Arboriculture & Urban Forestry

In urban areas there is a limited amount of soil space available for tree root growth. However, many systems have been developed that provide rooting space below pavement while supporting the weight of vehicles and pedestrians. Two main approaches have emerged: 1) supported pavement, and 2) structural growing media. This research was composed of two controlled studies that compare variations of these two approaches. The first was a 10-year study using elm trees that compared gravel-based structural soil (GBSS), expanded slate structural soil (ESSS), expanded slate (ES) alone, a concrete supported pavement and a compacted control. The second study was a four-year study using Liriodendron trees that compared GBSS, sand-based structural soil (SBSS), Silva Cells™, Stratacells™, an open control, and a compacted control. The results of these two studies showed that the trees growing in the supported pavement treatments with low-density soil media resulted in significantly greater tree growth and a healthier appearance. The treatments with the highly compacted soil media had less root development and less top growth. However, soil media that were highly compacted experienced less subsidence. (A, M, Bs, Bm)

Cities contain dozens of street tree species, each with multiple arthropod pests. A survey was used to identify the most common and damaging pests of the most common trees in the southeastern U.S.A. Tree genera varied in number of common pests from Zelkova, which has few pests, to Quercus, which has many pests from many feeding guilds. Sucking pests, such as aphids and scale insects, were rated among the most important pests on several tree genera, including Acer, Liriodendron, and Lagerstroemia. Defoliators, primarily caterpillars, were ranked highest on Quercus spp. Knowledge of the most common and damaging pests will help focus integrated pest management development and educational activities. (A, M, Bs, Bm)

Limited water availability can cause significant stress to newly transplanted urban trees, necessitating supplemental watering during the tree establishment period. The authors compared three types of indirect watering devices in terms of their performance and their benefits to newly transplanted river birch (Betula nigra) trees in a controlled greenhouse environment. (A, M, T, Bm)

The topic of wire basket removal during planting remains an area of contention among nursery growers, landscapers, and arborists who work with balled-and-burlapped planting material. Those in favor of removal fear that the burlap and wire will impede root regrowth and lead to girdling roots, while those opposed to removal believe leaving materials intact improves transplant stability and establishment. (A, M, Bp)

Roadside trees provide benefits to drivers such as traffic calming, roadway definition, and driver stress reduction. However, trees are also one of several roadway infrastructure elements commonly involved in single-vehicle crashes. In this study, Florida Highway Safety and Motor Vehicle records were analyzed to: evaluate the relative frequency of tree-related crashes compared to other fixed-object crashes; assess the impact of roadway-, vehicle-, and driver-related factors on tree crash frequency; and compare the severity of tree crashes relative to other single-vehicle crashes. (A, M, Bm)

The urban forest is a valuable ecosystem service provider, yet cities are frequently degraded environments with a myriad of stressors and disturbances affecting trees. Vulnerability science is increasingly used to explore issues of sustainability in complex social-ecological systems, and can be a useful approach for assessing urban forests. The purpose of this study was to identify and explore drivers of urban forest vulnerability in a residential neighborhood. Understanding the causes of urban forest change and decline are essential for developing planning strategies to reduce long-term system vulnerability. (A, M, T, Bm)

Volunteerism is one way to handle limited resources for municipal inventories. This study follows the Forest Health Ambassador Program and how it used volunteers to track signs and symptoms of infestations by emerald ash borer, gypsy moth, and Asian longhorned beetle. (A, M, Bs)

Apple and pear scab caused by the fungal pathogens Venturia inaequalis and V. pirina can be devastating to apples (Malus spp.) and pears (Pyrus spp). This article details two UK field trials that assessed the efficacy of alternatives to the synthetic fungicides frequently used in fruit production, including a range of silicon fertilizers, a resistance-inducing (IR) agent, and a combination of Si + IR. (A, Bs)

While the industry-standard black plastic container has many advantages in woody plant production, circling and girdling roots on plants grown in them can lead to a variety of post-transplant problems. Plants grown in fabric containers may have fewer circling and girdling roots, potentially eliminating some transplant problems. This study evaluated post-transplant root and shoot growth of Pyrus calleryana ‘Glen’s Form’ (Chanticleer®) produced using three container types. (A, Bs)

It is challenging to successfully grow trees in highly-urbanized areas, such as downtown commercial-retail districts. This research reports on an investigation of multiple abiotic factors that may have contributed to the decline and mortality of 133 London planetrees that were planted in downtown Toronto, Ontario, Canada as part of a streetscape revitalization project. (A, M, Bs)

The costs of collecting data necessary for urban forest management can be prohibitive for communities with inadequate financial or staffing resources. In this study, researchers assessed volunteer efficacy and the effect of training protocols on data quality by comparing volunteer-collected and university-collected tree inventory data in nine Minnesota, U.S. communities. (A, M, Bm)

Integrated vegetation management programs have successfully reduced the frequency and intensity of power line right-of-way management by promoting low-growing plant communities resistant to tree invasion. To examine whether these principles are transferable to northern ecosystems, researchers tested different methods of imazapyr and triclopyr treatments in Yukon, Canada. (A, U, Bs)