  A novel and generic understanding of spontaneous generation of transport
barriers and zonation regimes in turbulent self-organization is presented. It
associates the barrier onset to the development of a spectral gap between large
scale flows and turbulence modes leading to a zonation regime. A robust barrier
builds-up at the interface of such a region and a neighboring one with reduced
zonal flow generation. This more complex and generic transition paradigm could
fit the numerous and sometimes conflicting observations as in fusion plasma
experiments. Barrier relaxation by bursts of turbulence regenerate the zonal
flows that are eroded by viscous (collisional-like) damping. The duration of
the quiescent phase between the quasi-periodic relaxation events is governed by
this damping process, hence the barrier collision frequency for fusion plasmas.
