Interacting effects of vegetation components and water level on methane dynamics in a boreal fen

Riutta, Terhi; Korrensalo, Aino; Laine, Anna; Laine, Jukka; Tuittila, Eeva‐Stiina

doi:10.5194/bg-17-727-2020

Cited by 25 publications

(25 citation statements)

References 80 publications

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“…Instead, our findings are similar to patterns observed in other studies. WTD is a wellrecognized driver of CH 4 emissions Updegraff et al, 2001;Blodau et al, 2004;Turetsky et al, 2014;Riutta et al, 2020). Shallow WTD promote CH 4 emissions because methanogenesis requires anaerobic conditions, while deep WTD increases the portion of aerated surface peat accommodating consumption of CH 4 by methanotrophs as it diffuses toward the atmosphere Sundh et al, 1995).…”

Section: Methane Emissionsmentioning

confidence: 99%

Come Rain, Come Shine: Peatland Carbon Dynamics Shift Under Extreme Precipitation

Barel

Moulia

Hamard

et al. 2021

Front. Environ. Sci.

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Precipitation patterns are becoming increasingly extreme, particularly at northern latitudes. Current climate models predict that this trend will continue in the future. While droughts have been repeatedly studied in many ecosystems over the last decades, the consequences of increasingly intense, but less frequent rainfall events, on carbon (C) cycling are not well understood. At northern latitudes, peatlands store one third of the terrestrial carbon and their functioning is highly dependent on water. Shifts in rainfall regimes could disrupt peatland C dynamics and speed-up the rates of C loss. How will these immense stocks of C be able to withstand and recover from extreme rainfall? We tested the resistance and resilience effects of extreme precipitation regimes on peatland carbon dioxide (CO2) and methane (CH4) fluxes, pore water dissolved organic carbon (DOC) and litter decomposition rates by exposing intact peat cores to extreme, spring-time rainfall patterns in a controlled mesocosm experiment. We find that more intense but less frequent rainfall destabilized water table dynamics, with cascading effects on peatland C fluxes. Decomposition and respiration rates increased with a deeper mean water table depth (WTD) and larger WTD fluctuations. We observed similar patterns for CO2 uptake, which were likely mediated by improved vascular plant performance. After a three-week recovery period, CO2 fluxes still displayed responses to the earlier WTD dynamics, suggesting lagged effects of precipitation regime shifts. Furthermore, we found that CH4 emissions decreased with deeper mean WTD, but this showed a high resilience once WTD dynamics stabilised. Not only do our results illustrate that shifting rainfall patterns translate in altered WTD dynamics and, consequentially, influence C fluxes, they also demonstrate that exposure to altered rainfall early in the growing season can have lasting effects on CO2 exchange. Even though the increased CO2 assimilation under extreme precipitation patterns signals peatland resistance under changing climatic conditions, it may instead mark the onset of vascular plant encroachment and the associated C loss.

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Section: Methane Emissionsmentioning

confidence: 99%

Come Rain, Come Shine: Peatland Carbon Dynamics Shift Under Extreme Precipitation

Barel

Moulia

Hamard

et al. 2021

Front. Environ. Sci.

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“…In addition to the direct effects of climate and hydrology on peatland C cycling and autogenic hydrological feedbacks that occur within peatlands (Waddington et al, 2015), changes in temperature and water table also indirectly influence C cycling through changes in the relative abundance and productivity of dominant plant functional types (PFTs; bryophyte, graminoid and ericoid) (Gavazov et al, 2018; Laine et al, 2011; Riutta, Korrensalo, Laine, Laine, & Tuittila, 2020). Warmer and drier conditions are predicted to favour a shift from bryophyte to vascular plant dominance (Buttler et al, 2015; Dieleman, Branfireun, McLaughlin, & Lindo, 2015; Walker, Ward, Ostle, & Bardgett, 2015), with implications for microclimates and GHG emissions (Gavazov et al, 2018; Radu & Duval, 2018; Robroek et al, 2015; Ward et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

Plant functional type indirectly affects peatland carbon fluxes and their sensitivity to environmental change

Whitaker

Richardson

Ostle

et al. 2020

European J Soil Science

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The sensitivity of peatland carbon (C) fluxes to changes in climate and hydrology are uncertain due to the complex interactions between plants and peat properties. In this study we examine how peat cores taken from under three plant functional types (PFT) (bryophyte, graminoid and ericoid) differ in their biotic and abiotic properties and how this indirectly modulates the response of C fluxes to environmental change. Peat cores taken from under three PFTs had their aboveground vegetation removed to exclude direct plant‐mediated effects, and were incubated in a temperature × water table factorial experiment at 12, 14 and 16°C (air temperature) with the water table level −25, −15 or −5 cm below the peat surface. Carbon dioxide (CO2) and methane (CH4) fluxes were measured over 11 months. Emissions of CO2 and CH4 increased with temperature, with strong positive (CH4) and negative (CO2) interactions with increasing water table level. There were significant effects of removed PFT on the environmental sensitivity of CH4, but not CO2 fluxes. CH4 emissions were greatest in peat with graminoid PFT removed at the warmest temperature but these indirect effects were not explained by peat abiotic or biotic properties, which did not differ between PFTs. These results show that climate change‐induced expansion of graminoids in northern peatlands will have direct and indirect effects on C fluxes and the stability of peatland C stores. These responses will be determined by the interactive effects of vegetation composition, hydrology and warming on methane‐cycling microbial communities.Highlights Peatland carbon flux strength under a changing climate is influenced by PFT. Peat from under graminoid PFT emits more methane than peat from under bryophyte or ericoid PFT. Prior PFT cover influenced methane emissions, but did not affect peat abiotic or biotic properties. Increases in graminoid cover with climate change could indirectly increase peatland methane fluxes.

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“…the impact of the stream was again predominant over the impact of LAI. Studies have shown that shrubs can hinder CH4 production because of their poor-quality substrate for methanogenesis (Riutta et al, 2020, Yavitt et al, 2019, although the cover of shrubs at our study site was very small.…”

Section: Role Of Stream-induced Microhabitats In Driving Ch4 Emissionsmentioning

confidence: 66%

“…temperature or vegetation composition alone (Laine et al, 2019;Mäkiranta et al, 2018;Riutta et al, 2020). In addition to vertical water level changes, the lateral flow of water in fens can be even more important in driving the processes that underpin CH4 emissions, because flowing water not only ensures a water supply for the vegetation, but also transports nutrients, which benefits vegetation and microbial communities (Laitinen et al, 2007).…”

mentioning

confidence: 99%

Water Flow Controls the Spatial Variability of Methane Emissions in a Northern Valley Fen Ecosystem

Zhang¹,

Tuittila²,

Korrensalo³

et al. 2020

Preprint

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Abstract. Northern peatlands are projected to be crucial in future atmospheric methane (CH4) budgets and have a positive feedback on global warming. Fens receive nutrients from catchments via inflowing water and are more sensitive than bogs to climate change-caused variations in their ecohydrology. Yet, due to a lack of data detailing the impacts of moving water on microhabitats and CH4 fluxes in fens, there remains large uncertainties in predicting CH4 emissions from these sites. We measured CH4 fluxes with manual chambers over three growing seasons (2017–2019) at a northern boreal fen. To address the spatial variation at the site where a stream flows through the long and narrow valley fen, we established sample plots at varying distances from the stream. To link the variations in CH4 emissions to environmental controls, we quantified water levels, peat temperature, dissolved oxygen concentration, vegetation composition and leaf area index in combination with flux measurements during the growing season in 2019. We found that due to the flowing water, there was a higher water level, lower peat temperatures, and more oxygen in the peat close to the stream, which also had the highest total leaf area and gross primary production (GPP) values but the lowest CH4 emissions. Further from the stream, the conditions were drier and produced low CH4 emissions. In contrast, CH4 emissions were highest at an intermediate distance from the stream where the oxygen concentration in the surface peat was low but GPP was still high. Our results emphasise the key role of ecohydrology in CH4 dynamics in fens, and for the first time show how a stream controls CH4 emissions in a flow-through fen. As valley fens are common peatland ecosystems from the arctic to the temperate zones, future projections of global CH4 budgets need to take flowing water features into account.

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Interacting effects of vegetation components and water level on methane dynamics in a boreal fen

Cited by 25 publications

References 80 publications

Come Rain, Come Shine: Peatland Carbon Dynamics Shift Under Extreme Precipitation

Come Rain, Come Shine: Peatland Carbon Dynamics Shift Under Extreme Precipitation

Plant functional type indirectly affects peatland carbon fluxes and their sensitivity to environmental change

Water Flow Controls the Spatial Variability of Methane Emissions in a Northern Valley Fen Ecosystem

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