title: Climate change amplifies gross nitrogen turnover in montane grasslands of Central Europe in both summer and winter seasons.
abstract: The carbon- and nitrogen-rich soils of montane grasslands are exposed to above-average warming and to altered precipitation patterns as a result of global change. To investigate the consequences of climatic change for soil nitrogen turnover, we translocated intact plant-soil mesocosms along an elevational gradient, resulting in an increase of the mean annual temperature by approx. 2 °C while decreasing precipitation from approx. 1500 to 1000 mm. Following three years of equilibration, we monitored the dynamics of gross nitrogen turnover and ammonia-oxidizing bacteria (AOB) and archaea (AOA) in soils over an entire year. Gross nitrogen turnover and gene levels of AOB and AOA showed pronounced seasonal dynamics. Both summer and winter periods equally contributed to cumulative annual N turnover. However, highest gross N turnover and abundance of ammonia oxidizers were observed in frozen soil of the climate change site, likely due to physical liberation of organic substrates and their rapid turnover in the unfrozen soil water film. This effect was not observed at the control site, where soil freezing did not occur due to a significant insulating snowpack. Climate change conditions accelerated gross nitrogen mineralization by 250% on average. Increased N mineralization significantly stimulated gross nitrification by AOB rather than by AOA. However, climate change impacts were restricted to the 2-6 cm topsoil and rarely occurred at 12-16 cm depth, where generally much lower N turnover was observed. Our study shows that significant mineralization pulses occur under changing climate, which is likely to result in soil organic matter losses with their associated negative impacts on key soil functions. We also show that N cycling processes in frozen soil can be hot moments for N turnover and thus are of paramount importance for understanding seasonal patterns, annual sum of N turnover and possible climate change feedbacks.
authors.affiliation: Institute of Meteorology and Climate Research, Atmospheric Environmental Research (IMK-IFU), Karlsruhe Institute of Technology (KIT), Garmisch-Partenkirchen, 82467, Germany.|State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, The Chinese Academy of Sciences (IBCAS), Beijing, 100093, China.
authors.forename: Changhui
authors.initials: C
authors.lastname: Wang
authors.affiliation: Institute of Meteorology and Climate Research, Atmospheric Environmental Research (IMK-IFU), Karlsruhe Institute of Technology (KIT), Garmisch-Partenkirchen, 82467, Germany.
authors.forename: Zhe
authors.initials: Z
authors.lastname: Chen
authors.affiliation: Institute of Meteorology and Climate Research, Atmospheric Environmental Research (IMK-IFU), Karlsruhe Institute of Technology (KIT), Garmisch-Partenkirchen, 82467, Germany.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Unteregelsbacher
authors.affiliation: Institute of Meteorology and Climate Research, Atmospheric Environmental Research (IMK-IFU), Karlsruhe Institute of Technology (KIT), Garmisch-Partenkirchen, 82467, Germany.
authors.forename: Haiyan
authors.initials: H
authors.lastname: Lu
authors.affiliation: Research Unit Environmental Genomics, German Research Center for Environmental Health (GmbH), 85764, Neuherberg, Germany.
authors.forename: Silvia
authors.initials: S
authors.lastname: Gschwendtner
authors.affiliation: Institute of Meteorology and Climate Research, Atmospheric Environmental Research (IMK-IFU), Karlsruhe Institute of Technology (KIT), Garmisch-Partenkirchen, 82467, Germany.
authors.forename: Rainer
authors.initials: R
authors.lastname: Gasche
authors.affiliation: Institute of Meteorology and Climate Research, Atmospheric Environmental Research (IMK-IFU), Karlsruhe Institute of Technology (KIT), Garmisch-Partenkirchen, 82467, Germany.
authors.forename: Allison
authors.initials: A
authors.lastname: Kolar
authors.affiliation: Research Unit Environmental Genomics, German Research Center for Environmental Health (GmbH), 85764, Neuherberg, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Schloter
authors.affiliation: Institute of Meteorology and Climate Research, Atmospheric Environmental Research (IMK-IFU), Karlsruhe Institute of Technology (KIT), Garmisch-Partenkirchen, 82467, Germany.
authors.forename: Ralf
authors.initials: R
authors.lastname: Kiese
authors.affiliation: Institute of Meteorology and Climate Research, Atmospheric Environmental Research (IMK-IFU), Karlsruhe Institute of Technology (KIT), Garmisch-Partenkirchen, 82467, Germany.
authors.forename: Klaus
authors.initials: K
authors.lastname: Butterbach-Bahl
authors.affiliation: Institute of Meteorology and Climate Research, Atmospheric Environmental Research (IMK-IFU), Karlsruhe Institute of Technology (KIT), Garmisch-Partenkirchen, 82467, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Dannenmann
mesh_terms: D001105:Archaea; D001419:Bacteria; D057231:Climate Change; D005060:Europe; D065948:Grassland; D009584:Nitrogen; D010084:Oxidation-Reduction; D012621:Seasons; D012987:Soil; D012988:Soil Microbiology
chemical_list: D012987:Soil; D009584:Nitrogen
keywords: ammonia-oxidizing archaea; ammonia-oxidizing bacteria; freeze-thaw; frozen soil; gross N mineralization; gross nitrification; montane grassland