Spatial differentiation of sediment organic matter isotopic composition and inferred sources in a temperate forest lake catchment

Douglas, Peter; Stratigopoulos, Emerald; Park, Sanga; Keenan, Benjamin

doi:10.1016/j.chemgeo.2022.120887

Cited by 19 publications

(9 citation statements)

References 92 publications

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“…We suggest this may reflect deposition of particulate plant biomass in this region where the elevation gradient rapidly decreases, leading to a decrease in stream power and deposition of larger particles in fluvial sediments. This is consistent with other studies indicating that fresh plant material is flushed from high-energy upstream environments and deposited in low-energy streambeds or lake sediments (Dalzell et al, 2007;Douglas et al, 2022;Smith et al, 2013). The sample closest to the confluence contains a significantly higher bulk δ 13 C value than other LPW sediments (Figure 2b), consistent with an accumulation of biomass from upstream ecosystems with higher δ 13 C values, including possible input from maize agricultural fields and other C 4 plants that are common in the upstream regions of both the Polochic and Cahabón rivers (Figure S2 in Supporting Information S1).…”

Section: Soil Erosion-controlled Export Of Aged Organic Matter In The...supporting

confidence: 92%

“…Overall, the variability in 14 C between these samples points to pronounced within‐lake spatial variability in lake sediment OM age, and likely in OM source. Spatial heterogeneity in sediment OM isotopic composition has been observed in some other systems (Bovee & Pearson, 2014; Douglas et al., 2022; Murase & Sakamoto, 2000; Taylor et al., 2015), but is not typically incorporated in studies of inland water sediment C burial.…”

Section: Discussionmentioning

confidence: 99%

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Distinct Modes of Aged Soil Carbon Export in a Large Tropical Lake Basin Identified Using Bulk and Compound‐Specific Radiocarbon Analyses of Fluvial and Lacustrine Sediment

Parker¹,

Ahad

Obrist‐Farner

et al. 2023

JGR Biogeosciences

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The 14C content of sedimentary organic matter and specific organic molecules provide valuable information on the source and age of organic matter stored in sediments, but these data are limited for tropical fluvial and lake sediments. We analyzed 14C in bulk organic matter, palmitic acid (C16), and long‐chain n‐alkanoic acids (C24, C26, C28), within fluvial and lake sediments in the catchment of Lake Izabal, a large tectonic lake basin in Guatemala. We combined these measurements with bulk and compound‐specific δ13C measurements, as well as sediment OC:N ratios, to understand the source and age of sedimentary organic matter in different regions of the lake catchment. Most fatty acid and bulk OM samples were characterized by pre‐modern carbon, indicating important input of aged carbon with residence times of hundreds to thousands of years into sediments. We identified two mechanisms leading to aged carbon export to sediments. In the high‐relief and deforested Polochic catchment, older OM and fatty acids are associated with low %TOC and low OC:N, indicating aged organic matter associated with eroded mineral soil. In the smaller, low‐relief, and largely forested Oscuro catchment, old OM and fatty acids are associated with high %TOC and high OC:N ratios, indicating export of undegraded aged plant biomass from swamp peat. The age of bulk OM and fatty acids in Lake Izabal sediments is similar to the ages observed in fluvial sediments, implying that fluvial input of aged soil carbon makes an important contribution to lake sediment carbon reservoirs in this large tropical lake.

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Section: Soil Erosion-controlled Export Of Aged Organic Matter In The...supporting

confidence: 92%

Section: Discussionmentioning

confidence: 99%

Distinct Modes of Aged Soil Carbon Export in a Large Tropical Lake Basin Identified Using Bulk and Compound‐Specific Radiocarbon Analyses of Fluvial and Lacustrine Sediment

Parker¹,

Ahad

Obrist‐Farner

et al. 2023

JGR Biogeosciences

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“…1). Fine-grained mineral soiland bedrock-derived particles are advected to the center of the lake, whereas coarser, waterlogged biospheric debris mo-bilized by surface runoff is likely deposited near the river inlets (Douglas et al, 2022).…”

Section: Downstream Evolution Of Particulate Organic Carbonmentioning

confidence: 99%

Environmental and hydrologic controls on sediment and organic carbon export from a subalpine catchment: insights from a time series

et al. 2022

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Abstract. Studies engaging in tracking headwater carbon signatures downstream remain sparse, despite their importance for constraining transfer and transformation pathways of organic carbon (OC) and developing regional-scale perspectives on mechanisms influencing the balance between remineralization and carbon export. Based on a 40-month time series, we investigate the dependence of hydrology and seasonality on the discharge of sediment and OC in a small (350 km2) Swiss subalpine watershed (Sihl River basin). We analyze concentrations and isotopic compositions (δ13C, F14C) of particulate OC and use dual-isotope mixing and machine learning frameworks to characterize and estimate source contributions, transport pathways, and export fluxes. The majority of transferred OC is sourced from plant biomass and soil material. The relative amount of bedrock-derived (petrogenic) OC, abundant in headwater streams, progressively decreases downstream in response to a lack of source material and efficient overprinting with biospheric OC, illustrating rapid organic matter alteration over short distances. Large variations in OC isotopic compositions observed during baseflow conditions converge and form a homogenous mixture enriched in OC and characterized by higher POC-F14C values following precipitation-driven events. Particulate OC isotopic data and model results suggest that storms facilitate surface runoff and the inundation of riparian zones, resulting in the entrainment of loose plant-derived debris and surficial soil material. Although particle transport in the Sihl River basin is mainly driven by hydrology, subtle changes in bedrock erosivity, slope angle, and floodplain extent likely have profound effects on the POC composition, age, and export yields.

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“…1). Fine-grained mineral soil-and bedrock-derived particles are advected to the center of the lake, whereas coarser, waterlogged biospheric debris mobilized by surface runoff is likely deposited near the river inlets (Douglas et al, 2022).…”

Section: Downstream Evolution Of Particulate Organic Carbonmentioning

confidence: 99%

Environmental and hydrologic controls on sediment and organic carbon export from a subalpine catchment: insights from a time-series

Schwab

Gies

Freymond

et al. 2022

Preprint

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Abstract. Studies engaging in tracking headwater carbon signatures downstream remain sparse, despite their importance for constraining transfer and transformation pathways of organic carbon (OC) and developing regional-scale perspectives on mechanisms influencing the balance between remineralization and carbon export. Based on a 40-month time series, we investigate the dependence of hydrology and seasonality on the discharge of sediment and OC in a small Swiss subalpine watershed (Sihl River basin). We analyze concentrations and isotopic compositions (δ13C, F14C) of particulate OC and use dual-isotope mixing and machine learning frameworks to characterize and estimate source contributions, transport pathways, and export fluxes. The majority of transferred OC is sourced from plant biomass and soil material. Relative proportions of soil-derived particulate OC peak during the summer months, coinciding with maximum soil erosion rates. Bedrock-derived (petrogenic) OC abundant in headwater streams progressively decreases downstream in response to a lack of source material and efficient overprinting with biospheric organic matter, illustrating rapid OC transformation over short distances. Large variations in isotopic compositions observed during baseflow conditions converge and form a homogenous mixture enriched in OC and characterized by higher POC- F14C values following precipitation-driven events. We propose that storms facilitate surface runoff and shallow landsliding, resulting in the entrainment of fresh litter and surficial soil layers. Model results further indicate diverging mobilization pathways. Discharge and water stage describe the export of suspended sediment, while the prediction of POC fluxes is mostly supported by water stage and 1-day antecedent precipitation. Although particle transport in the Sihl River basin is mainly driven by hydrology, subtle changes in bedrock erosivity, slope angle, and floodplain extent likely have profound effects on the POC composition, age, and export yields.

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Spatial differentiation of sediment organic matter isotopic composition and inferred sources in a temperate forest lake catchment

Cited by 19 publications

References 92 publications

Distinct Modes of Aged Soil Carbon Export in a Large Tropical Lake Basin Identified Using Bulk and Compound‐Specific Radiocarbon Analyses of Fluvial and Lacustrine Sediment

Distinct Modes of Aged Soil Carbon Export in a Large Tropical Lake Basin Identified Using Bulk and Compound‐Specific Radiocarbon Analyses of Fluvial and Lacustrine Sediment

Environmental and hydrologic controls on sediment and organic carbon export from a subalpine catchment: insights from a time series

Environmental and hydrologic controls on sediment and organic carbon export from a subalpine catchment: insights from a time-series

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