Computation of the light use efficiency following Van Oijen et al. (2010), used in CAF2007 model.

LUE_Van_Oijen_et_al._2010.R

LUE= function(CO2A,Tair,PAR,K,RUBISC){
  # CO2A in ppm
  # Tair in degC
  # PAR in MJ PAR m-2 ground d-1
  # K in m2 ground m-2 leaf
  # RUBISC in g Rubisco m-2 leaf
  
  EAVCMX = 68000 # (J mol-1)
  EAKMC  = 65800 # (J mol-1)
  EAKMO  = 1400  # (J mol-1)
  JMUMOL = 4.56  # (mol quanta MJ-1 PAR)
  KC25   = 138   # (g CO2 g-1 Rubisco d-1)
  KMC25  = 460   # (ppm CO2)
  KMO25  = 33    # (% O2)
  KOKC   = 0.21  # (-)
  O2     = 21    # (% O2)
  R      = 8.314 # (J K-1 mol-1)
  CO2I   = 0.7 * CO2A # (ppm CO2)
  VCMAX  = RUBISC * KC25 * exp((1/298-1/(Tair+273))*EAVCMX/R) # (g CO2 m-2 leaf d-1)
  KMC    = KMC25 * exp((1/298-1/(Tair+273))*EAKMC /R) # (ppm CO2)
  KMO    = KMO25 * exp((1/298-1/(Tair+273))*EAKMO /R) # (% O2)
  GAMMAX = 0.5 * KOKC * KMC * O2 / KMO             # (ppm CO2)
  PMAX   = VCMAX * (CO2I-GAMMAX) / (CO2I + KMC * (1+O2/KMO))  # (g CO2 m-2 leaf d-1)
  EFF    = 44 * JMUMOL/2.1 * (CO2I-GAMMAX)/ (4.5*CO2I+10.5*GAMMAX) # (g CO2 MJ-1 PAR)
  LUE    = EFF * PMAX / (EFF*K*PAR + PMAX) # (g CO2 MJ-1 PAR)
  return(LUE)
}