SoilchemistryDNDC - Denitrification and Decomposition

Table of Contents

• Litter allocation
• Nitrification

The soilchemistry model SoilchemistryDNDC has been developed in order to predict GHG emissions from forest and agricultural ecosystems

Litter allocation

Plant litter is distributed into very labile, labile, and resistant compartments across the soil profile according to its nitrogen content.

Incoming plant is litter is characterized by:

• foliage
• fine roots
• storage organs
• stubble
• above- and belowground wood
• root exsudation
• dung and urine

Nitrification

During the first step of nitrification ( \( NH_4^+ \rightarrow NO_2 \)) some fraction is converted to \( N_2O \) and \( NO \):

\[ \frac{d NO}{dt} = -\psi_{KNO} \cdot \phi_{TM,NO} \cdot \phi_{pH,NO} \cdot \frac{d NH_4}{dt} \\ \frac{d N_2O}{dt} = -\psi_{KN2O} \cdot \phi_{TM, N_2O} \cdot \frac{d NH_4}{dt} \]

The temperature (T) moisture ( \(\theta\)) factor \( \phi_{TM, NO} \) is given by

\[ \phi_{TM,NO} = \frac{1}{\frac{1}{\Psi_{TF\_NUP\_NO1} e^{\frac{T}{\Psi_{TF\_NUP\_NO2}}}} + \frac{1}{1-\frac{\Psi_{M\_FACT\_P1}}{1 + e^{\theta - \Psi_{M\_FACT\_P2}}}}} \]

Temperature moisture dependency of N2O production during nitrification

The pH factor is given by

\[ \phi_{pH,NO} = \Psi_{PH\_FACT\_P2} - \Psi_{PH\_FACT\_P3} \cdot pH \]

The temperature (T) moisture ( \(\theta\)) factor \( \phi_{TM, N_2O} \) is given by

\[ \phi_{TM,N_2O} = \frac{1}{\frac{1}{\Psi_{TF\_NUP\_N2O1} e^{\frac{T}{\Psi_{TF\_NUP\_N2O2}}}} + \frac{1}{1-\frac{\Psi_{M\_FACT\_P3}}{1 + e^{\theta - \Psi_{M\_FACT\_P4}}}}} \]

Temperature moisture dependency of NO production during nitrification