scholarly journals Similar importance of edaphic and climatic factors for controlling soil organic carbon stocks of the world

2021 ◽  
Vol 18 (6) ◽  
pp. 2063-2073
Author(s):  
Zhongkui Luo ◽  
Raphael A. Viscarra-Rossel ◽  
Tian Qian
Keyword(s):  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Soil Properties ◽  
Climatic Factors ◽  
Net Primary Production ◽  
Field Capacity ◽  
Soil Layers ◽  
Soil Organic Carbon Stocks ◽  
Soc Stocks

Abstract. Soil organic carbon (SOC) accounts for two-thirds of terrestrial carbon. Yet, the role of soil physicochemical properties in regulating SOC stocks is unclear, inhibiting reliable SOC predictions under land use and climatic changes. Using legacy observations from 141 584 soil profiles worldwide, we disentangle the effects of biotic, climatic and edaphic factors (a total of 31 variables) on the global spatial distribution of SOC stocks in four sequential soil layers down to 2 m. The results indicate that the 31 variables can explain 60 %–70 % of the global variance of SOC in the four layers, to which climatic variables and edaphic properties each contribute ∼35 % except in the top 20 cm soil. In the top 0–20 cm soil, climate contributes much more than soil properties (43 % vs. 31 %), while climate and soil properties show the similar importance in the 20–50, 50–100 and 100–200 cm soil layers. However, the most important individual controls are consistently soil-related and include soil texture, hydraulic properties (e.g. field capacity) and pH. Overall, soil properties and climate are the two dominant controls. Apparent carbon inputs represented by net primary production, biome type and agricultural cultivation are secondary, and their relative contributions were ∼10 % in all soil depths. This dominant effect of individual soil properties challenges the current climate-driven framework of SOC dynamics and needs to be considered to reliably project SOC changes for effective carbon management and climate change mitigation.

scholarly journals Soil properties override climate controls on global soil organic carbon stocks

2020 ◽  
Author(s):  
Zhongkui Luo ◽  
Raphael Viscarra-Rossel
Keyword(s):  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Soil Properties ◽  
Physiochemical Properties ◽  
Soil Organic Carbon Stocks ◽  
Global Soil ◽  
Climate Controls ◽  
Edaphic Properties ◽  
Soc Stocks

Abstract. Soil organic carbon (SOC) accounts for two-thirds of terrestrial carbon. Yet, the role of soil physiochemical properties in regulating SOC stocks is unclear, inhibiting reliable SOC predictions under land use and climatic changes. Using legacy observations from 141,584 soil profiles worldwide, we disentangle the effects of biotic, climatic and edaphic factors (a total of 30 variables) on the global spatial distribution of SOC stocks in four sequential soil layers down to 2 m. The results indicate that the 30 variables can explain 70–80 % of the global variance of SOC in the four layers, to which edaphic properties contribute ~ 60 %. Soil lower limit is the most important individual soil properties, positively associated with SOC in all layers, while climatic variables are secondary. This dominant effect of soil properties challenges current climate-driven framework of SOC dynamics, and need to be considered to reliably project SOC changes for effective carbon management and climate change mitigation.

scholarly journals Spatial heterogeneity and environmental predictors of permafrost region soil organic carbon stocks

2021 ◽  
Vol 7 (9) ◽  
pp. eaaz5236 ◽  
Author(s):  
Umakant Mishra ◽  
Gustaf Hugelius ◽  
Eitan Shelef ◽  
Yuanhe Yang ◽  
Jens Strauss ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Spatial Heterogeneity ◽  
Surface Air Temperature ◽  
Spatially Explicit ◽  
Soil Profiles ◽  
Permafrost Region ◽  
Environmental Predictors ◽  
Soil Organic Carbon Stocks ◽  
Soc Stocks

Large stocks of soil organic carbon (SOC) have accumulated in the Northern Hemisphere permafrost region, but their current amounts and future fate remain uncertain. By analyzing dataset combining >2700 soil profiles with environmental variables in a geospatial framework, we generated spatially explicit estimates of permafrost-region SOC stocks, quantified spatial heterogeneity, and identified key environmental predictors. We estimated that 1014−175+194 Pg C are stored in the top 3 m of permafrost region soils. The greatest uncertainties occurred in circumpolar toe-slope positions and in flat areas of the Tibetan region. We found that soil wetness index and elevation are the dominant topographic controllers and surface air temperature (circumpolar region) and precipitation (Tibetan region) are significant climatic controllers of SOC stocks. Our results provide first high-resolution geospatial assessment of permafrost region SOC stocks and their relationships with environmental factors, which are crucial for modeling the response of permafrost affected soils to changing climate.

scholarly journals Soil organic carbon stocks are systematically overestimated by misuse of the parameters bulk density and stone content

2016 ◽  
Author(s):  
Christopher Poeplau ◽  
Cora Vos ◽  
Axel Don
Keyword(s):  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Bulk Density ◽  
Agricultural Soils ◽  
Soil Layer ◽  
Future Studies ◽  
Soil Organic Carbon Stocks ◽  
Soc Stock ◽  
The Mean ◽  
Soc Stocks

Abstract. Estimation of soil organic carbon (SOC) stocks requires estimates of the carbon content, bulk density, stone content and depth of a respective soil layer. However, different application of these parameters could introduce a considerable bias. Here, we explain why three out of four frequently applied methods overestimate SOC stocks. In stone rich soils (> 30 Vol. %), SOC stocks could be overestimated by more than 100 %, as revealed by using German Agricultural Soil Inventory data. Due to relatively low stone content, the mean systematic overestimation for German agricultural soils was 2.1–10.1 % for three different commonly used equations. The equation ensemble as re-formulated here might help to unify SOC stock determination and avoid overestimation in future studies.

The resilience of soil organic carbon stocks under contrasting hill country pasture management practices

2021 ◽  
Vol 17 ◽  
Author(s):  
Alec Mackay ◽  
Ronaldo Eduardo Vibart ◽  
Catherine McKenzie ◽  
Brian Devantier ◽  
Emma Noakes
Keyword(s):  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Management Practices ◽  
Pasture Management ◽  
Single Superphosphate ◽  
Hill Country ◽  
Soil Organic Carbon Stocks ◽  
Environmental Goals ◽  
The Stability ◽  
Soc Stocks

In 2020 we measured the stability of soil organic carbon (SOC) concentrations and stocks under contrasting hill country pasture regimes, by sampling three slope classes and three aspect locations on each of three farmlets of a long-term phosphorus fertiliser and sheep grazing experiment. The farmlets included no annual phosphorus (NF), 125 kg of single superphosphate/ha (LF), or 375 kg superphosphate/ha (HF) that has been applied on an annual basis since 1980. Results from the 2020 sampling event were added to previous results reported from soil samples collected in 2003 and 2014. The SOC concentrations in the topsoil (0-75 mm depth), ranging from 4.23 to 5.99% across all slopes and aspects of the farmlets, fell within the normal range (≥3.5 and <7.0%) required for sustaining production and environmental goals. A trend was shown for greater SOC stocks in the topsoil in the HF farmlet (34.0 Mg/ ha) compared with the other two farmlets (31.6 Mg/ha), but this trend was not evident in the deeper soil layers (75-150, 150-300, 0-300 mm). Under the current conditions, topographical features such as slope and aspect had a more profound influence on SOC stocks than management history.

scholarly journals Divergent controls of soil organic carbon between observations and process-based models

2021 ◽  
Author(s):  
Katerina Georgiou ◽  
Avni Malhotra ◽  
William R. Wieder ◽  
Jacqueline H. Ennis ◽  
Melannie D. Hartman ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Primary Productivity ◽  
Net Primary Productivity ◽  
Global Scale ◽  
Mean Annual Temperature ◽  
Biogeochemical Models ◽  
Soc Stocks ◽  
Process Based Models

AbstractThe storage and cycling of soil organic carbon (SOC) are governed by multiple co-varying factors, including climate, plant productivity, edaphic properties, and disturbance history. Yet, it remains unclear which of these factors are the dominant predictors of observed SOC stocks, globally and within biomes, and how the role of these predictors varies between observations and process-based models. Here we use global observations and an ensemble of soil biogeochemical models to quantify the emergent importance of key state factors – namely, mean annual temperature, net primary productivity, and soil mineralogy – in explaining biome- to global-scale variation in SOC stocks. We use a machine-learning approach to disentangle the role of covariates and elucidate individual relationships with SOC, without imposing expected relationships a priori. While we observe qualitatively similar relationships between SOC and covariates in observations and models, the magnitude and degree of non-linearity vary substantially among the models and observations. Models appear to overemphasize the importance of temperature and primary productivity (especially in forests and herbaceous biomes, respectively), while observations suggest a greater relative importance of soil minerals. This mismatch is also evident globally. However, we observe agreement between observations and model outputs in select individual biomes – namely, temperate deciduous forests and grasslands, which both show stronger relationships of SOC stocks with temperature and productivity, respectively. This approach highlights biomes with the largest uncertainty and mismatch with observations for targeted model improvements. Understanding the role of dominant SOC controls, and the discrepancies between models and observations, globally and across biomes, is essential for improving and validating process representations in soil and ecosystem models for projections under novel future conditions.

scholarly journals Soil organic carbon stocks are systematically overestimated by misuse of the parameters bulk density and rock fragment content

SOIL ◽  
2017 ◽  
Vol 3 (1) ◽  
pp. 61-66 ◽  
Author(s):  
Christopher Poeplau ◽  
Cora Vos ◽  
Axel Don
Keyword(s):  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Bulk Density ◽  
Agricultural Soils ◽  
Soil Layer ◽  
Rock Fragment ◽  
Rock Fragments ◽  
Soil Organic Carbon Stocks ◽  
Soc Stocks ◽  
Rock Fragment Content

Abstract. Estimation of soil organic carbon (SOC) stocks requires estimates of the carbon content, bulk density, rock fragment content and depth of a respective soil layer. However, different application of these parameters could introduce a considerable bias. Here, we explain why three out of four frequently applied methods overestimate SOC stocks. In soils rich in rock fragments (> 30 vol. %), SOC stocks could be overestimated by more than 100 %, as revealed by using German Agricultural Soil Inventory data. Due to relatively low rock fragments content, the mean systematic overestimation for German agricultural soils was 2.1–10.1 % for three different commonly used equations. The equation ensemble as re-formulated here might help to unify SOC stock determination and avoid overestimation in future studies.

scholarly journals Litter contribution to soil organic carbon in the processes of agriculture abandon

Solid Earth ◽  
2015 ◽  
Vol 6 (2) ◽  
pp. 425-432 ◽  
Author(s):  
A. Novara ◽  
J. Rühl ◽  
T. La Mantia ◽  
L. Gristina ◽  
S. La Bella ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Soil Profile ◽  
Secondary Succession ◽  
Co2 Emission ◽  
Soil Cores ◽  
Soil Layers ◽  
C Stock ◽  
One Year

Abstract. The mechanisms of litter decomposition, translocation and stabilization into soil layers are fundamental processes in the functioning of the ecosystem, as they regulate the cycle of soil organic matter (SOM) and CO2 emission into the atmosphere. In this study the contribution of litters of different stages of Mediterranean secondary succession on carbon sequestration was investigated, analyzing the role of earthworms in the translocation of SOM into the soil profile. For this purpose the δ13C difference between meadow C4-C soil and C3-C litter was used in a field experiment. Four undisturbed litters of different stages of succession (45, 70, 100 and 120 since agriculture abandon) were collected and placed on the top of isolated C4 soil cores. The litter contribution to C stock was affected by plant species and it increased with the age of the stage of secondary succession. One year after the litter position, the soil organic carbon increased up to 40% in comparison to soils not treated with litter after 120 years of abandon. The new carbon derived from C3 litter was decomposed and transferred into soil profile thanks to earthworms and the leaching of dissolved organic carbon. After 1 year the carbon increase attributed to earthworm activity was 6 and 13% in the soils under litter of fields abandoned for 120 and 45 years, respectively.

Impacts of fire on soil organic carbon stocks in a grazed semi-arid tropical Australian savanna: accounting for landscape variability

2014 ◽  
Vol 36 (4) ◽  
pp. 359 ◽  
Author(s):  
D. E. Allen ◽  
P. M. Bloesch ◽  
R. A. Cowley ◽  
T. G. Orton ◽  
J. E. Payne ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Spatial Variability ◽  
Management Practices ◽  
Soil Depth ◽  
Carbon Stocks ◽  
Soil Organic Carbon Stocks ◽  
Semi Arid ◽  
Soc Stocks

Fire and grazing are commonplace in Australian tropical savannas and the effects of these management practices on soil organic carbon stocks (SOC) is not well understood. A long-term (20 years) experiment studying the effects of fire on a grazed semi-arid tropical savanna was used to increase this understanding. Treatments, including frequency of fire (every 2, 4 and 6 years), season of fire [early (June) vs late (October) dry season] and unburnt control plots, were imposed on Vertosol grassland and Calcarosol woodland sites, which were grazed. Additionally long-term enclosures [unburnt (except the Calcarosol in 2001) and ungrazed since 1973] on each soil type adjacent to each site were sampled, although not included in statistical analyses. SOC stocks were measured to a soil depth of 0.3 m using a wet oxidation method (to avoid interference by carbonates) and compared on an equivalent soil mass basis. Significant treatment differences in SOC stocks were tested for, while accounting for spatial background variation within each site. SOC stocks (0–0.3 m soil depth) ranged between 10.1 and 28.9 t ha–1 (Vertosol site) and 20.7 and 54.9 t ha–1 (Calcarosol site). There were no consistent effects of frequency or season of fire on SOC stocks, possibly reflecting the limited statistical power of the study and inherent spatial variability observed. Differences in the response to frequency and season of fire observed between these soils may have been due to differences in clay type, plant species composition and/or preferential grazing activity associated with fire management. There may also have been differences in C input between treatments and sites due to differences in the herbage mass and post-fire grazing activity on both sites and changed pasture composition, higher herbage fuel load, and a reduction in woody cover on the Vertosol site. This study demonstrated the importance of accounting for background spatial variability and treatment replication (in the absence of baseline values) when assessing SOC stocks in relation to management practices. Given the absence of baseline SOC values and the potentially long period required to obtain changes in SOC in rangelands, modelling of turnover of SOC in relation to background spatial variability would enable management scenarios to be considered in relation to landscape variation that may be unrelated to management. These considerations are important for reducing uncertainty in C-flux accounting and to provide accurate and cost-effective methods for land managers considering participation in the C economy.

scholarly journals Dwarf Shrubs Impact Tundra Soils: Drier, Colder, and Less Organic Carbon

Ecosystems ◽  
2021 ◽  
Author(s):  
Julia Kemppinen ◽  
Pekka Niittynen ◽  
Anna-Maria Virkkala ◽  
Konsta Happonen ◽  
Henri Riihimäki ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Soil Properties ◽  
Woody Plants ◽  
Structural Equation ◽  
Carbon Stocks ◽  
Tundra Soils ◽  
Dwarf Shrubs ◽  
Soil Organic Carbon Stocks ◽  
Tundra Ecosystem

AbstractIn the tundra, woody plants are dispersing towards higher latitudes and altitudes due to increasingly favourable climatic conditions. The coverage and height of woody plants are increasing, which may influence the soils of the tundra ecosystem. Here, we use structural equation modelling to analyse 171 study plots and to examine if the coverage and height of woody plants affect the growing-season topsoil moisture and temperature (< 10 cm) as well as soil organic carbon stocks (< 80 cm). In our study setting, we consider the hierarchy of the ecosystem by controlling for other factors, such as topography, wintertime snow depth and the overall plant coverage that potentially influence woody plants and soil properties in this dwarf shrub-dominated landscape in northern Fennoscandia. We found strong links from topography to both vegetation and soil. Further, we found that woody plants influence multiple soil properties: the dominance of woody plants inversely correlated with soil moisture, soil temperature, and soil organic carbon stocks (standardised regression coefficients = − 0.39; − 0.22; − 0.34, respectively), even when controlling for other landscape features. Our results indicate that the dominance of dwarf shrubs may lead to soils that are drier, colder, and contain less organic carbon. Thus, there are multiple mechanisms through which woody plants may influence tundra soils.

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