Arbuscular Mycorrhizal Fungi throughout the Year: Using Massively Parallel Pyrosequencing to Quantify Spatiotemporal Seasonal Dynamics

Arbuscular mycorrhizal (AM) fungi represent a ubiquitous functional component of terrestrial ecosystems, playing central roles in nutrient cycling, with significant impacts on plant productivity and diversity. Yet despite their functional importance, AM fungal community ecology remains poorly understood. For example, studies describing the spatiotemporal dynamics of AM fungal communities are scarce, and commonly only quantify AM fungal diversity either temporally or spatially, or exclude sampling across all seasons. Here a study is described, based on (Dumbrell AJ, Gu F, Ashton PD, Aziz N, Nelson M, Dytham C, Fitter AH, Helgason T. Distinct seasonal assemblages of arbuscular mycorrhizal fungi revealed by massively parallel pyrosequencing. New Phytol 2011;190:794–804.), in which the spatiotemporal dynamics of AM fungal communities were investigated over a 1-year period. By using massively parallel pyrosequencing, AM fungi were sampled in a spatially explicit manner from plant roots growing in a temperate grassland throughout a year. Distinct seasonal assemblages of AM fungal species were recorded from winter and summer samples, along with significant changes in community spatiotemporal dynamics. AM fungal α diversity and β diversity between spatial samples were significantly higher in winter, and both α and β diversities were negatively correlated with climate variables that described temperature and sunshine hours. The strong response of AM fungal communities to climate variables known to impact plant growth suggests that seasonal changes in the supply of carbon from host plants, reflecting plant phenology, regulate the temporal dynamics of AM fungal communities. AM fungi gain all their carbon from their host plants and thus any changes in host-plant carbon supply are likely to impact their community dynamics. Thus Dumbrell et al. hypothesized that the diversity and evenness of AM fungal communities is promoted in winter months as reduced host-plant carbon supply produces more even competitive interactions between AM fungal species. These results highlight the potential for significant future changes to AM fungal community dynamics if climate-change effects impact environmental variables regulating the phenology of local host-plant species.