Forest Investment Account (FIA) - Forest Science Program
FIA Project Y051256

    Evaluation of the simulation model SORTIE for prediction of growth and yield in mixed aspen spruce stands [2005 Project Description Only]
Imprint: Vancouver, B.C. : University of British Columbia, 2005
Subject: Forest Investment Account (FIA), Trees, Growth, SORTIE (Computer Program)
Series: Forest Investment Account (FIA) - Forest Science Program
The main objective of this study was to perform an evaluation of SORTIE-ND as a predictive model for growth and stand dynamics in mixed boreal and sub-boreal stands. Evaluation is here defined as a process in which a modelís conceptual structure and predictions are described and assessed with regard to a specific purpose. The evaluation performed in this study had three main components. Initially, the model was evaluated in terms of its logic and conceptual structure. This was done to identify obvious structural limitations of the model. Secondly, a sensitivity analysis of the model was performed. This provided information on the modelís sensitivity to uncertainty about the parameter estimates and indicated the parameters with greatest influence on predictions. Third, the model predictions were compared to independent observations of growth from permanent sample plots. This provided information on ranges of accuracy and precision of stand-level predictions. The performed evaluation of SORTIE-ND gave generally positive results. The model was found to produce biologically believable predictions of stand development patterns for both single-species and mixed-species stands of aspen and spruce. Our sensitivity analysis indicated that the uncertainty about input parameters can produce large errors in predicted outcomes. Despite this variation, the predictions of stand development maintained a plausible pattern. The comparison to permanent sample plots illustrated two main points. First, the model predictions and the observations were generally found to conform well. Secondly, it was found that the model generally overestimates the site quality for mesic sites in the SBS.
Bruce Larson.
Contact: Larson, Bruce, (604) 822-1284,

Updated August 16, 2010 

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