Spatially varying peatland initiation, Holocene development, carbon accumulation patterns and radiative forcing within a subarctic fen

Piilo, Sanna; Korhola, Atte; Heiskanen, Lauri; Tuovinen, Juha‐Pekka; Aurela, Mika; Juutinen, Sari; Marttila, Hannu; Saari, Mohd Yusof; Tuittila, Eeva‐Stiina; Turunen, Jukka; Väliranta, Minna

doi:10.1016/j.quascirev.2020.106596

Cited by 26 publications

(36 citation statements)

References 103 publications

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“…Radiative forcing of peatlands across the Holocene indicates that due to net C accumulation, they have had a cooling impact on the atmosphere for the last 11 000 years [ 25 , 26 ]. As permafrost peatlands thaw, this cooling trend could change at least until ecosystems equilibrate to a new steady state [ 27 ], however, this is likely to occur heterogeneously across Arctic landscapes [ 26 ]. At Stordalen Mire, relatively small changes in per cent cover of highly productive sedges had a large impact on the net radiative forcing.…”

Section: Discussionmentioning

confidence: 99%

“…Net radiative forcing can be estimated using landcover classification along with gas exchange rates and global warming potential values derived using laboratory and modelling techniques [ 24 ]. Long-term evaluation of climate forcing over the Holocene indicates that peatland formation has had a cooling impact on our climate due to the high rates of CO 2 fixation overwhelming the warming impact of CH 4 emissions [ 25 , 26 ]. Using this approach is critical for understanding the climate feedbacks of thawing permafrost regions which over time have the potential to exchange large amounts of both CO 2 and CH 4 with the atmosphere and with current rates of thawing shift these ecosystems from net cooling to net warming [ 27 ].…”

Section: Introductionmentioning

confidence: 99%

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Permafrost thaw driven changes in hydrology and vegetation cover increase trace gas emissions and climate forcing in Stordalen Mire from 1970 to 2014

Varner

Crill

Frolking

et al. 2021

Phil. Trans. R. Soc. A.

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Permafrost thaw increases active layer thickness, changes landscape hydrology and influences vegetation species composition. These changes alter belowground microbial and geochemical processes, affecting production, consumption and net emission rates of climate forcing trace gases. Net carbon dioxide (CO 2 ) and methane (CH 4 ) fluxes determine the radiative forcing contribution from these climate-sensitive ecosystems. Permafrost peatlands may be a mosaic of dry frozen hummocks, semi-thawed or perched sphagnum dominated areas, wet permafrost-free sedge dominated sites and open water ponds. We revisited estimates of climate forcing made for 1970 and 2000 for Stordalen Mire in northern Sweden and found the trend of increasing forcing continued into 2014. The Mire continued to transition from dry permafrost to sedge and open water areas, increasing by 100% and 35%, respectively, over the 45-year period, causing the net radiative forcing of Stordalen Mire to shift from negative to positive. This trend is driven by transitioning vegetation community composition, improved estimates of annual CO 2 and CH 4 exchange and a 22% increase in the IPCC's 100-year global warming potential (GWP_100) value for CH 4 . These results indicate that discontinuous permafrost ecosystems, while still remaining a net overall sink of C, can become a positive feedback to climate change on decadal timescales. This article is part of a discussion meeting issue ‘Rising methane: is warming feeding warming? (part 2)’.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Permafrost thaw driven changes in hydrology and vegetation cover increase trace gas emissions and climate forcing in Stordalen Mire from 1970 to 2014

Varner

Crill

Frolking

et al. 2021

Phil. Trans. R. Soc. A.

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“…Moreover, further research is needed to assess the impact of recent climate-driven fen-bog transitions and Sphagnum expansion on the net ecosystem carbon budget in northern peatlands and radiative forcing effect (e.g. Johansson et al, 2006;Mathijssen et al, 2017;Piilo et al, 2020). Our study highlights the importance of considering the ecohydrological trajectories in response to recent warming when modelling the potential contribution of peatlands to climate change (e.g.…”

Section: Implications Of Ecosystem Shifts For Peatland Carbon Sequestrationmentioning

confidence: 94%

Widespread recent ecosystem state shifts in high‐latitude peatlands of northeastern Canada and implications for carbon sequestration

Magnan

Sanderson

Piilo

et al. 2021

Global Change Biology

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Northern peatlands are a major component of the global carbon (C) cycle. Widespread climate-driven ecohydrological changes in these ecosystems can have major consequences on their C sequestration function. Here, we synthesize plant macrofossil data from 33 surficial peat cores from different ecoclimatic regions, with high-resolution chronologies. The main objectives were to document recent ecosystem state shifts and explore their impact on C sequestration in high-latitude undisturbed peatlands of northeastern Canada. Our synthesis shows widespread recent ecosystem shifts in peatlands, such as transitions from oligotrophic fens to bogs and Sphagnum expansion, coinciding with climate warming which has also influenced C accumulation during the last ~100 years. The rapid shifts towards drier bog communities and an expansion of Sphagnum sect. Acutifolia after 1980 CE were most pronounced in the northern subarctic sites and are concurrent with summer warming in northeastern Canada. These results provide further evidence of a northward migration of Sphagnum-dominated peatlands in North America in response to climate change. The results also highlight differences in the timing of ecosystem shifts among peatlands and regions, reflecting internal peatland dynamics and varying responses of vegetation communities. Our study suggests that the recent rapid climate-driven shifts from oligotrophic fen to drier bog communities have promoted plant productivity and thus peat C accumulation. We highlight the importance of considering recent ecohydrological trajectories when modelling the potential contribution of peatlands to climate change. Our study suggests that, contrary to expectations, peat C sequestration could be promoted in high-latitude non-permafrost peatlands where wet sedge fens may transition to drier Sphagnum bog communities due to warmer and longer growing seasons.

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“…To evaluate the relative impact of each explanatory variable, the standardised regression coefficients were calculated, while the marginal coefficient of determination (R 2 m ) was used to quantify how much the fixed effects explain of the variance of the response variable. Data analyses were conducted in R (R Core Team, 2019) with the packages nlme (Pinheiro et al, 2019), MASS (Venables and Ripley, 2002) and reghelper (Hughes, 2020).…”

Section: Linear Mixed-effects Modelsmentioning

confidence: 99%

Carbon dioxide and methane exchange of a patterned subarctic fen during two contrasting growing seasons

et al. 2021

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Abstract. The patterned microtopography of subarctic mires generates a variety of environmental conditions, and carbon dioxide (CO2) and methane (CH4) dynamics vary spatially among different plant community types (PCTs). We studied the CO2 and CH4 exchange between a subarctic fen and the atmosphere at Kaamanen in northern Finland based on flux chamber and eddy covariance measurements in 2017–2018. We observed strong spatial variation in carbon dynamics between the four main PCTs studied, which were largely controlled by water table level and differences in vegetation composition. The ecosystem respiration (ER) and gross primary productivity (GPP) increased gradually from the wettest PCT to the drier ones, and both ER and GPP were larger for all PCTs during the warmer and drier growing season 2018. We estimated that in 2017 the growing season CO2 balances of the PCTs ranged from −20 g C m−2 (Trichophorum tussock PCT) to 64 g C m−2 (string margin PCT), while in 2018 all PCTs were small CO2 sources (10–22 g C m−2). We observed small growing season CH4 emissions (< 1 g C m−2) from the driest PCT, while the other three PCTs had significantly larger emissions (mean 7.9, range 5.6–10.1 g C m−2) during the two growing seasons. Compared to the annual CO2 balance (−8.5 ± 4.0 g C m−2) of the fen in 2017, in 2018 the annual balance (−5.6 ± 3.7 g C m−2) was affected by an earlier onset of photosynthesis in spring, which increased the CO2 sink, and a drought event during summer, which decreased the sink. The CH4 emissions were also affected by the drought. The annual CH4 balance of the fen was 7.3 ± 0.2 g C m−2 in 2017 and 6.2 ± 0.1 g C m−2 in 2018. Thus, the carbon balance of the fen was close to zero in both years. The PCTs that were adapted to drier conditions provided ecosystem-level resilience to carbon loss due to water level drawdown.

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Spatially varying peatland initiation, Holocene development, carbon accumulation patterns and radiative forcing within a subarctic fen

Cited by 26 publications

References 103 publications

Permafrost thaw driven changes in hydrology and vegetation cover increase trace gas emissions and climate forcing in Stordalen Mire from 1970 to 2014

Permafrost thaw driven changes in hydrology and vegetation cover increase trace gas emissions and climate forcing in Stordalen Mire from 1970 to 2014

Widespread recent ecosystem state shifts in high‐latitude peatlands of northeastern Canada and implications for carbon sequestration

Carbon dioxide and methane exchange of a patterned subarctic fen during two contrasting growing seasons

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