Towards an Improved Rapid Urban Site Index
B.C. Scharenbroch, L. Scheberl, J.C. Gebhard, J.R. Prater, and L.P. Werner
Abstract: Background: An urban site index is an approach for identifying site quality for optimal matching of urban tree tolerances to site conditions and for determining the efficacy of soil management actions. The Rapid Urban Site Index (RUSI) was previously developed and found to significantly relate to urban tree performance. However, the RUSI needs further testing to verify its accuracy in other urban tree populations. Furthermore, calibration of the RUSI with parameter weighting and additional parameters might also improve its accuracy. Methods: The objectives of this study are to: (1) evaluate the RUSI in 3 Wisconsin cities; (2) evaluate RUSI parameter weighting models to improve its accuracy; and (3) examine the addition of a labile organic matter indicator to the RUSI for detection of a soil management action. Results: The RUSI was found to significantly correlate to urban tree metrics in 3 Wisconsin cities (r = 0.29 to 0.31; n = 90). Parameter weighting increased significant correlation values between urban tree metrics and the RUSI model (r = 0.24 to 0.37; n = 90). The SolvitaŽ soil respiration test detected differences in soils from a biosolids application (P = 0.0275), and its addition to the RUSI model improved significant correlation values to urban tree metrics (r = 0.27 to 0.38; n = 90). Conclusions: This research demonstrates effective approaches for RUSI refinement. These findings show the RUSI to be a valid approach for urban site assessment and demonstrate how the RUSI can be tailored and refined for use in specific urban tree populations.
Keywords: Site Assessment; Soil Quality; Urban Soils; Urban Tree Growth; Urban Tree Health