Polymorphic site index curves for black spruce and trembling aspen in northwest Ontario

Abstract

Site index curves were developed using stem-analysis data from dominant and codominant trees in 230 black spruce and 194 trembling aspen plots located in mature, well-stocked, even-aged stands. Black spruce plots were in five separate and independent data sets located on mineral and organic soils; trembling aspen plots were in three separate and independent data sets located on mineral soils. Computations showed that the Newnham nonlinear regression model was slightly more precise than other models commonly used for developing site index curves. This model accurately expresses polymorphic height growth for a wide range of site index and age and constrains predicted height to agree with specified 50-year tree height (site index). Computations showed that height-growth curves were similar for each of the five black spruce data sets; likewise, curves for each of the three trembling aspen data sets were similar. Therefore, the five black spruce and the three trembling aspen data sets were combined for computing a single set of black spruce and a single set of trembling aspen site index curves for Northwest Ontario. Comparisons between our Northwest Ontario site index curves and other black spruce and trembling aspen curves showed large differences in height-growth patterns for older ages. Reasons for these differences are uncertain but in many instances these could be artifacts related to study methods involving various amounts and kind of data and variations in analytical techniques. In some cases differences in climate, soil and topography may also be related to variations in these site curves.

Growth and yield comparisons for red pine, white spruce and black spruce plantations in northwestern Ontario

“…Our good white spruce site indices are similar to good white spruce site indices reported by Stiell and Berry (1973), Rauscher (1987), and Carmean et al (2006a). And our good black spruce site indices are similar to good black spruce site indices reported for natural black spruce stands (Carmean et al 2006b). …”

“…Stem analysis used for site index curves for natural even-aged black spruce stands in northwestern Ontario (Carmean et al 2006b) also indicate that about seven years are needed for trees to reach breast height. Breast-height age for each of these site index curve studies was used because stem analyses from the above studies showed that height growth below breast height is slow and erratic.…”

Site index comparisons for forest species in the Upper Great Lakes area of the United States and Canada

“…However, only a few of those comparisons have aspen site indices less than 40 feet. Reasons for this lack of poor-site aspen plots are indicated in studies for northwest Ontario where few merchantable trembling aspen stands occur on poor sites such as dry sands, shallow to bedrock morainal soils, or poorly drained soils (Carmean 1996, Carmean and Li 1998, Carmean et al 2006. Trembling aspen may regenerate on these poor sites but defect and early "stand breakup" occurs, thus few older merchantable aspen stands are found on such poor sites.…”

Validation of empirical yield curves for natural-origin stands in boreal Ontario

“…As a result, site index curves from the literature were evaluated against the observed height development patterns in the data. Woods and Miller (1996) was used for white and red pine; Carmean et al (2006) for trembling aspen and black spruce; Carmean et al (2001) for jack pine; Carmean (1996) for white spruce, balsam fir, white birch, and tamarack (Larix laricina [Du Roi] K. Koch); and Carmean et al (1989) for the remaining species. Some site index curves use breast height age rather than total age.…”