Northern Peatlands and their Feedback to Climate Change: A microcosm study to evaluate the effect of temperature increase and water-table drawdown on the emission of greenhouse gases from a Danish Raised Bog: A microcosm study to evaluate the effect of temperature increase and water-table drawdown on the emission of greenhouse gases from a Danish Raised Bog

Nazia Tabassum

Studenteropgave: Speciale

Abstrakt

Northern peatlands are considered crucial components in the global carbon (C) budget as well as in the global budget of greenhouse gases (GHGs) like carbon dioxide (CO2) and methane (CH4). These ecosystems have accumulated a large amount of atmospheric C over the Holocene and acted as a sink of atmospheric CO2 on a long term but as a source of CH4 on short time horizons. But the biogeochemical processes associated with the ecosystems’ C and nitrogen (N) cycling can be significantly affected by the climatic factors- temperature and evapotranspiration. Consequently the function as CH4 source and as CO2 sink is also temperature and water level dependent. The increased air temperatures and evapotranspiration due to climate change, are therefore, frequently assumed as significant external climate forcings that can alter the GHG emission levels in northern bogs that are originally adapted to a more cold and humid climate. With a view to understand the impact of increased air temperatures and water level reductions on a northern bog’s CH4 and CO2 emission levels, the current project conducts a laboratory experiment where 16 semi-intact peat core samples differentiated by high water (HW) and low water (LW) levels and 3 intact background core samples are incubated at three different temperature levels: 4℃, 17℃ and 25℃. Soil samples are collected from a Danish raised bog called Holmegaard and the experiment covers a total period of 28 days. The underlying assumption of the experiment is higher temperature will cause higher CH4 and CO2 fluxes but lower water table will cause lower CH4 and higher CO2 fluxes. At 4℃ temperature, CH4 emissions are considerably low in semi-intact cores than the intact-cores. At 17℃, LW cores have produced more CH4 and CO2 emission than the HW cores. At 25℃ both CH4 and CO2 fluxes have increase but the emission of LW cores are still higher than the HW cores. Compared to the expected range of emission at high temperatures, the CH4 and CO2 flux obtained have been low. Based on the flux data no significant trend of change in the CH4 and CO2 emissions with increased temperatures and reduced water levels can be derived due to the limited number of samples and length of measurement time. Finally, sectors of further studies are recommended based on the outcomes and limitations of the project.

UddannelserMiljørisiko, (Bachelor/kandidatuddannelse) Kandidat
SprogEngelsk
Udgivelsesdato10 aug. 2018
VejledereLauren Paige Seaby & Gary Thomas Banta