The other indicator used in determining the ability of the unit to sustain, increase or decrease the deer population comes from an evaluation of the habitat, which is really a measure of the year round deer food supply. That is done by scientifically measuring the amount of regeneration of various tree species that can be eaten by deer within habitat plots. There are five sets of plots in each unit and each set will get evaluated once every five years. If that habitat value drops below 50 % regeneration then that is an indication the habitat is not good and probably not able to support more deer and very likely can’t even sustain the present deer numbers long term. That is also when deer populations are likely to start reducing their own numbers with reduced fawn recruitment rates.
Forest health is not a scientific measure of the year round food supply as you claim and it in no way an accurate measure of the carrying capacity of the habitat. The surveys do not measure the amount of regeneration of various tree species that can be eaten by deer within habitat plots, it measures the regeneration of trees that are capable of replacing the existing canopy species. Therefore, forest health ,as determined by the PGC is not a measure of the health of the habitat or the habitats ability support a given deer density over the long term.
An example of this would be 5C with only 23% regeneration but a reproductive rate of 1.6 embryos/doe compared to 4C with 60% regeneration but only 1.36 embryos/doe. Since 5C is comprised of mixed farm land and wood lots it can support a much higher deer density than 2G and 2G which are 90% forested. But that high deer density will often result in over browsing of the small survey plots used to determine forest health.