Understanding how soil microbial communities assemble has important applications to ecosystem processes. In agroecosystems, this is especially important for communities of arbuscular mycorrhizal fungi (AMF). AMF are ancient symbionts that associate with the majority of land plants, including major crops, providing essential nutrients (e.g. phosphorus and nitrogen) in exchange for photosynthetically-fixed carbon. Further, AMF also contribute a range of benefits to agroecosystems, including drought tolerance, pathogen protection, and improved soil structure. As such, AMF are key components of agricultural ecosystem functioning and sustainability. AMF taxa also differ life history strategies and provisioning of ecosystem functions and services and the diversity of AMF taxa has been associated with increasing aboveground diversity. In agricultural systems, simplification (e.g. monocropping) may decrease AMF diversity whereas diversification (e.g. intercropping) may increase AMF diversity with important implications for ecosystem functioning. Therefore, elucidating the drivers of AMF community assembly in agricultural systems is important to direct management decisions on farms. Here, we explore how on-farm diversification will impact AMF community assembly across scales. We sampled root zone soil of individual crop plants (n=12) on each farm (15 polyculture and 15 monoculture farms) to compare how AMF community assembly within a farm (fine spatial scale) and between farms (landscape scale) was influenced by polyculture versus monoculture farming. We identified AMF community composition using next generation sequencing on the fungal DNA barcode and measured edaphic variables of each soil sample plus calculated geographic distance between samples within and across farms. We then applied generalized dissimilarity modelling to test whether AMF communities were structured by farm management practices, edaphic variables, or geographic distance.
Results/Conclusions
Our preliminary results provide evidence that niche and neutral processes both contribute to community assembly of AMF across farms (landscape scale) and within farms (fine spatial scale). We found evidence that pH as well as crop diversity primarily drive AMF community composition. While these findings are only preliminary, our results provide further support that pH may play a central role in the assembly of all soil mediated systems, including agroecosystems. Further, the results presented here on AMF community assembly in agricultural soils, from fine spatial to landscape scale, could have important implications for agricultural management decisions.