Temat: PCA - Prolib Integro

Skocz do pozycji: 1.

Tytuł:: Effects of different fire severity levels on soil chemical and physical properties in Zagros forests of western Iran
Autorzy:: Ali, Mahdavi
Mehdi, Heydari
Ali, Salehi
Mostafa, Adibnejad
Wydawca:: Instytut Badawczy Leśnictwa, Komitet Nauk Leśnych PAN
Opis:: Przemysław Szmit
The study focused on the effect of different intensities of fire on physical and chemical properties of soil in Zagros forests of western Iran. The dominant tree species in these forests is oak (Quercus persica). Three sites were selected; high severity burned site (HS), low severity burned site (LS) and control (not burned) site (C). Soil chemical properties such as: organic matter (OM), the total nitrogen (N), NO3-N, soluble potassium (K), soil phosphorus (P), pH, soil electrical conductivity (EC), cation exchangeable capacity (CEC), base cations (Ca, Mg, Na), CO2 and soil physical properties such as saturation percentage (SP), bulk density (BD), sand, clay and silt percentages were assessed in soil samples. To determine significance of differences among the three observed sites and most effective variables in the separation of sample plots, one-way analysis of variance and principal component analysis were used, respectively. Mean pH, N, NO3- N, OM, SP, P, K, and CEC at HS site were lower than at the sites with other fire intensities but the EC value for HS site was higher in comparison with other sites observed. According to Duncan's test, mean BD value for HS site was higher when compared with other sites but SP value was comparatively lowest. At LS site, mean sand content was lowest and the amount of silt was highest, in comparison with other sites. The results showed that observed fire severities had significant effects on physical and chemical properties of soil, yet fire low severity and control sites were very similar to each other in terms of investigated factors. Therefore, it can be concluded that low-severity fire regime has no significant influence on soil properties. In a management strategy, controlled low-severity fire regime can be an alternative management tool in improving soil conditions.
Dostawca treści:: Repozytorium Centrum Otwartej Nauki

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Skocz do pozycji: 2.

Tytuł:: The impact of drought in 2015 on the health forest condition determined using Landsat-8 OLI images
Autorzy:: Rynkiewicz, Alicja
Rotchimmel, Karol
Kacprzak, Mariusz
Nasiłowska, Sylwia A.
Kotlarz, Jan
Kubiak, Katarzyna
Wydawca:: Instytut Badawczy Leśnictwa (Forest Research Institute), Sękocin Stary, Poland
Cytata wydawnicza:: Nasiłowska, S. A., Kotlarz, J., Kacprzak, M., Rynkiewicz, A., Rotchimmel, K., & Kubiak, K. (2019). The impact of drought in 2015 on the health forest condition determined using Landsat-8 OLI images, Forest Research Papers, 80(1), 55-68. doi: https://doi.org/10.2478/frp-2019-0005
Opis:: The main aim of this research was to determine the impact of drought (in 2015) on forests stand condition using remote sensing and statistical techniques. The study was based on the analysis of vegetation indices calculated from a series of Landsat-8 OLI satellite images covering the 2014 and 2015 growing seasons. Various tree biophysical and physical parameters as well as forest habitat characteristics were tested in order to find the most significant factors affecting drought resistance. Three approaches were used: (i) index differences, (ii) PCA analysis, and (iii) ANOVA statistical analysis. All three approaches used in this study indicate that forest biodiversity is the most important factor determining habitat response to stress conditions. Coniferous and mixed tree habitats were less sensitive than deciduous ones. Statistical analysis revealed the relationship between stress and soil types, as those more permeable were less dependent on rainwater. The highest stress was found for precipitation-dependent gley soils. Undergrowth density and height were also indicated as important factors inducing habitat response to a changing weather situation. All the results confirmed the usefulness of mid-infrared based indices for water shortage monitoring in forests. They confirmed that habitat biodiversity has a positive effect on its resistance to stressful conditions. Also forest type (conifer/deciduous) determines it's sensitivity. Precipitation and groundwater shortages have different effects on the forest condition depending on soil type.
Dostawca treści:: Repozytorium Centrum Otwartej Nauki

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Skocz do pozycji: 3.

Tytuł:: Tree crown size as a measure of tree biosocial positionin 135-year-old oak (Quercus L.) stand
Autorzy:: Zawieja, Bogna
Kaźmierczak, Katarzyna
Wydawca:: Instytut Badawczy Lesnictwa (Forest Research Institute), Komitet Nauk Lesnych PAN (The Committee on Forestry Sciences of the Polish Academy of Sciences)
Opis:: The paper presents an attempt to apply measurable traits of a tree – crown projection area, crown length, diameter at breast height and tree height for classification of 135-year-old oak (Quercus L.) trees into Kraft classes. Statistical multivariate analysis was applied to reach the aim. Empirical material was collected on sample plot area of 0.75 ha, located in 135-year-old oak stand. Analysis of dimensional traits of oaks from 135-year-old stand allows quite certain classification of trees into three groups: pre-dominant, dominant and co-dominant and dominated ones. This seems to be quite promising, providing a tool for the approximation of the biosocial position of tree with no need for assessment in forest. Applied analyses do not allow distinguishing trees belonging to II and III Kraft classes. Unless the eye-estimation-based classification is completed, principal component analysis (PCA) method provided simple, provisional solution for grouping trees from 135-year-old stand into three over-mentioned groups. Discriminant analysis gives more precise results compared with PCA. In the analysed stand, the most important traits for the evaluation of biosocial position were diameter at breast height, crown projection area and height.
Przemysław Szmit
Dostawca treści:: Repozytorium Centrum Otwartej Nauki

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Skocz do pozycji: 4.

Tytuł:: New Interpretation of Principal Components Analysis
Autorzy:: Gniazdowski, Zenon
Wydawca:: Warszawska Wyższa Szkoła Informatyki
Cytata wydawnicza:: Gniazdowski, Zenon. (2017). New Interpretation of Principal Components Analysis. Zeszyty Naukowe WWSI. 11. 43-65. 10.26348/znwwsi.16.43.
Opis:: A new look on the principal component analysis has been presented. Firstly, a geometric interpretation of determination coefficient was shown. In turn, the ability to represent the analyzed data and their interdependencies in the form of easy-tounderstand basic geometric structures was shown. As a result of the analysis of these structures it was proposed to enrich the classical PCA. In particular, it was proposed a new criterion for the selection of important principal components and a new algorithm for clustering primary variables by their level of similarity to the principal components. Virtual and real data spaces, as well as tensor operations on data, have also been identified.The anisotropy of the data was identified too.
Dostawca treści:: Repozytorium Centrum Otwartej Nauki

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Skocz do pozycji: 5.

Tytuł:: Application of GGE biplot graphs in multi-environment trials on selection of forest trees
Autorzy:: Ukalski, Krzysztof
Klisz, Marcin
Wydawca:: The Forest Sciences and Committee on Forestry Sciences and Wood Technology of the Polish Academy of Sciences; Instytut Badawczy Lesnictwa (Forest Research Institute), Sekocin Stary, Poland
Opis:: In the studies on selection and population genetics of forest trees that include the analysis of genotype × environment interaction (GE), the use of biplot graphs is relatively rare. This article describes the models and analytic methods useful in the biplot graphs, which enable the analyses of mega-environments, selection of the testing environment, as well as the evaluation of genotype stability. The main method presented in the paper is the GGE biplot method (G – genotype effect, GE –genotype × environment interaction effect). At the same time, other methods have also been referred to, such as, SVD (singular value decomposition), PCA (principal component analysis), linear-bilinear SREG model (sites regression), linear-bilinear GREG model (genotypes regression) and AMMI (additive main effects multiplicative interaction). The potential of biplot method is presented based on the data on growth height of 20 European beech genotypes (Fagus sylvatica L.), generated from real data concerning selection trials and carried out in 5 different environments. The combined ANOVA was performed using fixed-effects, as well as mixed-effects models, and significant interaction GE was shown. The GGE biplot graphs were constructed using PCA. The first principal component (GGE1) explained 54%, and the second (GGE2) explained more than 23% of the total variation. The similarity between environments was evaluated by means of the AEC method, which allowed us to determine one mega-environment that comprised of 4 environments. None of the tested environments represented the ideal one for trial on genotype selection. The GGE biplot graphs enabled: (a) the detection of a stable genotype in terms of tree height (high and low), (b) the genotype evaluation by ranking with respect to the height and genotype stability, (c) determination of an ideal genotype, (d) the comparison of genotypes in 2 chosen environments.
Przemysław Szmit
Dostawca treści:: Repozytorium Centrum Otwartej Nauki

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