bstracting a landscape presents it's own unique challenges. Unless there are man-made objects present in the landscape, my favorite system of abstraction, mulitple viewpoint perspect (MVP), is pretty useless.
 
With MVP I view my subject from multiple directions (front, back, side, top, bottom, etc.) and then represent all these various points of view, at the same time in a composite construction, like in my painting, Left to the Village, below. Study a tree, river or rock formation from all sides, then composite the information together in a single image and the viewer won't see what you've done. Trees, rivers and rock formations come in all shapes and sizes, so any MVP abstraction I come up with looks like elements in their natural state. Abstracting a landscape requires utilization of other systems of abstraction (geometric abstraction, organic abstraction, reductive abstraction, etc.).