Do happy roots make blue stems? Influence of land use practices on soil microbial communities and their benefits for a widespread prairie plant, Schizachyrium scoparium

Background/Question/Methods

Ecological restorations maintain natural resources for human health, mitigate climate change and provide habitat for ecosystem services. In central Missouri, land managers focus on reconstructing agricultural land to prairie. Soil microbes, such as arbuscular mycorrhizal fungi (AMF), support prairie plant communities by facilitating nutrient uptake and community succession, but reconstructions are managed without consideration of plant-microbe relationships. We conducted a common garden experiment to explore how provisioning little bluestem with soil inoculum from agricultural, reconstruction, and remnant prairie influences vegetative growth, flowering and AMF diversity. Soils were collected from nine sources: an agricultural field, a sequence of seven prairie reconstruction stages spanning 1-10 years since reconstruction began, and a remnant prairie. Field soils were characterized by phospholipid fatty acid (PLFA) analysis to determine microbial community composition. Ten individual S. scoparium were collected from the remnant prairie, and daughter ramets of each were propagated in sterile conditions by removing field roots and growing new roots in water and potting each ramet with soil from one of the nine sites. After three months, we collected roots for genetic analysis of AMF and tested for sources of variation in shoot growth (measured as the product of shoot and leaf number) using mixed-effect models.

Results/Conclusions

PFLA analysis showed a marginally significant increase in AMF biomass from agriculture to reconstruction to remnant soil. Plant genotype and shoot size influenced flower number, with smaller plants producing more flowers, regardless of soil treatment. This trend suggests that plant investment in early flowering reduces resources for vegetative production. Growth showed a marginally significant decrease with reconstruction age, suggesting that soil environment might restrict shoot growth for S. scoparium in later stages of the reconstruction process. A potential explanation for this decrease could be increased competition for fixed carbon allocation with soil microbes over the course of prairie reconstruction. Our analysis of the AMF community may provide insights as to the specific roles of AMF taxa as modulators of warm season grass growth during the prairie reconstruction process.