Anything that's natural is hard to create with LEGO, and tree roots are no exception. Despite this, David Zambito has managed to capture their shape and nature well with a great selection of reddish brown technic and feeler pieces.
David has also chosen his MOC well, as the vertical design lends itself to show the roots protruding from the cliffside, and this shows off the technique perfectly.
Check out his post on Flickr here: https://www.flickr.com/photos/137705513@N02/28187591107/in/feed