Organic matter composition and stabilization in a polygonal tundra soil of the Lena Delta

Höfle, Silke T.; Rethemeyer, Janet; Mueller, Carsten W.; John, Stephan

doi:10.5194/bg-10-3145-2013

Cited by 77 publications

(75 citation statements)

References 68 publications

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“…These carbon values are much higher than observed in other types of Arctic soils. For example, the carbon content of active layer soil from a polygonal tundra of the Lena Delta ranged from 1.5 to 3 % dry-weight (Höfle et al, 2013), an order of magnitude less than values in the SAS soil. Lower carbon concentrations were also measured in a study of permafrost soils of the Arctic tundra of Northwest Territories, which were 6.5 % C (Moquin and Wrona, 2015), and in the lithalsa mounds surrounding BGR1 (Fig.…”

Section: Organic Carbon Enrichmentmentioning

confidence: 85%

Bacterial production in subarctic peatland lakes enriched by thawing permafrost

et al. 2016

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Abstract. Peatlands extend over vast areas of the northern landscape. Within some of these areas, lakes and ponds are changing in size as a result of permafrost thawing and erosion, resulting in mobilization of the carbon-rich peatland soils. Our aims in the present study were to characterize the particle, carbon and nutrient regime of a set of thermokarst (thaw) lakes and their adjacent peatland permafrost soils in a rapidly degrading landscape in subarctic Québec, Canada, and by way of fluorescence microscopy, flow cytometry, production measurements and an in situ enrichment experiment, determine the bacterial characteristics of these waters relative to other thaw lakes and rock-basin lakes in the region. The soil active layer in a degrading palsa (peatland permafrost mound) adjacent to one of the lakes contained an elevated carbon content (51 % of dry weight), high C : N ratios (17 : 1 by mass), and large stocks of other elements including N (3 % of dry weight), Fe (0.6 %), S (0.5 %), Ca (0.5 %) and P (0.05 %). Two permafrost cores were obtained to a depth of 2.77 m in the palsa, and computerized tomography scans of the cores confirmed that they contained high concentrations (> 80 %) of ice. Upon thawing, the cores released nitrate and dissolved organic carbon (from all core depths sampled), and soluble reactive phosphorus (from bottom depths), at concentrations well above those in the adjacent lake waters. The active layer soil showed a range of particle sizes with a peak at 229 µm, and this was similar to the distribution of particles in the upper permafrost cores. The particle spectrum for the lake water overlapped with those for the soil, but extended to larger (surface water) or finer (bottom water) particles. On average, more than 50 % of the bacterial cells and bacterial production was associated with particles > 3 µm. This relatively low contribution of free-living cells (operationally defined as the < 1 µm fraction) to bacterial production was a general feature of all of the northern lakes sampled, including other thaw lakes and shallow rock-basin lakes (average ± SE of 25 ± 6 %). However, a distinguishing feature of the peatland thaw lakes was significantly higher bacterial specific growth rates, which averaged 4 to 7 times higher values than in the other lake types. The in situ enrichment experiment showed no difference between organic carbon or phosphorus enrichment treatments at day 5 relative to the control, however there was an apparent increase in bacterial growth rates between days 1 and 5 in the soil and the carbon plus phosphorus enrichments. Collectively these results indicate that particles, nutrients and carbon are released by degrading permafrost peatland soils into their associated thermokarst lakes, creating favorable conditions for production by particle-based as well as free-living aquatic bacterial communities. The reduced bacterial concentrations despite high cellular growth rates imply that there is control of their population size by loss-related factors such as grazing and vira...

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Section: Organic Carbon Enrichmentmentioning

confidence: 85%

Bacterial production in subarctic peatland lakes enriched by thawing permafrost

et al. 2016

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“…Hence, in permafrost soils, organic matter is often preserved in a relatively undecomposed state, both in surface horizons and in buried forms (e.g., peat deposits, cryoturbated organic matter). In addition, much of this organic matter is uncomplexed or only poorly associated with soil minerals (Diochon et al, 2013;Höfle et al, 2013). Furthermore, subzero microbial activity in unfrozen water films can lead to accumulation of easily decomposable, soluble microbial by-products in frozen soils.…”

Section: Characterization Of the Quality And Decomposability Of Organmentioning

confidence: 99%

“…Chemical characterization studies have run the gamut of methodologies in efforts to assess the current state of degradation -from wet chemical fractionations (acid/base extractions, molecular biomarkers, and water or solvent extractions; e.g., Uhlířová et al, 2007;Paulter et al, 2010;Hugelius et al, 2012) to various types of spectrochemical analysis (nuclear magnetic resonance spectroscopy, pyrolysis-gas chromatography/mass spectrometry, mid-infrared spectroscopy; e.g., Dai et al, 2002a, b;Andersen and White, 2006;Waldrop et al, 2010;Pedersen et al, 2011;Pengerud et al, 2013). Even though organomineral associations might play a role in the relative persistence of SOM upon thawing and warming (Davidson and Janssens, 2006), relatively few studies have employed physical fractionations to characterize the amount of SOC stabilized by mineral associations or by aggregation (e.g., Dutta et al, 2006;Xu et al, 2009a, b;Höfle et al, 2013).…”

Section: Characterization Of the Quality And Decomposability Of Organmentioning

confidence: 99%

“…For similar horizons in two Alaskan Turbels, Xu et al (2009a, b) reported even greater proportions of total SOC (> 70 %) in the POM fractions, and analysis of this material by pyrolysis-gas chromatography/mass spectrometry indicated that it was only lightly decomposed. Moreover, Höfle et al (2013) concluded that organomineral associations and aggregation are of lesser importance for SOM stabilization in permafrost soils than in temperate and tropical soils. Indeed, this is not surprising, because most clay minerals in Arctic tundra soils are inherent from the parent material rather than pedogenic (Borden et al, 2010).…”

Section: Characterization Of the Quality And Decomposability Of Organmentioning

confidence: 99%

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Permafrost soils and carbon cycling

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Jorgenson

et al. 2015

SOIL

264

188

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Abstract. Knowledge of soils in the permafrost region has advanced immensely in recent decades, despite the remoteness and inaccessibility of most of the region and the sampling limitations posed by the severe environment. These efforts significantly increased estimates of the amount of organic carbon stored in permafrost-region soils and improved understanding of how pedogenic processes unique to permafrost environments built enormous organic carbon stocks during the Quaternary. This knowledge has also called attention to the importance of permafrost-affected soils to the global carbon cycle and the potential vulnerability of the region's soil organic carbon (SOC) stocks to changing climatic conditions. In this review, we briefly introduce the permafrost characteristics, ice structures, and cryopedogenic processes that shape the development of permafrost-affected soils, and discuss their effects on soil structures and on organic matter distributions within the soil profile. We then examine the quantity of organic carbon stored in permafrost-region soils, as well as the characteristics, intrinsic decomposability, and potential vulnerability of this organic carbon to permafrost thaw under a warming climate. Overall, frozen conditions and cryopedogenic processes, such as cryoturbation, have slowed decomposition and enhanced the sequestration of organic carbon in permafrost-affected soils over millennial timescales. Due to the low temperatures, the organic matter in permafrost soils is often less humified than in more temperate soils, making some portion of this stored organic carbon relatively vulnerable to mineralization upon thawing of permafrost.

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“…This is indicated by a significant decrease of C/N-ratios from 16 to 8 (TOC/TN) and 15 to 8 (DOC/DN). POC fractions within the TOC pool which are subject to less degradation, could be sorbed to mineral particles and protected by organo-mineral bonds, potentially stabilizing OM (Höfle et al, 2013;Huguet et al, 2008;Keil et al, 1994). The narrow ratios, especially for the DOC fraction in the mudpool and transition zone, reflect the high mineralization rates of OM.…”

Section: Processes After Initial Slumpingmentioning

confidence: 99%