There is also the consideration that this whole process is being studied and modeled on a moving platform. The environments that we assumed to be in place when

There is also the consideration that this whole process is being studied and modeled on a moving platform. The environments that we assumed to be in place when we look back and describe these 'ancestral' states are rapidly changing. The timing and duration of rain events, winter snow levels (elevation, depth, duration), high heat events, Santa Ana winds; all of these things are quite rapidly changing their patterns of predictability. Forests are dynamical systems with non-linearity in many of the ways they interact with and respond to the environment. How forests have responded to climate change, to anthropogenic interactions, hunting and extinction of large herbivores (and predators), create feedbacks that further impact how forests (or really, vegetation at large), respond to the environment. I think my point here is that there is questionable utility in trying to run the clock in reverse. Its more important to understand where we're at and how things respond now than it is to contrast them with some ancestral state that is impossible to return to. There's no un-baking the cake. The 'climate' (read: entire earth biosphere), has changed/ is changing.