1 |
Methane and carbon dioxide fluxes in created riparian wetlands in the midwestern USA: Effects of hydrologic pulses, emergent vegetation and hydric soilsAltor, Anne E. 06 June 2007 (has links)
No description available.
|
2 |
Arctic Soils in a Warming Climate: Plot-scale Changes of CO2 Fluxes after Five Years of Experimental Warming.Schröer, Cosima January 2020 (has links)
Terrestrial arctic ecosystems store large amounts of carbon (C). With global warming, this C might be released into the atmosphere as CO2 by stimulation of soil microbial degradation. At the same time, CO2 uptake in plants is enhanced, which might, in parts, offset CO2 losses. Yet, the future balance of these two contrasting feedbacks remain uncertain. This study aimed to better understand changes of input and output CO2 fluxes in an arctic tussock tundra ecosystem in response to global warming, with a special focus on the contrast between two sub-ecosystem habitats, the tussocks and the space between tussocks. An experimental setup was used, where snow fences simulated winter warming by increasing snow depth, and open top chambers simulated summer warming. Daytime ecosystem respiration (ER), reflecting the outward CO2 flux, gross ecosystem production (GEP), reflecting the inward CO2 flux, and net ecosystem exchange (NEE), reflecting the net balance of both, were measured in the summer 2019 in the tussock and the intertussock habitat. In the tussock, both ER and GEP were as twice as high compared to the intertussock and increased with summer warming in a similar magnitude, resulting in an unchanged NEE. Fluxes in the intertussock were not altered with summer warming. Winter warming had no significant effects on ER and GEP in neither of the habitats. However, winter warming increased NEE and green biomass in the intertussock, indicating that in this habitat, plants benefit from warmer winter soil temperatures. Interaction effects of winter and summer warming underline the role of ecological processes outside the summer season, which are to date poorly understood. Contrasting responses of the two sub-ecosystem habitats highlight the challenges in predicting future C balances that are caused by small-scale spatial and temporal heterogeneity of C dynamics.
|
3 |
CARBONDIOXIDE FLUXES FROM A CONTROLLED BOREAL RIVERARTHUR, FRANK January 2018 (has links)
River, lakes and streams account for more carbon dioxide emissions than all other freshwater reservoirs together. However, there is still lack of knowledge of the physical processes that control the efficiency of the air-water exchange of CO2 in these aquatic systems. In the more turbulent water sections of a river, the gas transfer is thought to be governed by the river’s morphology such as bottom topography, slope and stream flow. Whiles for wider sections of the river, the gas transfer could potentially be influenced by atmospheric forcing (e.g. Wind speed). The main purpose of this project is to study the fluxes of carbon dioxide and how (wind speed and stream discharge) influence the CO2 fluxes in the river. In this study, direct and continuous measurements of CO2 emission was conducted for the first time in a controlled boreal river in Kattstrupeforsen (Sweden) from 18th April to 10th May 2018. A unique measurement setup which combines eddy covariance techniques, general meteorology and in situ water variables (for high accuracy emission measurements) was used. The results show that in the late winter, an upward directed CO2 fluxes measured in the river was approximately 2.2 μmol m−2 s−1. This value agrees with many other small and large rivers where CO2 fluxes has been studied. The river can be said to serve as source of CO2 to the atmosphere in the day due to the dominant upward fluxes recorded during the daytime. The results also show that carbon dioxide fluxes increase with increasing wind speed notably at wind speed above 2 m s-1. There was no relation between CO2 fluxes and stream discharge. This indicates that wind speed could be one principal factor for air- river gas exchange. The findings in this work on river gas exchange will provide a basis for a regional estimate and be applicable for many river systems on a global scale. / <p>2018-07-09</p>
|
Page generated in 0.0521 seconds