Breast Height Age Research Articles

Estimating Site Index of Douglas-Fir (Pseudotsuga menziesii [Mirb.] Franco) from Ecological Variables in Southwestern British Columbia

Abstract Relationships were examined between Douglas-fir site index (at 50 years breast height age), understory vegetation, and site classification units based on 88 sample plots from south coastal British Columbia. Analysis of variance showed differences in site index (P < 0.01) among the site units. Of the regression models tested, the one based on site units plus indicator species groups was most successful in predicting site index (R² = 0.87, SE = 2.96 m, and 75% of cases classified within 3 m of actual site index). The models using indicator species alone as variables had consistently poorer performance, which we attribute largely to inherent variation in understory vegetation. Further testing of the models over a wider range of sites and in earlier seral stages is suggested. For. Sci. 35(1):50-63.

Site Index Curves for Norway Spruce in Southern Ontario1

Abstract Four dominant or codominant Norway spruce trees from each of 55 sites were destructively sampled and the annual height growth determined by stem analysis. The sampled sites were stratified by soil textural class (coarse, medium, and fine) and depth to distinct mottling (0-16, 16-40, and 40 in.). Two sets of an-amorphic site index curves were constructed using a total age of 30 years (SI30), and breast height age of 25 years (SIBH25) as base ages. The mean SI30 from Ontario (53 ft) was found to be 17.8% higher than the mean values published from Vermont (45 ft) and currently used in Ontario. SIBH25 values had a range of 34.6 to 74.8 ft with a mean of 55.3 ft. Analysis of variance showed significant differences in SIBH25 due to soil texture and drainage class, and in years to breast height (BH) due to drainage class. SIBH25 was highest on sites with loamy soils and distinct mottling at 16-40 in. It took an average of 6.5 years for seedlings to reach BH with a range of 3 to 12 years. Years to BH was lowest on sites with sandy soils and those with distinct mottling below 40 in. North. J. Appl. For. 6(1):23-26, March 1989.

Height-growth and site-index curves for jack pine in north central Ontario

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.

Site Index Curves for Unthinned Norway Spruce Plantations in New York

Abstract Polymorphic site index curves were developed for Norway spruce growing in unthinned, old-field plantations in the Allegheny Plateau region of central New York (reference age is 50 years at breast height). Stem analysis data were collected from 151 dominant and codominant trees representing a single but wide-spread soil catena (Bath - Lordstown - Mardin - Volusia; approx. 2.7 million ac). Site index curves at 10-ft intervals for breast height ages 10 to 50 years are furnished for field estimation. For more precise estimates, a table of site index values by 2-ft heights and 2-year ages is provided. North. J. Appl. For. 5:251-254, December 1988.

Three-Dimensional Representation of Douglas-Fir Volume Growth: Comparison of Growth and Yield Models with Stand Data

Abstract Growth and yield estimates for unthinned stands from the Douglas-fir Stand Simulator (DFSIM; Curtis et al. 1981) and the Tree and Stand Simulator (TASS; Mitchell and Cameron 1985) were used to construct graphical three-dimensional representations of Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) stand growth on site index 44 meters (50 year). The three-dimensional models used three variables: trees per hectare, breast height age, and either mean tree volume or stand volume. The TASS and DFSIM models were in agreement over most of their common range of age and number of trees. At wider spacings and older ages, however, the volumes predicted by the DFSIM model exceeded those predicted by the TASS model by as much as 25%. Comparisons of these three-dimensional models to unthinned and thinned stand data from a similar site quality found the models to be reasonably accurate representations of unthinned stand growth. The thinned stands, however, had greater mean tree and stand volumes than those indicated by the TASS model for unthinned stands at similar spacings. Complete comparisons were not possible with the DFSIM model because of its limited range of number of trees. These results suggest the TASS model, and to a lesser extent, the DFSIM model may be underestimating the growth of widely spaced stands, or thinning may actually increase the growth of thinned trees over that of trees which had always grown at the post-thinning spacing. For. Sci. 34(3):724-743.

Early selection for wood density in young coastal Douglas-fir trees

Selection age for wood density in vigorous coastal Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) was determined by examining the following: strength of the correlation between total-stem wood density of 50-year-old trees and their breast-height density when the trees were 5 through 30 years old (breast-height age); efficiency in terms of gain per year of tree improvement effort by selecting at ages 5 through 30, relative to selecting at age 50. The linear regression and rank correlation between total-stem and breast-height densities improved as age increased from 5 to 15 years, but showed no significant improvement from 15 to 30 years. Densities of early-growth rings fluctuated considerably and their exclusion from the calculation of breast-height density enhanced the linear regression with total-stem density. Efficiency estimates in terms of gain per year showed an optimum value at age 15, but the estimates for ages 10–14 were nearly as efficient.

A site index system for redwood and Douglas-fir in California's North Coast Forest

This article evaluates and compares existing site index equations applicable to redwood and Douglas-fir in California’s north coast redwood forest. The authors find previous site index models for redwood to be biased, particularly in younger age classes. They therefore developed new polymorphic site index equations for this species, using both stem analysis and permanent plot data from Humboldt, Del Norte, and Mendocino counties. The new curves use a 50-year breast-height (4.5-foot) age as a base. For Douglas-fir, tests showed King’s site index model for Douglas-fir in Washington and Oregon to be unbiased and adequate for Douglas-fir site index estimation in the north coast. Also, for cases in which appropriate site index trees are available for only one species, the authors give equations to predict redwood site index from Douglas-fir site index or to predict Douglas-fir site index from redwood site index.

Foliar chemical concentrations, growth, and site productivity relations in western red cedar

Important site and tree characteristics of western red cedar (Thujaplicata Donn ex D. Don) were examined in 19 natural stands in the coastal and interior zones of western Washington and Oregon, U.S.A., and in western Vancouver Island, British Columbia, Canada. The stands occurred at various elevations and on different soil types and differed in age, soil pH, and associated plant species. Current-year foliage was collected during the winter and concentrations of N, P, K, S, Ca, Mg, Fe, Mn, B, Zn, Cu, Mo, Al, and the chlorophylls were determined. Mean terminal growth during the previous 3 years and site index at 50-year breast-height age were calculated for each stand. Site index ranged from 18 to 26 m. Terminal growth and foliar concentrations of the macronutrients, micronutrients, Al, and the chlorophylls varied among the 19 sites and between the two zones. Compared with known values for the most common associated conifers, foliar concentrations of red cedar were especially low in Mn and Al and high in Ca and Mo. Site index was correlated positively with N, the chlorophylls, S, Cu, and B, and negatively with Fe and Al. Also, N was positively correlated with the chlorophylls and with some of the other nutrients; there were many correlations among the nutrients and between some nutrients and soil pH or stand age. The data obtained provide base-line information for future analytical work with red cedar foliage. In addition, results suggest that (i) nutrient management strategies in western red cedar stands may differ from those for other conifers and different strategies may be necessary for the coastal and interior zones, (ii) productivity of red cedar may be improved by cultural treatments, including fertilization, which would enhance levels of chlorophyll as well as some essential elements (N, S, P, B, and Mo) in the foliage, (iii) levels of some chemicals in the foliage, such as N, chlorophyll, S, and B, may be useful as indicators to assess site quality for red cedar production, and (iv) chlorophyll may be used as a simple means to estimate N status of red cedar.

Individual Tree Basal Area Increment and Total Height Equations for Appalachian Mixed Hardwoods After Thinning

Abstract Growth response of various species to thinning in even-aged stands of Appalachian mixed hardwoods was predicted with species-specific regression equations. Periodic annual increment over a five-year period was expressed as a linear function of original tree basal area divided by breast height age and a thinning or competition index based on stand basal area. For most species, a combination of stand basal area before and after thinning served as the thinning index; for the five oak species studied, the index was simply stand basal area after thinning. Nonlinear regression equations were formulated to express total tree height as a function of dbh and average height of dominant and codominant white oak. The equations for tree basal area increment and total height may be applied to predict growth after thinning in Appalachian mixed hardwood stands. South J. Appl. For. 10:99-104, May 1986

Site-index Curve Shape in Spruce

Sets of site-index curves were prepared from stem analyses of white spruce (Picea glauca (Moench) Voss) and black spruce (P. mariana (Mill.) BSP.) from various regions in the boreal forest of Canada. Ordinates of the site-index curves, computed for 5-year breast-height age intervals up to 75 years, and for 10-foot site-index intervals up to 70 feet, were compared within the species for the same values of site index and age. For breast-height ages below 55 years and for site index below 70 feet, the maximum absolute difference among the ordinates did not exceed 2.0 feet in white spruce, and 1.6 feet in black spruce; the corresponding average deviations were 0.75 and 0.80 feet. For breast-height ages above 55 years, these differences increased with age and, at 75 years, reached 8.8 feet in white spruce, and 3.8 feet in black spruce; the corresponding average deviations were 4.40 and 1.53 feet.