No abstract

Height-growth patterns for jack pine (Pinusbanksiana Lamb.) were studied using stem analyses from dominant and codominant trees on 141 plots in north central Ontario. All plots were in natural, well-stocked, even-aged stands 50 years of age or older. Data from 32 of the 141 plots were randomly selected to confirm results, the remaining 109 plots were used for computing the curves. Height-growth curves were developed using a five-parameter Chapman–Richards nonlinear regression that expressed height as a function of age and site index. A site-index prediction equation was also computed using a similar model that expressed site index as a function of age and tree height. Estimated site index using height-growth curves based on the 109 computation plots agreed closely with site index observed from stem analyses on the 32 confirmation plots. Major results were as follows: (i) height-growth curves based on breast-height age were more accurate than curves based on total age; (ii) polymorphic height-growth patterns were related to site index, becoming more curvilinear as site index increased; (iii) average height-growth patterns were similar for jack pine growing on four glacial landforms: shallow and deep moraines, outwashed glacial sands, and lacustrine clays and silts; and (iv) height-growth patterns for ages less than 50 years were very similar to patterns of the commonly used Plonski curves for jack pine site classes in Ontario, but after 50 years, height growth was somewhat better for all sites than predicted by the Plonski curves.

A comparison of growth and yield prediction models for ioblolly pine. Blacksburg,VA: Clatterback,Wayne K. 1987. Height growth and site Virginia PolytechnicInstituteand State University, Index curves for cherrybark oak and sweetgum in School of Forestryand WildlifeResources.59 p. mixed, even-aged stands on the minor bottoms of central Misslsslppi. SouthernJournalof Applied Carmean, Willard H. 1968. Tree height growth pat-Forestry.11: 219-222. terns In relation to soil and site. In: Proceedings, 3d North American forest soilsconference:tree Clutter,JeromeL.; Lenhart, J. David. 1968. Site Index growthand forest soils;Corvallis,OR: Oregon State curves for old-field Ioblolly plne plantations in the UniversityPress: 499-512.

Stem-analysis data from dominant and codominant trees were collected from 383 plots located in fully stocked, even-aged, undisturbed mature jack pine stands. Separate site index curves were independently formulated for four regions of northern Ontario using the Newnham constrained nonlinear regression model; these formulations were used for comparing regional site index curves at three levels of site index (10 m, 15 m and 20 m).Comparisons showed that no significant differences existed between the four regional curves as well as with previously published site index curves for the North Central Region. Each of the four regions had similar polymorphic height-growth patterns; therefore, data for the four regions were combined and a single formulation was used to develop a polymorphic set of site index curves for all of northern Ontario. We found that poor sites in each region had almost linear height growth up to 100 years breast-height age, but for each region height growth became more curvilinear with increasing site index. The recommended site index curves for northern Ontario are based on a formulation using only data from plots 100 years and less but this formulation was not significantly different from a formulation using only data from plots 80 years and less, or a formulation that included all data from plots older than 100 years breast-height age.Comparisons were made between our northern Ontario curves and other jack pine site index curves for Ontario as well as curves for other areas of Canada and the United States. These comparisons generally showed considerable older age differences. Reasons for these differences are uncertain but could be due to differences in the amount and kind of data used for these other curves, could be due to differences in analytical methods, or could be due to regional differences in climate, soil and topography.

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.