Does o-Substitution Preserve Recognizability?

Substitution operations on tree series are at the basis of systems of equations (over tree series) and tree series transducers. Tree series transducers seem to be an interesting transformation device in syntactic pattern matching. In this contribution, it is shown that o-substitution preserves recognizable tree series provided that the target tree series is linear and the semiring is idempotent, commutative, and continuous. This result is applied to prove that the range of the o-t-ts transformation computed by a linear recognizable tree series transducer is pointwise recognizable.