Factors controlling the release of dissolved organic substances, their stability and impact in methanogenic inundated fens soils
Final Report Abstract
Excessive supply of nutrients is known to threaten nutrient limited peatlands. In this project bog and fen systems were investigated from the molecular to mesocosm scale. The nutrient enrichment of both systems either by internal eutrophication due to long-term drainage and agricultural use or by external loading triggered vegetation changes and altered microbial respiration processes. Labile litter of vascular plants was the primary carbon source for high respiratory activity and methanogenesis. Decomposed fen peat also contained lower amounts of polyphenols and condensed tannins – as potentially inhibitory compounds for decomposition. Surprisingly, fertilized and nutrient enriched litter of Juncus effusus did not decompose faster compared to nutrient poor litter, neither did nutrient enrichment in the pore water per se increase decomposition of peat. Rewetting or inundation of fens and bogs successfully halted aerobic decomposition and thus preserves the carbon stock of these sites. High CH4 emissions may partly offset this reduction in CO2 emissions; however, such high CH4 emissions seem to be a temporary phenomenon, also in rewetted fens. Top soil removal could provide a suitable measure to reduce the amount of biomass and labile litter formed after rewetting, and thus greatly reduce CH4 emissions. Interestingly, presence of aerenchymatic vegetation may not necessarily increase CH4 emissions as previously hypothesized but could also lead to an oxidation of the rhizosphere, providing electron acceptors for microbial respiration, suppressing CH4 production or facilitate CH4 oxidation.
Publications
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2015. Changes of the CO2 and CH4 production potential of rewetted fens in the perspective of temporal vegetation shifts. Biogeosciences 12: 2455–2468
Zak, D, Reuter, H, Augustin, J, Shatwell, T, Barth, M, Gelbrecht, J, McInnes, RJ
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2017. Direct Analysis of Lignin Phenols in Freshwater Dissolved Organic Matter. Analytical Chemistry 89: 13449–13457
Reuter, H, Gensel, J, Elvert, M, Zak, D
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2018. Juncus effusus mono-stands in restored cutover peat bogs – Analysis of litter quality, controls of anaerobic decomposition, and the risk of secondary carbon loss. Soil Biology & Biochemistry 117: 139–152
Agethen, S, Knorr, K-H
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2018. Plant rhizosphere oxidation reduces methane production and emission in rewetted peatlands. Soil Biology and Biochemistry 125: 125–135
Agethen, S, Sander, M, Waldemer, C, Knorr, K-H
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2018. Top soil removal reduces water pollution from phosphorus and dissolved organic matter and lowers methane emissions from rewetted peatlands. Journal of Applied Ecology 55: 311–320
Zak, D, Goldhammer, T, Cabezas, A, Gelbrecht, J, Gurke, R, Wagner, C, Reuter, H, Augustin, J, Klimkowska, A, McInnes, R
