Stem volume models with random coefficients for Pinus kesiya in Tanzania, Zambia, and Zimbabwe

2001 ◽  
Vol 31 (5) ◽  
pp. 879-888 ◽  
Author(s):  
Kalle Eerikäinen
Keyword(s):  
Variable Exponent ◽  
Generalized Least Squares ◽  
General Assumption ◽  
Random Coefficients ◽  
Stem Volume ◽  
Random Parameters ◽  
Pinus Kesiya ◽  
Taper Equation ◽  
Volume Models ◽  
Taper Models

The aim of the study was to estimate stem volume and taper models for Pinus kesiya (Royle ex Gordon). The volume function provides a simple prediction model for the stem volume. Taper models were developed for over- and under-bark diameters. The under-bark taper curve was determined with the variable-exponent taper equation, whereas the over-bark taper curve was derived from the predicted under-bark taper model using the variable-exponent form of the bark-thickness model. Because of the spatial correlation structures of the data, the general assumption of uncorrelated residuals did not hold. In addition, the models were assumed to contain random parameters that vary from stand to stand and from tree to tree. Therefore, the fixed and random parameters of the models were estimated with the generalized least squares technique. The results of the study show that the mixed models for stem volume and taper are more reliable volume and diameter predictors for P. kesiya than earlier taper and volume functions.

scholarly journals Variable-Exponent Taper Equation Based on Multilevel Nonlinear Mixed Effect for Chinese Fir in China

Forests ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 126
Author(s):  
Sensen Zhang ◽  
Jianjun Sun ◽  
Aiguo Duan ◽  
Jianguo Zhang
Keyword(s):  
Variable Exponent ◽  
Southern China ◽  
Information Criteria ◽  
Chinese Fir ◽  
Tree Level ◽  
Mixed Effect ◽  
Basic Model ◽  
Taper Equation ◽  
Taper Equations ◽  
Taper Models

A variable-exponent taper equation was developed for Chinese fir (Cunninghamia lanceolate (Lamb.) Hook.) trees grown in southern China. Thirty taper equations from different groups of models (single, segmented, or variable-exponent taper equation) were compared to find the excellent basic model with S-plus software. The lowest Akaike information criteria (AIC), Bayesian information criteria (BIC), and -2loglikelihood (-2LL) was chosen to determine the best combination of random parameters. Single taper models were found having the lowest precision, and the variable-exponent taper equations had higher precision than the segmented taper equations. Four variable-exponent taper models that developed by Zeng and Liao, Bi, Kozak, Sharma, and Zhang respectively, were selected as basic model and had no difference in fit statistics between them. Compared with the model without seldom parameter, the nonlinear mixed-effects (NLME) model improves the fitting performance. The plot-level NLME model was found not to remove the residual autocorrelation. The tree-level and two-level NLME model had better simulation accuracy than the plot-level NLME model, and there were no significant differences between the tree-level and two-level NLME model. Variable-exponent taper model developed by Kozak showed the best performance while considering two-level or tree-level NLME model, and produced better predictions for medium stems compared to lower and upper stems.

scholarly journals COMPATIBILITY BETWEEN THE SPURR FUNCTION VOLUME AND THE KOZAK’S TAPER FUNCTION AND QUINTIC POLYNOMIAL VOLUMES FOR BLACK WATTLE TREES

FLORESTA ◽  
2021 ◽  
Vol 51 (2) ◽  
pp. 521
Author(s):  
Marcos Behling ◽  
Henrique Soares Koehler ◽  
Alexandre Behling
Keyword(s):  
Stem Volume ◽  
System Of Equations ◽  
Acacia Mearnsii ◽  
Data Set ◽  
Taper Function ◽  
Quintic Polynomial ◽  
Black Wattle ◽  
Taper Equation ◽  
Volume Estimates ◽  
Taper Models

When modeling the taper and volume, it is desired that the volume estimates obtained by using these two methods are compatible, where the total stem volume estimates shall not differ when using a total volume equation and the volume calculated by integrating the taper equation. There are several of such systems proposed in the literature, in which modifications in the volume and taper models were made to obtain compatible systems. This paper introduces an idea to obtain compatibility in a simpler way, without the need to modify the volume and taper models. Thus, the overall objective of this study was to develop and present a procedure to obtain compatibility between the Spurr function volume and the Kozak’s taper function and quintic polynomial volumes for Acacia mearnsii De Wild trees and compare the results to the traditional method of the same system of equations. The procedures proposed were applied on data on the Acacia mearnsii De Wild (black wattle) species in the towns of Cristal, Piratini, and Encruzilhada in the south of the state of Rio Grande do Sul, Brazil. The data set included 343 trees ranging from 5 to 10.75 years of age. The quality of the fitting for the volume and taper equations fitted using procedures 1 and 2 is similar, and both are compatible. The system of equations presented in procedure 2 is simpler to be applied when compared to procedure 1.

scholarly journals Selection of mixed-effects parameters in a variable–exponent taper equation for birch trees in northwestern Spain

2013 ◽  
Vol 70 (7) ◽  
pp. 707-715 ◽  
Author(s):  
Esteban Gómez-García ◽  
Felipe Crecente-Campo ◽  
Ulises Diéguez-Aranda
Keyword(s):  
Variable Exponent ◽  
Mixed Effects ◽  
Birch Trees ◽  
Northwestern Spain ◽  
Taper Equation ◽  
Selection Of

scholarly journals Comprehensive yield model for plantation teak in Panama

Silva Fennica ◽  
2020 ◽  
Vol 54 (5) ◽  
Author(s):  
Petteri Seppänen ◽  
Antti Mäkinen
Keyword(s):  
Input Parameter ◽  
Large Diameter ◽  
Measurement Data ◽  
Growth And Yield ◽  
Tree Level ◽  
Stem Volume ◽  
Yield Model ◽  
Individual Tree ◽  
Support Tool ◽  
Volume Models

The purpose of this study was to prepare a comprehensive, computerized teak ( L.f) plantation yield model system that can be used to describe the forest dynamics, predict growth and yield and support forest planning and decision-making. Extensive individual tree and permanent sample plot data were used to develop tree-level volume models, taper curve models and stand-level yield models for teak plantations in Panama. Tree volume models were satisfactorily validated against independent measurement data and other published models. Tree height as input parameter improved the stem volume model marginally. Stand level yield models produced comparable harvest volumes with models published in the literature. Stand level volume product outputs were found like actual harvests with an exception that the models marginally underestimate the share of logs in very large diameter classes. The kind of comprehensive model developed in this study and implemented in an easy to use software package provides a very powerful decision support tool. Optimal forest management regimes can be found by simulating different planting densities, thinning regimes and final harvest ages. Forest practitioners can apply growth and yield models in the appropriate stand level inventory data and perform long term harvest scheduling at property level or even at an entire timberland portfolio level. Harvest schedules can be optimized using the applicable financial parameters (silviculture costs, harvesting costs, wood prices and discount rates) and constraints (market size and operational capacity).Tectona grandis

scholarly journals Direct Measurement of Trunk Volume in Forest Trees: Focus on White Pine and Comparison to a Statistical Method

2020 ◽  
Author(s):  
Robert T. Leverett ◽  
David N. Ruskin ◽  
Susan A. Masino
Keyword(s):  
Carbon Storage ◽  
Direct Measurement ◽  
State Of The Art ◽  
Forest Trees ◽  
White Pine ◽  
Individual Tree ◽  
Average Value ◽  
Direct Measurement Method ◽  
Volume Models ◽  
Taper Models

AbstractAccurate measurement of tree volume and associated carbon storage are necessary to determine ongoing sequestration as well as site productivity and changes in growth of individual tree species. Standard statistical methods vary their estimations of tree volume, and thus carbon storage and sequestration, particularly in larger, older trees in a forest setting. Here, we describe a detailed direct measurement method that combines traditional trunk taper models with state-of-the-art instrumentation and the best mathematical models for producing more accurate measurements of trunk volume. A stand-grown Eastern White Pine (Pinus strobus) is used as an example; the method is compared with a commonly used statistics-based Forest Service method. This latter method is shown to over- or underestimate volume if the trunk form factor deviates sufficiently from the average value for this species. Direct measurement modeling can be used to validate or choose among existing simple statistical volume models, especially for local applications. It can also assist in widespread recalibration of other standards and models used to estimate volume and carbon storage over time.

scholarly journals Generic and specific stem volume models for three subtropical forest types in southern Brazil

2015 ◽  
Vol 72 (6) ◽  
pp. 865-874 ◽  
Author(s):  
Alexander C. Vibrans ◽  
Paolo Moser ◽  
Laio Z. Oliveira ◽  
João P. de Maçaneiro
Keyword(s):  
Subtropical Forest ◽  
Stem Volume ◽  
Southern Brazil ◽  
Forest Types ◽  
Volume Models

scholarly journals Biomass and Volume Modeling along with Carbon Concentration Variations of Short-Rotation Poplar Plantations

Forests ◽  
2020 ◽  
Vol 11 (7) ◽  
pp. 780 ◽  
Author(s):  
Lihu Dong ◽  
Faris Rafi Almay Widagdo ◽  
Longfei Xie ◽  
Fengri Li
Keyword(s):  
Carbon Sink ◽  
Biomass Conversion ◽  
Model Fitting ◽  
National Forest Inventory ◽  
Model Systems ◽  
Stem Volume ◽  
Crown Length ◽  
Short Rotation ◽  
And Performance ◽  
Volume Models

Short-rotation forestry is of interest to provide biomass for bioenergy and act as a carbon sink to mitigate global warming. The Poplar tree (Populus × xiaohei) is a fast-growing and high-yielding tree species in Northeast China. In this study, a total of 128 Populus × xiaohei trees from the Songnen Plain, Heilongjiang Province, Northeastern China, were harvested. Several available independent variables, such as tree diameter at breast height (D), tree’s total height (H), crown width (CW), and crown length (CL), were differently combined to develop three additive biomass model systems and eight stem volume models for Populus × xiaohei tree. Variance explained within the three additive biomass model systems ranged from 83% to 98%, which was lowest for the foliage models, and highest for the stem biomass models. Similar findings were found in the stem volume models, in which the models explained more than 94% of the variance. The additional predictors, such as H, CL, or CW, evidently enhanced the model fitting and performance for the total and components biomass along with the stem volume models. Furthermore, the biomass conversion and expansion factors (BCEFs) of the root (118.2 kg/m3), stem (380.2 kg/m3), branch (90.7 kg/m3), and foliage (31.2 kg/m3) were also calculated. The carbon concentrations of Populus × xiaohei in root, stem, branch, and foliage components were 45.98%, 47.74%, 48.32%, and 48.46%, respectively. Overall, the newly established models in this study provided complete and comprehensive tools for quantifying the biomass and stem volume of Populus × xiaohei, which might be essential to be specifically utilized in the Chinese National Forest Inventory.

scholarly journals Taper, Volume, and Weight Equations for Red Pine in West Virginia

2008 ◽  
Vol 25 (3) ◽  
pp. 151-153 ◽  
Author(s):  
Lichun Jiang ◽  
John R. Brooks
Keyword(s):  
West Virginia ◽  
Ease Of Use ◽  
Red Pine ◽  
Seemingly Unrelated Regression ◽  
Stem Volume ◽  
West Virginia University ◽  
Individual Tree ◽  
Unrelated Regression ◽  
Taper Equation ◽  
Volume Equations

Abstract Compatible taper, volume, and weight equations were developed for planted red pine in West Virginia. The data were based on stem analysis of 26 trees from West Virginia University Research Forest, located in northern West Virginia. A commonly used segmented polynomial taper equation was chosen because of its balance between prediction accuracy and ease of use. Seemingly unrelated regression was used to simultaneously fit the system of equations for inside and outside bark data. When compared with existing total stem volume equations developed by Fowler (Fowler, G.W., 1997, Individual tree volume equations for red pine in Michigan, North. J. Appl. For. 14:53–58) and by Gilmore et al. (Gilmore, D.W., et al., 2005, Thinning red pine plantations and the Langsaeter hypothesis: A northern Minnesota case study. North, J. Appl. For. 22:19–25), a positive bias was evident that increased directly with stem diameter for trees from this region.

scholarly journals SEMIPARAMETRIC ESTIMATION OF RANDOM COEFFICIENTS IN STRUCTURAL ECONOMIC MODELS

2016 ◽  
Vol 33 (6) ◽  
pp. 1265-1305 ◽  
Author(s):  
Stefan Hoderlein ◽  
Lars Nesheim ◽  
Anna Simoni
Keyword(s):  
General Framework ◽  
Structural Model ◽  
Asymptotic Properties ◽  
Semiparametric Estimation ◽  
Estimation Method ◽  
Structural Models ◽  
Estimation Procedure ◽  
Random Coefficients ◽  
Random Parameters ◽  
Monte Carlo Experiments

This paper discusses nonparametric estimation of the distribution of random coefficients in a structural model that is nonlinear in the random coefficients. We establish that the problem of recovering the probability density function (pdf) of random parameters falls into the class of convexly-constrained inverse problems. The framework offers an estimation method that separates computational solution of the structural model from estimation. We first discuss nonparametric identification. Then, we propose two alternative estimation procedures to estimate the density and derive their asymptotic properties. Our general framework allows us to deal with unobservable nuisance variables, e.g., measurement error, but also covers the case when there are no such nuisance variables. Finally, Monte Carlo experiments for several structural models are provided which illustrate the performance of our estimation procedure.

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