Salem numbers in dynamics of K\"ahler threefolds and complex tori

Let $X$ be a compact K"ahler manifold of dimension $k\le 4$ and $f:X\to X$ a pseudo-automorphism. If the first dynamical degree ${\lambda }_1(f)$ is a Salem number, we show that either ${\lambda }_1(f)={\lambda }_{k-1}(f)$ or ${\lambda }_1(f{)}^2={\lambda }_{k-2}(f)$. In particular, if $dim(X)=3$ then ${\lambda }_1(f)={\lambda }_2(f)$. We use this to show that if $X$ is a complex 3-torus and $f$ is an automorphism of $X$ with ${\lambda }_1(f)>1$, then $f$ has a non-trivial equivariant holomorphic fibration if and only if ${\lambda }_1(f)$ is a Salem number. If $X$ is a complex 3-torus having an automorphism $f$ with ${\lambda }_1(f)={\lambda }_2(f)>1$ but is not a Salem number, then the Picard number of $X$ must be 0,3 or 9, and all these cases can be realized.