Research Briefs

Edited by Len Phillips

Better Understand Open Space Conservation in a Developing Watershed

By William F. Elmendorf and A.E. Luloff

A successful process for open space conservation is important in sustaining healthy urban forests and the benefits they provide. Open space must be planned for and financed much like local municipalities plan for schools, roads, and other assets. Steps that could be used for open space planning and conservation include:

• Understanding and documentation of open space resources,

• Understanding growth and development in municipal and county comprehensive plans,

• Including open space conservation as an element in comprehensive plans,

• Sound and progressive zoning and subdivision ordinances,

• A professional development application review process that supports conservation development,

• Good working relations between developers and municipal officials,

• An entity and process for multi-jurisdictional open space planning and acquisition,

• Tools such as bond issues to provide public funding for land acquisition,

• Strong leadership, citizen support, and education about the benefits of open space,

Arboriculture & Urban Forestry, Vol. 32, No. 2, March 2006.

Response of Trees to Inoculations with Mycorrhizal Fungi and Rhizobacteria

By Balakrishna Rao, Donald H. Marx, and Brian Jeffers

Seedlings of tree species were treated by:

• soil injection with mycorrhizal fungi and rhizobacteria;

• drenching with rhizobacteria and soil fungi applied monthly for 5 months;

• a combination of (1) and (2);

• drenching with Subdue® fungicide; or

• non-treated controls.

The introduction of mycorrhizal fungi to the root zone improved ectomycorrhizal development and increased tree stem growth in all species. Subdue drench did not affect mycorrhizal development, root growth, or stem growth on any tree species.

Arboriculture & Urban Forestry, Vol. 32, No. 2, March 2006.

Investigation of Fungicidal Properties of Paclobutrazol to Control Apple Scab

By Ryan A. Blaedow, et.al.

Paclobutrazol (PBZ) used as a systemic fungicide for control of apple scab (Venturia inaequalis) was investigated. Assessments showed that apple scab symptoms in treated trees were as severe as in untreated ones. Growth reduction occurred in all treated trees, suggesting that the PBZ levels needed for growth reduction are not sufficient to control apple scab.

Arboriculture & Urban Forestry, Vol. 32, No. 2, March 2006.

Branch Union Morphology Affects Decay Following Pruning

By Edward F. Gilman and Jason C. Grabosky

More discoloration resulted from removing codominant stems than removing branches that were small compared to the trunk. Removing limbs that originated from lateral buds resulted in the same amount of discoloration and decay as removing suppressed limbs that were once the leader. This result provides indirect evidence that small codominant stems suppressed by pruning techniques designed to slow its growth rate can result in a branch protection zone at the union. There was no relation between the presence of a bark inclusion and decay 4 years after making pruning cuts.

Arboriculture & Urban Forestry, Vol. 32, No. 2, March 2006.

Designing and Implementing Utility Line Arboreta

By Bonnie L. Appleton

In the United States, a significant conflict exists between overhead utility lines and inappropriately tall trees planted in or near line easements. A goal of Virginia’s Municipal Tree Restoration Project is the establishment of utility line arboreta in multiple locations to evaluate, showcase, and promote trees compatible with overhead utility lines. The utility line arboreta demonstrate to the public, designers, and municipalities that a wide variety of small trees and large shrubs, with low mature heights can help extend line-clearance cycles. These trees are readily available in nurseries in the United States.

Arboriculture & Urban Forestry, Vol. 32, No. 2, March 2006.

Plant Communities of Selected Urbanized Areas

By K. Turner, L. Lefler, and B. Freedman

This study was designed to compare plant indicators among urban residential areas and natural habitats in the vicinity of Halifax, Nova Scotia. In general, the observed plant species richness was much higher in the residential areas, but these habitats were strongly dominated by non-indigenous species, whereas the natural and semi-natural habitats supported native taxa.

Landscape and Urban Planning, 2004. 71(2–4):191–206.

Nature in the Retail Environment
By Kathleen L. Wolf

Most research addressing public response to the urban forest has occurred in residential settings while little is known about consumer response to trees in retail places. Trees are highly preferred by consumers, although business people express slightly lower liking for visual categories containing trees.

Landscape Journal, 2004. 23(1):40–51.

Potential Hazard Characteristics of Trees Removed in Helsinki

By Minna Terho and Anna-Maija Hallaksela

To study decay and to improve the management and protection of old urban trees, a total of 256 felled urban trees were examined. Most of the trees (73%) were located in the main parks and along the main streets in the downtown area of Helsinki, Finland. The mean age of the trees was over 60 years, and the majority (64%) were old park trees. Poor condition and increasing risk of failure were the main reasons for felling in 82% of the cases. Thirty-three percent (33%) of these trees were degenerated or dead, but 14% of the risk trees were big, old trees that posed a potential hazard but had a vital and balanced crown. Potential failures were identified for each of the tree species studied: decay fungi (Ganoderma lipsiense) in the butts and hollows and weak fork formations from Rigidoporus populinus decay in the stem.

Urban Forestry and Urban Greening, 2005. 3(2):113–120.

Comparison of Green Roofs in Southern Sweden

By Tobias Emilsson and Kaj Rolf

The most common technique for establishment of green roofs in Sweden was the use of prefabricated vegetation mats. The establishment of the vegetation, which consisted of succulents, was recorded:

• Prefabricated vegetation mats had higher succulent plant cover than on-site constructed roofs.

• There was no difference in plant cover between plots using plug-plants compared to shoots.

• Shoot-established plots had more moss than the other establishment methods.

• The commercial substrate “roof soil” had significantly higher succulent plant cover than the other substrates, which might be related to a higher nutrient content.

• The organic content of the non-commercial substrates was rapidly decomposed.

• The standard species mixture produced a higher cover than both the mix developed for northern conditions and the mix with an increased proportion of big-leaved species.

• Few species managed to establish spontaneously, but the establishment of woody species highlighted the need for proper maintenance.

Urban Forestry and Urban Greening, 2005. 3(2):103–111

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