Table of Contents

• Initialisation
  • Initialisation from site input
    • Accessing individual items from site input
      • Stone fraction
      • Soil texture
      • Bulk density
      • Carbon and nitrogen content
      • Porosity
      • Van Genuchten parameters
      • Maximum and minimum water filled pore space
      • Field capacity and wilting point
    • Linking/interpretating individual items
      • Soil texture
      • Stone fraction
      • pH value
      • Saturated hydraulic conductivity
      • Bulk density
      • Iron
      • Organic carbon and nitrogen
      • Porosity
      • van Genuchten parameters
      • Minimum and maximum water filled pore space
      • Field capacity and wilting point

Initialisation

Initialization of the global soil state is separated into two parts:

1. Initialization of soil state directly from site input information
2. Initialization of remaining soil state (state variables not directly provided by site input)

Initialisation from site input

Accessing individual items from site input

Stone fraction

For each stratum the following procedure applies for:

1. Take value if provided in the site input
2. If not provided in the site input, use value according to the humus or layer-specific soil type (determined by the clay, sand and silt content in the specific layer, note layer specific soil types are only determined if clay+sand+silt summs up to 1.0. If not, e.g. for peat soils, the soil type that covers the complete soil profile is used as specified in the site input.)

Soil texture

Soil texture includes:

• clay
• sand
• silt

For each stratum the following procedure applies for clay, sand and silt:

1. Take value if provided in the site input
2. If not provided in the site input, use value according to the humus/soil type
3. If the sum of all three fractions is greater than 1.0, all fractions are scaled down to exactly 1.0.

Bulk density

For each stratum the following procedure applies for:

1. Take value if provided in the site input
2. If not provided in the site input, use value according to the humus or layer-specific soil type (determined by the clay, sand and silt content in the specific layer, note layer specific soil types are only determined if clay+sand+silt summs up to 1.0. If not, e.g. for peat soils, the soil type that covers the complete soil profile is used as specified in the site input.)

Carbon and nitrogen content

For each stratum the following procedure applies for:

1. Take value of soil organic carbon content if provided in the site input
2. If soil organic carbon content is not provided in the site input, use humus type specific value for the litter layer. For the soil below the litter layer, if soil organic nitrogen content is provided determine ecosystem-specific C/N ratio to calculate the soil organic carbon content. If soil organic nitrogen content is also not provided, determine a exponential decay function using the soil organic carbon content in 5 and 30 cm soil depth as provided in the site input.
3. Take value of soil organic nitrogen content if provided in the site input
4. If soil organic carbon nitrogen is not provided in the site input, use humus type specific C/N ratio for the litter layer and determine ecosystem-specific C/N ratio for the soil below the litter layer to determine soil organic nitrogen content.

Porosity

For each stratum the following procedure applies for:

1. Take value of porosity if provided in the site input
2. If not explicitly provided, calculate porosity based on soil texture, soil organic carbon content and bulk density.

Van Genuchten parameters

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Maximum and minimum water filled pore space

...

Field capacity and wilting point

...

Linking/interpretating individual items

Soil texture

Soil texture is determined depending on clay, sand and silt content. Only if the sum of these fractions does add up to 1.0, the soil type is determined layer-specifc and used for further gap-filling. Otherwise, the soil type that covers the complete soil profile is used.

Stone fraction

Bulk soil characterization may in- or exclude rocks/stones/gravel depending on different measurement approaches and points of view. While smaller gravel is most likely included in soil samples of, e.g., bulk density, greater stones or rocks are commonly excluded. Within the context of LandscapeDNDC, all soil input refers to the bulk soil excluding rocks/stones/gravel. Accordingly, the stone fraction represents the volumetric sum of rocks/stones/gravel.

pH value

Depending on the model selection, pH may be dynamically calculated (e.g. after urea application). The pH value provided in the site input is interpretated as a mean value that is measured frequently over a longer time period.

Saturated hydraulic conductivity

...

Bulk density

Internally used bulk density \( \rho \) includes bulk density of the soil without stones \( \rho^{\ast} \) and bulk density of stones \( \rho_{min} \):

\( \rho = \rho^{\ast} (1 - x_{stone}) + \rho_{min} x_{stone} \)

Iron

Total iron content is distributed equally to ferric and ferrous iron pools.

Organic carbon and nitrogen

Internally used organic carbon and nitrogen contents include stones:

\( c_{org} = c_{org}^{\ast} (1 - x_{stone}) \frac{\rho}{\rho^{\ast}} \)

Porosity

...

van Genuchten parameters

Minimum and maximum water filled pore space

...

Field capacity and wilting point

...