title: Impact of Land Use Management and Soil Properties on Denitrifier Communities of Namibian Savannas.
abstract: We studied potential denitrification activity and the underlying denitrifier communities in soils from a semiarid savanna ecosystem of the Kavango region in NE Namibia to help in predicting future changes in N(2)O emissions due to continuing changes of land use in this region. Soil type and land use (pristine, fallow, and cultivated soils) influenced physicochemical characteristics of the soils that are relevant to denitrification activity and N(2)O fluxes from soils and affected potential denitrification activity. Potential denitrification activity was assessed by using the denitrifier enzyme activity (DEA) assay as a proxy for denitrification activity in the soil. Soil type and land use influenced C and N contents of the soils. Pristine soils that had never been cultivated had a particularly high C content. Cultivation reduced soil C content and the abundance of denitrifiers and changed the composition of the denitrifier communities. DEA was strongly and positively correlated with soil C content and was higher in pristine than in fallow or recently cultivated soils. Soil type and the composition of both the nirK- and nirS-type denitrifier communities also influenced DEA. In contrast, other soil characteristics like N content, C:N ratio, and pH did not predict DEA. These findings suggest that due to greater availability of soil organic matter, and hence a more effective N cycling, the natural semiarid grasslands emit more N(2)O than managed lands in Namibia.
authors.affiliation: Max Planck Institute for Terrestrial Microbiology, Marburg, Germany. gbraker@uv.uni-kiel.de.|Kiel University, Kiel, Germany. gbraker@uv.uni-kiel.de.
authors.forename: Gesche
authors.initials: G
authors.lastname: Braker
authors.affiliation: Philipps University, Marburg, Germany.
authors.forename: Diethart
authors.initials: D
authors.lastname: Matthies
authors.affiliation: Max Planck Institute for Terrestrial Microbiology, Marburg, Germany.|LGC Genomics, Berlin, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Hannig
authors.affiliation: Max Planck Institute for Terrestrial Microbiology, Marburg, Germany.
authors.forename: Franziska Barbara
authors.initials: FB
authors.lastname: Brandt
authors.affiliation: Max Planck Institute for Terrestrial Microbiology, Marburg, Germany.
authors.forename: Kristof
authors.initials: K
authors.lastname: Brenzinger
authors.affiliation: Institute of Soil Science, University of Hamburg, Hamburg, Germany.
authors.forename: Alexander
authors.initials: A
authors.lastname: Gröngröft
mesh_terms: D000383:Agriculture / Q000379:methods*; D002244:Carbon / Q000032:analysis; D058440:Denitrification; D017753:Ecosystem; D057075:Enzyme Assays / Q000379:methods; D065948:Grassland; D006863:Hydrogen-Ion Concentration; D059013:Microbial Consortia; D009276:Namibia; D009566:Nitrates / Q000032:analysis; D009584:Nitrogen / Q000032:analysis; D009609:Nitrous Oxide / Q000032:analysis; D012987:Soil / Q000737:chemistry*; D012988:Soil Microbiology; D014867:Water / Q000032:analysis
chemical_list: D009566:Nitrates; D012987:Soil; D014867:Water; D002244:Carbon; D009609:Nitrous Oxide; D009584:Nitrogen
keywords: Abundance; Activity; Community composition; Denitrifiers; Land use; Soil type