Fate of Chinese-fir litter during decomposition as a result of inorganic N additions

• Most litter-C was converted into CO2 during decomposition.
• Litter-C changed the decomposition rate of native soil organic carbon.
• The effects of inorganic N addition on the fates of litter-C depend on the inorganic N form.

We conducted a controlled experiment to evaluate Chinese-fir litter decomposition and its response to the addition of inorganic N. Litter-derived CO2, microbial biomass carbon (MBC), and dissolved organic carbon (DOC) were monitored during an 87-d incubation of a mixed soil–litter substrate using the 13C tracer technique. Litter C was mostly converted to CO2 (47.4% of original mass), followed by MBC (3.6%), and DOC (1.0%), with 48% remaining unaltered in the soil. The litter decomposition rate significantly increased with the addition of inorganic N, although the effect depended on whether N was added as NH4+ or NO3−. Soil-derived CO2, MBC, and DOC also increased following the combined addition of litter and N. The results showed that only a small percentage of litter C was retained as MBC or DOC and that the conversion rate depended, in part, on the form of inorganic N added to the Chinese-fir plantation soil.