An Investigation -- Methods to Predict Radial Growth in Urban Trees
Knox, Stephen E.
University of Wisconsin-Stevens Point, College of Natural Resources
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UW/SP URBAN FOREST and URFOR/SIMULATION, computerized street tree inventory system and related management simulation, estimate present and future tree values. Since, value is based on diameter, a reliable, least cost method of predicting diameter growth is required by its authors. Current procedures require sampling 2% to 5% of the population for previous ten year growth. Results indicate the urban trees growth patterns vary widely, with no correlation to species or diameter (age). But, in spite of wide variation, the method in use predicts growth reasonably well. Depending on the selection of probability level and standard deviation from the mean by the user, cost of collection and processing of growth data can be significantly reduced. In the city of Milwaukee, 552 growth samples were collected in 1979. At a 0.05 probability level and a standard deviation from the mean of 5%, 162 sample trees are required. At the 0.10 probability level with 10% deviation from the mean, only 29 samples are required. Growth projection alternatives investigated failed to improve the regression method currently in use.