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Ecophysiological characteristics of key members of Betaproteobacteria in freshwater bacterioplankton
KASALICKÝ, Vojtěch
This thesis primarily focuses on one segment of freshwater Betaproteobacteria, the Limnohabitans genus (including the RBT lineage). As opposed to other recent research directions, the major aim was to recover the members of the previously uncultured RBT lineage through their isolation from various freshwater habitats. However, the results presented in this thesis have also ambitions to go far beyond the taxonomic descriptions only; the dissertation intends to contribute significantly to unveiling of important ecophysiological characteristics of the studied lineage in a set of both laboratory and field research. Therefore, understanding of growth characteristics, mortality, diversity and life strategies of aquatic microbes is of highest importance regarding profound human impact on water quality and increasing need of drinking water supplies.
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An experimental study of initial succession on different substrata: analysis of changes in plant species cover and some soil biological parameters and their relationships
KRESÁČ, Martin
A four year experimental study of initial stages of succession on different substrata (sand, peat and gray clay overburden from brown coal mining) was carried out. The substrata were transplanted into two different landscape types in the Czech Republic. Control plots were filled with autochthonous topsoil treated with high temperature vapor. Plots with un-treated autochthonous topsoil were also established. Plant species cover and several soil-biological parameters (soil microbial biomass, basal soil respiration, exchangeable pH(KCl), organic-C extractable by potassium sulfate solution, and nitrate-N content) were measured once a year. Obtained data were mainly processed by unimodal (plant cover data) and liner (soil-biological data) ordination methods. Biological species traits (life span, seed dispersal vector, seed bank type, ecological strategy type following Grime, life form following Raunkiaer) were used to characterize early stages of plant succession. Vegetation and measured soil-biological parameters, except pH(KCl), were significantly changing during four growing seasons. Variance partitioning analysis based on plant species cover data indicated the landscape type to be the main governing factor and physico-chemical characteristics of substrate to be less important during the studied initial stages of succession. The same analysis based on soil-biological parameters showed the reverse result. Great variability of plant species ecological traits was noticed during four growing seasons. The earliest plant colonizers were mainly ruderal, anemochorous terophytes with persistent seed bank. The number of species with C-strategy type increased during the study. The relationship between the average plant species cover and measured soil-biological parameters was also examined during the experimental study of early succession. Direct and indirect ordination revealed the average sum of plant species cover to be weakly positively correlated with soil microbial biomass, basal soil respiration, nitrate-N, potassium sulfate extractable organic-C, metabolic quocient (qCO2) and negatively correlated to exchangeable pH(KCl). The relationship was significant only in the case of microbial biomass and potassium sulfate extractable organic-C. More detailed studies of the relationship between aboveground plant species biomass and soil microbial communities in initial stages of succession are required. Comparability of presented study is limited because not many experimental investigations of similar kind have been presented until now.
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