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Genetic diversity in relation to secondary succession of forest tree communities

Wehenkel C., Corral-Rivas J., Hernandez-Diaz J.

Polish Journal of Ecology

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2011

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Vol. 59, nr 1

45-54

EN

Forest succession is a fundamental ecological process, which has significant implications for the biological, biophysical, and biogeochemical processes in an ecosystem. Genetic diversity is not only a product of the number of species present in a given area, but also of successional change from colonization of gaps by pioneer species to mature climax forest. Genetic diversity should be higher in earlier successional stages than in later stages because high environmental predictability in later successional stages favours low genetic diversity. In the present study the relationship between secondary succession and genetic diversity was explored in eight stands of characteristic tree communities in the Thuringian forest area (Germany). Each of the eight stands was subdivided into six plots in a grid of 40 x 40 m to detect as much as possible tree species and genetic variants within the forest tree community and successionspecific structures. To define secondary succession, the mean Ellenberg indicator values for light and nitrogen in the herb layer, weighted for coverage, as well as the percentage of climax tree species in naturally regenerated stands were used. All species and genotype diversities based on the investigated tree species were calculated by the so-called Hill numbers. The results showed that the Gregorius's Covariation (C) of secondary succession with the transspecific genotype diversity as well as the transspecific genotype diversity per species for the enzyme systems AAT, HEK, PGI, MDH, IDH as well as the AFLP trait was statistically significant in several relationships. The transspecific genotype diversities were often significantly greater in the earlier successional stages than in the later stages. Selection effects during replacement of light and nitrogen demanding species and plant communities by more economical and competitive species such as Abies alba Mill. and Fagus sylvatica L. probably dominated in the study. Based on the results of the study, we conclude that genetic diversity may be an essential attribute of stages of secondary succession that should be further explored because of its relation to adaptability and ecological stability.

2

The permutation test for testing the statistical significance of the power spectrum estimation in dendrochronological analysis

Krawczyk A.

Geochronometria

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2010

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Vol. 36

23-29

EN

The study presents a proposal of application of the statistical permutation test, known from other applications, for searching for the symptoms of cyclicity, in particular related to solar activity, in the annual growth sequences of trees. The test consists in generation of random sequences of the increment widths observed and comparison of their periodograms with the periodogram of the sequence analysed. This allows for evaluation of the significance of the individual frequencies in the total variability. The model calculations carried out indicate that in the studies on cyclicity in dendrochronological sequences satisfactory results could be obtained in the analysis of sets of the individual sequences (but not the chronologies produced from them). It is important to generate sufficiently high numbers (1000 and more) of random sequences and to apply relatively low significance levels (at 0.05, or even 0.01).

3

Statistical testing of microstructure differences

Klebanov L., Lechnerova R., Slamova M., Slama P., Benes V.

Inżynieria Materiałowa

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2008

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Vol. 29, nr 4

181-184

EN

In materials microstructures including particles the aim is to provide a statistical test whether two microstructures are different or not. The information included can be related to individual particle parameters as well as to their spatial distribution and intensity. Since in classical statistical testing the assumption of independence of observations is necessary which is not fulfilled here, we develop a new test based on TV-distances in probability theory. Using the measurement from a few of windows we consider a multidimensional two-sample test where each parameter of each particle corresponds to one dimension. According to the theoretical background of M-distances this situation can be converted to a univariate two-sample test. We present an application which consists in a comparison of metallographic samples of aluminium alloys.

PL

Celem pracy jest opracowanie testu statystycznego pozwalającego stwierdzić, czy dwie mitostruktury materiałów zawierających cząstki są różne czy nie. Test oparty na 7V-odległościach w teorii prawdopodobieństwa został opracowany na podstawie informacji na temat cech charakterystycznych cząstek z kilku ramek pomiarowych. Jego zastosowanie pokazano na mikrostrukturze cienkiej folii wykonanej ze stopu Al-Mn (rys. 1 i 2). Dokładny skład chemiczny badanego materiału podano w tabeli 1. Histogramy podstawowych charakterystyk (powierzchni przekrojów cząstek) przedstawiono na rysunku 3. Średnia powierzchnia i liczba obserwowanych przekrojów znajdują się w tabeli 2. Następnie został przeprowadzony nowy test o hipotezie zerowej zakładającej, że dwa zbiory danych obserwowane w ramkach pomiarowych należą do tej samej iriikrostruktury (rys. 4). Tabela 3 obejmuje wartości p dla tego testu, gdy rozpatrywane są trzy parametry jednocześnie oraz indywidualnie: powierzchnia, średnica równoważna i wskaźnik kształtu. Można wnioskować, czy hipoteza zerowa jest odrzucana, czy nie, i interpretować wyniki dla różnych materiałów.