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    Wyświetlanie 1-7 z 7
    Tytuł:
    Ocena zgodnosci rozkladow piersnic drzew drzewostanow brzozowych z niektorymi rozkladami teoretycznymi
    Autorzy:
    Zasada, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/813305.pdf
    Data publikacji:
    2000
    Wydawca:
    Polskie Towarzystwo Leśne
    Tematy:
    modele wzrostu
    dendrometria
    rozklad piersnic
    brzoza
    lesnictwo
    Betula
    drzewostany brzozowe
    drzewa lesne
    Źródło:
    Sylwan; 2000, 144, 05; 43-48
    0039-7660
    Pojawia się w:
    Sylwan
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Uproszczony model rozkładu pierśnic jednowiekowych niepielęgnowanych drzewostanów sosnowych (Pinus sylvestris L.)
    Simplified model of diameter distribution for even-aged unthinned Scots pine (Pinus sylvestris L.) stands
    Autorzy:
    Jagiełło, R.
    Beker, C.
    Powiązania:
    https://bibliotekanauki.pl/articles/986956.pdf
    Data publikacji:
    2017
    Wydawca:
    Polskie Towarzystwo Leśne
    Tematy:
    lesnictwo
    dendrometria
    sosna zwyczajna
    Pinus sylvestris
    drzewostany sosnowe
    drzewostany jednowiekowe
    drzewostany niepielegnowane
    rozklad piersnic
    rozklad uproszczony
    rozklad gamma
    diameter distribution
    gamma poisson
    scots pine
    unthinned stand
    Opis:
    Although modelling of the diameter at the breast height (DBH) distributions has long history, theoretical discrete distributions have not so far been used for this purpose. In this study we use measurements covering 25 years (six inventories) without silvicultural influence on 14 even−aged Scots pine (Pinus sylvestris L.) stands to develop the DBH distribution models. Analysed stands are located in Murowana Goślina Forest Experimental Station (W Poland). The objective of the study was to elaborate the most simplified model that applies stand variables easy to assess and uncomplicated theoretical distribution. We employed two−parameter Gamma Poisson (GP) distribution and compared it to Weibull (W) and Sb Johnson (SbJ) ones. When maximum likelihood estimation (MLE) was used, GP gave similar results to W and both were slightly worse than SbJ. We found that both DBH standard deviation and stand density have substantial impact for model bias when above distributions used. Stepwise regression analysis was used for obtaining linear equations for parameter prediction of GP distribution. Then, GP model was simplified by removing standard deviation of DBH (SDD) from equation for overdispersion parameter. Results showed slight increase in mean of error values (i.e. modified Reynolds e index and root mean square error) for simplified model (SGP) compared with those for model including SDD, but differences in means were insignificant. Minimal and mean DBH represent enough variability of diameter distribution to obtain appropriate model based on Gamma Poisson distribution. Error was only 5% greater from four−parameter SbJ (MLE) distribution with similar range: 8.2−28.8% against 5.1−25.5% for SGP and SbJ respectively. The presented model can be used in many branches of forestry for more accurate calculation of stand level variables, when additional allometric equations employed, for instance assimilation apparatus volume or below− and aboveground biomass.
    Źródło:
    Sylwan; 2017, 161, 10; 822-830
    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:
    Szerokość pasma jądrowego estymatora rozkładu pierśnic w drzewostanach olszy czarnej (Alnus glutinosa (L.) Gaertn.) z zachodniej części Kotliny Sandomierskiej
    Bandwidth of kernel estimator of DBH distribution in black alder (Alnus glutinosa (L.) Gaertn.) stands from west part of the Sandomierz Basin
    Autorzy:
    Pogoda, P.
    Ochał, W.
    Orzeł, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/985919.pdf
    Data publikacji:
    2018
    Wydawca:
    Polskie Towarzystwo Leśne
    Tematy:
    lesnictwo
    dendrometria
    drzewa lesne
    olsza czarna
    Alnus glutinosa
    piersnice drzew
    rozklad piersnic
    estymacja
    estymatory jadrowe nieparametryczne
    kernel estimator
    bandwidth
    dbh structure
    black alder
    Opis:
    Set of ‘nonparametric’ methods, that don’t make a priori assumption about functional form of empirical distribution was developed as an alternative to the parametric distribution modeling. The kernel estimators are one of such methods, that can be used to describe the frequency of data representing for example DBH records. Kernel smoothing requires the choice of weighting function and bandwidth also called as smoothing parameter or window. The lack of comprehensive analysis on the applicability of particular bandwidth selection methods to model DBH structure gave an impulse to present investigation aimed at determining value and variability of smoothing parameter in black alder stands. The optimal bandwidth was obtained according to six different variants of plug−in method proposed by Altman and Léger. Presented investigations were based on DBH measurements collected in 163 managed black alder stands aged from 6 to 89 years, growing in the west part of the Sandomierz Basin (S Poland). We measured in total 22,530 black alders, from 48 to 359 in individual stand. Stands were characterized by: age, quadratic mean diameter, basal area, mean height, Reineke’s stand density index and standard deviation of DBH. Smoothing parameter was obtained by means of plug−in method with the pilot bandwidth selected by: Silverman’s rule of thumb (nrd0), Scott’s method (nrd), unbiased cross−validation (ucv), biased cross−validation (bcv), method of Sheather and Jones (sj) and one−stage method of Wand and Jones (onestage). The bandwidth was first obtained to real data, then to 100 bootstrap samples of 5, 10, 15 ... and 100 trees from each stand. Smoothing parameters were characterized by mean and variance. Relationship between values of smoothing parameter and stand characteristics was determined. Finally the influence of sample size on value and variability of bandwidth was assessed. Value and variability of smoothing parameter in black alder stands are determined by stand age, sample size and method of bandwidth choice. There is a close relationship between bandwidth and the mean height (r from 0.75 to 0.83), quadratic mean diameter (r from 0.79 to 0.88) and standard deviation of DBH (r from 0.84 to 0.93). Potentially these stand features can be used to predict smoothing parameter values. Minor changes of bandwidth for samples containing above 50 trees together with persistence of standard error give an objective grounds for defining optimal number of diameters, that are necessary to kernel estimation of DBH distribution.
    Źródło:
    Sylwan; 2018, 162, 05; 411-421
    0039-7660
    Pojawia się w:
    Sylwan
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Dokładność określania wybranych parametrów rozkładów pierśnic drzew w drzewostanach sosnowych za pomocą naziemnego skanowania laserowego
    Accuracy of the selected tree diameter distributions parameters assessed using terrestrial laser scanning in Scots pine stands
    Autorzy:
    Zasada, M.
    Sterenczak, K.
    Powiązania:
    https://bibliotekanauki.pl/articles/994333.pdf
    Data publikacji:
    2013
    Wydawca:
    Polskie Towarzystwo Leśne
    Tematy:
    lesnictwo
    dendrometria
    zasoby drzewne
    inwentaryzacja
    drzewostany sosnowe
    powierzchnie probne kolowe
    rozklad piersnic
    dokladnosc
    skanowanie laserowe
    forest inventory
    circular sample plots
    quadratic mean diameter
    percentile
    skewness
    kurtosis
    Opis:
    When using such methods as terrestrial laser scanning (TLS), one of the major factors influencing the accuracy of stand characteristics determination is the visibility of trees on a sample plot, which is often obscured by the shadow effect caused by trees located closer to the plot center. Because of this, the percentage of the identified trees and basal area depends on the distance from the plot center: the accuracy of stocking determination decreases as the plot radius increases. The values of such stand characteristics as average breast height diameter, standard deviation of tree diameters and percentiles of the tree diameters' distributions assessed based on all trees and the visible trees only are not significantly different from each other for circular sample plots with 20 m radius. Skewness and kurtosis are not significantly different in plots with radius of 5 and 10 meters. For the 15 m plot radius the difference was significant for about 15% of the analyzed plots. The obtained results correspond with previous findings that report that on the circular sample plots with radius up to 15 m the errors for the number of trees and basal area are relatively small and can be accepted in the practical inventory. The results support the circular sample plots size optimization, including measurements performed using a point cloud.
    Źródło:
    Sylwan; 2013, 157, 12; 883-891
    0039-7660
    Pojawia się w:
    Sylwan
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-7 z 7

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