Well... I don't know if I'd call it a portrait, but that's no matter. This is a well executed thought. I like the time of day you chose for the image. With the sun low in the sky, you're really communicated the texture of the stones while capturing some really wonderful rim lighting on your friend.
The composition is very good. I suspect you might hear some advice about the "rule of thirds," but this is a situation where it doesn't apply. The leading lines formed by the tracks, foliage and horizon all bring you very nicely to the subject. Also, don't that the tracks in the foreground are not centered... there's plenty of semetry goin on.
Congratulations on an impressive image.
-Pete Christie