Global Boundary Lines of N2O and CH4 Emission in Peatlands
Predicting N2O (nitrous oxide) and CH4 (methane) emissions from peatlands is challenging because of the complex coaction of biogeochemical factors. This study uses data from a global soil and gas sampling campaign. The objective is to analyse N2O and CH4 emissions in terms of peat physical and chemical conditions. Our study areas were evenly distributed across the A, C and D climates of the Köppen classification. Gas measurements using static chambers, groundwater analysis and gas and peat sampling for further laboratory analysis have been conducted in 13 regions evenly distributed across the globe. In each study area at least two study sites were established. Each site featured at least three sampling plots, three replicate chambers and corresponding soil pits and one observation well per plot. Gas emissions were measured during 2–3 days in at least three sessions. A log-log linear function limits N2O emissions in relation to soil TIN (total inorganic nitrogen). The boundary line of N2O in terms of soil temperature is semilog linear. The closest representation of the relationship between N2O and soil moisture is a local regression curve with its optimum at 60–70 %. Semilog linear upper boundaries describe the effects of soil moisture and soil temperature to CH4 best.
The global N2O boundary lines revealed a striking similarity with the Southern German N2O boundary lines, as well as with analogous scattergrams for Europe (Couwenberg et al. 2011) and Southern Queensland (Wang and Dalal 2010). This suggests that local rather than global conditions determine land-use-based greenhouse gas emissions.
Further work will analyse relationships between the environmental factors and the spatial distribution of the main functional genes nirS, nirK and nosZ regulating the denitrification process in the soil samples currently stored in fridge at −18°. An additional analysis will study the relationships between the intensity of CH4 emissions and methanogenesis-regulating functional genes mcrA, pmoA and dsrAB.
KeywordsBog Ecosystem Fen Histosol Hydromorphic Landscape Methane Microbiology Mire Nitrous oxide Organic soil
This study was supported by the IAEA’s Coordinated Research Project (CRP) on “Strategic placement and area-wide evaluation of water conservation zones in agricultural catchments for biomass production, water quality and food security”, the Ministry of Education and Science of Estonia (grant SF0180127s08), the Estonian Research Council (grant IUT2-16); and the EU through the European Regional Development Fund (Centre of Excellence ENVIRON). We are sincerely grateful to the assistance of Mr. Charles Kizza Luswata in the selection of study sites. Our work benefitted from the contribution of Prof. Jaak Truu, Dr. Marika Truu, Mrs. Teele Ligi and Mr. Kristjan Oopkaup to the perspective microbiological study.
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