Very large tree LAI values exceeding values that are possible from allometry parameters

[adamhb]

Hi all,

I am seeing large lai values that are maxing out the vai bins, as per this known issue 420. However, my "target lai" values at the time of model failure are below the vai bin limit (as seen in error output below). My slamax is set to always equal slatop and I've checked that allometry parameters (for sla and crown area) can't produce a tree lai above the max limit. So something is causing the actual tree lai to get above the target tree lai.

The erroneously high lai is being calculated within a call to tree_sai [here] (https://github.com/NGEET/fates/blob/main/biogeochem/EDCanopyStructureMod.F90#L2250). I am using a leaf biomass allometry that caps leaf biomass at the max height dbh, which is why target leaf biomass can never be too high. Possibly related is that something caused this cohort to get impossibly large (dbh of 388.8) in the short simulation time that this happened.

Could this be an issue with cohort fusion or forcing the dbh up? The value for leaf biomass that is used to produce the erroneously high lai value is pulled directly from the parteh object here and therefore isn't a value calculated allometrically (via bleaf), so it could therefore be erroneously high.

I am looking for some guidance on where I might be able to make a quick fix to the code to ensure that tree lai does not exceed the max, even in cases where fusion (or other model glitches?) (temporarily?) creates an erroneously large cohort.

Error output:

The leaf and stem are predicted for a cohort, maxed out the array size
lai: 56.2625005997680 (tree lai)
sai: 2.14597762874742
lai+sai: 58.4084782285155
target_bleaf: 88.9363631555620
area: 1.67565509481413 (crown area m2)
target_lai: 21.4597762874742
dinc_vai: 1.00000000000000 1.00000000000000
1.00000000000000 1.00000000000000 1.00000000000000
1.00000000000000 1.00000000000000 1.00000000000000
1.00000000000000 1.00000000000000 1.00000000000000
1.00000000000000 1.00000000000000 1.00000000000000
1.00000000000000 1.00000000000000 1.00000000000000
1.00000000000000 1.00000000000000 1.00000000000000
1.00000000000000 1.00000000000000 1.00000000000000
1.00000000000000 1.00000000000000 1.00000000000000
1.00000000000000 1.00000000000000 1.00000000000000
1.00000000000000 1.00000000000000 1.00000000000000
1.00000000000000 1.00000000000000 1.00000000000000
1.00000000000000 1.00000000000000 1.00000000000000
1.00000000000000 1.00000000000000 1.00000000000000
1.00000000000000 1.00000000000000 1.00000000000000
1.00000000000000 1.00000000000000 1.00000000000000
1.00000000000000 1.00000000000000 1.00000000000000
nlevleaf,sum(dinc_vai): 50 50.0000000000000
pft: 2
call id: 4
n: 2.449486331399154E-002
dbh: 388.807317493043 dbh_max: 90.0000000000000
h: 40.4608723797214
canopy_trim: 1.02667296028433
canopy layer: 1
canopy_tlai: 1.365349092384639E-003 0.000000000000000E+000
vcmax25top: 38.6464525343923
ENDRUN:
ERROR in FatesAllometryMod.F90 at line 800