  For a two-qubit state the isotropic strength measures the degree of isotropic
spin correlation. The concept of isotropic strength is generalized to
multipartite qudit systems, and the strength distributions for tripartite and
quadripartite qudit systems are thoroughly investigated. We show that the sum
of relative isotropic strengths of any three qudit state over $d$-dimensional
Hilbert space cannot exceed $d-1$, which generalizes of the case $d=2$. The
trade-off relations and monogamy-like relations of the sum of spin correlation
strengths for pure three- and four-partite systems are derived. Moreover, the
bounds of spin correlation strengths among different subsystems of a
quadripartite state are used to analyze quantum entanglement.
