Testing FATES cross grid seed dispersal is activated by enabling the namelist switch option fates_seeddisp_cadence as well as providing reasonable values to the fates parameter file for the following variables: fates_seed_dispersal_fraction fates_seed_dispersal_max_dist fates_seed_dispersal_pdf_scale fates_seed_dispersal_pdf_shape Given that the default fates parameter file has the above variables as unset, a custom fates parameter file must be supplied to appropriately test this mode. This testmod itself addresses CTSM issue 2151: https://github.com/ESCOMP/CTSM/issues/2151 Note that to avoid exceeding the filename string length maximu, the parameter file generated on the fly is placed in the $SRCROOT/src/fates/parameter_files directory. This may still run into problems is the $SRCROOT string is too long. The max_dist value will impact the size of the 'neighborhood' of gridcells that fates will attempt to distribute seeds to. To limit the neighborhood to something tractable for a regression test, the user_nl_clm file points to a specific fates parameter file that was generated to work with a 5x5_amazon resolution. The main downside of this method is that this file will require a custom update for every fates parameter file API update. Addressing CTSM issue #2126 will alleviate this issue as it will provide the capability to build the fates parameter file on the fly which with the appropriate values for this test.