Responses of soil nitrogen cycling to changes in aboveground plant litter inputs: A meta-analysis

Alterations in aboveground plant litter inputs due to global climate change can strongly change soil nitrogen (N) cycling, which will influence soil processes and functions. However, a comprehensive evaluation for the effects of altered litter inputs on soil N cycling is not available. We evaluated these effects using a global meta-analysis based on 1829 observations from 119 studies across different ecosystems including forests, shrublands and grasslands. Results showed that litter addition significantly increased soil N pools including total N (TN), dissolved organic N (DON), ammonium (NH4+), nitrate (NO3-) and microbial biomass N (MBN) by 4---24 %, while litter removal decreased them by 10---42 %. High initial soil TN pool weakened the positive effect of litter addition on soil TN. Moreover, litter addition significantly increased soil net N mineralization (+19 %), DON leaching (+56 %) and nitrous oxide (N2O) emission (+27 %), whereas litter removal reduced net N mineralization (-10 %) and increased NO3- leaching (+51 %). The response of soil net N mineralization to litter addition was stronger in broadleaved forests than that in coniferous forests, and negatively correlated with mean annual temperature and precipitation. The responses of soil TN, NH4+, NO3-, MBN and N2O emission to litter manipulation increased with increasing litter input rates. Therefore, altered litter inputs had strong effects on soil N cycling and these effects were regulated by soil N status, ecosystems, climates and experimental conditions. Our results provide insights into understanding how altered plant litter input affects soil N cycling and help better assess the soil processes under global climate change.

Automated summary

Alterations in aboveground plant litter inputs due to global climate change can strongly affect soil nitrogen cycling, soil processes, and functions. Litter addition significantly increased soil nitrogen pools, while litter removal decreased them. Litter addition also increased soil net nitrogen mineralization, dissolved organic nitrogen leaching, and nitrous oxide emission, while litter removal reduced net nitrogen mineralization and increased nitrate leaching. The response of soil nitrogen cycling to litter manipulation was influenced by soil nitrogen status, ecosystems, climates, and experimental conditions.