Is the q10_mr parameter used for both soil HR and plant MR? Should it be?

[linniahawkins]

From my reading of the code it seems like the q10_mr parameter is used by both heterotrophic respiration in Century AND plant maintenance respiration (stem, coarse root, fine root, but not leaf).

Is this as intended? Would it be appropriate to separate into two independent parameters?

Note: this is also how q10_mr is used in FATES.

[wwieder]

Thanks for creating this issue, @linniahawkins.

@olyson can you look into this?
@linniahawkins can you clarify what q10 value you expected the soil / plant values to actually use of the parameter file?
Out of curriosity, what are these set to in the latest paramter file(s)?

[olyson]

Thanks for creating this issue, @linniahawkins.

@olyson can you look into this? @linniahawkins can you clarify what q10 value you expected the soil / plant values to actually use of the parameter file? Out of curriosity, what are these set to in the latest paramter file(s)?

I can't speak as to whether they should be different, but the code does seem to indicate that q10_mr is used for both calculations. Although for soil it looks like there is some kind of normalization done for the temperature scalar:

     if ( normalize_q10_to_century_tfunc ) then
         ! scale all decomposition rates by a constant to compensate for offset between original CENTURY temp func and Q10
         normalization_factor = (catanf(normalization_tref)/catanf_30) / (q10**((normalization_tref-25._r8)/10._r8))
         do j = 1, nlevdecomp
            do fc = 1,num_bgc_soilc
               c = filter_bgc_soilc(fc)
               t_scalar(c,j) = t_scalar(c,j) * normalization_factor
            end do
         end do
      endif

The t_scalar on the right was previously calculated as:

           do j = 1, nlevdecomp
               do fc = 1,num_bgc_soilc
                  c = filter_bgc_soilc(fc)
                  if (t_soisno(c,j) >= SHR_CONST_TKFRZ) then
                     t_scalar(c,j)= (Q10**((t_soisno(c,j)-(SHR_CONST_TKFRZ+25._r8))/10._r8))
                  else
                     t_scalar(c,j)= (Q10**(-25._r8/10._r8))*(froz_q10**((t_soisno(c,j)-SHR_CONST_TKFRZ)/10._r8))
                  endif
               end do
            end do

The current value of q10_mr in the CLM6 parameter file is 1.5.

[linniahawkins]

Thanks Keith.

I raised this issue simply because I was misinterpreting the q10_mr parameter, assuming it only varied maintenance respiration (given the name). Charlie made an off-hand comment about the naming convention a couple years ago which stuck with me but I only recently looked into it.

We did not calibrate this parameter for CLM6 so it is still set to 1.5 as in CLM5.

However, for parameter uncertainty questions it could be useful to vary the Q10 for maintenance respiration and heterotrophic respiration independently. And I think the observational uncertainty bounds on these two parameters would likely be different.

This isn't my area of expertise (given that I really don't have one at all) but is there a reason the HR and MR Q10's should be coupled @ckoven ?