Drivers of seasonal- and event-scale DOC dynamics at the outlet of mountainous peatlands revealed by high-frequency monitoring

Rosset, Thomas; Binet, Stéphane; Antoine, Jean-Marc; Lerigoleur, Émilie; Rigal, François; Gandois, Laure

doi:10.5194/bg-17-3705-2020

Cited by 18 publications

(13 citation statements)

References 96 publications

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“…Pulses of DOC during flood events can be understood as a succession of hydrological connection and disconnection between the peatland and the stream, causing changes in DOC concentrations in the stream (Billett et al, 2006;Laudon et al, 2011; Jutebring Sterte et al, 2022). The runoff generation into the peat is controlled by the water table depth (WTD; Holden and Burt, 2003;Frei et al, 2010), where a large WTD increase during flood events leads to hydrological reconnection between DOC sources (Inamdar et al, 2004;Tunaley et al, 2016;Rosset et al, 2020) and greater DOC exports (Blaurock et al, 2021).…”

Section: Introductionmentioning

confidence: 99%

“…DOC exports during flood events may vary depending on many parameters: the magnitude of the rainfall events, the season and the porewater temperature, the recurrence of high-flow events, the presence of a free-rainfall period, and the antecedent wetness of the catchment (Leach et al, 2016;Tiwari et al, 2018;Rosset et al, 2020;Blaurock et al, 2021). Previous studies have highlighted that long periods between rainfall events favour DOC production.…”

Section: Introductionmentioning

confidence: 99%

“…The amount of exported DOC is also controlled by production processes, stimulated by the temperature (Clark et al, 2007(Clark et al, , 2009Grand-Clement et al, 2014;Zhu et al, 2022) because DOC concentrations in the peat pore water increase with the temperature (Freeman et al, 2001;Buzek et al, 2019). Among the studies that have used an event-based approach in peatland streams, most of them have been performed in temperate (Worrall et al, 2008;Austnes et al, 2010;Grand-Clement et al, 2014;Tunaley et al, 2016) and alpine (Birkel et al, 2017;Rosset et al, 2020) catchments, and none have been realized in boreal environments. Boreal catchments are constrained by seasonal freezing and pronounced snowmelt (Ågren et al, 2010;Leach et al, 2016;Tiwari et al, 2018) that potentially affect and delay DOC exports (Laudon et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

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Hydrological connectivity controls dissolved organic carbon exports in a peatland-dominated boreal catchment stream

Prijac

Gandois

Taillardat

et al. 2023

Preprint

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Abstract. Peatland-derived dissolved organic carbon (DOC) exports from boreal peatlands are variable during the ice-free season, depending on the peatland water table and the alternation of low and high flow in peat-draining streams. However, calculation of the specific DOC exports from a peatland can be challenging considering the multiple potential DOC sources within the catchment. A calculation approach based on the hydrological connectivity between the peat and the stream could help to solve this issue, an approach used in the present study. This study took place from June 2018 to October 2019 in a boreal catchment in north-eastern Canada, with 76.7 % of the catchment covered by ombrotrophic peatland. The objectives were (1) to establish relationships between DOC exports from a headwater stream and the peatland hydrology; (2) to quantify, at the catchment scale, the amount of DOC laterally exported to the draining stream; and (3) to define the patterns of DOC mobilization during high river flow events. At the peatland headwater stream outlet, the DOC concentrations were monitored at a high frequency (hourly) using a fluorescent dissolved organic matter (fDOM) sensor, a proxy for DOC concentrations. Hydrological variables, such as stream outlet discharge and the peatland water table depth (WTD), were continuously monitored for 2 years. Our results highlight the direct and delayed control of subsurface flow from peat to the stream and associated DOC exports. Rain events raised the peatland WTD, which increased the hydrological connectivity between the peatland and the stream. This led to increased stream discharge (Q) and a delayed DOC concentration increase, typical of lateral subsurface flow. The magnitude of the WTD increase played a crucial role in influencing the quantity of exported DOC. Based on the assumption that the peatland is the major contributor to DOC exports and other DOC sources were negligible during high-flow periods, we propose a new approach to calculate the specific DOC exports attributable to the peatland by distinguishing the surface used to the calculation between high-flow and low-flow periods. In 2018–2019, 92.6 % of DOC was exported during flood events, despite accounting for 59.1 % of the period. In 2019–2020, 93.8 % of DOC was exported during flood events, which represented 44.1 % of the period. Our analysis of individual flood events revealed three types of events and DOC mobilization patterns. The first type is characterized by high rainfall leading to an important WTD increase favouring the connection between the peatland and the stream, leading to high DOC exports. The second is characterized by a large WTD increase succeeding a previous event that had depleted DOC available to be transferred to the stream, leading to lower DOC exports. The third type corresponds to low rainfall events with an insufficient WTD increase to reconnect the peatland and the stream, leading to low DOC exports. Hence, DOC exports are sensitive to hydroclimatic conditions. Moreover, flood events, changes in rainfall regimes, the ice-free season duration and porewater temperatures may affect the exported DOC and, consequently, partially offset the carbon sequestration capacity of peatlands.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Hydrological connectivity controls dissolved organic carbon exports in a peatland-dominated boreal catchment stream

Prijac

Gandois

Taillardat

et al. 2023

Preprint

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“…These data can be deposited in another data repository with the reference to the article. The SNO Tourbières dataset will mention if it contains this particular sub-dataset: 'HasPart' (e.g., Rosset, 2019b;.…”

Section: Involvement Of the Si Sno Tourbières In National And International Research Infrastructuresmentioning

confidence: 99%

The information system of the French Peatland Observation Service: Service National d'Observation Tourbières – A valuable tool to assess the impact of global changes on the hydrology and biogeochemistry of temperate peatlands through long term monitoring

Gogo

Paroissien

Laggoun‐Défarge

et al. 2021

Hydrological Processes

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Mitigating and adapting to global changes requires a better understanding of the response of the Biosphere to these environmental variations. Human disturbances and their effects act in the long term (decades to centuries) and consequently, a similar time frame is needed to fully understand the hydrological and biogeochemical functioning of a natural system. To this end, the ‘Centre National de la Recherche Scientifique’ (CNRS) promotes and certifies long‐term monitoring tools called national observation services or ‘Service National d'Observation’ (SNO) in a large range of hydrological and biogeochemical systems (e.g., cryosphere, catchments, aquifers). The SNO investigating peatlands, the SNO ‘Tourbières’, was certified in 2011 (https://www.sno-tourbieres.cnrs.fr/). Peatlands are mostly found in the high latitudes of the northern hemisphere and French peatlands are located in the southern part of this area. Thus, they are located in environmental conditions that will occur in northern peatlands in coming decades or centuries and can be considered as sentinels. The SNO Tourbières is composed of four peatlands: La Guette (lowland central France), Landemarais (lowland oceanic western France), Frasne (upland continental eastern France) and Bernadouze (upland southern France). Thirty target variables are monitored to study the hydrological and biogeochemical functioning of the sites. They are grouped into four datasets: hydrology, fluvial export of organic matter, greenhouse gas fluxes and meteorology/soil physics. The data from all sites follow a common processing chain from the sensors to the public repository. The raw data are stored on an FTP server. After operator or automatic processing, data are stored in a database, from which a web application extracts the data to make them available (https://data-snot.cnrs.fr/data-access/). Each year at least, an archive of each dataset is stored in Zenodo, with a digital object identifier (DOI) attribution (https://zenodo.org/communities/sno_tourbieres_data/).

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“…The rising organic carbon concentration tends to coincide with iron increases, and this phenomenon may be linked to the declining sulfur deposition (Björnerås et al, 2017). Additionally, seasonal variations of DOC concentration and transportation are highly driven by water temperature (Rosset et al, 2020). For example, Egea et al (2019) found that water temperatures positively affected DOC transportation.…”

Section: Introductionmentioning

confidence: 99%

Deforestation alters dissolved organic carbon and sulfate dynamics in a mountainous headwater catchment—A wavelet analysis

Wang

Robinson

et al. 2022

Front. For. Glob. Change

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Deforestation has a wide range of effects on hydrological and geochemical processes. Dissolved organic carbon (DOC) dynamics, a sensitive environmental change indicator, is expected to be affected by deforestation, with changes in atmospheric sulfur (S) deposition compounding this. However, how precisely anthropogenic disturbance (deforestation) under a declining atmospheric S input scenario affects the underlying spatiotemporal dynamics and relationships of river DOC and sulfate with hydro-climatological variables e.g., stream water temperature, runoff, pH, total dissolved iron (Fetot), and calcium (Ca2+) remains unclear. We, therefore, examined this issue within the TERENO Wüstebach catchment (Eifel, Germany), where partial deforestation had taken place in 2013. Wavelet transform coherence (WTC) analysis was applied based on a 10-year time series (2010–2020) from three sampling stations, whose (sub) catchment areas have different proportions of deforested area (W10: 31%, W14: 25%, W17: 3%). We found that water temperature and DOC, sulfate, and Fetot concentrations showed distinct seasonal patterns, with DOC averaging concentrations ranging from 2.23 (W17) to 4.56 (W10) mg L–1 and sulfate concentration ranging from 8.04 (W10) to 10.58 (W17) mg L–1. After clear-cut, DOC significantly increased by 59, 58% in the mainstream (W10, W14), but only 26% in the reference stream. WTC results indicated that DOC was negatively correlated with runoff and sulfate, but positively correlated with temperature, Ca2+, and Fetot. The negative correlation between DOC with runoff and sulfate was apparent over the whole examined 10-year period in W17 but did end in W10 and W14 after the deforestation. Sulfate (SO4) was highly correlated with stream water temperature, runoff, and Fetot in W10 and W14 and with a longer lag time than W17. Additionally, pH was stronger correlated (higher R2) with sulfate and DOC in W17 than in W10 and W14. In conclusion, WTC analysis indicates that within this low mountainous forest catchment deforestation levels over 25% (W10 and W14) affected the coupling of S and C cycling substantially more strongly than “natural” environmental changes as observed in W17.

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Drivers of seasonal- and event-scale DOC dynamics at the outlet of mountainous peatlands revealed by high-frequency monitoring

Cited by 18 publications

References 96 publications

Hydrological connectivity controls dissolved organic carbon exports in a peatland-dominated boreal catchment stream

Hydrological connectivity controls dissolved organic carbon exports in a peatland-dominated boreal catchment stream

The information system of the French Peatland Observation Service: Service National d'Observation Tourbières – A valuable tool to assess the impact of global changes on the hydrology and biogeochemistry of temperate peatlands through long term monitoring

Deforestation alters dissolved organic carbon and sulfate dynamics in a mountainous headwater catchment—A wavelet analysis

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