GreenHouse Gas Flux Measurement From Rewetted and Drained Fen Peatland Cultivated with Reed Canary Grass

Abstract

Natural peatland are efficient ecosystems in storing carbon and serve as a net sink of atmospheric CO2. However, drainage and use of peatlands for agriculture and forestry may turn these natural ecosystems into net sources of CO2 as the peat degradation is accelerated due to processes such as increased soil aeration, fertilization and priming of soil organic carbon turn-over by root exudates. Thus, many studies have documented a high net emission of CO2 from drained peatlands used for annual arable crop production. As we know peatland covers only 3% of earth’s land surface but stores (15-30) % of world’s soil carbon as peat. Therefore, it is of paramount importance to monitor of the amount of greenhouse gas emissions from peatland to control Global warming and climate change.

This thesis is based on the research experiment conducted on fen peatland located in Nørre Å river valley, Denmark (44˚N, 56˚W, 96˚E). The main objective of the thesis project was to compare the emission of greenhouse gases from rewetted and drained fen peatland. Rewetted peatland is a land where water is again put back into it after the land has been utilized for agricultural purposes to restore the natural properties of peatland whereas peatland from which water has been drained out for agricultural purposes or peat extraction is a drained peatland. This experiment was carried out on four random plots where each plot consists of two sub plots. In each sub plot, one half was flooded with water while the other half was kept dry. Gas sample was collected from each sub plot consisting of wet and dry parts by an in line infra-red gas analyzer (IRGA) and opaque chamber method. After the gas was collected, it was then taken to the laboratory for analysis.

The results of the experiment were clear and comprehensible except for fluxes which are due to human error or some sudden change in the soil properties. It is obvious that drained peatland released a higher amount of CO2 than the wet peatland. Drained peatland (unflooded) released 31.25 % more CO2 in average than the rewetted (flooded) one. Similarly, wet part released 81.25 % more N2O in average than the dry part. Likewise, wet plot released 96.66% more CH4 than dry one. Here, one can be easily misguided by the results of CH4 and N2O emission, but they are emitted in a minuscule amount, which is in the order of (milligram) compared to CO2, which is in (gram) The average total GHG emission from the dry part is 16.012 g (16 g (CO2) + 0.01 g (CH4) + 0.002 g (N2O)), whereas from the wet part is 11.308 g (11 g (CO2) + 0.3 g (CH4) +0.0085 g (NO)). This clearly shows that GHG emission from the dry part is higher than the emission of wet part.