Abstract
A field-oriented competition index (Shade Index) was developed using a series of mensurational measurements on competitors surrounding individual jack pine seedlings. This index and accompanying software were developed for a hand-held microprocessor, allowing for on-site evaluations.
The Shade Index estimates the percent occupancy of competitor crowns overtopping individual jack pine seedlings within a 1.4 m radius of the subject tree. Using 360 crop treecentred plots situated on six four-year-old plantations, the accuracy of the index was tested against a more complex competition index (Total Canopy Cover) obtained from vertical hemispherical photographs. Both of these indices attempt to quantify the amount of light being intercepted by competitors. A relationship was found to exist between these two indices with Pearson correlation coefficients ranging from 0.82 to 0.90. Linear regression models of seedling diameter regressed against the Shade Index for the different site/stock type combinations are presented. All models were significant at greater than p=0.0001, with coefficients of determination ranging from 0.42 to 0.71.
This index was incorporated into software for a hand-held microprocessor to allow on-site evaluation. These evaluations have the potential to be used to set tending priorities or assess vegetation control measures.
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Morris, D.M., Forslund, R.R. A field-oriented competition index for young jack pine plantations and a computerized decision tool for vegetation management. New Forest 5, 93–107 (1991). https://doi.org/10.1007/BF00029301
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DOI: https://doi.org/10.1007/BF00029301