The use of radiocarbon to constrain current and future soil organic matter turnover and transport in a temperate forest

Braakhekke, Maarten C.; Beer, Christian; Schrumpf, Marion; Ekici, Altug; Ahrens, Bernhard; Hoosbeek, Marcel R.; Kruijt, B.; Kabat, P.; Reichstein, Markus

doi:10.1002/2013jg002420

Cited by 35 publications

(41 citation statements)

References 97 publications

(105 reference statements)

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“…Our previous work with CLM4.5 showed that these resolved controls are insufficient to predict both observed total C and 14 C SOM profiles in temperate soils (23). This result is consistent with some (34), but not all (35), recent modeling analyses using similar vertically resolved carbon decomposition models. To address this issue, we defined in CLM4.5 an e-folding distance, Z τ , that modifies HR by decreasing the respiration flux from each pool as an exponential function of depth (23).…”

Section: Methodssupporting

confidence: 88%

Permafrost carbon−climate feedback is sensitive to deep soil carbon decomposability but not deep soil nitrogen dynamics

Koven

Lawrence

Riley

2015

Proc. Natl. Acad. Sci. U.S.A.

274

264

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Permafrost soils contain enormous amounts of organic carbon whose stability is contingent on remaining frozen. With future warming, these soils may release carbon to the atmosphere and act as a positive feedback to climate change. Significant uncertainty remains on the postthaw carbon dynamics of permafrost-affected ecosystems, in particular since most of the carbon resides at depth where decomposition dynamics may differ from surface soils, and since nitrogen mineralized by decomposition may enhance plant growth. Here we show, using a carbon−nitrogen model that includes permafrost processes forced in an unmitigated warming scenario, that the future carbon balance of the permafrost region is highly sensitive to the decomposability of deeper carbon, with the net balance ranging from 21 Pg C to 164 Pg C losses by 2300. Increased soil nitrogen mineralization reduces nutrient limitations, but the impact of deep nitrogen on the carbon budget is small due to enhanced nitrogen availability from warming surface soils and seasonal asynchrony between deeper nitrogen availability and plant nitrogen demands. Although nitrogen dynamics are highly uncertain, the future carbon balance of this region is projected to hinge more on the rate and extent of permafrost thaw and soil decomposition than on enhanced nitrogen availability for vegetation growth resulting from permafrost thaw.

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Section: Methodssupporting

confidence: 88%

Permafrost carbon−climate feedback is sensitive to deep soil carbon decomposability but not deep soil nitrogen dynamics

Koven

Lawrence

Riley

2015

Proc. Natl. Acad. Sci. U.S.A.

274

264

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“…For example, soil organic matter should be represented as vertically resolved (Braakhekke et al, 2011(Braakhekke et al, , 2014Koven et al, 2015;Beer, 2016), with different soil carbon pools and a moisturedependent decomposition. Furthermore, the site hydrology should include soil moisture contents above field capacity and standing water above the surface (Stacke and Hagemann, 2012).…”

Section: Discussionmentioning

confidence: 99%

Process-based modelling of the methane balance in periglacial landscapes (JSBACH-methane)

et al. 2017

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Abstract. A detailed process-based methane module for a global land surface scheme has been developed which is general enough to be applied in permafrost regions as well as wetlands outside permafrost areas. Methane production, oxidation and transport by ebullition, diffusion and plants are represented. In this model, oxygen has been explicitly incorporated into diffusion, transport by plants and two oxidation processes, of which one uses soil oxygen, while the other uses oxygen that is available via roots. Permafrost and wetland soils show special behaviour, such as variable soil pore space due to freezing and thawing or water table depths due to changing soil water content. This has been integrated directly into the methane-related processes. A detailed application at the Samoylov polygonal tundra site, Lena River Delta, Russia, is used for evaluation purposes. The application at Samoylov also shows differences in the importance of the several transport processes and in the methane dynamics under varying soil moisture, ice and temperature conditions during different seasons and on different microsites. These microsites are the elevated moist polygonal rim and the depressed wet polygonal centre. The evaluation shows sufficiently good agreement with field observations despite the fact that the module has not been specifically calibrated to these data. This methane module is designed such that the advanced land surface scheme is able to model recent and future methane fluxes from periglacial landscapes across scales. In addition, the methane contribution to carbon cycleclimate feedback mechanisms can be quantified when running coupled to an atmospheric model.

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“…However, the resulting total CH 4 emissions with the three tested snow threshold depths were not statistically different. The JSBACH-methane model does not explicitly consider some mechanisms related to the 930 carbon decomposition and thaw in Arctic permafrost and wetland ecosystems, such as: CH 4 production in the soil from root exudates (Knoblauch et al, 2016;Ström et al, 2012), vertical transfer of carbon and its vertically resolved decomposition (Braakhekke et al, 2011(Braakhekke et al, , 2013(Braakhekke et al, and 2014Koven et al, 2015), and microbial community dynamics (McCalley et al, 2014) involved in anoxic CH 4 oxidation or the production of CH 4 in anaerobic microsites confined 935 in oxic soils. Although these processes might contribute substantially to the dynamics of CH 4 , research on these processes in soil-permafrost and wetland environments is still lacking or poorly understood with controversial results so far (Bridgham et al, 2013).…”

Section: Model Spatial Heterogeneitymentioning

confidence: 99%

“…KCM wishes to thank Andrew Durso for the English proofread of this manuscript. (Braakhekke et al, 2011;Braakhekke et al, 2014;Braakhekke et al, 2013;Koven et al, 2015;Sachs et al, 2010;Wille et al, 2008;Xu et al, 2016) Tuomi et al, 2009) 1290 Table 2. Daily methane emissions for the individual transport pathways and total methane emissions are shown.…”

Section: Acknowledgementsmentioning

confidence: 99%

Year-round simulated methane emissions from a permafrost ecosystem in Northeast Siberia

Castro-Morales¹,

Kleinen²,

Kaiser³

et al. 2017

Preprint

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15Methane emissions to the atmosphere from natural wetlands are estimated to be about 25 % of the total global CH 4 emissions. In the Arctic, these areas are highly vulnerable to the effects of global warming due to atmospheric warming amplification, leading to soil hydrologic changes involving permafrost thaw, formation of deeper active layers, and rising topsoil temperatures. As a result, projected increase in the degradation of permafrost carbon will likely 20 lead to higher CO 2 and CH 4 emissions from these areas. Here we evaluate year-round modelsimulated CH 4 emissions to the atmosphere (for 2014 and 2015) from a region of northeastern Siberia in the Russian Far East. Four CH 4 transport pathways are modeled with a revisited version of the process-based JSBACH-methane model: plant-mediated transport, ebullition and molecular diffusion in the presence or absence of snow. This model also simulates 25 the extent of wetlands as the fraction of inundated area in a model grid cell using a TOP-MODEL approach, and these are evaluated against a highly resolved wetland product from remote sensing data. The model CH 4 emissions are compared against ground-based CH 4 flux measurements using the eddy covariance technique and flux chambers in the same area of study. The magnitude of the summertime modeled CH 4 emissions is comparable to those 30 from eddy covariance and flux chamber measurements. However, wintertime modeled CH 4 emissions are underestimated by one order of magnitude. The annual CH 4 emissions are dominated by plant-mediated transport (61 %), followed by ebullition (~35 %). Molecular diffusion of CH 4 from the soil into the atmosphere during summer is negligible (0.02 %) compared to the diffusion through the snow during the non-growing season (~4 %). vestigate the relationship between temporal changes in the CH 4 fluxes, soil temperature, and soil moisture content. Our results highlight the heterogeneity in CH 4 emissions at a landscape scale and suggest that further improvements to the representation of large-scale hydrological Biogeosciences Discuss., https://doi.org/10.5194/bg-2017-310 Manuscript under review for journal Biogeosciences Discussion started: 24 July 2017 c Author(s) 2017. CC BY 4.0 License.2 conditions in the model, especially at regional scales in Arctic ecosystems influenced by permafrost thaw, will allow us to arrive at a more process-oriented land surface scheme and 40 better simulate CH 4 emissions under climate change.Keywords: methane, permafrost, carbon cycle, Arctic, wetlands, winter emissions IntroductionDuring the last 30 years, atmospheric temperatures at northern high-latitudes have risen more 45 than the global average (Schuur et al., 2015; Serreze et al., 2000). In consequence, many permafrost areas in these regions have experienced expedited thawing rates in recent years.Permafrost in northern high-latitude ecosystems contains twice as much carbon as the current carbon pool in the atmosphere and about half of global soil organic carbon (Hugelius et al., 2...

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The use of radiocarbon to constrain current and future soil organic matter turnover and transport in a temperate forest

Cited by 35 publications

References 97 publications

Permafrost carbon−climate feedback is sensitive to deep soil carbon decomposability but not deep soil nitrogen dynamics

Permafrost carbon−climate feedback is sensitive to deep soil carbon decomposability but not deep soil nitrogen dynamics

Process-based modelling of the methane balance in periglacial landscapes (JSBACH-methane)

Year-round simulated methane emissions from a permafrost ecosystem in Northeast Siberia

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