Hydrological processes and permafrost regulate magnitude, source and chemical characteristics of dissolved organic carbon export in a peatland catchment of northeastern China

Abstract. Permafrost thawing in peatland has the potential to alter the catchment export of dissolved organic carbon (DOC), thus influencing carbon cycling in linked aquatic and ocean ecosystems. However, peatland along the southern margins of Eurasian permafrost are seldom examined in spite of the presence of considerable risks associated with degradation due to climate warming. This study examines dynamics of DOC export from a permafrost peatland catchment located in northeastern China during the growing seasons of 2012 to 2014. Our findings show that runoff processes affect observed DOC concentrations, magnitudes, sources, and chemical characteristics of stream discharge. The entire catchment exhibits strong potential for annual DOC exporting (4.87 g C m−2), and DOC from the peatland landscape alone is estimated to amount to 12.89 g C m−2. Annual DOC export processes are closely related to total discharge levels, and floods contribute to approximately 85 % of DOC export levels. Flood volumes derived mainly from peat pore water stored in the upper organic layer of the soil profile prior to rainfall events, creating a strong linkage between discharge and DOC concentrations. DOC source and chemical characteristics, as indicated by three fluorescence indexes, have changed regularly according to source shifts occurring as a result of flood and baseflow processes. A deepening of the active layer due to climate warming should elevate proportions of microbial-originated DOC in the baseflow. Given expected future increases in precipitation, our results show that the magnitude of DOC exports from the study region will increase.

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Hydrological processes and permafrost regulate magnitude, source and chemical characteristics of dissolved organic carbon export in a peatland catchment of northeastern China

Hydrology and Earth System Sciences ◽

10.5194/hess-22-1081-2018 ◽

2018 ◽

Vol 22 (2) ◽

pp. 1081-1093 ◽

Cited By ~ 2

Author(s):

Yuedong Guo ◽

Changchun Song ◽

Wenwen Tan ◽

Xianwei Wang ◽

Yongzheng Lu

Keyword(s):

Organic Carbon ◽

Dissolved Organic Carbon ◽

Active Layer ◽

Climate Warming ◽

Carbon Balance ◽

Northeastern China ◽

Chemical Characteristics ◽

Permafrost Degradation ◽

Carbon Export ◽

Seasonal Thawing

Abstract. Permafrost thawing in peatlands has the potential to alter the catchment export of dissolved organic carbon (DOC), thus influencing the carbon balance and cycling in linked aquatic and ocean ecosystems. Peatlands along the southern margins of the Eurasian permafrost are relatively underexplored despite the considerable risks associated with permafrost degradation due to climate warming. This study examined dynamics of DOC export from a permafrost peatland catchment located in northeastern China during the 2012 to 2014 growing seasons. The estimated annual DOC loads varied greatly between 3211 and 19 022 kg yr−1, with a mean DOC yield of 4.7 g m−2 yr−1. Although the estimated DOC yield was in the lower range compared with other permafrost regions, it was still significant for the net carbon balance in the studied catchment. There were strong linkages between daily discharge and DOC concentrations in both wet and dry years, suggesting a transport-limited process of DOC delivery from the catchment. Discharge explained the majority of both seasonal and interannual variations of DOC concentrations, which made annual discharge a good indicator of total DOC load from the catchment. As indicated by three fluorescence indices, DOC source and chemical characteristics tracked the shift of flow paths during runoff processes closely. Interactions between the flow path and DOC chemical characteristics were greatly influenced by the seasonal thawing of the soil active layer. The deepening of the active layer due to climate warming likely increases the proportion of microbial-originated DOC in baseflow discharge.

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Review of “Hydrological processes and permafrost regulate magnitude, source and chemical characteristics of dissolved organic carbon export in a peatland catchment in northeastern China by Guo et al.

10.5194/hess-2017-412-rc3 ◽

2017 ◽

Author(s):

Anonymous

Keyword(s):

Organic Carbon ◽

Dissolved Organic Carbon ◽

Northeastern China ◽

Hydrological Processes ◽

Chemical Characteristics ◽

Carbon Export

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Referee review: Hydrological processes and permafrost regulate magnitude, source and chemical characteristics of dissolved organic carbon export in a peatland catchment of northeastern China

10.5194/hess-2017-412-rc1 ◽

2017 ◽

Author(s):

Anonymous

Keyword(s):

Organic Carbon ◽

Dissolved Organic Carbon ◽

Northeastern China ◽

Hydrological Processes ◽

Chemical Characteristics ◽

Carbon Export

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An integrated Dissolved Organic Carbon Dynamics Model (DOCDM 1.0): model development and a case study in the Alaskan Yukon River Basin

Geoscientific Model Development Discussions ◽

10.5194/gmdd-8-10411-2015 ◽

2015 ◽

Vol 8 (12) ◽

pp. 10411-10454 ◽

Cited By ~ 2

Author(s):

X. Lu ◽

Q. Zhuang

Keyword(s):

Organic Carbon ◽

Dissolved Organic Carbon ◽

Overland Flow ◽

Terrestrial Ecosystems ◽

Carbon Dynamics ◽

Water Infiltration ◽

Dynamics Model ◽

Study Region ◽

Doc Export ◽

Doc Production

Abstract. Quantitative understanding of the variation in dissolved organic carbon (DOC) is important to studying the terrestrial ecosystem carbon cycle. This study presents a process-based, dissolved organic carbon dynamics model (DOCDM 1.0) that couples the soil heat conduction, water flow, DOC production, mineralization and transport in both surface and subsurface of soil profile to quantify DOC dynamics in boreal terrestrial ecosystems. The model is first evaluated and then applied for a watershed in Alaska to investigate its DOC production and transport. We find that 42 and 27 % of precipitation infiltrates to soils in 2004, a warmer year, and in 1976, a colder year, respectively. Under warming conditions, DOC transported via overland flow does not show the expected decrease trend while the overland DOC yield shows a 4 % increase. The horizontal subsurface flow only accounts for 1–2 % of total water flux, but transports 30–50 % of DOC into rivers. Water flush due to water infiltration controls DOC transport. Snowmelt plays a noticeable role in DOC flush-out and DOC transport significantly depends on flowpaths in the study region. High soil temperature stimulates DOC production. The overland DOC export does not necessarily follow the DOC downward trend in surface water transport. Overall, this study shows that DOC export behavior is complex under changing temperature and hydrological conditions in cold-region watersheds. To adequately quantify DOC dynamics in northern high latitudes, more DOC and hydrological data are needed to better parameterize and test the developed model before extrapolating it to the region.

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Landscape controls on riverine export of dissolved organic carbon from Great Britain

Biogeochemistry ◽

10.1007/s10533-021-00762-2 ◽

2021 ◽

Author(s):

Jennifer L. Williamson ◽

Andrew Tye ◽

Dan J. Lapworth ◽

Don Monteith ◽

Richard Sanders ◽

...

Keyword(s):

Land Use ◽

Great Britain ◽

Population Density ◽

Organic Carbon ◽

Dissolved Organic Carbon ◽

Forest Cover ◽

River Systems ◽

C Cycle ◽

Global Land ◽

Doc Export

AbstractThe dissolved organic carbon (DOC) export from land to ocean via rivers is a significant term in the global C cycle, and has been modified in many areas by human activity. DOC exports from large global rivers are fairly well quantified, but those from smaller river systems, including those draining oceanic regions, are generally under-represented in global syntheses. Given that these regions typically have high runoff and high peat cover, they may exert a disproportionate influence on the global land–ocean DOC export. Here we describe a comprehensive new assessment of the annual riverine DOC export to estuaries across the island of Great Britain (GB), which spans the latitude range 50–60° N with strong spatial gradients of topography, soils, rainfall, land use and population density. DOC yields (export per unit area) were positively related to and best predicted by rainfall, peat extent and forest cover, but relatively insensitive to population density or agricultural development. Based on an empirical relationship with land use and rainfall we estimate that the DOC export from the GB land area to the freshwater-seawater interface was 1.15 Tg C year−1 in 2017. The average yield for GB rivers is 5.04 g C m−2 year−1, higher than most of the world’s major rivers, including those of the humid tropics and Arctic, supporting the conclusion that under-representation of smaller river systems draining peat-rich areas could lead to under-estimation of the global land–ocean DOC export. The main anthropogenic factor influencing the spatial distribution of GB DOC exports appears to be upland conifer plantation forestry, which is estimated to have raised the overall DOC export by 0.168 Tg C year−1. This is equivalent to 15% of the estimated current rate of net CO2 uptake by British forests. With the UK and many other countries seeking to expand plantation forest cover for climate change mitigation, this ‘leak in the ecosystem’ should be incorporated in future assessments of the CO2 sequestration potential of forest planting strategies.

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