[Nitrification-denitrification and N2O emission of typical Calamagrostis angustifolia wetland soils in Sanjiang plain].

With intact soil core and by using acetylene inhibition method, this paper measured the N2O emission and denitrification rates of typical Calamagrostis angustifolia wetland soils in Sanjiang Plain, analyzed their relationships with environmental factors, and estimated the total amounts of N2O emission and denitrification loss. The results showed that meadow marsh soil and humus marsh soil had a similar change range of N2O emission rate (0.020-0.089 kg N x hm(2) x d(-1) and 0.012-0.033 kg N x hm(2) x d(-1), respectively), but the former had a much higher N2O emission rate than the latter, and the difference was significant (P < 0.05). As for denitrification rate, its change range was 0.024-0.127 kg N x hm(2) x d(-1) for meadow marsh soil and 0.021-0.043 kg N x hm(2) x d(-1) for humus marsh soil. Meadow marsh soil also had a higher denitrification rate than humus marsh soil, but the difference was not significant (P > 0.05). In meadow marsh soil, nitrification played an important role in N2O emission and nitrogen loss; while in humus marsh soil, denitrification was the main process inducing N2O emission and nitrogen loss. For these two soils, nitrogenous compounds were not the important factor affecting nitrification-denitrification. In meadow marsh soil, temperature had more evident effect, where nitrification-denitrification had a significant positive correlation with the soil temperature at the depths of 5 cm, 10 cm and 15 cm (P < 0.05). Soil moisture condition was another important factor inducing the difference of N2O emission and denitrification rates. In growth season, the amount of N2O emission and denitrification loss was 5.216 kg N x hm(-2) and 6.166 kg N x hm(-2) for meadow marsh soil, and 3.196 kg N x hm(-2) and 4.407 kg N x hm(-2) for humus marsh soil, respectively. In the denitrification productions of meadow marsh soil and humus marsh soil, the maximum value of N2O/N2 ratio was 5.49 and 3.76, respectively, indicating that the proportion of N2 in denitrification productions was higher in humus marsh soil than in meadow marsh soil, and the seasonal waterlogged condition could induce the decrease of N2O/N2 ratio.