Poster Presentation Australian Microbial Ecology 2019

Microbial variations: Relationships between biogeochemistry, community composition and function across a 900 km aridity gradient (#148)

Mark Farrell 1 2 , Paul Dennis 3 , Jessica Ernakovich 4 , Jeff Baldock 1 , Francesca McInerney 5 , Stefan Caddy-Retalic 5 , Athina Puccini 1 , P A Hall 5 , Tom Carter 1 , Ian Waite 2 , Daniel Murphy 2 , Andrew Lowe 5 , Andrew Whiteley 2
  1. CSIRO, Glen Osmond, SA, Australia
  2. The University of Western Australia, Perth
  3. The University of Queensland, Brisbane
  4. The University of New Hampshire, Durham
  5. The University of Adelaide, Adelaide

Multiple soil functions will be affected by climate change, both through direct changes to the composition of soil microbial communities through changed rainfall and increased temperatures, and indirect and longer term changes to the composition and structure of associated vegetation communities. This study examined soil samples taken from 42 sites along a 900 km transect established under the Terrestrial Ecosystem Research Network (TERN) in South Australia. Microbial communities were analysed for community structure using 16S, 18S and ITS Illumina amplicon sequencing, and also by PLFA analysis to provide robust information on microbial community structure at time of sampling. To investigate microbial activity, rates of glucose mineralisation were quantified using 14C-labelling approaches, and stable isotope probing using 13C-glucose was conducted to identify the structure of the active microbial community. Beyond microbial measurements, comprehensive analysis of soil biogeochemistry including litter and soil organic matter chemistry by NMR was conducted. Combined with vegetation community structure and climatic information, these data were then analysed using multivariate statistical approaches to understand the strengths of relationships between vegetation, climatic, soil and microbial variability along the transect. We found that aridity, rather than SOM chemistry was the major driver, with bacteria and archaea (16S sequences) being influenced to a greater extent than fungi (ρ = 0.764 and ρ = 0.454 respectively, both P ≤ 0.001). Though there was no relationship between fungal community structure and SOM chemistry, bacterial and archaeal community structure was also influenced by SOM chemistry (ρ = 0.269, P ≤ 0.001). Ongoing work, particularly the finalisation of the 13C-SIP activity, will help elucidate linkages between these datasets and their functional role in the environment.