Interactive effects of preindustrial, current and future atmospheric CO2 concentrations and temperature on soil fungi associated with two Eucalyptus species

Soil microbial processes have a central role in global fluxes of the key biogenic greenhouse gases and are likely to respond rapidly to climate change. Whether climate change effects on microbial processes lead to a positive or negative feedback for terrestrial ecosystem resilience is unclear. In this study, we investigated the interactive effects of [CO2] and temperature on soil fungi associated with faster-growing Eucalyptus saligna and slower-growing Eucalyptus sideroxylon, and fungi that colonised hyphal in-growth bags. Plants were grown in native soil under controlled soil moisture conditions, while subjecting the above-ground compartment to defined atmospheric conditions differing in CO2 concentrations (290, 400, 650 mu L L-1) and temperature (26 and 30 degrees C). Terminal restriction fragment length polymorphism and sequencing methods were used to examine effects on the structure of the soil fungal communities. There was no significant effect of host plant or [CO2]/temperature treatment on fungal species richness (a diversity); however, there was a significant effect on soil fungal community composition (beta diversity) which was strongly influenced by eucalypt species. Interestingly, beta diversity of soil fungi associated with both eucalypt species was significantly influenced by the elevated [CO2]/high temperature treatment, suggesting that the combination of future predicted levels of atmospheric [CO2] and projected increases in global temperature will significantly alter soil fungal community composition in eucalypt forest ecosystems, independent of eucalypt species composition. These changes may arise through direct effects of changes in [CO2] and temperature on soil fungi or through indirect effects, which is likely the case in this study given the plant-dependent nature of our observations. This study highlights the role of plant species in moderating below-ground responses to future predicted changes to [CO2] and temperature and the importance of considering integrated plantsoil system responses.