氮负荷增强对冬季闽江河口芦苇湿地土壤N2O产生过程的影响OA北大核心

The typical Phragmites australis marsh in the Minjiang estuary was selected as the study object and a field N load experiment was conducted,which included four N load levels(NN,no N treatment,0 g N m-2 a-1;NL,low N treatment,12.5 g N m-2 a-1;NM,medium N treatment,25 g N m-2 a-1;and NH,high N treatment,75 g N m-2 a-1).The marsh soils were sampled in different N load treatments after 9(December 2021,WT9)and 21 months(December 2022,WT21)of N import and the N2 O production processes of different marsh soils were comparatively assessed through incubation experiments.Results showed that,with increased N loads,the sources of N2 O production varied significantly,with the NM treatment showing the highest total N2 O emissions during both the WT9 and WT21 periods.While the heterotrophic denitrification process significantly reduced N2 O emissions in the soils during the WT9 and WT21 periods,N2 O emissions generally rose with extended N loading durations.Under different N load treatments,the N2 O productions of marsh soils were primarily due to the non-biological process,but its N2 O production generally decreased with increasing N load levels in a short-term period(WT9)and increased in a long-term period(WT21).The higher contributions of non-biological process to N2 O production in different N load treatments mainly depended on the abundant iron(Fe),manganese(Mn)and sulfides in soils and the great alteration of soil pH under enhanced N load conditions.The interactions between N load levels and temperature showed different influences on N2 O production processes in soils of WT9 and WT21 periods.At lower temperature(5.5-11.5℃),the N2 O productions in soils of different N load treatments at WT9 period were mainly dependent on non-biological process,while those at WT21 period were predominated by nitrification and non-biological processes.However,at higher temperatures(17.5℃),the N2 O productions in soils of WT9 and WT21 periods were predominantly governed by non-biological process and nitrifier denitrification process.This study found that enhanced N load altered the original contribution patterns of biological and non-biological processes to soil N2 O production at WT9 and WT21 periods,which mainly influenced the biological or non-biological processes of N2 O production by altering soil nutrient status.Under low temperature and N load conditions in winter in the Minjiang estuary marsh,the interactions between temperature and N enrichment showed an offset effect on soil N2 O production,which was favorable for reducing the N2 O emissions in winter.