scholarly journals Field-warmed soil carbon changes imply high 21st century modeled uncertainty

2018 ◽  
Author(s):  
Katherine Todd-Brown ◽  
Bin Zheng ◽  
Thomas Crowther
Keyword(s):  
Organic Carbon ◽  
Soil Carbon ◽  
21St Century ◽  
Temperature Sensitivity ◽  
Carbon Stock ◽  
Earth System Model ◽  
System Model ◽  
Earth System ◽  
Soil Carbon Stock ◽  
Q10 Values

Abstract. The feedback between planetary warming and soil carbon loss has been the focus of considerable scientific attention in recent decades, due to its potential to accelerate anthropogenic climate change. The soil carbon temperature sensitivity is traditionally estimated from short-term respiration measurements – either from laboratory incubations that are artificially manipulated, or field measurements that cannot distinguish between plant and microbial respiration. To address these limitations of previous approaches, we developed a new method to estimate temperature sensitivity (Q10) of soil carbon directly from warming-induced changes in soil carbon stocks measured in 36 field experiments across the world. Variations in warming magnitude and control organic carbon percentage explained much of field-warmed organic carbon percentage (R2 = 0.96), revealing Q10 across sites of 2.2, [1.6, 2.7] 95 % Confidence Interval (CI). When these field-derived Q10 values were extrapolated over the 21st century using a post-hoc correction of 20 CMIP5 Earth system model outputs, the multi-model mean soil carbon stock changes shifted from the previous value of 83 ± 156 Pg-carbon (weighted mean ± 1 SD), to 16 ± 156 Pg-carbon with a Q10 driven 95 % CI of 245 ± 194 to −99 ± 208 Pg-carbon. On average, incorporating the field-derived Q10 values into Earth system model simulations led to reductions in the projected amount of carbon sequestered in the soil over the 21st century. However, the considerable parameter uncertainty led to extremely high variability in soil carbon stock projections within each model; intra-model uncertainty driven by the measured Q10 was as great as that between model variation. This study demonstrates that data integration may not improve model certainty, but instead should strive to capture the variation of the system as well as mean trends.

scholarly journals Field-warmed soil carbon changes imply high 21st-century modeling uncertainty

2018 ◽  
Vol 15 (12) ◽  
pp. 3659-3671 ◽  
Author(s):  
Katherine Todd-Brown ◽  
Bin Zheng ◽  
Thomas W. Crowther
Keyword(s):  
Organic Carbon ◽  
Soil Carbon ◽  
21St Century ◽  
Temperature Sensitivity ◽  
Carbon Stock ◽  
Earth System Model ◽  
System Model ◽  
Earth System ◽  
Soil Carbon Stock ◽  
Q10 Values

Abstract. The feedback between planetary warming and soil carbon loss has been the focus of considerable scientific attention in recent decades, due to its potential to accelerate anthropogenic climate change. The soil carbon temperature sensitivity is traditionally estimated from short-term respiration measurements – either from laboratory incubations that are artificially manipulated or from field measurements that cannot distinguish between plant and microbial respiration. To address these limitations of previous approaches, we developed a new method to estimate soil temperature sensitivity (Q10) of soil carbon directly from warming-induced changes in soil carbon stocks measured in 36 field experiments across the world. Variations in warming magnitude and control organic carbon percentage explained much of field-warmed organic carbon percentage (R2 = 0.96), revealing Q10 across sites of 2.2 [1.6, 2.7] 95 % confidence interval (CI). When these field-derived Q10 values were extrapolated over the 21st century using a post hoc correction of 20 Coupled Model Intercomparison Project Phase 5 (CMIP5) Earth system model outputs, the multi-model mean soil carbon stock changes shifted from the previous value of 88 ± 153 Pg carbon (weighted mean ± 1 SD) to 19 ± 155 Pg carbon with a Q10-driven 95 % CI of 248 ± 191 to −95 ± 209 Pg carbon. On average, incorporating the field-derived Q10 values into Earth system model simulations led to reductions in the projected amount of carbon sequestered in the soil over the 21st century. However, the considerable parameter uncertainty led to extremely high variability in soil carbon stock projections within each model; intra-model uncertainty driven by the field-derived Q10 was as great as that between model variation. This study demonstrates that data integration should capture the variation of the system, as well as mean trends.

Sensitivity of organic carbon fluxes from Arctic coastal erosion to climate change

2021 ◽  
Author(s):  
David Marcolino Nielsen ◽  
Patrick Pieper ◽  
Victor Brovkin ◽  
Paul Overduin ◽  
Tatiana Ilyina ◽  
...  
Keyword(s):  
Climate Change ◽  
Organic Carbon ◽  
Sea Ice ◽  
Coastal Erosion ◽  
Earth System Model ◽  
System Model ◽  
The Arctic ◽  
Earth System ◽  
Carbon Release ◽  
Arctic Coast

<p>When unprotected by sea-ice and exposed to the warm air and ocean waves, the Arctic coast erodes and releases organic carbon from permafrost to the surrounding ocean and atmosphere. This release is estimated to deliver similar amounts of organic carbon to the Arctic Ocean as all Arctic rivers combined, at the present-day climate. Depending on the degradation pathway of the eroded material, the erosion of the Arctic coast could represent a positive feedback loop in the climate system, to an extent still unknown. In addition, the organic carbon flux from Arctic coastal erosion is expected to increase in the future, mainly due to surface warming and sea-ice loss. In this work, we aim at addressing the following questions: How is Arctic coastal erosion projected to change in the future? How sensitive is Arctic coastal erosion to climate change?</p><p>To address these questions, we use a 10-member ensemble of climate change simulations performed with the Max Planck Institute Earth System Model (MPI-ESM) for the Coupled Model Intercomparison Project phase 6 (CMIP6) to make projections of coastal erosion at a pan-Arctic scale. We use a semi-empirical approach to model Arctic coastal erosion, assuming a linear contribution of its thermal and mechanical drivers. The pan-Arctic carbon release due to coastal erosion is projected to increase from 6.9 ± 5.4 TgC/year (mean estimate ± two standard deviations from the distribution of uncertainties) during the historical period (mean over 1850 -1950) to between 13.1 ± 6.7 TgC/year and 17.2 ± 8.2 TgC/year in the period 2081-2100 following an intermediate (SSP2.4-5) and a high-end (SSP5.8-5) climate change scenario, respectively. The sensitivity of the organic carbon release from Arctic coastal erosion to climate warming is estimated to range from 1.52 TgC/year/K to 2.79 TgC/year/K depending on the scenario. Our results present the first projections of Arctic coastal erosion, combining observations and Earth system model (ESM) simulations. This allows us to make first-order estimates of sensitivity and feedback magnitudes between Arctic coastal erosion and climate change, which can lay out pathways for future coupled ESM simulations.</p><p> </p>

scholarly journals Climate and land use change impacts on global terrestrial ecosystems and river flows in the HadGEM2-ES Earth system model using the representative concentration pathways

2015 ◽  
Vol 12 (5) ◽  
pp. 1317-1338 ◽  
Author(s):  
R. A. Betts ◽  
N. Golding ◽  
P. Gonzalez ◽  
J. Gornall ◽  
R. Kahana ◽  
...  
Keyword(s):  
Climate Change ◽  
Global Warming ◽  
Land Cover ◽  
Land Cover Change ◽  
21St Century ◽  
Terrestrial Ecosystems ◽  
Earth System Model ◽  
System Model ◽  
Earth System ◽  
Impacts Of Climate Change

Abstract. A new generation of an Earth system model now includes a number of land-surface processes directly relevant to analyzing potential impacts of climate change. This model, HadGEM2-ES, allows us to assess the impacts of climate change, multiple interactions, and feedbacks as the model is run. This paper discusses the results of century-scale HadGEM2-ES simulations from an impacts perspective – specifically, terrestrial ecosystems and water resources – for four different scenarios following the representative concentration pathways (RCPs), used in the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC, 2013, 2014). Over the 21st century, simulated changes in global and continental-scale terrestrial ecosystems due to climate change appear to be very similar in all 4 RCPs, even though the level of global warming by the end of the 21st century ranges from 2 °C in the lowest scenario to 5.5° in the highest. A warming climate generally favours broadleaf trees over needleleaf, needleleaf trees over shrubs, and shrubs over herbaceous vegetation, resulting in a poleward shift of temperate and boreal forests and woody tundra in all scenarios. Although climate related changes are slightly larger in scenarios of greater warming, the largest differences between scenarios arise at regional scales as a consequence of different patterns of anthropogenic land cover change. In the model, the scenario with the lowest global warming results in the most extensive decline in tropical forest cover due to a large expansion of agriculture. Under all four RCPs, fire potential could increase across extensive land areas, particularly tropical and sub-tropical latitudes. River outflows are simulated to increase with higher levels of CO2 and global warming in all projections, with outflow increasing with mean temperature at the end of the 21st century at the global scale and in North America, Asia, and Africa. In South America, Europe, and Australia, the relationship with climate warming and CO2 rise is less clear, probably as a result of land cover change exerting a dominant effect in those regions.

scholarly journals A simplified permafrost-carbon model for long-term climate studies with the CLIMBER-2 coupled earth system model

2014 ◽  
Vol 7 (4) ◽  
pp. 4931-4992
Author(s):  
K. A. Crichton ◽  
D. M. Roche ◽  
G. Krinner ◽  
J. Chappellaz
Keyword(s):  
Soil Carbon ◽  
Land Surface ◽  
Measurement Data ◽  
Grid Cell ◽  
Earth System Model ◽  
Carbon Pool ◽  
System Model ◽  
Earth System ◽  
Carbon Release ◽  
Surface Scheme

Abstract. We present the development and validation of a simplified permafrost-carbon mechanism for use with the land surface scheme operating in the CLIMBER-2 earth system model. The simplified model estimates the permafrost fraction of each grid cell according to the balance between modelled cold (below 0 °C) and warm (above 0 °C) days in a year. Areas diagnosed as permafrost are assigned a reduction in soil decay, thus creating a slow accumulating soil carbon pool. In warming climates, permafrost extent reduces and soil decay increases, resulting in soil carbon release to the atmosphere. Four accumulation/decay rate settings are retained for experiments within the CLIMBER-2(P) model, which are tuned to agree with estimates of total land carbon stocks today and at the last glacial maximum. The distribution of this permafrost-carbon pool is in broad agreement with measurement data for soil carbon concentration per climate condition. The level of complexity of the permafrost-carbon model is comparable to other components in the CLIMBER-2 earth system model.

scholarly journals A simplified permafrost-carbon model for long-term climate studies with the CLIMBER-2 coupled earth system model

2014 ◽  
Vol 7 (6) ◽  
pp. 3111-3134 ◽  
Author(s):  
K. A. Crichton ◽  
D. M. Roche ◽  
G. Krinner ◽  
J. Chappellaz
Keyword(s):  
Soil Carbon ◽  
Decomposition Rate ◽  
Land Surface ◽  
Measurement Data ◽  
Grid Cell ◽  
Earth System Model ◽  
Carbon Pool ◽  
System Model ◽  
Earth System ◽  
Soil Carbon Content

Abstract. We present the development and validation of a simplified permafrost-carbon mechanism for use with the land surface scheme operating in the CLIMBER-2 earth system model. The simplified model estimates the permafrost fraction of each grid cell according to the balance between modelled cold (below 0 °C) and warm (above 0 °C) days in a year. Areas diagnosed as permafrost are assigned a reduction in soil decomposition rate, thus creating a slow accumulating soil carbon pool. In warming climates, permafrost extent reduces and soil decomposition rates increase, resulting in soil carbon release to the atmosphere. Four accumulation/decomposition rate settings are retained for experiments within the CLIMBER-2(P) model, which are tuned to agree with estimates of total land carbon stocks today and at the last glacial maximum. The distribution of this permafrost-carbon pool is in broad agreement with measurement data for soil carbon content. The level of complexity of the permafrost-carbon model is comparable to other components in the CLIMBER-2 earth system model.

scholarly journals SPATIAL VARIABILITY OF PHYSICAL ATTRIBUTES, LITTER AND SOIL CARBON STOCK IN A FAMILY FARMING SYSTEM IN TOCANTINS

2020 ◽  
Vol 28 ◽  
pp. 37-50
Author(s):  
Wilma Dias Santana ◽  
Antônio Clementino dos Santos ◽  
Amanda Da Silva Reis ◽  
Rodrigo De Castro Tavares ◽  
Gilson Araújo de Freitas
Keyword(s):  
Land Use ◽  
Organic Carbon ◽  
Spatial Variability ◽  
Soil Carbon ◽  
Carbon Stock ◽  
Farming System ◽  
Native Forest ◽  
Family Farming ◽  
Soil Carbon Stock ◽  
Physical Attributes

The monitoring of soil attributes allows the evaluation of its ability to perform its functions within an agroecosystem. The objective of this work was to evaluate the spatial variability of soil physical attributes, litter and carbon stock in a family farming system in the Cerrado Tocantinense. The area is located in the southern region in the state in the municipality of Aliança do Tocantins. Four types of land use were diagnosed in the area: brachiaria pasture intercropped with stylosanthes, Andropogon pasture, orchard and native forest. The native forest was considered as a reference. The study area totaled 7.9 ha-1 in which it was distributed an irregular sample grid composed of 160 points. Deformed and undeformed samples were collected for each georeferenced point at depths of 0-10 and 10-20 cm, as well as samples to determine the litter and soil carbon stock. Data were submitted to exploratory analysis and geostatistical study. It was found that the conversion of native forest for different soil uses through orchard, brachiaria, andropogon and native forest caused spatial variability in physical attributes, litter and soil carbon stock at depths 0-10 and 10-20 cm. The orchard subarea stood out as a promising system in the accumulation of organic carbon due to cattle manure.

Estimation of Biomass and Soil Carbon Stock in Mixed Forest of Abies pindrow Royle - Picea smithiana (Wallich) Boiss. and Betula utilis D.Don Forests of District Shimla, Himachal Pradesh

2017 ◽  
Vol 40 (2) ◽  
pp. 117-120
Author(s):  
R.K. Verma ◽  
◽  
K.S. Kapoor ◽  
Keyword(s):  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Soil Carbon ◽  
Carbon Stock ◽  
Soil Organic Carbon Stock ◽  
Soil Carbon Stock ◽  
Betula Utilis ◽  
Below Ground ◽  
Abies Pindrow ◽  
Organic Carbon Stock

A study was conducted to estimate the biomass and soil carbon stock in various sites of Abies pindrow (Silver fir) - Picea smithiana (Spruce) and Betula utilis (Bhojpatra) forests of district Shimla, Himachal Pradesh during the year 2014-2015. In Fir-Spruce mixed forests, the amount of carbon stock at Larot site for above ground, below ground, under storey and litter was 287.39 tC/ha, 57.48 tC/ha, 2.22 tC/ha and 0.92 tC/ha respectively. Whereas, values of these components at Khirki site were 267.31 tC/ha, 53.46 tC/ha, 3.65 tC/ha and 0.85 tC/ha respectively. The biomass as well as the carbon stock was higher at Larot site than Khirki site. The soil organic carbon stock (tC/ha) at 10-15 cm, 15-30 cm and 30-45 cm was 27.05, 24.91 and 18.35 respectively at Larot site. Whereas, these values for different depths were 27.36 tC/ha, 22.02 tC/ha and 19.01 tC/ha respectively for Khirki site. The value of total soil carbon stock was little more (70.31 tC/ha) at Larot site than Khirki site (68.39 tC/ha). In case of Bhojpatra forests, the amount of carbon stock at Larot site for above ground, below ground, under storey and litter was 75.32 tC/ha, 18.83 tC/ha, 11.38 tC/ha and 1.57 tC/ha respectively. In Bhojpatra forests, understorey i.e. biomass of shrubs and herbs contribute about 11.63% to the total biomass in the forest. The soil organic carbon stock (tC/ha) at 10-15 cm, 15-30 cm and 30-45 cm was 19.54, 15.43 and 11.88 respectively for this site. The soil organic carbon stock decreased with increasing the soil depth.

scholarly journals Fine root contribution to the soil carbon stock of an agroforestry system in a Caatinga-Atlantic Forest transition zone

2020 ◽  
Vol 56 (1) ◽  
pp. 128-136
Author(s):  
Paulo Henrique Marques Monroe ◽  
Patrícia Anjos Bittencourt Barreto-Garcia ◽  
Maida Cynthia Duca Lima ◽  
Rayka Kristian Alves Santos ◽  
Elismar Pereira Oliveira ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Soil Carbon ◽  
Fine Roots ◽  
Carbon Stock ◽  
Agroforestry System ◽  
Soil Organic Carbon Stock ◽  
Soil Carbon Stock ◽  
Root Carbon ◽  
Organic Carbon Stock

The objective of this work was to evaluate the distribution of fine roots and its influence on the soil organic carbon stock, at a depth of 20 cm, in a Grevillea robusta and Coffea arabica agroforestry system. The study was conducted in an agroforestry system established 15 years ago in a transition area of Caatinga and Atlantic Forest biomes in Brazil. G. robusta trees representing the most frequent diameter class were selected, and three distances of these trees (0, 0.75 and 1.50 m) and two soil collection depths (0–10 and 10–20 cm) were defined. The root samples were scanned and quantified using a software program. There was a general predominance of roots with a diameter of 0.6 mm at the shortest distance from the surface layer, while there was a predominance of roots with a diameter of 0.4 mm in the 10–20 cm layer. The root carbon stock at a distance of 0.75 m was higher at a depth of 0–10 cm (0.60 Mg ha-1). The soil organic carbon stock also showed higher results in the 0–10 cm layer compared to the 10–20 cm layer, although with significant variation only in the distance of 1.5 m. There was a higher concentration of fine roots in the topsoil, probably influenced by a greater availability of water and nutrients from plant residues. The soil carbon stock is not closely related to root density or root carbon stock. The data presented in this study do not provide a definitive conclusion.

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