scholarly journals Diameter-height models for the Terai tree species

2015 ◽  
Vol 25 (1) ◽  
pp. 50-54 ◽  
Author(s):  
A. Khadka ◽  
T. Subedi ◽  
M. Ghimire ◽  
B. P. Dhakal ◽  
H. Parikka
Keyword(s):  
Tree Species ◽  
Linear Models ◽  
Resource Assessment ◽  
Forest Growth ◽  
Growth And Yield ◽  
Forest Resource ◽  
Linear Mixed Effects ◽  
Shorea Robusta ◽  
Non Linear ◽  
Growth And Yield Models

Tree diameter-height relationship can be used as a key input component in forest growth and yield models, and description of stand dynamics. Various models of stem diameter and height relation were developed. Those were formulated and implemented during Terai forest inventory data calculations in the Forest Resource Assessment (FRA) Nepal Project. The field inventory was conducted from December, 2010 to March, 2011. The Concentric Circular Sample Plot was designed where the diameters at breast height of all the tallied trees and the heights of the sampled trees were measured. The data were handled with R-script in R Programme to generate non-linear mixed effects models in ‘lmfor’ package of forest biometrics functions of Mehtatalo. Different non-linear models were used to fit the diameter-height relation, which performed well in describing the relationships between the diameters and the heights of the Terai tree species depending on the sample size. The models were selected as the best fitted based on the statistical results such as standard error, Adjusted R2, RMSE and residuals. The best models for Shorea robusta and Terminalia alata were generated using Wykoff’s and Naslund’s functions, respectively.Banko Janakari, A Journal of Forestry Information for NepalVol. 25, No. 1Page: 50-54

scholarly journals StandsSIM-MD: a Management Driven forest SIMulator

2016 ◽  
Vol 25 (2) ◽  
pp. eRC07 ◽  
Author(s):  
Susana Barreiro ◽  
João Rua ◽  
Margarida Tomé
Keyword(s):  
Forest Management ◽  
Tree Species ◽  
Growth Models ◽  
Planning Horizon ◽  
Md Simulations ◽  
Forest Growth ◽  
Growth And Yield ◽  
Management Approaches ◽  
User Friendly ◽  
Growth And Yield Models

Aim of the study: The existing stand level forest simulators available in Portugal were not developed with the aim of including up-to-date model versions and were limited in terms of accounting for forest management. The simulators’ platform, sIMfLOR was recently created to implement different growth models with a common philosophy. The objective was developing one easily-updatable, user-friendly, forest management and climate change sensitive simulator capable of projecting growth for the main tree species in Portugal.Area of the study: Portugal.Material and methods: The new simulator was programmed in a modular form consisting of several modules. The growth module integrates different forest growth and yield models (empirical and process-based) for the main wood production tree species in Portugal (eucalypt, umbrella and maritime pines); whereas the management module drives the growth projections along the planning horizon according to a range of forest management approaches and climate (at present only available for eucalypt).Main results: The main result is the StandsSIM-MD Management Driven simulator that overcomes the limitations of the existing stand level simulators. It is a step forward when compared to the models currently available in the sIMfLOR platform covering more tree species, stand structures and stand compositions. It is focused on end-users and it is based on similar concepts regarding the generation of required inputs and generated outputs.Research highlights:-          Forest Management Driven simulations approach-          Multiple Prescriptions-Per-Stand functionality-          StandsSIM-MD can be used to support landowners decisions on stand forest management-          StandsSIM-MD simulations at regional level can be combined with optimization routinesKeywords: Forest simulator, Forest Management Approaches; StandsSIM-MD; forest management.

Ontario's forest growth and yield modelling program: Advances resulting from the Forestry Research Partnership

2008 ◽  
Vol 84 (5) ◽  
pp. 694-703 ◽  
Author(s):  
Mahadev Sharma ◽  
John Parton ◽  
Murray Woods ◽  
Peter Newton ◽  
Margaret Penner ◽  
...  
Keyword(s):  
Tree Species ◽  
Stand Density ◽  
Forest Growth ◽  
Growth And Yield ◽  
Research Partnership ◽  
Wood Supply ◽  
Permanent Sample Plots ◽  
Forestry Research ◽  
Research Activities ◽  
Forest Growth And Yield

The province of Ontario holds approximately 70.2 million hectares of forests: about 17% of Canada’s and 2% of the world’s forests. Approximately 21 million hectares are managed as commercial forests, with an annual harvest in the early part of the decade approaching 200 000 ha. Yield tables developed by Walter Plonski in the 1950s provide the basis for most wood supply calculations and growth projections in Ontario. However, due to changes in legislation, policy, and the planning process, they no longer fully meet the needs of resource managers. Furthermore, Plonski`s tables are not appropriate for the range of silvicultural options now practised in Ontario. In October 1999, the Canadian Ecology Centre- Forestry Research Partnership (CEC-FRP) was formed and initiated a series of projects that collectively aimed at characterizing, quantifying and ultimately increasing the economically available wood supply. Comprehensive, defensible, and reliable forecasts of forest growth and yield were identified as key knowledge gaps. The CEC-FRP, with support from the broader science community and forest industry, initiated several new research activities to address these needs, the results of which are outlined briefly in this paper. We describe new stand level models (e.g., benchmark yield curves, FVS Ontario, stand density management diagrams) that were developed using data collected from permanent sample plots and permanent growth plots established and remeasured during the past 5 decades. Similarly, we discuss new height–diameter equations developed for 8 major commercial tree species that specifically account for stand density. As well, we introduce a CEC-FRP-supported project aimed at developing new taper equations for plantation grown jack pine and black spruce trees established at varying densities. Furthermore, we provide an overview of various projects undertaken to explore measures of site productivity. Available growth intercept and site index equations are being evaluated and new equations are being developed for major commercial tree species as needed. We illustrate how these efforts are advancing Ontario’s growth and yield program and supporting the CEC-FRP in achieving its objective of increasing the supply of fibre by 10% in 10 years while maintaining forest sustainability. Key words: permanent sample plots (PSPs), permanent growth plots (PGPs), normal yield tables, sustainable forest management, NEBIE plot network, forest inventory, Forest Vegetation Simulator

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

scholarly journals Modelling height-diameter relationship for Pinus wallichiana trees for Lete and Kunjo of Mustang district

2013 ◽  
Vol 21 (2) ◽  
pp. 13-23
Author(s):  
B. H. Wagle ◽  
R. P. Sharma
Keyword(s):  
Linear Models ◽  
Weibull Model ◽  
Growth And Yield ◽  
Height Variation ◽  
Growth Simulation ◽  
Pinus Wallichiana ◽  
Pine Trees ◽  
Tree Data ◽  
Growth And Yield Models ◽  
Simulation Systems

Quantifi cation of height-diameter relationship helps in better understanding of stand dynamics. Height-diameter models can be used as necessary inputs to growth and yield models and growth simulation systems. The researchers developed height-diameter models with 364 Blue pine (Pinus wallichiana) tree data from Lete and Kunjo Village Development Committees (VDCs) of Mustang district. Eighteen non-linear models were calibrated, among which, Weibull model described the largest proportion of height variation (R2 adj = 0. 9362). Gunary and Chapman-Richards’ models also appeared almost identical to Weibull model in terms of fi t statistics and graphical appearance. The researchers recommend Weibull model for predicting total heights of Blue pine trees for the VDCs covered by the study.DOI: http://dx.doi.org/10.3126/banko.v21i2.9125Banko Janakari Vol. 21, NO. 2, 2011 Page: 13-23 Uploaded date: 10 November, 2013 

scholarly journals Towards understanding the role of ectomycorrhizal fungi in forest phosphorus cycling : a modelling approach

2018 ◽  
Vol 64 (2) ◽  
pp. 79-95 ◽  
Author(s):  
Michiel F. Bortier ◽  
Enrique Andivia ◽  
José G. Genon ◽  
Tine Grebenc ◽  
Gaby Deckmyn
Keyword(s):  
Ectomycorrhizal Fungi ◽  
Nutrient Availability ◽  
Forest Ecosystem ◽  
P Uptake ◽  
Forest Growth ◽  
Growth And Yield ◽  
Management Scenarios ◽  
Soil P ◽  
Growth And Yield Models

Abstract Many studies have shown the importance of ectomycorrhizal fungi (EM) in forests both for nutrient availability and for carbon (C) and nutrient cycling in the soil. Yet so far they are not incorporated in forest ecosystem growth and yield models. Recent research suggests phosphorus (P) shortage could be a major constraints to forest productivity in the future. For a realistic simulation of future forest ecosystem functioning, inclusion of detailed soil P cycling and the trees-EM interaction is necessary. We developed a full ecosystem P model that simulates P uptake by roots and EM, allocation within trees, physiological deficiency effects on C assimilation and allocation, release through litter decomposition, coupled with water, C and nitrogen (N) fluxes accounted for in the mechanistic forest stand model ANAFORE. Our results confirm the importance of incorporating EM in forest ecosystem models and suggest that the lack of incorporation of P in models may result in an under- or overestimation of forest growth. This new model has the potential of being used to assess the response of trees and/or stands to nutrient availability under different climate and management scenarios. With the current parameterization it is functional as a scientific research tool to investigate hypotheses.

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 Use of non-linear mixed-effects modelling and regression analysis to predict the number of somatic coliphages by plaque enumeration after 3 hours of incubation

2017 ◽  
Vol 15 (5) ◽  
pp. 706-717 ◽  
Author(s):  
Javier Mendez ◽  
Antonio Monleon-Getino ◽  
Juan Jofre ◽  
Francisco Lucena
Keyword(s):  
Linear Models ◽  
Mixed Effects ◽  
Repeated Measurements ◽  
Suitable Model ◽  
Laboratory Equipment ◽  
Linear Mixed Effects ◽  
Non Linear ◽  
Agar Layer ◽  
Linear Fit ◽  
Working Day

The present study aimed to establish the kinetics of the appearance of coliphage plaques using the double agar layer titration technique to evaluate the feasibility of using traditional coliphage plaque forming unit (PFU) enumeration as a rapid quantification method. Repeated measurements of the appearance of plaques of coliphages titrated according to ISO 10705-2 at different times were analysed using non-linear mixed-effects regression to determine the most suitable model of their appearance kinetics. Although this model is adequate, to simplify its applicability two linear models were developed to predict the numbers of coliphages reliably, using the PFU counts as determined by the ISO after only 3 hours of incubation. One linear model, when the number of plaques detected was between 4 and 26 PFU after 3 hours, had a linear fit of: (1.48 × Counts3 h + 1.97); and the other, values &gt;26 PFU, had a fit of (1.18 × Counts3 h + 2.95). If the number of plaques detected was &lt;4 PFU after 3 hours, we recommend incubation for (18 ± 3) hours. The study indicates that the traditional coliphage plating technique has a reasonable potential to provide results in a single working day without the need to invest in additional laboratory equipment.

Integrating biophysical controls in forest growth and yield predictions with artificial intelligence technology

2013 ◽  
Vol 43 (12) ◽  
pp. 1162-1171 ◽  
Author(s):  
M. Irfan Ashraf ◽  
Zhengyong Zhao ◽  
Charles P.-A. Bourque ◽  
David A. MacLean ◽  
Fan-Rui Meng
Keyword(s):  
Artificial Intelligence ◽  
Nova Scotia ◽  
Soil Water ◽  
Tree Growth ◽  
Forest Growth ◽  
Growth And Yield ◽  
Individual Tree ◽  
Artificial Intelligence Technology ◽  
Growth And Yield Models ◽  
Forest Growth And Yield

Growth and yield models are critically important for forest management planning. Biophysical factors such as light, temperature, soil water, and nutrient conditions are known to have major impacts on tree growth. However, it is difficult to incorporate these biophysical variables into growth and yield models due to large variation and complex nonlinear relationships between variables. In this study, artificial intelligence technology was used to develop individual-tree-based basal area (BA) and volume increment models. The models successfully account for the effects of incident solar radiation, growing degree days, and indices of soil water and nutrient availability on BA and volume increments of over 40 species at 5-year intervals. The models were developed using data from over 3000 permanent sample plots across the province of Nova Scotia, Canada. Model validation with independent field data produced model efficiencies of 0.38 and 0.60 for the predictions of BA and volume increments, respectively. The models are applicable to predict tree growth in mixed species, even- or uneven-aged forests in Nova Scotia but can easily be calibrated for other climatic and geographic regions. Artificial neural network models demonstrated better prediction accuracy than conventional regression-based approaches. Artificial intelligence techniques have considerable potential in forest growth and yield modelling.

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