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#include "global.h"

#include "production3pg.h"

#include "resourceunit.h"

#include "species.h"

#include "speciesresponse.h"

#include "model.h"

Production3PG::Production3PG()

{

    mResponse=0;

}

/**

  This is based on the utilizable photosynthetic active radiation.

  @sa http://iland.boku.ac.at/primary+production

  The resulting radiation is MJ/m2       */

inline double Production3PG::calculateUtilizablePAR(const int month) const

{

    // calculate the available radiation

    // there is no production outside of the vegetation period

    if (mResponse->absorbedRadiation()[month]==0.)

        return 0.;

    // see Equation (3)

    // multiplicative approach: responses are averaged one by one and multiplied on a monthly basis

//    double response = mResponse->absorbedRadiation()[month] *

//                      mResponse->vpdResponse()[month] *

//                      mResponse->soilWaterResponse()[month] *

//                      mResponse->tempResponse()[month];

    // minimum approach: for each day the minimum aof vpd, temp, soilwater is calculated, then averaged for each month

    double response = mResponse->absorbedRadiation()[month] *

                      mResponse->minimumResponses()[month];

    return response;

}

/** calculate the alphac (=photosynthetic efficiency) for the given month.

   this is based on a global efficiency, and modified per species.

   epsilon is in gC/MJ Radiation

  */

inline double Production3PG::calculateEpsilon(const int month) const

{

    double epsilon = Model::settings().epsilon; // maximum radiation use efficiency

    epsilon *= mResponse->nitrogenResponse() *

               mResponse->co2Response();

    return epsilon;

}

inline double Production3PG::abovegroundFraction() const

{

    double harsh =  1 - 0.8/(1 + 2.5 * mResponse->nitrogenResponse());

    return harsh;

}

/** calculate the alphac (=photosynthetic efficiency) for given month.

  @sa http://iland.boku.ac.at/primary+production */

double Production3PG::calculate()

{

    Q_ASSERT(mResponse!=0);

    // Radiation: sum over all days of each month with foliage

    double year_raw_gpp = 0.;

    for (int i=0;i<12;i++) {

        mGPP[i] = 0.; mUPAR[i]=0.;

    }

    double utilizable_rad, epsilon;

    // conversion from gC to kg Biomass: C/Biomass=0.5

    const double gC_to_kg_biomass = 2. / 1000.;

    for (int i=0;i<12;i++) {

        utilizable_rad = calculateUtilizablePAR(i); // utilizable radiation of the month times ...

        epsilon = calculateEpsilon(i); // ... photosynthetic efficiency ...

        mUPAR[i] = utilizable_rad ;

        mGPP[i] =utilizable_rad * epsilon * gC_to_kg_biomass; // ... results in GPP of the month kg Biomass/m2 (converted from gC/m2)

        year_raw_gpp += mGPP[i]; // kg Biomass/m2

    }

    // calculate fac

    mRootFraction = 1. - abovegroundFraction();

    // global value set?

    double dbg = GlobalSettings::instance()->settings().paramValue("gpp_per_year",0);

    if (dbg) {

        year_raw_gpp = dbg;

        mRootFraction = 0.4;

    }

    // year GPP/rad: kg Biomass/m2

    mGPPperArea = year_raw_gpp;

    return mGPPperArea; // yearly GPP in kg Biomass/m2

}