Diameter distributional trends within mixed black-spruce/balsam-fir and pure black-spruce stand types

Abstract

This study describes and compares (i) the diameter distribution of black spruce ( Picea mariana (Mill.) B.S.P.) and balsam fir ( Abies balsamea (L.) Mill.) within mixed black-spruce/balsam-fir stands, and (ii) the diamter distribution of black spruce within pure stands, at various stages of stand development. Employing relative-frequency diameter-class data from 128 0.081-ha semi-permanent sample plots located in natural mixed (57 plots) and pure (71 plots) stand types of central insular Newfoundland, 1st, 2nd, 3rd and 4th-order polynomial functions were used to describe stand structure at various species heights. The Chi-square statistic was used to compare distributions within and between stand types by height class. Results indicated that both species within mixed stands, and black spruce within both stand types, had similar distribution trends, i.e., initially reverse J-shaped or positively-skewed unimodal distributions progressing to a semi-bimodal or positively skewed mound-shaped distribution. Black spruce occupied a slightly greater proportion of the larger diameter classes, whereas balsam fir occupied a slightly greater proportion of the smaller diameter classes, indicating a semi-stratified structure.