Investors are buying up vast tracts of timberland across U.S. in one of market's longest-term bets

When the economy and the market look shaky, gold and government bonds are the traditional places to park money. Lately, some investors have also been looking at something more rooted: timber. 

The pitch is easy to like: a back-to-basics, natural asset that grows on its own, matures into a harvest and can be cashed in all while you use it to hunt, pitch a tent, or forage.