With roots going back to 1978, Badgersett Research Corporation works on bringing "Woody Agriculture" into the mainstream world of full scale staple food production.
From the Badgersett website:
What Is Woody Agriculture?
Woody Agriculture refers to the intensive production of agricultural staple commodities from highly domesticated woody perennial plants. It differs fromagroforestry in that no annual crops are grown, and thus little or no tillage is performed. Permanent stands of the woody crop are established and seeds are harvested annually. Once every 5-10 years the wood is harvested for biomass by coppicing, whereupon the plants regenerate from the roots and resume production of the food crop one year later.