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Wyświetlanie 1-6 z 6
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:
Aproksymacja rozkładów pierśnic drzew w dwugeneracyjnych drzewostanach za pomocą rozkładów mieszanych. III. Estymatory jądrowe a rozkłady mieszane
Approximation of the breast height diameter distribution of two-cohort stands by mixture models. III. Kernel density estimators vs mixture models
Autorzy:
Podlaski, R.
Roesch, F.A.
Powiązania:
https://bibliotekanauki.pl/articles/990995.pdf
Data publikacji:
2014
Wydawca:
Polskie Towarzystwo Leśne
Tematy:
lesnictwo
drzewostany dwupokoleniowe
rozklad piersnic
aproksymacja
rozklad mieszany
rozklad Weibulla
estymatory jadrowe nieparametryczne
two−component models
kernel density estimator
tree diameter distribution
monte carlo simulation
Opis:
Two−component mixtures of either the Weibull distribution or the gamma distribution and the kernel density estimator were used for describing the diameter at breast height (dbh) empirical distributions of two−cohort stands. The data consisted of study plots from the Świętokrzyski National Park (central Poland) and areas close to and including the North Carolina section of the Great Smoky Mountains National Park (USA; southern Appalachians). Kernel density estimators belong to a class of nonparametric density estimators. Nonparametric estimators have no fixed structure and depend upon all the data points to reach an estimate. In this study the Weibull and the gamma mixture distributions were the most versatile models. The results also support the conclusion that there are only minor differences between the parametric models and the kernel density estimates.
Źródło:
Sylwan; 2014, 158, 06; 414-422
0039-7660
Pojawia się w:
Sylwan
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Aproksymacja rozkładów pierśnic drzew w drzewostanach dwugeneracyjnych za pomocą rozkładów mieszanych. II. Testy zgodności
Approximation of the breast height diameter distribution of two-cohort stands by mixture models. II. Goodness-of-fit tests
Autorzy:
Podlaski, R.
Roesch, F.A.
Powiązania:
https://bibliotekanauki.pl/articles/993354.pdf
Data publikacji:
2013
Wydawca:
Polskie Towarzystwo Leśne
Tematy:
lesnictwo
drzewostany dwupokoleniowe
rozklad piersnic
aproksymacja
rozklad mieszany
testy zgodnosci
two−component mixtures
tree diameter distribution
nonparametric goodness−of−fit tests
discrete null distribution
Opis:
The goals of this study are (1) to analyse the accuracy of the approximation of empirical distributions of diameter at breast height (dbh) using two−component mixtures of either the Weibull distribution or the gamma distribution in two−cohort stands, and (2) to discuss the procedure of choosing goodness−of−fit tests. The study plots were located in the Świętokrzyski National Park (central Poland) and in the Southern Appalachian Mountains (eastern USA). The results of the goodness−of−fit tests (chi−squared, Kolmogorov−Smirnov, Cramér−von Mises, and Anderson−Darling), normalised bias and normalised root mean square error, indicate that dbh empirical distributions of two−cohort stands are compatible with the mixture models investigated. The chi−squared test and the generalization of the Anderson−Darling test to discrete distributions should be used to assess whether empirical dbh data are consistent with a hypothesized null distribution.
Źródło:
Sylwan; 2013, 157, 09; 652-661
0039-7660
Pojawia się w:
Sylwan
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Rozkłady teoretyczne najlepiej aproksymujące strukturę pierśnic w drzewostanach świerkowych regla górnego w rezerwacie przyrody "Śnieżnik Kłodzki"
Theoretical distributions in approximation of breast height diameter structure in upper mountain zone Norway spruce stands in 'Snieżnik Klodzki' nature reserve
Autorzy:
Sinica, P.
Tomusiak, R.
Tkaczyk, M.
Powiązania:
https://bibliotekanauki.pl/articles/989425.pdf
Data publikacji:
2016
Wydawca:
Polskie Towarzystwo Leśne
Tematy:
lesnictwo
regiel gorny
rezerwat Snieznik Klodzki
drzewostany swierkowe
swierk pospolity
Picea abies
piersnice drzew
rozklad piersnic
aproksymacja
rozklad teoretyczny
dbh distribution
stand structure
native type forests
picea abies
Opis:
The study on the structure of Norway spruce old−growth stands of original provenience in upper mountain zone was carried out in a nature reserve ‘Śnieżnik Kłodzki', located in the Lądek Zdrój Forest District (SW Poland). The fieldwork was conducted in three spruce stands located at the altitude of 1,215 and 1,235 m a.s.l. The breast height diameters (dbh) of living trees were characterized. The aim of this study is to characterize the structure of dbh of trees in spruce stands of subalpine forest. Implementation of the objective will be associated with the characteristics of empirical distributions dbh and an indication of theoretical distributions of continuous random variable best approximating the structure of dbh. The comparison of empirical dbh distributions with 36 theoretical distributions were carried out, but goodness−of−fit tests proven statistically significant compatibility with seventeen of them: beta (4−parameter), Cauchy, exponential power, folded normal, gamma (3−parameter), generalized logistic, Laplace, logistic, loglogistic, loglogistic (3−parameter), lognormal (3−parameter), noncentral chi−square, normal, smallest extreme value, triangular, Weibull and Weibull (3−parameter). The dbh distributions in upper mountain spruce stands are the best fitted with logistic distribution, and subsequently loglogistic (3−parameter), generalized logistic and Weibull (3−parameter) distributions. That four distributions can be used in individual tree growth models while generating structure dbh of trees in the stand. The knowledge of dbh structure in protected stands could be helpful in shaping spruce stand structure in planned silvicultural treatments, and shows the need for silvicultural treatments in upper mountain spruce stands.
Źródło:
Sylwan; 2016, 160, 11; 905-914
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
Tytuł:
Ocena przydatności wybranych funkcji do modelowania rozkładu pierśnic w drzewostanach olszy czarnej (Alnus glutinosa (L.) Gaertn.)
Evaluation of usefulness of selected functions for modeling distribution of breast height diameter in black alder stands (Alnus glutinosa (L.) Gaertn.)
Autorzy:
Orzeł, S.
Pogoda, P.
Ochał, W.
Powiązania:
https://bibliotekanauki.pl/articles/988989.pdf
Data publikacji:
2017
Wydawca:
Polskie Towarzystwo Leśne
Tematy:
lesnictwo
drzewostany olszowe
struktura grubosci
olsza czarna
Alnus glutinosa
piersnice drzew
rozklad piersnic
rozklad teoretyczny
aproksymacja
modelowanie
funkcja gestosci prawdopodobienstwa
test Kolmogorowa-Smirnowa
diameter at breast height
diameter distribution
probability density function
kolmogorov−smirnov test
Opis:
We evaluated the usefulness of ten theoretical probability density functions for the approximation of the breast height diameter distributions in managed alder stands growing in the western part of the Sandomierz Basin (southern Poland). The study material consisted of measurement results for 22,530 alders obtained for 844 circular sample plots, established in 163 stands aged 6−89. In the area of particular stands, from 2 to 10 age−dependent circular sample plots sized 0.01−0.10 ha were systematically arranged. We evaluated the following theoretical probability distributions: normal (N), double normal (P−N), Johnson SB (J), Weibull (W), beta (B), Burr (Bu), gamma (G), log−normal (L−N), log−logistic (L−L) and Birnbaum−Saunders (B−S). Additionally the usefulness of the W, B, Bu, G, L−N, L−L and B−S distributions with omitted location parameter was tested. The goodness−of−fit of each probability density function was assessed based on the Kolmogorov−Smirnov statistic, the root mean square error and ranks established on their basis. It was found that DBH distribution of majority stands is characterized by right−sided asymmetry and negative kurtosis. It was showed that the best distribution for the breast height diameter structure approximation of alder stands is the Johnson SB (J) distribution. To describe the frequency of thickness, normal (N) and log−logistic (L−L) distribution should not be used. Elimination of location parameter significantly affects usefulness of probability density functions to modeling empirical distributions of breast height diameter. Gamma and Burr distributions with omitted location parameter gave the best results in description the frequency of breast height diameter. In certain situations, these distributions can also be used to describe the structure of breast height diameter of alder stands.
Źródło:
Sylwan; 2017, 161, 02; 101-113
0039-7660
Pojawia się w:
Sylwan
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-6 z 6

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