scholarly journals Beneath the arctic greening: Will soils lose or gain carbon or perhaps a little of both?

2019 ◽  
Author(s):  
Jennifer W. Harden ◽  
Jonathan A. O'Donnell ◽  
Katherine A. Heckman ◽  
Benjamin N. Sulman ◽  
Charles D. Koven ◽  
...  
Keyword(s):  
Steady State ◽  
Forest Soil ◽  
The Arctic ◽  
Mean Annual Temperature ◽  
Spruce Forest ◽  
Organic C ◽  
Soil C ◽  
Community Land Model ◽  
C Stocks ◽  
And Shifts

Abstract. Ecosystem shifts related to climate change are anticipated for the next decades to centuries based on a number of conceptual and experimentally derived models of plant structure and function. Belowground, the potential responses of soil systems are less well known. We used geochemical steady state models, soil density fractionation, and soil radiocarbon data to constrain changes in soil carbon based on measurements from detrital (free light), aggregate-bound (occluded) and complexed or chemically bound (mineral associated) carbon pools and for bulk soil. We explored a space-for-time sequence of soils along a cold-to-warm climatic gradient from Alaskan Black Spruce forest soil with permafrost (Gelisols; 50 cm Mean Annual Temperature −1.5 ºC), Alaskan White Spruce forest soil lacking permafrost (Inceptisols; 50 cm MAT +3 ºC ), and Iowa Grassland soil lacking permafrost (Mollisols; 50 cm MAT +9 ºC) developed on similar geologic substrates (wind-blown loess deposits). These temperature ranges were also representative of temperatures at 50 cm soil depth from model output by the Community Land Model for the years 2014, 2100, and 2300 for Interior Alaska. Fitting an exponential equation to depth trends in soil C down to 2 m depths, we found that depth distributions of organic C were related mainly to depths of rooting and changes in bulk density. Using output from the geochemical steady state model, the direction and magnitude of the C loss or gain upon ecosystem shift was dictated by the C stocks of initial and final ecosystems. Radiocarbon measurements specific to each soil fraction (free light, occluded, and mineral associated) allowed us to constrain the timing of the potential loss or gain of C in each fraction driven by climatic shifts. Thawing from the Gelisol to Inceptisol in loess parent materials from present day to year 2100 resulted in small net gains to soil C, reflecting the net balance between loss of detrital and gain into occluded and mineral associated C. Greater warming and shifts from Inceptisol to Mollisol analogous to predicted warming from circa 2100 to 2300 resulted in net C losses from both occluded and mineral associated C, although small gains to the free light C fraction occurred throughout the depth profile. Gains to occluded and mineral associated C post- thaw likely reflect aggregate formation and physical protection of C as well as formation of organo-mineral compounds that accompany microbial processing. Greater warming and shifts from Inceptisol to Mollisol, which are analogous to predicted warming circa 2100 to 2300, resulted in net C losses from both occluded and mineral associated C resulting from enhanced decomposition, small gains to the free light C fraction occurred throughout the transition to Mollisol reflecting deeper rooting of the tallgrass prairie system.

scholarly journals Evaluation of terrestrial pan-Arctic carbon cycling using a data-assimilation system

2019 ◽  
Vol 10 (2) ◽  
pp. 233-255 ◽  
Author(s):  
Efrén López-Blanco ◽  
Jean-François Exbrayat ◽  
Magnus Lund ◽  
Torben R. Christensen ◽  
Mikkel P. Tamstorf ◽  
...  
Keyword(s):  
The Arctic ◽  
Soil Organic C ◽  
Area Index ◽  
Organic C ◽  
Soil C ◽  
Transit Times ◽  
C Cycle ◽  
C Stocks ◽  
Data Assimilation System ◽  
Assimilation System

Abstract. There is a significant knowledge gap in the current state of the terrestrial carbon (C) budget. Recent studies have highlighted a poor understanding particularly of C pool transit times and of whether productivity or biomass dominate these biases. The Arctic, accounting for approximately 50 % of the global soil organic C stocks, has an important role in the global C cycle. Here, we use the CARbon DAta MOdel (CARDAMOM) data-assimilation system to produce pan-Arctic terrestrial C cycle analyses for 2000–2015. This approach avoids using traditional plant functional type or steady-state assumptions. We integrate a range of data (soil organic C, leaf area index, biomass, and climate) to determine the most likely state of the high-latitude C cycle at a 1∘ × 1∘ resolution and also to provide general guidance about the controlling biases in transit times. On average, CARDAMOM estimates regional mean rates of photosynthesis of 565 g C m−2 yr−1 (90 % confidence interval between the 5th and 95th percentiles: 428, 741), autotrophic respiration of 270 g C m−2 yr−1 (182, 397) and heterotrophic respiration of 219 g C m−2 yr−1 (31, 1458), suggesting a pan-Arctic sink of −67 (−287, 1160) g Cm−2 yr−1, weaker in tundra and stronger in taiga. However, our confidence intervals remain large (and so the region could be a source of C), reflecting uncertainty assigned to the regional data products. We show a clear spatial and temporal agreement between CARDAMOM analyses and different sources of assimilated and independent data at both pan-Arctic and local scales but also identify consistent biases between CARDAMOM and validation data. The assimilation process requires clearer error quantification for leaf area index (LAI) and biomass products to resolve these biases. Mapping of vegetation C stocks and change over time and soil C ages linked to soil C stocks is required for better analytical constraint. Comparing CARDAMOM analyses to global vegetation models (GVMs) for the same period, we conclude that transit times of vegetation C are inconsistently simulated in GVMs due to a combination of uncertainties from productivity and biomass calculations. Our findings highlight that GVMs need to focus on constraining both current vegetation C stocks and net primary production to improve a process-based understanding of C cycle dynamics in the Arctic.

Soil organic carbon stocks and flows in New Zealand: System development, measurement and modelling

2005 ◽  
Vol 85 (Special Issue) ◽  
pp. 481-489 ◽  
Author(s):  
K. R. Tate ◽  
R. H. Wilde ◽  
D. J. Giltrap ◽  
W. T. Baisden ◽  
S. Saggar ◽  
...  
Keyword(s):  
Land Use ◽  
Steady State ◽  
New Zealand ◽  
Organic Carbon ◽  
Land Use Changes ◽  
Soil Organic C ◽  
Organic C ◽  
Soil C ◽  
C Stocks ◽  
Stocks And Flows

An IPCC-based Carbon Monitoring System (CMS) was developed to monitor soil organic C stocks and flows to assist New Zealand to achieve its CO2 emissions reduction target under the Kyoto Protocol. Geo-referenced soil C data from 1158 sites (0.3 m depth) were used to assign steady-state soil C stocks to various combinations of soil class, climate, and land use. Overall, CMS soil C stock estimates are consistent with detailed, stratified soil C measurements at specific sites and over larger regions. Soil C changes accompanying land-use changes were quantified using a national set of land-use effects (LUEs). These were derived using a General Linear Model to include the effects of numeric predictors (e.g., slope angle). Major uncertainties a rise from estimates of changes in the areas involved, the assumption that soil C is at steady state for all land-cover types, and lack of soil C data for some LUEs. Total national soil organic C stocks estimated using the LUEs for 0–0.1, 0.1–0.3, and 0.3–1 m depths were 1300 ± 20, 1590 ± 30, and 1750 ± 70 Tg, respectively. Most soil C is stored in grazing lands (1480 ± 60 Tg to 0.3 m depth), which appear to be at or near steady state; their conversion to exotic forests and shrubland contributed most to the predicted national soil C loss of 0.6 ± 0.2 Tg C yr-1 during 1990–2000. Predicted and measured soil C changes for the grazing-forestry conversion agreed closely. Other uncertainties in our current soil CMS include: spatially integrated annual changes in soil C for the major land-use changes, lack of soil C change estimates below 0.3 m, C losses from erosion, the contribution of agricultural management of organic soils, and a possible interaction between land use and our soil-climate classification. Our approach could be adapted for use by other countries with land-use-change issues that differ from those in the IPCC default methodology. Key words: Soil organic carbon, land-use change, stocks, flows, measurement, modelling, IPCC

Carbon stocks in Tasmanian soils

Soil Research ◽  
2012 ◽  
Vol 50 (2) ◽  
pp. 83 ◽  
Author(s):  
W. E. Cotching
Keyword(s):  
Management Practices ◽  
Agricultural Soils ◽  
C Sequestration ◽  
Mean Annual Temperature ◽  
Soil C ◽  
C Stocks ◽  
Initial Soil ◽  
If Current ◽  
Intensive Cropping ◽  
The Difference

Soil carbon (C) stocks were calculated for Tasmanian soil orders to 0.3 and 1.0 m depth from existing datasets. Tasmanian soils have C stocks of 49–117 Mg C/ha in the upper 0.3 m, with Ferrosols having the largest soil C stocks. Mean soil C stocks in agricultural soils were significantly lower under intensive cropping than under irrigated pasture. The range in soil C within soil orders indicates that it is critical to determine initial soil C stocks at individual sites and farms for C accounting and trading purposes, because the initial soil C content will determine if current or changed management practices are likely to result in soil C sequestration or emission. The distribution of C within the profile was significantly different between agricultural and forested land, with agricultural soils having two-thirds of their soil C in the upper 0.3 m, compared with half for forested soils. The difference in this proportion between agricultural and forested land was largest in Dermosols (0.72 v. 0.47). The total amount of soil C in a soil to 1.0 m depth may not change with a change in land use, but the distribution can and any change in soil C deeper in the profile might affect how soil C can be managed for sequestration. Tasmanian soil C stocks are significantly greater than those in mainland states of Australia, reflecting the lower mean annual temperature and higher precipitation in Tasmania, which result in less oxidation of soil organic matter.

scholarly journals Effect of deforestation and subsequent land-use management on soil carbon stocks in the South American Chaco

2018 ◽  
Author(s):  
Natalia Andrea Osinaga ◽  
Carina Rosa Álvarez ◽  
Miguel Angel Taboada
Keyword(s):  
Land Use ◽  
Land Use Changes ◽  
Warm Season ◽  
Native Forest ◽  
Continuous Cropping ◽  
Organic C ◽  
Soil C ◽  
C Stocks ◽  
Chaco Region ◽  
The Impact

Abstract. Abstract. The sub-humid Chaco region of Argentina, originally covered by dry sclerophyll forest, has been subjected to clearing since the end of the '70 and replacement of the forest by no till farming. Land use changes produced a decrease in aboveground carbon stored in forests, but little is known about the impact on soil organic C stocks. The aim of this study was to evaluate soil C stocks and C fractions up to 1 m depth in soils under different land use:  20 yr continuous cropping, warm season grass pasture and native forest in 32 sites distributed over the Chaco region. The organic C stock content up to 1 m depth expressed as equivalent mass varied as follows: forest (119.3 Mg ha−1) > pasture (87.9 Mg ha−1) > continuous cropping (71.9 and 77.3 Mg ha−1), with no impact of the number of years under cropping. The most sensitive organic carbon fraction was the coarse particle fraction (2000 μm–212 μm) at 0–5 cm and 5–20 cm depth layers. Resistant carbon (

Site-level simulations of measurable soil fractions with Millennial Version 2

2021 ◽  
Author(s):  
Rose Abramoff ◽  
Bertrand Guenet ◽  
Haicheng Zhang ◽  
Katerina Georgiou ◽  
Xiaofeng Xu ◽  
...  
Keyword(s):  
Meta Analysis ◽  
C Sequestration ◽  
Current Understanding ◽  
Century Model ◽  
Mineral Association ◽  
Microbial Decomposition ◽  
Organic C ◽  
Soil C ◽  
Soil Fractions ◽  
C Stocks

<p>Soil carbon (C) models are used to predict C sequestration responses to climate and land use change. Yet, the soil models embedded in Earth system models typically do not represent processes that reflect our current understanding of soil C cycling, such as microbial decomposition, mineral association, and aggregation. Rather, they rely on conceptual pools with turnover times that are fit to bulk C stocks and/or fluxes. As measurements of soil fractions become increasingly available, soil C models that represent these measurable quantities can be evaluated more accurately. Here we present Version 2 (V2) of the Millennial model, a soil model developed to simulate C pools that can be measured by extraction or fractionation, including particulate organic C, mineral-associated organic C, aggregate C, microbial biomass, and dissolved organic C. Model processes have been updated to reflect the current understanding of mineral-association, temperature sensitivity and reaction kinetics, and different model structures were tested within an open-source framework. We evaluated the ability of Millennial V2 to simulate total soil organic C (SOC), as well as the mineral-associated and particulate fractions, using three soil fractionation data sets spanning a range of climate and geochemistry in Australia (N=495), Europe (N=176), and across the globe (N=730). Millennial V2 (RMSE = 1.98 – 4.76 kg, AIC = 597 – 1755) generally predicts SOC content better than the widely-used Century model (RMSE = 2.23 – 4.8 kg, AIC = 584 – 2271), despite an increase in process complexity and number of parameters. Millennial V2 reproduces between-site variation in SOC across a gradient of plant productivity, and predicts SOC turnover times similar to those of a global meta-analysis. Millennial V2 updates the conceptual Century model pools and processes and represents our current understanding of the roles that microbial activity, mineral association and aggregation play in soil C sequestration.</p>

Land‐use change with pasture and short rotation eucalypts impacts the soil C emissions and organic C stocks in the Cerrado biome

2020 ◽  
Vol 31 (7) ◽  
pp. 909-923 ◽  
Author(s):  
Rafael da Silva Teixeira ◽  
Ricardo Cardoso Fialho ◽  
Daniela Cristina Costa ◽  
Rodrigo Nogueira Sousa ◽  
Rafael Silva Santos ◽  
...  
Keyword(s):  
Land Use ◽  
Land Use Change ◽  
Organic C ◽  
Soil C ◽  
Cerrado Biome ◽  
Short Rotation ◽  
C Stocks

scholarly journals Spatial patterns in soil organic matter dynamics are shaped by mycorrhizosphere interactions in a treeline forest

2019 ◽  
Vol 447 (1-2) ◽  
pp. 521-535
Author(s):  
Nina L. Friggens ◽  
Thomas J. Aspray ◽  
Thomas C. Parker ◽  
Jens-Arne Subke ◽  
Philip A. Wookey
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Spatial Scales ◽  
Mountain Birch ◽  
Organic C ◽  
Soil C ◽  
Soil Organic Matter Dynamics ◽  
C Stocks ◽  
Organic Matter Dynamics ◽  
Individual Trees

Abstract Aims In the Swedish sub-Arctic, mountain birch (Betula pubescens ssp. czerepanovii) forests mediate rapid soil C cycling relative to adjacent tundra heaths, but little is known about the role of individual trees within forests. Here we investigate the spatial extent over which trees influence soil processes. Methods We measured respiration, soil C stocks, root and mycorrhizal productivity and fungi:bacteria ratios at fine spatial scales along 3 m transects extending radially from mountain birch trees in a sub-Arctic ecotone forest. Root and mycorrhizal productivity was quantified using in-growth techniques and fungi:bacteria ratios were determined by qPCR. Results Neither respiration, nor root and mycorrhizal production, varied along transects. Fungi:bacteria ratios, soil organic C stocks and standing litter declined with increasing distance from trees. Conclusions As 3 m is half the average size of forest gaps, these findings suggest that forest soil environments are efficiently explored by roots and associated mycorrhizal networks of B. pubescens. Individual trees exert influence substantially away from their base, creating more uniform distributions of root, mycorrhizal and bacterial activity than expected. However, overall rates of soil C accumulation do vary with distance from trees, with potential implications for spatio-temporal soil organic matter dynamics and net ecosystem C sequestration.

Spatial variability in terrestrial and aquatic carbon stocks and fluxes in boreal forested catchments

2020 ◽  
Author(s):  
Nora Casson ◽  
Adrienne Ducharme ◽  
Geethani Amarawansha ◽  
Geoff Gunn ◽  
Scott Higgins ◽  
...  
Keyword(s):  
Spatial Variability ◽  
Soil Depth ◽  
Organic C ◽  
Soil C ◽  
C Pools ◽  
Sampling Campaign ◽  
C Stocks ◽  
Doc Export ◽  
Rain Events ◽  
C Pools And Fluxes

<p>Canada’s boreal zone is a complex mosaic of forests, wetlands, streams and lakes.  The pool of carbon (C) stored in each of these ecosystem components is vast, and significant to the global C balance.  However, C pools and fluxes are heterogeneous in time and space, which contributes to uncertainty in predicting how a changing climate will affect the fate of C in these sensitive ecosystems. The objective of this study was to investigate factors controlling spatial variability in soil C stocks and stream C export and assess the sensitivity of these stocks and fluxes to climatic factors. We conducted a detailed examination of soil C stocks and stream dissolved organic C (DOC) export from a 320 ha boreal forested catchment located in northwestern Ontario, Canada. High-frequency stream chemistry and discharge samples were collected from three inflow streams during snowmelt and rain events from 2016-2017. An intensive soil C sampling campaign resulting in 47 surface (0 – 30 cm) samples were collected during the summer of 2019. Stream hysteresis analysis revealed marked differences in flowpaths among sub-catchments during snowmelt and rain events. In the wetland-dominated catchment, near-stream sources contributed most of the DOC export during both rainstorms and snowmelt events, but in upland-dominated catchments, the sources of DOC depended on antecedent moisture conditions. Rainstorms in these catchments following prolonged droughts resulted in DOC flushing from distal regions of the catchment. Soil C stocks were also highly spatially variable, with much of the variability being explained by local-scale factors (e.g. gravel content, soil depth, distance to the nearest ridge). Taken together, these two findings emphasize the need to consider sub-catchment scale variability when calculating C pools and fluxes in boreal catchments. This is also important when predicting how C dynamics will shift in the future as a result of shorter winters, longer droughts and more intense rainstorms.</p>

scholarly journals Detecting the permafrost carbon feedback: Talik formation and increased cold-season respiration as precursors to sink-to-source transitions

2017 ◽  
Author(s):  
Nicholas C. Parazoo ◽  
Charles D. Koven ◽  
David M. Lawrence ◽  
Vladimir Romanovsky ◽  
Charles E. Miller
Keyword(s):  
Cold Season ◽  
Permafrost Region ◽  
Permafrost Degradation ◽  
Borehole Data ◽  
Deep Soil ◽  
Organic C ◽  
Soil C ◽  
Community Land Model ◽  
Warm Permafrost

Abstract. Thaw and release of permafrost carbon (C) due to climate change is likely to offset increased vegetation C uptake in Northern High Latitude (NHL) terrestrial ecosystems. Models project that this permafrost C feedback may act as a slow leak, in which case detection and attribution of the feedback may be difficult. The formation of talik, a sub-surface layer of perennially thawed soil, can accelerate permafrost degradation and soil respiration, ultimately shifting the C balance of permafrost affected ecosystems from long-term C sinks to long-term C sources. It is imperative to understand and characterize mechanistic links between talik, permafrost thaw, and respiration of deep soil C to detect and quantify the permafrost C feedback. Here, we use the Community Land Model (CLM) version 4.5, a permafrost and biogeochemistry model, in comparison to long term deep borehole data along North American and Siberian transects, to investigate thaw driven C sources in NHL (> 55° N) from 2000–2300. Widespread talik at depth IS projected across most of the NHL permafrost region (14 million km2) by 2300, correlated to increased cold season warming, earlier spring thaw, and growing active layers. Talik formation peaks in the 2050s in warm permafrost regions in the sub-Arctic. Comparison to borehole data suggests talik formation may even occur sooner. Accelerated decomposition of deep soil C following talik onset shifts the surface balance of photosynthetic uptake and litter respiration into long-term C sources across 3.2 million km2 of permafrost. Talik driven sources occur predominantly in warm permafrost, but sink-to-source transition dates are delayed by decades to centuries due to high ecosystem productivity. In contrast, most of the cold permafrost region in the northern Arctic (3 million km2) shifts to a net source by the end of the 21st century in the absence of talik due to the high decomposition rates of shallow, young C in organic rich soils coupled with low productivity. Our results provide important clues signaling imminent talik onset and C source transition including: (1) late cold season (Jan–Feb) soil warming at depth (~ 2 m), (2) increasing cold season emissions (Nov–Apr), (3) enhanced respiration of deep, old C in warm permafrost and young, shallow C in organic rich cold permafrost soils. Our results suggest a mosaic of processes that govern carbon source-to-sink transitions at high latitudes, and emphasize the urgency of monitoring soil thermal profiles, organic C age and content, cold season CO2 emissions, and atmospheric 14CO2 as key indicators of the permafrost C feedback.

scholarly journals Assessing the response of soil carbon in Australia to changing inputs and climate using a consistent modelling framework

2021 ◽  
Vol 18 (18) ◽  
pp. 5185-5202
Author(s):  
Juhwan Lee ◽  
Raphael A. Viscarra Rossel ◽  
Mingxi Zhang ◽  
Zhongkui Luo ◽  
Ying-Ping Wang
Keyword(s):  
Global Change ◽  
Future Climate Change ◽  
Natural Environments ◽  
Soil Organic C ◽  
Total N ◽  
Organic C ◽  
Soil C ◽  
Continental Scale ◽  
Modelling Framework ◽  
C Stocks

Abstract. Land use and management practices affect the response of soil organic carbon (C) to global change. Process-based models of soil C are useful tools to simulate C dynamics, but it is important to bridge any disconnect that exists between the data used to inform the models and the processes that they depict. To minimise that disconnect, we developed a consistent modelling framework that integrates new spatially explicit soil measurements and data with the Rothamsted carbon model (Roth C) and simulates the response of soil organic C to future climate change across Australia. We compiled publicly available continental-scale datasets and pre-processed, standardised and configured them to the required spatial and temporal resolutions. We then calibrated Roth C and ran simulations to estimate the baseline soil organic C stocks and composition in the 0–0.3 m layer at 4043 sites in cropping, modified grazing, native grazing and natural environments across Australia. We used data on the C fractions, the particulate, mineral-associated and resistant organic C (POC, MAOC and ROC, respectively) to represent the three main C pools in the Roth C model's structure. The model explained 97 %–98 % of the variation in measured total organic C in soils under cropping and grazing and 65 % in soils under natural environments. We optimised the model at each site and experimented with different amounts of C inputs to simulate the potential for C accumulation under constant climate in a 100-year simulation. With an annual increase of 1 Mg C ha−1 in C inputs, the model simulated a potential soil C increase of 13.58 (interquartile range 12.19–15.80), 14.21 (12.38–16.03) and 15.57 (12.07–17.82) Mg C ha−1 under cropping, modified grazing and native grazing and 3.52 (3.15–4.09) Mg C ha−1 under natural environments. With projected future changes in climate (+1.5, 2 and 5.0 ∘C) over 100 years, the simulations showed that soils under natural environments lost the most C, between 3.1 and 4.5 Mg C ha−1, while soils under native grazing lost the least, between 0.4 and 0.7 Mg C ha−1. Soil under cropping lost between 1 and 2.7 Mg C ha−1, while those under modified grazing showed a slight increase with temperature increases of 1.5 ∘C, but with further increases of 2 and 5 ∘C the median loss of TOC was 0.28 and 3.4 Mg C ha−1, respectively. For the different land uses, the changes in the C fractions varied with changes in climate. An empirical assessment of the controls on the C change showed that climate, pH, total N, the C : N ratio and cropping were the most important controls on POC change. Clay content and climate were dominant controls on MAOC change. Consistent and explicit soil organic C simulations improve confidence in the model's estimations, facilitating the development of sustainable soil management under global change.

Sign in / Sign up

Export Citation Format

Share Document