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Alexander Levin - One of the best experts on this subject based on the ideXlab platform.

Klaus Von Gadow - One of the best experts on this subject based on the ideXlab platform.

  • Dynamic base-age invariant site index models for Tectona grandis in peninsular India
    Southern Forests: a Journal of Forest Science, 2014
    Co-Authors: Vindhya Prasad Tewari, Juan Gabriel Álvarez-gonzález, Klaus Von Gadow
    Abstract:

    Data from 27 remeasured sample plots were used to evaluate dynamic base-age invariant site index models for teak (Tectona grandis) forests in Karnataka, India. The data were obtained in observational field studies covering a wide range of sites in Karnataka and provided up to three interval measurements per plot. All the functions were fitted simultaneously using iterative seemingly unrelated regression and a base-age-invariant method. The model evaluation criteria were bias, root mean square error and the adjusted coefficient of determination. The best results were obtained with the generalised Algebraic Difference equations derived from the Korf base model. The selected model accounted for 99.8% of the total variance in height–age relationships in dominant trees. The dynamic base-age invariant site index model proved to be effective and accurate in presenting polymorphic site index curves with multiple asymptotes. The new dynamic base-age invariant site index models based on generalised Algebraic Difference approach (GADA) methodology can be recommended for dominant height prediction and forest site quality evaluations in the teak forests in Karnataka, India.

  • Estimating growth in beech forests: a study based on long term experiments in Switzerland
    Annals of Forest Science, 2010
    Co-Authors: Juan Gabriel Álvarez-gonzález, Andreas Zingg, Klaus Von Gadow
    Abstract:

    • This contribution presents a dynamic stand growth model for Beech (Fagus sylvatica L.) forests, based on a dataset provided by the Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Birmensdorf. The dataset includes 143 research plots, covering a wide range of growing sites and providing up to 16 interval measurements per research plot. • The objective of this research is to complement the range of existing beech growth models by bridging the gap between the historical yield tables and the single tree growth models. The specific aim is to develop transition functions which will project three state variables (dominant height, basal area and number of trees per hectare) at any particular time, in response to any arbitrary silvicultural treatment. • Two of the transition functions were derived using the generalized Algebraic Difference approach (GADA), the third one was derived with the Algebraic Difference approach (ADA). All the functions were fitted simultaneously using iterative seemingly unrelated regression and a base-age-invariant method. The influence of thinnings on basal area growth was included by fitting different transition functions for thinned and unthinned stands. • The overall model provides satisfactory predictions for time intervals up to 20 years. The new model is robust and its relatively simple structure makes it suitable for economic analysis and decision support.

  • Comparative modeling of stand development in Scots pine dominated forests in Estonia
    Forest Ecology and Management, 2007
    Co-Authors: Ahto Kangur, Andres Kiviste, Allan Sims, Kalev Jõgiste, Henn Korjus, Klaus Von Gadow
    Abstract:

    Abstract In general, forests in Estonia are characterized by great variability, not only in protected areas but in commercial forests as well. The data needed for the derivation and calibration of growth models can be obtained by continuous observation of permanent growth plots (also known as longitudinal studies) or by establishing chronosequences with temporary plots distributed over a wide range of growing sites, densities and ages (also known as cross-sectional studies). A compromise may be achieved by a system of “interval plots” (also known as a short-time series: series which covers a short time). Since the measurement interval is a period of undisturbed growth, it is possible to measure change rates as in a longitudinal study and at the same time cover a wide range of initial conditions as in a cross-sectional study. Numerous models of stand growth have been derived from re-measured sample plots. This study, which uses the data of 142 five-year intervals from 134 unmanaged Scots pine stands, compares six different model combinations involving Algebraic Difference equations and fixed time-step increment equations. New stand-level diameter and basal area increment equations and a tree survival model which showed close correspondence with the existing stand-level model for Estonia were developed. The main advantage of the use of Algebraic Difference equations over the fixed-step increment equations is the ability to use flexible time steps. However, the projection intervals should not deviate too much from the time steps of the measurement data. An important constraint when using the Algebraic Difference equations is to avoid long-term predictions in one projection sequence.

  • Compatible height and site index models for five pine species in El Salto, Durango (Mexico)
    Forest Ecology and Management, 2004
    Co-Authors: José Javier Corral Rivas, Juan Gabriel Álvarez González, Ana Daría Ruiz González, Klaus Von Gadow
    Abstract:

    Abstract Seven Algebraic Difference equations were used to develop site index models for major pine species of the forest region of El Salto, Durango (Mexico). Data from stem analysis of 160 trees of Pinus cooperi, P. durangensis, P. engelmannii, P. leiophylla and P. herrerae were obtained and a data structure involving all possible growth intervals was used to fit the equations. Generalized nonlinear least square methods were used to take into account the error structure. Autocorrelation was corrected expanding the error term to allow a first-order autoregressive model adequate for the data structure. Different weighting factors were employed to satisfy the equal error variance assumption. Bias, root mean square error and Akaike's information criterion were calculated and cross-validation residuals were used to evaluate the performance of the equations. The results indicate that models with multiple asymptotes achieve greater accuracy and precision. The best results were obtained with an Algebraic Difference equation derived from the base model of Hossfeld IV. Due to these species often constituting mixed stands with the same silvicultural treatments and rotation age, Differences among species in the best dominant-height equation were examined and tested using the nonlinear extra sum of squares method. The model parameters were significantly different among species. Based on the analysis, the Cieszewski and Bella polymorphic equation can be recommended for all five pine species. This function is polymorphic and base-age invariant with multiple asymptotes. It provides compatible site index and height growth estimates.

Miren Del Río - One of the best experts on this subject based on the ideXlab platform.

  • dominant height growth equations including site attributes in the generalized Algebraic Difference approach
    Canadian Journal of Forest Research, 2008
    Co-Authors: Margarida Tomé, Felipe Bravo, Gregorio Montero, Miren Del Río, Andres Bravooviedo
    Abstract:

    We present a new dynamic dominant height growth model based on Cieszewski's generalized Algebraic Difference approach (GADA) advanced dynamic site equation strengthened by the use of explicit climate and soil variables (i.e., H = f(H0,T0, T, site conditions)). The results suggest that the inclusion of climatic variables would improve the applicability of the inter-regional model in regions in which climate and soil type lead to intra-regional variability. The new model reduces the bias present in a previous dynamic model that did not include climatic at- tributes and improves the model efficiency across the different age classes. Climate has a multiplicative effect on dominant tree growth in the early development stages (<20 years) and an additive effect in older stands. Resume ´ : Nous presentons ici un nouveau modele dynamique de croissance en hauteur dominante fondesur l'equation de la methode de la Difference algebrique generalisee (GADA) de l'indice de qualitede station de Cieszewski renforcee par l'utilisation des variables explicites du climat et du sol, c.-a `-d. H = f(H0, T0, T ,etat du site). Les resultats indiquent que l'inclusion des variables climatiques permettrait d'ameliorer l'applicabilitedu modele interregional dans les regions oule climat et le type de sol sont al'origine de la variabiliteintraregionale. Le nouveau modele permet de reduire le biais present dans un modele dynamique precedent qui n'incluait pas les caracteristiques climatiques et ameliore l'efficacitede ce modele pour l'ensemble des classes d'age. Le climat exerce un effet multiplicateur sur la croissance des arbres domi- nants durant les premiers stades de developpement (<20 ans) et un effet additif dans les vieux peuplements. (Traduit par la Redaction)

  • Dominant height growth equations including site attributes in the generalized Algebraic Difference approach
    Canadian Journal of Forest Research, 2008
    Co-Authors: Andrés Bravo-oviedo, Margarida Tomé, Felipe Bravo, Gregorio Montero, Miren Del Río
    Abstract:

    We present a new dynamic dominant height growth model based on Cieszewski's generalized Algebraic Difference approach (GADA) advanced dynamic site equation strengthened by the use of explicit climate and soil variables (i.e., H = f(H0,T0, T, site conditions)). The results suggest that the inclusion of climatic variables would improve the applicability of the inter-regional model in regions in which climate and soil type lead to intra-regional variability. The new model reduces the bias present in a previous dynamic model that did not include climatic at- tributes and improves the model efficiency across the different age classes. Climate has a multiplicative effect on dominant tree growth in the early development stages (

  • Long-term trends in dominant-height growth of black pine using dynamic models
    Forest Ecology and Management, 2008
    Co-Authors: Dario Martin-benito, Miren Del Río, Guillermo Gea-izquierdo, Isabel Cañellas
    Abstract:

    Abstract Black pine (Pinus nigra Arn.) is a pan-Mediterranean species of high ecological importance and one of the most important timber species in the area. We compare several site dependent height–age models for the species in three regions along its natural distribution area in Spain. The best model was a generalized Algebraic Difference approach (GADA) polymorphic model with variable asymptotes (Cieszewski, C.J., Bailey, R.L., 2000. Generalized Algebraic Difference approach: theory based derivation of dynamic site equations with polymorphism and variable asymptotes. For. Sci. 46, 116–126). There was no significant increase in error when a reduced model common to the three regions was tested instead of a full model with region-specific parameters. To study possible biases of the proposed model along the trees’ lifespan we carried out a LOWESS analysis of residuals in time. We detected deviations in the model residuals, and a patent growth reduction in the 1960s and 1970s, which might be related to climate and/or changing stand characteristics. Departures from estimated mean past growth should be monitored in the future to adapt models to a changing environment.

  • Geographic variation and parameter assessment in generalized Algebraic Difference site index modelling
    Forest Ecology and Management, 2007
    Co-Authors: Andrés Bravo-oviedo, Miren Del Río, Gregorio Montero
    Abstract:

    Abstract Parameter assessment in site index modelling has proved useful prior to model specification. A base-age invariant model that supports polymorphism and variable asymptotes was fitted for Mediterranean Maritime pine in the inland part of Iberian Peninsula. A generalized Algebraic formulation of Hossfeld's model was found to be the most appropriate model in terms of biological consistency and fit statistics throughout the range of the data. Models were fitted to data from stem analysis and permanent sample plot measurement using a dummy variable approach and a continuous-time autoregressive structure to correct for autocorrelation. Model performance was evaluated using Jack–knife techniques applied to each growth series. The selected model was used in a regional-based comparison of growth patterns. The parameter identified as ‘global’ in the first part of the study was expanded with dummy variables to assess the Differences among regions. The stands located in the Northern Plateau, the Central Mountain Range, and South Eastern Mountains, exhibited different growth patterns from one another. However, these regions show a similar growth pattern to stands located in their origin of dispersion (Iberian Mountain Range). Consideration was also given to other factors which might lead to variation, such as environmental conditions.

  • Modelling dominant height growth and site index curves for rebollo oak (Quercus pyrenaica Willd.)
    Annals of Forest Science, 2006
    Co-Authors: Patricia Adame, Isabel Cañellas, Sonia Roig, Miren Del Río
    Abstract:

    A dominant height growth model and a site index model were developed for rebollo oak (Quercus pyrenaica Willd.) in northwest Spain. Data from 147 stem analysis in 90 permanent plots, where rebollo oak was the main species, were used for modelling. The plots were selected from the National Forest Inventory at random in proportion to four biogeoclimatic stratums. Different traditional and generalized Algebraic Difference equations were tested. The evaluation criteria included qualitative and quantitative examinations and a testing with independent data from another region. The generalized Algebraic Difference equation of Cieszewski based on Bailey equation showed the best results for the four stratums. An analysis of the height growth patterns among ecological stratums was made in order to study the necessity of different site index curves. Results indicated the validity of a common height growth model for the four stratums. In spite of the irregular height growth pattern observed in rebollo oak, probably due to past management, the model obtained allows us to classify and compare correctly rebollo oak stands growing at different sites.

Michael Wibmer - One of the best experts on this subject based on the ideXlab platform.

Chris J. Cieszewski - One of the best experts on this subject based on the ideXlab platform.

  • New dynamic site equation that fits best the Schwappach data for Scots pine (Pinus sylvestris L.) in Central Europe
    Forest Ecology and Management, 2007
    Co-Authors: Chris J. Cieszewski, Mike Strub, Michał Zasada
    Abstract:

    Abstract Using historical growth series data of Scots pine (Pinus sylvestris L.) in Central Europe we examine all the dynamic site equations previously used for modeling the height growth of this species as well as a new dynamic site equation that has not been used previously in the context of this forestry data. The tested models included two groups of anamorphic and polymorphic dynamic site equations (three-dimensional site–height–age models, such as Y = f(t,t0,y0)). One group of the models is based on the Algebraic Difference approach (ADA) implementation of different, preexisting base equations (two-dimensional equations, such as Y = f(t)). The other group of models is based on newer generalized Algebraic Difference approach (GADA) formulations of new site–height–age relationships that may use older models only as a part of their structure. The models were selected because they were relevant to Scots pine height growth modeling in other studies. We compared all the models with each other in terms of the sum of square deviations associated with fitting them simultaneously to all sites represented by the Scots pine data. All the fits were based on base-age invariant stochastic regressions, in which the global model parameters that are common to all growth series are estimated simultaneously with the site-specific effects that are different for each of the site productivity series. Cieszewski's model [Cieszewski, C.J., 2005. A new flexible GADA based dynamic site equation with polymorphism and variable asymptotes. PMRC Technical Report 2005-2] best described the data.

  • Derivation of Generic Dynamic Site Equations Using Generalized Algebraic Difference Approach
    2003
    Co-Authors: Chris J. Cieszewski, Michał Zasada
    Abstract:

    This article describes use of the Generalized Algebraic Difference Approach for derivation of generic dynamic site equations. The generic equations are useful in situations of unspecific expectations with regards to the final model form where one wants to test simultaneously in a single fitting many various models and assumptions about the modeled processes. Equations derived in this work are extremely flexible with various patterns of polymorphisms and asymptotes. Even thought in principle the generic equations have more parameters, those derived with methodology proposed here are very parsimonious.

  • Comparing Fixed- and Variable-Base-Age Site Equations Having Single Versus Multiple Asymptotes
    Forest Science, 2002
    Co-Authors: Chris J. Cieszewski
    Abstract:

    Site equations compute values of a variable Y as a function of both variable t and a value of the variable Y = Y 0 measured at an arbitrary t = t 0 . For example, the plant size (Y) can be defined as a function of both age (t) and a reference size (Y 0 ) measured at the base age t 0 . The base age can be implicit (i.e., implied but hidden), as in fixed-base-age equations (e.g., Y = f(t, S), where S is Y at t = 50), or explicit (i.e., readily exposed and changeable), as in dynamic equations (e.g., Y = f(t, t 0 , Y 0 )). Using as the main criterion the ability of an equation to generate concurrent polymorphism and multiple asymptotes, I compare a fixed-base-age height growth site equation with several dynamic equations, derived through the traditional and the Generalized Algebraic Difference Approaches. The comparison leads to conclusions about desirable model properties, the methodologies of derivations, and expected outcomes of the different methodologies. The conclusions suggest that the ability to simulate concurrent polymorphism and multiple asymptotes is an important property of site equations that should be considered during modeling various growth trends. Furthermore, the conclusions suggest that both Algebraic Difference approaches are more parsimonious and robust than the fixed- base-age approaches. The Generalized Algebraic Difference Approach can increase model usefulness considerably through derivation of more complex equations that can achieve more desirable properties. FOR. SCI. 48(1): 7-23.

  • Generalized Algebraic Difference approach: theory based derivation of dynamic site equations with polymorphism and variable asymptotes.
    Forest Science, 2000
    Co-Authors: Chris J. Cieszewski, R. L. Bailey
    Abstract:

    Biologically realistic site models require the ability to concurrently express variable asymptotes and polymorphism in curve shapes. Moreover, it is only logical and rational to require that these models be invariant to changes in the index or base age. This manuscript explains the Generalized Algebraic Difference Approach that can be used effectively to derive truly base-age invariant Difference equations capable of describing concurrent polymorphism and variable asymptotes. This new generic methodology for derivation of even the most complex dynamic equations is mathematically sound. The equations derived with it can be extremely flexible and may generate intricate patterns of concurrent polymorphism and variable asymptotes. This methodology is relevant to all situations in which the dependent variable is a function of an unobservable variable, and the models can be implicitly defined by their initial conditions. It is equally useful for derivation of new equations and for improvement of existing base-age specific equations.