General Overview


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This report is the result of the use of the Python 3.4 package Sympy (for symbolic mathematics), as means to translate published models to a common language. It was created by Holger Metzler (Orcid ID: 0000-0002-8239-1601) on 10/03/2016, and was last modified on lm.

About the model

The model depicted in this document considers soil organic matter decomposition. It was originally described by Parton, Schimel, Cole, & Ojima (1987).

Abstract

We analyzed climatic and textural controls of soil organic C and N for soils of the U.S. Great Plains. We used a model of soil organic matter (SOM) quantity and composition to simulate steady-state organic matter levels for 24 grassland locations in the Great Plains. The model was able to simulate the effects of climatic gradients on SOM and productivity. Soil texture was also a major control over organic matter dynamics. The model adequately predicted aboveground plant production and soil C and N levels across soil textures (sandy, medium, and fine); however, the model tended to overestimate soil C and N levels for fine textured soil by 10 to 15%. The impact of grazing on the system was simulated and showed that steady-state soil C and N levels were sensitive to the grazing intensity, with soil C and N levels decreasing with increased grazing rates. Regional trends in SOM can be predicted using four site-specific variables, temperature, moisture, soil texture, and plant lignin content. Nitrogen inputs must also be known. Grazing intensity during soil development is also a significant control over steady-state levels of SOM, and since few data are available on presettlement grazing, some uncertainty is inherent in the model predictions.

Keywords

differential equations, time variant

Principles

mass balance, substrate dependence of decomposition, heterogeneity of speed of decay, internal transformations of organic matter, environmental variability effects

Available parameter values

Information on given parameter sets
Abbreviation Description
Set 1 original values without effects of temperature and soil moisture

Available initial values

Information on given sets of initial values
Abbreviation Description
IV 1 original values without effects of temperature and soil moisture

State Variables

The following table contains the available information regarding this section:

Information on State Variables
Name Description Values

IV 1
\(C_{1}\) structural soil surface litter pool \(100\)
\(C_{2}\) metabolic soil surface litter pool \(200\)
\(C_{3}\) structural soil litter pool -
\(C_{4}\) metabolic soil litter pool -
\(C_{5}\) active soil organic matter pool -
\(C_{6}\) slow soil organic matter pool -
\(C_{7}\) passive soil organic matter pool -

Maximum Decomposition Rates

The following table contains the available information regarding this section:

Information on Maximum Decomposition Rates
Name Description Type Values

Set 1
\(K_{1}\) maximum decomposition rate of structural soil surface litter parameter \(0.076\)
\(K_{2}\) maximum decomposition rate of metabolic soil surface litter parameter \(0.28\)
\(K_{3}\) maximum decomposition rate of structural soil litter parameter \(0.094\)
\(K_{4}\) maximum decomposition rate of metabolic soil litter parameter \(0.35\)
\(K_{5}\) maximum decomposition rate of active soil organic matter parameter \(0.14\)
\(K_{6}\) maximum decomposition rate of slow soil organic matter parameter \(0.0038\)
\(K_{7}\) maximum decomposition rate of passive organic matter parameter \(0.00013\)

Decomposition Rates

The following table contains the available information regarding this section:

Information on Decomposition Rates
Name Description Expressions Values

Set 1
\(k_{1}\) decomposition rate of structural soil surface litter \(k_{1}=K_{1}\,\operatorname{exp}\left(- 3\,Ls\right)\) -
\(k_{3}\) decomposition rate of structural soil litter \(k_{3}=K_{3}\,\operatorname{exp}\left(- 3\,Ls\right)\) -
\(k_{5}\) decomposition rate of active soil organic matter \(k_{5}=K_{5}\,\left(1-0.75\,Tx\right)\) -

Additional Parameters

The following table contains the available information regarding this section:

Information on Additional Parameters
Name Description Type Values

Set 1
\(LN\) lignin-to-nitrogen ratio parameter -
\(Ls\) fraction of structural material that is lignin parameter -
\(Tx\) silt and clay fraction of the soil parameter -
\(A_{l}\) lignin fraction that is composed in structural pools (equals Ls?) parameter -

Auxiliary Variables

The following table contains the available information regarding this section:

Information on Auxiliary Variables
Name Description Expressions Values

Set 1
\(E_{s}\) fraction of carbon lost as CO\(_2\) when active soil organic matter is decomposed and stabilized into slow organic matter \(E_{s}=0.85-0.68\,Tx\) -
\(F_{m}\) fraction of incoming metabolic litter \(F_{m}=0.85-0.018\,LN\) -
\(F_{s}\) fraction of incoming structural litter \(F_{s}=1-F_{m}\) -

Input Components

The following table contains the available information regarding this section:

Information on Input Components
Name Description Type Values

Set 1
\(J_{1}\) organic matter input to surface parameter -
\(J_{2}\) organic matter input to soil parameter -

Transfer Coefficients

The following table contains the available information regarding this section:

Information on Transfer Coefficients
Name Description Expressions Values

Set 1
\(\alpha_{51}\) flux coefficient from strucutral soil surface litter pool to active soil organic matter pool \(\alpha_{51}=0.55\,\left(1-A_{l}\right)\) -
\(\alpha_{53}\) flux coefficient from strucutral soil litter pool to active soil organic matter pool \(\alpha_{53}=0.45\,\left(1-A_{l}\right)\) -
\(\alpha_{61}\) flux coefficient from strucutral soil surface litter pool to slow soil organic matter pool \(\alpha_{61}=0.7\,A_{l}\) -
\(\alpha_{63}\) flux coefficient from strucutral soil litter pool to slow soil organic matter pool \(\alpha_{63}=\alpha_{61}\) -
\(\alpha_{65}\) flux coefficient from strucutral soil surface litter pool to slow soil organic matter pool \(\alpha_{65}=1-E_{s}-0.004\) -

Environmental Coefficients

The following table contains the available information regarding this section:

Information on Environmental Coefficients
Name Description Type Values

Set 1
\(f_{T}\) function of temperature variable -
\(f_{W}\) function of soil moisture variable -

Components

The following table contains the available information regarding this section:

Information on Components
Name Description Expressions
\(C\) carbon content \(C=\left[\begin{matrix}C_{1}\\C_{2}\\C_{3}\\C_{4}\\C_{5}\\C_{6}\\C_{7}\end{matrix}\right]\)
\(I\) input vector \(I=\left[\begin{matrix}F_{s}\cdot J_{1}\\F_{m}\cdot J_{1}\\F_{s}\cdot J_{2}\\F_{m}\cdot J_{2}\\0\\0\\0\end{matrix}\right]\)
\(\xi\) environmental effects multiplier (DEFAG) \(\xi=f_{T}\,f_{W}\)
\(A\) decomposition operator \(A=\left[\begin{matrix}- k_{1} & 0 & 0 & 0 & 0 & 0 & 0\\0 & - K_{2} & 0 & 0 & 0 & 0 & 0\\0 & 0 & - k_{3} & 0 & 0 & 0 & 0\\0 & 0 & 0 & - K_{4} & 0 & 0 & 0\\\alpha_{51}\cdot k_{1} & 0.45\cdot K_{2} &\alpha_{53}\cdot k_{3} & 0.45\cdot K_{4} & - k_{5} & 0.42\cdot K_{6} & 0.45\cdot K_{7}\\\alpha_{61}\cdot k_{1} & 0 &\alpha_{63}\cdot k_{3} & 0 &\alpha_{65}\cdot k_{5} & - K_{6} & 0\\0 & 0 & 0 & 0 & 0.004\cdot k_{5} & 0.03\cdot K_{6} & - K_{7}\end{matrix}\right]\)
\(f_{s}\) the right hand side of the ode \(f_{s}=I+\xi\,A\,C\)

Pool model representation

Flux description

Figure 1
Figure 1: Pool model representation

Input fluxes

\(C_{1}: J_{1}\cdot\left(0.018\cdot LN + 0.15\right)\)
\(C_{2}: J_{1}\cdot\left(- 0.018\cdot LN + 0.85\right)\)
\(C_{3}: J_{2}\cdot\left(0.018\cdot LN + 0.15\right)\)
\(C_{4}: J_{2}\cdot\left(- 0.018\cdot LN + 0.85\right)\)

Output fluxes

\(C_{1}: C_{1}\cdot K_{1}\cdot f_{T}\cdot f_{W}\cdot\left(- 0.15\cdot A_{l} + 0.45\right)\cdot e^{- 3\cdot Ls}\)
\(C_{2}: 0.55\cdot C_{2}\cdot K_{2}\cdot f_{T}\cdot f_{W}\)
\(C_{3}: C_{3}\cdot K_{3}\cdot f_{T}\cdot f_{W}\cdot\left(- 0.25\cdot A_{l} + 0.55\right)\cdot e^{- 3\cdot Ls}\)
\(C_{4}: 0.55\cdot C_{4}\cdot K_{4}\cdot f_{T}\cdot f_{W}\)
\(C_{5}: C_{5}\cdot K_{5}\cdot f_{T}\cdot f_{W}\cdot\left(0.68\cdot Tx - 0.85\right)\cdot\left(0.75\cdot Tx - 1\right)\)
\(C_{6}: 0.55\cdot C_{6}\cdot K_{6}\cdot f_{T}\cdot f_{W}\)
\(C_{7}: 0.55\cdot C_{7}\cdot K_{7}\cdot f_{T}\cdot f_{W}\)

Internal fluxes

\(C_{1} > C_{5}: - 0.55\cdot C_{1}\cdot K_{1}\cdot f_{T}\cdot f_{W}\cdot\left(A_{l} - 1\right)\cdot e^{- 3\cdot Ls}\)
\(C_{1} > C_{6}: 0.7\cdot A_{l}\cdot C_{1}\cdot K_{1}\cdot f_{T}\cdot f_{W}\cdot e^{- 3\cdot Ls}\)
\(C_{2} > C_{5}: 0.45\cdot C_{2}\cdot K_{2}\cdot f_{T}\cdot f_{W}\)
\(C_{3} > C_{5}: - 0.45\cdot C_{3}\cdot K_{3}\cdot f_{T}\cdot f_{W}\cdot\left(A_{l} - 1\right)\cdot e^{- 3\cdot Ls}\)
\(C_{3} > C_{6}: 0.7\cdot A_{l}\cdot C_{3}\cdot K_{3}\cdot f_{T}\cdot f_{W}\cdot e^{- 3\cdot Ls}\)
\(C_{4} > C_{5}: 0.45\cdot C_{4}\cdot K_{4}\cdot f_{T}\cdot f_{W}\)
\(C_{5} > C_{6}: C_{5}\cdot K_{5}\cdot f_{T}\cdot f_{W}\cdot\left(- 0.51\cdot Tx^{2} + 0.5705\cdot Tx + 0.146\right)\)
\(C_{5} > C_{7}: C_{5}\cdot K_{5}\cdot f_{T}\cdot f_{W}\cdot\left(- 0.003\cdot Tx + 0.004\right)\)
\(C_{6} > C_{5}: 0.42\cdot C_{6}\cdot K_{6}\cdot f_{T}\cdot f_{W}\)
\(C_{6} > C_{7}: 0.03\cdot C_{6}\cdot K_{6}\cdot f_{T}\cdot f_{W}\)
\(C_{7} > C_{5}: 0.45\cdot C_{7}\cdot K_{7}\cdot f_{T}\cdot f_{W}\)

The right hand side of the ODE

\(\left[\begin{matrix}- C_{1}\cdot K_{1}\cdot f_{T}\cdot f_{W}\cdot e^{- 3\cdot Ls} + J_{1}\cdot\left(0.018\cdot LN + 0.15\right)\\- C_{2}\cdot K_{2}\cdot f_{T}\cdot f_{W} + J_{1}\cdot\left(- 0.018\cdot LN + 0.85\right)\\- C_{3}\cdot K_{3}\cdot f_{T}\cdot f_{W}\cdot e^{- 3\cdot Ls} + J_{2}\cdot\left(0.018\cdot LN + 0.15\right)\\- C_{4}\cdot K_{4}\cdot f_{T}\cdot f_{W} + J_{2}\cdot\left(- 0.018\cdot LN + 0.85\right)\\C_{1}\cdot K_{1}\cdot f_{T}\cdot f_{W}\cdot\left(- 0.55\cdot A_{l} + 0.55\right)\cdot e^{- 3\cdot Ls} + 0.45\cdot C_{2}\cdot K_{2}\cdot f_{T}\cdot f_{W} + C_{3}\cdot K_{3}\cdot f_{T}\cdot f_{W}\cdot\left(- 0.45\cdot A_{l} + 0.45\right)\cdot e^{- 3\cdot Ls} + 0.45\cdot C_{4}\cdot K_{4}\cdot f_{T}\cdot f_{W} - C_{5}\cdot K_{5}\cdot f_{T}\cdot f_{W}\cdot\left(- 0.75\cdot Tx + 1\right) + 0.42\cdot C_{6}\cdot K_{6}\cdot f_{T}\cdot f_{W} + 0.45\cdot C_{7}\cdot K_{7}\cdot f_{T}\cdot f_{W}\\0.7\cdot A_{l}\cdot C_{1}\cdot K_{1}\cdot f_{T}\cdot f_{W}\cdot e^{- 3\cdot Ls} + 0.7\cdot A_{l}\cdot C_{3}\cdot K_{3}\cdot f_{T}\cdot f_{W}\cdot e^{- 3\cdot Ls} + C_{5}\cdot K_{5}\cdot f_{T}\cdot f_{W}\cdot\left(- 0.75\cdot Tx + 1\right)\cdot\left(0.68\cdot Tx + 0.146\right) - C_{6}\cdot K_{6}\cdot f_{T}\cdot f_{W}\\0.004\cdot C_{5}\cdot K_{5}\cdot f_{T}\cdot f_{W}\cdot\left(- 0.75\cdot Tx + 1\right) + 0.03\cdot C_{6}\cdot K_{6}\cdot f_{T}\cdot f_{W} - C_{7}\cdot K_{7}\cdot f_{T}\cdot f_{W}\end{matrix}\right]\)

The Jacobian (derivative of the ODE w.r.t. state variables)

\(\left[\begin{matrix}- K_{1}\cdot f_{T}\cdot f_{W}\cdot e^{- 3\cdot Ls} & 0 & 0 & 0 & 0 & 0 & 0\\0 & - K_{2}\cdot f_{T}\cdot f_{W} & 0 & 0 & 0 & 0 & 0\\0 & 0 & - K_{3}\cdot f_{T}\cdot f_{W}\cdot e^{- 3\cdot Ls} & 0 & 0 & 0 & 0\\0 & 0 & 0 & - K_{4}\cdot f_{T}\cdot f_{W} & 0 & 0 & 0\\K_{1}\cdot f_{T}\cdot f_{W}\cdot\left(- 0.55\cdot A_{l} + 0.55\right)\cdot e^{- 3\cdot Ls} & 0.45\cdot K_{2}\cdot f_{T}\cdot f_{W} & K_{3}\cdot f_{T}\cdot f_{W}\cdot\left(- 0.45\cdot A_{l} + 0.45\right)\cdot e^{- 3\cdot Ls} & 0.45\cdot K_{4}\cdot f_{T}\cdot f_{W} & - K_{5}\cdot f_{T}\cdot f_{W}\cdot\left(- 0.75\cdot Tx + 1\right) & 0.42\cdot K_{6}\cdot f_{T}\cdot f_{W} & 0.45\cdot K_{7}\cdot f_{T}\cdot f_{W}\\0.7\cdot A_{l}\cdot K_{1}\cdot f_{T}\cdot f_{W}\cdot e^{- 3\cdot Ls} & 0 & 0.7\cdot A_{l}\cdot K_{3}\cdot f_{T}\cdot f_{W}\cdot e^{- 3\cdot Ls} & 0 & K_{5}\cdot f_{T}\cdot f_{W}\cdot\left(- 0.75\cdot Tx + 1\right)\cdot\left(0.68\cdot Tx + 0.146\right) & - K_{6}\cdot f_{T}\cdot f_{W} & 0\\0 & 0 & 0 & 0 & 0.004\cdot K_{5}\cdot f_{T}\cdot f_{W}\cdot\left(- 0.75\cdot Tx + 1\right) & 0.03\cdot K_{6}\cdot f_{T}\cdot f_{W} & - K_{7}\cdot f_{T}\cdot f_{W}\end{matrix}\right]\)

Steady state formulas

\(C_{1} = \frac{0.006\cdot J_{1}\cdot e^{3.0\cdot Ls}}{K_{1}\cdot f_{T}\cdot f_{W}}\cdot\left(3.0\cdot LN + 25.0\right)\)
\(C_{2} = -\frac{0.002\cdot J_{1}\cdot\left(9.0\cdot LN - 425.0\right)}{K_{2}\cdot f_{T}\cdot f_{W}}\)
\(C_{3} = \frac{0.006\cdot J_{2}\cdot e^{3.0\cdot Ls}}{K_{3}\cdot f_{T}\cdot f_{W}}\cdot\left(3.0\cdot LN + 25.0\right)\)
\(C_{4} = -\frac{0.002\cdot J_{2}\cdot\left(9.0\cdot LN - 425.0\right)}{K_{4}\cdot f_{T}\cdot f_{W}}\)
\(C_{5} = \frac{1}{K_{5}\cdot f_{T}\cdot f_{W}\cdot\left(884340.0\cdot Tx^{2} - 3983847.0\cdot Tx + 3739636.0\right)}\cdot\left(- 17751.6\cdot A_{l}\cdot J_{1}\cdot LN - 147930.0\cdot A_{l}\cdot J_{1} - 10551.6\cdot A_{l}\cdot J_{2}\cdot LN - 87930.0\cdot A_{l}\cdot J_{2} + 7200.0\cdot J_{1}\cdot LN + 1860000.0\cdot J_{1} + 1800000.0\cdot J_{2}\right)\)
\(C_{6} = \frac{1}{K_{6}\cdot f_{T}\cdot f_{W}\cdot\left(294780.0\cdot Tx - 934909.0\right)}\cdot\left(6732.0\cdot A_{l}\cdot J_{1}\cdot LN\cdot Tx - 11131.92\cdot A_{l}\cdot J_{1}\cdot LN + 56100.0\cdot A_{l}\cdot J_{1}\cdot Tx - 92766.0\cdot A_{l}\cdot J_{1} + 5508.0\cdot A_{l}\cdot J_{2}\cdot LN\cdot Tx - 11394.72\cdot A_{l}\cdot J_{2}\cdot LN + 45900.0\cdot A_{l}\cdot J_{2}\cdot Tx - 94956.0\cdot A_{l}\cdot J_{2} - 1224.0\cdot J_{1}\cdot LN\cdot Tx - 262.8\cdot J_{1}\cdot LN - 316200.0\cdot J_{1}\cdot Tx - 67890.0\cdot J_{1} - 306000.0\cdot J_{2}\cdot Tx - 65700.0\cdot J_{2}\right)\)
\(C_{7} = \frac{1}{K_{7}\cdot f_{T}\cdot f_{W}\cdot\left(294780.0\cdot Tx - 934909.0\right)}\cdot\left(201.96\cdot A_{l}\cdot J_{1}\cdot LN\cdot Tx - 316.206\cdot A_{l}\cdot J_{1}\cdot LN + 1683.0\cdot A_{l}\cdot J_{1}\cdot Tx - 2635.05\cdot A_{l}\cdot J_{1} + 165.24\cdot A_{l}\cdot J_{2}\cdot LN\cdot Tx - 331.29\cdot A_{l}\cdot J_{2}\cdot LN + 1377.0\cdot A_{l}\cdot J_{2}\cdot Tx - 2760.75\cdot A_{l}\cdot J_{2} - 36.72\cdot J_{1}\cdot LN\cdot Tx - 15.084\cdot J_{1}\cdot LN - 9486.0\cdot J_{1}\cdot Tx - 3896.7\cdot J_{1} - 9180.0\cdot J_{2}\cdot Tx - 3771.0\cdot J_{2}\right)\)

Steady states (potentially incomplete), according jacobian eigenvalues, damping ratio

Parameter set: Set 1

\(C_1: \frac{0.0789473684210526\cdot J_{1}}{f_{T}\cdot f_{W}}\cdot\left(3.0\cdot LN + 25.0\right)\cdot e^{3.0\cdot Ls}\), \(C_2: -\frac{0.00714285714285714\cdot J_{1}}{f_{T}\cdot f_{W}}\cdot\left(9.0\cdot LN - 425.0\right)\), \(C_3: \frac{0.0638297872340425\cdot J_{2}}{f_{T}\cdot f_{W}}\cdot\left(3.0\cdot LN + 25.0\right)\cdot e^{3.0\cdot Ls}\), \(C_4: -\frac{0.00571428571428571\cdot J_{2}}{f_{T}\cdot f_{W}}\cdot\left(9.0\cdot LN - 425.0\right)\), \(C_5: -\frac{1}{f_{T}\cdot f_{W}\cdot\left(884340.0\cdot Tx^{2} - 3983847.0\cdot Tx + 3739636.0\right)}\cdot\left(126797.142857143\cdot A_{l}\cdot J_{1}\cdot LN + 1056642.85714286\cdot A_{l}\cdot J_{1} + 75368.5714285714\cdot A_{l}\cdot J_{2}\cdot LN + 628071.428571429\cdot A_{l}\cdot J_{2} - 51428.5714285714\cdot J_{1}\cdot LN - 13285714.2857143\cdot J_{1} - 12857142.8571429\cdot J_{2}\right)\), \(C_6: \frac{1}{f_{T}\cdot f_{W}\cdot\left(294780.0\cdot Tx - 934909.0\right)}\cdot\left(1771578.94736842\cdot A_{l}\cdot J_{1}\cdot LN\cdot Tx - 2929452.63157895\cdot A_{l}\cdot J_{1}\cdot LN + 14763157.8947368\cdot A_{l}\cdot J_{1}\cdot Tx - 24412105.2631579\cdot A_{l}\cdot J_{1} + 1449473.68421053\cdot A_{l}\cdot J_{2}\cdot LN\cdot Tx - 2998610.52631579\cdot A_{l}\cdot J_{2}\cdot LN + 12078947.3684211\cdot A_{l}\cdot J_{2}\cdot Tx - 24988421.0526316\cdot A_{l}\cdot J_{2} - 322105.263157895\cdot J_{1}\cdot LN\cdot Tx - 69157.8947368421\cdot J_{1}\cdot LN - 83210526.3157895\cdot J_{1}\cdot Tx - 17865789.4736842\cdot J_{1} - 80526315.7894737\cdot J_{2}\cdot Tx - 17289473.6842105\cdot J_{2}\right)\), \(C_7: \frac{1}{f_{T}\cdot f_{W}\cdot\left(294780.0\cdot Tx - 934909.0\right)}\cdot\left(1553538.46153846\cdot A_{l}\cdot J_{1}\cdot LN\cdot Tx - 2432353.84615385\cdot A_{l}\cdot J_{1}\cdot LN + 12946153.8461538\cdot A_{l}\cdot J_{1}\cdot Tx - 20269615.3846154\cdot A_{l}\cdot J_{1} + 1271076.92307692\cdot A_{l}\cdot J_{2}\cdot LN\cdot Tx - 2548384.61538462\cdot A_{l}\cdot J_{2}\cdot LN + 10592307.6923077\cdot A_{l}\cdot J_{2}\cdot Tx - 21236538.4615385\cdot A_{l}\cdot J_{2} - 282461.538461538\cdot J_{1}\cdot LN\cdot Tx - 116030.769230769\cdot J_{1}\cdot LN - 72969230.7692308\cdot J_{1}\cdot Tx - 29974615.3846154\cdot J_{1} - 70615384.6153846\cdot J_{2}\cdot Tx - 29007692.3076923\cdot J_{2}\right)\)

\(\lambda_{1}: - 0.076\cdot f_{T}\cdot f_{W}\cdot e^{- 3\cdot Ls}\)
\(\lambda_{2}: - 0.35\cdot f_{T}\cdot f_{W}\)
\(\lambda_{3}: - 0.094\cdot f_{T}\cdot f_{W}\cdot e^{- 3\cdot Ls}\)
\(\lambda_{4}: 0.035\cdot Tx\cdot f_{T}\cdot f_{W} - 0.04798\cdot f_{T}\cdot f_{W} +\frac{\left(-0.5 + 0.866\cdot i\right)\cdot\left(3.798\cdot 10^{-5}\cdot Tx^{2}\cdot f_{T}^{2}\cdot f_{W}^{2} - 0.00018\cdot Tx\cdot f_{T}^{2}\cdot f_{W}^{2} + 0.0001727\cdot f_{T}^{2}\cdot f_{W}^{2} - 0.1111\cdot\left(- 0.105\cdot Tx\cdot f_{T}\cdot f_{W} + 0.1439\cdot f_{T}\cdot f_{W}\right)^{2}\right)}{\left(7.645\cdot 10^{-9}\cdot Tx^{2}\cdot f_{T}^{3}\cdot f_{W}^{3} - 3.444\cdot 10^{-8}\cdot Tx\cdot f_{T}^{3}\cdot f_{W}^{3} + 3.233\cdot 10^{-8}\cdot f_{T}^{3}\cdot f_{W}^{3} + 0.03704\cdot\left(- 0.105\cdot Tx\cdot f_{T}\cdot f_{W} + 0.1439\cdot f_{T}\cdot f_{W}\right)^{3} - 0.1667\cdot\left(- 0.105\cdot Tx\cdot f_{T}\cdot f_{W} + 0.1439\cdot f_{T}\cdot f_{W}\right)\cdot\left(0.000114\cdot Tx^{2}\cdot f_{T}^{2}\cdot f_{W}^{2} - 0.0005401\cdot Tx\cdot f_{T}^{2}\cdot f_{W}^{2} + 0.000518\cdot f_{T}^{2}\cdot f_{W}^{2}\right) +\left(\left(3.798\cdot 10^{-5}\cdot Tx^{2}\cdot f_{T}^{2}\cdot f_{W}^{2} - 0.00018\cdot Tx\cdot f_{T}^{2}\cdot f_{W}^{2} + 0.0001727\cdot f_{T}^{2}\cdot f_{W}^{2} - 0.1111\cdot\left(- 0.105\cdot Tx\cdot f_{T}\cdot f_{W} + 0.1439\cdot f_{T}\cdot f_{W}\right)^{2}\right)^{3} + 0.25\cdot\left(1.529\cdot 10^{-8}\cdot Tx^{2}\cdot f_{T}^{3}\cdot f_{W}^{3} - 6.888\cdot 10^{-8}\cdot Tx\cdot f_{T}^{3}\cdot f_{W}^{3} + 6.466\cdot 10^{-8}\cdot f_{T}^{3}\cdot f_{W}^{3} + 0.07407\cdot\left(- 0.105\cdot Tx\cdot f_{T}\cdot f_{W} + 0.1439\cdot f_{T}\cdot f_{W}\right)^{3} - 0.3333\cdot\left(- 0.105\cdot Tx\cdot f_{T}\cdot f_{W} + 0.1439\cdot f_{T}\cdot f_{W}\right)\cdot\left(0.000114\cdot Tx^{2}\cdot f_{T}^{2}\cdot f_{W}^{2} - 0.0005401\cdot Tx\cdot f_{T}^{2}\cdot f_{W}^{2} + 0.000518\cdot f_{T}^{2}\cdot f_{W}^{2}\right)\right)^{2}\right)^{0.5}\right)^{0.3333}} -\left(-0.5 - 0.866\cdot i\right)\cdot\left(7.645\cdot 10^{-9}\cdot Tx^{2}\cdot f_{T}^{3}\cdot f_{W}^{3} - 3.444\cdot 10^{-8}\cdot Tx\cdot f_{T}^{3}\cdot f_{W}^{3} + 3.233\cdot 10^{-8}\cdot f_{T}^{3}\cdot f_{W}^{3} + 0.03704\cdot\left(- 0.105\cdot Tx\cdot f_{T}\cdot f_{W} + 0.1439\cdot f_{T}\cdot f_{W}\right)^{3} - 0.1667\cdot\left(- 0.105\cdot Tx\cdot f_{T}\cdot f_{W} + 0.1439\cdot f_{T}\cdot f_{W}\right)\cdot\left(0.000114\cdot Tx^{2}\cdot f_{T}^{2}\cdot f_{W}^{2} - 0.0005401\cdot Tx\cdot f_{T}^{2}\cdot f_{W}^{2} + 0.000518\cdot f_{T}^{2}\cdot f_{W}^{2}\right) +\left(\left(3.798\cdot 10^{-5}\cdot Tx^{2}\cdot f_{T}^{2}\cdot f_{W}^{2} - 0.00018\cdot Tx\cdot f_{T}^{2}\cdot f_{W}^{2} + 0.0001727\cdot f_{T}^{2}\cdot f_{W}^{2} - 0.1111\cdot\left(- 0.105\cdot Tx\cdot f_{T}\cdot f_{W} + 0.1439\cdot f_{T}\cdot f_{W}\right)^{2}\right)^{3} + 0.25\cdot\left(1.529\cdot 10^{-8}\cdot Tx^{2}\cdot f_{T}^{3}\cdot f_{W}^{3} - 6.888\cdot 10^{-8}\cdot Tx\cdot f_{T}^{3}\cdot f_{W}^{3} + 6.466\cdot 10^{-8}\cdot f_{T}^{3}\cdot f_{W}^{3} + 0.07407\cdot\left(- 0.105\cdot Tx\cdot f_{T}\cdot f_{W} + 0.1439\cdot f_{T}\cdot f_{W}\right)^{3} - 0.3333\cdot\left(- 0.105\cdot Tx\cdot f_{T}\cdot f_{W} + 0.1439\cdot f_{T}\cdot f_{W}\right)\cdot\left(0.000114\cdot Tx^{2}\cdot f_{T}^{2}\cdot f_{W}^{2} - 0.0005401\cdot Tx\cdot f_{T}^{2}\cdot f_{W}^{2} + 0.000518\cdot f_{T}^{2}\cdot f_{W}^{2}\right)\right)^{2}\right)^{0.5}\right)^{0.3333}\)
\(\lambda_{5}: - 0.28\cdot f_{T}\cdot f_{W}\)
\(\lambda_{6}: 0.035\cdot Tx\cdot f_{T}\cdot f_{W} - 0.04798\cdot f_{T}\cdot f_{W} +\frac{\left(-0.5 - 0.866\cdot i\right)\cdot\left(3.798\cdot 10^{-5}\cdot Tx^{2}\cdot f_{T}^{2}\cdot f_{W}^{2} - 0.00018\cdot Tx\cdot f_{T}^{2}\cdot f_{W}^{2} + 0.0001727\cdot f_{T}^{2}\cdot f_{W}^{2} - 0.1111\cdot\left(- 0.105\cdot Tx\cdot f_{T}\cdot f_{W} + 0.1439\cdot f_{T}\cdot f_{W}\right)^{2}\right)}{\left(7.645\cdot 10^{-9}\cdot Tx^{2}\cdot f_{T}^{3}\cdot f_{W}^{3} - 3.444\cdot 10^{-8}\cdot Tx\cdot f_{T}^{3}\cdot f_{W}^{3} + 3.233\cdot 10^{-8}\cdot f_{T}^{3}\cdot f_{W}^{3} + 0.03704\cdot\left(- 0.105\cdot Tx\cdot f_{T}\cdot f_{W} + 0.1439\cdot f_{T}\cdot f_{W}\right)^{3} - 0.1667\cdot\left(- 0.105\cdot Tx\cdot f_{T}\cdot f_{W} + 0.1439\cdot f_{T}\cdot f_{W}\right)\cdot\left(0.000114\cdot Tx^{2}\cdot f_{T}^{2}\cdot f_{W}^{2} - 0.0005401\cdot Tx\cdot f_{T}^{2}\cdot f_{W}^{2} + 0.000518\cdot f_{T}^{2}\cdot f_{W}^{2}\right) +\left(\left(3.798\cdot 10^{-5}\cdot Tx^{2}\cdot f_{T}^{2}\cdot f_{W}^{2} - 0.00018\cdot Tx\cdot f_{T}^{2}\cdot f_{W}^{2} + 0.0001727\cdot f_{T}^{2}\cdot f_{W}^{2} - 0.1111\cdot\left(- 0.105\cdot Tx\cdot f_{T}\cdot f_{W} + 0.1439\cdot f_{T}\cdot f_{W}\right)^{2}\right)^{3} + 0.25\cdot\left(1.529\cdot 10^{-8}\cdot Tx^{2}\cdot f_{T}^{3}\cdot f_{W}^{3} - 6.888\cdot 10^{-8}\cdot Tx\cdot f_{T}^{3}\cdot f_{W}^{3} + 6.466\cdot 10^{-8}\cdot f_{T}^{3}\cdot f_{W}^{3} + 0.07407\cdot\left(- 0.105\cdot Tx\cdot f_{T}\cdot f_{W} + 0.1439\cdot f_{T}\cdot f_{W}\right)^{3} - 0.3333\cdot\left(- 0.105\cdot Tx\cdot f_{T}\cdot f_{W} + 0.1439\cdot f_{T}\cdot f_{W}\right)\cdot\left(0.000114\cdot Tx^{2}\cdot f_{T}^{2}\cdot f_{W}^{2} - 0.0005401\cdot Tx\cdot f_{T}^{2}\cdot f_{W}^{2} + 0.000518\cdot f_{T}^{2}\cdot f_{W}^{2}\right)\right)^{2}\right)^{0.5}\right)^{0.3333}} -\left(-0.5 + 0.866\cdot i\right)\cdot\left(7.645\cdot 10^{-9}\cdot Tx^{2}\cdot f_{T}^{3}\cdot f_{W}^{3} - 3.444\cdot 10^{-8}\cdot Tx\cdot f_{T}^{3}\cdot f_{W}^{3} + 3.233\cdot 10^{-8}\cdot f_{T}^{3}\cdot f_{W}^{3} + 0.03704\cdot\left(- 0.105\cdot Tx\cdot f_{T}\cdot f_{W} + 0.1439\cdot f_{T}\cdot f_{W}\right)^{3} - 0.1667\cdot\left(- 0.105\cdot Tx\cdot f_{T}\cdot f_{W} + 0.1439\cdot f_{T}\cdot f_{W}\right)\cdot\left(0.000114\cdot Tx^{2}\cdot f_{T}^{2}\cdot f_{W}^{2} - 0.0005401\cdot Tx\cdot f_{T}^{2}\cdot f_{W}^{2} + 0.000518\cdot f_{T}^{2}\cdot f_{W}^{2}\right) +\left(\left(3.798\cdot 10^{-5}\cdot Tx^{2}\cdot f_{T}^{2}\cdot f_{W}^{2} - 0.00018\cdot Tx\cdot f_{T}^{2}\cdot f_{W}^{2} + 0.0001727\cdot f_{T}^{2}\cdot f_{W}^{2} - 0.1111\cdot\left(- 0.105\cdot Tx\cdot f_{T}\cdot f_{W} + 0.1439\cdot f_{T}\cdot f_{W}\right)^{2}\right)^{3} + 0.25\cdot\left(1.529\cdot 10^{-8}\cdot Tx^{2}\cdot f_{T}^{3}\cdot f_{W}^{3} - 6.888\cdot 10^{-8}\cdot Tx\cdot f_{T}^{3}\cdot f_{W}^{3} + 6.466\cdot 10^{-8}\cdot f_{T}^{3}\cdot f_{W}^{3} + 0.07407\cdot\left(- 0.105\cdot Tx\cdot f_{T}\cdot f_{W} + 0.1439\cdot f_{T}\cdot f_{W}\right)^{3} - 0.3333\cdot\left(- 0.105\cdot Tx\cdot f_{T}\cdot f_{W} + 0.1439\cdot f_{T}\cdot f_{W}\right)\cdot\left(0.000114\cdot Tx^{2}\cdot f_{T}^{2}\cdot f_{W}^{2} - 0.0005401\cdot Tx\cdot f_{T}^{2}\cdot f_{W}^{2} + 0.000518\cdot f_{T}^{2}\cdot f_{W}^{2}\right)\right)^{2}\right)^{0.5}\right)^{0.3333}\)
\(\lambda_{7}: 0.035\cdot Tx\cdot f_{T}\cdot f_{W} - 0.04798\cdot f_{T}\cdot f_{W} +\frac{3.798\cdot 10^{-5}\cdot Tx^{2}\cdot f_{T}^{2}\cdot f_{W}^{2} - 0.00018\cdot Tx\cdot f_{T}^{2}\cdot f_{W}^{2} + 0.0001727\cdot f_{T}^{2}\cdot f_{W}^{2} - 0.1111\cdot\left(- 0.105\cdot Tx\cdot f_{T}\cdot f_{W} + 0.1439\cdot f_{T}\cdot f_{W}\right)^{2}}{\left(7.645\cdot 10^{-9}\cdot Tx^{2}\cdot f_{T}^{3}\cdot f_{W}^{3} - 3.444\cdot 10^{-8}\cdot Tx\cdot f_{T}^{3}\cdot f_{W}^{3} + 3.233\cdot 10^{-8}\cdot f_{T}^{3}\cdot f_{W}^{3} + 0.03704\cdot\left(- 0.105\cdot Tx\cdot f_{T}\cdot f_{W} + 0.1439\cdot f_{T}\cdot f_{W}\right)^{3} - 0.1667\cdot\left(- 0.105\cdot Tx\cdot f_{T}\cdot f_{W} + 0.1439\cdot f_{T}\cdot f_{W}\right)\cdot\left(0.000114\cdot Tx^{2}\cdot f_{T}^{2}\cdot f_{W}^{2} - 0.0005401\cdot Tx\cdot f_{T}^{2}\cdot f_{W}^{2} + 0.000518\cdot f_{T}^{2}\cdot f_{W}^{2}\right) +\left(\left(3.798\cdot 10^{-5}\cdot Tx^{2}\cdot f_{T}^{2}\cdot f_{W}^{2} - 0.00018\cdot Tx\cdot f_{T}^{2}\cdot f_{W}^{2} + 0.0001727\cdot f_{T}^{2}\cdot f_{W}^{2} - 0.1111\cdot\left(- 0.105\cdot Tx\cdot f_{T}\cdot f_{W} + 0.1439\cdot f_{T}\cdot f_{W}\right)^{2}\right)^{3} + 0.25\cdot\left(1.529\cdot 10^{-8}\cdot Tx^{2}\cdot f_{T}^{3}\cdot f_{W}^{3} - 6.888\cdot 10^{-8}\cdot Tx\cdot f_{T}^{3}\cdot f_{W}^{3} + 6.466\cdot 10^{-8}\cdot f_{T}^{3}\cdot f_{W}^{3} + 0.07407\cdot\left(- 0.105\cdot Tx\cdot f_{T}\cdot f_{W} + 0.1439\cdot f_{T}\cdot f_{W}\right)^{3} - 0.3333\cdot\left(- 0.105\cdot Tx\cdot f_{T}\cdot f_{W} + 0.1439\cdot f_{T}\cdot f_{W}\right)\cdot\left(0.000114\cdot Tx^{2}\cdot f_{T}^{2}\cdot f_{W}^{2} - 0.0005401\cdot Tx\cdot f_{T}^{2}\cdot f_{W}^{2} + 0.000518\cdot f_{T}^{2}\cdot f_{W}^{2}\right)\right)^{2}\right)^{0.5}\right)^{0.3333}} -\left(7.645\cdot 10^{-9}\cdot Tx^{2}\cdot f_{T}^{3}\cdot f_{W}^{3} - 3.444\cdot 10^{-8}\cdot Tx\cdot f_{T}^{3}\cdot f_{W}^{3} + 3.233\cdot 10^{-8}\cdot f_{T}^{3}\cdot f_{W}^{3} + 0.03704\cdot\left(- 0.105\cdot Tx\cdot f_{T}\cdot f_{W} + 0.1439\cdot f_{T}\cdot f_{W}\right)^{3} - 0.1667\cdot\left(- 0.105\cdot Tx\cdot f_{T}\cdot f_{W} + 0.1439\cdot f_{T}\cdot f_{W}\right)\cdot\left(0.000114\cdot Tx^{2}\cdot f_{T}^{2}\cdot f_{W}^{2} - 0.0005401\cdot Tx\cdot f_{T}^{2}\cdot f_{W}^{2} + 0.000518\cdot f_{T}^{2}\cdot f_{W}^{2}\right) +\left(\left(3.798\cdot 10^{-5}\cdot Tx^{2}\cdot f_{T}^{2}\cdot f_{W}^{2} - 0.00018\cdot Tx\cdot f_{T}^{2}\cdot f_{W}^{2} + 0.0001727\cdot f_{T}^{2}\cdot f_{W}^{2} - 0.1111\cdot\left(- 0.105\cdot Tx\cdot f_{T}\cdot f_{W} + 0.1439\cdot f_{T}\cdot f_{W}\right)^{2}\right)^{3} + 0.25\cdot\left(1.529\cdot 10^{-8}\cdot Tx^{2}\cdot f_{T}^{3}\cdot f_{W}^{3} - 6.888\cdot 10^{-8}\cdot Tx\cdot f_{T}^{3}\cdot f_{W}^{3} + 6.466\cdot 10^{-8}\cdot f_{T}^{3}\cdot f_{W}^{3} + 0.07407\cdot\left(- 0.105\cdot Tx\cdot f_{T}\cdot f_{W} + 0.1439\cdot f_{T}\cdot f_{W}\right)^{3} - 0.3333\cdot\left(- 0.105\cdot Tx\cdot f_{T}\cdot f_{W} + 0.1439\cdot f_{T}\cdot f_{W}\right)\cdot\left(0.000114\cdot Tx^{2}\cdot f_{T}^{2}\cdot f_{W}^{2} - 0.0005401\cdot Tx\cdot f_{T}^{2}\cdot f_{W}^{2} + 0.000518\cdot f_{T}^{2}\cdot f_{W}^{2}\right)\right)^{2}\right)^{0.5}\right)^{0.3333}\)

References

Parton, W. J., Schimel, D. S., Cole, C. V., & Ojima, D. S. (1987). Analysis of factors controlling soil organic matter levels in Great Plains grasslands. Soil Sci. Soc. Am. J., 51(5), 1173–1179. http://doi.org/10.2136/sssaj1987.03615995005100050015x