Maintenance respiration Q10 for C4 grasses (Ryan 1991)

[mpaiao]

I was just checking the Ryan (1991) leaf maintenance respiration subroutine, and I noticed that the reference value at 25°C is calculated from the original reference at 20°C using a Q₁₀ = 1.5

fates/biogeophys/FatesPlantRespPhotosynthMod.F90

Lines 2105 to 2106 in 5551a70

	lmr25top = EDPftvarcon_inst%maintresp_leaf_ryan1991_baserate(ft) * (1.5_r8 ** ((25._r8 - 20._r8)/10._r8))
	lmr25top = lmr25top * lnc_top / (umolC_to_kgC * g_per_kg)

However, when the respiration is calculated for C4 grasses, the actual Q₁₀ used is 2.0:

fates/biogeophys/FatesPlantRespPhotosynthMod.F90

Lines 2121 to 2123 in 5551a70

	! temperature sensitivity of C4 plants
	lmr = lmr25 * 2._r8**((veg_tempk-(tfrz+25._r8))/10._r8)
	lmr = lmr / (1._r8 + exp( 1.3_r8*(veg_tempk-(tfrz+55._r8)) ))

Perhaps we would want to use the same value in both cases? I have the impression this is making the reference respiration to be less than intended for C4 grasses...

[glemieux]

Consensus is to continue to discuss this and come back to it later.