From my old physical meteorology class, walk around the tree and see where the "steam" (it's actually condensed water vapor) is actually visible. Most atmospheric particles are forward scatterers. That means you can "see" their effects more easily when you are looking at them as light is passing through them (looking towards or into the direction of the sun). I think the moisture "cloud" would disappear if you walked on the other side of the tree and looked in the direction the light is heading. Any light from the reflection in that position would be back scattered.

So if you took a video walking around the tree, the light from the condensed water vapor would be more apparent from the position of your photograph versus the other side (looking in the direction of the sunlight).