Litter cellulose modulates dissolved organic carbon to drive co-denitrification contribution and nitrous oxide emissions in tea plantation soils

Plant litter constitutes a primary source of soil organic carbon (C) and nutrients in terrestrial ecosystems. Litter chemical composition critically regulates the formation and bioavailability of soil organic C fractions to microorganisms, thereby governing nitrogen (N) transformation processes and nitrous oxide (N 2O) emissions. Nevertheless, the C-N coupling process driven by litter chemistry and its impacts on N 2O emissions have received relatively little attention. Here, we collected litter samples from five >30-year-old tea tree varieties and examined the effects of their litter chemistry on soil organic C fractions, N transformations, and N 2O emission pathways using 15N isotope tracing. Results revealed significant inter-varietal differences in the lignin and cellulose content of their leaf litter. Litter cellulose content positively regulated soil labile C contents, particularly dissolved organic carbon (DOC). Elevated DOC concentrations enhanced nirK + nirS gene abundance and gross NO 3 - consumption rates, amplifying co-denitrification contributions to enhanced N 2O emissions. Soil C-acquiring enzymes involved in cellulose degradation (β-glucosidase and cellobiohydrolase) further stimulated co-denitrification-derived N 2O emissions. Overall, soil DOC emerged as the central driver linking soil C dynamics and N 2O emission pathways. These mechanistic insights significantly advance the predictive modeling of terrestrial N 2O fluxes based on litter chemistry parameters. Furthermore, they enable optimization of N 2O mitigation through precision management of pruning residues in tea plantations.