Effects of permafrost aggradation on peat properties as determined from a pan‐Arctic synthesis of plant macrofossils

Treat, Claire C.; Jones, Miriam C.; Camill, Philip; Gallego‐Sala, Angela; Garneau, Michelle; Harden, Jennifer W.; Hugelius, Gustaf; Klein, E. S.; Kokfelt, Ulla; Kuhry, Peter; Loisel, Julie; Mathijssen, Paul; O’Donnell, J. A.; Oksanen, Pirita; Ronkainen, Tiina; Sannel, A. Britta K.; Talbot, Julie; Tarnocai, C.; Väliranta, Minna

doi:10.1002/2015jg003061

Cited by 100 publications

(145 citation statements)

References 106 publications

(215 reference statements)

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“…Treat et al () compiled a database of 273 peat samples from the permafrost tundra zone and found mean values of peat C content of 39.5 ± 9.0%, C:N ratios of 34 ± 18, and a DBD of 0.16 ± 0.21 g cm −3 , in the range of our mean values for the 10 peat samples from Abisko (Figure ).…”

Section: Discussionsupporting

confidence: 66%

Short and Long‐Term Controls on Active Layer and Permafrost Carbon Turnover Across the Arctic

et al. 2018

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Decomposition of soil organic matter (SOM) in permafrost terrain and the production of greenhouse gases is a key factor for understanding climate change‐carbon feedbacks. Previous studies have shown that SOM decomposition is mostly controlled by soil temperature, soil moisture, and carbon‐nitrogen ratio (C:N). However, focus has generally been on site‐specific processes and little is known about variations in the controls on SOM decomposition across Arctic sites. For assessing SOM decomposition, we retrieved 241 samples from 101 soil profiles across three contrasting Arctic regions and incubated them in the laboratory under aerobic conditions. We assessed soil carbon losses (Closs) five times during a 1 year incubation. The incubated material consisted of near‐surface active layer (ALNS), subsurface active layer (ALSS), peat, and permafrost samples. Samples were analyzed for carbon, nitrogen, water content, δ13C, δ15N, and dry bulk density (DBD). While no significant differences were observed between total ALSS and permafrost Closs over 1 year incubation (2.3 ± 2.4% and 2.5 ± 1.5% Closs, respectively), ALNS samples showed higher Closs (7.9 ± 4.2%). DBD was the best explanatory parameter for active layer Closs across sites. Additionally, results of permafrost samples show that C:N ratio can be used to characterize initial Closs between sites. This data set on the influence of abiotic parameter on microbial SOM decomposition can improve model simulations of Arctic soil CO2 production by providing representative mean values of CO2 production rates and identifying standard parameters or proxies for upscaling potential CO2 production from site to regional scales.

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Section: Discussionsupporting

confidence: 66%

Short and Long‐Term Controls on Active Layer and Permafrost Carbon Turnover Across the Arctic

et al. 2018

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“…In the bottom part of both peat sequences the main peat‐forming plants included Cyperaceae (Figure , phase A; Figure , phases A and B). The presence of Carex fruits and rootlets, as well as brown mosses in both sites indicates that during this period the peatlands operated as fens, a widespread wetland type in the permafrost area of the northern hemisphere (Vardy et al , ; Kuhry, ; Teltewskoi et al , ; Treat et al , ). Pollen data indicate that between 2650 and 2300 cal yr BP the non‐peatland community at Marooned was dominated by Betula .…”

Section: Discussionmentioning

confidence: 93%

Vegetation Succession, Carbon Accumulation and Hydrological Change in Subarctic Peatlands, Abisko, Northern Sweden

Gałka

Szal

Watson

et al. 2017

Permafrost & Periglacial

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High‐resolution analyses of plant macrofossils, testate amoebae, pollen, mineral content, bulk density, and carbon and nitrogen were undertaken to examine the late Holocene dynamics of two permafrost peatlands in Abisko, Subarctic Sweden. The peat records were dated using tephrochronology, 14C and 210Pb. Local plant succession and hydrological changes in peatlands were synchronous with climatic shifts, although autogenous plant succession towards ombrotrophic status during peatland development was also apparent. The Marooned peatland experienced a shift ca. 2250 cal yr BP from rich to poor fen, as indicated by the appearance of Sphagnum fuscum. At Stordalen, a major shift to wetter conditions occurred between 500 and 250 cal yr BP, probably associated with climate change during the Little Ice Age. During the last few decades, the testate amoeba data suggest a deepening of the water table and an increase in shrub pollen, coinciding with recent climate warming and the associated expansion of shrub communities across the Arctic. Rates of carbon accumulation vary greatly between the sites, illustrating the importance of local vegetation communities, hydrology and permafrost dynamics. Multiproxy data elucidate the palaeoecology of S. lindbergii and show that it indicates wet conditions in peatlands. Copyright © 2017 John Wiley & Sons, Ltd.

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“…Within a radius of 350 m around the landscaper tower, 21% of the land surface was classified as transition zone. Due to their differing hydrology, vegetation composition, and nutrient availability, CO 2 flux dynamics of fens most likely differ from CO 2 flux dynamics of collapse-scar bogs (e.g., Bubier, 1995;Yu, 2006;Treat et al, 2016). Transition zones are part of the wetland land cover type and their definition is to some extent arbitrary, as a reference year (here 1977, the first year of available aerial photography) is used to differentiate between gradual transition zones and interior wetlands.…”

Section: Eddy Covariance Measurementsmentioning

confidence: 99%

“…In contrast to changes in T a and precipitation, SW in is more strongly bound to latitude. A shift from permafrost peatland landscapes with large organic C stocks [mean of 106 kg m À2 AE45 (AEone standard deviation) for forested permafrost plateaus (n = 158); 117 kg m À2 AE 65 for collapse-scar bogs (n = 52); data from Treat et al, 2016] to landscapes with low C stocks would result in large net CO 2 emissions. S6) is therefore likely to increase ER more than GPP, particularly for the RCP8.5 scenario (Fig.…”

Section: Direct Climate Change Impacts On Carbon Dioxide Fluxesmentioning

confidence: 99%

“…Along the southern limit of the North American permafrost zone, long-term net CO 2 uptake has resulted in large organic C stocks as peat (Robinson & Moore, 1999;Tarnocai et al, 2009;Treat et al, 2016). In these organic-rich boreal landscapes, thawing permafrost makes previously frozen organic C stocks available for decomposition and ER may be enhanced by warming soils O'Donnell et al, 2012;Natali et al, 2014;Treat et al, 2014;Koven et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

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Direct and indirect climate change effects on carbon dioxide fluxes in a thawing boreal forest–wetland landscape

Helbig

Chasmer

Desai

et al. 2017

Global Change Biology

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In the sporadic permafrost zone of northwestern Canada, boreal forest carbon dioxide (CO ) fluxes will be altered directly by climate change through changing meteorological forcing and indirectly through changes in landscape functioning associated with thaw-induced collapse-scar bog ('wetland') expansion. However, their combined effect on landscape-scale net ecosystem CO exchange (NEE ), resulting from changing gross primary productivity (GPP) and ecosystem respiration (ER), remains unknown. Here, we quantify indirect land cover change impacts on NEE and direct climate change impacts on modeled temperature- and light-limited NEE of a boreal forest-wetland landscape. Using nested eddy covariance flux towers, we find both GPP and ER to be larger at the landscape compared to the wetland level. However, annual NEE (-20 g C m ) and wetland NEE (-24 g C m ) were similar, suggesting negligible wetland expansion effects on NEE . In contrast, we find non-negligible direct climate change impacts when modeling NEE using projected air temperature and incoming shortwave radiation. At the end of the 21st century, modeled GPP mainly increases in spring and fall due to reduced temperature limitation, but becomes more frequently light-limited in fall. In a warmer climate, ER increases year-round in the absence of moisture stress resulting in net CO uptake increases in the shoulder seasons and decreases during the summer. Annually, landscape net CO uptake is projected to decline by 25 ± 14 g C m for a moderate and 103 ± 38 g C m for a high warming scenario, potentially reversing recently observed positive net CO uptake trends across the boreal biome. Thus, even without moisture stress, net CO uptake of boreal forest-wetland landscapes may decline, and ultimately, these landscapes may turn into net CO sources under continued anthropogenic CO emissions. We conclude that NEE changes are more likely to be driven by direct climate change rather than by indirect land cover change impacts.

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Effects of permafrost aggradation on peat properties as determined from a pan‐Arctic synthesis of plant macrofossils

Cited by 100 publications

References 106 publications

Short and Long‐Term Controls on Active Layer and Permafrost Carbon Turnover Across the Arctic

Short and Long‐Term Controls on Active Layer and Permafrost Carbon Turnover Across the Arctic

Vegetation Succession, Carbon Accumulation and Hydrological Change in Subarctic Peatlands, Abisko, Northern Sweden

Direct and indirect climate change effects on carbon dioxide fluxes in a thawing boreal forest–wetland landscape

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