I am inclined to agree with most people to suggest the rule of thirds, and while I immediately do not know what this image would have looked like with the tree shifted left or right I believe that in this photo it looks best as is. Here is why:
The horizon in low, the angle is shot uphill, the clouds converge towards the bottom and center, and the tree is directly in front of the light source. Even the trees on the horizon sort of taper towards the center. But the main thing I think that I like the most about the photo is that the tree is pretty much dead center of the photo. Not just a little left or right, but to my eye the trunk is centered up almost exact (I say almost because I didn't measure or anything). If it was shifted the sun would have shown brighter and maybe had a negative effect.
I am not saying all this to discount any other opinions, just throwing mine in since I think this image is great along with the rest of you!