To test the effect of biodiversity on decomposition and enzyme activities, quaking aspen (Populus tremuloides Michx.) and black spruce (Picea mariana Mill.) litter was inoculated with mixtures of one, two, four, or eight fungi from a pool of 16 fungi that had been isolated from a boreal forest in Alaska. Total CO2 release and the activities of b-glucosidase, which targets cellulose, and polyphenol oxidase, which targets lignin and other recalcitrant phenolic compounds, were observed across the range of species numbers in the mixtures.