Soil Quality Attributes as Indicators of Urban Tree Performance

Abstract

Soil quality assessments are needed to improve a professional’s ability to manage urban soils and trees. This research was conducted to identify which soil properties are most useful for relating information on urban tree performance. In total, 48 soil properties were measured at 84 sites from five urban landscapes in the western suburbs of Chicago, Illinois, U.S. Key physical, chemical, and biological properties to be included in a minimum data set (MDS) for assessing urban soil quality were identified using statistical approaches and practical considerations. The MDS included: texture, bulk density, wet-aggregate stability, pH, electrical conductivity, soil organic matter (SOM), and particulate organic matter. The MDS was used to establish an urban soil quality index (USQI). The MDS and USQI were highly correlated with tree size attributes of height, trunk diameter, crown area, and age. Correlations between the MDS and USQI with trunk diameter growth rate, height growth rate, foliar N, and chlorophyll content were often significant, but less strong. Among the MDS parameters, SOM, pH, and texture appear to be the most informative measures for soil quality relating to urban tree performance. Soil quality and tree performance increased logarithmically following site disturbance, with a plateau after 50 years.