scholarly journals Diameter distribution model development of tropical hybrid Eucalyptus clonal plantations in Sumatera, Indonesia: A comparison of estimation methods

2022 ◽  
Vol 52 ◽  
Author(s):  
Joni Waldy ◽  
John A. Kershaw Jr ◽  
Aaron Weiskittel ◽  
Mark J. Ducey
Keyword(s):  
Growth And Yield ◽  
Estimation Methods ◽  
Hybrid Clone ◽  
Distribution Model ◽  
Diameter Distribution ◽  
Average Growth ◽  
Eucalyptus Hybrid ◽  
Stand Attributes ◽  
The Moment ◽  
Diameter Distributions

Background: Effective forest management and planning often requires information about the distribution of volume by size and product classes. Size-class models describe the diameter distribution and provide information by diameter class, such as the number of trees, basal area, and volume per unit of area. A successful diameter-distribution model requires high flexibility yet robust prediction of its parameters. To our knowledge, there are no studies regarding diameter distribution models for Eucalyptus hybrids in Indonesia. Therefore, the aim of this study was to compare different recovery methods for predicting parameters of the 3-parameter Weibull distribution for characterising diameter distributions of Eucalyptus hybrid clone plantations, on Sumatera Island of Indonesia. Methods: The parameter recovery approach was proposed to be compatible with stand-average growth and yield models developed based on the same data. Three approaches where compared: moment-based recovery, percentile-based prediction and hybrid methods. The ultimate goal was to recover Weibull parameters from future stand attributes, which were predicted from current stand attributes using regression models. Results: In this study, the moment method was found to give the overall lowest mean error-index and Kolmogorov– Smirnov (KS) statistic, followed by the hybrid and percentile methods. The moment-based method better fit long tails on both sides of the distribution and exhibited slightly greater flexibility in describing plots with larger variance than the other methods. Conclusions: The Weibull approach appeared relatively robust in determining diameter distributions of Eucalyptus hybrid clone plantation in Indonesia, yet some refinements may be necessary to characterize more complex distributions.

scholarly journals A percentile-based estimator for the log-logistic function: Application to forestry

2020 ◽  
Vol 72 (1) ◽  
pp. 107-120
Author(s):  
Friday Nwabueze Ogana
Keyword(s):  
Estimation Method ◽  
Tectona Grandis ◽  
Logistic Function ◽  
Growth And Yield ◽  
Estimation Methods ◽  
Diameter Distribution ◽  
Logistic Distribution ◽  
Forest Stands ◽  
Forest Modelling ◽  
Diameter Distributions

AbstractDeveloping a simplified estimation method without compromising the performance of the distribution is germane to forest modelling. Few estimation methods exist for the Log-Logistic distribution and are relatively complex. A simplified estimator for the Log-Logistic parameters will increase its application in diameter distribution yield systems. Therefore, in this study, a percentile-based estimator was applied for the Log-Logistic distribution. The Kolmogorov-Smirnov, Anderson-Darling and Cramer-von Mises statistics were used to evaluate the method in two natural forest stands and two monospecific plantations of Gmelina arborea Roxb. and Tectona grandis Linn. f. in Nigeria. The parameter recovery model (PRM) and parameter prediction model (PPM) were used to predict the diameter distributions of independent stands of G. arborea and T. grandis. The results showed that the percentile estimator did not compromise the quality of fits of the Log-Logistic function across the four forest stands and are comparable to the maximum likelihood estimator. The 25th and 75th, and 40th and 80th were the best sample percentiles for the estimator. The predicted diameter distributions of G. arborea and T. grandis stands from the PRM and PPM were reasonable and compare well with the observed distribution. Thus, either of the models can be incorporated into the growth and yield system of forest stand management.

A Blind Spot in the Use of the Weibull Function for Modeling Diameter Distributions

2020 ◽  
Author(s):  
Adrian Norman Goodwin
Keyword(s):  
Lower Bound ◽  
Blind Spot ◽  
Forest Growth ◽  
Growth And Yield ◽  
Diameter Distribution ◽  
Absolute Difference ◽  
Weibull Function ◽  
Distribution Models ◽  
Difference Statistic ◽  
Diameter Distributions

Abstract Diameter distribution models based on probability density functions are integral to many forest growth and yield systems, where they are used to estimate product volumes within diameter classes. The three-parameter Weibull function with a constrained nonnegative lower bound is commonly used because of its flexibility and ease of fitting. This study compared Weibull and reverse Weibull functions with and without a lower bound constraint and left-hand truncation, across three large unthinned plantation cohorts in which 81% of plots had negatively skewed diameter distributions. Near-optimal lower bounds for the unconstrained Weibull function were negative for negatively skewed data, and the left-truncated Weibull using these bounds was 14.2% more accurate than the constrained Weibull, based on the Kolmogorov-Smirnov statistic. The truncated reverse Weibull fit dominant tree distributions 23.7% more accurately than the constrained Weibull, based on a mean absolute difference statistic. This work indicates that a blind spot may have developed in plantation growth modeling systems deploying constrained Weibull functions, and that left-truncation of unconstrained functions could substantially improve model accuracy for negatively skewed distributions.

Deriving Tree Diameter Growth and Probability of Survival Equations from Successive Diameter Distributions

2008 ◽  
Vol 54 (1) ◽  
pp. 31-35
Author(s):  
Thomas G. Matney ◽  
Emily B. Schultz
Keyword(s):  
General Procedure ◽  
Growth And Yield ◽  
Diameter Distribution ◽  
Diameter Growth ◽  
Individual Tree ◽  
Statistical Probability ◽  
Growth And Survival ◽  
Tree Diameter ◽  
Growth And Yield Models ◽  
Diameter Distributions

Abstract Many growth and yield models have used statistical probability distributions to estimate the diameter distribution of a stand at any age. Equations for approximating individual tree diameter growth and survival probabilities from dbh can be derived from these models. A general procedure for determining the functions is discussed and illustrated using a loblolly pine spacing study. The results from the spacing study show that it is possible to define tree diameter growth and survival probability functions from diameter distributions with an accuracy sufficient to obtain a link between the individual tree and diameter growth and yield models.

On the use of the Weibull distribution in modeling and describing diameter distributions of clonal eucalypt stands

2020 ◽  
Vol 50 (10) ◽  
pp. 1050-1063 ◽  
Author(s):  
Luciane Naimeke Schmidt ◽  
Mateus Niroh Inoue Sanquetta ◽  
John Paul McTague ◽  
Gilson Fernandes da Silva ◽  
Clayton Vieira Fraga Filho ◽  
...  
Keyword(s):  
Weibull Distribution ◽  
Goodness Of Fit ◽  
Cumulative Distribution ◽  
Growth And Yield ◽  
Likelihood Method ◽  
Weibull Distributions ◽  
Recovery Method ◽  
Stand Attributes ◽  
Parameter Prediction ◽  
Diameter Distributions

Weibull distributions have been widely used to describe tree stem diameter distributions. However, there is a scarcity of studies that suggest the best Weibull formulation. The parameters of the Weibull distribution are usually predicted by either the parameter prediction method (PPM) or the parameter recovery method (PRM), although other methods have been proposed. Thus, this study aimed to evaluate the performance of eight Weibull formulations and compare methods of parameter prediction to describe diameter distributions of clonal eucalypt stands in Brazil. Data originated from remeasurements of 56 plots at ages 3, 5, and 6 years. Weibull distributions were fitted using the maximum likelihood method and evaluated in a goodness-of-fit indicators ranking. The right-truncated two-parameter formulation showed the best results and was used to evaluate the methods of parameter prediction. Stand attributes showed a strong relationship with shape and scale parameters. Regression models were developed and resulted in accurate estimates using PPM. PRM used a growth and yield system to estimate the stand attributes, followed by the moment-based method. The modified cumulative distribution function regression (CDFR) approach was also evaluated, and it presented the poorest results. Although the PPM showed excellent results, PRM is recommended in older stands with inventory because it implicitly promotes compatibility among stand attributes.

scholarly journals A New Diameter Distribution Model for Unmanaged Loblolly Pine Plantations in East Texas

2006 ◽  
Vol 30 (1) ◽  
pp. 13-20 ◽  
Author(s):  
Young-Jin Lee ◽  
Dean W. Coble
Keyword(s):  
Loblolly Pine ◽  
Pine Plantations ◽  
Growth And Yield ◽  
Distribution Model ◽  
Diameter Distribution ◽  
Yield Prediction ◽  
East Texas ◽  
Distribution Models ◽  
Parameter Recovery ◽  
Diameter Classes

Abstract A parameter recovery procedure for the Weibull distribution function based on four percentile equations was used to develop a diameter distribution yield prediction model for unmanaged loblolly pine (Pinus taeda L.) plantations in East Texas. This model was compared with the diameter distribution models of Lenhart and Knowe, which have been used in East Texas. All three models were evaluated with independent observed data. The model developed in this study performed better than the other two models in prediction of trees per acre and cubic-foot volume per acre (wood and bark, excluding stump) across diameter classes. Lenhart’s model consistently underestimated the larger-diameter classes because it was developed originally with data mostly collected in young plantations. Knowe’s model overestimated volume in sawtimber-sized trees, which could lead to overestimations of volume in older loblolly pine plantations found in East Texas. An example also is provided to show users how to use this new yield prediction system. These results support the recommendation that forest managers should use growth and yield models designed and/or calibrated for the region in which they are implemented.South. J. Appl.For. 30(1):13–20.

Calibrating predicted diameter distribution with additional information in growth and yield predictions

2003 ◽  
Vol 33 (3) ◽  
pp. 430-434 ◽  
Author(s):  
Annika Kangas ◽  
Matti Maltamo
Keyword(s):  
Growth Models ◽  
Basal Area ◽  
Growth And Yield ◽  
Diameter Distribution ◽  
Individual Tree ◽  
Forest Management Planning ◽  
Growing Stock ◽  
Additional Information ◽  
Tree Models ◽  
Diameter Distributions

Diameter distribution of the growing stock is essential in many forest management planning problems. The diameter distribution is the basis for predicting, for example, timber assortments of a stand. Usually the predicted diameter distribution is scaled so that the stem number (or basal area) corresponds to the measured value (or predicted future value), but it may be difficult to obtain a distribution that gives correct estimates for all known variables. Diameter distributions that are compatible with all available information can be obtained using an approach adopted from sampling theory, the calibration estimation. In calibration estimation, the original predicted frequencies are modified so that they respect a set of constraints, the calibration equations. In this paper, an example of utilizing diameter distributions in growth and yield predictions is presented. The example is based on individual tree growth models of Scots pine (Pinus sylvestris L.). Calibration estimation was utilized in predicting the diameter distribution at the beginning of the simulation period. Then, trees were picked from the distribution and their development was predicted with individual tree models. In predicting the current stand characteristics, calibrated diameter distributions proved to be efficient. However, in predicting future yields, calibration estimation did not significantly improve the accuracy of the results.

Some observations on fitting assumed diameter distributions to horizontal point sampling data

2000 ◽  
Vol 30 (4) ◽  
pp. 521-533 ◽  
Author(s):  
Jeffrey H Gove
Keyword(s):  
Diameter Distribution ◽  
Parameter Estimates ◽  
Sample Point ◽  
Underlying Distribution ◽  
Weighted Distribution ◽  
Reliable Parameter ◽  
Simulation Results ◽  
Larger Sample ◽  
Horizontal Point Sampling ◽  
Diameter Distributions

This paper revisits the link between assumed diameter distributions arising from horizontal point samples and their unbiased stand-based representation through weighted distribution theory. Examples are presented, which show that the assumption of a common shared parameter set between these two distributional forms, while theoretically valid, may not be reasonable in many operational cases. Simulation results are presented, which relate the conformity (or lack thereof) in these estimates to sampling intensity per point and the underlying shape of the population diameter distribution from which the sample point was drawn. In general, larger sample sizes per point are required to yield reliable parameter estimates than are generally taken for inventory purposes. In addition, a complimentary finding suggests that the more positively skewed the underlying distribution, the more trees per point are required for good parameter estimates.

Comparison of two parameter recovery methods for the transformation of Pinus sylvestris yield tables into a diameter distribution model

2021 ◽  
Vol 78 (1) ◽  
Author(s):  
Francisco Mauro ◽  
Antonio García-Abril ◽  
Esperanza Ayuga-Téllez ◽  
Alberto Rojo-Alboreca ◽  
Ruben Valbuena ◽  
...  
Keyword(s):  
Pinus Sylvestris ◽  
Distribution Model ◽  
Diameter Distribution ◽  
Parameter Recovery ◽  
Two Parameter ◽  
Recovery Methods

Selective Synthesis of Single-Walled Carbon Nanotubes by Blending Catalysts

2007 ◽  
Author(s):  
Shuhei Inoue ◽  
Takeshi Nakajima ◽  
Kazuya Nomura ◽  
Yoshihiro Kikuchi
Keyword(s):  
Carbon Nanotubes ◽  
Fermi Level ◽  
Chemical Vapor ◽  
Single Walled Carbon Nanotubes ◽  
Diameter Distribution ◽  
Efficient Catalyst ◽  
Single Walled Carbon ◽  
Similar Density ◽  
Walled Carbon Nanotubes ◽  
Diameter Distributions

Single-walled carbon nanotubes are considered the most attractive material and a lot of synthesis processes are developed. Among these synthesis processes chemical vapor deposition processes are considered to be most suitable for macroscopic production. In many CVD processes the alcohol catalytic CVD process can be the best process because it can produce very pure nanotubes without any purification. However, cobalt is essential as a catalyst that makes the flexibility of catalysts restricted. In this paper, our investigation mainly focused on as follows: The efficiency of combined catalysts with/without cobalt. The diameter distributions against catalysts density. The electrical states of catalysts near Fermi level. Consequently, almost all of cobalt containing catalysts worked well, and the diameter distributions were proportional to the particle size. Efficient catalysts had enough states around Fermi level and the cobalt-less efficient catalyst cluster model showed the similar density of state to the cobalt cluster. Thus, noticing to the DOS, other efficient catalysts can be discovered and the diameter distribution will be controllable by adjusting temperature, a catalyst size, and a catalyst combination without any complicated techniques and facilities.

scholarly journals GROWTH AND YIELD OF Shorea parvifolia PLANTED UNDER AKASIA PLANTS IN KAPUAS, CENTRAL KALIMANTAN

2016 ◽  
Vol 7 (3) ◽  
pp. S48-S49
Author(s):  
Wahyudi .
Keyword(s):  
Native Species ◽  
Research Result ◽  
Volume Growth ◽  
Acacia Mangium ◽  
Average Diameter ◽  
Growth And Yield ◽  
Central Kalimantan ◽  
Enrichment Planting ◽  
The Moment ◽  
Silvicultural System

Shorea parvifolia is the native species of Kalimantan and has a high commercial value. This research was aimed to analysis the growth and yield of meranti planted under Acacia mangium stands, as enrichment planting on the TPTI silvicultural system.  The research was conducted at Kapuas District, Central Kalimantan Province. Type of soil at the site is ultisol with 2 606 mm/year of precipitation average.  Initially, Acacia mangium planted with space namely 3 x 3 m at 1993. After two years, seedlings of Shorea parvifolia were planted among akasia plants with 1 111 tress/ha of density.  Thinning of akasia plants were conducted stage by stage, especially at the stunted plants or dead. The data were latest analyzed at 2014 or at the moment of 20 years old.  Research result showed that at the 1, 5, 10, 15, and 15 years old, life percentage of Shorea parvifolia are 94.8%, 78%, 66.4%, 57.5%, and 53% respectively. Average diameter of Shorea parvifolia at the same times are 1.27 cm, 6.13 cm, 12.8 cm, 19.86, and 27.46 cm respectively, and their average total height are 1.51 m, 5.27 m, 10.89 m, 17.18 m, and 24.41 m respectively. Volume growth of Shorea parvifolia at the same times namely 0.05 m3/ha , 3.97 m3/ha, 36.93 m3/ha, 145.44 m3/ha, and 303.62 m3/ha respectively.Key words: growth and yield, CAI, MAI, Shorea parvifolia.

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