Do spatial simulations change reference conditions?

The reference condition is the expected proportions of reference
vegetation classes per ecological system (hereafter, system) within an
area and has been measured with non-spatial state-and-transition
simulation models (STSM). We aimed to Demonstrate that reference
conditions varied between non-spatial and spatial STSMs from an eastern
Nevada USA landscape. The same STSM database was used to simulate the
non-spatial and spatial reference conditions, except additional input were
added for spatial simulations. The reference condition was obtained from
averaged vegetation class proportions of replicated simulations. Mean fire
return intervals (MFRI) were always shorter in spatial than non-spatial
simulations. The dissimilarity between the spatial and non-spatial
reference conditions was generally higher for smaller systems and those
with long MFRIs (≥ 100 years). Non-spatial and spatial reference
conditions were comparable for large systems with 50-100-year MFRI. The
proportions of older vegetation classes for spatial systems were smaller
for large systems with long MFRIs compared to non-spatial results, but
those proportions were larger for smaller systems with shorter MFRIs
likely because fires can spatially exit small narrow systems. National and
local assessments that use departure from non-spatial reference conditions
to determine vegetation treatments should recognize that spatial
simulations can lead to revisions of treatments decisions.