A traditional focus of soil research in urban forestry and arboriculture care has been on improving physical and chemical properties of soils to promote tree health. The effects of soil amendments (e.g., mulching, fertilization, and compost teas) on soil biology are not well-understood, but are likely very important for landscape tree care. Biological components of the soil environment are critical for healthy plants. In undisturbed woodlands, soil organic matter contents are high and the microbial population is typically fungal-dominated. Disturbed urban soils have relatively lower organic matter content; and, these soils (especially if planted to turf) are usually bacteria dominated. Tree health on sites that have been scraped, compacted, and filled is dependent on rebuilding soil organic matter and reestablishing fungal-dominated soil biology. An urban soil research plot has been created in the research grounds at the Morton Arboretum, Lisle, IL USA. Topsoil has been stripped, and the underlying subsoil compacted with nominal depth of topsoil replaced. In the spring of 2007, sixty red maple (Acer rubrum) and sixty river birch (Betula nigra) were planted in a randomized complete block. The overall goal of this research is to determine the effectiveness of arboricultural amendments (mulch, compost, compost tea, other biological soil amendment, and fertilization) to improve soil quality and tree health in disturbed urban environments. The project is funded in part by a TREE Fund Hyland R. Johns Grant. The results were presented at the 2011 ISA conference in Sydney, Austraila.

CRUD - Compaction and Remediation of Urban Dirt (2007-2011)

Initial site disturbance (top-left), compost and mulch plots (top-right), compost tea application (bottom-left), soil water sampling (bottom-right).