[Effects of exogenous nitrogen on NO production processes in wetland soils of different restoration phases in the Yellow River estuary].

The effects of exogenous nitrogen on NO production processes in the soils of un-restoration wetland (R), restoration wetland since 2007 (R) and restoration wetland since 2002 (R) of the Yellow River estuary were studied, and the contributions of different processes in NO production were determined. Results showed that the NO production of restoration wetland soils (R and R) with NO-N addition was much higher than that with NH-N addition, but both NH-N and NO-N additions demonstrated inhibition on the NO production of soils in R. Although the effect of NO-N addition on the total NO production of topsoil in R was significantly higher than those in R, the values in R and R were greatly increased with increasing NO-N addition. The denitrification and nitrifier denitrification processes in restoration wetland soils (R and R) were greatly affected by NO-N addition, but no significant influence on the non-biological processes of soil in R was observed. Although NH-N addition did not produce significant effects on the total NO production of wetland soils, the nitrifier denitrification process in R soil, the nitrification process in R soil and the non-biological process in R soil were generally stimulated. In R and R soils, the NO produced by non-biological processes was generally eleva-ted with NH-N addition, while with NO-N addition, the non-biological processes generating NO in R, R and R soils were generally inhibited, which was closely correlated with the regulation of soil pH caused by the import of exogenous nitrogen. This study found that the enrichment of NO-N greatly enhanced the total NO production of wetland soils and significantly altered the original contribution patterns of biological and non-biological processes to NO production. Thus, special attention should be paid on the influences of nutrient import (particularly NO-N enrichment) induced by ecological restoration project on NO production of wetland soils.