Minke M.,APB BirdLife Belarus |
Minke M.,University of Greifswald |
Augustin J.,ZALF e.V. |
Hagemann U.,ZALF e.V. |
Joosten H.,University of Greifswald
Aquatic Botany | Year: 2014
In daylight, methane (CH4) emissions from green Phragmites australis culms are dominated by internal convective through-flow controlled by relative air humidity (RH), air temperature and photosynthetic active radiation (PAR). As shading by opaque chambers may attenuate emissions, it is generally recommended to use temperature-controlled transparent chambers for measuring CH4 emissions. However, experimental data on the actual impact of opaque chambers are contradictory, and full-day measurements integrating the entire range of solar radiation are rare. Moreover, the impact of chamber headspace mixing with fans on measured CH4 fluxes remains to be determined.We conducted high resolution CH4 measurements over 8-24h at two rewetted fen sites with dense reed stands featuring different water depths. Methane emissions were measured with short enclosure times (8-12min) using temperature-controlled transparent chambers and opaque chambers both with and opaque chambers without continuous headspace mixing by fans.The use of transparent or opaque chambers with fans did not lead to significant differences in measured CH4 emission rates. At the deep water reed site, chambers without fans resulted in lower flux estimates compared to chambers with fans, but differences were not significant. Methane emission rates closely reflected changes of PAR, even during drastic and fast changes between clouded and clear skies, indicating that PAR is the dominant factor influencing CH4 flux rates of Phragmites. We explain the contradiction between the high importance of outside PAR and the negligible influence of chamber shading by pressure propagation along horizontal rhizomes connecting non-illuminated culms inside and illuminated culms outside the chamber. For plant species with interconnected gas exchange and pressurization exceeding the boundary of a measurement plot, both opaque and transparent chambers may therefore be used to reliably determine CH4 emission. © 2013 Elsevier B.V. Source
Hahn-Schofl M.,Max Planck Institute for Biogeochemistry |
Zak D.,Leibniz Institute of Freshwater Ecology and Inland Fisheries |
Minke M.,APB BirdLife Belarus |
Gelbrecht J.,Leibniz Institute of Freshwater Ecology and Inland Fisheries |
And 2 more authors.
Biogeosciences | Year: 2011
Peatland restoration by inundation of drained areas can alter local greenhouse gas emissions as CO2 and CH4. Factors that can influence these emissions include the quality and amount of substrates available for anaerobic degradation processes and the sources and availability of electron acceptors. In order to learn about possible sources of high CO 2 and CH4. emissions from a rewetted degraded fen grassland, we performed incubation experiments that tested the effects of fresh plant litter in the flooded peats on pore water chemistry and CO2 and CH4. production and emission.
The position in the soil profile of the pre-existing drained peat substrate affected initial rates of anaerobic CO2 production subsequent to flooding, with the uppermost peat layer producing the greatest specific rates of CO2 evolution. CH4 production rates depended on the availability of electron acceptors and was significant only when sulfate concentrations were reduced in the pore waters. Very high specific rates of both CO2 (maximum of 412 mg C d-1 kg-1 C) and CH4 production (788 mg C d -1 kg-1 C) were observed in a new sediment layer that accumulated over the 2.5 years since the site was flooded. This new sediment layer was characterized by overall low C content, but represented a mixture of sand and relatively easily decomposable plant litter from reed canary grass killed by flooding. Samples that excluded this new sediment layer but included intact roots remaining from flooded grasses had specific rates of CO2 (max. 28 mg C d-1 kg-1 C) and CH4 (max. 34 mg C d-1 kg-1 C) production that were 10-20 times lower than for the new sediment layer and were comparable to those of a newly flooded upper peat layer. Lowest rates of anaerobic CO2 and CH4 production (range of 4-8 mg C d-1 kg-1 C and <1 mg C d-1 kg-1 C) were observed when all fresh organic matter sources (plant litter and roots) were excluded. In conclusion, the presence of fresh organic substrates such as plant and root litter originating from plants killed by inundation has a high potential for CH4 production, whereas peat without any fresh plant-derived material is relatively inert. Significant anaerobic CO2 and CH4 production in peat only occurs when some labile organic matter is available, e.g. from remaining roots or root exudates. © 2011 Author(s). Source
Couwenberg J.,University of Greifswald |
Thiele A.,APB BirdLife Belarus |
Tanneberger F.,University of Greifswald |
Augustin J.,Leibniz Center for Agricultural Landscape Research |
And 7 more authors.
Hydrobiologia | Year: 2011
Drained peatlands in temperate Europe are a globally important source of greenhouse gas (GHG) emissions. This article outlines a methodology to assess emissions and emission reductions from peatland rewetting projects using vegetation as a proxy. Vegetation seems well qualified for indicating GHG fluxes from peat soils as it reflects long-term water level, affects GHG emissions via assimilate supply and aerenchyma and allows fine-scaled mapping. The methodology includes mapping of vegetation types characterised by the presence and absence of species groups indicative for specific water level classes. GHG flux values are assigned to the vegetation types following a standardized protocol and using published emission values from plots with similar vegetation and water level in regions with similar climate and flora. Carbon sequestration in trees is accounted for by estimating the annual sequestration in tree biomass from forest inventory data. The method follows the criteria of the Voluntary Carbon Standard and is illustrated using the example of two Belarusian peatlands. © 2011 Springer Science+Business Media B.V. Source