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Ecophysiology of photosynthesis of wetland grasses
MEJDOVÁ, Markéta
The wetland ecosystems play an important role in the global carbon cycle. The individual processes of carbon (C) exchange and sequestration of vegetation are studied using different approaches and methods. Using by the photosynthesis light curves can be determined parameters of photosynthesis (Pmax -maximum rate of photosynthesis, Icomp- compensation point, Rd- dark respiration, - maximum quantum yield) of individual plant species. Knowledge of these parameters will allow us to understand what role plants play in the processes of C exchange and sequestration. The main goal of this work was to determine the parameters of the photosynthesis light curve of dominant plant species in the sedge-grass marsh stand of Mokré louky near to Třeboň town. Further to evaluate whether the investigated plant species differ in individual photosynthetic parameters and whether they are affected by environmental conditions. The work took place during the vegetation period of 2013 at weekly intervals. Vegetation mapping was performed also in 2013 and consequently in 2017. For a comprehensive knowledge of the ecosystem, the production characteristics of the investigated plant species and the determination of the big-leaf parameters of the light curve for whole ecosystem. Estimated carbon uptake by the hypothetical big-leaf was compared with net ecosystem exchange (NEE) measured by eddy-covariance (EC) system. The investigated plant species differed significantly in the Pmax parameter and can be divided into three groups according to it. The first group with the highest average value of Pmax includes Glyceria maxima (18.36 ?mol m-2 s-1) and Acorus calamus (16.61 ?mol m-2 s-1). The second group includes Carex acuta (10.83 ?mol m-2 s-1) and Phalaris arundinacea (9.41 ?mol m-2 s-1). And in the third groups with the lowest average value of Pmax includes Calamagrostis canescens (7.02 ?mol m-2 s-1). Pmax was higher in early summer and then gradually decreased. Higher Rd was observed, for example, at the beginning of the growth season; after the flood and especially at the end of the growing season. The Pmax was significantly affected by water level fluctuations in Phalaris arundinacea and Calamagrostis canescens. The Pmax in Phalaris arundinacea was also significantly affected by the June floods. The conductivity of the stomata did not affect the Pmax parameter, but was significantly affected by the water level in all examined plant species. During vegetation mapping in 2013, the following relative representation of individual plant species was processed: Phalaris arundinacea 35 %, Carex acuta 28.6 %, Glyceria maxima 16.5 %, Acorus calamus 1.2 %, and Calamagrostis canescens 18.7 %. Rate of Pn and NEE had a similar seasonal course (R2=0,859 - 0,998), but Pn reached higher values than NEE measured by EC method.
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Turnover of aboveground biomass of the dominant of a sedge fen
MEJDOVÁ, Markéta
Annotation This thesis is part of Project of the Grant Agency of the Czech Republic No. P504/11/1151 (Role of plants in the greenhouse gas budget of a sedge fen) aims at estimating the turnover of aboveground biomass of Carex acuta L. in a flooded part of the Wet Meadows near Třeboň. The biomass turnover was estimated using both destructive and non-destructive types of measurement and was assessed separately for generative and vegetative tillers, which markedly differ in their life cycles. Vegetative tillers last throughout the vegetation season. Generative tillers have a fast development at the beginning of the vegetatin season but die out soon after seed development. They disapper from the stand in mid-July. Vegetative shoots reached their maximum aboveground biomass at the end of June. The average dry weight of all leaves produced so far was 1,51 g per tiller and the average dry weight of all aboveground biomass produced per tiller was 2,28 g. The turnover coefficient was 1,39 year-1 and 1,01 year-1 for leaves and whole tillers, respectively. Also generative shoots reached their maximum aboveground biomass at the end of June. The average dry weight of aboveground biomass produced so far was 1,95 g per tiller. The turnover coefficient was 1, 38 year-1and 1,10 year-1.
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Turnover of aboveground biomass in a dominant species of a wet meadow
MEJDOVÁ, Markéta
This Bachelor{\crq}s Thesis is a part of the SP/2d1/93/07 (Czech Terra) project of the Department of Environment, which is focused on an assessment of carbon cycle and carbon balance in selected ecosystems of the Czech Republic. Within this project there is assessed production of aboveground biomass of wetland vegetation in the location of Mokrá luka (Wet Meadow) near Třeboň. In the presented Bachelor{\crq}s Thesis I focus on documentation of conversion of aboveground biomass of tulfted sedge (Carex acuta L.), which represents a dominant of the flooded part of Wet Meadows. My thesis consisted in non-destructive observation of aboveground biomass accumulation in selected humps, during which I assigned dry mass value to tillers growing in these humps on the basis of an analogy with parallel samples. At the selected tillers I observed dynamics of leaf growth during vegetative season, their drying up and falling. In this thesis I also deal with the differences in growth dynamics at generative and vegetative tillers. During their growth the generative tillers had on average only three leaves; in total they had on average seven leaves, which means that four leaves started to grow in previous autumn. Since seeding the leaves were dieing and the last live ones were observed on 13 August. During August and at the beginning of September the leaves started to fall more. At vegetative tillers the number of leaves during the growth period increased. At the beginning of measurement of these dynamics (4 June) the tillers had on average 10 leaves, from which three were from the previous autumn; by September their number increased to 14. During the growth period the tiller had 5-6 photosynthetic active leaves. The leaves fell more slowly than at generative tillers.
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