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    Climbers' CornerTree Academy

    Forest Floors under Downtown Pavements: Quantitative Measurements and Trends of Trees in Suspended Pavement 27 Years after Planting


    Stormwater management benefits are one of the most compelling reasons to plant urban trees, and they are also the focus of many “green” policy initiatives. However, few urban trees have enough soil to grow large enough to meet anywhere near their potential ability to manage stormwater at maturity. Providing adequate amounts of rootable soil for the tree to grow to its mature size is crucial to maximizing stormwater benefits: a 40-year-old hackberry tree in Minneapolis is expected to intercept 40 times as much rain as a 5-year-old hackberry, and 14 times as much as a 10-year-old hackberry (McPherson et al 2006).

    Suspended pavement is an innovative technique used to extend rootable soil volume for trees underneath paving, thereby enabling them to live significantly longer, grow larger, and provide greater benefits, while still meeting HS-20 loading. This presentation will share long-term quantitative data on the performance of trees planted in suspended pavement 27 years ago in downtown Bethesda, Maryland, and Charlotte, North Carolina, demonstrating that suspended pavement can be used to grow long lived trees even in ultra-urban areas. Long-term data comparing growth of trees grown in structural soil vs. compacted soil vs. suspended pavement in an urban plaza study will also be presented.


    L. Peter MacDonagh

    Peter MacDonagh co-founded the Kestrel Design Group in 1990 and today serves as its Director of Design + Science. He is also adjunct faculty at the University of Minnesota, where he teaches courses in sustainable design. In addition to being a registered landscape architect and horticulturist, MacDonagh is an ISA Certified Arborist and LEED AP. He has successfully managed more than 100 public projects for local, regional, provincial and national governments. Clients also include municipalities, park districts, watershed districts, schools, corporations, energy utilities and manufacturers. MacDonagh is a recognized authority on sustainable landscape architecture, and is widely sought for his expertise in urban stormwater, green roofs, and urban trees.

    E. Thomas Smiley , Ph.D.

    Dr. Tom Smiley is an arboricultural researcher at the Bartlett Tree Research Laboratory in Charlotte, North Carolina, and an adjunct professor of Urban Forestry at Clemson University. He is active in the arboriculture industry and has co-authored the ISA’s Best Management Practices for Tree Risk Assessment, Lightning Protection, Fertilization, Support Systems, and Construction Management. His research that has led to improved methods of increasing sidewalk  longevity near trees, protecting more trees from lightning damage, improving tree root growth in compacted soil using the patented Root Invigoration process, and better predicting trees failures. His continued studies include tree biomechanics, plant growth regulators, and the development of more efficient tree support systems.

    Climbers' CornerTree Academy

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