Remove `site%area_bareground` based area scaling calcuation in history interface module

[glemieux]

Discussed in #1375

^{Originally posted by glemieux April 1, 2025}
In the history interface module we have an area scaling calculation that I think should be changed:

fates/main/FatesHistoryInterfaceMod.F90

Lines 4990 to 4999 in 0f321cd

	if (hlm_use_nocomp .eq. itrue .and. hlm_use_fixed_biogeog .eq. itrue) then
	site_area_veg_inv = area - sites(s)%area_bareground * area
	else
	site_area_veg_inv = 0._r8
	cpatch => sites(s)%oldest_patch
	do while(associated(cpatch))
	site_area_veg_inv = site_area_veg_inv + cpatch%total_canopy_area
	cpatch => cpatch%younger
	end do !patch loop
	end if

@ckoven the site_area_veg_inv here was initially used to scale only the instantaneous tveg (via #877). That said, I think the scaling that uses the patch%total_canopy_area site summation in the else block is more correct for fbg+nocomp mode as well. Is that correct to you?

Background

I noticed that there is one place in the history interface module in which we check if we are in FBG + Nocomp mode to determine how to calculate an area scaling variable site_area_veg_inv for use in the update_history_hifreq1 subroutine:

fates/main/FatesHistoryInterfaceMod.F90

Lines 4990 to 4992 in 0f321cd

	if (hlm_use_nocomp .eq. itrue .and. hlm_use_fixed_biogeog .eq. itrue) then
	site_area_veg_inv = area - sites(s)%area_bareground * area
	else

This jumped out at me as I didn't see a similar check in the companion update_history_hifreq2 subroutine in which we calculate the same scaling:

fates/main/FatesHistoryInterfaceMod.F90

Lines 5185 to 5195 in 0f321cd

	site_area_veg_inv = 0._r8
	cpatch => sites(s)%oldest_patch
	do while(associated(cpatch))
	site_area_veg_inv = site_area_veg_inv + cpatch%total_canopy_area
	cpatch => cpatch%younger
	end do !patch loop
	! If there is no vegetation, go to the next site
	if(site_area_veg_inv < nearzero) cycle do_sites
	site_area_veg_inv = 1._r8/site_area_veg_inv

This scaling value came in initially as site_area_veg to address #861 via #877. @rgknox had originally removed the FBG+nocomp check and restructured the scaling as the summation of the patch%total_canopy_area via #1119, but due to a later merge deconflict between this (now on main) and #1116 the check made its way back in.