Abstract
Soil N2O emission and denitrification in the wetland( water level drawdown) area of reservoirs are critical pathways in the N biogeochemistry cycles. The intact soil core-acetylene inhibition technique was applied to investigate the N2 O emission and denitrification rates on grass land,cultivated area and background group in Lake Gaoyang drawdown area of Pengxi River,a tributary in the Three Gorges Reservoir,from March to April in 2013. Environmental impact factors,e. g. p H,oxidation-reduction potential,temperature,organic matter,total nitrogen,ammonium nitrogen,nitrate nitrogen and water-filled pore space,were measured simultaneously. The grass land had a mean N2 O emission rate of 9. 88 ± 6. 49 g N /( ha·d),and a mean denitrification rate of 58. 94 ± 52. 84 g N /( ha·d). The mean N2 O emission rate and denitrification rate of cultivated area were 7. 71 ± 4. 44 g N /( ha·d) and 30. 70 ± 25. 68 g N/( ha·d),respectively. The difference of N2 O emission rate in different land use types was significant. The N2 O emission and denitrification processes were greatly affected by the soil oxygen content,water content and nitrogen content of soils. An increase in soil oxygen content stimulated the N2 O emission in grass area and inhibited the denitrification process in a certain extent. Larger water content in the cultivated area,comparing with that in the grass area,probably lead to a smaller N2 O emission rate. Soil nitrogen content had a positive relationship with the decline of denitrification rate in the drawdown area.
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