ctsm5.4.039

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Tag name: ctsm5.4.039
Originator(s): mvdebolskiy (Matvey Debolskiy, University of Oslo, matvey.d...@geo.uio.no)
Date: Thu May 14 01:07:45 PM MDT 2026
One-line Summary: Add FATES namelist option to initialize cohorts with diameter at breast height (DBH)

Purpose and description of changes
----------------------------------

FATES allows for the ability to initialize seedling by density or DBH. Prior to this change,
the user would update the `fates_recruit_init_density` parameter to use a negative value to
initalize by DBH. This pull request removes this global switch behavior and creates a namelist
option for the user. The FATES parameter file and behavior has been updated to include a new
parameter for users to set the initial DBH by plant functional type.

Notes of particular relevance for users
---------------------------------------

Changes to CTSM's user interface (e.g., new/renamed XML or namelist variables):
New namelist option to control FATES:
use_fates_dbh_init

Changes made to namelist defaults (e.g., changed parameter values):
Sets the default for use_fates_dbh_init to false

Changes to the parameter file (output of tools/param_utils/compare_paramfiles):
Adds fates_recruit_init_dbh to the FATES parameter file

Notes of particular relevance for developers:
---------------------------------------------

Caveats for developers (e.g., code that is duplicated that requires double maintenance):
- Note that this option currently is only applicable with use_fates_nocomp

Changes to tests or testing:
Added test module FatesColdNoCompInitDbh

Testing summary:
----------------

build-namelist tests (if CLMBuildNamelist.pm has changed):

derecho - OK (2 expected fails)

regular tests (aux_clm: https://github.com/ESCOMP/CTSM/wiki/System-Testing-Guide#pre-merge-system-testing):

derecho ----- OK
izumi ------- OK

fates tests: (baseline comparison against fates-sci.1.92.4_api.45.0.0-ctsm5.4.037)
derecho ----- OK
izumi ------- OK

Answer changes
--------------

Changes answers relative to baseline: No

Other details
-------------

List any git submodules updated (cime, rtm, mosart, cism, fates, etc.):
fates: sci.1.92.4_api.45.0.0 -> sci.1.92.5_api.46.0.0

Pull Requests that document the changes (include PR ids):
(https://github.com/ESCOMP/ctsm/pull)
https://github.com/ESCOMP/CTSM/pull/3910
https://github.com/NGEET/fates/pull/1550

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