1) a correction - standard PAR at Harvard is consistent with frequent J limitation *requires further examination.
2) If we calculate J with low light, photosynthesis is always J limited - Wj is always lower than Wc
Weighting J by PAR from Harvard (above canopy)
Mid to lower canopy
Full Harvard record provides a range of realistic PAR values
Calculating J using Jmax from Griffen pers comm and
J = (jmax +PhiPAR - sqrt((jmax+PhiPAR)^2-4thetajmaxPhiPAR))/2*theta
Equation 1(a) from Walker 2014 modified from Farquhar and Wong 1984
Results in this response curve:
Canopy light study from Harvard Forest (David Foster)
Driving equation 1(a) Results in the following J calculations
This is summarized here:
Most of the time ... it's dark
if you think about it isotopically ... most of the signal should be made up from periods when photosynthesis is actually happening ... at really low light, the overall isotopic signal is probably not being changed.
I'll need to think about how to deal with this
Completed
1) a correction - standard PAR at Harvard is consistent with frequent J limitation *requires further examination. 2) If we calculate J with low light, photosynthesis is always J limited - Wj is always lower than Wc
Weighting J by PAR from Harvard (above canopy)
Mid to lower canopy
Full Harvard record provides a range of realistic PAR values Calculating J using Jmax from Griffen pers comm and J = (jmax +PhiPAR - sqrt((jmax+PhiPAR)^2-4thetajmaxPhiPAR))/2*theta
Equation 1(a) from Walker 2014 modified from Farquhar and Wong 1984
Canopy light study from Harvard Forest (David Foster)
Driving equation 1(a) Results in the following J calculations
This is summarized here:
Most of the time ... it's dark
if you think about it isotopically ... most of the signal should be made up from periods when photosynthesis is actually happening ... at really low light, the overall isotopic signal is probably not being changed. I'll need to think about how to deal with this