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Effects of competitor spacing in a new class of individual-tree indices of competition: semidistance-independent indices computed for Bitterlich versus fixed-area plots


Stage, Albert R.; Ledermann, Thomas. 2008. Effects of competitor spacing in a new class of individual-tree indices of competition: semidistance-independent indices computed for Bitterlich versus fixed-area plots. Canadian Journal of Forest Research. 38: 890-898.

We illustrate effects of competitor spacing for a new class of individual-tree indices of competition that we call semi-distance-independent. This new class is similar to the class of distance-independent indices except that the index is computed independently at each subsampling plot surrounding a subject tree for which growth is to be modelled. We derive the effects of distance for this class as the expected value over independent samples containing a particular subject tree. In a previous paper, we illustrated distance effects implicit in eight indices of the distance-dependent class. Here, we present distance effects of four semi-distance-independent indices: density, sum of diameters, basal area, and tree-area ratio; each determined for small fixed-area plots of 0.04ha and for Bitterlich samples of 6m2·ha-1. We show that several members of this new class have distance effects very similar to the distance-dependent class and should, therefore, be equally effective in accounting for competitive effects in individual-tree increment models. The comparisons should inform selection of competition indices and sampling designs for growth modelling.

Keywords: competitor spacing, individual-tree indices, subsampling, density, sum of diameters, basal area, tree-area ratio


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Title: RMRS Other Publications: Effects of competitor spacing in a new class of individual-tree indices of competition: semidistance-independent indices computed for Bitterlich versus fixed-area plots
Electronic Publish Date: August 20, 2008
Last Update:
August 20, 2008

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