The single tree is ok imo. It's just the view that is wrong; makes the tree look wrong, because it's too marginal in the picture. Same goes for the horizon.
Don't lose the edge of that hill. Get the sun over to the foot of the hill, get the tree slightly more centered. Too much emptiness in the right side of the picture, but the tree wouldn't fit there. Maybe some more objects, like a person or a tree stump ^.
Don't know how the clouds could be fixed, but looks pretty good anyway. Nice, make more!