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    Author(s): Jacek Bankowski; Daniel C. Dey; Eric Boysen; Murray Woods; Jim Rice
    Date: 1996
    Source: Forest Research Information Paper. Issue 130. 1996. pp. 1-21
    Publication Series: Scientific Journal (JRNL)
    Station: North Central Research Station
    PDF: View PDF  (964.5 KB)

    Description

    The individual-tree, distance-independent stand growth simulator NE-TWIGS has been tested for Ontario's tolerant hardwood stands using data from long-term permanent sample plots. NE-TWIGS provides reliable short-term (5-year) predictions of stand basal area (modelling efficiency from 77% to 99%), but in longer projections the efficiency of the model drops significantly. Basal area is underestimated an average of 2% to 5% for 5-year projections (with exception of the data set representing low-productivity sites). The error of basal area for individual stands ranges from -22% to 37%. NE-TWIGS is not reliable for predicting basal area by timber size classes, particularly those for medium and large sawlogs. In over 51% of stand projections, the predicted diameter distribution is significantly different from the actual distribution, primarily due to the ingrowth function. Thus, calibrating the ingrowth model is recommended for Ontario conditions. NE-TWIGS uses Site Index as ameasure of site productivity, but this data was not available for this analysis. Inclusion of site productivity data may have improved the performance of NE-TWIGS.

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    Citation

    Bankowski, Jacek; Dey, Daniel C.; Boysen, Eric; Woods, Murray; Rice, Jim 1996. Validation of NE-TWIGS for tolerant hardwood stands in Ontario. Forest Research Information Paper. Issue 130. 1996. pp. 1-21

    Keywords

    growth model, tolerant hardwood, thinning, timber class, basal area, stand ensity, stand volume

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