scholarly journals The undetected loss of aged carbon from boreal mineral soils

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Geert Hensgens ◽  
Hjalmar Laudon ◽  
Mark S. Johnson ◽  
Martin Berggren
Keyword(s):  
Organic Carbon ◽  
Boreal Forest ◽  
Soil C ◽  
Earth Systems ◽  
Nuclear Bomb ◽  
C Cycle ◽  
Water Extractable Organic Carbon ◽  
High Lability ◽  
Mineral Soils ◽  
Terrestrial Biomes

AbstractThe boreal forest is among the largest terrestrial biomes on earth, storing more carbon (C) than the atmosphere. Due to rapid climatic warming and enhanced human development, the boreal region may have begun transitioning from a net C sink to a net source. This raises serious concern that old biogenic soil C can be re-introduced into the modern C cycle in near future. Combining bio-decay experiments, mixing models and the Keeling plot method, we discovered a distinct old pre-bomb organic carbon fraction with high biodegradation rate. In total, 34 ± 12% of water-extractable organic carbon (WEOC) in podzols, one of the dominating boreal soil types, consisted of aged (~ 1000 year) labile C. The omission of this aged (i.e., Δ14C depleted) WEOC fraction in earlier studies is due to the co-occurrence with Δ14C enriched modern C formed following 1950s nuclear bomb testing masking its existence. High lability of aged soil WEOC and masking effects of modern Δ14C enriched C suggests that the risk for mobilization and re-introduction of this ancient C pool into the modern C cycle has gone undetected. Our findings have important implications for earth systems models in terms of climate-carbon feedbacks and the future C balance of the boreal forest.

scholarly journals Three representative UK moorland soils show differences in decadal release of dissolved organic carbon in response to environmental change

2011 ◽  
Vol 8 (12) ◽  
pp. 3661-3675 ◽  
Author(s):  
M. I. Stutter ◽  
D. G. Lumsdon ◽  
A. P. Rowland
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Environmental Change ◽  
Soil Properties ◽  
Process Models ◽  
Environmental Drivers ◽  
Specific Response ◽  
Soil C ◽  
Doc Concentration ◽  
Mineral Soils

Abstract. Moorland carbon reserves in organo-mineral soils may be crucial to predicting landscape-scale variability in soil carbon losses, an important component of which is dissolved organic carbon (DOC). Surface water DOC trends are subject to a range of scaling, transport and biotic processes that disconnect them from signals in the catchment's soils. Long-term soil datasets are vital to identify changes in DOC release at source and soil C depletion. Here we show, that moorland soil solution DOC concentrations at three key UK Environmental Change Network sites increased between 1993–2007 in both surface- and sub- soil of a freely-draining Podzol (48 % and 215 % increases in O and Bs horizons, respectively), declined in a gleyed Podzol and showed no change in a Peat. Our principal findings were that: (1) considerable heterogeneity in DOC response appears to exist between different soils that is not apparent from the more consistent observed trends for streamwaters, and (2) freely-draining organo-mineral Podzol showed increasing DOC concentrations, countering the current scientific focus on soil C destabilization in peats. We discuss how the key solubility controls on DOC associated with coupled physico-chemical factors of ionic strength, acid deposition recovery, soil hydrology and temperature cannot readily be separated. Yet, despite evidence that all sites are recovering from acidification the soil-specific responses to environmental change have caused divergence in soil DOC concentration trends. The study shows that the properties of soils govern their specific response to an approximately common set of broad environmental drivers. Key soil properties are indicated to be drainage, sulphate and DOC sorption capacity. Soil properties need representation in process-models to understand and predict the role of soils in catchment to global C budgets. Catchment hydrological (i.e. transport) controls may, at present, be governing the more ubiquitous rises in river DOC concentration trends, but soil (i.e. source) controls provide the key to prediction of future C loss to waters and the atmosphere.

scholarly journals Three representative UK moorland soils show differences in decadal release of dissolved organic carbon in response to environmental change

2011 ◽  
Vol 8 (4) ◽  
pp. 7823-7857
Author(s):  
M. I. Stutter ◽  
D. G. Lumsdon ◽  
A. P. Rowland
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Environmental Change ◽  
Soil Properties ◽  
Process Models ◽  
Environmental Drivers ◽  
Specific Response ◽  
Soil C ◽  
Doc Concentration ◽  
Mineral Soils

Abstract. Moorland carbon reserves in organo-mineral soils may be crucial to predicting landscape-scale variability in soil carbon losses, an important component of which is dissolved organic carbon (DOC). Surface water DOC trends are subject to a range of scaling, transport and biotic processes that disconnect them from signals in the catchment's soils. Long-term soil datasets are vital to identify changes in DOC release at source and soil C depletion. Here we show, that moorland soil solution DOC concentrations at three key UK Environmental Change Network sites increased between 1993–2007 in both surface- and sub- soil of a freely-draining Podzol (48 % and 215 % increases in O and Bs horizons, respectively), declined in a gleyed Podzol and showed no change in a Peat. Our principal findings were that: (1) considerable heterogeneity in DOC response appears to exist between different soils that is not apparent from the more consistent observed trends for streamwaters, and (2) freely-draining organo-mineral Podzol showed increasing DOC concentrations, countering the current scientific focus on soil C destabilization in peats. We discuss how the key solubility controls on DOC associated with coupled physico-chemical factors of ionic strength, acid deposition recovery, soil hydrology and temperature cannot readily be separated. Yet, despite evidence that all sites are recovering from acidification the soil-specific responses to environmental change have caused divergence in soil DOC concentration trends. The study shows that the properties of soils govern their specific response to an approximately common set of broad environmental drivers. Key soil properties are indicated to be drainage, sulphate and DOC sorption capacity. Soil properties need representation in process-models to understand and predict the role of soils in catchment to global C budgets. Catchment hydrological (i.e. transport) controls may, at present, be governing the more ubiquitous rises in river DOC concentration trends, but soil (i.e. source) controls provide the key to prediction of future C loss to waters and the atmosphere.

scholarly journals The contribution of deadwood to soil carbon dynamics in contrasting temperate forest ecosystems

2021 ◽  
Author(s):  
V. L. Shannon ◽  
E. I. Vanguelova ◽  
J. I. L. Morison ◽  
L. J. Shaw ◽  
J. M. Clark
Keyword(s):  
Organic Carbon ◽  
Soil Carbon ◽  
Leaf Litter ◽  
Phenol Oxidase ◽  
Forest Carbon ◽  
Microbial Decomposition ◽  
High Background ◽  
Soil C ◽  
Tea Bag Index ◽  
Water Extractable Organic Carbon

AbstractDeadwood forms a significant carbon pool in forest systems and is a potential source of dissolved organic carbon (DOC) input to soil, yet little is known about how deadwood effects forest soil carbon cycling. Deadwood DOC inputs to soil may be retained through sorption or may prime microbial decomposition of existing organic matter to produce additional DOC. To determine impacts of deadwood on soil C cycling, we analysed surface soil from beneath deadwood or leaf litter only, along chronosequences of stands of lowland oak and upland Sitka spruce. The concentration and quality (by optical indices) of water-extracted soil DOC (water-extractable organic carbon; WEOC), in situ decomposition ‘tea bag index’ (TBI) parameters and enzymatic potential assays (β-D-cellubiosidase, β-glucosidase, β-xylosidase, leucine aminopeptidase, phosphatase, phenol oxidase) were determined. Presence of deadwood significantly (p < 0.05) increased WEOC concentration (~ 1.5 to ~ 1.75 times) in the mineral oak soil but had no effect on WEOC in spruce soils, potentially because spruce deadwood DOC inputs were masked by a high background of WEOC (1168 mg kg−1 soil) and/or were not retained through mineral sorption in the highly organic (~ 90% SOM) soil. TBI and enzyme evidence suggested that deadwood-derived DOC did not impact existing forest carbon pools via microbial priming, possibly due to the more humified/aromatic quality of DOC produced (humification index of 0.75 and 0.65 for deadwood and leaf litter WEOC, respectively). Forest carbon budgets, particularly those for mineral soils, may underestimate the quantity of DOC if derived from soil monitoring that does not include a deadwood component.

Characterization of Soil Organic Matter along an elevation gradient at Stelvio Pass (Italian Alps).

2020 ◽  
Author(s):  
Roberta Zangrando ◽  
Maria del Carmen Villoslada Hidalgo ◽  
Clara Turetta ◽  
Nicoletta Cannone ◽  
Francesco Malfasi ◽  
...  
Keyword(s):  
Climate Change ◽  
Organic Matter ◽  
Soil Organic Matter ◽  
Organic Carbon ◽  
Elevation Gradient ◽  
Total Carbon ◽  
Plant Component ◽  
Soil C ◽  
C Cycle ◽  
C Stocks

&lt;p&gt;Climate Change (CC) has evident impacts on the biotic and abiotic components of ecosystems.&lt;/p&gt;&lt;p&gt;Soil is the third largest reservoir of carbon, next to the lithosphere and the oceans, and stores approximately 1500 Gt in the top1 m depth. &amp;#160;Even small changes in soil C stocks could have a vast impact on atmospheric CO&lt;sub&gt;2 &lt;/sub&gt;concentration. Elevated surface temperature can substantially affect global C budgets and produce positive or negative feedbacks to climate change. Therefore, understanding the response of soil organic carbon (SOC) stocks to warming is of critical importance to evaluate the feedbacks between terrestrial C cycle and climate change.&lt;/p&gt;&lt;p&gt;In comparison to other ecosystems, the areas at high altitudes and latitudes are the most vulnerable. In permafrost areas of the Northern Hemisphere the CC has already determined an increase in greenhouse gas emissions, shrub vegetation and variation in the composition of microbial communities. While numerous studies have been performed in Arctic, much less numerous are available for high altitude areas. These areas are a quarter of the emerged lands &amp;#160;and have suffered strong impacts from the CC. Mountain permafrost makes up 14% of global permafrost, stores large quantities of organic carbon (SOC), and can release large quantities of CO&lt;sub&gt;2&lt;/sub&gt; due to climate change. However, permafrost contribution to the IPCC global budget has not yet been correctly quantified, in particular for ecosystems of prairie and shrubland, which alone could incorporate over 80Pg of C between soil and biomass. In the last decades, the plant component has undergone migration of species to higher altitudes, expansion of shrubs, variations in floristic composition and dominance, variations in area distribution. The expansion of the shrubs accelerates the regression of alpine meadows and snow valleys.&lt;/p&gt;&lt;p&gt;The sampling activities have been carried out in July and September, from September 2017 to July 2019 in an area near Stelvio Pass (2,758 m a.s.l.) (Italian Central-Eastern Alps) along an altitude gradient. &amp;#160;&amp;#160;Two sampling sites located at 2600 m a.s.l. and 2200 m a.s.l. in altitude, corresponding to about 3&amp;#176; C difference in the average annual air temperature were chosen. At the 2600 m site, warming experiments using open-top chambers (OTCs) to investigate how climate warming affects SOC were performed.&lt;/p&gt;&lt;p&gt;In order to characterize the SOM (Soil Organic Matter), Total carbon (TC), Organic carbon (OC), Total Nitrogen (TN) and Dissolved Organic Carbon (DOC) were determined in soils. TC and TN were determined in biomass. In both soils and biomass were analyzed to quantify the distribution of stable isotopes of C and N, &amp;#948;&lt;sup&gt;13&lt;/sup&gt;C and &amp;#948;&lt;sup&gt;15&lt;/sup&gt;N.&lt;/p&gt;

Storage and spatial patterns of organic carbon of soil profiles in Guangdong Province, China

Soil Research ◽  
2017 ◽  
Vol 55 (4) ◽  
pp. 401
Author(s):  
Huihua Zhang ◽  
Junjian Chen ◽  
Zhifeng Wu ◽  
Dingqiang Li ◽  
Li Zhu
Keyword(s):  
Land Use ◽  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Guangdong Province ◽  
Soil Horizon ◽  
Surrounding Water ◽  
Soil C ◽  
Cycle System ◽  
C Cycle ◽  
Storage Location

Regional soil organic carbon (SOC) investigations play an important role in building knowledge of the global soil C cycle system. The purpose of the present study was to estimate soil organic carbon (SOC) storage for different soil types and land uses in Guangdong Province, China. The results showed that the total SOC storage in the study area was 1.25 Pg, of which 0.41 Pg SOC was in A horizon soils (mean depth 17.0cm), 0.51 Pg SOC was in the B horizon (mean depth 29.5cm) and 0.33 Pg SOC was in the C horizon (mean depth 48.9cm). SOC storage in Ferrallisols was approximately 0.976 Pg for the total soil profile, accounting for 78.1% of total SOC storage. Forest soils were the main SOC pool by land use, accounting for approximately 80.3% of total SOC storage. Regardless of soil type and land use, subsoil was the primary SOC storage location in the study area. The SOC contents of the upper soil horizon were closely related to the SOC contents of the lower soil horizon, possibly suggesting that there is movement of SOC from the surface soil to lower horizons. Because of soil degradation and erosion, approximately 13.3 Tg SOC entered the surrounding water, accounting for 3.2% of the SOC storage of A horizon soils, and approximately 20.9 Tg SOC was redistributed in surface soils of the study area each year.

scholarly journals Modeling changes in organic carbon stocks for distinct soils in southeastern brazil after four eucalyptus rotations using the century model

2011 ◽  
Vol 35 (3) ◽  
pp. 833-847 ◽  
Author(s):  
Augusto Miguel Nascimento Lima ◽  
Ivo Ribeiro da Silva ◽  
Jose Luis Stape ◽  
Eduardo Sá Mendonça ◽  
Roberto Ferreira Novais ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Residue Management ◽  
Southeastern Brazil ◽  
Native Forest ◽  
Century Model ◽  
Soil C ◽  
Climate Conditions ◽  
C Cycle ◽  
C Stocks ◽  
The Impact

Soil organic matter (SOM) plays an important role in carbon (C) cycle and soil quality. Considering the complexity of factors that control SOM cycling and the long time it usually takes to observe changes in SOM stocks, modeling constitutes a very important tool to understand SOM cycling in forest soils. The following hypotheses were tested: (i) soil organic carbon (SOC) stocks would be higher after several rotations of eucalyptus than in low-productivity pastures; (ii) SOC values simulated by the Century model would describe the data better than the mean of observations. So, the aims of the current study were: (i) to evaluate the SOM dynamics using the Century model to simulate the changes of C stocks for two eucalyptus chronosequences in the Rio Doce Valley, Minas Gerais State, Brazil; and (ii) to compare the C stocks simulated by Century with the C stocks measured in soils of different Orders and regions of the Rio Doce Valley growing eucalyptus. In Belo Oriente (BO), short-rotation eucalyptus plantations had been cultivated for 4.0; 13.0, 22.0, 32.0 and 34.0 years, at a lower elevation and in a warmer climate, while in Virginópolis (VG), these time periods were 8.0, 19.0 and 33.0 years, at a higher elevation and in a milder climate. Soil samples were collected from the 0-20 cm layer to estimate C stocks. Results indicate that the C stocks simulated by the Century model decreased after 37 years of poorly managed pastures in areas previously covered by native forest in the regions of BO and VG. The substitution of poorly managed pastures by eucalyptus in the early 1970´s led to an average increase of C of 0.28 and 0.42 t ha-1 year-1 in BO and VG, respectively. The measured C stocks under eucalyptus in distinct soil Orders and independent regions with variable edapho-climate conditions were not far from the values estimated by the Century model (root mean square error - RMSE = 20.9; model efficiency - EF = 0.29) despite the opposite result obtained with the statistical procedure to test the identity of analytical methods. Only for lower soil C stocks, the model over-estimated the C stock in the 0-20 cm layer. Thus, the Century model is highly promising to detect changes in C stocks in distinct soil orders under eucalyptus, as well as to indicate the impact of harvest residue management on SOM in future rotations.

scholarly journals The soil carbon erosion paradox reconciled

2022 ◽  
Author(s):  
Kristof Van Oost ◽  
Jo Six
Keyword(s):  
Climate Change ◽  
Ecosystem Services ◽  
Organic Carbon ◽  
Spatial Scales ◽  
Recent Model ◽  
Agricultural Expansion ◽  
Soil C ◽  
C Cycle ◽  
Temporal And Spatial ◽  
Carbon Erosion

Abstract. The acceleration of erosion, transport and burial of soil organic carbon (C) in response to agricultural expansion represents a significant perturbation of the terrestrial C cycle. Recent model advances now enable improved representation of the relationships between sedimentary processes and C cycling and this has led to substantially revised assessments of changes in land C as a result of land cover and climate change. However, surprisingly a consensus on both the direction and magnitude of the erosion-induced land-atmosphere C exchange is still lacking. Here, we show that the apparent soil C erosion paradox, i.e., whether agricultural erosion results in a C sink or source, can be reconciled when comprehensively considering the range of temporal (from seconds to millennia) and spatial scales (from soil microaggregates to the Land Ocean Aquatic Continuum (LOAC)) at which erosional effects on the C cycle operate. Based on the currently available data (74 studies), we developed a framework that describes erosion-induced C sink and source terms across scales. Based on this framework, we conclude that erosion is a source for atmospheric CO2 when considering only small temporal and spatial scales, while both sinks and sources appear when multi-scaled approaches are used. We emphasize the need for erosion control for the benefits it brings for the delivery of ecosystem services, particularly in low-input systems, but our analysis clearly demonstrates that cross-scale approaches are essential to accurately represent erosion effects on the global C cycle.

scholarly journals SOC stabilization mechanisms and temperature sensitivity in old terraced soils

2021 ◽  
Author(s):  
Pengzhi Zhao ◽  
Daniel J. Fallu ◽  
Sara Cucchiaro ◽  
Paolo Tarolli ◽  
Clive Waddington ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Temperature Sensitivity ◽  
Land Surface ◽  
Temperature Sensitive ◽  
Organic C ◽  
Soil C ◽  
Fraction Composition ◽  
Soil Burial ◽  
C Cycle ◽  
Clear Shift

Abstract. Being the most common and widest spread man-made landform, terrace construction has resulted in an extensive perturbation of the land surface. Our mechanistic understanding of soil organic carbon (SOC) (de-) stabilization mechanisms and of the persistence of SOC stored in terraced soils, however, is far from complete. Here we explored the factors controlling SOC stability and temperature sensitivity (Q10) of abandoned prehistoric agricultural terrace soils in NE England, using soil fractionation and temperature sensitive incubation in combination with measurements of terrace soil burial age. Results showed that although buried terrace soils contained 1.7 times more unprotected SOC (i.e., coarse particulate organic carbon) than non-terraced soils at comparable soil depths, a significantly lower potential soil respiration was observed, relative to a control (non-terraced) profile. This suggests that burial of former topsoil due to terracing provided a mechanism for enhanced C stabilization. Furthermore, we observed a shift in SOC fraction composition from particulate organic C towards mineral protected C with increasing burial age. This clear shift to more processed recalcitrant SOC with soil burial age also contributes to SOC stability in terraced soils. Temperature sensitivity incubations revealed that the dominant controls on Q10 depend on the terrace soil burial age. At relatively younger ages of soil burial, the reduction of substrate availability due to SOC mineral protection with ageing attenuates the intrinsic Q10 of SOC decomposition. However, as terrace soil becomes older, SOC stocks in deep buried horizons are characterized by a higher temperature sensitivity, potentially resulting from the poor SOC quality (i.e., soil C : N ratio). In conclusion, terracing in our study site has stabilized SOC as a result of soil burial during terrace construction. The depth-age patterns of Q10 and SOC fraction composition of terraced soils observed in our study site differ from those seen in non-terraced soils and this has implications when assessing the effects of climate warming or terrace abandonment on the terrestrial C cycle.

scholarly journals TIME-INTEGRATED COLLECTION OF CO2 FOR 14C ANALYSIS FROM SOILS

Radiocarbon ◽  
2021 ◽  
pp. 1-17
Author(s):  
Shawn Pedron ◽  
X Xu ◽  
J C Walker ◽  
J C Ferguson ◽  
R G Jespersen ◽  
...  
Keyword(s):  
Soil Temperature ◽  
Molecular Sieve ◽  
Emission Sources ◽  
Soil C ◽  
Silicone Tubing ◽  
2Nd Generation ◽  
C Cycle ◽  
Uptake Rates ◽  
Two Generations ◽  
Cleaning Procedures

ABSTRACT We developed a passive sampler for time-integrated collection and radiocarbon (14C) analysis of soil respiration, a major flux in the global C cycle. It consists of a permanent access well that controls the CO2 uptake rate and an exchangeable molecular sieve CO2 trap. We tested how access well dimensions and environmental conditions affect collected CO2, and optimized cleaning procedures to minimize 14CO2 memory. We also deployed two generations of the sampler in Arctic tundra for up to two years, collecting CO2 over periods of 3 days–2 months, while monitoring soil temperature, volumetric water content, and CO2 concentration. The sampler collects CO2 at a rate proportional to the length of a silicone tubing inlet (7–26 µg CO2-C day-1·m Si-1). With constant sampler dimensions in the field, CO2 recovery is best explained by soil temperature. We retrieved 0.1–5.3 mg C from the 1st and 0.6–13 mg C from the 2nd generation samplers, equivalent to uptake rates of 2–215 (n=17) and 10–247 µg CO2-C day-1 (n=20), respectively. The method blank is 8 ± 6 µg C (mean ± sd, n=8), with a radiocarbon content (fraction modern) ranging from 0.5875–0.6013 (n=2). The sampler enables more continuous investigations of soil C emission sources and is suitable for Arctic environments.

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