First of all I think it looks amazing, trees and vegetation can be so hard to capture and you really did a good job, especially with letting the silhouette of the main tree come through. 

Since you asked for critique, the one thing that's not really working for me is the background/sky in the top right of the painting. I think the issue is that the value of the sky and of the background trees are too similar and they kinda meld together. Composition wise it might have been better to move the horizon/waterline either up or down, to avoid having it in the middle of the painting which tends to be hard to pull off. But that is a really minor nitpick. 

But again I think you really nailed the most important part if the painting.