Different responses of soil CO2 and N2O emissions to simulated N deposition in forests with divergent N transformation characteristics

CO₂ and N₂O are important greenhouse gases that are related to soil mineralization–immobilization turnover and nitrification. To explore the responses of CO₂ and N₂O emissions to N deposition in forests with different N transformation characteristics, CO₂ and N₂O fluxes were measured in two NH₄NO₃ fertilized plots. One plot was in a temperate pine plantation in Heilongjiang Liangshui National Nature Reserve (LS) with slow and minimally coupled mineralization–immobilization turnover and a high nitrification rate. The other plot was in a subtropical bamboo forest in the Fujian Daiyun Mountain National Nature Reserve (DY) in China with rapid and coupled mineralization–immobilization turnover but a low nitrification rate. The results showed that CO₂ emissions in the DY with a high mineralization rate were greater than those in the LS. Cumulative CO₂ emissions were significantly enhanced by N addition in DY, but in LS, they were not affected. The mean N₂O fluxes in the control were 0.010 and 0.008 mg N m^?2 hr^?1 for LS and DY, respectively. High N addition stimulated N₂O emissions in both LS and DY, but the response ratio for N₂O flux in LS (8.6) was larger than that in DY (2.9). These results suggested that soils with rapid and coupled mineralization–immobilization turnover are beneficial to CO₂ emissions and their positive response to N deposition. A high nitrification rate contributed to high N₂O emissions and the sensitive response of N₂O emissions to N deposition.