scholarly journals Long-term bare fallow experiments offer new opportunities for the quantification and the study of stable carbon in soil

2010 ◽  
Vol 7 (3) ◽  
pp. 4887-4917 ◽  
Author(s):  
P. Barré ◽  
T. Eglin ◽  
B. T. Christensen ◽  
P. Ciais ◽  
S. Houot ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Soil Carbon ◽  
Co2 Concentration ◽  
Soil C ◽  
Climate Conditions ◽  
Stable Pool ◽  
Bare Fallow ◽  
The Stability ◽  
A Site

Abstract. The stability of soil carbon is a major source of uncertainty for the prediction of atmospheric CO2 concentration during the 21st century. Isolating experimentally the stable soil carbon from other, more vulnerable, pools is of prime importance for calibrating soil C models, and gaining insights on the mechanisms leading to soil organic carbon (SOC) stability. Long-term bare fallow experiments, in which the decay of SOC is monitored for decades after inputs from plant material have stopped, represent a unique opportunity to assess the stable organic carbon. We synthesized data from 6 bare fallow experiments of long-duration, covering a range of soil types and climate conditions, at Askov (Denmark), Grignon and Versailles (France), Kursk (Russia), Rothamsted (UK), and Ultuna (Sweden). The conceptual model of SOC being divided into three pools with increasing turnover times, a labile pool (~ years), an intermediate pool (~ decades) and a stable pool (~ several centuries or more) fits well with the long term SOC decays observed in bare fallow soils. The modeled stable pool estimates ranged from 2.7 gC kg−1 at Rothamsted to 6.8 gC kg−1 at Grignon. The uncertainty over the identification of the stable pool is large due to the short length of the fallow records relative to the time scales involved in the decay of soil C. At Versailles, where there is least uncertainty associated with the determination of a stable pool, the soil contains predominantly stable C after 80 years of continuous bare fallow. Such a site represents a unique research platform for future experimentation addressing the characteristics of stable SOC and its vulnerability to global change.

scholarly journals Quantifying and isolating stable soil organic carbon using long-term bare fallow experiments

2010 ◽  
Vol 7 (11) ◽  
pp. 3839-3850 ◽  
Author(s):  
P. Barré ◽  
T. Eglin ◽  
B. T. Christensen ◽  
P. Ciais ◽  
S. Houot ◽  
...  
Keyword(s):  
Simulation Models ◽  
Co2 Concentration ◽  
Turnover Time ◽  
Soil C ◽  
Climate Conditions ◽  
Stable Pool ◽  
Pool Model ◽  
Bare Fallow ◽  
The Stability

Abstract. The stability of soil organic matter (SOM) is a major source of uncertainty in predicting atmospheric CO2 concentration during the 21st century. Isolating the stable soil carbon (C) from other, more labile, C fractions in soil is of prime importance for calibrating soil C simulation models, and gaining insights into the mechanisms that lead to soil C stability. Long-term experiments with continuous bare fallow (vegetation-free) treatments in which the decay of soil C is monitored for decades after all inputs of C have stopped, provide a unique opportunity to assess the quantity of stable soil C. We analyzed data from six bare fallow experiments of long-duration (>30 yrs), covering a range of soil types and climate conditions, and sited at Askov (Denmark), Grignon and Versailles (France), Kursk (Russia), Rothamsted (UK), and Ultuna (Sweden). A conceptual three pool model dividing soil C into a labile pool (turnover time of a several years), an intermediate pool (turnover time of a several decades) and a stable pool (turnover time of a several centuries or more) fits well with the long term C decline observed in the bare fallow soils. The estimate of stable C ranged from 2.7 g C kg−1 at Rothamsted to 6.8 g C kg−1 at Grignon. The uncertainty associated with estimates of the stable pool was large due to the short duration of the fallow treatments relative to the turnover time of stable soil C. At Versailles, where there is least uncertainty associated with the determination of a stable pool, the soil contains predominantly stable C after 80 years of continuous bare fallow. Such a site represents a unique research platform for characterization of the nature of stable SOM and its vulnerability to global change.

scholarly journals Long-term Fertilization Enhances Soil Carbon Stability by Increase the Ratio of Passive Carbon: Evidence From Four Typical Croplands

2021 ◽  
Author(s):  
Wei Zhou ◽  
Shilin Wen ◽  
Yunlong Zhang ◽  
Andrew S. Gregory ◽  
Minggang Xu ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Soil Carbon ◽  
Active Carbon ◽  
Large Scale ◽  
Carbon Accumulation ◽  
Response Ratio ◽  
Soil Carbon Accumulation ◽  
The Stability

Abstract Aims Soil organic carbon (SOC) plays an important role in improving soil quality, however how long-term fertilization influences SOC and contrasting active carbon (AC) and passive C (PC) pools at large scale remains unclear. The aim of this study was to examine the effect of long-term fertilization on SOC, including AC and PC, across four typical croplands in China and to explore the potential relationships and mechanism. Methods We assessed the effect of different fertilization (standard and 1.5 × standard of inorganic fertilizer (NPK) with or without manure (M), with a control for comparison) at soil depths (0-20 cm, 20-40 cm, 40-60 cm) on SOC, AC and PC. Results We found that SOC, AC and PC increased in the order Control < NPK < NPKM < 1.5NPKM. 1.5NPKM resulted in a significant increase in SOC, AC and PC, of 76.3%, 53.0% and 108.5% respectively across the soil profile (0-60 cm) compared with Control. The response ratio of PC to long-term fertilization was 2.1 times greater than that of AC across four sites on average. In addition, Clay was identified as the most important factor in explaining the response of AC and PC to different fertilization application, respectively. Conclusions Long-term fertilization enhanced both AC and PC, but the greater response of PC suggests that fertilization application could enhance the stability of carbon and thus the potential of cropland for soil carbon accumulation.

scholarly journals Boreal forest soil chemistry drives soil organic carbon bioreactivity along a 314-year fire chronosequence

2019 ◽  
Author(s):  
Benjamin Andrieux ◽  
David Paré ◽  
Julien Beguin ◽  
Pierre Grondin ◽  
Yves Bergeron
Keyword(s):  
Organic Carbon ◽  
Soil Carbon ◽  
Soil Chemistry ◽  
Mineral Soil ◽  
Chemical Properties ◽  
Soil C ◽  
C Pools ◽  
Time Since Fire ◽  
C Stock

Abstract. Following wildfire, organic carbon (C) accumulates in boreal forest soils. The long-term patterns of accumulation as well as the mechanisms responsible for continuous soil C stabilization or sequestration are poorly known. We evaluated post-fire C stock changes in functional reservoirs (bioreactive and recalcitrant) using the proportion of C mineralized in CO2 by microbes in a long-term lab incubation, as well as the proportion of C resistant to acid hydrolysis. We found that all soil C pools increased linearly with time since fire. The bioreactive and acid-insoluble soil C pools increased at a rate of 0.02 MgC ha−1 yr−1 and 0.12 MgC ha−1 yr−1, respectively, and their proportions relative to total soil C stock remained constant with time since fire (8 % and 46 %, respectively). We quantified direct and indirect causal relationships among variables and carbon bioreactivity to disentangle the relative contribution of climate, moss dominance, soil particle size distribution and soil chemical properties (pH, exchangeable Mn and Al, and metal oxides) to the variation structure of in vitro soil carbon bioreactivity. Our analyses showed that the chemical properties of Podzolic soils that characterise the study area were the best predictors of soil carbon bioreactivity. For the FH horizon (O-layer), pH and exchangeable Mn were the most important (model-averaged estimator for both: 0.34) factors directly related to soil organic C bioreactivity, followed by time since fire (0.24), moss dominance (0.08) and climate and texture (0 for both). For the mineral soil, exchangeable aluminum was the most important factor (model-averaged estimator: −0.32), followed by metal oxide (−0.27), pH (−0.25), time since fire (0.05), climate and texture (~ 0 for both). Of the four climate factors examined in this study (i.e., mean annual temperature, growing degree-days above 5 °C, mean annual precipitation and water balance) only those related to water availability, and not to temperature, had indirect effect (FH horizon) or a marginal indirect effect (mineral soil) on soil carbon bioreactivity. Given that predictions of the impact of climate change on soil carbon balance are strongly linked to the size and the bioreactivity of soil C pools, our study stresses the need to include the direct effects of soil chemistry and the indirect effects of climate and soil texture on soil C decomposition in Earth System Models to forecast the response of boreal soils to global warming.

scholarly journals Long-Term Nitrogen Addition Decreases Soil Carbon Mineralization in an N-Rich Primary Tropical Forest

Forests ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 734
Author(s):  
Xiankai Lu ◽  
Qinggong Mao ◽  
Zhuohang Wang ◽  
Taiki Mori ◽  
Jiangming Mo ◽  
...  
Keyword(s):  
Microbial Biomass ◽  
Organic Carbon ◽  
Tropical Forest ◽  
Soil Carbon ◽  
Tropical Forests ◽  
Carbon Mineralization ◽  
N Deposition ◽  
Soil Carbon Mineralization ◽  
N Additions

Anthropogenic elevated nitrogen (N) deposition has an accelerated terrestrial N cycle, shaping soil carbon dynamics and storage through altering soil organic carbon mineralization processes. However, it remains unclear how long-term high N deposition affects soil carbon mineralization in tropical forests. To address this question, we established a long-term N deposition experiment in an N-rich lowland tropical forest of Southern China with N additions such as NH4NO3 of 0 (Control), 50 (Low-N), 100 (Medium-N) and 150 (High-N) kg N ha−1 yr−1, and laboratory incubation experiment, used to explore the response of soil carbon mineralization to the N additions therein. The results showed that 15 years of N additions significantly decreased soil carbon mineralization rates. During the incubation period from the 14th day to 56th day, the average decreases in soil CO2 emission rates were 18%, 33% and 47% in the low-N, medium-N and high-N treatments, respectively, compared with the Control. These negative effects were primarily aroused by the reduced soil microbial biomass and modified microbial functions (e.g., a decrease in bacteria relative abundance), which could be attributed to N-addition-induced soil acidification and potential phosphorus limitation in this forest. We further found that N additions greatly increased soil-dissolved organic carbon (DOC), and there were significantly negative relationships between microbial biomass and soil DOC, indicating that microbial consumption on soil-soluble carbon pool may decrease. These results suggests that long-term N deposition can increase soil carbon stability and benefit carbon sequestration through decreased carbon mineralization in N-rich tropical forests. This study can help us understand how microbes control soil carbon cycling and carbon sink in the tropics under both elevated N deposition and carbon dioxide in the future.

Increase in soil stable carbon isotope ratio relates to loss of organic carbon: results from five long-term bare fallow experiments

Oecologia ◽  
2014 ◽  
Vol 177 (3) ◽  
pp. 811-821 ◽  
Author(s):  
Lorenzo Menichetti ◽  
Sabine Houot ◽  
Folkert van Oort ◽  
Thomas Kätterer ◽  
Bent T. Christensen ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Carbon Isotope ◽  
Isotope Ratio ◽  
Stable Carbon Isotope ◽  
Carbon Isotope Ratio ◽  
Stable Carbon ◽  
Stable Carbon Isotope Ratio ◽  
Bare Fallow

scholarly journals Carbon storage in seagrass soils: long-term nutrient history exceeds the effects of near-term nutrient enrichment

2016 ◽  
Vol 13 (1) ◽  
pp. 313-321 ◽  
Author(s):  
A. R. Armitage ◽  
J. W. Fourqurean
Keyword(s):  
Organic Carbon ◽  
Soil Carbon ◽  
Carbon Stock ◽  
Seagrass Beds ◽  
Nutrient Input ◽  
High Carbon ◽  
Phosphorus Addition ◽  
Seagrass Biomass ◽  
Near Term

Abstract. The carbon sequestration potential in coastal soils is linked to aboveground and belowground plant productivity and biomass, which in turn, is directly and indirectly influenced by nutrient input. We evaluated the influence of long-term and near-term nutrient input on aboveground and belowground carbon accumulation in seagrass beds, using a nutrient enrichment (nitrogen and phosphorus) experiment embedded within a naturally occurring, long-term gradient of phosphorus availability within Florida Bay (USA). We measured organic carbon stocks in soils and above- and belowground seagrass biomass after 17 months of experimental nutrient addition. At the nutrient-limited sites, phosphorus addition increased the carbon stock in aboveground seagrass biomass by more than 300 %; belowground seagrass carbon stock increased by 50–100 %. Soil carbon content slightly decreased ( ∼  10 %) in response to phosphorus addition. There was a strong but non-linear relationship between soil carbon and Thalassia testudinum leaf nitrogen : phosphorus (N : P) or belowground seagrass carbon stock. When seagrass leaf N : P exceeded an approximate threshold of 75 : 1, or when belowground seagrass carbon stock was less than 100 g m−2, there was less than 3 % organic carbon in the sediment. Despite the marked difference in soil carbon between phosphorus-limited and phosphorus-replete areas of Florida Bay, all areas of the bay had relatively high soil carbon stocks near or above the global median of 1.8 % organic carbon. The relatively high carbon content in the soils indicates that seagrass beds have extremely high carbon storage potential, even in nutrient-limited areas with low biomass or productivity.

Herbage biomass and its relationship to soil carbon under long-term grazing in northern temperate grasslands

2019 ◽  
Vol 99 (6) ◽  
pp. 905-916
Author(s):  
E.W. Bork ◽  
M.P. Lyseng ◽  
D.B. Hewins ◽  
C.N. Carlyle ◽  
S.X. Chang ◽  
...  
Keyword(s):  
Soil Carbon ◽  
Root Biomass ◽  
Mineral Soil ◽  
Belowground Biomass ◽  
Cattle Grazing ◽  
Shoot Biomass ◽  
Positive Contribution ◽  
Temperate Grasslands ◽  
Soil C

While northern temperate grasslands are important for supporting beef production, it remains unclear how grassland above- and belowground biomass responds to long-term cattle grazing. Here, we use a comprehensive dataset from 73 grasslands distributed across a broad agro-climatic gradient to quantify grassland shoot, litter, and shallow (top 30 cm) root biomass in areas with and without grazing. Additionally, we relate biomass to soil carbon (C) concentrations. Forb biomass was greater (p < 0.05) in grazed areas, particularly those receiving more rainfall. In contrast, grass and total aboveground herbage biomass did not differ with grazing (total: 2320 kg ha−1 for grazed vs. 2210 kg ha−1 for non-grazed; p > 0.05). Forb crude protein concentrations were lower (p < 0.05) in grazed communities compared with those that were non-grazed. Grasslands subjected to grazing had 56% less litter mass. Root biomass down to 30 cm remained similar between areas with (9090 kg ha−1) and without (7130 kg ha−1) grazing (p > 0.05). Surface mineral soil C concentrations were positively related to peak grassland biomass, particularly total (above + belowground) biomass, and with increasing forb biomass in grazed areas. Finally, total aboveground shoot biomass and soil C concentrations in the top 15 cm of soil were both positively related to the proportion of introduced plant diversity in grazed and non-grazed grasslands. Overall, cattle grazing at moderate stocking rates had minimal impact on peak grassland biomass, including above- and belowground, and a positive contribution exists from introduced plant species to maintaining herbage productivity and soil C.

scholarly journals Boreal-forest soil chemistry drives soil organic carbon bioreactivity along a 314-year fire chronosequence

SOIL ◽  
2020 ◽  
Vol 6 (1) ◽  
pp. 195-213
Author(s):  
Benjamin Andrieux ◽  
David Paré ◽  
Julien Beguin ◽  
Pierre Grondin ◽  
Yves Bergeron
Keyword(s):  
Organic Carbon ◽  
Indirect Effect ◽  
Soil Chemistry ◽  
Mineral Soil ◽  
Chemical Properties ◽  
Soil C ◽  
C Pools ◽  
Time Since Fire ◽  
C Stock

Abstract. Following a wildfire, organic carbon (C) accumulates in boreal-forest soils. The long-term patterns of accumulation as well as the mechanisms responsible for continuous soil C stabilization or sequestration are poorly known. We evaluated post-fire C stock changes in functional reservoirs (bioreactive and recalcitrant) using the proportion of C mineralized in CO2 by microbes in a long-term lab incubation, as well as the proportion of C resistant to acid hydrolysis. We found that all soil C pools increased linearly with the time since fire. The bioreactive and acid-insoluble soil C pools increased at a rate of 0.02 and 0.12 MgC ha−1 yr−1, respectively, and their proportions relative to total soil C stock remained constant with the time since fire (8 % and 46 %, respectively). We quantified direct and indirect causal relationships among variables and C bioreactivity to disentangle the relative contribution of climate, moss dominance, soil particle size distribution and soil chemical properties (pH, exchangeable manganese and aluminum, and metal oxides) to the variation structure of in vitro soil C bioreactivity. Our analyses showed that the chemical properties of podzolic soils that characterize the study area were the best predictors of soil C bioreactivity. For the O layer, pH and exchangeable manganese were the most important (model-averaged estimator for both of 0.34) factors directly related to soil organic C bioreactivity, followed by the time since fire (0.24), moss dominance (0.08), and climate and texture (0 for both). For the mineral soil, exchangeable aluminum was the most important factor (model-averaged estimator of −0.32), followed by metal oxide (−0.27), pH (−0.25), the time since fire (0.05), climate and texture (∼0 for both). Of the four climate factors examined in this study (i.e., mean annual temperature, growing degree-days above 5 ∘C, mean annual precipitation and water balance) only those related to water availability – and not to temperature – had an indirect effect (O layer) or a marginal indirect effect (mineral soil) on soil C bioreactivity. Given that predictions of the impact of climate change on soil C balance are strongly linked to the size and the bioreactivity of soil C pools, our study stresses the need to include the direct effects of soil chemistry and the indirect effects of climate and soil texture on soil organic matter decomposition in Earth system models to forecast the response of boreal soils to global warming.

Management effects on the dynamics and storage rates of organic matter in long-term crop rotations

2004 ◽  
Vol 84 (1) ◽  
pp. 49-61 ◽  
Author(s):  
E. A. Paul ◽  
H. P. Collins ◽  
K. Paustian ◽  
E. T. Elliott ◽  
S. Frey ◽  
...  
Keyword(s):  
Organic Matter ◽  
C Sequestration ◽  
Organic C ◽  
Soil C ◽  
Site Analysis ◽  
Laboratory Incubation ◽  
C And N ◽  
A Site ◽  
Management Effects

Factors controlling soil organic matter (SOM) dynamics in soil C sequestration and N fertility were determined from multi-site analysis of long-term, crop rotation experiments in Western Canada. Analyses included bulk density, organic and inorganic C and N, particulate organic C (POM-C) and N (POM -N), and CO2-C evolved during laboratory incubation. The POM-C and POM-N contents varied with soil type. Differences in POM-C contents between treatments at a site (δPOM-C) were related (r2= 0.68) to treatment differences in soil C (δSOC). The CO2-C, evolved during laboratory incubation, was the most sensitive indicator of management effects. The Gray Luvisol (Breton, AB) cultivated plots had a fivefold difference in CO2-C release relative to a twofold difference in soil organic carbon (SOC). Soils from cropped, Black Chernozems (Melfort and Indian Head, SK) and Dark Brown Chernozems (Lethbridge, AB) released 50 to 60% as much CO2-C as grassland soils. Differences in CO2 evolution from the treatment with the lowest SOM on a site and that of other treatments (δCO2-C) in the early stages of the incubation were correlated to δPOM-C and this pool reflects short-term SOC storage. Management for soil fertility, such as N release, may differ from management for C sequestration. Key words: Multi-site analysis, soil management, soil C and N, POM-C and N, CO2 evolution

The Need for a New Approach to Grazing Management - Is Cell Grazing the Answer?

1996 ◽  
Vol 18 (2) ◽  
pp. 327 ◽  
Author(s):  
JM Earl ◽  
CE Jones
Keyword(s):  
Ground Cover ◽  
Dry Weight ◽  
Grazing Pressure ◽  
Individual Plant ◽  
South Wales ◽  
Continuous Grazing ◽  
Adverse Environmental Conditions ◽  
The Stability ◽  
A Site

With any grazing method, the grazing pressure applied to an individual plant is a site, stock density and time dependent variable and the diet selection hierarchy of grazing animals is to the disadvantage of the most palatable and actively growing pasture components. The greater the differences in palatability and abundance among the components of a sward, and the lower the stock density, the greater the variation in the grazing pressure exerted. These effects are heightened when animals are set-stocked under adverse environmental conditions. This paper reports the comparative effects of cell grazing and continuous grazing on pasture composition on three properties on the Northern Tablelands of New South Wales. The basal diameters, relative frequency and contribution to dry weight of the most desirablelpalatable species at each site were found to remain constant or to increase under cell grazing, while declining significantly under continuous stocking. The converse was true for the least palatable components of the pasture, which declined significantly under cell grazing but changed little under continuous grazing. Percentage ground cover was significantly higher after two years of cell grazing than under continuous grazing. These changes in pasture composition may have long-term benefits with respect to erosion control, nutrient cycling, hydrological function and the stability of animal production at the cell grazed sites.

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