In a previous study, creosote bush (Larrea tridentata) fine litter that was buried 5 cm beneath the soil surface in the northern Chihuahuan Desert lost about 20% of the original mass during the following three month summer-autumn period. A mathematical model was devised to elucidate the interactions between litter decay and decomposer microorganisms, using soil moisture and temperature as primary driving variables and litter quality as a controlling factor. Chemical analyses of the litter remaining at various stages of decay now provide additional insight to the decomposition process and another assessment of model behavior. As litter decayed, quantities of soluble and holocellulosic materials decreased by 41% and 22% (respectively), and acid-insolubles increased by 34%. This is consistent with microbially mediated decay processes in which recalcitrant microbial products (e.g., cell wall materials) accumulate as total litter mass decreases. Simulation results were comparable to observed patterns of changing litter chemistry, corroborating a microbial based explanation for decay in desert soils that is very similar to decomposition processes in more mesic temperate ecosystems.