Litter age interacted with N and P addition to impact soil N2O emissions in Cunninghamia lanceolata plantations

Litter decomposition impacts carbon (C) and nutrient cycling. Nitrogen (N) and phosphorus (P) addition as well as litter age impact litter decomposition. Effects of nutrient addition and litter age on litter decomposition may impact emissions of soil nitrous oxide (N₂O), which is an important greenhouse gas. However, no study has examined the effects of interactions between litter age and nutrient addition on soil N₂O emissions, and explored the underlining mechanisms simultaneously, thus limiting our evaluation of litter decomposition effects on N₂O emissions. Litter with different age was collected from Cunninghamia lanceolata plantations experienced N and P addition treatments to examine the effects of nutrient addition and litter age on N₂O emissions by incubation study. Litter age generally increased N₂O emissions via a decrease in litter C:N ratio. While P addition decreased N₂O emissions, N addition increased them mainly by positive effects on soil enzymes as indicated by microbial functional genes associated with N₂O production and negative effects on litter C:N ratio. Litter age and nutrient addition interacted to impact soil N₂O emissions. In future forest management, both nutrient addition and litter age should be considered in evaluation of management effects on N₂O emissions, especially thinning or selectively cutting involving litter input with different age.