[bocephus]

Im not sure how the Adleman Bank article applies really.
Your basic description sounds sort of like Fangorn Forest without the Treants.

You have to answer a couple questions about your creation "the Self Aware Forest".

1) What does "Aware" mean?

2) How developed is the intellect that is behind the awareness? IE a 3yr old is self aware, as is a 45yr old physicist but anyone could see that they will respond differently to the same stimulus. The Adleman Bank is a "human adult intellect", but its origin is clear and its neurosis are also fairly easy to understand.

2.5) How 'Human' is the intellect? Are its motivations something the PCs are able to understand without misunderstanding it?

3) What is the motivation, if any, of this Forest?

4) Since its trees etc... what scale of time does it operate on? Does it perceive and react as we do, or does it take time for it to realize somethings up before deciding to 'do something'
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Separate to all that, being menacing and unwelcoming to visitors doesn't have to be overt though I'm not sure DFRPG is the correct product for dealing with this design. If you want it to operate as a single cohesive organism with many diverse parts. There are a lot of ways you could do this, though I would struggle to work it into DFRPG except as "this is just the way it is, PCs are not intended to understand it as an NPC but as a sentient landscape".

I think the easiest way to model this is "sentient landscape" and just do what you want.
Figure out the limitations of actions and work from there:

What are its goals, if any?
What is it's actual intelligence?
What is it's awareness of things that are not 'part of it'?

Can any of the trees actually move as singe entities? What is the limitation of the parts?
Can the entity influence minds directly, as in a psychic attack?
Indirectly influence invaders in it's environs: temperature, ambient light, sounds, smells, images?
Physical attacks, via proxy animals or animated plants?
Coordinated awareness, as in fully aware of its options and resources and able to formulate tactical and strategic offense/defense?
Is it like an immune response, just reacting to stimulus like antibodies trying to swarm a perceived threat till the threat seems to be gone?
Is there an intellect that could be negotiated with, how would it communicate, who would it be willing to talk to and under what circumstances?