Temporal continuity of habitat strengthens covariation between plant and arbuscular mycorrhizal fungal communities

Old grassland is considered one of the most biodiverse terrestrial ecosystems. The habitat temporal continuity may promote the accumulation of host species and symbiont arbuscular mycorrhizal fungi (AMF) diversity and strengthen symbiont interactions. We tested the hypothesis that covariation between AMF and plant communities is stronger in old grasslands. We compared the relationship between AMF and plant communities in forests and in new and old semi-natural grasslands in Japan. DNA was extracted from bulk roots collected at each site and from roots of Miscanthus sinensis at each grassland site. AMF operational taxonomic unit was characterized on the basis of small subunit rRNA gene sequences. Old grasslands harboured the highest diversity of AMF among vegetation types. The AMF compositions were significantly related to those of plant species. The covariation of plant-AMF communities was stronger in old grasslands than in new grasslands. Individuals of M. sinensis were found to share AMF with bulk roots comprising different species. This suggests that AMF form a common mycorrhizal network among several coexisting plants of different species. Increasing AMF diversity in the shared rhizosphere has been proposed to lead to more efficient utilization of soil nutrients and to increase overall benefits of plant-AMF facilitation.