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Soil organic carbon (SOC) storage and erosion in South China at the regional scale in the past decades remains far from being understood. This paper calculated the SOC density, storage and erosion in 14 soil classes in Guangdong P...
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Soil organic carbon (SOC) storage and erosion in South China at the regional scale in the past decades remains far from being understood. This paper calculated the SOC density, storage and erosion in 14 soil classes in Guangdong Province, South China, based on statistical data from the soil survey and soil erosion survey of Guangdong, which was performed in the 1990s. The purpose of this study is to understand the relationships between soil classes and SOC erosion at the regional scale. The results indicated that the SOC density in the soils of Guangdong varied from 12.7 to 144.9 Mg ha~(-1) over the entire profile and from 12.6 to 68.4 Mg ha~(-1) in the top 20-cm soil layer. The average area-weighted SOC density in the topsoil (0-20 cm) and the entire profile was 32 ± 3 and 86 ± 4 Mg ha~(-1), respectively. The total SOC storage was 1.27 ± 0.06 Pg, with 35.6 % (0.46 ± 0.04 Pg) located in the topsoil. The average area-weighted strength of the SOC erosion in the 1990s was 20.6 ± 0.8 Mg km~(-2) year~(-1). The results indicated that SOC erosion was strongly related to soil class.
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The objective of this 20-year tillage study was to quantify the amount and rates of soil organic carbon (SOC) storage and retention as a result of a conversion to no-till (NT) or chisel plow (CP) tillage systems using the comparis...
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The objective of this 20-year tillage study was to quantify the amount and rates of soil organic carbon (SOC) storage and retention as a result of a conversion to no-till (NT) or chisel plow (CP) tillage systems using the comparison method with moldboard plow (MP) tillage SOC data as baseline. The NT and CP plots did store and retain 8.4 Mg C ha(-1) and 0.6 Mg C ha(-1) more SOC in the soil than MP. That SOC amount was retained in the soil and not decomposed and re-emitted to the atmosphere as a result of cultivation or in the transported sediment moved off of the plots. However, no SOC sequestration occurred in the NT, CP, and MP plots because the SOC level of the plot area was higher at the start of the experiment than at the end of the study. Pretreatment SOC baseline of the plot area was used to determine NT, CP, and MP SOC sequestration or loss. The NT plots actually lost a total of -6.8 Mg C ha(-1), the CP lost -15.1 Mg C ha(-1), and the MP lost -15.2 Mg C ha(-1) during the 20-year study. Soil erosion and transport of SOC rich sediment off of the sloping plots contributed substantially (29%-39%) to these SOC losses. These findings suggest that determination of a pretreatment SOC baseline is essential in all tillage comparison studies to determine the amount and rate of SOC sequestration or loss.
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Soil organic carbon (SOC) in agricultural land forms part of the global terrestrial carbon cycle and it affects atmospheric carbon dioxide balance. SOC is sensitive to local agricultural management practices that sum up into regio...
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Soil organic carbon (SOC) in agricultural land forms part of the global terrestrial carbon cycle and it affects atmospheric carbon dioxide balance. SOC is sensitive to local agricultural management practices that sum up into regional SOC storage dynamics. Understanding regional carbon emission and sequestration trends is, therefore, important in formulating and implementing climate change adaptation and mitigation policies. In this study, the estimation of SOC stock and regional storage dynamics in the Ondavská Vrchovina region (North-Eastern Slovakia) cropland and grassland topsoil between 1970 and 2013 was performed with the RothC model and gridded spatial data on weather, initial SOC stock and historical land cover and land use changes. Initial SOC stock in the 0.3-m topsoil layer was estimated at 38.4 t ha<sup>?1</sup> in 1970. The 2013 simulated value was 49.2 t ha<sup>?1</sup>, and the 1993–2013 simulated SOC stock values were within the measured data range. The total SOC storage in the study area, cropland and grassland areas, was 4.21 Mt in 1970 and 5.16 Mt in 2013, and this 0.95 Mt net SOC gain was attributed to inter-conversions of cropland and grassland areas between 1970 and 2013, which caused different organic carbon inputs to the soil during the simulation period with a strong effect on SOC stock temporal dynamics.
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Soil microbes' activity is very important for forming of the nutrient stock and, soil structure, as well as the carbon cycle simulation. This is particularly crucial for deep soil layers. Effect of soil microbes on the rate of acc...
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Soil microbes' activity is very important for forming of the nutrient stock and, soil structure, as well as the carbon cycle simulation. This is particularly crucial for deep soil layers. Effect of soil microbes on the rate of accumulation and decomposition of the soil organic carbon (SOC) has been found for different regions. However, it is known still a little on the SOC performance for different decomposition rates and its relation to the microbial activity in the saline-alkali desert ecosystem. Therefore, the main task of our research was investigation of interrelation between the soil organic carbon and microbial carbon (SMC) at different depths in the original saline-alkali Gurbantunggiit Desert. Our results showed in the soil vertical profile, (i) SMC and SOC presented a very significant positive linear correlation (R-2 = 0.63, P = 0.0003); (ii) SMC exhibited two obvious changed-interfaces - 20 cm and 80 cm, the SMC at depth of 0-20 cm, 20-80 cm and 80-500 cm was 2.24-3.06, 0.19-0.72, and 0.0017-0.0097 mg kg(-1), respectively; (iii) in the depth of 0-20 cm and 20-80 cm, the SMC had highly significant difference (P < 0.0001) and at 20-80 cm and 80-500 cm, significant difference (P = 0.013); (iv) according to the soil division based on the SMC, SOC also had some certain stratification; (v) organic carbon layers can be respectively defined according to different microbial activities as active, inert, and stable organic carbon pool. Therefore, these three kinds of organic carbon pools can be quantitatively measured by analyzing their location at different depths of the soil profile.
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The use of three discrete soil organic carbon (SOC) pools proposed by the CENTURY model to study the SOC dynamics helps to understand the changes in cropland SOC pool and its stability. This study focuses on a typical black soil (...
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The use of three discrete soil organic carbon (SOC) pools proposed by the CENTURY model to study the SOC dynamics helps to understand the changes in cropland SOC pool and its stability. This study focuses on a typical black soil (mollisol) region in Northeast China. Based on historical soil data from samples that were collected in the 1980s, we selected 44 sampling points and collected 88 soil samples from the surface (0-20 cm) and subsurface (20-40 cm) layers in 2010. A 100-day laboratory incubation for each sample was conducted to measure the decomposition rates of SOC at different times, and data from the incubation experiment were fitted to a three-pool first-order model that divided the total SOC into active (C-a), slow (C-s) and resistant (C-r) SOC fractions. A method for predicting the concentrations of the three SOC fractions was developed and used to obtain the concentrations of SOC fractions in the 1980s at each sampling point. The results showed that a power function model (D-soct = a x t(b)) could be used as the universal SOC decomposition curve model. Using the universal model, the predictive method accurately estimated the concentrations of C-a, C-s and C-r of upland soils in this black soil region, which effectively solved the problem of a lack of soil samples and SOC fractions data in previous studies of the spatial-temporal variations of SOC fractions in regional soils. From 1980 to 2010, the estimated variations of the C-a, C-s and C-r in the surface upland soil were + 0.37, - 5.53 and - 6.32 g kg(-1), and the corresponding contributions to the loss of the total SOC were -3.2%, + 48.2% and + 55.1%, respectively, while the variations of the C-a, C-s and C-r in the subsurface soil were + 0.19,- 0.43 and - 2.45 g kg(-1), and the corresponding contributions to the loss of the total SOC were - 7.1%, + 16.0% and + 91.1%, respectively. The decrease in the total SOC is primarily attributed to the decrease of the C-s and C-r fractions in the region, although the C-a fraction has significantly increased. The overall variations in the SOC fractions suggest a declining stability of the SOC pool in the black soil region of Northeast China.
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The purpose of this study was to characterize the soil organic carbon dynamics associated with four land uses (cropland, grassland, shrubland, and forestland) in the upper Blue Nile Basin of the Ethiopian Highlands. We collected d...
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The purpose of this study was to characterize the soil organic carbon dynamics associated with four land uses (cropland, grassland, shrubland, and forestland) in the upper Blue Nile Basin of the Ethiopian Highlands. We collected diverse biophysical data to allow spatial variability of soil organic carbon and factors contributing to this variation to be determined statistically, and used well established simulation models to interpret the data, predict long-term carbon dynamics and determine the potential for improvements in soil quality and mitigation of greenhouse gas emissions. The spatial variation in soil organic carbon in the 0-20 cm soil depth was significant across study areas (P < 0.01, 21.6 g kg(-1)-37.8 g kg(-1)), and between land-uses (P < 0.05, 27.9 g kg(-1) in cropland and 43.0 g kg(-1) soil in forestland). In a multiple linear regression model, among the 11 explanatory variables used, four (total nitrogen, shrubs, trees and land use) showed a significant positive effect (P < 0.01), while three (impact of grazing, impact of erosion and clay) showed a significant negative effect (P < 0.01). Simulations using the assumption of steady state to estimate carbon dynamics suggested that plant inputs from croplands are generally lower than grass or shrublands, resulting in build-up of recalcitrant organic matter in shrublands compared to grass or croplands. Erosion results in a decline in both the absolute and relative amounts of carbon in recalcitrant pools, but the more active pools remained unchanged, meaning that the overall activity of soil organic matter is increased when the soil is eroded, and it becomes more difficult to sequester soil carbon. More rapid decrease in soil organic carbon is likely to be due to increased erosion, persistent removal of organic materials, grazing pressures, and higher rate of decompositions in cropland and grazing land-uses. Conversion to shrubland shows high potential to quickly restore eroded soils and build up a pool of recalcitrant soil carbon, suggesting that management of land using periodic 20 year exclosures, preventing cropping and grazing and allowing shrubland succession, could be beneficial in restoring degraded soils. Simulations using a calibration approach, rather than assuming steady state, corroborated these findings, suggesting that after 30 years of current management, croplands will deplete soil organic carbon by 5.6, 7.1 and 7.2 t ha(-1), and grasslands by 3.5, 3.9 and 2.7 t ha(-1), while shrublands will build-up soil organic carbon by 0.6, 0.1 and 1.3 t ha(-1) at study sites. At one study site, forests, will further increase soil organic carbon by 6.7 t ha(-1) after 30 years. The significant positive impact of shrubs and trees on soil organic carbon suggests the need to focus on introduction of agroforestry systems in crop and grasslands. (C) 2015 Elsevier B.V. All rights reserved.
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Soil is a prominent component of terrestrial C and N budgets. Soil C and N pools are influenced by, and may reciprocally influence, many environmental factors. Our objective was to determine the quantitative relations of surface m...
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Soil is a prominent component of terrestrial C and N budgets. Soil C and N pools are influenced by, and may reciprocally influence, many environmental factors. Our objective was to determine the quantitative relations of surface mineral-soil organic C, N, and C/N ratios to climate and soil texture across seven ecological regions that make up the conterminous USA. Up to 608 soil profiles per region and their corresponding climates were evaluated with regression analysis. The organic C pool (kg C m?2) in the upper 20 cm of mineral soil was positively related to mean annual precipitation, evapotranspiration and clay content in all regions. It was negatively related to a temperature/precipitation index in all regions and negatively related to mean annual temperature, except in the northwest temperate forest region. Soil C/N ratios were negatively related to clay or silt content in all regions. These relations are consistent with concepts of moisture and temperature controls on detrital production, differential effects of temperature on detrital production and decomposition, and stabilization of organic matter by clay and silt. Differences in quantitative relations among regions may be related to vegetation-composition effects on soil organic matter processes, clay mineralogy, and faunal mixing of surface organic horizons with mineral soil. Regional differences also occurred in the importance of climate vs. soil texture in explaining the variability in soil C. The regional differences indicate the importance of using region-specific, rather than generalized, equations for projecting long-term soil responses to climate change and for conducting ecosystem-model calibration or validation.
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Forest soils are a key element of the forest ecosystems which could contribute to carbon storage and climate change mitigation. The carbon sequestration and storage potential of the forest soils, however, depends to a great extent...
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Forest soils are a key element of the forest ecosystems which could contribute to carbon storage and climate change mitigation. The carbon sequestration and storage potential of the forest soils, however, depends to a great extent on the forestry operations and forest management activities carried out in the forest. There is a widely accepted assumption that under a set of climate and management conditions the carbon content in the forest soils is at equilibrium. However, different factors like management activities, productivity, decay rates and/or natural disturbances could alter the carbon dynamics of forest soils. The aim of the current study was to assess the carbon stock and the carbon stock changes in mineral forest soils in Bulgaria based on the forest soil monitoring information gathered under the ICP Forest Programme. For that purpose, a dataset from the programme on mineral forest soils from 1998 was processed and analysed. The carbon stock for each sample plot was estimated for the 0-30 cm layer. The carbon stock change was calculated for all the sample plots with repeated measurements over the study period. The results were further analysed with parametric and non-parametric statistical tests to assess whether the carbon stock changes are significant. However, the lack of other relevant observations within the monitoring implementation such as litter decomposition, turnover rates, climatic conditions, etc., hinder the application of dynamic soil carbon models in assessing and predicting the current and the future rate of the soil carbon in forests in Bulgaria.
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摘要 :
Soil organic carbon (SOC) in agricultural land forms part of the global terrestrial carbon cycle and it affects atmospheric carbon dioxide balance. SOC is sensitive to local agricultural management practices that sum up into regio...
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Soil organic carbon (SOC) in agricultural land forms part of the global terrestrial carbon cycle and it affects atmospheric carbon dioxide balance. SOC is sensitive to local agricultural management practices that sum up into regional SOC storage dynamics. Understanding regional carbon emission and sequestration trends is, therefore, important in formulating and implementing climate change adaptation and mitigation policies. In this study, the estimation of SOC stock and regional storage dynamics in the Ondavská Vrchovina region (North-Eastern Slovakia) cropland and grassland topsoil between 1970 and 2013 was performed with the RothC model and gridded spatial data on weather, initial SOC stock and historical land cover and land use changes. Initial SOC stock in the 0.3-m topsoil layer was estimated at 38.4 t ha-~1 in 1970. The 2013 simulated value was 49.2 t ha-1, and the 1993-2013 simulated SOC stock values were within the measured data range. The total SOC storage in the study area, cropland and grassland areas, was 4.21 Mt in 1970 and 5.16 Mt in 2013,and this 0.95 Mt net SOC gain was attributed to interconversions of cropland and grassland areas between 1970 and 2013, which caused different organic carbon inputs to the soil during the simulation period with a strong effect on SOC stock temporal dynamics.
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