Assessing DOC export from a Sphagnum‐dominated peatland using δ¹³C and δ¹⁸O–H₂O stable isotopes

Abstract

Dissolved organic carbon (DOC) originating in peatlands can be mineralized to carbon dioxide (CO 2 ) and methane (CH 4 ), two potent greenhouse gases. Knowledge of the dynamics of DOC export via run-off is needed for a more robust quantification of C cycling in peatland ecosystems, a prerequisite for realistic predictions of future climate change. We studied dispersion pathways of DOC in a mountain-top peat bog in the Czech Republic (Central Europe), using a dual isotope approach. Although δ 13 C DOC values made it possible to link exported DOC with its within-bog source, δ 18 O H2O values of precipitation and run-off helped to understand run-off generation.Our 2-year DOC-H 2 O isotope monitoring was complemented by a laboratory peat incubation study generating an experimental time series of δ 13 C DOC values. DOC concentrations in run-off during high-flow periods were 20-30 mg L −1 . The top 2 cm of the peat profile, composed of decaying green moss, contained isotopically lighter C than deeper peat, and this isotopically light C was present in run-off in high-flow periods. In contrast, baseflow contained only 2-10 mg DOC L −1 , and its more variable C isotope composition intermittently fingerprinted deeper peat. DOC in run-off occasionally contained isotopically extremely light C whose source in solid peat substrate was not identified. Pre-event water made up on average 60% of the water run-off flux, whereas direct precipitation contributed 40%. Run-off response to precipitation was relatively fast. A highly leached horizon was identified in shallow catotelm. This peat layer was likely affected by a lateral influx of precipitation. Within 36 days of laboratory incubation, isotopically heavy DOC that had been initially released from the peat was replaced by isotopically lighter DOC, whose δ 13 C values converged to the solid substrate and natural run-off. We suggest that δ 13 C systematics can be useful in identification of vertically stratified within-bog DOC sources for peatland run-off. K E Y W O R D Speat, dissolved organic carbon, carbon isotopes, water isotopes

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

“…Others have shown that great WTD before a rain event favour rapid DOC mobilization and lead to greater exports, independently of the recurrence between events in a peatland (Birkel et al, 2017;Blaurock et al, 2021). 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.…”

“…Previous studies have highlighted that long periods between rainfall events favour DOC production. Greater DOC exports are measured once the hydrological connection is restored, given the large amounts of DOC recently produced in the peatland and which could be mobilized through lateral discharge (Worrall et al, 2008;Clark et al, 2009;Grand-Clement et al, 2014;Buzek et al, 2019). Others have shown that great WTD before a rain event favour rapid DOC mobilization and lead to greater exports, independently of the recurrence between events in a peatland (Birkel et al, 2017;Blaurock et al, 2021).…”

Understanding the soil and plant water hydrological cycle in a typical wetland under harsh natural conditions in the Shigatse area of the Tibetan Plateau

“…Overall, the wetland showed more obviously depleted δ 13 C values than the river; however, the groundwater downstream of the wetland had the most depleted δ 13 C values (Figure 5). Jiangsa wetland is an important carbon reservoir that can produce a large amount of soil biogenic CH 4 and CO 2 (Bridgham et al, 2006; Buzek et al, 2019; Roulet, 2000). CH 4 is characterized by strong 13 C depletion (δ 13 C = −44‰ to −60‰) in the alpine wetland of the southern QTP (Kato et al, 2017).…”

Dissolved organic carbon vertical movement and carbon accumulation in West Siberian peatlands

“…Our results considered the hypothesis about DOC downward movement. Numerous studies have analyzed DOC export from peatlands (Freeman et al, 2001;Frey and Smith, 2005;Buzek et. al., 2019;Blueten et al, 2020) but only few are related to the downward DOC movement and none covers this process in peatlands of Western Siberia, except (Schulze at al., 2015).…”