Sequences of tree transformations offer 
a convenient method to describe various 
manipulations that are commonly performed 
by compilers and language-based editors. 
If the considered tree transformations are 
described by certain mappings defined 
on the set of all terms, then sequences 
of tree transformations can be described 
by products of such mappings. 
In this paper we use extensions of 
generalized hypersubstitutions to define 
tree transformations. This allows us to 
describe algebraic properties of sets of 
tree transformations by algebraic properties 
of the set of all generalized hypersubstitutions.