 |
| Titel |
Impact of dry-wet cycle and flooding on redox dynamics and carbon cycling in a northern fen |
| VerfasserIn |
Cristian Estop, Klaus-Holger Knorr, Christian Blodau |
| Konferenz |
EGU General Assembly 2011
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250053487
|
|
|
|
|
|
| Zusammenfassung |
| Peatlands are quantitatively important carbon-storing terrestrial ecosystems where peat
develops due to the rate of C input (organic matter as litter) surpassing that of C output (gas
efflux and leaching) as plant biomass decomposes. High water contents are an important
factor controlling such C balance in these soils since water does not limit plant growth while
keeping peat in a reduced state thus lowering peat degradation rate. A predicted effect of
current climate change is the potential alteration in the hydrological regime due to
extreme rain events, extended dry periods as well as floodings. Thus, water table (WT)
fluctuations are expected to influence redox processes and carbon cycling in peat
soils.
We investigated redox dynamics, respiration and transport processes in peat profiles
during manipulation of WT at ecosystem scale in a small fen located in a forested area of
North Bavaria (Germany) and compared them to natural WT fluctuations. The experimental
design consists on two treatments; WT was manipulated in one and it was not in the other.
Three spatially high resolved peat profiles were investigated during 2 consecutive seasons for
each treatment. An extended drought and subsequent rewetting during the first season and a
flooding event during the second one were carried out. Gas (O2, CO2, CH4) and pore water
(redox sensitive species) concentrations as well as soil moisture and temperature
allowed gaining insight into spatio-temporal gradients related to WT fluctuations and
seasonality.
Our results indicate that dry events take place seasonally leading to shifts in the peat
redox state. As peat becomes drier when WT drops, the diffusive transport is affected leading
to oxygen penetration, methanogenesis reduction or inhibition, loss of stored CO2 and
suppression of Fe(III) and sulphate reduction processes in the profile. This pattern is
magnified as observed from the reinforced drying in the first season and it is inverted as WT
recovers and is kept high. Calculations and peat depth incubations indicate that
most CO2 and CH4 production takes place in the upper peat layers thus resting
importance to the intensity of the WT drop regarding CO2 emissions in this site.
Nevertheless, the intensity of the WT drop is important regarding the renewal of the
electron acceptor pool, greater due to the reinforced drying. The long lag time phase
observed for CH4 concentrations recovery after the dry event indicates that no CH4
emissions are expected in this system if such intense dry events seasonally occur. |
|
|
|
|
|
|