  The evolution of an initial perturbation in Vlasov plasma is studied in the
intrinsically nonlinear long-time limit dominated by the effects of particle
trapping. After the possible transient linear exponential Landau damping, the
evolution enters into a universal regime with an algebraically damped electric
field, $E\propto1/t$. The trick used for the Vlasov equation is also applied to
the two-dimensional (2D) Euler equation. It is shown that the stream function
perturbation to a stable shear flow decays as $t^{-5/2}$ in the long-time
limit. These results imply a strong non-ergodicity of the fluid element motion,
which invalidates Gibbs-ensemble-based statistical theories of Vlasov and 2D
fluid turbulence.
