I'm out of the habit of critiqueing, so I hope this is helpful.
There's something off about the composition. I think the way you've got it shaded, the pcture should be twice as wide so you could put the sun where it needs to be. There's also an awkward intersection of line to the left where the mountain edge meets the leaves.
You've got something really interesting going on with the choice of color and the sylistic banding around the sun. If you can improve the piece without loosing it, please do. Keep the old version next to the current so we can see how it's improving.
Don't forget, the mountain is going to cast a shadow too.
Things become less saturated the further away they are from the viewer. So with the grass I would pick a much less saturated color for the yellow-green and maybe up the saturation a little near the front so the piece keeps it's vibrancy.
The leaves on the tree look a bit like the're running away from the sun. They're all lined up in neat rows and there is some distinct banding. With both the leaves and the mountain try to break up the shading with the imperfections and details of what you're looking at. Leaves grow in clumps, spreading outward from the branch they're growing from. The mountain is likely to have other ripples in it's surface, a lot like a mound of blankets.
Here's a quick and dirty edit. Not perfect, but hopefully it'll get you thinking in the right direction.
