In plant litter decomposition, recalcitrant substances such as lignin are either gradually decomposed and completely mineralized or transformed into more complex, recalcitrant forms and stored in soil after rapid initial decay of easily degradable substances such as cellulose. In some of the latter cases, recalcitrant substances as well as nitrogen (N) increase during decomposition with strong correlation, inferring that incorporation of N into the recalcitrant substances. Although the N incorporation would influence N flow in terrestrial ecosystems, the detailed processes remain unknown. Main decomposers of plant litter, fungi, have a wide range of abilities in decomposition of cellulose and lignin, and the fungal communities shift during decomposition processes. Therefore, colonization of fungi with various decomposition ability might influence accumulation of N; that is, some cellulose decomposers causing accumulation of recalcitrant substances might also introduce N to decaying litter. To verify, we will 1) analyze relationships between fungal communities and N concentration in decayed wood and 2) inoculate cellulose decomposers to partially decayed wood and measure changes in N concentration.