The exposure of the left portion is right on. Unless you took two identical shots, one darker than this one, that you could then combine with this one in an HDR program, or, if you were shooting in RAW mode, I think you are stuck with trying to work with this shot (which is not too shabby, by the way!). If it were mine, I would try some careful cloning of areas/objects that are nicely-exposed, onto the brighter areas/objects. It would be picky work, though -- one sprig of evergreen at a time, for example. If you try using a darkening tool selectively, white areas will just turn gray, not the brown and green colors you are seeking.
Well, I think that I have the "bugs" out of this computer. I am using a new (to me) version of PE3 thanks for waiting & I'll try and post more often now. ;-)
Steve