ESCOMP · mvdebolskiy · Apr 3, 2026 · May 4, 2026 · May 6, 2026 · May 6, 2026
diff --git a/bld/CLMBuildNamelist.pm b/bld/CLMBuildNamelist.pm
@@ -816,7 +816,7 @@ sub setup_cmdl_fates_mode {
     } else {
        # dis-allow fates specific namelist items with non-fates runs
        my @list  = (  "fates_spitfire_mode", "use_fates_planthydro", "use_fates_ed_st3", "use_fates_ed_prescribed_phys",
-                      "use_fates_cohort_age_tracking","use_fates_inventory_init","use_fates_fixed_biogeog",
+                      "use_fates_cohort_age_tracking","use_fates_inventory_init","use_fates_dbh_init","use_fates_fixed_biogeog",
                       "use_fates_nocomp","use_fates_sp","fates_inventory_ctrl_filename","fates_harvest_mode",
                       "fates_parteh_mode","use_fates_tree_damage","fates_seeddisp_cadence","use_fates_luh","fluh_timeseries",
                       "flandusepftdat","use_fates_potentialveg","use_fates_lupft","fates_history_dimlevel",
@@ -4896,7 +4896,7 @@ sub setup_logic_fates {
     if (&value_is_true( $nl_flags->{'use_fates'})  ) {
         add_default($opts, $nl_flags->{'inputdata_rootdir'}, $definition, $defaults, $nl, 'fates_paramfile', 'phys'=>$nl_flags->{'phys'});
         my @list  = (  "use_fates_planthydro", "use_fates_ed_st3", "use_fates_ed_prescribed_phys",
-                       "use_fates_inventory_init","fates_seeddisp_cadence","fates_history_dimlevel",
+                       "use_fates_inventory_init","use_fates_dbh_init","fates_seeddisp_cadence","fates_history_dimlevel",
                        "fates_harvest_mode","fates_parteh_mode", "use_fates_cohort_age_tracking","use_fates_tree_damage",
                        "use_fates_daylength_factor", "fates_photosynth_acclimation", "fates_stomatal_model",
                        "fates_stomatal_assimilation", "fates_leafresp_model", "fates_cstarvation_model",
@@ -4961,6 +4961,10 @@ sub setup_logic_fates {
               }
            }
         }
+        my $var = "use_fates_dbh_init";
+        if ( &value_is_true($nl->get_value($var)) && ( !&value_is_true($nl->get_value("use_fates_nocomp")))) {
+            $log->fatal_error("$var can only be .true. use_fates_nocomp is .true." );
+        }
         # make sure that fates landuse x pft mode has the necessary run mode configurations
         my $var = "use_fates_lupft";
         if ( defined($nl->get_value($var))  ) {

diff --git a/bld/namelist_files/namelist_defaults_ctsm.xml b/bld/namelist_files/namelist_defaults_ctsm.xml
@@ -2715,6 +2715,7 @@ lnd/clm2/surfdata_esmf/NEON/ctsm5.4.0/surfdata_1x1_NEON_TOOL_hist_2000_78pfts_c2
 <use_fates_ed_st3               use_fates=".true.">.false.</use_fates_ed_st3>
 <use_fates_ed_prescribed_phys   use_fates=".true.">.false.</use_fates_ed_prescribed_phys>
 <use_fates_inventory_init       use_fates=".true.">.false.</use_fates_inventory_init>
+<use_fates_dbh_init             use_fates=".true.">.false.</use_fates_dbh_init>
 <use_fates_sp                   use_fates=".true.">.false.</use_fates_sp>
 <use_fates_lupft                use_fates=".true.">.false.</use_fates_lupft>
 <use_fates_potentialveg         use_fates=".true.">.false.</use_fates_potentialveg>

diff --git a/bld/namelist_files/namelist_definition_ctsm.xml b/bld/namelist_files/namelist_definition_ctsm.xml
@@ -881,6 +881,14 @@ Full pathname to the inventory initialization control file.
 (Only relevant if FATES is on).
 </entry>
 
+
+<entry id="use_fates_dbh_init" type="logical" category="physics"
+        group="clm_inparm" valid_values="" value=".false.">
+Initialize cohorts at coldstart with diameter at breast height instead of density
+(Applies only if use_fates_nocomp=.true.)
+(Only relevant if FATES is on).
+</entry>
+
 <entry id="fates_history_dimlevel" type="integer(2)" category="physics"
        group="clm_inparm" valid_values="0,1,2" >
   Setting for what types of FATES history to be allocate and

diff --git a/cime_config/testdefs/testlist_clm.xml b/cime_config/testdefs/testlist_clm.xml
@@ -4104,6 +4104,14 @@
       <option name="wallclock">00:40:00</option>
     </options>
   </test>
+  <test name="ERS_D_Ld10" grid="f45_f45_mg37" compset="I2000Clm50FatesCruRsGs" testmods="clm/FatesColdNoCompInitDbh">
+    <machines>
+      <machine name="derecho" compiler="intel" category="fates"/>
+    </machines>
+    <options>
+      <option name="wallclock">00:40:00</option>
+    </options>
+  </test>
   <test name="SMS_D" grid="1x1_brazil" compset="I2000Clm60FatesSpCruRsGs" testmods="clm/FatesColdSatPhen">
     <machines>
       <machine name="derecho" compiler="intel" category="ctsm_sci"/>

diff --git a/cime_config/testdefs/testmods_dirs/clm/FatesColdNoCompInitDbh/include_user_mods b/cime_config/testdefs/testmods_dirs/clm/FatesColdNoCompInitDbh/include_user_mods
@@ -0,0 +1 @@
+../FatesColdNoComp
diff --git a/cime_config/testdefs/testmods_dirs/clm/FatesColdNoCompInitDbh/shell_commands b/cime_config/testdefs/testmods_dirs/clm/FatesColdNoCompInitDbh/shell_commands
@@ -0,0 +1,10 @@
+SRCDIR=`./xmlquery SRCROOT --value`
+CASEDIR=`./xmlquery CASEROOT --value`
+FATESDIR=$SRCDIR/src/fates/
+FATESPARAMFILE=$CASEDIR/fates_params_init_dbh.json
+
+cp $FATESDIR/parameter_files/fates_params_default.json $FATESPARAMFILE
+
+$FATESDIR/tools/modify_fates_paramfile.py --overwrite --fin $FATESPARAMFILE --param fates_recruit_init_seed --values 0.01 --indices all
+
+echo "fates_paramfile = '$FATESPARAMFILE'" >> $CASEDIR/user_nl_clm
diff --git a/cime_config/testdefs/testmods_dirs/clm/FatesColdNoCompInitDbh/user_nl_clm b/cime_config/testdefs/testmods_dirs/clm/FatesColdNoCompInitDbh/user_nl_clm
@@ -0,0 +1 @@
+use_fates_dbh_init = .true.
diff --git a/src/main/clm_varctl.F90 b/src/main/clm_varctl.F90
@@ -357,6 +357,7 @@ module clm_varctl
   logical, public            :: use_fates_ed_st3   = .false.            ! true => static stand structure
   logical, public            :: use_fates_ed_prescribed_phys = .false.  ! true => prescribed physiology
   logical, public            :: use_fates_inventory_init = .false.      ! true => initialize fates from inventory
+  logical, public            :: use_fates_dbh_init = .false.            ! true => initialize cohorts with dbh instead of density (nocomp only)
   logical, public            :: use_fates_fixed_biogeog = .false.       ! true => use fixed biogeography mode
   logical, public            :: use_fates_nocomp = .false.              ! true => use no comopetition mode
   logical, public            :: use_fates_daylength_factor = .false.    ! true => enable fates to use host land model daylength factor

diff --git a/src/main/controlMod.F90 b/src/main/controlMod.F90
@@ -239,6 +239,7 @@ subroutine control_init(dtime)
           use_fates_cohort_age_tracking,                &
           use_fates_ed_prescribed_phys,                 &
           use_fates_inventory_init,                     &
+          use_fates_dbh_init,                           &
           use_fates_fixed_biogeog,                      &
           use_fates_nocomp,                             &
           use_fates_sp,                                 &
@@ -845,6 +846,7 @@ subroutine control_spmd()
     call mpi_bcast (use_fates_ed_st3, 1, MPI_LOGICAL, 0, mpicom, ier)
     call mpi_bcast (use_fates_ed_prescribed_phys,  1, MPI_LOGICAL, 0, mpicom, ier)
     call mpi_bcast (use_fates_inventory_init, 1, MPI_LOGICAL, 0, mpicom, ier)
+    call mpi_bcast (use_fates_dbh_init, 1, MPI_LOGICAL, 0, mpicom, ier)
     call mpi_bcast (use_fates_fixed_biogeog, 1, MPI_LOGICAL, 0, mpicom, ier)
     call mpi_bcast (use_fates_nocomp, 1, MPI_LOGICAL, 0, mpicom, ier)
     call mpi_bcast (use_fates_sp, 1, MPI_LOGICAL, 0, mpicom, ier)
@@ -1266,6 +1268,7 @@ subroutine control_print ()
        write(iulog, *) '    use_fates_ed_st3 = ',use_fates_ed_st3
        write(iulog, *) '    use_fates_ed_prescribed_phys = ',use_fates_ed_prescribed_phys
        write(iulog, *) '    use_fates_inventory_init = ',use_fates_inventory_init
+       write(iulog, *) '    use_fates_dbh_init = ',use_fates_dbh_init
        write(iulog, *) '    use_fates_fixed_biogeog = ', use_fates_fixed_biogeog
        write(iulog, *) '    use_fates_nocomp = ', use_fates_nocomp
        write(iulog, *) '    use_fates_sp = ', use_fates_sp

diff --git a/src/utils/clmfates_interfaceMod.F90 b/src/utils/clmfates_interfaceMod.F90
@@ -68,6 +68,7 @@ module CLMFatesInterfaceMod
    use clm_varctl        , only : fates_radiation_model
    use clm_varctl        , only : fates_electron_transport_model
    use clm_varctl        , only : use_fates_inventory_init
+   use clm_varctl        , only : use_fates_dbh_init
    use clm_varctl        , only : use_fates_fixed_biogeog
    use clm_varctl        , only : use_fates_nocomp
    use clm_varctl        , only : use_fates_sp
@@ -430,6 +431,7 @@ subroutine CLMFatesGlobals2()
      integer                                        :: pass_ed_prescribed_phys
      integer                                        :: pass_planthydro
      integer                                        :: pass_inventory_init
+     integer                                        :: pass_dbh_init
      integer                                        :: pass_is_restart
      integer                                        :: pass_cohort_age_tracking
      integer                                        :: pass_tree_damage
@@ -674,6 +676,12 @@ subroutine CLMFatesGlobals2()
 
         call set_fates_ctrlparms('inventory_ctrl_file',cval=fates_inventory_ctrl_filename)
 
+        if(use_fates_dbh_init) then
+           pass_dbh_init = 1
+        else
+           pass_dbh_init = 0
+        end if
+        call set_fates_ctrlparms('use_dbh_init',ival=pass_dbh_init)
 
         ! Check through FATES parameters to see if all have been set
         call set_fates_ctrlparms('check_allset')