Changes in the microbial community structure of bacteria, archaea and fungi in response to elevated CO 2 and warming in an A ustralian native grassland soil

Abstract

Summary The microbial community structure of bacteria, archaea and fungi is described in an Australian native grassland soil after more than 5 years exposure to different atmospheric CO 2 concentrations ([ CO 2 ]) (ambient, + 550 ppm) and temperatures (ambient, + 2°C) under different plant functional types ( C 3 and C 4 grasses) and at two soil depths (0–5 cm and 5–10 cm). Archaeal community diversity was influenced by elevated [ CO 2 ], while under warming archaeal 16S rRNA gene copy numbers increased for C 4 plant T hemeda triandra and decreased for the C 3 plant community ( P CO 2 ], elevated [ CO 2 ] plus warming and ambient [ CO 2 ]. Overall bacterial community diversity was influenced primarily by depth. Specific bacterial taxa changed in richness and relative abundance in response to climate change factors when assessed by a high‐resolution 16 S rRNA microarray ( PhyloChip ). Operational taxonomic unit signal intensities increased under elevated [ CO 2 ] for both F irmicutes and B acteroidetes, and increased under warming for A ctinobacteria and A lphaproteobacteria. For the interaction of elevated [ CO 2 ] and warming there were 103 significant operational taxonomic units ( P CO 2 ] plus warming plots, while abundance declined in warmed or elevated [ CO 2 ] plots. Bacterial abundance (16 S rRNA gene copy number) was significantly different for the interaction of elevated [ CO 2 ] and depth ( P CO 2 ] at 5–10 cm, and for Firmicutes under elevated [ CO 2 ] ( P CO 2 ], warming and their interaction. Taxa identified as significantly climate‐responsive could show differing trends in the direction of response (‘+’ or ‘−’) under elevated CO 2 or warming, which could then not be used to predict their interactive effects supporting the need to investigate interactive effects for climate change. The approach of focusing on specific taxonomic groups provides greater potential for understanding complex microbial community changes in ecosystems under climate change.

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