What do I like about this shot;
-Great idea with the "shadow". Makes it very interesting.
-Saw that some people didn't like the brown sky - IMHO, I like it. Nice contrast with the tree.
What I would've changed;
-The trees in the background is distracting. Maybe a bit more DOF would've worked well here.
-Bump up the sharpness on the tree and shadow a bit. This will also help to create depth in the image.
Great image and surely deserving to be amaongst your top 4 challenge entries.
The 'shadow' really makes this stand out from the other 'tree photos' good choice, I hope people dont dismiss it as 'just another tree shot', I really like. Good luck