Sources, Sinks, and Fluxes of Dissolved Organic Carbon in Subarctic Fen Catchments

Koprivnjak, Jean-François; Moore, Tim R.

doi:10.2307/1551658

Cited by 65 publications

(40 citation statements)

References 49 publications

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“…Peatlands have been found to export between 0.2 and 11.5 mmol m −2 d −1 to discharging streams (Moore 1987(Moore , 1988Urban et al 1989;Koprivnjak and Moore 1992;Dillon and Molot 1997). DOC release from Thoreau's Bog, an ombrotrophic peatland in the northeastern United States, was 5-10 mmol m −2 d −1 (McKnight et al 1985), which is somewhat lower than the figures obtained in this study (Table 1, ЉDOC flux dissolvedЉ).…”

Section: Discussioncontrasting

confidence: 79%

Carbon turnover in peatland mesocosms exposed to different water table levels

2004

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Abstract. Changes of water table position influence carbon cycling in peatlands, but effects on the sources and sinks of carbon are difficult to isolate and quantify in field investigations due to seasonal dynamics and covariance of variables. We thus investigated carbon fluxes and dissolved carbon production in peatland mesocosms from two acidic and oligotrophic peatlands under steady state conditions at two different water table positions. Exchange rates and CO 2 , CH 4 and DOC production rates were simultaneously determined in the peat from diffusive-advective mass-balances of dissolved CO 2 , CH 4 and DOC in the pore water. Incubation experiments were used to quantify potential CO 2, CH 4 , and DOC production rates. The carbon turnover in the saturated peat was dominated by the production of DOC (10-15 mmol m −2 d −1 ) with lower rates of DIC (6.1-8.5 mmol m −2 d −1 ) and CH 4 (2.2-4.2 mmol m −2 d −1 ) production. All production rates strongly decreased with depth indicating the importance of fresh plant tissue for dissolved C release. A lower water table decreased area based rates of photosynthesis (24-42%), CH 4 production (factor 2.5-3.5) and emission, increased rates of soil respiration and microbial biomass C, and did not change DOC release. Due to the changes in process rates the C net balance of the mesocosms shifted by 36 mmol m −2 d −1 . According to our estimates the change in C mineralization contributed most to this change. Anaerobic rates of CO 2 production rates deeper in the peat increased significantly by a factor of 2-3.5 (DOC), 2.9-3.9 (CO 2 ), and 3-14 (CH 4 ) when the water table was lowered by 30 cm. This phenomenon might have been caused by easing an inhibiting effect by the accumulation of CO 2 and CH 4 when the water table was at the moss surface.

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Section: Discussioncontrasting

confidence: 79%

Carbon turnover in peatland mesocosms exposed to different water table levels

2004

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“…However, the diplotelmic model is only able to represent this one type of hot spot and only in one dimension. Other examples of hot spots that have been identified in peatlands include lagg fens, recognized as zones of high mineral and DOC concentrations and rapid exchanges of chemical energy and solute mass (Koprivnjak and Moore, 1992;Mitchell et al, 2008), peat pipes in blanket bogs, which act as conduits for water, oxygen and DOC into and out of the peat profile, and are localized areas of rapid decomposition (Holden, 2005b), the live plant layer, where photosynthesis leads to high rates of evaporative water loss, latent heat exchange and carbon sequestration (Kim and Verma, 1996) and areas of groundwater upwelling in fens, which exhibit high porewater dissolved mineral content (Almendinger and Leete, 1998). Most importantly to our argument, hot spots may be delineated not only with respect to depth (as in Ingram's (1978) original scheme), but also horizontally to represent two-dimensional or three-dimensional heterogeneity in peatland ecohydrology (Mitchell et al, 2008).…”

Section: Hot Spots and Cold Spotsmentioning

confidence: 99%

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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“…Fluxes of DOC generally decrease from the litter layer to deeper mineral hori-zons (Table 1). In virtually every soil with substantial clay content, DOC concentrations drop by 50%-90% from the surface organic layers to subsurface mineral soils (McDowell and Wood 1984;Cronan and Aiken 1985;Dalva and Moore 1991;Koprivnjak and Moore 1992;Dosskey and Bertsch 1997). Surface soil fluxes of DOC range from 10 to 85 g C m Ϫ2 y Ϫ1 ; below the surface horizons, they decline to 2-40 g C m Ϫ2 y Ϫ1 (Table 1).…”

Section: Model Generationmentioning

confidence: 99%

Dissolved Organic Carbon in Terrestrial Ecosystems: Synthesis and a Model

2001

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The movement of dissolved organic carbon (DOC) through soils is an important process for the transport of carbon within ecosystems and the formation of soil organic matter. In some cases, DOC fluxes may also contribute to the carbon balance of terrestrial ecosystems; in most ecosystems, they are an important source of energy, carbon, and nutrient transfers from terrestrial to aquatic ecosystems. Despite their importance for terrestrial and aquatic biogeochemistry, these fluxes are rarely represented in conceptual or numerical models of terrestrial biogeochemistry. In part, this is due to the lack of a comprehensive understanding of the suite of processes that control DOC dynamics in soils. In this article, we synthesize information on the geochemical and biological factors that control DOC fluxes through soils. We focus on conceptual issues and quantitative evaluations of key process rates to present a general numerical model of DOC dynamics. We then test the sensitivity of the model to variation in the controlling parameters to highlight both the significance of DOC fluxes to terrestrial carbon processes and the key uncertainties that require additional experiments and data. Simulation model results indicate the importance of representing both root carbon inputs and soluble carbon fluxes to predict the quantity and distribution of soil carbon in soil layers. For a test case in a temperate forest, DOC contributed 25% of the total soil profile carbon, whereas roots provided the remainder. The analysis also shows that physical factors-most notably, sorption dynamics and hydrology-play the dominant role in regulating DOC losses from terrestrial ecosystems but that interactions between hydrology and microbial-DOC relationships are important in regulating the fluxes of DOC in the litter and surface soil horizons. The model also indicates that DOC fluxes to deeper soil layers can support a large fraction (up to 30%) of microbial activity below 40 cm.

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Sources, Sinks, and Fluxes of Dissolved Organic Carbon in Subarctic Fen Catchments

Cited by 65 publications

References 49 publications

Carbon turnover in peatland mesocosms exposed to different water table levels

Carbon turnover in peatland mesocosms exposed to different water table levels

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

Dissolved Organic Carbon in Terrestrial Ecosystems: Synthesis and a Model

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