Title page for ETD etd-12142010-150948


Type of Document Master's Thesis
Author Layman, Rachel Montgomery
Author's Email Address ralayman@vt.edu
URN etd-12142010-150948
Title Rehabilitation of Severely Compacted Urban Soil to Improve Tree Establishment and Growth
Degree Master of Science
Department Horticulture
Advisory Committee
Advisor Name Title
Day, Susan D. Committee Co-Chair
Harris, James Roger Committee Co-Chair
Daniels, Walter Lee Committee Member
Wiseman, P. Eric Committee Member
Keywords
  • canopy; tree roots; minirhizotron; organic amendme
Date of Defense 2010-12-02
Availability unrestricted
Abstract
Land development restricts tree growth by damaging soil structure and removing organic matter. Mechanical loosening and organic amendment may improve soil physical properties and tree establishment and growth. Effects of typical post-construction practice and improved methods of soil restoration on tree growth and soil properties were evaluated over two years. Treatments included undisturbed soil (UN); minimum effort (ME) (10 cm topsoil); enhanced topsoil (ET) (ME + rototilling); and profile rebuilding (PR) (compost, subsoiling, topsoil and rototilling). Pretreatment included removing topsoil and compacting subsoil to 1.95 g/cm3 bulk density. Acer rubrum L. (red maple), Quercus bicolor Willd. (swamp white oak), Ulmus ‘Morton’ (Ulmus japonica (Rehd.) Sarg. x Ulmus wilsoniana Schneid.) (Accolade elm), Prunus ‘First Lady’ (Prunus xincam x Prunus campanulata) L. and Quercus macrocarpa Michx. (bur oak) were planted in each plot. The PR treatment reduced soil bulk density at 15-20 cm depth and increased soil C/N ratio, pH, and CEC. Mean canopy projection and cross-sectional trunk area in PR plots ranged from 32% to 226% and 16% to 71% greater, respectively, than those in ME plots. PR treatment increased Q. bicolor photosynthesis rates. Greater root presence was observed in deeper soil layers of ET and PR treatments for A. rubrum and of UN and PR for Q. bicolor; root distribution was not measured for other species. Rehabilitation improved soil physical properties and tree growth after two years. Species variation in growth rate and environmental tolerance appeared to influence early growth treatment effects. Long-term data is needed to fully understand effects of soil rehabilitation.
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