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dec home > wsmd home > erp > green infrastructure > green stormwater infrastructure > urban tree canopy

Urban Tree Canopy

 

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Vermont has a long history of managing its forests for multiple uses - including timber, fuel wood, wildlife, habitat, and recreation. In addition to the 4.5 million acres of land that we traditionally viewed as forestland, another forest touches our lives everyday: our urban and community forest. Trees along streets, in parks and town greens, and on municipal forest lands are our community forests. These trees provide numerous environmental, social and economic benefits, however, they are not always managed as a community resource. In Vermont, assistance in urban and community forestry is provided by the Urban and Community Forestry (UCF) Program. The program's mission is "To promote the stewardship of urban and rural landscapes to enhance the quality of life in Vermont communities."

Choosing the right trees for an urban landscape is an important process to go through. The urban environment can be harsh for trees, so it is vital that you choose species that can handle the variety of conditions which exist in urban settings. When considering what types of trees to plant, an excellent resource is the Vermont Urban & Community Forest Program's Tree Selection Guide.

If you would like information on Vermont's Urban & Community Forestry Program, please contact the UCF Program Coordinator Danielle Fitzko, in the Department of Forest, Parks and Recreation.

Trees protect water and soil resources by reducing the amount of runoff and pollutant loading through evapotranspiration, interception and infiltration. A healthy urban tree canopy also provides the added benefit of shade and lower urban heat indices. There are several technologies currently available to support urban trees, with a wide range of benefits and applications.

Tree Boxes

Tree boxes are amongst the most common practices used when installing urban trees. These concrete boxes are filled with soil and inserted into sidewalks, parking lots, and other paved areas. They are often favored due to the fact that they provide a barrier for the root system, preventing the tree canopy from expanding beyond a certain point that could interfere with above ground utility lines. Unfortunately, restricting the root system of a tree in this way often causes a tree a large amount of stress. When the tree cannot "explore" below ground for water and nutrients, we often see a loss of vegetation, suceptibility to disease and invasive insects, and a general loss of environmental function.

In managing stormwater, tree boxes are often equipped with an outlet so when water begins to collect in the bottom it can then drain into the municipal sewer system. The freshly filtered stormwater is then recombined with other contaminated runoff - which is not ideal.

 

Tree Box Installed
Tree Box

 

Silva Cell©

Silva Cells© essentially function as underground scaffolding for trees. They can be stacked one, two, or three units high depending on the desired soil volume and number of trees being planted. The structure is then filled with soil and trees are planted in gaps along the length of the structure. The area is then paved over, preventing harmful soil compaction during the paving process and throughout the life of the surface - allowing trees the space, nutrients, and water holding capacity they require to thrive.

The Silva Cell© is a product of DeepRoot, and more information on this product can be found on their website: www.deeproot.com

Silva Cell

CU-Structural Soil

In response to the unique needs of the urban forest, the Cornell University Urban Horticulture Institute developed a product that would help mitigate the challenges in establishing urban trees. Soil compaction, lack of nutrients, improper pH levels, and inappropriate water holding capacities have long been cited as major barriers to establishing a healthy, high functioning urban tree canopy.

CU-Structural Soil™ is a two part system. The first part (approximately 80% of the mixture) is composed of a rigid aggregate to provide load-bearing capacity, stability, and void space for root intrusion and the movement of air and water. The second part, making up around 20% of the mix, clays and clay-loams to promote nutrient and water holding capacity in the soil. To ensure the clay remains "suspended" between the larger aggregates, a non-toxic, non-phytotoxic substance known as Gelscape® hydrogel is included in the mixture as well.

More information on the technical specifications of CU-Structural Soil can be found in Cornell University's publication Using CU-Structural Soil in the Urban Environment.

CU-Soil

 

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