Effect of Index Age on the Precision of Site Index

1973 ◽  
Vol 3 (1) ◽  
pp. 1-6 ◽  
Author(s):  
L. Heger
Keyword(s):  
Confidence Interval ◽  
Random Error ◽  
White Spruce ◽  
Site Index ◽  
Regression Method ◽  
Curve Shape ◽  
Breast Height

Effect of index age on the probable size of random error in site index was evaluated by comparing the 95% confidence interval for site index by curves based on index age 50 years at breast height (BH) with that by curves based on index age 100 years at BH. The curves were constructed using the regression method and stem analyses of 181 dominant white spruce trees (Piceaglauca (Moench) Voss). Using curves based on index age 100, a 10-ft index class could not be identified with 95% confidence for BH ages below about 50 years even if these curves were entered with sample averages of 50 dominant heights. Using curves based on index age 50, a 10-ft index class could be identified with 95% confidence for BH ages 20–100 years if these curves were entered with sample averages of at least 15 dominant heights. Effect of index age on the outcome of curve shape comparisons was discussed.

scholarly journals Site-index Curve Shape in Spruce

1969 ◽  
Vol 45 (3) ◽  
pp. 184-186 ◽  
Author(s):  
L. Heger
Keyword(s):  
Picea Glauca ◽  
Black Spruce ◽  
White Spruce ◽  
Site Index ◽  
Absolute Difference ◽  
Curve Shape ◽  
Breast Height ◽  
Maximum Absolute Difference ◽  
Site Index Curve ◽  
Index Curve

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.

Confidence Interval for Site Index Using Curves Based on Stem Analyses

1971 ◽  
Vol 1 (4) ◽  
pp. 241-245 ◽  
Author(s):  
L. Heger
Keyword(s):  
Confidence Interval ◽  
Sample Size ◽  
Confidence Intervals ◽  
White Spruce ◽  
Site Index ◽  
Stand Age ◽  
Average Quality ◽  
Breast Height ◽  
True Value ◽  
Index Level

A method was described for the derivation of confidence intervals for site index using site-index curves based on stem analyses. The method allows assessment of effects on index estimates due to stand age, index level, sample size of heights used in entering the curves, index age, and sample size underlying the curves. Of these effects, the first three were evaluated for a set of curves based on stem analyses of white spruce (Piceaglauca (Moench) Voss) and on index age of 50 years at breast height (BH). With sample averages of 20 heights, about 95% of index estimates were within ±5 ft (1.52 m) of the true value in spruce 25–100 years old at BH on both average quality and extreme quality sites. To ensure this precision in spruce younger than 15 years at BH, 50 heights were required on the average sites and more than 50 on extreme sites.

scholarly journals Site-Index Curves and Growth Intercepts for Young White Spruce Plantations in North Central Ontario

2006 ◽  
Vol 23 (4) ◽  
pp. 257-263 ◽  
Author(s):  
Willard H. Carmean ◽  
Gerrit Hazenberg ◽  
James S. Thrower ◽  
Richard R. LaValley
Keyword(s):  
Regression Model ◽  
Nonlinear Regression ◽  
White Spruce ◽  
Analysis Data ◽  
Site Index ◽  
Nonlinear Regression Model ◽  
North Central ◽  
Breast Height ◽  
University Of Wisconsin ◽  
Dominant Height

Abstract Site-index (heightߝgrowth) curves, site-index prediction equations, and growth intercepts were developed from internode measurements and stem-analysis data using dominant trees in 69 plots located in white spruce plantations aged 19 to 32 years total age. Site-index curves were based on breast-height (1.3 m) age because our analyses show that height growth below breast height is slow and erratic and is poorly related to site index (dominant height at 15 years breast-height age). The most precise model for computing heightߝgrowth curves was a Newnham constrained polymorphic expression (Newnham, R.M. 1988. A modification of the Ek-Payandeh nonlinear regression model for site-index curves. Can. J. For. Res. 18:115ߝ120) of the Ek nonlinear regression model (Ek, A.R. 1971. A formula for white spruce site-index curves. University of Wisconsin For. Res. Note 161. 2 p). Comparisons showed that site-index curves in North Central Ontario were comparable to site-index curves for white spruce plantations in southeastern Ontario. The first three to five internodes above 2.0 m gave the most precise estimates of site index based on growth intercepts. North. J. Appl. For. 23(4):257–263.

Growth intercepts for estimating site quality of young white spruce plantations in north central Ontario

1987 ◽  
Vol 17 (11) ◽  
pp. 1385-1389 ◽  
Author(s):  
James S. Thrower
Keyword(s):  
Average Length ◽  
White Spruce ◽  
Site Index ◽  
Site Quality ◽  
North Central ◽  
Breast Height

Growth intercepts were used to estimate site index (defined as height of the trees 15 years after breast height (1.3 m) was attained) of dominant, planted white spruce (Piceaglauca (Moench) Voss) in north central Ontario. The growth intercepts were computed using four methods to select internode lengths from series of one through seven internodes, starting at each of eight heights from 0 to 3.0 m. Precision increased rapidly with more internodes and higher starting heights but quickly slowed to only marginal increases. Removing the smallest internode increased precision when growth intercepts started below 1.3 m. Removing the largest and both the smallest and largest internodes reduced precision from all starting heights. The most precise and practical growth intercepts used the average length of the first three, four, and five internodes above 2.0 m, explaining 83, 85, and 89% of the variation in site index, respectively.

Linking juvenile growth of white spruce with site index

2006 ◽  
Vol 82 (6) ◽  
pp. 819-824 ◽  
Author(s):  
Zhili Feng ◽  
Kenneth J Stadt ◽  
Victor J Lieffers ◽  
Shongming Huang
Keyword(s):  
White Spruce ◽  
Analysis Data ◽  
Site Index ◽  
Growth Increment ◽  
Breast Height ◽  
Spruce Stands ◽  
Stand Height ◽  
Using Data ◽  
New Equation ◽  
Mixedwood Stands

The goal of this study was to link the growth of juvenile white spruce stands with an estimate of their site index. We applied a previously developed technique for correcting the height bias created by dominance switching among juvenile trees before trees reached the site index base age (50 years at breast height), using stem analysis data of white spruce from five mixedwood stands in central Alberta. For white spruce of approximately 15 years total age, we found the height of the current top height trees was approximately 14% greater than the height of the top height trees that would be selected close to breast height age 50. This height correction is essential to avoid an overestimate of site index. Secondly, to avoid the difficulties of determining breast height age or growth increment required for juvenile site index determination, we developed a linkage to site index using data from 168 white spruce trees that were longitudinally sectioned along the pith, selected from juvenile (age 6–15) spruce stands. Using this new equation, coupled with the correction for bias, we found that site index for white spruce from 49 test stands in Alberta, ranged from 9.0 to 31.8 m at base age 50, with a mean of 17.8 m; these values are in the range for spruce in mixedwood stands in Alberta. Key words: juvenile stand, height age curve, height bias adjustment, site index

A Multipoint Felled-Tree Validation of Height–Age Modeled Growth Rates

2020 ◽  
Vol 66 (3) ◽  
pp. 275-283 ◽  
Author(s):  
Halli Hemingway ◽  
Mark Kimsey
Keyword(s):  
Growth Rates ◽  
Rocky Mountain ◽  
Site Index ◽  
Douglas Fir ◽  
Alternative Methods ◽  
Forest Site ◽  
Site Productivity ◽  
Site Factors ◽  
Forest Management Planning ◽  
Breast Height

Abstract Accurate measures of forest site productivity are essential for forest-management planning. The most common measure of site productivity is breast height–age site index (BHASI)—the expected height at a reference age. Error from including early growth in productivity estimates and limited applicability of any one BHASI model warrant development of alternative methods. Exploring alternatives may only be necessary if regional BHASI models are not accurately predicting growth rates. We compared modeled height growth rates for Rocky Mountain Douglas-fir (Pseudotsuga menziesii var. glauca) to felled-tree measurements to evaluate relative performance of a regional BHASI model. An orthogonal sampling design ensured samples were collected across a range of site factors known to influence Douglas-fir growth rates. Growth rates for each 10 m section were calculated and compared to BHASI modeled growth rates. The regional BHASI model underpredicted growth rates from breast height to 30 m. Observed growth rates from 10 to 30 m accounted for the majority of underprediction relative to BHASI modeled growth rates. An alternative multipoint method of defining site productivity is described. More research comparing BHASI and alternative methods is needed, given the growth rate error associated with one-point site productivity assessment.

Site Index Curves for Norway Spruce in Southern Ontario1

1989 ◽  
Vol 6 (1) ◽  
pp. 23-26 ◽  
Author(s):  
Andrew M. Gordon ◽  
Peter A. Williams ◽  
Edward P. Taylor
Keyword(s):  
Norway Spruce ◽  
Soil Texture ◽  
Sandy Soils ◽  
Site Index ◽  
Height Growth ◽  
Stem Analysis ◽  
Mean Values ◽  
Breast Height ◽  
Drainage Class ◽  
The Mean

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.

Some climatic aspects of biomass productivity of white spruce stem wood

1987 ◽  
Vol 17 (9) ◽  
pp. 1075-1079 ◽  
Author(s):  
L. A. Jozsa ◽  
J. M. Powell
Keyword(s):  
Boreal Forests ◽  
Biomass Productivity ◽  
White Spruce ◽  
Ice Age ◽  
Stem Wood ◽  
Breast Height ◽  
Sampling Locations ◽  
Tree Ring Data ◽  
Canadian Boreal Forest ◽  
Old Trees

Biomass productivity was determined for white spruce (Piceaglauca (Moench) Voss) in the boreal forests of Alberta, the Northwest Territories, and Manitoba. Comparisons were made between southern and northern locations, between eastern and western transect locations, and between older (200 + years) and younger (110 years) trees. At 13 sampling locations, X-ray densitometric tree ring data were obtained from the base of the stem, breast height, and from five points equidistant along the stem. Markedly higher stem wood biomass productivity was found for the 110-year-old trees than for the 210-year-old trees in Alberta; average ring weights were 3.8 and 1.2 g for the first 100 years of growth in 1 cm thick disks at breast height. These results suggest that climatic warming since the end of the Little Ice Age (ca. 1850) has resulted in higher biomass productivity in the Canadian boreal forest.

scholarly journals Juvenile Height Development in Interior Spruce Stands of British Columbia

2000 ◽  
Vol 15 (3) ◽  
pp. 117-121 ◽  
Author(s):  
Gordon D. Nigh ◽  
Bobby A. Love
Keyword(s):  
Decision Making ◽  
British Columbia ◽  
Site Index ◽  
Timber Supply ◽  
Breast Height ◽  
Forest Region ◽  
Interior Spruce ◽  
Spruce Stands ◽  
Age Model ◽  
Height Model

Abstract Good estimates of juvenile heights are important for silviculture and timber supply decision-making. These height estimates are particularly important for estimating the number of years it takes a stand to reach green-up and breast height. Thirty-nine 0.04 ha plots were established in managed juvenile stands of interior spruce in the Prince Rupert Forest Region. Four sample trees in each plot were split longitudinally and height-age data were obtained from the exposed pith nodes or branch whorls. The height-age data were fit to a combined exponential and power function to create a juvenile height model for interior spruce. This model is a function of age and site index. Years to breast height and green-up age models were developed with data generated from the juvenile height model. Forecasts from these models indicate that the time to reach breast height and green-up age is less than previously expected. The juvenile height model, years to breast height model, and green-up age model should be used for site indices above 14.2 m. In addition, the height model should only be used up to total age 20. West. J. Appl. For. 15(3):117-121.

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