ecearth3/sources/lpjg/modules/canexch.cpp

///////////////////////////////////////////////////////////////////////////////////////
/// \file canexch.cpp
/// \brief The canopy exchange module
///
/// Vegetation-atmosphere exchange of H2O and CO2 via
/// production, respiration and evapotranspiration.
///
/// \author Ben Smith
/// $Date: 2013-10-10 10:20:33 +0200 (Thu, 10 Oct 2013) $
///
///////////////////////////////////////////////////////////////////////////////////////

// WHAT SHOULD THIS FILE CONTAIN?
// Module source code files should contain, in this order:
//   (1) a "#include" directive naming the framework header file. The framework header
//       file should define all classes used as arguments to functions in the present
//       module. It may also include declarations of global functions, constants and
//       types, accessible throughout the model code;
//   (2) other #includes, including header files for other modules accessed by the
//       present one;
//   (3) type definitions, constants and file scope global variables for use within
//       the present module only;
//   (4) declarations of functions defined in this file, if needed;
//   (5) definitions of all functions. Functions that are to be accessible to other
//       modules or to the calling framework should be declared in the module header
//       file.
//
// PORTING MODULES BETWEEN FRAMEWORKS:
// Modules should be structured so as to be fully portable between models (frameworks).
// When porting between frameworks, the only change required should normally be in the
// "#include" directive referring to the framework header file.

#include "config.h"
#include "canexch.h"
#include "driver.h"
#include "q10.h"
#include "bvoc.h"
#include "ncompete.h"
#include <assert.h>


// Anonymous namespace for variables with file scope
namespace {

/// leaf nitrogen (kgN/kgC) not associated with photosynthesis
/** (value given by Haxeltine & Prentice 1996) */
const double N0 = 7.15 * 0.001;

// Lookup tables for parameters with Q10 temperature responses

/// lookup table for Q10 temperature response of CO2/O2 specificity ratio
LookupQ10 lookup_tau(0.57, 2600.0);

/// lookup table for Q10 temperature response of Michaelis constant for O2
LookupQ10 lookup_ko(1.2, 3.0e4);

/// lookup table for Q10 temperature response of Michaelis constant for CO2
LookupQ10 lookup_kc(2.1, 30.0);

}

///////////////////////////////////////////////////////////////////////////////////////
// INTERCEPTION

/// Daily loss of water and energy through evaporation of rain or snow intercepted by the vegetation canopy
/** Gerten et al. (2004) Eq 2-4.

  */
void interception(Patch& patch,Climate& climate) {

	// Calculates daily loss of water and energy through evaporation of rainfall
	// intercepted by the vegetation canopy

	double scap; // canopy storage capacity (mm)
	double fwet; // fraction of day that canopy is wet (Kergoat 1996)
	double pet; // potential evapotranspiration (mm)

	pet=climate.eet*PRIESTLEY_TAYLOR;

	// Retrieve Vegetation object
	Vegetation& vegetation=patch.vegetation;

	patch.intercep=0.0;
	if (date.day == 0) {
		for (int d = 0; d < date.year_length(); d++) {
			patch.dintercep[d] = 0.0;
		}
	}

	// Loop through individuals ...

	vegetation.firstobj();
	while (vegetation.isobj) {
		Individual& indiv=vegetation.getobj();

		// For this individual ...

		if (!negligible(pet)) {

			if (indiv.alive) {
				// Storage capacity for precipitation by canopy (point scale)
				scap=climate.prec*min(indiv.lai_indiv_today()*indiv.pft.intc,0.999);

				// Fraction of day that canopy remains wet
				fwet=min(scap/pet,patch.fpc_rescale);

				// Calculate interception by this individual, and increment patch total

				indiv.intercep=fwet*pet*indiv.fpc;
				patch.intercep+=indiv.intercep;
			}
			else {
				indiv.intercep=0.0;
			}
		}
		else {

			indiv.intercep=0.0;
			patch.intercep=0.0;
		}

		// ... on to next individual
		vegetation.nextobj();
	}

	// Calculate net EET for vegetated parts of patch (deducting loss to interception)

	patch.eet_net_veg=max(climate.eet-patch.intercep,0.0);

	// Interception accounting for patch
	patch.aintercep+=patch.intercep;
	patch.mintercep[date.month]+=patch.intercep;
	patch.dintercep[date.day] = patch.intercep;
}


///////////////////////////////////////////////////////////////////////////////////////
// FPAR
// Internal function - not intended to be called by framework

void fpar(Patch& patch) {

	// DESCRIPTION
	// Calculates daily fraction of incoming PAR (FPAR) taken up by individuals in a
	// particular patch over their projective areas, given current leaf phenological
	// status. Calculates PAR and FPAR at top of grass canopy (individual and cohort
	// modes). Calculates fpar assuming leaf-on (phen=1) for all vegetation.
	//
	// Note: In order to compensate for the additional computational cost of
	//       calculating fpar_leafon in cohort/individual mode, the grain of the
	//       integration of FPAR through the canopy has been increased from 1 to 2 m
	//
	// NEW ASSUMPTIONS CONCERNING FPC AND FPAR (Ben Smith 2002-02-20)
	// FPAR = average individual fraction of PAR absorbed on patch basis today,
	//        including effect of current leaf phenology (this differs from previous
	//        versions of LPJ-GUESS in which FPAR was on an FPC basis)
	// FPC =  PFT population (population mode), cohort (cohort mode) or individual
	//        (individual mode) fractional projective cover as a fraction of patch area
	//        (in population mode, corresponds to LPJF variable fpc_grid). Updated
	//        annually based on leaf-out LAI (see function allometry in growth module).
	//        (FPC was previously equal to summed crown area as a fraction of patch
	//        area in cohort/individual mode)
	//
	// Population mode: FPAR on patch (grid cell) area basis assumed to be equal to fpc
	// under full leaf cover; i.e.
	//     (1) fpar        = fpc*phen
	//     (2) fpar_leafon = fpc
	//
	// Individual and cohort modes: FPAR calculated assuming trees shade themselves
	//   and all individuals below them according to the Lambert-Beer law (Prentice
	//   et al 1993, Eqn 27; Monsi & Saeki 1953):
	//     (3) fpar = integral [0-tree height] exp ( -k * plai(z) )
	//   where
	//       k       = extinction coefficient;
	//       plai(z) = summed leaf-area index for leaves of all individuals, above
	//                 canopy depth z, taking account of current phenological status

	const double VSTEP=2.0; // width of vertical layers for canopy-area integration (m)
	const double PHEN_GROWINGSEASON=0.5;
		// minimum expected vegetation leaf-on fraction for growing season

	double plai; // cumulative leaf-area index (LAI) for patch (m2 leaf/m2 ground)
	double plai_leafon;
		// cumulative LAI for patch assuming full leaf cover for all individuals
	double plai_layer; // summed LAI by layer for patch
	double plai_leafon_layer;
		// summed LAI by layer for patch assuming full leaf cover for all individuals
	double plai_grass; // summed LAI for grasses
	double plai_leafon_grass;
		// summed LAI for grasses assuming full leaf cover for all individuals
	double flai; // fraction of total grass LAI represented by a particular grass
	double fpar_layer_top; // FPAR by layer
	double fpar_leafon_layer_top;
		// FPAR by layer assuming full leaf cover for all individuals
	double fpar_layer_bottom;
	double fpar_leafon_layer_bottom;
	double fpar_grass; // FPAR at top of grass canopy
	double fpar_leafon_grass;
		// FPAR at top of grass canopy assuming full leaf cover for all individuals
	double fpar_ff; // FPAR at forest floor (beneath grass canopy)
	double fpar_leafon_ff;
		// FPAR at forest floor assuming full leaf cover for all individuals
	double frac;
		// vertical fraction of layer occupied by crown cylinder(s) of a particular
		// individual or cohort
	double atoh; // term in calculating LAI sum for a given layer
	double height_veg; // maximum vegetation height (m)
	int toplayer; // number of vertical layers of width VSTEP in vegetation (minus 1)
	int layer; // layer number (0=lowest)
	double lowbound; // lower bound of current layer (m)
	double highbound; // upper bound of current layer (m)
	double fpar_min; // minimum FPAR required for grass growth
	double par_grass; // PAR reaching top of grass canopy (J/m2/day)
	double phen_veg; // LAI-weighted mean fractional leaf-out for vegetation
	//variables needed for "S�kes" FPAR scheme
	double fpar_uptake_layer;
	double fpar_uptake_leafon_layer;

	// Obtain reference to Vegetation object
	Vegetation& vegetation=patch.vegetation;

	// And to Climate object
	const Climate& climate = patch.get_climate();

	if (vegmode==POPULATION) {

		// POPULATION MODE

		// Loop through individuals

		vegetation.firstobj();
		while (vegetation.isobj) {
			Individual& indiv=vegetation.getobj();

			// For this individual ...

			indiv.fpar=indiv.fpc_today(); // Eqn 1
			indiv.fpar_leafon=indiv.fpc * indiv.growingseason(); // Eqn 2

			vegetation.nextobj(); // ... on to next individual
		}
	}

	else {

		// INDIVIDUAL OR COHORT MODE

		// Initialise individual FPAR, find maximum height of vegetation, calculate
		// individual LAI given current phenology, calculate summed LAI for grasses

		plai=0.0;
		plai_leafon=0.0;
		plai_grass=0.0;
		plai_leafon_grass=0.0;
		phen_veg=0.0;
		height_veg=0.0;

		// Loop through individuals

		vegetation.firstobj();
		while (vegetation.isobj) {
			Individual& indiv=vegetation.getobj();

			// For this individual ...

			if (indiv.growingseason()) {

				indiv.fpar=0.0;
				indiv.fpar_leafon=0.0;
				if (indiv.height>height_veg) height_veg=indiv.height;
				plai_leafon+=indiv.lai;

				if (indiv.pft.lifeform==GRASS) {
					plai_leafon_grass+=indiv.lai;
					plai_grass+=indiv.lai_today();
				}

				// Accumulate LAI-weighted sum of individual leaf-out fractions
				phen_veg+=indiv.lai_today();
			}

			vegetation.nextobj(); // ... on to next individual
		}

		// Calculate LAI-weighted mean leaf-out fraction for vegetation
		// guess2008 - bugfix - was: if (!negligible(plai))
		if (!negligible(plai_leafon))
			phen_veg/=plai_leafon;
		else
			phen_veg=1.0;

		// Calculate number of layers (minus 1) from ground surface to top of canopy
		toplayer=(int)(height_veg/VSTEP-0.0001);

		// Calculate FPAR by integration from the top of the canopy (Eqn 2)
		plai=0.0;
		plai_leafon=0.0;

		// Set FPAR for bottom of layer above (initially 1 at top of canopy)

		fpar_layer_bottom=1.0;
		fpar_leafon_layer_bottom=1.0;

		for (layer=toplayer;layer>=0;layer--) {

			lowbound=(double)layer*VSTEP;
			highbound=lowbound+VSTEP;

			// FPAR at top of this layer = FPAR at bottom of layer above

			fpar_layer_top=fpar_layer_bottom;
			fpar_leafon_layer_top=fpar_leafon_layer_bottom;

			plai_layer=0.0;
			plai_leafon_layer=0.0;

			// Loop through individuals

			vegetation.firstobj();
			while (vegetation.isobj) {
				Individual& indiv=vegetation.getobj();

				// For this individual ...

				if (indiv.pft.lifeform==TREE) {
					if (indiv.height>lowbound && indiv.boleht<highbound &&
						!negligible(indiv.height-indiv.boleht)) {

						// Calculate vertical fraction of current layer occupied by
						// crown cylinders of this cohort

						frac=1.0;
						if (indiv.height<highbound)
							frac-=(highbound-indiv.height)/VSTEP;
						if (indiv.boleht>lowbound)
							frac-=(indiv.boleht-lowbound)/VSTEP;

						// Calculate summed LAI of this cohort in this layer

						atoh=indiv.lai/(indiv.height-indiv.boleht);
						indiv.lai_leafon_layer=atoh*frac*VSTEP;
						plai_layer+=indiv.lai_leafon_layer*indiv.phen;
						plai_leafon_layer+=indiv.lai_leafon_layer;
					}
					else {
						indiv.lai_layer=0.0;
						indiv.lai_leafon_layer=0.0;
					}
				}

				// ... on to next individual
				vegetation.nextobj();
			}

			// Update cumulative LAI for this layer and above
			plai+=plai_layer;
			plai_leafon+=plai_leafon_layer;

			// Calculate FPAR at bottom of this layer
			// Eqn 27, Prentice et al 1993

			fpar_layer_bottom = lambertbeer(plai);
			fpar_leafon_layer_bottom = lambertbeer(plai_leafon);

			// Total PAR uptake in this layer

			fpar_uptake_layer=fpar_layer_top-fpar_layer_bottom;
			fpar_uptake_leafon_layer=fpar_leafon_layer_top-fpar_leafon_layer_bottom;

			// Partition PAR for this layer among trees,

			vegetation.firstobj();
			while (vegetation.isobj) {
				Individual& indiv=vegetation.getobj();

				// For this individual ...

				if (indiv.pft.lifeform==TREE) {
					if (!negligible(plai_leafon_layer))

						// FPAR partitioned according to the relative amount
						// of leaf area in this layer for this individual

						indiv.fpar_leafon+=fpar_uptake_leafon_layer*
							indiv.lai_leafon_layer/plai_leafon_layer;

					if (!negligible(plai_layer))
						indiv.fpar+=fpar_uptake_layer*
							(indiv.lai_leafon_layer*indiv.phen)/plai_layer;
				}

				// ... on to next individual
				vegetation.nextobj();
			}

		}

		// FPAR reaching grass canopy
		fpar_grass = lambertbeer(plai);
		fpar_leafon_grass = lambertbeer(plai_leafon);

		// Add grass LAI to calculate PAR reaching forest floor
		// BLARP: Order changed Ben 050301 to overcome optimisation bug in pgCC

		//plai+=plai_grass;
		fpar_ff = lambertbeer(plai+plai_grass);
		plai+=plai_grass;

		// Save this
		patch.fpar_ff=fpar_ff;

		plai_leafon+=plai_leafon_grass;
		fpar_leafon_ff = lambertbeer(plai_leafon);

		// FPAR for grass PFTs is difference between relative PAR at top of grass canopy
		// canopy and at forest floor, or lower if FPAR at forest floor below threshold
		// for grass growth. PAR reaching the grass canopy is partitioned among grasses
		// in proportion to their LAI (a somewhat simplified assumption)

		// Loop through individuals

		double fpar_tree_total=0.0;

		vegetation.firstobj();
		while (vegetation.isobj) {
			Individual& indiv=vegetation.getobj();

			// For this individual ...

			if (indiv.pft.lifeform==GRASS) {

				// Calculate minimum FPAR for growth of this grass

				// Fraction of total grass LAI represented by this grass

				if (!negligible(plai_grass))
					flai=indiv.lai_today()/plai_grass;
				else
					flai=1.0;

				if (!negligible(climate.par))
					fpar_min=min(indiv.pft.parff_min/climate.par,1.0);
				else
					fpar_min=1.0;

				indiv.fpar=max(0.0,fpar_grass*flai-max(fpar_ff*flai,fpar_min));

				// Repeat assuming full leaf cover for all individuals

				if (!negligible(plai_leafon_grass))
					flai=indiv.lai/plai_leafon_grass;
				else
					flai=1.0;

				indiv.fpar_leafon=max(0.0,fpar_leafon_grass*flai-
					max(fpar_leafon_ff*flai,fpar_min));
			}

			if (indiv.pft.lifeform==TREE) fpar_tree_total+=indiv.fpar;

			vegetation.nextobj();
		}

		// Save grass canopy FPAR and update mean growing season grass canopy PAR
		// Growing season defined here as days when mean vegetation leaf-on fraction
		// exceeds 50% and we're in the light half of the year (daylength >= 11).
		//
		// The daylength condition was added because sites with evergreens can have
		// a mean vegetation leaf-on fraction over 50% even during polar night.
		// 11 hours was chosen because some sites never reach exactly 12 hours, the
		// exact limit shouldn't matter much.

		patch.fpar_grass=fpar_grass;
		par_grass=fpar_grass*climate.par;

		if (date.day==0) {
			patch.par_grass_mean=0.0;
			patch.nday_growingseason=0;
		}

		if (phen_veg>PHEN_GROWINGSEASON && patch.get_climate().daylength >= 11.0) {
			patch.par_grass_mean+=par_grass;
			patch.nday_growingseason++;
		}

		// Convert from sum to mean on last day of year

		if (date.islastday && date.islastmonth && patch.nday_growingseason) {
			patch.par_grass_mean/=(double)patch.nday_growingseason;
		}
	}
}

double alphaa(const Pft& pft) {

	if (!ECEARTH) {
		// trunk
		if (pft.phenology == CROPGREEN)
			return ifnlim ? ALPHAA_CROP_NLIM : ALPHAA_CROP;
		else
			return ifnlim ? ALPHAA_NLIM : ALPHAA;
	}
	else {
		// EC-Earth - increased _NLIM values
		if (pft.phenology == CROPGREEN)
			return ifnlim ? ALPHAA_CROP_NLIM_ECE : ALPHAA_CROP;
		else
			return ifnlim ? ALPHAA_NLIM_ECE : ALPHAA;
	}
}

/// Non-water stressed rubisco capacity, with or without nitrogen limitation
void vmax(double b, double c1, double c2, double apar, double tscal,
		  double daylength, double temp, double nactive, bool ifnlimvmax, double& vm, double& vmaxnlim, double& nactive_opt) {

	// Calculation of non-water-stressed rubisco capacity assuming leaf nitrogen not
	// limiting (Eqn 11, Haxeltine & Prentice 1996a)
	// Calculation of sigma is based on Eqn 12 (same source)

	double s =  24.0 / daylength * b;
	double sigma = sqrt(max(0., 1. - (c2 - s) / (c2 - THETA * s)));
	vm = 1 / b * CMASS * CQ * c1 / c2 * tscal * apar *
						(2. * THETA * s * (1. - sigma) - s + c2 * sigma);

	// Calculate nitrogen-limited Vmax for current leaf nitrogen
	// Haxeltine & Prentice 1996b Eqn 28

	const double M = 25.0; // corresponds to parameter p in Eqn 28, Haxeltine & Prentice 1996b

	// Conversion factor in calculation of leaf nitrogen: includes conversion of:
	//		- Vm from gC/m2/day to umolC/m2/sec
	//      - nitrogen from mg/m2 to kg/m2

	double CN = 1.0 / (3600 * daylength * CMASS);

	double tfac = exp(-0.0693 * (temp - 25.0));
	double vm_max = nactive / (M * CN * tfac);

	// Calculate optimal leaf nitrogen based on [potential] Vmax (Eqn 28 Haxeltine & Prentice 1996b)
	nactive_opt = M * vm * CN * tfac;

	if (vm > vm_max && ifnlimvmax) {
		vmaxnlim = vm_max / vm;	// Save vmax nitrogen limitation
		vm = vm_max;
	}
	else {
		vmaxnlim = 1.0;
	}
}

/// Total daily gross photosynthesis
/** Calculation of total daily gross photosynthesis and leaf-level net daytime
 *  photosynthesis given degree of stomatal closure (as parameter lambda).
 *  Includes implicit scaling from leaf to plant projective area basis.
 *  Adapted from Farquhar & von Caemmerer (1982) photosynthesis model, as simplified
 *  by Collatz et al (1991), Collatz et al (1992), Haxeltine & Prentice (1996a,b)
 *  and Sitch et al. (2000).
 *
 *  To calculate vmax call w/ daily averages of temperature and par.
 *  Vmax is to be calculated daily and only with lambda == lambda_max.
 *  lambda values greater than lambda_max are forbidden.
 *  In sub-daily mode daylength should be 24 h, to obtain values in daily units.
 *
 *  INPUT PARAMETERS
 *
 *  \param co2        atmospheric ambient CO2 concentration (ppmv)
 *  \param temp       mean air temperature today (deg C)
 *  \param par        total daily photosynthetically-active radiation today (J/m2/day)
 *  \param daylength  day length, must equal 24 in diurnal mode (h)
 *  \param fpar       fraction of PAR absorbed by foliage
 *  \param lambda     ratio of intercellular to ambient partial pressure of CO2
 *  \param pft        Pft object containing the following public members:
 *   - pathway         biochemical pathway for photosynthesis (C3 or C4)
 *   - pstemp_min      approximate low temperature limit for photosynthesis (deg C)
 *   - pstemp_low      approximate lower range of temperature optimum for
 *                     photosynthesis (deg C)
 *   - pstemp_high     approximate upper range of temperature optimum for photosynthesis
 *                     (deg C)
 *   - pstemp_max      maximum temperature limit for photosynthesis (deg C)
 *   - lambda_max      non-water-stressed ratio of intercellular to ambient CO2 pp
 *  \param nactive    nitrogen available for photosynthesis
 *  \param ifnlimvmax whether nitrogen should limit Vmax
 *  \param vm         pre-calculated value of Vmax for this stand for this day if
 *                    available, otherwise calculated
 *
 * OUTPUT PARAMETERS
 *
 * \param result      see documentation of PhotosynthesisResult struct
 */
void photosynthesis(double co2, double temp, double par, double daylength,
                    double fpar, double lambda, const Pft& pft,
                    double nactive, bool ifnlimvmax,
                    PhotosynthesisResult& result, double vm) {

	// NOTE: This function is identical to LPJF subroutine "photosynthesis" except for
	// the formulation of low-temperature inhibition coefficient tscal (tstress; LPJF).
	// The function adopted here draws down metabolic activity in approximately the
	// temperature range pstemp_min-pstemp_low but does not affect photosynthesis
	// at high temperatures.

	// HISTORY
	// Ben Smith 18/1/2001: Tested in comparison to LPJF subroutine "photosynthesis":
	// function showed identical behaviour except at temperatures >= c. 35 deg C where
	// LPJF temperature inhibition function results in lower photosynthesis.

	// Make sure that only two alternative modes are possible:
	//  * daily non-water stressed (forces Vmax calculation)
	//  * with pre-calculated Vmax (sub-daily and water-stressed)
	assert(vm >= 0 || lambda == pft.lambda_max);
	assert(lambda <= pft.lambda_max);

	const double PATMOS = 1e5;	// atmospheric pressure (Pa)

	// No photosynthesis during polar night, outside of temperature range or no RuBisCO activity
	if (negligible(daylength) || negligible(fpar) || temp > pft.pstemp_max || temp < pft.pstemp_min || !vm) {
		result.clear();
		return;
	}

	// Scale fractional PAR absorption at plant projective area level (FPAR) to
	// fractional absorption at leaf level (APAR)
	// Eqn 4, Haxeltine & Prentice 1996a
	double apar = par * fpar * alphaa(pft);
	double b, c1, c2;


	// Calculate temperature-inhibition coefficient
	// This function (tscal) is mathematically identical to function tstress in LPJF.
	// In contrast to earlier versions of modular LPJ and LPJ-GUESS, it includes both
	// high- and low-temperature inhibition.
	double k1 = (pft.pstemp_min+pft.pstemp_low) / 2.0;
	double tscal = (1. - .01*exp(4.6/(pft.pstemp_max-pft.pstemp_high)*(temp-pft.pstemp_high)))/
							(1.0+exp((k1-temp)/(k1-pft.pstemp_min)*4.6));

	if (pft.pathway == C3) 	{			// C3 photosynthesis

		// Calculate CO2 compensation point (partial pressure)
		// Eqn 8, Haxeltine & Prentice 1996a
		double gammastar = PO2 / 2.0 / lookup_tau[temp];

		// Intercellular partial pressure of CO2 given stomatal opening (Pa)
		// Eqn 7, Haxeltine & Prentice 1996a
		double pi_co2 = lambda * co2 * PATMOS * CO2_CONV;

		// Calculation of C1_C3, Eqn 4, Haxeltine & Prentice 1996a
		// High-temperature inhibition modelled by suppression of LUE by decreased
		// relative affinity of rubisco for CO2 with increasing temperature (Table 3.7,
		// Larcher 1983)
		// Notes: - there is an error in Eqn 4, Haxeltine & Prentice 1996a (missing
		//          2.0* in denominator) which is fixed here (see Eqn A2, Collatz
		//          et al 1991)
		//        - the explicit low temperature inhibition function has been removed
		//          and replaced by a temperature-dependent upper limit on V_m, see
		//          below
		//        - the reduction in maximum photosynthesis due to leaf age (phi_c)
		//          has been removed
		//        - alpha_a, accounting for reduction in PAR utilisation efficiency
		//          from the leaf to ecosystem level, appears in the calculation of
		//          apar (above) instead of here
		//        - C_mass, the atomic weight of carbon, appears in the calculation
		//          of V_m instead of here
		c1 = (pi_co2 - gammastar) / (pi_co2 + 2.0 * gammastar) * ALPHA_C3;

		// Calculation of C2_C3, Eqn 6, Haxeltine & Prentice 1996a
		c2 = (pi_co2 - gammastar) / (pi_co2 + lookup_kc[temp] * (1.0 + PO2/lookup_ko[temp]));
		b = BC3;
	}
	else {							// C4 photosynthesis
		// Calculation of C1_C4 given actual pi (lambda)
		// C1_C4 incorporates term accounting for effect of intercellular CO2
		// concentration on photosynthesis (Eqn 14, 16, Haxeltine & Prentice 1996a)
		c1 = min(lambda/LAMBDA_SC4, 1.0) * ALPHA_C4;
		c2 = 1;
		b = BC4;
	}
	if (vm < 0) {

		// Calculation of non-water-stressed rubisco capacity (Eqn 11, Haxeltine & Prentice 1996a)
		vmax(b, c1, c2, apar, tscal, daylength, temp, nactive, ifnlimvmax, result.vm, result.vmaxnlim, result.nactive_opt);
	}
	else {
		result.vm = vm;			// reuse existing Vmax
	}
	// Calculation of daily leaf respiration
	// Eqn 10, Haxeltine & Prentice 1996a
	result.rd_g = result.vm * b;

	// PAR-limited photosynthesis rate (gC/m2/h)
	// Eqn 3, Haxeltine & Prentice 1996a
	result.je = c1 * tscal * apar * CMASS * CQ / daylength;

	// Rubisco-activity limited photosynthesis rate (gC/m2/h)
	// Eqn 5, Haxeltine & Prentice 1996a
	double jc = c2 * result.vm / 24.0;

	// Calculation of daily gross photosynthesis
	// Eqn 2, Haxeltine & Prentice 1996a
	// Notes: - there is an error in Eqn 2, Haxeltine & Prentice 1996a (missing
	// 			theta in 4*theta*je*jc term) which is fixed here
	result.agd_g = (result.je + jc - sqrt((result.je + jc) * (result.je + jc) - 4.0 * THETA * result.je * jc)) /
														(2.0 * THETA) * daylength;

	// Leaf-level net daytime photosynthesis (gC/m2/day)
	// Based on Eqn 19, Haxeltine & Prentice 1996a
	double adt = result.agd_g - daylength / 24.0 * result.rd_g;

	// Convert to CO2 diffusion units (mm/m2/day) using ideal gas law
	result.adtmm = adt / CMASS * 8.314 * (temp + K2degC) / PATMOS * 1e3;
}

/// Calculate value for canopy conductance component associated with photosynthesis (mm/s)
/** Eqn 21, Haxeltine & Prentice 1996
 *  includes conversion of daylight from hours to seconds
 */
inline double gpterm(double adtmm, double co2, double lambda, double daylength) {
	if (adtmm <= 0) {
		return 0;
	}
	return 1.6 / CO2_CONV / 3600 * adtmm / co2 / (1 - lambda) / daylength;
}

/// Pre-calculate Vmax and no-stress assimilation and canopy conductance
/**
 * Vmax is calculated on a daily scale (w/ daily averages of temperature and par)
 * Subdaily values calculated if needed
 */
void photosynthesis_nostress(Patch& patch, Climate& climate) {

	// If this is the first patch, calculate no-stress assimilation for
	// each Standpft, assuming FPAR=1. This is then later used in
	// forest_floor_conditions.
	if (!patch.id) {

		for (int p=0; p<npft; p++) {
			Standpft& spft = patch.stand.pft[p];
			if (spft.active) {

				// Call photosynthesis assuming stomates fully open (lambda = lambda_max)
				photosynthesis(climate.co2, climate.temp, climate.par, climate.daylength,
					1.0, spft.pft.lambda_max, spft.pft, 1.0, false, spft.photosynthesis, -1);
			}
		}
	}

	// Pre-calculation of no-stress assimilation for each individual
	Vegetation& vegetation = patch.vegetation;
	vegetation.firstobj();

	while (vegetation.isobj) {
		Individual& indiv = vegetation.getobj();
		Pft& pft = indiv.pft;

		// Individual photosynthesis with no nitrogen limitation
		photosynthesis(climate.co2, climate.temp, climate.par, climate.daylength,
		               indiv.fpar, pft.lambda_max, pft,
		               1.0, false,
		               indiv.photosynthesis,
		               -1);

		indiv.gpterm = gpterm(indiv.photosynthesis.adtmm, climate.co2, pft.lambda_max, climate.daylength);

		if (date.diurnal()) {

			indiv.gpterms.assign(date.subdaily, 0);
			PhotosynthesisResult res;
			indiv.phots.assign(date.subdaily, res);

			for (int i=0; i<date.subdaily; i++) {
				PhotosynthesisResult& result = indiv.phots[i];
				photosynthesis(climate.co2, climate.temps[i], climate.pars[i], 24,
				               indiv.fpar, pft.lambda_max, pft,
				               1.0, false,
				               result,
				               indiv.photosynthesis.vm);

				indiv.gpterms[i] = gpterm(result.adtmm, climate.co2, pft.lambda_max, 24);
			}
		}
		vegetation.nextobj();
	}
}

/// Calculates individual fnuptake based on surface of fine root
/** Calculates individual fraction nitrogen uptake based on surface of fine root
 *  Roots are cone formed with height == radius.
 *  V = PI * r^3 / 3
 *  A = (2^1/2 + 1) * PI * r^2
 *  -> A = const * cmass_root^2/3
 */
double nitrogen_uptake_strength(const Individual& indiv) {
	return pow(max(0.0, indiv.cmass_root_today()) * indiv.pft.nupscoeff * indiv.cton_status / indiv.densindiv, 2.0 / 3.0) * indiv.densindiv;
}

/// Individual nitrogen uptake fraction
/** Determining individual nitrogen uptake as a fraction of its nitrogen demand.
 *
 *  \see ncompete
 *
 *  Function nitrogen_uptake_strength() determines how good individuals are at
 *  acquiring nitrogen.
 */
void fnuptake(Vegetation& vegetation, double nmass_avail) {

	// Create vector describing the individuals to ncompete()
	std::vector<NCompetingIndividual> individuals(vegetation.nobj);

	for (unsigned int i = 0; i < vegetation.nobj; i++) {
		individuals[i].ndemand = vegetation[i].ndemand;
		individuals[i].strength = nitrogen_uptake_strength(vegetation[i]);
	}

	// Let ncompete() do the actual distribution
	ncompete(individuals, nmass_avail);

	// Get the results, nitrogen uptake fraction for each individual
	for (unsigned int i = 0; i < vegetation.nobj; i++) {
		vegetation[i].fnuptake = individuals[i].fnuptake;
	}
}


/// Use nitrogen storage to limit stress
/** Retranslocated nitrogen from last year is used to
 *  limit nitrogen stress in leaves, roots, and sap wood
 */
void nstore_usage(Vegetation& vegetation) {

	vegetation.firstobj();
	while (vegetation.isobj) {
		Individual& indiv=vegetation.getobj();

		// individual excess nitrogen demand after uptake
		double excess_ndemand = (indiv.leafndemand + indiv.rootndemand) * (1.0 - indiv.fnuptake)
		                        + indiv.leafndemand_store + indiv.rootndemand_store;

		// if individual is in need of using its labile nitrogen storage
		if (!negligible(excess_ndemand)) {

			// if labile nitrogen storage is larger than excess nitrogen demand
			if (excess_ndemand <= indiv.nstore_labile) {

				// leaf nitrogen demand
				double leaf_ndemand = indiv.leafndemand * (1.0 - indiv.fnuptake) + indiv.leafndemand_store;
				indiv.nmass_leaf    += leaf_ndemand;
				indiv.nstore_labile -= leaf_ndemand;

				// root nitrogen demand
				double root_ndemand = indiv.rootndemand * (1.0 - indiv.fnuptake) + indiv.rootndemand_store;
				indiv.nmass_root    += root_ndemand;
				indiv.nstore_labile -= root_ndemand;

#ifdef CRESCENDO_FACE
				indiv.report_flux(Fluxes::DNGL, leaf_ndemand);
				indiv.report_flux(Fluxes::DNGR, root_ndemand);
#endif

				indiv.nstress = false;
			}
			else {

				if (!negligible(indiv.nstore_labile)) {

					// calculate total nitrogen mass
					double tot_nmass = indiv.nmass_leaf + indiv.nmass_root + indiv.fnuptake * (indiv.leafndemand + indiv.rootndemand) + indiv.nstore_labile;

					// new leaf C:N ratio
					double cton_leaf = (indiv.cmass_leaf_today() + indiv.cmass_root_today() * (indiv.pft.cton_leaf_avr / indiv.pft.cton_root_avr)) / tot_nmass;

					// nitrogen added to leaf from storage
					double labile_nto_leaf = indiv.cmass_leaf_today() / cton_leaf - (indiv.nmass_leaf + indiv.fnuptake * indiv.leafndemand);

					// new leaf nitrogen
					indiv.nmass_leaf += labile_nto_leaf;

					// new root nitrogen
					indiv.nmass_root += indiv.nstore_labile - labile_nto_leaf;

#ifdef CRESCENDO_FACE
					indiv.report_flux(Fluxes::DNGL, labile_nto_leaf);
					indiv.report_flux(Fluxes::DNGR, indiv.nstore_labile - labile_nto_leaf);
#endif

					indiv.nstore_labile = 0.0;
				}

				// nitrogen stressed photosynthesis is allowed only when nitrogen limitation is turned on
				indiv.nstress = ifnlim;
				
			}
		}
		else
			// photosynthesis will not be nitrogen stresses
			indiv.nstress = false;

		vegetation.nextobj();
	}
}

/// Nitrogen demand
/** Determines nitrogen demand based on vmax for leaves.
 *  Roots and sap wood nitrogen concentration follows leaf
 *  nitrogen concentration.
 *  Also determines individual nitrogen uptake capability
 */
void ndemand(Patch& patch, Vegetation& vegetation) {

	Gridcell& gridcell = patch.stand.get_gridcell();
	Soil& soil = patch.soil;

	/// daily nitrogen demand for patch (kgN/m2)
	patch.ndemand = 0.0;

	// Scalar to soil temperature (Eqn A9, Comins & McMurtrie 1993) for nitrogen uptake
	double temp_scale = soil.temp > 0.0 ? max(0.0, 0.0326 + 0.00351 * pow(soil.temp, 1.652) - pow(soil.temp / 41.748, 7.19)) : 0.0;

	/// Rate of nitrogen uptake not associated with Michaelis-Menten Kinetics (Zaehle and Friend 2010)
	double kNmin = 0.05;

	vegetation.firstobj();
	while (vegetation.isobj) {
		Individual& indiv = vegetation.getobj();

		// Rescaler of nitrogen uptake
		indiv.fnuptake = 1.0;

		// Starts with no nitrogen stress
		indiv.nstress = false;

		// Optimal leaf nitrogen content
		double leafoptn;

		// Optimal leaf C:N ratio
		double cton_leaf_opt;

		// Calculate optimal leaf nitrogen content and demand
		if (!negligible(indiv.phen) || !negligible(indiv.cmass_leaf_today())) {

			indiv.nday_leafon++;

			// Added a scalar depending on individual lai to slow down light optimization of newly shaded leafs
			// Peltoniemi et al. 2012
			indiv.nextin = exp(0.12 * min(10.0*indiv.phen, indiv.lai_indiv_today()));

			// Calculate optimal leaf nitrogen associated with photosynthesis and none photosynthetic
			// active nitrogen (Haxeltine et al. 1996 eqn 27/28)

			leafoptn = indiv.photosynthesis.nactive_opt * indiv.nextin + N0 * indiv.cmass_leaf_today();

			// Can not have higher nitrogen concentration than minimum leaf C:N ratio
			if (indiv.cmass_leaf_today() / leafoptn < indiv.pft.cton_leaf_min) {
				leafoptn = indiv.cmass_leaf_today() / indiv.pft.cton_leaf_min;
			}
			// Can not have lower nitrogen concentration than maximum leaf C:N ratio
			else if (indiv.cmass_leaf_today() / leafoptn > indiv.pft.cton_leaf_max) {
				leafoptn = indiv.cmass_leaf_today() / indiv.pft.cton_leaf_max;
			}

			// Updating annual optimal leaf C:N ratio
			indiv.cton_leaf_aopt = min(indiv.cmass_leaf_today() / leafoptn, indiv.cton_leaf_aopt);

			// Leaf nitrogen demand
			indiv.leafndemand = max(leafoptn - indiv.nmass_leaf, 0.0);

			// Setting daily optimal leaf C:N ratio
			if (indiv.leafndemand) {
				cton_leaf_opt = indiv.cmass_leaf_today() / leafoptn;
			}
			else {
				cton_leaf_opt = max(indiv.pft.cton_leaf_min, indiv.cton_leaf());
			}
		}
		else {
			indiv.leafndemand = 0.0;
			cton_leaf_opt = indiv.cton_leaf();
		}

		// Nitrogen demand

		// Root nitrogen demand
		indiv.rootndemand = max(0.0, indiv.cmass_root_today() / (cton_leaf_opt * indiv.pft.cton_root_avr / indiv.pft.cton_leaf_avr) - indiv.nmass_root);

		// Sap wood nitrogen demand. Demand is ramped up throughout the year.
		if (indiv.pft.lifeform == TREE) {
			indiv.sapndemand = max(0.0, indiv.cmass_sap / (cton_leaf_opt * indiv.pft.cton_sap_avr / indiv.pft.cton_leaf_avr) - indiv.nmass_sap) * ((1.0 + (double)date.day) / (double)date.year_length());
		}

		// Labile nitrogen storage demand
		indiv.storendemand = indiv.ndemand_storage(cton_leaf_opt);
		//TODO HO demand
		indiv.hondemand = 0.0;

		// Total nitrogen demand
		double ndemand_tot = indiv.leafndemand + indiv.rootndemand + indiv.sapndemand + indiv.storendemand + indiv.hondemand;

		// Calculate scalars to possible nitrogen uptake

		// Current plant mobile nitrogen concentration
		double ntoc = !negligible(indiv.cmass_leaf_today() + indiv.cmass_root_today()) ? (indiv.nmass_leaf + indiv.nmass_root) / (indiv.cmass_leaf_today() + indiv.cmass_root_today()) : 0.0;

		// Scale to maximum nitrogen concentrations
		indiv.cton_status = max(0.0, (ntoc - 1.0 / indiv.pft.cton_leaf_min) / (1.0 / indiv.pft.cton_leaf_avr - 1.0 / indiv.pft.cton_leaf_min));

		// Nitrogen availablilty scalar due to saturating Michaelis-Menten kinetics
		double nmin_scale = kNmin + soil.nmass_avail / (soil.nmass_avail + gridcell.pft[indiv.pft.id].Km);

		// Maximum available soil mineral nitrogen for this individual is base on its root area.
		// This is considered to be related to FPC which is proportional to crown area which is approx
		// 4 times smaller than the root area
		double max_indiv_avail = min(1.0, indiv.fpc * 4.0) * soil.nmass_avail;

		// Maximum nitrogen uptake due to all scalars (times 2 because considering both NO3- and NH4+ uptake)
		// and soil available nitrogen within individual projectived coverage
		double maxnup = min(2.0 * indiv.pft.nuptoroot * nmin_scale * temp_scale * indiv.cton_status * indiv.cmass_root_today(), max_indiv_avail);

		// Nitrogen demand limitation due to maximum nitrogen uptake capacity
		double fractomax = ndemand_tot > 0.0 ? min(maxnup/ndemand_tot,1.0) : 0.0;

		// Root and leaf demand from storage pools
		indiv.leafndemand_store = indiv.leafndemand * (1.0 - fractomax);
		indiv.rootndemand_store = indiv.rootndemand * (1.0 - fractomax);

		// Nitrogen demand after adjustment to maximum uptake capacity
		indiv.leafndemand  *= fractomax;
		indiv.rootndemand  *= fractomax;
		indiv.sapndemand   *= fractomax;
		indiv.storendemand *= fractomax;

		// Sum total nitrogen demand individual is capable of taking up
		indiv.ndemand = indiv.leafndemand + indiv.rootndemand + indiv.sapndemand + indiv.storendemand;

		// Negative nitrogen demand not allowed
		if (indiv.ndemand <= 0.0) {
			indiv.ndemand = 0.0;

			// Compartments fraction of total nitrogen demand
			indiv.leaffndemand  = 0.0;
			indiv.rootfndemand  = 0.0;
			indiv.sapfndemand   = 0.0;
			indiv.storefndemand = 0.0;
		}
		else {

			// Compartments fraction of total nitrogen demand
			indiv.leaffndemand  = indiv.leafndemand / indiv.ndemand;
			indiv.rootfndemand  = indiv.rootndemand / indiv.ndemand;
			indiv.sapfndemand   = indiv.sapndemand  / indiv.ndemand;
			indiv.storefndemand = max(0.0, 1.0 - (indiv.leaffndemand + indiv.rootfndemand + indiv.sapfndemand));
		}

		// Sum total patch nitrogen demand
		patch.ndemand += indiv.ndemand;

		vegetation.nextobj();
	}
}

/// Recalculation of photosynthesis under vmax nitrogen stress
/** If nitrogen supply is not able to meet demand it will lead
 *  to down-regulation of vmax resulting in lower photosynthesis
 */
void vmax_nitrogen_stress(Patch& patch, Climate& climate, Vegetation& vegetation) {

	// Supply function for nitrogen and determination of nitrogen stress leading
	// to down-regulation of vmax.

	// Nitrogen within projective cover of all individuals
	double tot_nmass_avail = patch.soil.nmass_avail * min(1.0, patch.fpc_total);

	if (patch.stand.landcover == CROPLAND && ifnlim) { // Also for other landcovers ??
		// Take soil wcont into account
		tot_nmass_avail *= patch.soil.wcont[0] * 0.9 + patch.soil.wcont[1] * 0.1;
	}

	// Calculate individual uptake fraction of nitrogen demand
	if (patch.ndemand > tot_nmass_avail) {

		// Determine individual nitrogen uptake fractions
		fnuptake(vegetation, tot_nmass_avail);
	}

	// Resolve nitrogen stress with longterm stored nitrogen
	nstore_usage(vegetation);

	// Calculate leaf nitrogen associated with photosynthesis, nitrogen limited photosynthesis,
	// and annual otimal leaf nitrogen content and nitrogen limitation on vmax

	vegetation.firstobj();

	while (vegetation.isobj) {
		Individual& indiv = vegetation.getobj();
		Pft& pft = indiv.pft;

		// Calculate leaf nitrogen associated with photosynthesis (Haxeltine et al. 1996 eqn 27/28)
		// Added difference between needleleaved and broadleaved mentioned in Friend et al. 1997
		// Should be done on FPC basis, but is not as it does not matter mathematically
		// Needs to be calculated for each individual due to possible water stress

		// Todays leaf nitrogen after uptake
		double nmass_leaf = indiv.nmass_leaf + indiv.leafndemand * indiv.fnuptake;

		if (indiv.phen > 0.0) {
			indiv.nactive = max(0.0, nmass_leaf - N0 * indiv.cmass_leaf_today());
		}
		else {
			indiv.nactive = 0.0;
		}

		// Individuals photosynthesis is nitrogen stressed
		if (indiv.nstress) {

			// Individual photosynthesis
			photosynthesis(climate.co2, climate.temp, climate.par, climate.daylength,
				indiv.fpar, pft.lambda_max, pft,
				indiv.nactive / indiv.nextin, true,
				indiv.photosynthesis,
				-1);

			indiv.gpterm = gpterm(indiv.photosynthesis.adtmm, climate.co2, pft.lambda_max, climate.daylength);

			if (date.diurnal()) {
				for (int i=0; i<date.subdaily; i++) {
					PhotosynthesisResult& result = indiv.phots[i];
					photosynthesis(climate.co2, climate.temps[i], climate.pars[i], 24,
						indiv.fpar, pft.lambda_max, pft,
						indiv.nactive / indiv.nextin, true,
						result,
						indiv.photosynthesis.vm);

					indiv.gpterms[i] = gpterm(result.adtmm, climate.co2, pft.lambda_max, 24);
				}
			}
		}

		// Sum annual average nitrogen limitation on vmax
		if (indiv.phen)
			indiv.avmaxnlim += indiv.photosynthesis.vmaxnlim;

		// On last day of year determined average nitrogen limitation
		// based on days with leaf on
		if (date.islastday && date.islastmonth) {

			if (!negligible(indiv.nday_leafon)) {
				indiv.avmaxnlim /= (double)indiv.nday_leafon;
			}
			else {
				indiv.avmaxnlim = 0.0;
			}
		}
		vegetation.nextobj();
	}
}

/// Transpirative demand
/** Two alternative parameterisations of aet_monteith are available:
 *      AET_MONTEITH_HYPERBOLIC and AET_MONTEITH_EXPONENTIAL
 *  \see canexch.h
 */
void wdemand(Patch& patch, Climate& climate, Vegetation& vegetation, const Day& day) {

	// Determination of transpirative demand based on a Monteith parameterisation of
	// boundary layer dynamics, i.e. demand = f(EET, conductance)

	double gp_patch = 0.0;
		// non-water-stressed canopy conductance for patch, patch vegetated area
		// basis (mm/s)
	double gp_leafon_patch = 0.0;
		// non-water-stressed canopy conductance assuming full leaf cover, patch
		// vegetated area basis (mm/s)

	vegetation.firstobj();
	while (vegetation.isobj) {
		Individual& indiv = vegetation.getobj();

		Pft& pft = indiv.pft;

		// Calculate non-water-stressed canopy conductance assuming full leaf cover
		//        - include canopy-conductance component not linked to
		//          photosynthesis (diffusion through leaf cuticle etc); this is
		//          assumed to be proportional to leaf-on fraction

		// Call photosynthesis for individual assuming stomates fully open
		// (lambda = lambda_max)

		if (indiv.growingseason()) {

			PhotosynthesisResult leafon_photosynthesis;

			// Call photosynthesis first with fpar_leafon to get gp_leafon below.
			// Should hopefully not be needed in future, demand_leafon only used
			// by raingreen phenology.

			double temp = date.diurnal() ? climate.temps[day.period] : climate.temp;
			double par = date.diurnal() ? climate.pars[day.period] : climate.par;
			double daylength = date.diurnal() ? 24 : climate.daylength;

			// No nitrogen limitation when calculating gp_leafon
			photosynthesis(climate.co2, temp, par, daylength,
			               indiv.fpar_leafon, pft.lambda_max, pft,
			               1.0, false,
			               leafon_photosynthesis,
			               -1);

			double gp_leafon = gpterm(leafon_photosynthesis.adtmm, climate.co2, pft.lambda_max, daylength) + pft.gmin * indiv.fpc;

			// Increment patch sums of non-water-stressed gp by individual value
			gp_patch +=  (date.diurnal() ? indiv.gpterms[day.period] : indiv.gpterm) + pft.gmin * indiv.fpc_today();
			gp_leafon_patch += gp_leafon;
		}

		vegetation.nextobj();
	}

	// Calculate transpirational demand on patch vegetated area basis
	// Eqn 23, Haxeltine & Prentice 1996
	if (!negligible(gp_patch) && !negligible(patch.fpc_total)) {
		gp_patch /= patch.fpc_total;
		patch.wdemand = aet_monteith(patch.eet_net_veg, gp_patch);
	}
	else
		patch.wdemand = 0.0;

	patch.wdemand_day += patch.wdemand;
	if (day.isend) {
		patch.wdemand_day /= date.subdaily;
	}

	if (!negligible(gp_leafon_patch) && !negligible(patch.fpc_total)) {
		gp_leafon_patch /= patch.fpc_total;
		patch.wdemand_leafon = aet_monteith(patch.eet_net_veg, gp_leafon_patch);
	}
	else
		patch.wdemand_leafon = 0.0;
}

/// Plant water uptake
/**
 * Returns plant water uptake (point scale, or mean for patch) as a fraction of
 * maximum possible (daily basis).
 *
 * Supports alternative parameterisations of plant water uptake:
 *
 * WCONT           = uptake rate coupled to water content and vertical
 *                   root distribution (as in earlier versions of LPJ-GUESS and LPJF)
 * ROOTDIST        = uptake rate independent of water content (to wilting point)
 *                   but with fractional uptake from different layers according
 *                   to prescribed root distribution
 * SMART           = uptake rate independent of water content (to wilting point),
 *                   fractional uptake from different layers according to layer
 *                   water content for trees, according to prescribed root
 *                   distribution for grasses
 * SPECIESSPECIFIC = uptake rate is species specific, with more drought
 *                   tolerance species (lower species_drought_tolerance values)
 *                   having greater relative uptake rates.
 */
inline double water_uptake(double wcont[NSOILLAYER], double awc[NSOILLAYER],
	double rootdist[NSOILLAYER], double emax, double fpc_rescale,
	double fwuptake[NSOILLAYER], bool ifsmart, double species_drought_tolerance) {

	// INPUT PARAMETERS:
	//   wcont       = water content of soil layers as fraction between wilting point
	//                 (0) and available water holding capacity (1)
	//   awc         = available water holding capacity of each soil layer (mm)
	//   rootdist    = plant root distribution (fraction in each soil layer)
	//   emax        = maximum evapotranspiration rate (mm/day)
	//   fpc_rescale = scaling factor for foliar projective cover (complement of patch
	//                 summed FPC overlap)
	//   ifsmart     = whether plants can freely adapt root profile to distribution of
	//                 available water among layers (required for "smart" mode)
	//   species_drought_tolerance = used only if the SPECIESSPECIFIC option is specified.


	// OUTPUT PARAMETER:
	//   fwuptake     = fraction of total uptake originating from each layer

	double wr;
	int s;

	switch (wateruptake) {
	case WR_WCONT:

		// LPJ "standard" formulation with linear scaling of uptake to water content
		// and weighting by plant root profiles

		wr = 0.0;
		for (s=0; s<NSOILLAYER; s++) {
			fwuptake[s] = rootdist[s] * wcont[s] * fpc_rescale;
			wr += fwuptake[s];
		}
		break;

	// guess2008 - drought/water uptake changes - new option
	case WR_SPECIESSPECIFIC:

		// Uptake rate is species specific, with more drought tolerance species (lower species_drought_tolerance
		// values) having greater relative uptake rates.
		// Reduces to WCONT if species_drought_tolerance = 0.5

		wr = 0.0;
		for (s=0; s<NSOILLAYER; s++) {
			double max_rel_uptake = pow(wcont[s], 2.0 * 0.1); // Upper limit. Limits C3 grass uptake
			fwuptake[s] = rootdist[s] * min(pow(wcont[s], 2.0 * species_drought_tolerance), max_rel_uptake) * fpc_rescale;
			wr += fwuptake[s];
		}
		break;
	case WR_ROOTDIST:

		// Uptake rate independent of water content (to wilting point) but with fractional
		// uptake from different layers according to prescribed root distribution

		wr = 0.0;
		for (s=0; s<NSOILLAYER; s++) {
			fwuptake[s] = min(wcont[s] * awc[s] * fpc_rescale, emax * rootdist[s]) / emax;
			wr += fwuptake[s];
		}
		break;
	case WR_SMART:
		{

			// Uptake rate independent of water content (to wilting point), fractional uptake
			// from different layers according to layer water content for trees, and according
			// to prescribed root distribution for grasses

			double wcsum = 0.0;
			double wcfrac;

			for (s=0; s<NSOILLAYER; s++) wcsum += wcont[s];

			wr = 0.0;
			if (negligible(wcsum))
				for (s=0; s<NSOILLAYER; s++) fwuptake[s] = 0.0;
			else {
				for (s=0; s<NSOILLAYER; s++) {
					wcfrac = wcont[s] / wcsum;
					if (ifsmart)
						fwuptake[s] = min(wcont[s] * awc[s] * wcfrac * fpc_rescale, emax * wcfrac) / emax;
					else
						fwuptake[s] = min(wcont[s] * awc[s] * fpc_rescale, emax * rootdist[s]) / emax;
					wr += fwuptake[s];
				}
			}
		}
		break;
	default:
		// Should never happen
		fail("Unsupported wateruptake type");
	}

	if (!negligible(wr))
		for (s=0; s<NSOILLAYER; s++)
			fwuptake[s] /= wr;

	return wr;
}

/// Plant water uptake for irrigated crops
/**
 * Returns plant water uptake (point scale, or mean for patch) as a fraction of
 * maximum possible (daily basis), after adding required water to obtain maximum
 * water uptake.
 * Irrigation water is added to the soil in hydrology_lpjf
 *
 * Only ROOTDIST currently supported plant water uptake parameterisation:
 *
 * ROOTDIST        = uptake rate independent of water content (to wilting point)
 *                   but with fractional uptake from different layers according
 *                   to prescribed root distribution
 */
double irrigated_water_uptake(Patch& patch, Pft& pft, const Day& day) {
	Patchpft& ppft = patch.pft[pft.id];
	double* awc = patch.soil.soiltype.awc;

	double wcont_cp[NSOILLAYER];
	for (int i=0;i<NSOILLAYER;i++) {
		wcont_cp[i] = patch.soil.wcont[i];
	}

	if (day.isstart) {
		ppft.water_deficit_d = 0.0;
		if (date.day == 0) {
			ppft.water_deficit_y = 0.0;
		}
	}

	if (patch.soil.wcont[0]<0.9 && ppft.phen > 0.0)	{
		double wcont_0_opt = 0.0;
		double wr_opt = min(1.0, patch.wdemand / ppft.phen / pft.emax);

		if (wateruptake == WR_ROOTDIST) {

			wcont_0_opt = (wr_opt * pft.emax - min(patch.soil.wcont[1] * awc[1] * patch.fpc_rescale, pft.emax * pft.rootdist[1])) / awc[0] / patch.fpc_rescale;

			if (wcont_0_opt * awc[0] * patch.fpc_rescale > pft.emax * pft.rootdist[0]) {
				wcont_0_opt = pft.emax * pft.rootdist[0] / awc[0] / patch.fpc_rescale;
			}
		}
		else {
			fail("Irrigation soil water only balanced for WR_ROOTDIST currently !\n");
		}

		if (wcont_0_opt > patch.soil.wcont[0]) {
			ppft.water_deficit_d += (wcont_0_opt-patch.soil.wcont[0]) * awc[0];
			wcont_cp[0] = wcont_0_opt;
		}

		if (day.isend) {
			ppft.water_deficit_d /= date.subdaily;
			ppft.water_deficit_y += ppft.water_deficit_d;
		}
	}
	return water_uptake(wcont_cp, awc, pft.rootdist, pft.emax, patch.fpc_rescale,
			ppft.fwuptake, pft.lifeform == TREE, pft.drought_tolerance);
};


/// Actual evapotranspiration and water stress
/** Soil water supply at the roots available to meet the transpirational demand
 *  Fundamentally, water stress = supply < demand
 */
void aet_water_stress(Patch& patch, Vegetation& vegetation, const Day& day) {

	// Supply function for evapotranspiration and determination of water stress leading
	// to down-regulation of stomatal conductance. Actual evapotranspiration determined
	// as smaller of supply and transpirative demand (see function demand).
	// Base value for actual canopy conductance calculated here for water-stressed
	// individuals and used to derive actual photosynthesis in function npp (below)

	// Calculate common point supply for each PFT in this patch
	for (int p=0; p<npft; p++) {

		Standpft& spft = patch.stand.pft[p];
		if (!spft.active)
			continue;

		// Retrieve next patch PFT
		Patchpft& ppft = patch.pft[p];

		// Retrieve PFT
		Pft& pft = ppft.pft;

		if (day.isstart || spft.irrigated && pft.id == patch.stand.pftid) {

			// Calculate effective water supply from plant roots
			// Rescale available water by patch FPC if exceeds 1
			// (this then represents the average amount of water available over an
			// individual's FPC, assuming individuals are equal in competition for water)
			double wr;

			if (spft.irrigated && pft.id == patch.stand.pftid) {
				wr = irrigated_water_uptake(patch, pft, day);
			} else {
				wr = water_uptake(patch.soil.wcont, patch.soil.soiltype.awc,
							pft.rootdist, pft.emax, patch.fpc_rescale, ppft.fwuptake,
							pft.lifeform == TREE, pft.drought_tolerance);
			}

			// Calculate supply (Eqn 24, Haxeltine & Prentice 1996)
			if (patch.stand.landcover!=CROPLAND || ppft.cropphen->growingseason)
				ppft.wsupply_leafon = pft.emax * wr;
			else
				ppft.wsupply_leafon = 0.0;
			ppft.wsupply = ppft.wsupply_leafon * ppft.phen;
		}

		ppft.wstress = ppft.wsupply < patch.wdemand && !negligible(ppft.phen) && !(pft.phenology==CROPGREEN && !largerthanzero(patch.wdemand-ppft.wsupply, -10));

		// Calculate water-stressed canopy conductance on FPC basis assuming
		// FPAR=1 and deducting canopy conductance component not associated
		// with CO2 uptake; valid for all individuals of this PFT in this patch
		// today.
		// Eqn 25, Haxeltine & Prentice 1996

		// Fix, valid for monocultures, for faulty equation, manifesting itself in problems with crops in high scenario CO2-levels.
		// No fix for natural vegetation yet.
		double gmin = pft.phenology==CROPGREEN ? ppft.phen * pft.gmin : pft.gmin;

		ppft.gcbase = ppft.wstress ? max(gc_monteith(ppft.wsupply, patch.eet_net_veg)-
					gmin * ppft.wsupply / patch.wdemand, 0.0) : 0;

		if (!date.diurnal()) {
			ppft.wstress_day = ppft.wstress;
			ppft.gcbase_day = ppft.gcbase;
		}
		else if (day.isend) {

			ppft.wstress_day = ppft.wsupply < patch.wdemand_day && !negligible(ppft.phen) && !(pft.phenology==CROPGREEN && !largerthanzero(patch.wdemand-ppft.wsupply, -10));

			ppft.gcbase_day = ppft.wstress_day ? max(gc_monteith(ppft.wsupply,
					patch.eet_net_veg) - gmin * ppft.wsupply / patch.wdemand_day, 0.0) : 0;
		}
	}

	// Calculate / transfer supply to individuals
	vegetation.firstobj();
	while (vegetation.isobj) {
		Individual& indiv = vegetation.getobj();
		Patchpft& ppft = patch.pft[indiv.pft.id];
		if (day.isstart) {
			indiv.aet = 0;

			if (date.day == 0)
				indiv.aaet = 0.0;
		}

		indiv.wstress = ppft.wstress;

		if (indiv.alive) {
			if (indiv.wstress) {
				indiv.aet += ppft.wsupply;
			}
			else {
				indiv.aet += negligible(indiv.phen) ? 0.0 : patch.wdemand;
			}
		}
		if (day.isend) {
			indiv.aet *= indiv.fpc / date.subdaily;
		}

		if (day.isend) {
			indiv.aaet += indiv.aet;
		}

		vegetation.nextobj();
	}
}

/// Water scalar
void water_scalar(Patch& patch, Vegetation& vegetation, const Day& day) {

	// Derivation of daily and annual versions of water scalar (wscal, omega)
	// Daily version is used to determine leaf onset and abscission for raingreen PFTs.
	// Annual version determines relative allocation to roots versus leaves for
	// subsequent year

	for (int p=0; p<npft; p++) {

		// Retrieve next patch PFT
		Patchpft& ppft = patch.pft[p];

		if (!patch.stand.pft[p].active)
			continue;

		if (day.isstart) {
			ppft.wscal = 0;
			if (date.day == 0) {
				ppft.wscal_mean = 0;
				if (ppft.pft.phenology==CROPGREEN || ppft.pft.isintercropgrass)
					ppft.cropphen->growingdays_y=0;
			}
		}

		// Calculate patch PFT water scalar value

		if (!negligible(patch.wdemand_leafon)) {
			ppft.wscal += min(1.0, ppft.wsupply_leafon/patch.wdemand_leafon);
		}
		else {
			ppft.wscal += 1.0;
		}

		if (day.isend) {
			ppft.wscal /= (double)date.subdaily;

			if (patch.stand.landcover!=CROPLAND										//natural, urban, pasture, forest and peatland stands
					|| ppft.pft.phenology==ANY && ppft.pft.id==patch.stand.pftid) {	//normal grass growth
				ppft.wscal_mean += ppft.wscal;

				// Convert from sum to mean on last day of year
				if (date.islastday && date.islastmonth) {
					ppft.wscal_mean /= (double)date.year_length();
				}
			}
			else if (ppft.cropphen->growingseason									// true crops and cover-crop grass
					|| ppft.pft.phenology == CROPGREEN && date.day == ppft.cropphen->hdate
					|| ppft.pft.isintercropgrass && date.day == patch.pft[patch.stand.pftid].cropphen->eicdate) {

				ppft.cropphen->growingdays_y++;
				ppft.wscal_mean = ppft.wscal_mean + (ppft.wscal - ppft.wscal_mean) / ppft.cropphen->growingdays_y;
			}
		}
	}
}


///////////////////////////////////////////////////////////////////////////////////////
// ASSIMILATION_WSTRESS
// Internal function (do not call directly from framework)

void assimilation_wstress(const Pft& pft, double co2, double temp, double par,
			double daylength, double fpar, double fpc, double gcbase,
			double vmax, PhotosynthesisResult& phot_result, double& lambda,
			double nactive, bool ifnlimvmax) {

	// DESCRIPTION
	// Calculation of net C-assimilation under water-stressed conditions
	// (demand>supply; see function canopy_exchange). Utilises a numerical
	// iteration procedure to find the level of stomatal aperture (characterised by
	// lambda, the ratio of leaf intercellular to ambient CO2 concentration) which
	// satisfies simulataneously a canopy-conductance based and light-based
	// formulation of photosynthesis (Eqns 2, 18 and 19, Haxeltine & Prentice (1996)).

	// Numerical method is a tailored implementation of the bisection method,
	// assuming root (f(lambda)=0) bracketed by f(0.02)<0 and
	// f(lambda_max)>0 (Press et al 1986)

	// The bisection method terminates when we're close enough to a root
	// (absolute value of f(lambda) < EPS), or after a maximum number of
	// iterations.

	// Note that the function sometimes doesn't search for a lambda,
	// and returns zero assimilation (for instance if there is no
	// root within the valid interval, or if daylength is zero).
	// So if zero assimilation is returned, the returned lambda should
	// not be used!

	// OUTPUT PARAMETER
	// phot_result = result of photosynthesis for the found lambda
	// lambda      = the lambda found by the bisection method (see above)


	// Set lambda to something for cases where we don't actually search for
	// a proper lambda. This value shouldn't be used (see documentation
	// above), but we'll set it to something anyway so we don't return
	// random garbage.
	lambda = -1;

	if (negligible(fpc) || negligible(fpar) || negligible(gcbase * daylength * 3600)) {
		// Return zero assimilation
		phot_result.clear();
		return;
	}

	// Canopy conductance component associated with photosynthesis on a
	// daily basis (mm / m2 / day)
	double gcphot = gcbase * daylength * 3600 / 1.6 * co2 * CO2_CONV;

	// At this point the function f(x) = g(x) - h(x) can be calculated as:
	//
	// g(x) = phot_result.adtmm / fpc (after a call to photosynthesis with lambda x)
	// h(x) = gcphot * (1 - x)

	// Evaluate f(lambda_max) to see if there's a root
	// in the interval we're searching
	photosynthesis(co2, temp, par, daylength, fpar, pft.lambda_max, pft, nactive, ifnlimvmax, phot_result, vmax);
	double f_lambda_max = phot_result.adtmm / fpc - gcphot * (1 - pft.lambda_max);

	if (f_lambda_max <= 0) {
		// Return zero assimilation
		phot_result.clear();
		return;
	}

	const double EPS = 0.1; // minimum precision of solution in bisection method

	double xmid;

	// Implement numerical solution

	double x1 = 0.02;                      // minimum bracket of root
	double x2 = pft.lambda_max;            // maximum bracket of root
	double rtbis = x1;                     // root of the bisection
	double dx = x2 - x1;

	const int MAXTRIES = 6; // maximum number of iterations towards a solution
	int b = 0;              // number of tries so far towards solution

	double fmid = EPS + 1.0;

	while (fabs(fmid) > EPS && b <= MAXTRIES) {

		b++;
		dx *= 0.5;
		xmid = rtbis + dx;				// current guess for lambda

		// Call function photosynthesis to calculate alternative value
		// for total daytime photosynthesis according to Eqns 2 & 19,
		// Haxeltine & Prentice (1996), and current guess for lambda

		photosynthesis(co2, temp, par, daylength, fpar, xmid, pft, nactive, ifnlimvmax, phot_result, vmax);

		// Evaluate fmid at the point lambda=xmid
		// fmid will be an increasing function of xmid, with a solution
		// (fmid=0) between x1 and x2

		// Second term is total daytime photosynthesis (mm/m2/day) implied by
		// canopy conductance and current guess for lambda (xmid)
		// Eqn 18, Haxeltine & Prentice 1996
		fmid = phot_result.adtmm / fpc - gcphot * (1 - xmid);

		if (fmid < 0) {
			rtbis = xmid;
		}
	}

	// bvoc
	lambda=xmid;
}

///////////////////////////////////////////////////////////////////////////////////////
// AUTOTROPHIC RESPIRATION
// Internal function (do not call directly from framework)

void respiration(double gtemp_air, double gtemp_soil, lifeformtype lifeform,
	double respcoeff, double cton_sap, double cton_root,
	double cmass_sap, double cmass_root_today, double assim, double& resp, 
	double& resp_root, double& resp_sap, double& resp_growth) {

	// DESCRIPTION
	// Calculation of daily maintenance and growth respiration for individual with
	// specified life form, phenological state, tissue C:N ratios and daily net
	// assimilation, given current air and soil temperatures.
	// Sitch et al. (2000), Lloyd & Taylor (1994), Sprugel et al (1996).

	// NOTE: leaf respiration is not calculated here, but included in the calculation
	// of net assimilation (function production above) as a proportion of rubisco
	// capacity (Vmax).

	// INPUT PARAMETERS
	// gtemp_air  = respiration temperature response incorporating damping of Q10
	//              response due to temperature acclimation (Eqn 11, Lloyd & Taylor
	//              1994); Eqn B2 below
	// gtemp_soil = as gtemp_air given soil temperature
	// lifeform   = PFT life form class (TREE or GRASS)
	// respcoeff  = PFT respiration coefficient
	// cton_sap   = PFT sapwood C:N ratio
	// cton_root  = PFT root C:N ratio
	// phen       = vegetation phenological state (fraction of potential leaf cover)
	// cmass_sap  = sapwood C biomass on grid cell area basis (kgC/m2)
	// cmass_root = fine root C biomass on grid cell area basis (kgC/m2)
	// assim      = net assimilation on grid cell area basis (kgC/m2/day)

	// OUTPUT PARAMETER
	// resp       = sum of maintenance and growth respiration on grid cell area basis
	//              (kgC/m2/day)

	// guess2008 - following a comment by Annett Wolf, the following parameter value was changed:
	// const double K=0.0548; // OLD value
	const double K=0.095218;  // NEW parameter value in respiration equations
	// See the comment after Eqn (4) below.

	// double resp_sap;    // sapwood respiration (kg/m2/day)
	// double resp_root;   // root respiration (kg/m2/day)
	// double resp_growth; // growth respiration (kg/m2/day)

	// Calculation of maintenance respiration components for each living tissue:
	//
	// Based on the relations
	//
	// (A) Tissue respiration response to temperature
	//     (Sprugel et al. 1996, Eqn 7)
	//
	//     (A1) Rm = 7.4e-7 * N * f(T)
	//     (A2) f(T) = EXP (beta * T)
	//
	//       where Rm   = tissue maintenance respiration rate in mol C/sec
	//             N    = tissue nitrogen in mol N
	//             f(T) = temperature response function
	//             beta = ln Q10 / 10
	//             Q10  = change in respiration rate with a 10 K change
	//                    in temperature
	//             T    = tissue absolute temperature in K
	//
	// (B) Temperature response of soil respiration across ecosystems
	//     incorporating damping of Q10 response due to temperature acclimation
	//     (Lloyd & Taylor 1994, Eqn 11)
	//
	//     (B1) R = R10 * g(T)
	//     (B2) g(T) = EXP [308.56 * (1 / 56.02 - 1 / (T - 227.13))]
	//
	//       where R    = respiration rate
	//             R10  = respiration rate at 10 K
	//             g(T) = temperature response function at 10 deg C
	//             T    = soil absolute temperature in K
	//
	// Mathematical derivation:
	//
	// For a tissue with C:N mass ratio cton, and C mass, c_mass, N concentration
	// in mol given by
	//  (1) N = c_mass / cton / atomic_mass_N
	// Tissue respiration in gC/day given by
	//  (2) R = Rm * atomic_mass_C * seconds_per_day
	// From (A1), (1) and (2),
	//  (3) R = 7.4e-7 * c_mass / cton / atomic_mass_N * atomic_mass_C
	//          * seconds_per_day * f(T)
	// Let
	//  (4) k = 7.4e-7 * atomic_mass_C / atomic_mass_N * seconds_per_day
	//        = 0.0548

	// guess2008 - there is an ERROR here, spotted by Annett Wolf
	// If we calculate the respiration at 20 degC using g(T) and compare it to
	// Sprugel's eqn 3, for 1 mole tissue N, say, we do NOT get the same result with this
	// k value. This is because g(T) = 1 at 10 degC, not 20 degC. Changing k from 0.0548
	// to 0.095218 gives exactly the same results as Sprugel at 20 degC. The scaling factor
	// 7.4e-7 used here is taken from Sprugel's eqn. (7), but they used f(T), not g(T), and
	// these are defined on different bases.

	// from (3), (4)
	//  (5) R = k * c_mass / cton * f(T)
	// substituting ecosystem temperature response function g(T) for f(T) (Eqn B2),
	//  (6) R = k * c_mass / cton * g(T)
	// incorporate PFT-specific respiration coefficient to model acclimation
	// of respiration rates to average (temperature) conditions for PFT (Ryan 1991)
	//  (7) R_pft = respcoeff_pft * k * c_mass / cton * g(T)

	if (lifeform == TREE) {

		// Sapwood respiration (Eqn 7)

		resp_sap = respcoeff * K * cmass_sap / cton_sap * gtemp_air;

		// Root respiration (Eqn 7)
		// Assumed that root phenology follows leaf phenology

		resp_root = respcoeff * K * cmass_root_today / cton_root * gtemp_soil;

		// Growth respiration = 0.25 ( GPP - maintenance respiration)

		resp_growth = (assim - resp_sap - resp_root) * 0.25;

		// guess2008 - disallow negative growth respiration
		// (following a comment (060823) from Annett Wolf)
		if(resp_growth < 0.0) resp_growth = 0.0;

		// Total respiration is sum of maintenance and growth respiration

		resp = resp_sap + resp_root + resp_growth;
	}
	else if (lifeform == GRASS) {

		// Root respiration

		resp_root = respcoeff * K * cmass_root_today / cton_root * gtemp_soil;
		resp_sap = 0.0;

		// Growth respiration (see above)

		resp_growth = (assim - resp_root) * 0.25;

		// guess2008 - disallow negative growth respiration
		// (following a comment (060823) from Annett Wolf)
		if(resp_growth < 0.0) resp_growth = 0.0;

		// Total respiration (see above)

		resp = resp_root + resp_growth;
	}
	else fail ("Canopy exchange function respiration: unknown life form");
}

/// Net Primary Productivity
/** Includes BVOC calculations \see bvoc.cpp
 */
void npp(Patch& patch, Climate& climate, Vegetation& vegetation, const Day& day) {

	// Determination of daily NPP. Leaf level net assimilation calculated for non-
	// water-stressed individuals (i.e. with fully-open stomata) using base value
	// from function demand (above); for water-stressed individuals using base value
	// for canopy conductance by a simultaneous solution of light-based and canopy
	// conductance-based equations for net daily photosynthesis (see function
	// assimilation wstress above). The latter uses the PFT-specific base value for
	// conductance from function aet_water_stress (above).
	// Plant respiration obtained by a call to function respiration (above).

	double par, temp, assim, resp, resp_leaf, resp_root, resp_sap, resp_growth, lambda, rad, gtemp;
	double hours = 24;			// diurnal "daylength" to convert to daily units

	if (date.diurnal()) {
		par   = climate.pars[day.period];
		temp  = climate.temps[day.period];
		rad   = climate.rads[day.period];
		gtemp = climate.gtemps[day.period];
	}
	else {
		par   = climate.par;
		temp  = climate.temp;
		hours = climate.daylength;
		rad   = climate.rad;
		gtemp = climate.gtemp;
	}

	vegetation.firstobj();
	while (vegetation.isobj) {
		Individual& indiv = vegetation.getobj();

		// For this individual ...

		// Retrieve PFT and patch PFT

		Pft& pft = indiv.pft;
		Patchpft& ppft = patch.pft[pft.id];

		//Don't do calculations for crops outside their growingseason
		if (!indiv.growingseason()) {
			indiv.dnpp=0.0;
			vegetation.nextobj();
			continue;
		}

		PhotosynthesisResult phot = date.diurnal() ? indiv.phots[day.period] : indiv.photosynthesis;

		if (indiv.wstress) {

			// Water stress - derive assimilation by simultaneous solution
			// of light- and conductance-based equations of photosynthesis

			assimilation_wstress(pft, climate.co2, temp, par, hours, indiv.fpar, indiv.fpc,
				ppft.gcbase, phot.vm, phot, lambda,
				indiv.nactive / indiv.nextin, ifnlim);
		}
		else {
			lambda = indiv.pft.lambda_max;
		}

		//assim = phot.net_assimilation();
		assim = phot.agd_g * 1e-3;
		resp_leaf = phot.rd_g * 1e-3;

		if (ifbvoc) {
			PhotosynthesisResult phot_nostress = date.diurnal() ? indiv.phots[day.period] : indiv.photosynthesis;
			bvoc(temp, hours, rad, climate, patch, indiv, pft, phot_nostress, phot.adtmm, day);
		}
		// Calculate autotrophic respiration
		double cmass_root;
		if (indiv.cropindiv && indiv.cropindiv->isintercropgrass && indiv.phen == 0.0)
			cmass_root = 0.0;
		else
			cmass_root = indiv.cmass_root_today();

		// Static root and sap wood C:N ratio if no N limitation
		// to not let N affect respiration for C only version of model

		double cton_sap, cton_root;
		if (ifnlim) {
			cton_sap = indiv.cton_sap();
			cton_root = indiv.cton_root();
		}
		else {
			cton_sap = pft.cton_sap_avr;
			cton_root = pft.cton_root_avr;
		}

		respiration(gtemp, patch.soil.gtemp, indiv.pft.lifeform,
			indiv.pft.respcoeff, cton_sap, cton_root,
			indiv.cmass_sap, cmass_root, assim, resp, resp_root, resp_sap, resp_growth);

		resp += resp_leaf;

		// Convert to averages for this period for accounting purposes
		assim /= date.subdaily;
		resp /= date.subdaily;

		// Update accumulated annual NPP and daily vegetation-atmosphere flux
		indiv.dnpp = assim - resp;
		indiv.anpp += indiv.dnpp;
		indiv.mgpp[date.month] += assim;
		indiv.mlambda_gpp[date.month] += lambda * assim;

		indiv.report_flux(Fluxes::NPP, indiv.dnpp);
		indiv.report_flux(Fluxes::GPP, assim);
		indiv.report_flux(Fluxes::RA, resp);
		indiv.report_flux(Fluxes::RALEAF, resp_leaf);
		indiv.report_flux(Fluxes::RASTEM, resp_sap);
		indiv.report_flux(Fluxes::RAROOT, resp_root);
		indiv.report_flux(Fluxes::RAGROWTH, resp_growth);

		if (indiv.pft.lifeform == TREE) {
			indiv.report_flux(Fluxes::GPPTREE, assim);
			indiv.report_flux(Fluxes::RATREE, resp);
		}
		else if (indiv.pft.landcover != CROPLAND) {
			indiv.report_flux(Fluxes::GPPGRASS, assim);
			indiv.report_flux(Fluxes::RAGRASS, resp);
		}

#ifdef CRESCENDO_FACE
		indiv.report_flux(Fluxes::DRALEAF, resp_leaf);
		indiv.report_flux(Fluxes::DRASTEM, resp_sap);
		indiv.report_flux(Fluxes::DRAROOT, resp_root);
		indiv.report_flux(Fluxes::DRAGROWTH, resp_growth);
#endif

		if (indiv.lai_today() > indiv.mlai_max[date.month])
			indiv.mlai_max[date.month] = indiv.lai_today();

		if (day.isend) {
			indiv.mlai[date.month] += indiv.lai_today() / (double)date.ndaymonth[date.month];
		}

		vegetation.nextobj();
	}
}

/// Leaf senescence for crops Eqs. 8,9,13 and 14 in Olin 2015
void leaf_senescence(Vegetation& vegetation) {

	if (!(vegetation.patch.stand.is_true_crop_stand() && ifnlim)) {
		return;
	}

	vegetation.firstobj();
	while (vegetation.isobj) {
		Individual& indiv = vegetation.getobj();

		// Age dependent N retranslocation, Sec. 2.1.3 Olin 2015
		if (indiv.patchpft().cropphen->dev_stage > 1.0) {
			const double senNr = 0.1;
			double senN = senNr * (indiv.nmass_leaf-indiv.cmass_leaf_today() / (indiv.pft.cton_leaf_max));

			// Senescence is not done during spinup
			if (vegetation.patch.stand.get_gridcell().getsimulationyear(date.year) > nyear_spinup && senN > 0) {
				indiv.nmass_leaf -= senN;
				indiv.cropindiv->nmass_agpool += senN;
			}
		}

		double r = 0.0;

		// N dependant C mass loss, with an inertia of 1/10, Eq. 13 Olin 2015
		if (indiv.cmass_leaf_today() > 0.0) {
			double Ln = indiv.lai_nitrogen_today();
			double Lnld = indiv.lai_today();
			r = (Lnld - min(Lnld, Ln))/indiv.pft.sla/10.0;
		}
		// No senescence during the initial growing period
		if (indiv.patchpft().cropphen->fphu < 0.05) {
			indiv.daily_cmass_leafloss = 0.0;
		} else {
			indiv.daily_cmass_leafloss = max(0.0, r);
		}
		indiv.daily_nmass_leafloss = 0.0;

		vegetation.nextobj();
	}
}

/// Forest-floor conditions
/** Called in cohort/individual mode (not population mode) to quantify growth
 *  conditions at the forest floor for each PFT
 *  Calculates net assimilation at top of grass canopy (or at soil surface if
 *  there is none).
 */
void forest_floor_conditions(Patch& patch) {

	const Climate& climate = patch.get_climate();
	double lambda;			// not used here
	PhotosynthesisResult phot;

	for (int p=0; p<npft; p++) {

		Patchpft& ppft = patch.pft[p];
		Standpft& spft = patch.stand.pft[p];
		if (!spft.active) {
			continue;
		}
		Pft& pft = spft.pft;
		// Initialise net photosynthesis sum on first day of year
		if (date.day == 0) {
			ppft.anetps_ff = 0.0;
		}
		if (patch.stand.landcover != CROPLAND || pft.phenology != CROPGREEN && ppft.cropphen->growingseason) {
			double assim = 0;

			if (ppft.wstress_day) {
				assimilation_wstress(pft, climate.co2, climate.temp, climate.par,
					climate.daylength, patch.fpar_grass * ppft.phen, 1., ppft.gcbase_day,
					spft.photosynthesis.vm, phot, lambda, 1.0, false);
				assim = phot.net_assimilation();
			}
			else {
				assim = spft.photosynthesis.net_assimilation() * ppft.phen * patch.fpar_grass;
			}

			// Accumulate annual value
			ppft.anetps_ff += assim;
		}

		if (date.islastmonth && date.islastday) {

			// Avoid negative ppft.anetps_ff
			ppft.anetps_ff = max(0.0, ppft.anetps_ff);

			if (ppft.anetps_ff > spft.anetps_ff_max) {
				spft.anetps_ff_max = ppft.anetps_ff;
			}
		}
	}
}

/// Initiate required variables for the module
void init_canexch(Patch& patch, Climate& climate, Vegetation& vegetation) {

	if (date.day == 0) {
		vegetation.firstobj();
		while (vegetation.isobj) {
			Individual& indiv = vegetation.getobj();

			indiv.anpp           = 0.0;

			indiv.leafndemand    = 0.0;
			indiv.rootndemand    = 0.0;
			indiv.sapndemand     = 0.0;
			indiv.storendemand   = 0.0;
			indiv.hondemand      = 0.0;

			indiv.nday_leafon    = 0;
			indiv.avmaxnlim      = 1.0;
			indiv.cton_leaf_aavr = 0.0;

			if (!negligible(indiv.cmass_leaf) && !negligible(indiv.nmass_leaf))
				indiv.cton_leaf_aopt = indiv.cmass_leaf / indiv.nmass_leaf;
			else
				indiv.cton_leaf_aopt = indiv.pft.cton_leaf_max;

 			for (int m=0; m<12; m++) {
				indiv.mlai[m] = 0.0;
				indiv.mlai_max[m] = 0.0;
				indiv.mgpp[m] = 0.0;
				indiv.mlambda_gpp[m] = 0.0;
			}

			vegetation.nextobj();
		}
	}

	patch.wdemand_day = 0;
}

/// Canopy exchange
/** Vegetation-atmosphere exchange of CO2 and water including calculations
 *  of actual evapotranspiration (AET), canopy conductance, carbon assimilation
 *  and autotrophic respiration.
 *  Should be called each simulation day for each modelled area or patch,
 *  following update of leaf phenology and soil temperature and prior to update
 *  of soil water.
 */
void canopy_exchange(Patch& patch, Climate& climate) {

	// NEW ASSUMPTIONS CONCERNING FPC AND FPAR (Ben Smith 2002-02-20)
	// FPAR = average individual fraction of PAR absorbed on patch basis today,
	//        including effect of current leaf phenology (this differs from previous
	//        versions of LPJ-GUESS in which FPAR was on an FPC basis)
	// FPC =  PFT population (population mode), cohort (cohort mode) or individual
	//        (individual mode) fractional projective cover as a fraction of patch area
	//        (in population mode, corresponds to LPJF variable fpc_grid). Updated
	//        annually based on leaf-out LAI (see function allometry in growth module).
	//        (FPC was previously equal to summed crown area as a fraction of patch
	//        area in cohort/individual mode)

	// Retrieve Vegetation and Climate objects for this patch
	Vegetation& vegetation = patch.vegetation;

	// Initial no-stress canopy exchange processes
	init_canexch(patch, climate, vegetation);

	// Canopy exchange processes
	fpar(patch);

	// Calculates no-stress daily values of photosynthesis and gpterm
	photosynthesis_nostress(patch, climate);

	// Nitrogen demand
	ndemand(patch, vegetation);

	// Nitrogen stress
	vmax_nitrogen_stress(patch, climate, vegetation);

	// Only these processes are affected in diurnal mode
	for (Day day; day.period != date.subdaily; day.next()) {

		wdemand(patch, climate, vegetation, day);
		aet_water_stress(patch, vegetation, day);
		water_scalar(patch, vegetation, day);
		npp(patch, climate, vegetation, day);
	}
	leaf_senescence(vegetation);

	// Forest-floor conditions
	forest_floor_conditions(patch);

	// Total potential evapotranspiration for patch (mm, patch basis)
	// is a sum of: (1) potential transpirative demand of the vegetation;
	// (2) evaporation of canopy-intercepted precipitation; and
	// (3) evaporation from the soil surface of non-vegetated parts of patch -
	//     currently with boleht at 0, a patch has only two surfaces - vegetated
	//     and non-vegetated.
	// This value is only diagnostic, it is not to be used in further calculations.
	// Correct value should use daily value of patch.demand_leafon.
	double pet_patch = patch.wdemand_day * patch.fpc_total + patch.intercep +
				climate.eet * PRIESTLEY_TAYLOR * max(1.0-patch.fpc_total, 0.0);
	patch.apet += pet_patch;
	patch.mpet[date.month] += pet_patch;
	patch.dpet[date.day] += pet_patch;
}

///////////////////////////////////////////////////////////////////////////////////////
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//
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