Modeling of eucalyptus tree stem taper in mixed production systems

Abstract This study aims to evaluate the robustness of parametric and nonparametric procedures using alternative definitions of validation data for loblolly pine. Specifically, four data division strategies were implemented: random selection of one-third of the trees in the data set, selection of the smallest one-third of the trees by diameter at breast height (DBH), selection of the middle third of the trees by DBH, and selection of the largest third of the trees by DBH. Results indicate that tree taper was predicted reasonably well by both procedures when the smallest, medium-sized, or randomly selected trees were withheld for validation. However, when the largest trees were withheld for validation, diameters predicted by the nonparametric random forest algorithm were considerably less accurate than those predicted by the parametric models, especially for diameters near the tree top. When extrapolation is anticipated, a carefully designed data-partitioning strategy should provide some protection against poor results for given prediction objectives. Study Implications Parametric tree-stem taper models have been widely applied in forestry. Recently, nonparametric methods with computationally intensive algorithms were proposed for estimating tree taper, but reliability of the methods has not been explicitly examined. In practice, models are commonly applied to predict unknown populations, which may vary from the observations used in model development. This study provides insights for natural resource and forest managers to select appropriate validation procedures when developing models for predicting tree-stem taper and examining robustness of parametric and nonparametric fitting of tree-stem taper under varying levels of interpolation/extrapolation from fitting to validation of data.

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Ozolinši tüvemoodustaja matemaatiline analüüs ja modifitseerimise võimalused Hiiumaa männikute näitel

Forestry Studies / Metsanduslikud Uurimused ◽

10.2478/fsmu-2020-0004 ◽

2020 ◽

Vol 72 (1) ◽

pp. 34-53

Author(s):

Allar Padari

Keyword(s):

Pinus Sylvestris ◽

Stem Volume ◽

Accurate Assessment ◽

Forest Reserve ◽

Breast Height ◽

Stem Taper ◽

Curve Equation ◽

Root Collar ◽

Lateral Area ◽

Tree Stem

AbstractThis paper discloses algorithms for calculating the volume and lateral area of a stem or part of the stem (assortment) using the integral of the Ozolinš’ stem taper curve. An algorithm was also developed to change the taper curve constants in case another diameter was measured higher than the breast height. The experiment was performed with 580 Scots pines (Pinus Sylvestris L.) measured in Hiiumaa, which included height, diameter at breast height and diameter from the root collar at a height of 5 m. The volumes of tree stem and assortments were estimated with both – the original and corrected (with the measured additional diameter) Ozolinš’ taper curve. Using the original Ozolinš’ taper curve, the stem volume of pines in Hiiumaa is estimated at 4% higher according to the analysis results of 580 measured trees. In the case of Hiiumaa Scots pines (Pinus Sylvestris L.), it is recommended to use 119.717, −289.805 and 1152.016 as the values of the coefficients a0, a1 and a2, respectively, of the Ozolinš’ taper curve equation. In conclusion, for a more accurate assessment of the forest reserve, it is recommended to measure one additional diameter at 5 to 8 m above the root collar on some or all trees.

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Borehole Oleoresin Production from Slash Pine

Southern Journal of Applied Forestry ◽

10.1093/sjaf/21.3.108 ◽

1997 ◽

Vol 21 (3) ◽

pp. 108-115 ◽

Cited By ~ 5

Author(s):

Alan W. Hodges ◽

Jon D. Johnson

Keyword(s):

Labor Productivity ◽

Production Systems ◽

Insect Pest ◽

Basal Area ◽

Pinus Palustris ◽

Pinus Elliottii ◽

Slash Pine ◽

Stem Size ◽

Resin Duct ◽

Tree Stem

Abstract A process is described for production of oleoresin from borehole wounds to the xylem in slash pine (Pinus elliottii Engelm. var. elliottii). Advantages of this process over conventional oleoresin production methods include higher labor productivity, improved product quality, reduced tree damage and stress, and reduced insect pest problems. In experiments conducted in Florida and Georgia from 1991 to 1994, oleoresin yields averaged 657 g (1.45 lb) per borehole, or nearly 1.7 kg (3.7 lb) per tree with multiple boreholes. Tests of other species used commercially for oleoresin production, including longleaf pine (Pinus palustris Mill.), produced substantially lower yields. Borehole oleoresin yields were very sensitive to tree stem size, reflecting the capacity of preformed oleoresin stored in the resin duct system. Yields were significantly affected by treatment manipulations of borehole diameter, depth, number, spacing, orientation, chemical stimulants, and collection container type. Oleoresin flow was highest during the midsummer period and continued over a period of several months. Oleoresin flow potential was related to the percentage of tree stem basal area tapped. For optimal treatments affecting 35 to 40% of tree basal area, predicted yields ranged from 1.52 to 3.10 kg (3.35 to 6.83 lb) for trees 23 to 37 cm (9 to 14.5 in.) dbh, respectively. Tree growth rates were not measurably altered by borehole treatment. Comparisons with conventional bark-chipping oleoresin production systems in slash pine showed that the borehole system achieves a labor productivity two times greater than the best alternative, but sacrifices overall yields per tree. The borehole method offers new opportunities for utilization of the slash pine resource and an additional economic enterprise for forest lands. South. J. Appl. For. 21(3):108-115.

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An integrated approach to individual tree volume distribution and stem profile modeling

Canadian Journal of Forest Research ◽

10.1139/x85-091 ◽

1985 ◽

Vol 15 (3) ◽

pp. 555-560 ◽

Cited By ~ 1

Author(s):

James D. Newberry ◽

Thomas E. Burk

Keyword(s):

Conditional Distribution ◽

Volume Ratio ◽

Integrated Approach ◽

Bivariate Distribution ◽

Volume Distribution ◽

Individual Tree ◽

Stem Taper ◽

Error Analyses ◽

Tree Stem ◽

Taper Model

Individual tree merchantable volume – total volume ratios with respect to stem diameters and heights on the tree stem were described with the SB distribution. Different volume ratio estimates were obtained from these models for a given location on the tree stem depending on whether the location is indexed by a diameter or height. This problem is common with many volume ratio systems. To overcome this problem, the merchantable volume – total volume ratios with respect to joint stem diameters and heights were described with the SBB bivariate distribution. Error analyses showed that the bivariate distribution had less error than the marginal SB distribution for stem diameters, but more error than the marginal SB distribution for stem heights. A stem taper model was obtained from the conditional distribution of diameter given height using the median regression.

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Representation of Tree Stem Taper Curves and Their Dynamic, Using a Linear Model and the Centroaffine Transformation

Journal of Forest Research ◽

10.1007/bf02760304 ◽

1998 ◽

Vol 3 (2) ◽

pp. 67-74 ◽

Cited By ~ 7

Author(s):

Dieter Gaffrey ◽

Branislav Sloboda ◽

Naoto Matsumura

Keyword(s):

Linear Model ◽

Stem Taper ◽

Tree Stem

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Covariance Generalized Linear Models: An Approach for Quantifying Uncertainty in Tree Stem Taper Modeling

Forest Science ◽

10.1093/forsci/fxab037 ◽

2021 ◽

Author(s):

Luan Demarco Fiorentin ◽

Wagner Hugo Bonat ◽

Allan Libanio Pelissari ◽

Sebastião do Amaral Machado ◽

Saulo Jorge Téo

Keyword(s):

Covariance Matrix ◽

Confidence Intervals ◽

Generalized Linear Models ◽

Linear Models ◽

Mixed Effect Model ◽

Mixed Effect ◽

Stem Taper ◽

Effect Model ◽

The Mean ◽

Tree Stem

Abstract A natural dependence among diameters measured within-tree is expected in taper data due to the hierarchical structure. The aim of this paper was to introduce the covariance generalized linear model (CGLM) framework in the context of forest biometrics for Pinus taeda stem form modeling. The CGLMs are based on marginal specification, which requires a definition of the mean and covariance components. The tree stem mean profiles were modeled by a nonlinear segmented model. The covariance matrix was built considering four strategies of linear combinations of known matrices, which expressed the variance or correlations among observations. The first strategy modeled only the variance of the diameters over the stem as a function of covariates, the second modeled correlation among observations, the third was defined based on a random walk model, the fourth was based on a structure similar to a mixed-effect model with a marginal specification, and the fourth was a traditional mixed-effect model. Mean squared error and bias showed that the approaches were similar for describing the mean profile for fitting and validation dataset. However, uncertainties expressed by confidence intervals of the relative diameters were significant and related to the matrix covariance structures of the CGLMs. Study Implications: We proposed stem taper modeling based on a new class of statistical models. Covariance generalized linear models allow quantification of the stem dynamic by using a nonlinear model. Uncertainty estimates are performed on a covariance matrix given by a linear combination of known matrices. The matrices enable modeling of the nonconstant variance as well as the several correlation patterns, resulting in a framework more flexible and robust than traditional approaches usually applied for stem taper modeling. For practical purposes, uncertainty modeling can improve forest management planning, because the production limits by timber assortments are more reliable due to the confidence intervals derived from an appropriate uncertainty analysis.

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