Along with the regular prairie planting that happened in the Arb this fall, a new research project, overlaid on one of the plantings was also initiated. This project is designed to investigate the impact of inoculating our restoration plantings with soil from original, never plowed, prairie remnants.
Prairie restorations are, in general, planted into fields that have been in agricultural cultivation for many years. Many of the original soil organisms—bacteria, mold, fungus, even tiny invertebrate animals—are very likely lost during this period of cultivation. This new project hopes to investigate our ability to return some of those organisms to the soil, and the impact on the vegetation of doing so. We believe that the soil organisms may have a large impact on the ability of the largest prairie grasses to dominate restoration plantings, something that we normally don't see in true prairies.
Half of our research plots were inoculated with original soil from small prairie remnants in the Northfield area, hopefully with all of the unique microbes. The other half of the plots were left without the added soil. Then all of the plots were planted with the Arb’s regular prairie seed mix, but without the large grasses included. Those seeds were introduced last, to only half of the plots. The treatments in the research plots are thus: one with no original soil and no large grass seeds, one with only soil, one with only large grass seeds, and one with both soil and large grass seeds.
This type of research is useful to the Arb because it shows the effects that the original prairie soil has on the large grasses as well as the wildflowers in the regular prairie seed mix. It provides a control group and several experimental scenarios that give the Arb management staff an opportunity to monitor how quickly and how widely the large grasses naturally spread out over the prairie. Because many of the restored prairies in the Arboretum and elsewhere are dominated by the large grasses, knowing more about the way that their seeds spread and grow will be useful to creating healthier, more diverse prairies.