Hi,

I actually think that ecological niche modelling for trees can be rather tricky due to the long generation time. It's generally speaking the seeds that experience the selection pressure of changing environments, while the mature trees can endure quite some change in environmental conditions. This might lead to a rather large disconnection between the current environmental conditions and the current distribution of the tree species, for which you would want to correct in some way. The attached paper is not exactly on topic, but might give a feel for what I'm getting at and point you to some interesting reads.