Parameter Descriptions

State Variables

These values evolve during a model run and are stored in the respective fields in the [ModvegeSite] instance that was run.

• BM Standing biomass in kg DM per ha.
• BMG Standing green biomass (kg DM / ha).
• cBM Cumulativeley grown biomass (kg DM / ha).
• dBM Daily grown biomass (kg DM / ha).
• hvBM Cumulative harvested biomass (kg DM / ha).
• OMD Organic matter digestibility (kg / kg).
• OMDG OMD of green matter (kg / kg).
• ST Temperature sum in degree Celsius days.
• REP Reproductive function. Gives the fraction of growth that is assigned to reproductive growth. The remainder goes into vegetative growth. Dimensionless.
• PGRO Potential growth in kg DM / ha.
• GRO Effective growth in kg DM / ha.
• LAI Leaf area index, accounting for the proportion of light intercepted by the sward. Dimensionless.
• LAIGV LAI of green vegetative biomass. Dimensionless.
• AET Actual evapotranspiration in mm.
• WR Water reserves in mm.
• ENV Function representing environmental effects on growth. Acts as a multiplicative factor. Dimensionless.
• ENVfPAR Part of ENV due to strength of incident radiation. Dimensionless.
• ENVfT Part of ENV due to temperature. Dimensionless.
• ENVfW Part of ENV due to water limitation. Dimensionless.

Initial conditions

• AgeGV Age of green vegetative matter in degree Celsius days.

• AgeGR Age of green reproductive matter in degree Celsius days.

• AgeDV Age of dead vegetative matter in degree Celsius days.

• AgeDR Age of dead reproductive matter in degree Celsius days.

• BMGV biomass of GV (kg DM per ha).

• BMGR biomass of GR (kg DM per ha).

• BMDV biomass of DV (kg DM per ha).

• BMDR biomass of DR (kg DM per ha).

• BMDR biomass of DR (kg DM per ha).

• SENG senescence of GV (kg DM per ha).

• SENG senescence of GR (kg DM per ha).

• ABSG abscission of DV (kg DM per ha).

• ABSG abscission of DR (kg DM per ha).

• ST thermal time (degree days).

• cBM cumulative total biomass (kg per ha).

Model parameters

• LON geographic longitude of site in degree.

• LAT geographic latitude of site in degree.

• ELV geographic elevation of site in m.a.s.l.

• WHC water-holding capacity of site in mm.

• NI site nutritional index (dimensionless).

• RUEmax maximum radiuation use efficiency in g DM per MJ.

• w_FGA relative weight of functional group A.

• w_FGB relative weight of functional group B.

• w_FGC relative weight of functional group C.

• w_FGD relative weight of functional group D.

• sigmaGV rate of GV respirative biomass loss (dimensionless).

• sigmaGR rate of GR respirative biomass loss (dimensionless).

• T0 photosynthesis activation temperature (degree C).

• T1 photosynthesis plateau temperature (degree C).

• T2 photosynthesis max temperature (degree C).

• KGV basic senescence rate GV (dimensionless).

• KGR basic senescence rate GR (dimensionless).

• KlGV basic abscission rate GV (dimensionless).

• KlGR basic abscission rate GR (dimensionless).

• maxOMDDV organic matter digestibility in gram per gram DV.

• minOMDDR organic matter digestibility in gram per gram DR.

• CO2_growth_factor strength of effect of CO2 concentration on growth. See parameter b in [fCO2_growth_mod()].

• crop_coefficient multiplicative factor K_c by which reference evapotranspiration ET₀ has to be multiplied to get the crop evapotranspiration ET_c: ET_c = K_c ET₀

• senescence_cap fraction c_s of GRO to which SEN is limited: SEN_i^max = c_s GRO_i for i in GV, GR. Makes it less likely for grass population to die out. Can be set to large values in order to effectively disable senescence capping.

• stubble_height float. Minimum height the grass can assume. The biomass will not fall below that height. This effectively presents a simple model of plant reserves.

• SGS_method string. Choice of method to determine the start of the growing season. Can be either "MTD" for the multicriterial thermal definition (see [start_of_growing_season_mtd()]) or "simple" for a commonly used approach as described in [start_of_growing_season()]).

Functional group parameters

• SLA Specific Leaf Area in m² per g.

• pcLAM Percentage of laminae (number between 0 and 1).

• ST1 Temperature sum in degree Celsiues days after which the seasonality function SEA starts to decrease from its maximum plateau. See also [SEA()].

• ST2 Temperature sum in degree Celsiues days after which the seasonality function SEA has decreased back to its minimum value. See also [SEA()].

• maxSEA Maximum value of the seasonality function [SEA()]

• minSEA Minimum value of the seasonality function [SEA()]. Usually, minSEA = 1 - (maxSEA - 1).

• maxOMDGV Maximum organic matter digestability for green vegetative matter in arbitrary units.

• minOMDGV Minimum organic matter digestability for green vegetative matter in arbitrary units.

• maxOMDGR Maximum organic matter digestability for green reproductive matter in arbitrary units.

• minOMDGR Minimum organic matter digestability for green reproductive matter in arbitrary units.

• BDGV Bulk density of green vegetative dry matter in g per m³.

• BDDV Bulk density of dead vegetative dry matter in g per m³.

• BDGR Bulk density of green reproductive dry matter in g per m³.

• BDDR Bulk density of dead reproductive dry matter in g per m³.

• fg_parameter_names Vector of strings of the variable names of all vegetation parameters governed by functional group composition.

Weather variables

• DOY day of year in given year

• Ta average temperature of given day (Celsius).

• precip precipitation in millimeter per day.

• PAR photosynthetically active radiation in MJ/m². Can be calculated from average sunlight irradiance SRad in J/s/m² as: PAR = SRad * 0.47 * 24 * 60 * 60 / 1e6

• ET0 evapotranspiration in mm.