Bug fix in new NGEE Arctic IM3 vegetation parameters

New vegetation parameters in VegStructUpdateMod,
bendresist, vegshape, taper, and stocking (the last two
previously moved to pftvarcon) had been applied to each
column when they are pft specific variables. This commit
changes this such that one value of each parameter is expected
per PFT.

There are use cases where it may be desirable to vary these
at the column level (e.g., if there are not sufficient pfts
to capture things like sagebrush, with an expected bendresist = 1
vs Arctic shrubs, with an expected bendresist of ~0.5), but
this could also be solved by adding pfts.

components/elm/src/biogeochem/VegStructUpdateMod.F90

@@ -161,11 +161,11 @@ subroutine VegStructUpdate(num_soilp, filter_soilp, &
                ! taper and stocking density can be set as input variables now to
                ! change from default values set in pftvarcon.F90
                if (spinup_state >= 1) then
-                 htop(p) = ((3._r8 * deadstemc(p) * spinup_mortality_factor * taper(p) * taper(p))/ &
-                      (SHR_CONST_PI * stocking(p) * dwood(ivt(p))))**(1._r8/3._r8)
+                 htop(p) = ((3._r8 * deadstemc(p) * spinup_mortality_factor * taper(ivt(p)) * taper(ivt(p)))/ &
+                      (SHR_CONST_PI * stocking(ivt(p)) * dwood(ivt(p))))**(1._r8/3._r8)
                else
-                 htop(p) = ((3._r8 * deadstemc(p) * taper(p) * taper(p))/ &
-                      (SHR_CONST_PI * stocking(p) * dwood(ivt(p))))**(1._r8/3._r8)
+                 htop(p) = ((3._r8 * deadstemc(p) * taper(ivt(p)) * taper(ivt(p)))/ &
+                      (SHR_CONST_PI * stocking(ivt(p)) * dwood(ivt(p))))**(1._r8/3._r8)
                end if
 
                ! Peter Thornton, 5/3/2004
@@ -237,7 +237,7 @@ subroutine VegStructUpdate(num_soilp, filter_soilp, &
          ! Liston and Hiemstra, 2011; Belke-Brea et al. 2020
          if (ivt(p) > noveg .and. ivt(p) <= nbrdlf_dcd_brl_shrub ) then
             ol = min( max(snow_depth(c)-hbot(p), 0._r8), htop(p)-hbot(p))
-            fb = 1._r8 - (ol / max(1.e-06_r8, bendresist(p) * (htop(p)-hbot(p)))) ** vegshape(p)
+            fb = 1._r8 - (ol / max(1.e-06_r8, bendresist(ivt(p)) * (htop(p)-hbot(p)))) ** vegshape(ivt(p))
          else
             fb = 1._r8 - max(min(snow_depth(c),0.2_r8),0._r8)/0.2_r8   ! 0.2m is assumed
             !depth of snow required for complete burial of grasses

components/elm/src/main/pftvarcon.F90

@@ -1047,6 +1047,10 @@ subroutine pftconrd
    end do
     call ncd_io('stocking', stocking, 'read', ncid, readvar=readv, posNOTonfile=.true.)
     if (.not. readv ) stocking(:) = 1000._r8
+    ! convert from stems/ha -> stems/m2
+    do i = 0, npft -1
+      stocking(i) = stocking(i) / 10000._r8
+    end do 
     call ncd_io('taper', taper, 'read', ncid, readvar=readv, posNOTonfile=.true.)
     if (.not. readv ) then
       taper(:) = 200._r8