| Summary: | Although litter can regulate the global climate by influencing soil N<sub>2</sub>O fluxes, there is no consensus on the major drivers or their relative importance and how these impact at the global scale. In this paper, we conducted a meta-analysis of 21 global studies to quantify the impact of litter removal and litter doubling on soil N<sub>2</sub>O fluxes from forests. Overall, our results showed that litter removal significantly reduced soil N<sub>2</sub>O fluxes (−19.0%), while a doubling of the amount of litter significantly increased soil N<sub>2</sub>O fluxes (30.3%), based on the results of a small number of studies. Litter removal decreased the N<sub>2</sub>O fluxes from tropical forest and temperate forest. The warmer the climate, the greater the soil acidity, and the larger the soil C:N ratio, the greater the impact on N<sub>2</sub>O emissions, which was particularly evident in tropical forest ecosystems. The decreases in soil N<sub>2</sub>O fluxes associated with litter removal were greater in acid soils (pH < 6.5) or soils with a C:N > 15. Litter removal decreased soil N<sub>2</sub>O fluxes from coniferous forests (−21.8%) and broad-leaved forests (−17.2%) but had no significant effect in mixed forests. Soil N<sub>2</sub>O fluxes were significantly reduced in experiments where the duration of litter removal was <1 year. These results showed that modifications in ecosystem N<sub>2</sub>O fluxes due to changes in the ground litter vary with forest type and need to be considered when evaluating current and future greenhouse gas budgets.
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