Soil foraging animals alter the composition and co-occurrence of microbial communities in a desert shrubland

Animals that modify their physical environment by foraging in the soil can have dramatic effects on ecosystem functions and processes. We compared bacterial and fungal communities in the foraging pits created by bilbies and burrowing bettongs with undisturbed surface soils dominated by biocrusts. Bacterial communities were characterized by Actinobacteria and Alphaproteobacteria, and fungal communities by Lecanoromycetes and Archaeosporomycetes. The composition of bacterial or fungal communities was not observed to vary between loamy or sandy soils. There were no differences in richness of either bacterial or fungal operational taxonomic units (OTUs) in the soil of young or old foraging pits, or undisturbed soils. Although the bacterial assemblage did not vary among the three microsites, the composition of fungi in undisturbed soils was significantly different from that in old or young foraging pits. Network analysis indicated that a greater number of correlations between bacterial OTUs occurred in undisturbed soils and old pits, whereas a greater number of correlations between fungal OTUs occurred in undisturbed soils. Our study suggests that digging by soil-disturbing animals is likely to create successional shifts in soil microbial and fungal communities, leading to functional shifts associated with the decomposition of organic matter and the fixation of nitrogen. Given the primacy of organic matter decomposition in arid and semi-arid environments, the loss of native soil-foraging animals is likely to impair the ability of these systems to maintain key ecosystem processes such as the mineralization of nitrogen and the breakdown of organic matter, and to recover from disturbance

Partitioning of fungal assemblages across different marine habitats

Fungi are a highly diverse group of microbes that fundamentally influence the biogeochemistry of the biosphere, but we currently know little about the diversity and distribution of fungi in aquatic habitats. Here we describe shifts in marine fungal community composition across different marine habitats, using targeted pyrosequencing of the fungal ITS region. Our results demonstrate strong partitioning of fungal community composition between estuarine, coastal and oceanic samples, with each habitat hosting discrete communities that are controlled by patterns in salinity, temperature, oxygen and nutrients. While estuarine habitats comprised a significant proportion of fungal groups often found in terrestrial habitats, the open ocean sites were dominated by previously unidentified groups. The patterns observed here indicate that fungi are potentially a significant, although largely overlooked, feature of the ocean's microbiota, but greater efforts to characterise marine species are required before the full ecological and biogeochemical importance of marine fungi can be ascertained

Interactive effects of seasonal drought and elevated atmospheric carbon dioxide concentration on prokaryotic rhizosphere communities

Global change models indicate that rainfall patterns are likely to shift towards more extreme events concurrent with increasing atmospheric carbon dioxide concentration ([CO2]). Both changes in [CO2] and rainfall regime are known to impact above- and belowground communities, but the interactive effects of these global change drivers have not been well explored, particularly belowground. In this experimental study, we examined the effects of elevated [CO2] (ambient + 240 ppm; [eCO2]) and changes in rainfall patterns (seasonal drought) on soil microbial communities associated with forest ecosystems. Our results show that bacterial and archaeal communities are highly resistant to seasonal drought under ambient [CO2]. However, substantial taxa specific responses to seasonal drought were observed at [eCO2], suggesting that [eCO2] compromise the resistance of microbial communities to extreme events. Within the microbial community we were able to identify three types of taxa specific responses to drought: tolerance, resilience and sensitivity that contributed to this pattern. All taxa were tolerant to seasonal drought at [aCO2], whereas resilience and sensitivity to seasonal drought were much greater in [eCO2]. These results provide strong evidence that [eCO2] moderates soil microbial community responses to drought in forests, with potential implications for their long-term persistence and ecosystem functioning