I'd worry about trip planning and preparation, first aid, orienteering, things like that, before what roots you can safely nibble on.
IMO, the most important survival skill is not getting into a survival situation to begin with.
A real survival scenario also has a precipitating event-which means that your situation abruptly changes. That is usually going to be an injury, or becoming lost, but could be anything that puts you out beyond your planned time or in unforeseen conditions, like drastic changes in the weather, for instance. A dayhike where someone sets out with plans to be back the same day(and is thinking short-term, with minimal preparation) is probably how the vast majority of these survival stories begin. Then they get stuck out overnight, hurt or in bad weather, without adequate clothing, shelter, or water.
We need to think in terms of what can change, how to avoid it, and how to cope with it if it happens. Think injury, exposure, and dehydration.
If you want to see someone who spends a lot of time outdoors and is practically prepared without carrying a bunch of useless stuff, search for posts by "mtwarden" and look at his replies and pics in threads asking what people carry. For example, this post in a thread about what people carry on dayhikes:
http://www.bladeforums.com/forums/showpost.php?p=9299039&postcount=2
Just remember to tailor what you carry to your own environment...