Improving growth and yield estimates with a process model derived growth index

2004 ◽  
Vol 34 (6) ◽  
pp. 1274-1282 ◽  
Author(s):  
Jason G Henning ◽  
Thomas E Burk
Keyword(s):  
Process Model ◽  
Environmental Variability ◽  
Growth Index ◽  
Process Models ◽  
Growth And Yield ◽  
Yield Model ◽  
Forest Inventories ◽  
Model Predictions ◽  
Growth And Yield Models ◽  
Empirical Growth

Forest managers have long made use of the regular and predictable nature of tree growth by using empirical growth and yield models to update forest inventories. Updated inventories support better decision making without requiring on the ground reassessment of the forest resource. Growth and yield model predictions can suffer from inaccuracies due to the influence of climate and environmental variability on the growth of trees. Researchers have been attempting to assess and predict the effect of this variation by developing mechanistic process models that often do not generate outputs applicable to inventory update. Here we create a growth index dependent on process model outputs to improve growth and yield estimates. Estimate accuracy was modestly improved over the basic growth and yield estimates and was comparable to previous efforts to account for environmental variability in growth and yield estimates. Using a process model we are nominally considering the entire environment, and by adjusting the growth and yield estimates external to both model types we have avoided difficulties involved with refitting or recreating either model. These are key differences from previous efforts to include environmental variability in growth and yield estimates.

A simple growth and yield model for assessing changes in standing volume across Canada’s forests

2009 ◽  
Vol 85 (1) ◽  
pp. 57-64 ◽  
Author(s):  
C -H. Ung ◽  
P Y Bernier ◽  
X J Guo ◽  
M -C. Lambert
Keyword(s):  
Predictive Power ◽  
Robust Regression ◽  
Forest Growth ◽  
Growth Potential ◽  
Growth And Yield ◽  
Stand Age ◽  
Yield Model ◽  
Wood Volume ◽  
National Model ◽  
Growth And Yield Models

We have adjusted two growth and yield models to temporary sample plots from across Canada, and used climate variables in lieu of phytometric indices such as site index to represent, in part, the site-level variability in growth potential. Comparison of predicted increments in plot-level height, basal area and merchantable wood volume to increments of these variables measured in permanent sample plots shows a moderate to poor predictive ability. Comparison with the performance of four operational growth and yield models from different provinces across Canada shows comparable predictive power of this new model versus that of the provincial models. Based on these results, we suggest that the simplification of regional growth and yield models may be achieved without further loss of predictive power, and that the large error in the prediction of growth increment is mostly associated with the use of temporary sample plots which, by definition, contain little information on stand dynamics. We also suggest that, because of the empirical nature of these growth and yield models, the scale of application should determine the appropriate scale of the model. National estimates of forest growth are therefore less likely to be biased if obtained from a national model only than if obtained from a combination of regional models, where those exist, gap-filled with estimates from a national model. Key words: yield model, merchantable wood volume, stand age, climatic variables, simultaneous regression, robust regression

A compatible growth and yield model for the management of mixed tropical rain forest

2000 ◽  
Vol 30 (2) ◽  
pp. 311-323 ◽  
Author(s):  
James Atta-Boateng ◽  
John William Moser, Jr.
Keyword(s):  
Forest Management ◽  
Rain Forest ◽  
Sustainable Use ◽  
Rate Of Change ◽  
Growth And Yield ◽  
Timber Species ◽  
Yield Model ◽  
Financial Investment ◽  
The Impact ◽  
Growth And Yield Models

The lack of appropriate analytical tools to evaluate the impact of forest management policies has hindered the sustainable use of the rain forest. Decisions about the level of forest management and financial investment require accurate predictions of future forest yields. A technique, using hierarchical clustering and canonical discriminant procedures, was developed previously to pool 112 timber species with similar growth increment characteristics into seven groups suitable for the construction of growth and yield models. Compatible growth and yield models were developed for each group by the solution of a system of differential equations expressing the rate of change of ingrowth, mortality, and survival growth components within a forest stand. The solution provides the means to project the status of the timber stand at any future time given some predefined initial stand conditions. The models are useful for inventory updating, allowable annual cut calculations, and management planning for natural or managed stands. They also provide a means to test hypotheses concerning the influence of stand characteristics on increment and to project future product assortments.

scholarly journals Development of height to crown base models for thirteen tree species of the North American Acadian Region

2012 ◽  
Vol 88 (1) ◽  
pp. 60-73 ◽  
Author(s):  
Baburam Rijal ◽  
Aaron R. Weiskittel ◽  
John A. Kershaw
Keyword(s):  
Tree Species ◽  
Basal Area ◽  
Logistic Equation ◽  
Growth And Yield ◽  
Suitable Model ◽  
Breast Height ◽  
The North ◽  
Model Predictions ◽  
Important Input ◽  
Growth And Yield Models

Height to live crown base (HCB) is an important input variable for several growth and yield models. Since HCB is rarely measured in the field, it is often predicted using static models. Instead of predicting HCB, the Forest Vegetation Simulator Northeastern Variant (FVS-NE) uses an equation that predicts crown ratio (CR), which has not been well validated. The main goal of the present study was to construct a regional HCB model for thirteen selected tree species of the Acadian Region of North America. The specific objectives were to: 1) evaluate FVS-NE model predictions, 2) compare suitable model forms, and 3) assess influence of various covariates to improve predictions. We evaluated three model forms, namely Holdaway (1986), logistic, and exponential. The findings indicated that FVS-NE models were significantly biased for all species as the overall mean bias and root mean square error (RMSE) were 0.11 m and 1.80 m, respectively. A logistic equation with size (diameter at breast height [DBH], total height [HT] and ratio of DBH to HT), and competition (crown competition factor [CCF] and basal area larger than subject tree [BAL]) gave the best predictions for all species in this analysis. This model had an overall mean bias <0.01 m and an RMSE of 1.59 m, which represents a significant improvement in predictions compared to FVS-NE. Despite the range of species and observed variation in the data, the equations worked well and can be easily calibrated to new stands with a few local observations.

scholarly journals A preliminary growth and yield model for Eucalyptus globoidea Blakely plantations in New Zealand

2020 ◽  
Vol 50 ◽  
Author(s):  
Serajis Salekin ◽  
Euan G. Mason ◽  
Justin Morgenroth ◽  
Dean F. Meason
Keyword(s):  
New Zealand ◽  
Basal Area ◽  
Growth And Yield ◽  
Maximum Diameter ◽  
Forest Industry ◽  
Eucalyptus Species ◽  
Plantation Forest ◽  
Yield Model ◽  
Growth And Yield Model ◽  
Growth And Yield Models

Background: New Zealand’s plantation forest industry is dominated by the exotic species radiata pine (Pinus radiata D.Don), which comprises approximately 90% of the net stocked area. However, there is interest in introducing new species to: (a) provide wood that is naturally decay-resistant as a substitute for wood treated with preservatives; (b) match species to the wide variety of environmental conditions in New Zealand; and (c) reduce reliance on P. radiata. Some Eucalyptus species are considered as potential alternatives to P. radiata, specifically those that can survive in resource-limited conditions and produce high quality wood. While Eucalyptus species are grown in plantations in many regions of the world, limited information is available on their growth in New Zealand. Eucalyptus globoidea Blakley is of particular interest and has been planted in trials throughout New Zealand. A complete set of preliminary growth and yield models for this species will satisfy the initial information requirements for diversifying New Zealand’s plantation forest industry. Methods: A set of growth and yield models was developed and validated, based on data from 29 E. globoidea permanent sample plots (PSPs) located mostly in North Island and a few in South Island of New Zealand. Trees were measured at different time intervals in these plots, with height and diameter at breast height (DBH) ranging from 0.1–39.8 m and 0.1–62.3 cm, respectively. An algebraic difference approach (ADA) was applied to model mean top height, basal area, maximum diameter, and standard deviation of DBH. Non-linear regression equations were used to project stand volume and height-diameter relationship, and Reineke’s stand density index (SDI) approach was employed to model mortality. Results: Mean top height, maximum diameter, and standard deviation of DBH were best fitted by Von Bertalanffy-Richards (SE=1.1 m), Hossfeld (SE=2.4 cm), and Schumacher polymorphic (SE=1.6 cm) difference equations, respectively. Basal area data were modelled with high precision (SE=6.9 m2 ha-1) by the Schumacher anamorphic difference equation. Reineke’s SDI approach was able to explain the self-thinning as a reduction in the number of stems per hectare. Stand-level volume per hectare and height-diameter relationship models were precise when including site-specific variables with standard errors of 40.5 m3 ha-1 and 3.1 m, respectively. Conclusion: This study presents a set of preliminary growth and yield models for E. globoidea to project plot-level growth attributes. The models were path invariant and satisfied basic traditional mensurational-statistical growth and yield model assumptions. These models will provide forest growers and managers with important fundamental information about the growth and yield of E. globoidea.

Politikvermittlung an der Schnittstelle von Unterhaltung und Information : Political communication at the interface of entertainment and information

SPIEL ◽  
2019 ◽  
Vol 4 (1) ◽  
pp. 121-145
Author(s):  
Larissa Leonhard ◽  
Anne Bartsch ◽  
Frank M. Schneider
Keyword(s):  
Information Processing ◽  
Political Participation ◽  
Knowledge Acquisition ◽  
Political Communication ◽  
Information Seeking ◽  
Process Model ◽  
Political Information ◽  
Process Models ◽  
Dual Process ◽  
Dual Process Model

This article presents an extended dual-process model of entertainment effects on political information processing and engagement. We suggest that entertainment consumption can either be driven by hedonic, escapist motivations that are associated with a superficial mode of information processing, or by eudaimonic, truth-seeking motivations that prompt more elaborate forms of information processing. This framework offers substantial extensions to existing dual-process models of entertainment by conceptualizing the effects of entertainment on active and reflective forms of information seeking, knowledge acquisition and political participation.

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.

A Growth and Yield Model for Improved Eastern Cottonwood Plantations in the Lower Mississippi Delta

1991 ◽  
Vol 15 (4) ◽  
pp. 213-216 ◽  
Author(s):  
Quang V. Cao ◽  
Kenneth M. Durand
Keyword(s):  
Populus Deltoides ◽  
Mississippi Delta ◽  
Basal Area ◽  
Site Index ◽  
Growth And Yield ◽  
Annual Increment ◽  
Yield Model ◽  
Eastern Cottonwood ◽  
Volume Yield ◽  
Growth And Yield Model

Abstract A compatible growth and yield model was developed based on remeasurement data collected from 183 plots on unthinned improved eastern cottonwood (Populus deltoides Bartr.) plantations in the lower Mississippi Delta. The Sullivan and Clutter (1972) equation form was selected for predicting cubic-foot volume yield and projecting volume from site index and initial age and basal area. Yield equations explained 97% and 94%, respectively, of the variations in total outside bark and merchantable inside bark volumes. Mean annual increment of merchantable volume culminated between 8 and 15 years, depending on site index and initial basal area. South. J. Appl. For. 15(4):213-216.

Toward Metamodels for Composable and Reusable Additive Manufacturing Process Models

2014 ◽  
Vol 136 (6) ◽  
Author(s):  
Paul Witherell ◽  
Shaw Feng ◽  
Timothy W. Simpson ◽  
David B. Saint John ◽  
Pan Michaleris ◽  
...  
Keyword(s):  
Additive Manufacturing ◽  
Metal Powder ◽  
Manufacturing Process ◽  
Process Model ◽  
Model Development ◽  
Process Models ◽  
Powder Bed Fusion ◽  
Powder Bed ◽  
Future Work ◽  
Am Processes

In this paper, we advocate for a more harmonized approach to model development for additive manufacturing (AM) processes, through classification and metamodeling that will support AM process model composability, reusability, and integration. We review several types of AM process models and use the direct metal powder bed fusion AM process to provide illustrative examples of the proposed classification and metamodel approach. We describe how a coordinated approach can be used to extend modeling capabilities by promoting model composability. As part of future work, a framework is envisioned to realize a more coherent strategy for model development and deployment.

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