Verlässliche Abschätzung von CH4-Bilanzen für Ökosysteme auf der Basis der Extrapolation von Punktmessungen unter Benutzung von Vegetationsmustern und weiteren Umweltparametern
Final Report Abstract
Gas fluxes and matter balances of ecosystems are of crucial importance for the evaluation of the climate impact of land use under predicted climate change. Closed chamber (CC) and eddy covariance (EC) measurements are the two most widely used methods to assess greenhouse gas (GHG) emissions from ecosystems. CC measurements exhibit a considerable spatial and temporal variability caused by the phenological development (temporal variability) and by the spatial variability of the vegetative cover and their associated micro-organism communities. We planned to use the vegetation composition of a degraded, rewetted, brackish fen - together with continuous maps of relevant environmental parameters - as a proxy to extrapolate CC measurements of CH4 flux rates to obtain reliable CH4 emission estimates for the ecosystem/ habitat scale. However, albeit we already reached important milestones of the original proposal, we are just not there yet. But we are on the way: We investigated the influence of plant species on methane emissions before rewetting by flooding and found a significant influence of the dominating plant species. When the area was flooded because a ground sill had been installed at the outflow of the catchment in late 2009, the ecosystem collapsed, leading to substantial die-back of vegetation and change in ecosystem properties, including a 100-fold increase in average annual methane emissions, considerable change to pore water and peat chemistry and a dramatic decrease in ecosystem respiration (RECO) and canopy photosynthesis (CP). This is of major importance for future rewetting projects. In the following, the system stabilized slowly, expressed by a constant, asymptotic decrease in methane emissions and a fast succession of vegetation, indicating a relatively adaptation of the ecosystem. Under the new ecosystem conditions, rather representing a shallow lake than a peatland, spatial variability of methane emissions is very high, even when only stands with Phragmites australis are considered although the flooded conditions would rather suggest a smoothing of environmental variability. Unfortunately, species composition has no direct link to the annual methane emission estimates rendering reliable upscaling extremely difficult.
Publications
- (2011) Maßnahmen zur Minderung der Treibhausgasfreisetzung aus Mooren im Mittleren Mecklenburg. Telma Beiheft 4:85–106
Glatzel S, Koebsch F, Beetz S, Hahn J, Richter P, Jurasinski G
- (2013) CO2 exchange of a temperate fen during the conversion from moderately rewetting to flooding. Journal of Geophysical Research - Biogeosciences 118:940–950
Koebsch F, Glatzel S, Hofmann J, Forbrich I, Jurasinski G
(See online at https://doi.org/10.1002/jgrg.20069) - (2013) Vegetation controls methane emissions in a coastal brackish fen. Wetlands Ecology and Management 21:323–337
Koebsch F, Glatzel S, Jurasinski G
(See online at https://doi.org/10.1007/s11273-013-9304-8) - (2014) Spatial variability of methane emissions in a Phragmites australis (Cav.) Trin. ex Steud. dominated restored coastal brackish fen. Wetlands 34:593–602
Koch S, Jurasinski G, Koebsch F, Koch M, Glatzel S
(See online at https://doi.org/10.1007/s13157-014-0528-z) - Controls for multi-scale temporal variation in ecosystem methane exchange during the growing season of a permanently inundated fen. Agricultural and Forest Meteorology, Volume 204, 15 May 2015, Pages 94-105
Koebsch F, Jurasinski G, Koch M, Hofmann J, Glatzel S
(See online at https://doi.org/10.1016/j.agrformet.2015.02.002)
