It's difficult to accurately address your question without a little more information, but I'll take a stab at it. You seem to be asking about the "value of trees" and that can be taken in two ways.
The first has to do with the market value of the standing timber. This is beyond the scope of your practice as a real estate appraiser, but you can certainly call in a professional in the field and get a timber cruze (it can be quite costly - but then, the value of standing timber can be substantial). The fire damage may/may not be significant to the value of the standing timber but the fact that there has been a fire may mean that salvage logging may be the way to recover.
The second has to do with the value of the site for residential use in the upper market tier (assumed not subdividable). This may be a complex assignment (see scope of your license) but does fall into the real estate appraisal bucket. Obviously, the way to determine the impact of the fire damage to a 35 acre high end residential site is to find recent market sales of similar sites-some with fire damage and some without (paired sales). Now we all know that your not going to find 'em. The best you are gonna get is a couple of land sales (if your lucky). Look at those sales very carefully and try to ascertain the amount of forest remaining and make some comparative analysis based on something like the percentage of forest cover remaining/acre and/or view amenity resulting from the diminished forest cover - or something like that.
I still think that I'd get a cruze on this just so as I'd know the economic recovery attributable to the timber/salvage as an off set against any reduction in value for residential use.
But hey, what do I know.......Oregon Doug