Scale eind dynamically based on climate-driven relative abundance

[kpalmqui]

Currently the maximum number of individuals that can establish in each year is fixed. To represent geographic differences in plant functional type abundance, eind will now vary across sites and climate scenarios and will be set dynamically based on a site's climate and the climate-derived relative abundance of each plant functional type derived in function estimate_STEPWAT_relativeVegAbundance in rSFSTEP2.

Proposed implementation:

1. Define a new flag to determine whether this implementation is used or not.
2. Define max eind for each plant functional type.
3. Use relative abundance (0 to 1) to re-scale max eind:

if rel abun > 0 {
max  eind * relative abundance }

4. Write new derived eind value into species.in using similar workflow in place already for writing climate-derived space value in rgroup.in (contained in Main.R).

[kpalmqui]

For annual species, min eind will also be defined, which represents the minimum number of individuals for annual species biomass to be > 0.

Proposed implementation:

if rel abun > 0 {
relative abundance * (max eind - min eind) + min eind
}

This implementation will distinguish species that have relative abundance = 0 from those that have a very small relative abundance. Thus all species with relative abundance > 0 will be simulated.