  We study the transport properties of a one-dimensional spinful Fermi gas,
after junction of two semi-infinite sub-systems held at different temperatures.
The ensuing dynamics is studied by analysing the space-time profiles of local
observables emerging at large distances $x$ and times $t$, as a function of
$\zeta = x/t$. At equilibrium, the system displays two distinct species of
quasi-particles, naturally associated with different physical degrees of
freedom. By employing the generalised hy- drodynamic approach, we show that
when the temperatures are finite no notion of separation can be attributed to
the quasi-particles. In this case the profiles can not be qualitatively
distinguished by those associated to quasi-particles of a single species that
can form bound states. On the contrary, signatures of separation emerge in the
low-temperature regime, where two distinct characteristic ve- locities appear.
In this regime, we analytically show that the profiles display a piece-wise
constant form and can be understood in terms of two decoupled Luttinger
liquids.
