Functions of mycorrhizhosphere communities under the influence of different nitrogen and water regimes in forest soils
Final Report Abstract
Climate change will lead to more extreme weather events, including severe drought periods and intense drying rewetting cycles. This may directly influence microbial nitrogen (N) turnover rates in soil by changing the water content and the oxygen partial pressure. Therefore in the frame of the project, a space for time climate change experiment was conducted by transferring intact beech seedling-soil mesocosms from a northwest (NW) exposed site, representing today's climatic conditions, to a southwest (SW) exposed site, providing a model climate for future conditions with naturally occurring increased soil temperature (+0.8°C in average). In addition, severe drought and intense rainfall was simulated by a rainout shelter at SW and manual rewetting after 39 days drought, respectively. Soil samples were taken in June, at the end of the drought period (August), 24 and 72 hours after rewetting (August) and after a regeneration period of four weeks (September). To follow dynamics of bacterial and archaeal communities involved in N turnover, abundance and activity of nitrifiers, denitrifiers, N2 fixing microbes and N-mineralizers were analyzed based on marker genes and the related transcripts by qPCR from DNA and RNA directly extracted from soil. Abundance of the transcripts was reduced under climate change with most pronounced effects for denitrification. Our results revealed that already a transfer from NW to SW without further treatment resulted in decreased cnor and nosZ transcripts, encoding for nitric oxide reductase and nitrous oxide reductase, respectively, while nirK transcripts, encoding for nitrite reductase, remained unaffected. Severe drought additionally led to reduced nirK and cnor transcripts at SW. After rewetting, nirK transcripts increased rapidly at both sites, while cnor and nosZ transcripts increased only at NW. Further climate changes also induces enhanced CO2 concentrations in the atmosphere. In order to gain insight into short-term, site-specific effects of eCO2 on the microbial community structure at the plant-soil interface, young beech trees (Fagus sylvatica L.) from two opposing mountainous slopes with contrasting climatic conditions were incubated under ambient (360 ppm) CO2 concentrations in a greenhouse. One week before harvest, half of the trees were incubated for 2 days under eCO2 (1,100 ppm) conditions. Shifts in the microbial community structure in the adhering soil as well as in the root rhizosphere complex (RRC) were investigated via TRFLP and 454 pyrosequencing based on 16S ribosomal RNA (rRNA) genes. Multivariate analysis of the community profiles showed clear changes of microbial community structure between plants grown under ambient and elevated CO2 mainly in RRC. Both TRFLP and 454 pyrosequencing showed a significant decrease in the microbial diversity and evenness as a response of CO2 enrichment. While Alphaproteobacteria dominated by Rhizobiales decreased at eCO2, Betaproteobacteria, mainly Burkholderiales, remained unaffected. In contrast, Gammaproteobacteria and Deltaproteobacteria, predominated by Pseudomonadales and Myxococcales, respectively, increased at eCO2. Members of the order Actinomycetales increased, whereas within the phylum Acidobacteria subgroup Gp1 decreased, and the subgroups Gp4 and Gp6 increased under atmospheric CO2 enrichment. Moreover, Planctomycetes and Firmicutes, mainly members of Bacilli, increased under eCO2. Overall, the effect intensity of eCO2 on soil microbial communities was dependent on the distance to the roots.
Publications
- Climate Change Induces Shifts in Abundance and Activity Pattern of Bacteria and Archaea Catalyzing Major Transformation Steps in Nitrogen Turnover in a Soil from a Mid-European Beech Forest. PLoS ONE 9(12): e114278, 2014
Silvia Gschwendtner, Javier Tejedor, Carolin Bimüller, Ingrid Kögel Knabner, Michael Dannenmann and Michael Schloter
(See online at https://doi.org/10.1371/journal.pone.0114278) - Decoupled carbon and nitrogen mineralization in soil particle size fractions of a forest topsoil. Soil Biology and Biochemistry Volume 78, November 2014, Pages 263-273
Carolin Bimüller, Carsten W. Mueller, Margit von Lützow, Olivia Kreyling, Angelika Kölbl, Stephan Haug, Michael Schloter and Ingrid Kögel-Knabner
(See online at https://doi.org/10.1016/j.soilbio.2014.08.001) - Effects of elevated atmospheric CO 2 on microbial community structure at the plant-soil interface of young beech trees (Fagus sylvatica L.) grown at two sites with contrasting climatic conditions. Microbial ecology 69 (4), 867-878, 2015
Silvia Gschwendtner, Martin Leberecht, Marion Engel, Susanne Kublik, Michael Dannenmann, Andrea Polle and Michael Schloter
(See online at https://doi.org/10.1007/s00248-014-0527-x) - Relationships between denitrification gene expression, dissimilatory nitrate reduction to ammonium and nitrous oxide and dinitrogen production in montane grassland soils. Soil Biology and Biochemistry
Volume 87, August 2015, Pages 67-77
Zhe Chen, Changhui Wang, Silvia Gschwendtner, Georg Willibald, Sebastian Unteregelsbacher, Haiyan Lu, Allison Kolar, Michael Schloter, Klaus Butterbach-Bahl and Michael Dannenmann
(See online at https://doi.org/10.1016/j.soilbio.2015.03.030) - Climate change impairs nitrogen cycling in European beech forests. PLoS ONE 11(7): e0158823, 2016
Michael Dannenmann, Carolin Bimüller, Silvia Gschwendtner, Martin Leberecht, Javier Tejedor, Silvija Bilela, Rainer Gasche, Marc Hanewinkel, Andri Baltensweiler, Ingrid Kögel-Knabner, Andrea Polle, Michael Schloter, Judy Simon, Heinz Rennenberg
(See online at https://doi.org/10.1371/journal.pone.0158823)
