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    Wyświetlanie 1-5 z 5
    Tytuł:
    Aproksymacja rozkładów pierśnic w dwugeneracyjnych drzewostanach za pomocą rozkładów mieszanych. I. Estymacja parametrów
    Approximation of the breast height diameter distribution of two-cohort stands by mixture models. I. Parameter estimation
    Autorzy:
    Podlaski, R.
    Roesch, F.A.
    Powiązania:
    https://bibliotekanauki.pl/articles/994450.pdf
    Data publikacji:
    2013
    Wydawca:
    Polskie Towarzystwo Leśne
    Tematy:
    lesnictwo
    drzewostany dwupokoleniowe
    rozklad piersnic
    aproksymacja
    rozklad mieszany
    estymacja parametrow
    two−component mixtures
    tree diameter distribution
    weibull distribution
    gamma distribution
    starting strategy
    Opis:
    Study assessed the usefulness of various methods for choosing the initial values for the numerical procedures for estimating the parameters of mixture distributions and analysed variety of mixture models to approximate empirical diameter at breast height (dbh) distributions. Two−component mixtures of either the Weibull distribution or the gamma distribution were employed. The study plots, representing two−cohort stands, were located in the Świętokrzyski National Park (central Poland) and in the Southern Appalachian Mountains (eastern USA). A new strategy using three methods for choosing initial values (min.k/max.k for k=1, 5, 10; 0,5/1,5/mean; wp) for maximizing the likelihood during parameter estimation for mixture models for small and large plots is proposed.
    Źródło:
    Sylwan; 2013, 157, 08; 587-596
    0039-7660
    Pojawia się w:
    Sylwan
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Modelowanie rozkładów pierśnic młodocianych drzewostanów brzozy brodawkowatej na gruntach porolnych za pomocą dwuparametrowego rozkładu Weibulla
    Modeling dbh distribution of young silver birch stands on former agricultural lands with the 2-parameter Weibull distribution
    Autorzy:
    Zasada, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/991512.pdf
    Data publikacji:
    2013
    Wydawca:
    Polskie Towarzystwo Leśne
    Tematy:
    lesnictwo
    dendrometria
    drzewostany mlode
    grunty porolne
    drzewostany brzozowe
    brzoza brodawkowata
    Betula pendula
    piersnice drzew
    rozklad piersnic
    modelowanie
    rozklad Weibulla
    betula pendula
    secondary succession
    diameter distribution
    weibull
    Opis:
    The paper presents the diameter distributions of young silver fir stands (Betula pendula Roth.) growing on former agricultural lands described using the 2−parameter Weibull distribution. Various methods of parameters' estimation were tested: maximum likelihood method, method of moments and percentile approach. It was found, that the diameter distributions in such birch stands can have various shapes and forms – from close to the exponential to almost normal. The shape parameter were not affected by the age of the stand, but the scale parameter was strongly correlated with age. The most efficient methods for the tree diameter distribution modeling using the 2−parameter Weibull distribution are the method of moments and the maximum likelihood method. However, the obtained results does not exclude the percentile method, which is relatively simple and can be further modified for obtaining better results.
    Źródło:
    Sylwan; 2013, 157, 04; 268-277
    0039-7660
    Pojawia się w:
    Sylwan
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Modele struktury grubości w jednopiętrowych drzewostanach z udziałem jodły Abies alba Mill. i buka Fagus sylvatica L.
    Models of diameter structure in single-storied stands with fir Abies alba Mill.and beech Fagus sylvatica L.
    Autorzy:
    Podlaski, R.
    Pach, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/989766.pdf
    Data publikacji:
    2015
    Wydawca:
    Polskie Towarzystwo Leśne
    Tematy:
    lesnictwo
    drzewostany mieszane
    drzewostany jednopietrowe
    struktura grubosci
    jodla pospolita
    Abies alba
    buk zwyczajny
    Fagus sylvatica
    piersnice drzew
    rozklad piersnic
    rozklad Weibulla
    forest patches
    structural heterogeneity
    tree diameter distribution
    weibull distribution
    Opis:
    The objectives of the study were (1) to determine the models of diameter at breast height (dbh) distributions in single−storied mixed stands with fir Abies alba Mill. and beech Fagus sylvatica L. as well as (2) to assess the usefulness of Weibull distribution to approximation of empirical dbh distributions for distinguished models. In the Carpathians (southern Poland) and in the Świętokrzyskie Mountains (central Poland) 36 sample plots ranging in size from 0.1 to 0.4 ha were established. To identify the dbh distribution models in single−storied stands with similar empirical dbh distributions, the hierarchical cluster analysis (HCA) with the Jaccard's measure and the Ward's minimum variance agglomeration method was used. To approximate dbh distributions, the Weibull distribution was employed. Single−storied mixed stands with fir and beech, with the mean age between 50 and 70 years at the dbh, were characterised by a large diversity of dbh distributions. Three groups of stands (I, II, III) differing, among others, in average dbh were determined (fig. 1). In these groups the average dbh ranged from 23.5 to 32.6 cm, from 18.9 to 25.1 cm, and from 13.7 cm to 19.6 cm, respectively. Within these groups, seven models of unimodal distributions were selected (figs. 2−4; tab.). The models are characterised by varying degrees of asymmetry with the highest number of trees from less than 30/ha to more than 300/ha which occurred mainly in the dbh classes between 9 and 33 cm (models AS1, SM1, AS2, AS3, AS4, AS5, SM2). The results of χ² test indicate the high flexibility and suitability of Weibull distribution for modelling of such types of dbh structures.
    Źródło:
    Sylwan; 2015, 159, 07; 586-592
    0039-7660
    Pojawia się w:
    Sylwan
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Modele struktury grubości w dwu- i wielopiętrowych drzewostanach z udziałem jodły Abies alba Mill. i buka Fagus sylvatica L.
    Models of diameter structure in two- and multi-storied stands with fir Abies alba Mill. and beech Fagus sylvatica L.
    Autorzy:
    Pach, M.
    Podlaski, R.
    Powiązania:
    https://bibliotekanauki.pl/articles/989729.pdf
    Data publikacji:
    2015
    Wydawca:
    Polskie Towarzystwo Leśne
    Tematy:
    lesnictwo
    drzewostany mieszane
    struktura grubosci
    drzewostany dwupietrowe
    drzewostany wielopietrowe
    jodla pospolita
    Abies Alba
    buk zwyczajny
    Fagus sylvatica
    rozklad piersnic
    rozklad Weibulla
    rozklad mieszany
    tree diameter modelling
    forest complex structure
    weibull mixture model
    Opis:
    The objectives of the study were (1) to determine the models of diameter at breast height (dbh) distributions in two− and multi−storied mixed stands with fir Abies alba Mill. and beech Fagus sylvatica L. as well as (2) to assess the usefulness of single Weibull distribution and two−component mixture of Weibull distribution to approximation of empirical dbh distributions for distinguished models of dbh structures. In the Świętokrzyskie Mountains, 21 sample plots ranging in size from 0.2 to 0.4 ha were established. To identify the models of dbh distributions, in two− and multi−storied stands with similar empirical dbh distributions, the hierarchical cluster analysis (HCA) with the Jaccard's measure and the Ward's minimum variance agglomeration method were used. To approximate dbh distributions, the single Weibull distribution and the two−component mixture of Weibull distribution were employed. In two− and multi−storied mixed stands with fir and beech, with the mean age between 50 and 70 at the dbh, four models of dbh distributions were determined (fig. 1). Two of them were decreasing, strongly asymmetric (OS and OJ models; fig. 2) and the other two were increasing in the initial phase and decreasing in the final, having two maximums (DM1 and DM2 models; fig. 3). In the stands with the complex structure mixed distribution should be used to approximate empirical data. The analysis revealed high suitability and versatility of Weibull distribution both as single form and two−component mixture.
    Źródło:
    Sylwan; 2015, 159, 08; 632-638
    0039-7660
    Pojawia się w:
    Sylwan
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Modelowanie rozkładów pierśnic drzew z wykorzystaniem rozkładów mieszanych. II. Aproksymacja rozkładów pierśnic w lasach wielopiętrowych
    Modelling tree diameter distributions using mixture models. II. Approximation the breast height diameter distributions of multi-storeyed forests
    Autorzy:
    Podlaski, R.
    Powiązania:
    https://bibliotekanauki.pl/articles/973657.pdf
    Data publikacji:
    2011
    Wydawca:
    Polskie Towarzystwo Leśne
    Tematy:
    modelowanie
    rozklad mieszany
    rozklad Weibulla
    rozklad gamma
    aproksymacja
    dynamika drzewostanu
    Swietokrzyski Park Narodowy
    leśnictwo
    rozkład pierśnic
    drzewostany wielopiętrowe
    finite mixture models
    weibull distribution
    gamma distribution
    irregularly descending distributions
    forest dynamics
    Polska
    Świętokrzyski National Park
    Opis:
    The aim of the study is to (1) test the procedure of estimating mixture distribution parameters proposed in Podlaski [2011] and (2) present the universality and usefulness of mixture distributions for modelling the empirical distributions of breast height diameters on the example of two−generation stands with an asymmetric breast height diameter distributions. The tested procedure of estimating mixture distribution parameters allowed to calculate parameters for all analysed plots. Weibull and gamma distributions correctly approximated empirical distributions of breast height diameters of all investigated stands. The results presented in the study show the usefulness of mixture distributions to model asymmetric unimodal and poorly developed bimodal distributions of breast height diameters.
    Źródło:
    Sylwan; 2011, 155, 05; 293-300
    0039-7660
    Pojawia się w:
    Sylwan
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-5 z 5

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