The Effect of Soil Microbiota on the Growth of Bouteloua Curtipendula

Abstract

Urban grassland fragments provide ecosystem benefits ranging from flood mitigation, carbon sequestration, and promotion of biodiversity. The functionality of urban grassland fragments is dependent upon a rich and diverse native plant community and the absence of exotic plants with fewer ecological connections. When mature, the native prairie grass Bouteloua curtipendula (Michx.) (sideoats grama) can improve the resilience and functionality of urban grasslands by serving as a green mulch, providing habitat while outcompeting seedlings of undesirable plants. Thus, strategies that promote B. curtipendula growth and maturation could improve urban grassland functionality. Little is known about the factors contributing to B. curtipendula germination and early growth, but soil microbial communities have been linked to plant germination, growth, and drought tolerance. In this study, we used sterilized soil to examine the impact of soil microbes on B. curtipendula growth under greenhouse conditions. Bouteloua curtipendula emergence was delayed in sterilized soils, with only 50% of samples emerging by two weeks post-seeding (compared to greater than 90% in non-sterile soils). Also, B. curtipendula grown in sterilized soil grew five fewer blades of grass on average than B. curtipendula grown in unsterilized soil throughout the seven-week experiment. Cumulative grass-blade length in B. curtipendula grown in sterile soil was less than half (10 cm) the length for plants grown in not sterile soil (25 cm), after the first four weeks after seeding. Using high throughput sequencing of the soil, we found B. curtipendula grown in sterilized soil also induced a greater proportion of plant pathogens and nitrifying bacteria compared to B. curtipendula grown in non-sterilized soil. By seven weeks after seeding, B. curtipendula transformed the bacterial community of sterile soil such that it was indiscernible from non-sterile soil. However, fungal communities in sterilized soil were still different from non-sterilized soil seven weeks post-seeding. Last, we found soil sterilization and growth of B. curtipendula changed the relative abundance of metabolic subsystem genes in the soil. Collectively, our findings demonstrate a role of soil microbes on the early growth of B. curtipendula under controlled conditions. In addition, we demonstrate how B. curtipendula growth shapes soil microbial communities. These results may be useful for developing more effective methods for urban grassland installation.