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Role of plants in the greenhouse gas budget of a sedge fen
NOVOTNÁ, Jitka
Wetlands play an important role in the global carbon cycle because they fix or release carbon dioxide (CO2) and are a source of atmospheric methane (CH4). The dynamics of the exchange of these greenhouse gases is determined mainly by the height and dynamics of water level, temperature and vegetation structure and biomass. The aim of this study was to evaluate the effect of plants with a dominant sedge, Carex acuta, on CO2 and CH4 emissions from a sedge fen on a model site ?The Wet Meadows? near Třeboň. This study included field research using a method of manual emission chambers in order to monitor the differences in the emissions between hummocks with vegetation and hollows without vegetation. In addition, aboveground plant biomass, water level and temperature were followed. The field research was supplemented with a mesocosm experiment in which the influence of water regime on C. acuta biomass production was evaluated. The results of the field research show that water level had a significant effect on CO2 emissions only in the hollows. Soil temperature was an important factor on both micro-sites. The presence and biomass of the plants had a substantial effect on the amounts of CO2 emissions, but only in the second part of the vegetation season, when the plant aboveground biomass reached its seasonal maximum. CH4 emissions were significantly influenced by the water level and its previous dynamics but not by temperature. An important factor was also the presence of sedge hummocks, which vented considerable amounts of CH4 into the atmosphere when their basal parts were flooded. Fairly small amounts of CH4 were mediated by the plants at water levels between -20 cm and the soil surface. A conceptual model has been created for the conditions of 2014 in order to estimate the effect of the C. acuta dominated vegetation of the hummocks on carbon emissions and its balance. The carbon assimilation into plant biomass exceeded not only the carbon emissions mediated by the plants, but also the emissions from the whole hummocks. Approximately 130 g C m-2 per vegetation season was stored into the soil owing to the plants. The mesocosm experiment indicated that the plants of C. acuta formed the greatest belowground biomass as well as total biomass in the limosal ecophase followed by the plants subjected to a spring flood.
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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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Effect of flooding régime on the growth of Carex acuta in a mesocosm experiment
JANUŠ, Vojtěch
This MCs thesis is part of the Grant Agency of Czech Republic GACR P504/11/1151 The role of plants in bilance of greenhouse gases in Carex fens. The results of this project will serve as a basis for another analyses of greenhouse gases in natural wetland biotops. Growth and morphological changes of Carex acuta were monitored in mesocosm experiment durig the growing seson. Carex acuta has already been the subjekt of numerous studies. The aim of this study is to compare the growth rate of plants C. acuta grown under controlled conditions, simulating different regimes of flooding habitat. Number of shoots and maximum plant height were observed during the growing season. Destructive method has been used to fall aboveground and belowground biomass in autumn. Elevated water levels in the middle of the growing season caused a slowdown in growth in height and the creation of new shoots. Reduced water level of the mid-growing season seemed to faster growth of plants in height. Underground biomass significantly negatively affected by increased water level in the middle of the growing season.
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Dynamics of aboveground biomass of a sedge fen
HAŠEK, Ladislav
This thesis is part of Project of the Grant Agency of the Czech Republic No P504/11/1151, focused on the role of plants in the balance of carbon dioxide and the other greenhouse gases produced in the ecosystem of a sedge fen, which is situated on the study site Wet Meadows near Třeboň. The thesis deals with the growth dynamics of the dominant sedge, Carex acuta. The samples were taken using the method of successive harvests near the automatic meteorological station of Czech Globe, Academy of Sciences of the Czech Republic. During the growing season nine harvests were accomplished on 25.3, 15.4, 6.5, 5.6., 9.7., 5.8., 9.9., 21.10., 25.11.. On each date eight replicates were taken, i.e., a total of 72 samples within the vegetation season. The seasonal dynamic of the above ground biomass was compared between C. acuta and the other plant species on the experimental area. Both live and dead biomass, was harvested and subsequently sorted to single botanic species, dried, weighed and the values were processed using the MS Excel tables. The seasonal maximum of aboveground biomass of all plant species (both live and dead parts) was found on 9.7. (1452,72 g.m-2). Among plant species the highest values of aboveground biomass were attained by Calamagrostis canescens (1257,93 g.m-2) and C. acuta (1163,49 g.m-2). C. acuta displayed the highest density of all shoots on 15.4 (300 m-2),and the highest average weight of one shoot. The maximum length of the longest live shoot of Carex acuta was very consistent among the measurememnts.
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Effects of nutrients and water level on \kur{Phalaris arundinacea} growth
KÁPLOVÁ, Miroslava
This thesis is an extension of my Bc. thesis. Based upon previously conducted research in a wet grassland, Mokré Louky, near Třeboň, Czech Republic, a mesocosm experiment was designed for investigating the effect of two nutrient regimes (non fertilized / fertilized) and three flooding regimes (saturated / spring flood / flooded) on Carex acuta and Phalaris arundinacea plants to determine the effect of management type for restoring a more diverse wet meadows system.
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Effect of mineral nutrient availability and flooding on the growth of Carex acuta in a mesocosm experiment
SYCHROVÁ, Jana
This MSc thesis is part of the project GACR 526/09/1545 Importance of newly assimilated carbon for the plant-soil interactions in wet grassland ecosystems in varying environmental conditions, which focuses on the effects of eutrophication on selected wet meadows with mineral or organic soil in the Trebon Biosphere Reserve. The results of this project will serve as a basis for developing a suitable ecosystem management for wet meadows, especially for sites registered as nature reserves. Pot experiments were carried out with Carex acuta, a dominant species of wet meadows that has already been subject of many studies. The aim of this work was to find out how C. acuta responds to different levels of fertilization and soil flooding under controlled conditions. The growth of the generative shoots of C. acuta was significantly affected by fertilization. The growth of vegetative shoots was significantly influenced by the soil organic matter content and fertilizer addition. The vegetative shoots reached greater length than the generative shoots. The pot experiment indicates that fertilization has not a large influence on the growth of C. acuta. This finding may explain field observations that C. acuta is gradually replaced in eutrophic habitats by stronger competitors, especially Phalaris arundinacea.
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Aboveground production of a wet meadow stand dominated by Carex acuta
KUNCOVÁ, Štěpánka
The MSc thesis is part of the project of Ministry of Environment of the Czech Republic entitled Czech Terra, which aims at assessing the carbon budget and cycle in the main types of ecosystems in the Czech Republic. This thesis is focussed on the production of aboveground biomass of Carex acuta, which dominates the unmanaged and permanently flooded part of the Wet Meadows. The seasonal dynamics of aboveground plant production was followed using a series of 9 destructive harvests during the vegetation season. On each date, four 0.5x0.5m2 samples were taken from the wetter, and four samples from the drier part of the stand. The maximum value of live biomass of C. acuta (550.8 g.m-2) was recorded on 13.6 2008. The highest value of live biomass of all species reached 602.4 g.m-2. The maximum total biomass (without litter) reached 994.6 g. m-2. The highest value of productivity of C. acuta (12.46 g.m-2.day-1) was recorded on 24. 5.
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Effect of mineral fertilization on photosynthetic characteristics of Carex acuta
LESKOVCOVÁ, Martina
The MSc. thesis "Effect of mineral fertilization on photosynthetic characteristics of Carex acuta" deals with photosynthetic characteristics of plants subjected to different nutrient regimes. Stands dominated with Carex acuta were studied din two localities: Záblatské louky with organic soil and Hamr with mineral soil. The experimental treament was subjected to high fertilization, while the control treatment received no nutrient addition. The net assimilation was measured using Licor 6400. The aim was to find out whether the net assimilation was higher in fertilized plants as compared with non-fertilized plants. In spring the fertilized plants did not have higher photosynthetic rates at either locality, probably because of water limitation. The positive effect of fertilization was proved only at Hamerské louky after the second cut.
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