Chronic atmospheric reactive N deposition has breached the N sink capacity of a northern ombrotrophic peatbog increasing the gaseous and fluvial N losses

Fotis Sgouridis; Christopher A. Yates; Charlotte E.M. Lloyd; Ernesto Saiz; Daniel N. Schillereff; Sam Tomlinson; Jennifer Williamson; Sami Ullah

doi:10.1016/j.scitotenv.2021.147552

Chronic atmospheric reactive N deposition has breached the N sink capacity of a northern ombrotrophic peatbog increasing the gaseous and fluvial N losses

Fotis Sgouridis^*, Christopher A. Yates, Charlotte E.M. Lloyd, Ernesto Saiz, Daniel N. Schillereff, Sam Tomlinson, Jennifer Williamson, Sami Ullah

^*Corresponding author for this work

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Abstract

Peatlands play an important role in modulating the climate, mainly through sequestration of carbon dioxide into peat carbon, which depends on the availability of reactive nitrogen (Nr) to mosses. Atmospheric Nr deposition in the UK has been above the critical load for functional and structural changes to peatland mosses, thus threatening to accelerate their succession by vascular plants and increasing the possibility of Nr export to downstream ecosystems. The N balance of peatlands has received comparatively little attention, mainly due to the difficulty in measuring gaseous N losses as well as the Nr inputs due to biological nitrogen fixation (BNF). In this study we have estimated the mean annual N balance of an ombrotrophic bog (Migneint, North Wales) by measuring in situ N₂ + N₂O gaseous fluxes and also BNF in peat and mosses. Fluvial N export was monitored through a continuous record of DON flux, while atmospheric N deposition was modelled on a 5 × 5 km grid. The mean annual N mass balance was slightly positive (0.7 ± 4.1 kg N ha⁻¹ y⁻¹) and varied interannually indicating the fragile status of this bog ecosystem that has reached N saturation and is prone to becoming a net N source. Gaseous N losses were a major N output term accounting for 70% of the N inputs, mainly in the form of the inert N₂ gas, thus providing partial mitigation to the adverse effects of chronic Nr enrichment. BNF was suppressed by 69%, compared to rates in pristine bogs, but was still active, contributing ~2% of the N inputs. The long-term peat N storage rate (8.4 ± 0.8 kg N ha⁻¹ y⁻¹) cannot be met by the measured N mass balance, showing that the bog catchment is losing more N than it can store due its saturated status.

Original language	English
Article number	147552
Journal	Science of the Total Environment
Volume	787
DOIs	https://doi.org/10.1016/j.scitotenv.2021.147552
Publication status	Published - 15 Sept 2021

Keywords

N isotopes
Atmospheric N deposition
Biological nitrogen fixation
Denitrification
DON
Peatbog

UN SDGs

This output contributes to the following UN Sustainable Development Goals (SDGs)

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10.1016/j.scitotenv.2021.147552

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Sgouridis, F., Yates, C. A., Lloyd, C. E. M., Saiz, E., Schillereff, D. N., Tomlinson, S., Williamson, J., & Ullah, S. (2021). Chronic atmospheric reactive N deposition has breached the N sink capacity of a northern ombrotrophic peatbog increasing the gaseous and fluvial N losses. Science of the Total Environment, 787, Article 147552. https://doi.org/10.1016/j.scitotenv.2021.147552

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title = "Chronic atmospheric reactive N deposition has breached the N sink capacity of a northern ombrotrophic peatbog increasing the gaseous and fluvial N losses",

abstract = "Peatlands play an important role in modulating the climate, mainly through sequestration of carbon dioxide into peat carbon, which depends on the availability of reactive nitrogen (Nr) to mosses. Atmospheric Nr deposition in the UK has been above the critical load for functional and structural changes to peatland mosses, thus threatening to accelerate their succession by vascular plants and increasing the possibility of Nr export to downstream ecosystems. The N balance of peatlands has received comparatively little attention, mainly due to the difficulty in measuring gaseous N losses as well as the Nr inputs due to biological nitrogen fixation (BNF). In this study we have estimated the mean annual N balance of an ombrotrophic bog (Migneint, North Wales) by measuring in situ N2 + N2O gaseous fluxes and also BNF in peat and mosses. Fluvial N export was monitored through a continuous record of DON flux, while atmospheric N deposition was modelled on a 5 × 5 km grid. The mean annual N mass balance was slightly positive (0.7 ± 4.1 kg N ha−1 y−1) and varied interannually indicating the fragile status of this bog ecosystem that has reached N saturation and is prone to becoming a net N source. Gaseous N losses were a major N output term accounting for 70% of the N inputs, mainly in the form of the inert N2 gas, thus providing partial mitigation to the adverse effects of chronic Nr enrichment. BNF was suppressed by 69%, compared to rates in pristine bogs, but was still active, contributing ~2% of the N inputs. The long-term peat N storage rate (8.4 ± 0.8 kg N ha−1 y−1) cannot be met by the measured N mass balance, showing that the bog catchment is losing more N than it can store due its saturated status.",

keywords = "N isotopes, Atmospheric N deposition, Biological nitrogen fixation, Denitrification, DON, Peatbog",

author = "Fotis Sgouridis and Yates, {Christopher A.} and Lloyd, {Charlotte E.M.} and Ernesto Saiz and Schillereff, {Daniel N.} and Sam Tomlinson and Jennifer Williamson and Sami Ullah",

note = "Funding Information: The authors wish to acknowledge and thank staff at the UK Centre for Ecology & Hydrology (Bangor), who deployed and maintained instream optical sensors and Dwr Cymru Welsh Water (DCWW) for allowing access to the data. This research draws upon published datasets available through the Environmental Information Data Centre (hosted by UKCEH), funded under the Natural Environment Research Council (NERC) Macronutrient Cycles Programme. Stage discharge data along with the sampling and analysis of instream chemical variables were conducted under ?Turf 2 Surf? project (NERC; NE/J011991/1). Measurements of N2 and N2O along with atmospheric deposition data were funded under the LTLS project (NERC; NE/J011541/1, NE/J011533/1 and NE/J011703/1 respectively). A special thanks goes to Edward Tipping and Hannah Toberman who carried out all the sampling and analysis in peat cores collected in the Migneint. Funding Information: The authors wish to acknowledge and thank staff at the UK Centre for Ecology & Hydrology (Bangor), who deployed and maintained instream optical sensors and Dwr Cymru Welsh Water (DCWW) for allowing access to the data. This research draws upon published datasets available through the Environmental Information Data Centre (hosted by UKCEH), funded under the Natural Environment Research Council (NERC) Macronutrient Cycles Programme. Stage discharge data along with the sampling and analysis of instream chemical variables were conducted under {\textquoteleft}Turf 2 Surf{\textquoteright} project (NERC; NE/J011991/1). Measurements of N 2 and N 2 O along with atmospheric deposition data were funded under the LTLS project (NERC; NE/J011541/1, NE/J011533/1 and NE/J011703/1 respectively). A special thanks goes to Edward Tipping and Hannah Toberman who carried out all the sampling and analysis in peat cores collected in the Migneint. Publisher Copyright: {\textcopyright} 2021 The Authors Copyright: Copyright 2021 Elsevier B.V., All rights reserved.",

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doi = "10.1016/j.scitotenv.2021.147552",

language = "English",

volume = "787",

journal = "Science of the Total Environment",

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T1 - Chronic atmospheric reactive N deposition has breached the N sink capacity of a northern ombrotrophic peatbog increasing the gaseous and fluvial N losses

AU - Sgouridis, Fotis

AU - Yates, Christopher A.

AU - Lloyd, Charlotte E.M.

AU - Saiz, Ernesto

AU - Schillereff, Daniel N.

AU - Tomlinson, Sam

AU - Williamson, Jennifer

AU - Ullah, Sami

N1 - Funding Information: The authors wish to acknowledge and thank staff at the UK Centre for Ecology & Hydrology (Bangor), who deployed and maintained instream optical sensors and Dwr Cymru Welsh Water (DCWW) for allowing access to the data. This research draws upon published datasets available through the Environmental Information Data Centre (hosted by UKCEH), funded under the Natural Environment Research Council (NERC) Macronutrient Cycles Programme. Stage discharge data along with the sampling and analysis of instream chemical variables were conducted under ?Turf 2 Surf? project (NERC; NE/J011991/1). Measurements of N2 and N2O along with atmospheric deposition data were funded under the LTLS project (NERC; NE/J011541/1, NE/J011533/1 and NE/J011703/1 respectively). A special thanks goes to Edward Tipping and Hannah Toberman who carried out all the sampling and analysis in peat cores collected in the Migneint. Funding Information: The authors wish to acknowledge and thank staff at the UK Centre for Ecology & Hydrology (Bangor), who deployed and maintained instream optical sensors and Dwr Cymru Welsh Water (DCWW) for allowing access to the data. This research draws upon published datasets available through the Environmental Information Data Centre (hosted by UKCEH), funded under the Natural Environment Research Council (NERC) Macronutrient Cycles Programme. Stage discharge data along with the sampling and analysis of instream chemical variables were conducted under ‘Turf 2 Surf’ project (NERC; NE/J011991/1). Measurements of N 2 and N 2 O along with atmospheric deposition data were funded under the LTLS project (NERC; NE/J011541/1, NE/J011533/1 and NE/J011703/1 respectively). A special thanks goes to Edward Tipping and Hannah Toberman who carried out all the sampling and analysis in peat cores collected in the Migneint. Publisher Copyright: © 2021 The Authors Copyright: Copyright 2021 Elsevier B.V., All rights reserved.

PY - 2021/9/15

Y1 - 2021/9/15

N2 - Peatlands play an important role in modulating the climate, mainly through sequestration of carbon dioxide into peat carbon, which depends on the availability of reactive nitrogen (Nr) to mosses. Atmospheric Nr deposition in the UK has been above the critical load for functional and structural changes to peatland mosses, thus threatening to accelerate their succession by vascular plants and increasing the possibility of Nr export to downstream ecosystems. The N balance of peatlands has received comparatively little attention, mainly due to the difficulty in measuring gaseous N losses as well as the Nr inputs due to biological nitrogen fixation (BNF). In this study we have estimated the mean annual N balance of an ombrotrophic bog (Migneint, North Wales) by measuring in situ N2 + N2O gaseous fluxes and also BNF in peat and mosses. Fluvial N export was monitored through a continuous record of DON flux, while atmospheric N deposition was modelled on a 5 × 5 km grid. The mean annual N mass balance was slightly positive (0.7 ± 4.1 kg N ha−1 y−1) and varied interannually indicating the fragile status of this bog ecosystem that has reached N saturation and is prone to becoming a net N source. Gaseous N losses were a major N output term accounting for 70% of the N inputs, mainly in the form of the inert N2 gas, thus providing partial mitigation to the adverse effects of chronic Nr enrichment. BNF was suppressed by 69%, compared to rates in pristine bogs, but was still active, contributing ~2% of the N inputs. The long-term peat N storage rate (8.4 ± 0.8 kg N ha−1 y−1) cannot be met by the measured N mass balance, showing that the bog catchment is losing more N than it can store due its saturated status.

AB - Peatlands play an important role in modulating the climate, mainly through sequestration of carbon dioxide into peat carbon, which depends on the availability of reactive nitrogen (Nr) to mosses. Atmospheric Nr deposition in the UK has been above the critical load for functional and structural changes to peatland mosses, thus threatening to accelerate their succession by vascular plants and increasing the possibility of Nr export to downstream ecosystems. The N balance of peatlands has received comparatively little attention, mainly due to the difficulty in measuring gaseous N losses as well as the Nr inputs due to biological nitrogen fixation (BNF). In this study we have estimated the mean annual N balance of an ombrotrophic bog (Migneint, North Wales) by measuring in situ N2 + N2O gaseous fluxes and also BNF in peat and mosses. Fluvial N export was monitored through a continuous record of DON flux, while atmospheric N deposition was modelled on a 5 × 5 km grid. The mean annual N mass balance was slightly positive (0.7 ± 4.1 kg N ha−1 y−1) and varied interannually indicating the fragile status of this bog ecosystem that has reached N saturation and is prone to becoming a net N source. Gaseous N losses were a major N output term accounting for 70% of the N inputs, mainly in the form of the inert N2 gas, thus providing partial mitigation to the adverse effects of chronic Nr enrichment. BNF was suppressed by 69%, compared to rates in pristine bogs, but was still active, contributing ~2% of the N inputs. The long-term peat N storage rate (8.4 ± 0.8 kg N ha−1 y−1) cannot be met by the measured N mass balance, showing that the bog catchment is losing more N than it can store due its saturated status.

KW - N isotopes

KW - Atmospheric N deposition

KW - Biological nitrogen fixation

KW - Denitrification

KW - DON

KW - Peatbog

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DO - 10.1016/j.scitotenv.2021.147552

M3 - Article

AN - SCOPUS:85105827800

SN - 0048-9697

VL - 787

JO - Science of the Total Environment

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M1 - 147552

ER -

Chronic atmospheric reactive N deposition has breached the N sink capacity of a northern ombrotrophic peatbog increasing the gaseous and fluvial N losses

Abstract

Keywords

UN SDGs

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