Municipal Tree Research Articles

Callery Pear Cultivars Tested As Street Trees: Final Report on a 12-year Study

Cooperators in the Municipal Tree Restoration Program planted nine Callery pear (Pyrus calleryana Decne.) cultivars in 11 Pennsylvania, U.S. communities for evaluation as street trees, comparing two cultivars (three in one case) in each community. Cooperators measured them annually with standardized methods for 3 years and then at 3-year intervals until the 12th year. The most noteworthy differences occurred in tree height and crown width. The tallest were Aristocrat™, ‘Cleveland Select’, and ‘Redspire’, attaining more than 8 m (26 ft) on average by the twelfth year and even 10.3 m (34 ft) in one community. ‘Autumn Blaze’, evaluated only at one location, was ≈1.5 to 2 m (5 to 6.6 ft) shorter in the 12th year. Heights of the other cultivars, tested at just one or two locations, were similar to the tallest ones. Crown widths differed more in the first 9 years than at the twelfth when on average most were ≈6.5 m (21.5 ft) wide. Cleveland Pride ®, ‘Cleveland Select’, Valiant ®, and ‘Whitehouse’ were narrower than the others until the ninth year, but only ‘Cleveland Select’ at ≈5.6 m (18.5 ft) remained narrower in the twelfth year and not everywhere. All cultivars were in good health during the whole period, although the foliage of ‘Whitehouse’ exhibited minor injuries in many years. As street trees, the Callery pears were not invasive and did not yet experience branch breakage, which can become a serious problem. All of the cultivars are too tall to be planted under utility wires.

Restoration of the urban forests of Tokyo and Hiroshima following World War II

The urban forests of Tokyo and Hiroshima were devastated by American bombing during World War II. Approximately 160 km 2 of Tokyo were burned by more than 100 fire bombings, while an area of 12 km 2 was leveled and burned by one atomic bomb in Hiroshima. Tokyo's street tree population was reduced from 105,000 to approximately 42,000 by the end of the war. In the years immediately following the war, the street tree population dropped to 35,000 in Tokyo due to a combination of further tree mortality and the cutting of trees for fire wood. No estimates of pre-war street tree populations are available for Hiroshima. Examination of pre- and post-atomic bombing photographs of Hiroshima suggests an even higher percentage of the trees in the city were destroyed. Post-war reconstruction of the urban forests of each city developed along different pathways. Plans for the redevelopment of Tokyo were rejected by the general public who wanted a return to pre-war conditions. Few streets were widened to accommodate traffic and allow for new street tree planting. Plans for new parks were shelved or only partially achieved. Some streets were replanted by private citizens. Initial survival rates of replanting were low. Trees in Tokyo's municipal tree nurseries, which had not been converted to vegetable gardens during the war, were often larger than the optimal size for transplanting, but were used as no other trees were available. A more concerted effort to reconstruct the urban forest came following the 1959 decision to site the 1964 Olympic Games in Tokyo. Many streets were widened and planted with trees. New tree-lined boulevards were also created. In contrast, Hiroshima sponsored an international competition for the design of a Peace Park and a major tree-lined boulevard. Several wide streets were built with space for street trees. Major plans were also drawn to create greenways along the rivers and to build additional parks. Trees were initially donated by local farmers and nearby towns for planting the parks and the boulevard since municipal tree nurseries had been converted to vegetable gardens during the war. Survival rates were very low due to the rubble content of the soil and difficulties in watering the transplanted trees. Strong support from the mayors of Hiroshima contributed to the success of urban forest reconstruction in Hiroshima. The historical significance of the destruction caused by the first atomic bomb to be dropped on an urban area also contributed to Hiroshima citizens' will to reconstruct both the city and its urban forest. Species and location of trees determined the survival of trees after war in both cities. Species with strong resprouting ability and thick bark survived the bombing and fire. In Tokyo trees located in open areas avoided the fire, while in Hiroshima trees standing behind tall concrete buildings were shielded from radiation and the heat wave. In addition to the difficulties faced during the city-wide replanning process, constraints of urban forest recovery included severe financial restriction, short supply of proper large-sized trees for planting and lack of labor for planting and post-planting tree care. Hiroshima used public participation and community involvement to restore the urban greenery successfully and, until today, has maintained a program to conserve the trees that survived the atomic bomb.

Designing and Implementing Utility Line Arboreta

In the United States, a significant conflict exists between overhead utility lines and inappropriately tall trees planted in or near line easements. A major goal of Virginia, U.S.’s Municipal Tree Restoration Project is the establishment of utility line arboreta in multiple state locations as a way to evaluate, showcase, and promote trees compatible with overhead utility lines. Three different utility line arboreta models have been developed that can be replicated anywhere internationally to deal with this important infrastructure conflict. A stepwise list of considerations and potential funding sources for developing utility line arboreta is provided, as well as a comparison of the advantages and disadvantages of the three described utility line arboreta models.

A Practical Approach to Assessing Structure, Function, and Value of Street Tree Populations in Small Communities

This study demonstrates an approach to quantify the structure, benefits, and costs of street tree populations in resource-limited communities without tree inventories. Using the city of Davis, California, U.S., as a model, existing data on the benefits and costs of municipal trees were applied to the results of a sample inventory of the city's public and private street trees. Results indicate that Davis maintained nearly 24,000 public street trees that provided $1.2 million in net annual environmental and property value benefits, with a benefit­cost ratio of 3.8:1. The city can improve long-term stability of this resource by managing maintenance, new plantings, and stand rejuvenation on a city zone basis.

Influences of Community Characteristics on Municipal Tree Ordinances in Illinois, U.S.

While the overall objective of municipal tree ordinances is to provide safe and attractive community forests, the approach to addressing this issue varies profoundly among municipalities. This study explores the relationship between community characteristics and municipal tree ordinances using data from 151 Illinois communities. Results show significant correlations between ordinance provisions and comrnunity 'characteristics relating to wealth and education. Communities with higher mean income and level of education are more likely to have provisions biased toward the maintenance and protection of existing community trees, while communities where residents are less educated and poorer on average tend to have ordinances focused on community aesthetics and safety through resource improvement. Municipal governments, and the tree care professionals advising them, can use this information for guidance when revising or developing ordinances to match community preferences and objectives.

Equations for Predicting Diameter, Height, Crown Width, and Leaf Area of San Joaquin Valley Street Trees

Although the modeling of energy-use reduction, air pollution uptake, rainfall interception, and microclimate modification associated with urban trees depends on data relating diameter at breast height (dbh), crown height, crown diameter, and leaf area to tree age or dbh, scant information is available for common municipal tree species. In this study, tree height, crown width, crown height, dbh, and leaf area were measured for 12 common street tree species in the San Joaquin Valley city of Modesto, California, U.S. The randomly sampled trees were planted from 2 to 89 years ago. Using age or dbh as explanatory variables, parameters such as dbh, tree height, crown width, crown height, and leaf area responses were modeled using two equations. There was strong correlation (adjusted R2 > 0.70) for total height, crown diameter, and leaf area with dbh. Correlations for dbh with age and crown height for several species were weaker. The equations for predicting tree sizes and leaf area are presented and applied to compare size and growth for all species 15 and 30 years after planting. Tree height, crown diameter, and dbh growth rates tended to slow during the second 15 years, but the leaf area growth rate increased for most species. Comparisons of predicted sizes for three species common to Modesto and Santa Monica trees suggest that pruning has a significant impact on tree size and leaf area, potentially more than climate and soil characteristics.

Replacement of Trees Under Utility Wires Impacts Attitudes and Community Tree Programs

Opinions of people in 54 Pennsylvania municipalities who received trees through the Municipal Tree Restoration Program (MTRP) were surveyed, and progress in their tree programs also was evaluated. All municipal tree program components, such as ordinances, tree commissions, inventories, and management plans, were stimulated by the MTRP to varying extents in one or more ways in 91% of the municipalities. Responses from residents showed high approval for removal of large trees that interfered with utility wires, though some did miss them, and for replacement with smaller-growing cultivars of Amelanchier, Crataegus, Malm, Pyrus, and Syringa. Responses across all genera indicated that 82% liked the planted trees, 77% thought they improved the neighborhood, and 69% favored removal of the large trees when they were replaced by smaller trees. Only 8% greatly regretted the removals and 3% offered negative comments about the removal of large trees or replacement with smaller species. Comments about likes and dislikes were mainly about tree characteristics and varied among genera. The most common complaints were about messy fruit, and the best-liked qualities were flowers and other aesthetic traits. There was little variation in attitudes among communities, three of which differed from the others in their opinions about Malus cultivars, which seemed to relate mainly to the nature of the trees and their fruit.

Callery Pear Cultivars Tested as Street Trees: Second Report

Nine Callery pear (Pyrus calleryana) cultivars were planted under utility wires in 11 communities for evaluation as street trees. In most communities, 2 cultivars were alternated within each of several plots. Cooperators in the Municipal Tree Restoration Program used standardized methods to measure them annually at the end of the growing period for 3 years, and periodically afterwards until the ninth year in some cases. Significant differences were found in growth rate, height, crown width, and trunk diameter, but growth patterns and dimensions of most cultivars that were evaluated for 9 years were similar, with some notable exceptions. The height growth of 'Autumn Blaze' seems to have stalled at 5.6 m (18.5 ft) 9 years after transplanting, whereas most other cultivars exceeded 7.2 m (23.7 ft) and were still growing about 0.4 m (1.3 ft) per year. 'Cleveland Select' and 'Whitehouse' had narrower crowns and smaller trunks than others. All cultivars were in very good health except 'Whitehouse', whose foliage and twigs were injured somewhat in most years by unidentified insects and disease, possibly anthracnose or fireblight.

Crabapple Cultivars Tested as Street Trees: Second Report

Seventeen crabapple (Malus) cultivars planted under utility wires in 27 communities were evaluated as street trees. In most communities, 2 cultivars were alternated within each of several plots. Cooperators in the Municipal Tree Restoration Program used standardized methods to measure them annually at the end of the growing period for 3 years and periodically afterwards until the ninth year in some cases. Many differences were found in growth rate, height, crown width, and trunk diameter. Most cultivars had healthy foliage, though some injuries were caused by apple scab and several insects. Basal sprouts were common, and low branching of broader cultivars also required periodic pruning especially in confined spaces. Centurion®, Harvest Gold®, Red Jewel®, 'Spring Snow', and Sugar Tyme® are recommended as street trees based on the most extensive data. 'Adams', 'Donald Wyman', 'Prairifire', 'Red Barron', and zumi 'Calocarpa' also appear promising.

Tree Wardens and Utility Arborists: A Management Team Working for Street Trees in Massachusetts

Public trees along streets and roads are often jointly managed by municipalities and electric companies. This research obtained information about community forestry programs and assessed the level of cooperation between the two management entities. The study queried electric utility staff arborists and municipal tree wardens, the arboricultural professionals in Massachusetts who are directly responsible for the planting, maintenance, and removal of street trees in urban and community forests. Results showed that the majority of communities still lack street tree inventories and management plans. Major advances in utility arboriculture have resulted in the need for trained and qualified arboricultural professionals to implement the new practices and techniques. Municipal arboriculture professionals give high ratings to the cooperation between communities and electric utilities when the private companies employ trained arborists on staff.

Serviceberry Cultivars Tested as Street Trees: Initial Results

Five serviceberry {Amelanchier) cultivars, 2 each in 11 communities, were planted for evaluation as street trees. They were measured annually for 3 years, and periodically afterwards, by cooperators in the Municipal Tree Restoration Program using standardized methods. 'Autumn Brilliance', 'Cumulus', 'Princess Diana', 'Robin Hill', and Tradition® all performed well in general, but they suffered somewhat from urban stresses. 'Autumn Brilliance' had healthier foliage, higher survival, and was broader but not as tall as the others.

Tree Lilac Cultivars Tested as Street Trees: Initial Results

Three Japanese tree lilac (Syringa reticulata) cultivars, 2 each in 11 communities, were planted for evaluation as street trees. Cooperators in the Municipal Tree Restoration Program using standardized methods measured them annually for 3 years, and periodically afterwards. 'Ivory Silk', 'Regent', and 'Summer Snow' performed well at all locations. All 3 cultivars grew slowly initially, and their foliage tended to turn yellow in late summer. Height growth of 'Summer Snow', reputed to be slower than 'Ivory Silk', was not slower at all locations.

From Nature to Nurture: The History of Sacramento's Urban Forest

Over the course of 150 years, a combination of cultural and natural processes drove Sacramento's transition from City of the Plains to the City of Trees. This paper describes how the many authors of Sacramento's treescape have affected the health, management, and public perception of the city's trees. Local government directed early street and park tree plantings and banned problem tree species by ordinance. During the first half of the 20th century, participation in street tree planting and preservation by groups such as the Chamber of Commerce, Boy Scouts, Science Teachers Association, and "tree enthusiasts" raised public awareness and civic pride. The large trees shading city streets became a community icon, frequently described as the "crowning jewel of Sacramento." More recently, concern about street tree health associated with declining funds for municipal tree care has spawned new partnerships that involve trained volunteers in Dutch elm disease control, residents in energy-conserving yard tree planting, and a public task force in developing policy recommendations to perpetuate Sacramento's legacy as the City of Trees.

A Street Tree Inventory for Massachusetts Using a Geographic Information System

The creation of a street tree inventory using Geographic Information System (GIS) software can greatly enhance municipal tree management. Many different techniques were explored in an effort to map tree locations efficiently and accurately, including aerial photo interpretation, Global Positioning Systems (GPS), surveying techniques, and tree placement on existing base maps. Additionally, several different types of basemaps were tested to optimize accurate cartographic transfer of tree locations. Detailed data about tree attributes were collected in the field using a portable, preprogrammed computersothatthese data would be compatible with a GIS. The spatial tree location data were joined with the tree attribute data to produce afully functional spatial database for street tree management purposes. Based upon two case studies, the advantages and disadvantages of each project phase are discussed and qualified.

Urban Tree Residues: Results of the First National Inventory

The volume and characteristics of urban tree residues associated with tree pruning and other urban forestry activities have never been well documented, yet disposal of this residue is subject to increasing regulatory actions. The regulatory actions have a considerable impact on the activities of commercial, utility, and municipal tree care operations. This paper reports the results of the first national inventory of the volume and characteristics of urban tree residues. Residues are classified as follows: chips, logs, mixed wood, tops and brush, leaves, lawn clippings, and stumps. Generators of residues include the following: commercial tree care firms, municipal park and recreation departments, municipal tree care divisions, county tree care divisions, electric/telephone utility power line maintenance departments, nurseries, orchards, and landscapers. The national inventory assesses volume, characteristics, and disposal of the residues on both a regional basis as well as by size of metropolitan area. Finally, irregular residue inputs associated with natural disasters are discussed.

Callery Pear Cultivars Tested as Street Trees: Initial Results

Eight callery pear cultivars were planted, two each in ten communities, for evaluation as street trees. They were measured annually during the first three years by cooperators in the Municipal Tree Restoration Program, using standardized methods. Under sometimes stressful site conditions, all the cultivars but one grew well and remained healthy. Two-year height growth of five cultivars varied from 1.0 to 3.4 feet, representing a 7 to 30 percent increase. Diameter growth ranged from 0.4 to 1.0 inches, i.e. average increases of 18 to 68 percent in two years. The health of foliage, branches, and trunks was good to excellent after the first growing season, during which there were occasional signs of transplant shock. The one exception was the Whitehouse cultivar, which grew little in height and exhibited greater foliage injury than the others. Aristocrat, Cleveland Select, and Redspire received the highest overall rating; Autumn Blaze, Cleveland Pride, and Valiant also appear promising, based on more limited data. Bradford is growing well, and has not yet shown signs of breakage which is known to occur when trees become more mature.

Assessing the Feasibility of Collaborative Utility - Municipal Tree Removal and Replanting

In June 1993, Newport Electric Company and the City of Newport, Rhode Island collaborated to complete a tree removal and replanting pilot project. This pilot project was initiated to address the situation that large city-owned trees in Newport are potential hazards to the delivery of safe and reliable electric service, and are costly to trim for adequate clearance. The two primary purposes of this project were: 1) to examine the operational feasibility of a collaborative tree removal and replanting project between the City of Newport and Newport Electric Company; and 2) to cost justify participation by Newport Electric in a tree removal and replanting project. Net Present Value (NPV) is offered as a defensible model for determining cost justified participation by the utility because this method for determining financial worthiness is consistent with other business analyzes conducted within the electric utility industry. If considered over the short-term, participation in a tree removal and replanting project cannot be cost justified, because a financial break-even point will not be realized. This project is cost effective when evaluated over the long-term, because the expense of trimming each tree by the utility is ongoing for several cycles. The willingness of the municipality to share the costs was critical in the decision of the utility to participate.

Street Tree Performance Tests of Crabapple Cultivars: Initial Results

Ten crabapple cultivars are being evaluated as street trees in twelve communities. Using standardized methods, cooperators in the Municipal Tree Restoration Program design plantings, plant trees, and take annual measurements in the first three growing seasons after which they are repeated triennially. Growth in height and trunk diameter varied considerably among locations, as did exposure to diseases and insects. The principal pests were gypsy moth, Japanese beetle, scab, and aphid. The large fruit of Brandywine caused problems in one community, but not in two others. All ten cultivars grew well and remained healthy at most locations, which could be expected because they had been selected for superior street tree growth habit and disease resistance. Minor differences in performance of cultivars during the first three years were not large or uniform enough to recommend one over another, though this may change as evaluations continue. Until then, selections can be based on other traits such as color of flowers or fruit, tree size, and branching habit.

Flow regulation and restoration of Florida's Kissimmee River: L. A. Toth, J. T. B. Obeysekera, W. A. Perkins & M. K. Loftin, Regulated Rivers: Research & Management, 8(1–2), 1993, pp 155–166

Cities are home to an increasing number of people who depend on urban forests to provide ecosystem services such as temperature regulation, air quality improvement and storm water abatement. Climate change may challenge the capacity of urban forests to provide these services. Intensification of heat waves, droughts and strengthening storms could lead to tree die-offs. In Quebec City, work has suggested that the urban canopy is vulnerable to future projected climates, i.e. hotter and drier summers. Compounding this threat, the exotic emerald ash borer is expected to kill 11 % of municipal trees over the next decade. Together these pressures could lead to a significant loss of canopy cover and ecosystem service provisioning in the near-term.We test whether replanting strategies for lost ash, which shift the forest community towards a more climate-tolerant canopy using a functional trait-based approach, can help to mitigate or improve ecosystem service provisioning in the near-term. Using a municipal database of urban trees, we simulate canopy growth and replacement over 20-years for three different replanting scenarios: i) ‘business-as-usual’, ii) ‘stratified’ or iii) ‘conifer-focused’ replanting strategy, and compare their delivery of ecosystem services.Results from the simulations find clear trade-offs in ecosystem service provisioning within and between replanting approaches. The ‘conifer-focused’ scenario provides the highest level of air quality improvement, storm water abatement and reduced energy demands in winter, however there are limitations on where coniferous trees can be planted in cities. In contrast, the ‘business-as-usual’ scenario achieved greater canopy cover, carbon sequestration, and high summertime cooling, but remains vulnerable to climate change. Stratifying replanting across tree functional groups results in the greatest increase to canopy diversity, intermediate levels of ecosystem service provisioning and important reduction in vulnerability to future pests . We suggest that a replanting approach focused on increasing the functional trait diversity of the urban canopy will likely confer the greatest ecosystem service benefits to the urban population and improve the resilience of the urban canopy to pests and climate pressures in the future.

How to Compete for Budget Dollars by Privatizing the Tree Care Operation

Contracting the municipal tree care operation can generally handle specialized tasks more efficiently. It offers greater managerial/technical expertise. Contractors have the ability to manage their workforce more effectively. They can respond to crisis situations more rapidly and can downsize when no longer needed. Contracting only works well when it is functioning under properly trained customer supervision, well written specifications, good contract administration, competition and honesty.