Adaptation of a soil heterotrophic respiration model to an agricultural soil.
Adaptation of a soil heterotrophic respiration model to an agricultural soil.
Buysse P.
1, Le Dantec V.
2, Sagnier C.
2, Aubinet M.
11
Unité de Physique des Biosystèmes, Faculté Universitaire des Sciences Agronomiques de Gembloux, Belgium
2Centre d’Etudes Spatiales de la BIOsphère, Toulouse, France
Objectives of this work:
To adapt a model describing soil heterotrophic respiration, derived from the Century model, to an agricultural soil situated at the Carbo-Europe site of Lonzée (Hesbaye region) in Belgium.
To highlight the main parameters of the model in order to define further steps of investigation and to improve its adjustment on experimental data.
Further goal:
To integrate the present model as a sub routine in a larger model of soil respiration, which will include a heterotrophic respiration component, an autotrophic component and a soil CO2diffusion submodel (Fig. 1).
This soil respiration model:
Will be applied to agricultural soils at an ecosystem scale. Will be as mechanistic as possible and use a daily time step. Will be validated on experimental measurements.
Could be used to compare soil CO2production resulting from different crop management
methods and different culture types. Fig. 1 : Outline of the larger model which will be set up.
The present soil heterotrophic respiration model:
Is derived from the Century model.
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1. Introduction
2. Model description
3. Results
H
ETEROTROPHIC RESPIRATIONS
OIL RESPIRATION MODELA
UTOTROPHIC RESPIRATIONS
OILCO
2 DIFFUSIONLower soil layer (30cm+)
Soil surface layer
Upper soil layer (0-30cm)
Above-ground crop residues Below-ground crop residues Temperature Humidity Decomposition constant (Kx) Soil texture factor (Qx) Soil humidity factor (Aw) Soil temperature factor (At) Pool carbon content (Cx)
Carbon pools:
3 in the soil surface layer (soil surface residues (metabolic/structural C), microbial pool)
5 in each soil layer (Soil residues (metabolic/structural C), microbial pool and active, slow and passive pools) Inputs:
Daily meteorological inputs from automatic measurements (Temperature, Soil moisture content) in each soil layer Residue input frequency: once a cultural year (at harvest)
Fig. 2: Inputs (in green) and layers of the soil heterotrophic respiration model
x x x x
K
Q
Aw
At
C
F
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Carbon flows between pools:Literature survey for a first approach of model parameterisation:
Biochemical features of residues (Lignin, Cellulose and Nitrogen contents, root distribution in the soil) For Sugar beet, Winter wheat and Potato crops
Large variability of the values
Lack of information concerning Sugar beet and Potato crops Soil characteristics of loamy soils
Other parameters: e.g. temperature at which the respiratory activity of micro-organisms is maximum
An insight of the results which can be expected from the model:
Fig. 3 shows the evolution of modeled soil heterotrophic respiration (Rh) during a 4-year period for two residue input scenarios : residue inputs at harvest (blue line, « harv ») and constant daily residue inputs (red line, « daily »). At this stage, the following results are only qualitative
Fig. 3: Evolution of modeled soil heterotrophic respiration during a 4-year period, using meteorological data of this period and wheat biochemical parameters. Crop residues are added to the soil at harvest (blue line) or every day (red line).
Averaged Rh over the 4-year period: Rh harv= 0,87 gC m-2j-1
Rh daily= 0,88 gC m-2j-1
Maximum Rh over the 4-year period: Rh harv= 4,67 gC m-2j-1
Rh daily= 1,95 gC m-2j-1
Sharp increase of modeled Rh when all crop residues are added at harvest
It would be interesting to compare with other scenarios of crop residue inputs
There is a need to better characterise the different parameters
0 0,5 1 1,5 2 2,5 3 3,5 4 4,5 5 0 200 400 600 800 1000 1200 1400 1600 Time (days) R e s p ir a ti o n r a te ( g C m -2 j -1) 0,8 1 1,2 T e m p era tu re f a c to r [-] 0 0,2 0,4 0,6 0,8 1 1,2 0 10 20 30 40 50 Soil moisture content [%Vol]
S o il h u m id it y f a c to r [-]
Respiration fluxes:Parts of Fx, which are function of biochemical characteristics of residues and soil clay content.
Results of the sensitivity analysis:
line) or every day (red line).
CONTACT PERSON: Pauline Buysse – FRS-FNRS Research fellow
Unit of Biosystem Physics – Gembloux Agricultural University – Belgium
buysse.p@fsagx.ac.be
Acknowledgements: This research is funded by the FRS-FNRS, Belgium
Parameters Sensitivity (S) [-] Tb 0,587 MBR 0,361 Litfall 0,351 h -0,304 Hu2 -0,064 Lignrl 0,036 Lignroot 0,033 Nroot -0,031 Nlit -0,026 Lignlit 0,026 Lignll 0,024 Hu1 0,005 H2O30 0,000 Long term Parameters Sensitivity (S) [-] Tb 0,134 Litfall 0,104 MBR 0,085 h -0,069 Hu2 -0,024 Nlit -0,021 Lignlit 0,021 Nroot -0,019 Lignroot 0,019 Lignrl 0,019 Lignll 0,017 Hu1 0,005 H2O30 0,000 Short term Tb, h: Parameters of the temperature responseMBR, Litfall: Quantities of below-ground and above-ground crop residues respectively Hu1, Hu2: Parameters of the humidity response H2O30: Water quantity which percolates under 30cm depth
Biochemical parameters
