Shoot different from a tree?
 

Will a crossbow shoot different from a tree like a compound bow does?

Yes.
(Thats the short answer)

It depends on a lot of things, such as how high up you are in the tree, how steep an angle you are shooting, the range you're shooting at, etc. In my experience, if the shot angle isn't very steep, then the difference in arrow POI isn't very much. But if you're up 20 or 25 feet and shooting at a deer 10 yards away, then yes, it makes a difference. For me, shooting at a steep angle, especially at a close target, the arrow hits high (compared to shooting from the ground).

You really need to practice shooting from a treestand at a target- you may need to adjust your sights a little bit.

How high up you are in the tree makes no difference to the arrows trajectory, as gravity acts on the arrow over its HORIZONAL distance, i.e, from the base of the tree you're in to the target. But height will definitely affect the angle at which the arrow enters, and exits, the target.

If you base your aim on the distance to the target from the base of the tree it makes no difference how high you are in the tree.
Most people use their range finder after they are perched in their stand and the distance noted is further than it would be from the ground. This could make you use the wrong pin, dot, cross hair, etc...

Couldn't be put better.

i second what cossack said