how to draw a food chain including decomposer and detritivore? (biology/science)?

[JunoJuliet]

i know how to draw up a simple food chain with
producer-consumer1-consumer2-consumer3
but how do i include decomposers and detritivores??
all the research ive been doing online, basicly comes up with models like this:
http://alaska.fws.gov/fire/role/unit1/images/I-6.jpg
how does that work???
im working with forest animals here, like leaves, squirrels, bears etc
help??!?!?!?!