Measuring The Effects Of An Urban Plant Restoration On The Structure And Function Of Soil Microbial Communities

Restoring wildlife habitats has become a priority within densely developed urban areas across the United States. A central strategy underlying these restorations involves replacing invasive plants with native plant communities that have been found to substantially increase habitat resources for insects, birds, and mammals, and to increase ecosystem function and stability. A less visible aspect of these restorations occurs within the rhizosphere, the underground microhabitat surrounding roots where bacteria and fungi interact with plants by cycling nutrients and minerals back into soils to support plant growth and reproduction. In return, microbial communities are dependent on energy-rich compounds that plants release into soils through their root systems. This symbiosis suggests that changing the composition of plant communities during habitat restorations potentially drives concomitant changes within the rhizosphere. Few studies to date, however, have focused on the influences that shifting plants species composition may exert upon the structure and function of microbes colonizing the soils where these restorations take place. In August 2018, we began a baseline analysis to compare characteristics of soil microbes that inhabit restored soils with those that inhabit unrestored soils. Specifically, we incorporated a combination of phospholipid fatty acid analysis (PLFA), and microtiter EcoPlates TM analysis to track the effects of restructuring plant communities on microbial community structure and functional diversity within soil core samples taken from two Chicago Park District sites. The first site at Legion Park (restored) was restored with a variety of native plants ten years ago, while the second site at Thillens Park (unrestored) was slated to undergo a similar native plant restoration immediately following our sampling campaign. The PLFA analysis showed that, in comparison to the unrestored site, soils taken from the restored site contained significantly higher total microbial biomass, as well as a greater amount of fungal biomass than of bacteria. Additionally, soils extracted from the restored site also exhibited a greater proportion of fungal biomass to bacterial biomass. Furthermore, EcoPlate analysis confirmed that, in comparison to the unrestored site, soil communities taken from the restored site exhibited moderate increases in total metabolic activity. Finally, Shannon-Wiener and Simpson’s Diversity Indices both revealed that microbial communities within the 10-year old restored site were also able to metabolize a broader variety of carbon substrates. Our comparison of the two sites suggests that changing the composition of plant communities yields significant changes within the structure of microbial communities underlying habitat restorations – both in terms of the major groups present, e.g., bacterial biomass in comparison to fungal biomass, as well as in their functional capabilities to metabolize carbon-rich substrates