fates_mort_hf_sm_threshold default

[pollybuotte]

Recently talking with @ckoven about the need for this parameter to be somewhere in the range of 0.2-0.5. The default parameter file has it at 1e-06. Noting here so it can changed during the next parameter file update.

[ckoven]

We discussed this today, a proposed approach would be to try to calibrate fates_mort_hf_sm_threshold values in the default parameter file, in tandem with related parameters fates_nonhydro_smpsc and fates_mort_scalar_hydrfailure, as part of the calibration cascade approach, specifically after the SP and initial nocomp calibration rungs of the cascade, and calibrated against observations and remote sensing products of PFT distributions etc, in order to get the climate effects on mortality rates working in the default parameterization.