The Impact of Modifications in Forest Litter Inputs on Soil N2 O Fluxes: A Meta-Analysis

Abstract

Although litter can regulate the global climate by influencing soil N2 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 N2 O fluxes from forests. Overall, our results showed that litter removal significantly reduced soil N2 O fluxes (−19.0%), while a doubling of the amount of litter significantly increased soil N2 O fluxes (30.3%), based on the results of a small number of studies. Litter removal decreased the N2 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 N2 O emissions, which was particularly evident in tropical forest ecosystems. The decreases in soil N2 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 N2 O fluxes from coniferous forests (−21.8%) and broad-leaved forests (−17.2%) but had no significant effect in mixed forests. Soil N2 O fluxes were significantly reduced in experiments where the duration of litter removal was <1 year. These results showed that modifications in ecosystem N2 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.