Yeah it's a well composed picture. Professional photographers
   know where the "gravity" of a photograph should be and where
   there should be less of it. Considering how long this type of
   composition has been used in photography, there's no way to
   really know if we weren't just trained to see this as balanced.
   Ye ol' nature/nature stuff. In the OP, though, I see a diagonal.
   Bottom right , upper left. Something interesting in lower right
   hand half, something interesting in upper left hand half. But I
   tend to split things down the diagonal anyway.