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The ICBM model. i = (annual) input, Young C (Y) = young soil carbon, Old C (O) = old soil carbon, k Y = fraction of Y that decomposes (per year), k O = fraction of O that decomposes (per year), h =
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A simple soil carbon model, the Introductory Carbon Balance Model (ICBM), is useful for projecting soil C dynamics in temperate and tropical land-use systems. A spreadsheet-based version of ICBM is presented, with an emphasis on African and short-and long term projections under variable conditions (climate, crops, soil). ICBM has two compartments,...
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... or pools, “Young” ( Y ) and “Old” ( O ) soil carbon. ICBM has five parameters: i, k Y , h, k O , and r e (Table 1 and Figure 1). The “humification coefficient” ( h ) controls the fraction of Y that enters O and ( 1-h ) then represents the fraction of the outflow from Y that becomes CO 2 – C. Parameter r e summarizes all external influence (mainly climate) on the decomposition rates of Y and O . Note that r e only affects decomposition rates; r e does not influence i or h (Figure 1) (Andrén and Kätterer, 1997) for complete list of equations as well as strategies for estimating parameter values. The model was originally calibrated using data from a Swedish long-term agricultural field experiment with various amendments (manure, cereal straw and sewage sludge, etc) but also a black fallow kept since 1956 (Kirchmann et al., 2004). The model has been successfully applied to agricultural field data from Sweden (Karlsson et al., 2003), European field trials, Western and Eastern Canadian agricultural regions (Bolinder et al., 2006, 2007a, 2008; Campbell et al., 2007) and Norwegian arable land (Kynding et al., 2012) has been adapted to sub-Saharan African conditions (Andrén et al., 2007). ICBM has also been expanded to a larger family of related model structures, including more carbon pools and also nitrogen dynamics. The basic idea behind ICBM is to use an analytically solved, five- parameter two-component model for interactive calculations of soil C balances in a 30-years perspective using a spreadsheet program. The reasons for this simple approach are: 1. Easy and rapid to use and understand with usually only three parameters to „play‟ with using guessed or „rule -of- thumb‟ parameter values. All parameter values used can be reported in ...
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... or pools, “Young” ( Y ) and “Old” ( O ) soil carbon. ICBM has five parameters: i, k Y , h, k O , and r e (Table 1 and Figure 1). The “humification coefficient” ( h ) controls the fraction of Y that enters O and ( 1-h ) then represents the fraction of the outflow from Y that becomes CO 2 – C. Parameter r e summarizes all external influence (mainly climate) on the decomposition rates of Y and O . Note that r e only affects decomposition rates; r e does not influence i or h (Figure 1) (Andrén and Kätterer, 1997) for complete list of equations as well as strategies for estimating parameter values. The model was originally calibrated using data from a Swedish long-term agricultural field experiment with various amendments (manure, cereal straw and sewage sludge, etc) but also a black fallow kept since 1956 (Kirchmann et al., 2004). The model has been successfully applied to agricultural field data from Sweden (Karlsson et al., 2003), European field trials, Western and Eastern Canadian agricultural regions (Bolinder et al., 2006, 2007a, 2008; Campbell et al., 2007) and Norwegian arable land (Kynding et al., 2012) has been adapted to sub-Saharan African conditions (Andrén et al., 2007). ICBM has also been expanded to a larger family of related model structures, including more carbon pools and also nitrogen dynamics. The basic idea behind ICBM is to use an analytically solved, five- parameter two-component model for interactive calculations of soil C balances in a 30-years perspective using a spreadsheet program. The reasons for this simple approach are: 1. Easy and rapid to use and understand with usually only three parameters to „play‟ with using guessed or „rule -of- thumb‟ parameter values. All parameter values used can be reported in ...
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Quantifying soil CO2 and CH4 emissions and C balance under dryland cropping systems in arid and semiarid regions is needed to understand their contributions to climate change. The objective of this study was to examine the effect of crop rotation and N fertilization rate on soil CO2 and CH4 fluxes and C balance under dryland farming from 2012 to 20...
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... This study modified the ICBM (Introductory Carbon Balance Model) and applied it to provide simulation results of GHG emitted from Tidal Flat over the period of 2017 and 2047. Since ICBM has been regarded as one of the excellent models to simulate carbon dynamics in soil, it has been extensively applied to estimate the amount of carbon stored in agricultural soils over a long period to establish the efficient and effective soil management plans [16][17][18]. The main objectives of this study were to improve the ICBM, to optimize the model parameters in accordance with a tidal flat area, and to evaluate the applicability of the model to predict the amount of carbon stored in the sediment and GHG emissions (CO 2 and CH 4 ) over 30 years from 2017 to 2047, using data from the vegetated tidal flat and BTF areas in Ganghwa, Korea. ...
Since coastal wetlands have been severely degraded and polluted by human activities, they
have increasingly become a significant source of greenhouse gases (GHGs), so understanding the
characteristics of their emissions is critical for devising future climate change mitigation strategies.
This study modified a model based on carbon balance to forecast carbon stored and CO2, CH4
emissions in four types of typical tidal flats—Phragmites australis (PA), Spartina alterniflora (SA),
Suaeda japonica (SJ), and Bare Tidal Flat (BTF) in Korea’s Ganghwa province from 2017 to 2047. The
model was built using biomass data from salt plant species collected in different locations. The
results indicate that the total annual simulated flow of CH4 increased over time in all four areas,
most notably in SA, while CO2 remained relatively stable. The mean CO2 and CH4 fluxes in the
four types of representative tidal flats were in the range of 0.03 to 19.1 mg m2 d1 and 0.007 to
5.23 mg m2 d1, respectively, across all seasons. Besides, the results indicate that the amount of
carbon accumulated in the top soil increases linearly over time in nearly all areas studied, ranging
from 0.01 to 0.13 (kgC m2 yr1). In general, the study provides a model for Korean tidal flats that
incorporates carbon storage and GHG emissions in the intertidal zone in order to develop potential
GHG reduction scenarios.
... Given the many degrees of freedom in the calibration (in particular the C input estimation parameters), we believe that model calibration already has enough flexibility to represent the results. Moreover, the determination of the old pool kinetics in the original ICBM version is tied to real data from a long-term bare fallow and is considered robust enough to be generalizable (Andrén et al., 2008(Andrén et al., , 2012Menichetti et al., 2019). The posterior distributions of the kinetics of the young pools were similar to the prior distributions. ...
Agroforestry is a form of productive land management that combines trees or bushes with annual crops or pasture, and it can bring benefits in terms of food security and increased carbon (C) sequestration compared with conventional agriculture. But agroforestry as a structured form of agronomic management is relatively new compared with well-established and widespread agronomic systems. Consequently, there is a lack of data and few models of soil organic carbon (SOC) have been developed specifically for agroforestry systems. Also, agroforestry SOC sequestration data measured in field experiments are often reported only as average linear sequestration rates over the study period. This approach, equivalent to zero-order kinetics, makes it difficult to compare results since, in reality, SOC sequestration rates are variable over time and change depending on the duration of measurements. Sequestration rates are also strongly dependent on former C stocks in the soil, further hampering comparisons between agroforestry systems established on different former land uses.
To describe the SOC stocks variation over time, researchers often employ models considering at least first-order kinetics. This approach can take care of the two above mentioned issues, considering both the variation of the sequestration over time and the effect of previous land use. However, the variability of agroforestry systems makes applying these models more challenging compared to simpler agricultural systems. To deal with this problem we propose to use detailed uncertainty estimation methods, based on stochastic calibrations that can deal with broad probability distributions.
To do so, we adapted a first-order compartmental SOC model to agroforestry systems. It was calibrated within a Bayesian framework on global agroforestry data. Compared to linear coefficients, the model (ICBMAgroforestry) estimates equilibrium SOC stocks of different agroforestry systems probabilistically and is providing uncertainty bounds. These values are independent of initial land use and time duration of the experiments. ICBMAgroforestry can be used for rapid assessment and comparison of the maximum potential SOC stocks for different agroforestry systems and climatic zones. In this study, we could use our approach to estimate the global maximum C that can be sequestered by agroforestry systems at equilibrium, which ranged between 156 and 263 Mg C ha⁻¹ on average, above but comparable with similar estimates for simpler agricultural systems.
... Southwest and North are less suitable for grain production, and the arable lands have been used for forage production or as pastures for decades, resulting in high initial SOC. The initial C in topsoil is crucial for estimating C balance as a high initial SOC content will lead to a decrease, and a low initial SOC will lead to an increase (Andrén et al., 2015). Hence, the estimated C loss from farms in Southwest and North is a result of high initial SOC. ...
... Hence, the estimated C loss from farms in Southwest and North is a result of high initial SOC. As the soil C content is difficult to measure, Andrén et al. (2015) suggested to modify the initial SOC if the changes between samplings are unrealistic. However, in the present study there is only a single estimate of the SOC content and modifying the initial SOC is not possible. ...
Emission intensities from beef production vary both among production systems (countries) and farms within a country depending upon use of natural resources and management practices. A whole-farm model developed for Norwegian suckler cow herds, HolosNorBeef, was used to estimate GHG emissions from 27 commercial beef farms in Norway with Angus, Hereford, and Charolais cattle. HolosNorBeef considers direct emissions of methane (CH4), nitrous oxide (N2O) and carbon dioxide (CO2) from on-farm livestock production and indirect N2O and CO2 emissions associated with inputs used on the farm. The corresponding soil carbon (C) emissions are estimated using the Introductory Carbon Balance Model (ICBM). The farms were distributed across Norway with varying climate and natural resource bases. The estimated emission intensities ranged from 22.5 to 45.2 kg CO2 equivalents (eq) (kg carcass)⁻¹. Enteric CH4 was the largest source, accounting for 44% of the total GHG emissions on average, dependent on dry matter intake (DMI). Soil C was the largest source of variation between individual farms and accounted for 6% of the emissions on average. Variation in GHG intensity among farms was reduced and farms within region East, Mid and North re-ranked in terms of emission intensities when soil C was excluded. Ignoring soil C, estimated emission intensities ranged from 21.5 to 34.1 kg CO2 eq (kg carcass)⁻¹. High C loss from farms with high initial soil organic carbon (SOC) content warrants further examination of the C balance of permanent grasslands as a potential mitigation option for beef production systems.
... (1) and (2) in the original ICBM calibration (Andrén and Kätterer, 1997) aggregates all the influences on SOC from soil type and climate. It was originally conceived as a constant, but it also has been used as a response variable connected with climatic and edaphic factors (Andrén et al., 2012). We decided to consider r according to the following equation: ...
Soil organic carbon (SOC) dynamics result from different interacting processes and controls on spatial scales from sub-aggregate to pedon to the whole ecosystem. These complex dynamics are translated into models as abundant degrees of freedom. This high number of not directly measurable variables and, on the other hand, very limited data at disposal result in equifinality and parameter uncertainty. Carbon radioisotope measurements are a proxy for SOC age both at annual to decadal (bomb peak based) and centennial to millennial timescales (radio decay based), and thus can be used in addition to total organic C for constraining SOC models. By considering this additional information, uncertainties in model structure and parameters may be reduced. To test this hypothesis we studied SOC dynamics and their defining kinetic parameters in the Zürich Organic Fertilization Experiment (ZOFE) experiment, a > 60-year-old controlled cropland experiment in Switzerland, by utilizing SOC and SO14C time series. To represent different processes we applied five model structures, all stemming from a simple mother model (Introductory Carbon Balance Model – ICBM): (I) two decomposing pools, (II) an inert pool added, (III) three decomposing pools, (IV) two decomposing pools with a substrate control feedback on decomposition, (V) as IV but with also an inert pool. These structures were extended to explicitly represent total SOC and 14C pools. The use of different model structures allowed us to explore model structural uncertainty and the impact of 14C on kinetic parameters. We considered parameter uncertainty by calibrating in a formal Bayesian framework. By varying the relative importance of total SOC and SO14C data in the calibration, we could quantify the effect of the information from these two data streams on estimated model parameters. The weighing of the two data streams was crucial for determining model outcomes, and we suggest including it in future modeling efforts whenever SO14C data are available. The measurements and all model structures indicated a dramatic decline in SOC in the ZOFE experiment after an initial land use change in 1949 from grass- to cropland, followed by a constant but smaller decline. According to all structures, the three treatments (control, mineral fertilizer, farmyard manure) we considered were still far from equilibrium. The estimates of mean residence time (MRT) of the C pools defined by our models were sensitive to the consideration of the SO14C data stream. Model structure had a smaller effect on estimated MRT, which ranged between 5.9 ± 0.1 and 4.2 ± 0.1 years and 78.9 ± 0.1 and 98.9 ± 0.1 years for young and old pools, respectively, for structures without substrate interactions. The simplest model structure performed the best according to information criteria, validating the idea that we still lack data for mechanistic SOC models. Although we could not exclude any of the considered processes possibly involved in SOC decomposition, it was not possible to discriminate their relative importance.
... In our study, under agroforestry, the accumulation rate in the top 15 cm was on average 1.2 Mg ha -1 a -1 (95% CI: 0.3 to 2.0) higher and in restrained grazing 0.7 Mg ha -1 a -1 (95% CI: 0.3 to 1.3) higher relative to the traditional control when estimated by the Hodges-Lehmann procedure (Sprent & Smeeton, 2001). The obvious reason for the difference is that the process-based models were developed and validated under temperate conditions and for systems not representative of East Africa (Andrén et al., 2012). In previous studies from Kenya, the often-used soil organic carbon models Century and RothC performed better for monocropping than for intercropping systems common in East-Africa (Kamoni et al., 2007), exemplified by the agroforestry and restrained grazing in the present study. ...
More than half of the cultivation-induced carbon loss from agricultural soils could be restored through improved management. To incentivise carbon sequestration, the potential of improved practices needs to be verified. To date, there is sparse empirical evidence of carbon sequestration through improved practices in East-Africa. Here, we show that agroforestry and restrained grazing had a greater stock of soil carbon than their bordering pair-matched controls, but the difference was less obvious with terracing. The controls were treeless cultivated fields for agroforestry, on slopes not terraced for terracing, and permanent pasture for restrained grazing, representing traditionally managed agricultural practices dominant in the case regions. The gain by the improved management depended on the carbon stocks in the control plots. Agroforestry for 6-20 years led to 11.4 Mg ha(-1) and restrained grazing for 6-17 years to 9.6 Mg ha(-1) greater median soil carbon stock compared with the traditional management. The empirical estimates are higher than previous process-model-based estimates and indicate that Ethiopian agriculture has greater potential to sequester carbon in soil than previously estimated. This article is protected by copyright. All rights reserved.
... It is important to note when reading this 2008 paper that even though the actual ICBM model is simple (Figure 4), calculations of climatic influence, soil type effects, and how much carbon is input from plants each year can be complex. However, general knowledge concerning climate, plant productivity, etc. can be used to generate model inputs when detailed data are not available, and the actual modeling can be done interactively using an Excel spreadsheet (Andrén et al., 2012). Thus, ICBM was developed as a minimal approach for calculating soil carbon balances in a 30-year perspective . ...
The recent economic progress in China has stimulated scientific research in sandy lands in Inner Mongolia, where the Institute of Desert Research, Chinese Academy of Sciences (now CAREERI) has a leading position. Economic progress naturally creates financial resources for research, and also a dire need for solutions to emerging environmental problems following development, where wind-blown dust from Inner Mongolia adds to the severe particle air pollution in many Chinese cities. This paper presents selected results and observations made during Chinese–Swedish cooperation projects spanning 25 years. Results and experiences from sandy land research concerning climate, vegetation, root dynamics, soil carbon balances, etc. are briefly presented. The evolution of the Naiman Desertification Research Station, 520 km northeast of Beijing, from 1988 to 2013 is duly noted and commented. An overview of the ICBM soil carbon model concept follows and a few recommendations for future scientific advancement in Chinese arid lands are given.
... The latter two used the ICBMregion concept, as was also used for a regional study in croplands of the USA by Lokupitiya et al. (2012). Furthermore, the ICBM model showed a strong potential under African conditions when an inert C fraction was included and the parameters were adapted to local conditions (Andrén et al., 2012;Juston et al., 2010). ...
Slides from the seminar ”Introduction to SOC modelling”, module of the course ”Carbon Dynamics and Global Change”. University of Basel, Switzerland, 2016.
