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    Climbers' CornerTree Academy

    Evaluation of Established Trees Planted in Structural Soils


    Loam Soil under Suspended Sidewalks (LSSS) and Sand Based Structural Soil (SBSS) are currently used to improve the growing conditions of street trees.  There has been little evaluation of the effectiveness of these approaches and both are currently being used in many locations around the United States.  The LSSS  approach was first used on a large scale in Bethesda, Maryland. Between 1983 and 1990, approximately 25 blocks of street trees were planted during a series of citywide streetscape improvement projects.  In Boston, Massachusetts, a large number of projects including the Rose Kennedy Greenway were built between 2003 and 2008 using the SBSS approach.  During this same period a number of other Boston projects including one block of the Greenway and the Convention Center were built using the LSSS approach.  In each city, the number of trees is sufficiently large, of reasonable maturity and consistency in construction, and with sufficiently diverse species to provide a set of conditions to be the basis for a case study of each approach.  Data was collected in Boston in 2011 and 2013.  The Bethesda data was collected in 2013.  Approximately 400 trees were evaluated for their growth rates and general health.  This data along with information on how each approach was constructed and maintained will be presented as a comparative case study.  The presentation will include the results of the growth and health ratings, as well as a discussion on construction, lessons learned and cost.    


    James R. Urban, ISA, FASLA

    James Urban specializes in the design of trees and soils in urban spaces. He has written and lectured extensively on the subject of urban tree planting and has been responsible for the introduction of many innovations including most of the current standards relating to urban tree plantings.  His 2008 book ‘Up By Roots: Healthy Trees and Soils in the Built Environment’, is becoming one of the principle tree and soil references. James Urban was instrumental in the development of structural cells and structural planting soils for use under sidewalk pavements, and is credited with helping to re-awaken the profession of landscape architecture to the skills required to successfully plant trees in difficult urban soils. In 2007 he was awarded the ASLA Medal of Excellence for this contribution the profession of Landscape Architecture. He is the 2013 recipient of the ISA Award of Achievement for long-term contributions to the profession of arboriculture.

    Dr. Tom Smiley is an arboricultural researcher at the Bartlett Tree Research Laboratory in Charlotte, NC and an adjunct professor of Urban Forestry at Clemson University.  Dr. Smiley 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 has lead 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 predicting tree failures.

    Climbers' CornerTree Academy

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