Different spatial structure of plant-associated fungal communities above- and belowground

Background/Question/Methods

Microorganisms affect plants in diverse ways. Nonetheless, the distribution and community assembly of microorganisms associated with individual plants above- and belowground remains poorly understood. Depending on how microbial communities are structured, we can expect different effects of the microbial community on the health of individual plants and on ecosystem processes. To examine the effect of environmental factors and dispersal on the distribution of fungal communities, we sampled leaves and soil of Quercus robur trees, as well as microclimatic, phenological and spatial variables, in a landscape in southwestern Finland. To test for environmental filtering of microbial communities, we recorded temperature, relative humidity and tree autumn phenology at the tree level. To examine the impact of microbial dispersal between individual oak trees, we recorded the spatial connectivity of the trees.

Results/Conclusions

The majority of variation in the foliar fungal community was found within trees, whereas soil fungal community composition showed positive spatial autocorrelation up to 50 m. Microclimate, tree phenology and tree spatial connectivity explained little variation in the foliar and soil fungal communities. Overall, foliar and soil fungal communities differed strongly in terms of community structure, with no link found between above- and belowground communities. These contrasts point to a different role of individual processes in the assembly of microbial communities above- and belowground. Synthesis. We provide evidence that foliar and soil fungal communities assemble independent of each other and are structured by different ecological processes. Our findings contribute to our understanding of below- and aboveground microbial communities, plant–microbe interactions and plant population dynamics.