Managed peatlands are a significant source of nitrous oxide(N_(2)O),a powerful greenhouse gas and stratospheric ozone depleter.Due to the complexity and diversity of microbial N_(2)O processes,different methods such a...Managed peatlands are a significant source of nitrous oxide(N_(2)O),a powerful greenhouse gas and stratospheric ozone depleter.Due to the complexity and diversity of microbial N_(2)O processes,different methods such as tracer,isotopomer,and microbiological technologies are required to understand these processes.The combined application of different methods helps to precisely estimate these processes,which is crucial for the future management of drained peatlands,and to mitigate soil degradation and negative atmospheric impact.In this study,we investigated N_(2)O sources by combining tracer,isotopomer,and microbial analysis in a drained peatland forest under flooded and drained treatments.On average,the nitrification genes showed higher abundances in the drained treatment,and the denitrification genes showed higher abundances in the flooded treatment.This is consistent with the underlying chemistry,as nitrification requires oxygen while denitrification is anaerobic.We observed significant differences in labelled N_(2)O fluxes between the drained and flooded treatments.The emissions of N_(2)O from the flooded treatment were nearly negligible,whereas the N_(2)O evolved from the nitrogen-15(^(15)N)-labelled ammonium(^(15)NH4+)in the drained treatment peaked at 147μg ^(15)N m^(-2) h^(-1).This initially suggested nitrification as the driving mechanism behind N_(2)O fluxes in drained peatlands,but based on the genetic data,isotopic analysis,and N_(2)O mass enrichment,we conclude that hybrid N_(2)O formation involving ammonia oxidation was the main source of N_(2)O emissions in the drained treatment.Based on the ^(15)N-labelled nitrate(^(15)NO3-)tracer addition and gene copy numbers,the low N_(2)O emissions in the flooded treatment came possibly from complete denitrification producing inert dinitrogen.At atomic level,we observed selective enrichment of mass 45 of N_(2)O molecule under ^(15)NH4+amendment in the drained treatment and enrichment of both masses 45 and 46 under ^(15)NO3-amendment in the flooded treatment.The selective enrichment of mass 45 in the drained treatment indicated the presence of hybrid N_(2)O formation,which was also supported by the high abundances of archaeal genes.展开更多
基金supported by the Ministry of Education and Science of Estonia(No.SF0180127s08)the Estonian Research Council(Nos.IUT2-16,PRG-352,and MOBERC20)+1 种基金the European Union through the European Regional Development Fund(Estonian EcolChange Centre of Excellence,Estonia,and MOBTP101 returning researcher grant by the Mobilitas Pluss programme)the European Social Fund(Doctoral School of Earth Sciences and Ecology).
文摘Managed peatlands are a significant source of nitrous oxide(N_(2)O),a powerful greenhouse gas and stratospheric ozone depleter.Due to the complexity and diversity of microbial N_(2)O processes,different methods such as tracer,isotopomer,and microbiological technologies are required to understand these processes.The combined application of different methods helps to precisely estimate these processes,which is crucial for the future management of drained peatlands,and to mitigate soil degradation and negative atmospheric impact.In this study,we investigated N_(2)O sources by combining tracer,isotopomer,and microbial analysis in a drained peatland forest under flooded and drained treatments.On average,the nitrification genes showed higher abundances in the drained treatment,and the denitrification genes showed higher abundances in the flooded treatment.This is consistent with the underlying chemistry,as nitrification requires oxygen while denitrification is anaerobic.We observed significant differences in labelled N_(2)O fluxes between the drained and flooded treatments.The emissions of N_(2)O from the flooded treatment were nearly negligible,whereas the N_(2)O evolved from the nitrogen-15(^(15)N)-labelled ammonium(^(15)NH4+)in the drained treatment peaked at 147μg ^(15)N m^(-2) h^(-1).This initially suggested nitrification as the driving mechanism behind N_(2)O fluxes in drained peatlands,but based on the genetic data,isotopic analysis,and N_(2)O mass enrichment,we conclude that hybrid N_(2)O formation involving ammonia oxidation was the main source of N_(2)O emissions in the drained treatment.Based on the ^(15)N-labelled nitrate(^(15)NO3-)tracer addition and gene copy numbers,the low N_(2)O emissions in the flooded treatment came possibly from complete denitrification producing inert dinitrogen.At atomic level,we observed selective enrichment of mass 45 of N_(2)O molecule under ^(15)NH4+amendment in the drained treatment and enrichment of both masses 45 and 46 under ^(15)NO3-amendment in the flooded treatment.The selective enrichment of mass 45 in the drained treatment indicated the presence of hybrid N_(2)O formation,which was also supported by the high abundances of archaeal genes.
