Re: What is the role of decomposers in the Subtropical Rainforest ecosystem?

I think you have already answered your own question. One of the important 
things about the ecosystem concept is that like a play, the actors may 
change, but the functional roles of producers, consumers, and decomposers 
stay the same.  Decomposers in a subtropical rainforest will be the same 
group of organisms, fungi & bacteria, utilizing the organic molecules that 
remain after organisms die, and in the process, returning mineral nutrients 
to the biosphere.

There may be some differences in the timing of this process depending upon 
the particular circumstances of an ecosystem.  Deciduous forests usually 
have a season of leaf fall caused by either cold or dry seasons followed by 
a burst of decomposer activity.  Tropical evergreen forests have more of a 
steady recycling.  Perhaps some such seasonality plays a role in Australian 
subtropical rainforests.  But you can be certain that the same type of 
organisms will have essentially the same function.  So unless you have 
missed something or misunderstood your assignment, you have the answer to 
your question.