First I want to say that I love your landscape pieces; I really want to start trying to put atmospheres like this together, myself. The tree is very real looking with the peeking branches and the different levels of light give the appearance of a full, leafy tree, despite the fact that you haven't gone through and tried to draw every individual leaf. The color scheme and glowy lighting are great.
I feel like the size and shape of the canvas in conjunction with the shape and positioning of the tree make this feel a bit plain. The leafy part of the tree is far too much of a focus on the piece. With the vertical lines of the tall rocks, and with the rocks obstructing our view in the foreground, a portrait-shaped canvas might accentuate the piece a bit better. The free-standing pillars of rock are daunting and important, and the mimicking of their general shape would give more of a balance to the entire piece. If you did wantto stick with a landscape shaped piece, though, a simple rule of thirds could possibly do. One last little thing is that empty space below the tree roots is (the orange triangle at the bottom of the canvas.) It seems as if roots and vines might be hanging here, a bit, or perhaps that the edge of the rocks here are too straight; something more organic might be more appropriate.