Earthworms contribute to carbon and nitrogen cycling directly through the a
ccumulation (consumption), storage (assimilation) and turn over (respiratio
n, excretion, mortality) of nutrients from their tissues. An energetics-bas
ed model was designed to describe the flows of C and N through three compon
ents: litter, earthworm, and byproducts pools. Litter C and N pools contain
ed insoluble nutrients that were consumed by earthworms. A portion of consu
med C and N were assimilated from the earthworm gut and used for growth and
maintenance of earthworm tissue. Earthworm byproducts included C and N def
ecated in earthworm casts as well as C and N released from earthworm tissue
through respiration and excretion. The effect of litter quality, soil temp
erature and soil moisture content on C and N fluxes through earthworms were
simulated. Tissue C accumulation was validated using growth data and N flu
xes were validated with N-15-nitrogen consumption, assimilation and excreti
on data from laboratory studies with Aporrectodea tuberculata (Eisen). Sens
itivity analysis indicated most uncertainty in the function describing the
effect of soil temperature on litter C and N consumption. C and N storage a
nd turn over from earthworm tissues was greatest when the litter C:N ratio
was 10 and declined as the litter C:N ratio increased to 30. Tissue C and N
accumulation was affected strongly by soil temperature and moisture, and o
ptimal conditions for earthworm growth were at 15 degrees C and 30 % (w/w)
soil moisture content. Further work involving the addition of a dynamic pop
ulation structure to the model and validation with data from field studies
is underway to determine the contribution of earthworms to ecosystem-level
fluxes of C and N.