As a major carbon sink, belowground ecosystems have an important role in controlling the carbon flow. Freshly fallen litter is firstly softened by fungi, then fragmented and degraded by fauna, further decomposed by microbes and changed to humus, which stays in the soil for a long time. That is, faunal activities may alter the microbial communities and activities and thus the way of humus formation. However, the effects of fauna on microbes are not yet fully understood. Fauna breaks down litter into small particles, produces faecal pellets, degrades complex compounds and assimilates water-soluble compounds through the gut passage. The questions in this study are 1) how does fauna change litter by grazing and 2) how do the changes affect microbes. Assuming that microbes depend on accessibility of targeting chemical compounds, comparing chemical aspects of litter and faeces of fauna is important. Millipedes are selected as they are one of the most common macrofaunae in coastal forests in BC, Canada. Microcosms with 1) Douglas-fir needles, 2) faeces of millipedes that feed on Douglas-fir litter and 3) mix of needles and faeces are set, and respiratory CO₂ and PLFA are analyzed to determine microbial activities and communities, respectively.