  An easy-plane ferromagnetic spin-1 Bose gas undergoes two
Berezinskii-Kosterlitz-Thouless (BKT) transitions, associated with mass and
spin superfluidity respectively. We study the effect of axial magnetization on
the superfluid properties of this system. We find that nonzero axial
magnetization couples mass and spin superflow, via a mechanism analogous to the
Andreev-Bashkin effect present in two-component superfluids. With sufficiently
large axial magnetization mass and spin superfluidity arise simultaneously. The
cross-over to this phase provides a finite-temperature generalization of the
zero-temperature broken-axisymmetric to easy-axis transition. We present
analytic relations connecting mass and spin superfluidity with experimentally
observable coherence of the three spinor components and local magnetization.
