Transport and thermodynamics constrain belowground carbon turnover in a northern peatland

Beer, Julia; Blodau, Christian

doi:10.1016/j.gca.2007.03.010

Cited by 97 publications

(123 citation statements)

References 64 publications

(75 reference statements)

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“…4b). The constant depth profiles at our sites are in contrast to measurements by Beer and Blodau (2007) in an oligotrophic bog in Canada, who found a strong increase in the upper 65 cm. This latter profile pattern was mainly explained by diffusion.…”

Section: Water Tablecontrasting

confidence: 99%

High soil solution carbon and nitrogen concentrations in a drained Atlantic bog are reduced to natural levels by 10 years of rewetting

Frank¹,

Tiemeyer²,

Gelbrecht

et al. 2014

Biogeosciences

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Abstract. Anthropogenic drainage of peatlands releases additional greenhouse gases to the atmosphere, and dissolved carbon (C) and nutrients to downstream ecosystems. Rewetting drained peatlands offers a possibility to reduce nitrogen (N) and C losses. In this study, we investigate the impact of drainage and rewetting on the cycling of dissolved C and N as well as on dissolved gases, over a period of 1 year and a period of 4 months. We chose four sites within one Atlantic bog complex: a near-natural site, two drained grasslands with different mean groundwater levels and a former peat cutting area rewetted 10 years ago.Our results clearly indicate that long-term drainage has increased the concentrations of dissolved organic carbon (DOC), ammonium, nitrate and dissolved organic nitrogen (DON) compared to the near-natural site. DON and ammonium contributed the most to the total dissolved nitrogen. Nitrate concentrations below the mean groundwater table were negligible. The concentrations of DOC and N species increased with drainage depth. In the deeply-drained grassland, with a mean annual water table of 45 cm below surface, DOC concentrations were twice as high as in the partially rewetted grassland with a mean annual water table of 28 cm below surface. The deeply drained grassland had some of the highestever observed DOC concentrations of 195.8 ± 77.3 mg L −1 with maximum values of > 400 mg L −1 . In general, dissolved organic matter (DOM) at the drained sites was enriched in aromatic moieties and showed a higher degradation status (lower DOC to DON ratio) compared to the nearnatural site. At the drained sites, the C to N ratios of the uppermost peat layer were the same as of DOM in the peat profile. This suggests that the uppermost degraded peat layer is the main source of DOM. Nearly constant DOM quality through the profile furthermore indicated that DOM moving downwards through the drained sites remained largely biogeochemically unchanged. Unlike DOM concentration, DOM quality and dissolved N species distribution were similar in the two grasslands and thus unaffected by the drainage depth.Methane production during the winter months at the drained sites was limited to the subsoil, which was quasipermanently water saturated. The recovery of the water table in the winter months led to the production of nitrous oxide around mean water table depth at the drained sites.The rewetted and the near-natural site had comparable DOM quantity and quality (DOC to DON ratio and aromaticity). 10 years after rewetting quasi-pristine biogeochemical conditions have been re-established under continuously water logged conditions in the former peat cut area. Only the elevated dissolved methane and ammonium concentrations reflected the former disturbance by drainage and peat extraction. Rewetting via polder technique seems to be an appropriate way to revitalize peatlands on longer timescales and to improve the water quality of downstream water bodies.

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Section: Water Tablecontrasting

confidence: 99%

High soil solution carbon and nitrogen concentrations in a drained Atlantic bog are reduced to natural levels by 10 years of rewetting

Frank¹,

Tiemeyer²,

Gelbrecht

et al. 2014

Biogeosciences

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“…2 values derived from Hornibrook et al (2009), Keller and Bridgham, (2007), Küsel et al (2008), and Loy et al (2004). 3 values derived from Beer and Blodau (2007), Billet and Moore (2008), Blodau et al (2007aBlodau et al ( , 2007b, and Shotyk (1997a, 1997b).…”

Section: Biogeochemistry and Electron Acceptorsmentioning

confidence: 99%

Anaerobic oxidation of methane: an underappreciated aspect of methane cycling in peatland ecosystems?

2011

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Abstract.Despite a large body of literature on microbial anaerobic oxidation of methane (AOM) in marine sediments and saline waters and its importance to the global methane (CH 4 ) cycle, until recently little work has addressed the potential occurrence and importance of AOM in non-marine systems. This is particularly true for peatlands, which represent both a massive sink for atmospheric CO 2 and a significant source of atmospheric CH 4 . Our knowledge of this process in peatlands is inherently limited by the methods used to study CH 4 dynamics in soil and sediment and the assumption that there are no anaerobic sinks for CH 4 in these systems. Studies suggest that AOM is CH 4 -limited and difficult to detect in potential CH 4 production assays against a background of CH 4 production. In situ rates also might be elusive due to background rates of aerobic CH 4 oxidation and the difficulty in separating net and gross process rates. Conclusive evidence for the electron acceptor in this process has not been presented. Nitrate and sulfate are both plausible and favorable electron acceptors, as seen in other systems, but there exist theoretical issues related to the availability of these ions in peatlands and only circumstantial evidence suggests that these pathways are important. Iron cycling is important in many wetland systems, but recent evidence does not support the notion of CH 4 oxidation via dissimilatory Fe(III) reduction or a CH 4 oxidizing archaea in consortium with an Fe(III) reducer. Calculations based on published rates demonstrate that AOM might be a significant and underappreciated constraint on the global CH 4 cycle, although much about the process is unknown, in vitro rates may not relate well to in situ rates, and projections based on those rates are fraught with uncertainty. We suggest electron transfer mechanisms, C flow and pathways, and quantifying in situ peatland AOM rates as the highest priority topics for future research.

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“…Following our discussion on decomposition and water flux processes, we could include a deep layer of chemically inert porewater with long residence times (Beer and Blodau, 2007); multiple thin layers, in which water movements and decay are rapid, representing peat pipes in blanket bogs (Holden and Burt, 2003) and possibly tropical peatlands (Walsh and Howells, 1988); a near-surface layer of low permeability representing blockages in pore spaces by bubbles (Beckwith and Baird, 2001;Baird and Waldron, 2003). Ordinal layers could be developed for as many different processes as one's research questions dictated.…”

Section: The Polytelmic (Many-layered) Modelmentioning

confidence: 99%

“…Although threshold changes in space are conveniently represented by the definition of a boundary between discrete layers, some variables exhibit highly continuous variation that is not well captured by two layers. Beer and Blodau (2007) and Beer et al (2008) showed that high porewater concentrations of dissolved inorganic carbon compounds, methane, phenols and other end products of peat decay can slow or even halt decay through thermodynamic limitation of microbial respiration (cf. Conrad, 1999).…”

mentioning

confidence: 99%

“…Conrad, 1999). Beer and Blodau (2007) and Beer et al (2008) postulated that deep layers in thick peat deposits may become effectively disconnected from rainfall due to slow porewater turnover times, allowing decay end products to accumulate in concentrations high enough to halt decay. This theorized deep zone of disconnection provides an example of a situation in which a two-layered scheme would struggle to represent the continuous down-profile variation of interest.…”

mentioning

confidence: 99%

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Conceptual frameworks in peatland ecohydrology: looking beyond the two‐layered (acrotelm–catotelm) model

et al. 2011

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Northern peatlands are important shallow freshwater aquifers and globally significant terrestrial carbon stores. Peatlands are complex, ecohydrological systems, commonly conceptualized as consisting of two layers, the acrotelm (upper layer) and the catotelm (lower layer). This diplotelmic model, originally posited as a hypothesis, is yet to be tested in a comprehensive manner. Despite this, the diplotelmic model is highly prevalent in the peatland literature, suggesting a general acceptance of the concept. We examine the diplotelmic model with respect to what we believe are three important research criteria: complexity, generality and flexibility. The diplotelmic model assumes that all ecological, hydrological and biogeochemical processes and structures can be explained by a single discrete boundary-depth in relation to a drought water table. This assumption makes the diplotelmic scheme inherently inflexible, in turn hindering its representation of a range of ecohydrological phenomena. We explore various alternative conceptual approaches that might offer greater flexibility, including the representation of horizontal spatial heterogeneity and transfers. We propose that the concept of hot spots, prevalent in terrestrial biogeochemistry literature, might be extended to peatland ecohydrology, providing a more flexible conceptual framework. Hot spots are areas of a peatland which exhibit fast processing rates in a number of mechanistically linked hydrological, ecological and biogeochemical processes. The complementary concept of cold spots may also be useful in peatland ecohydrology, particularly with regards to understanding the vulnerability of peatlands to disturbance. The flexibility of our suggested scheme may allow the future incorporation of ecohydrological phenomena yet to be identified as important in peatlands.

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Transport and thermodynamics constrain belowground carbon turnover in a northern peatland

Cited by 97 publications

References 64 publications

High soil solution carbon and nitrogen concentrations in a drained Atlantic bog are reduced to natural levels by 10 years of rewetting

High soil solution carbon and nitrogen concentrations in a drained Atlantic bog are reduced to natural levels by 10 years of rewetting

Anaerobic oxidation of methane: an underappreciated aspect of methane cycling in peatland ecosystems?

Conceptual frameworks in peatland ecohydrology: looking beyond the two‐layered (acrotelm–catotelm) model

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