage and subsequent recovery of various ornamental trees is described. Pecan harvests were greatly reduced by hurricanes that struck late in the season in both Alabama and Texas. Varieties of pecans varied in their susceptibility to various stresses. Pine forests were sometimes devastated by certain hurricanes while live oaks, various shrubs, and important insects often survived the same storms with little damage. Many exotic ornamental plants including Chinese tallow are either adventive or invasive along the Gulf Coast. Species escape from cultivation over a long period of time and exhibit different invasion lag phases. In Texas and Louisiana, hurricane damage to native trees allowed Chinese tallow seedlings and saplings to subsequently dominate some areas as a result of the disturbance. One delayed ecological response to hurricanes and typhoons is an acceleration of ongoing exotic plant invasions.

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Flowering dogwood (Cornus florida L.) is an important tree of forests and urban landscapes in the eastern United States. Currently, there are over 100 cultivars of flowering dogwood commercially available. An identification process based on genotype would be of use to researchers, breeders, and nurserymen, as many cultivars are similar phenotypically. Molecular markers offer a promising way of definitively identifying flowering dogwood cultivars. Amplified fragment length polymorphism (AFLP) is a technique that can be used to generate DNA fingerprints. DNA was isolated from leaves of 17 common cultivars of dogwood and AFLP fingerprints were generated by a Beckman Coulter CEQ™ 8000. Fingerprints were converted to binary data and verified manually. Two drafts of a cultivar identification key were generated based on the corrected, verified binary data and cultivar-specific peaks. Six primer combinations were used to construct all keys and were tested with seven unknown dogwood cultivar samples. Six unknown samples were correctly identified using the keys. Only one unknown, `Cherokee Brave', was unidentifiable with any key. In all cases, some intracultivar variation was observed. A similarity index was calculated and visualized with a tree of genetic relatedness using NTSYSpc. Intracultivar variation was observed in the similarity index as well. This database for cultivar-specific molecular markers will serve as a starting point to which other cultivars can be added and also can be used in breeding applications, patent application and other projects, such as mapping the C. florida genome.

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Economic and aesthetic losses from deer browsing of ornamental plants in nurseries and landscapes has increased significantly during recent years. This, according to wildlife specialists, is primarily due to hunting restrictions in urban areas. There are numerous so-called “deer repellents” on the market, but most are foliar applied and can be washed off or diluted with rain or irrigation. This study evaluated the effect of a systemically absorbed deer repellent tablet, Repellex (trademarked product), on deer browsing of containerized ornamental plants. A foliar applied counterpart, Repellex liquid, was also evaluated. The 1.5-gm tablets are a 14–2–2 fertilizer containing denatonium benzoate, lactose, ammonium phosphate, hydrous magnesium, and potassium sulfide. Two to eight tablets, depending on the size of the container, are placed adjacent to the root ball of the plant and 2 inches below the media surface at time of transplant. Gumpo azalea, Indian hawthorne, daylily, and Manhattan Euonymus were used for the study. Plants treated with tablets were held 6 to 8 weeks, according to manufacturer recommendations, under nursery conditions, then transported to deer-holding pens at the Whitehall Forest Research Station at the Univ. of Georgia. The pens, 1/2- to 1 acre in size, contained seven to 12 deer, depending on the study. Growth measurements initially and at weekly intervals were used to assess the degree of deer browsing. Results varied by plant species. Generally, the tablets were ineffective in preventing deer browsing when compared to the control. The foliar applied liquid was effective in reducing deer for up to 6 weeks when compared to the control. Plants treated with a tablet at time of propagation and two additional tablets when transplanted were browsed to the container within 2 days of deer exposure.

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In 1992, Hurricane Andrew destroyed over 1000 mature trees in the City of North Miami, located 50 mi north of the storm center. The cleanup cost over $1,000.000. Most of the tree failures were caused by structural faults: co-dominant leaders, narrow limb attachment, included bark, over-lifting, hatracking, poor vertical limb placement, crown imbalance, overly-dense crowns, crossing and in-growing branches. All could have been corrected with proper pruning. Action was taken to reduce future damage. The city arborist made a complete, computerized inventory of all trees on public property, creating a data-base with all structural problems identified. These were prioritized so the worst could be addressed first. After any pruning work was done on a city tree, a follow-up evaluation was made, and any additional pruning needed was scheduled. Pruning followed the recommendations of state specialists and three county extension agents with the University of Florida Cooperative Extension Service. City workers were taught using lectures, demonstrations, site visits, CES publications, and individualized instruction. In addition, all new trees purchased were grades FL Fancy or FL no. 1, based on Grades and Standards for Nursery Plants; such trees require little or no corrective pruning at planting and mature as structurally-sound trees which resist wind damage. Two later storms (1993, 1999) produced winds in North Miami similar to those of Hurricane Andrew. Together they destroyed only 35 trees which cost $35,000 to remove. These data demonstrate that following CES pruning recommendations reduces storm damage to trees, saving money and preserving the urban forest canopy.

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children’s urban agriculture activities surveyed in this study—is to conduct regular urban agriculture activities in outdoor spaces (e.g., vacant lots, gardens, forests, rooftops) at school, where it is easy for teachers to access the children, as well as

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