As little as 1% of the original expanse of North America’s tallgrass prairie remains intact and not degraded. The remaining tallgrass prairie is threatened by invasions of non-native plant species. Of critical conservation concern, restoration of native biodiversity has been met with little success following eradication of non-native plants. While much attention has focused on aboveground processes, considerably less research has assessed the role of belowground microbial processes in restoration success.
Two complementary experiments were conducted at Konza Prairie Biological Station in Manhattan, KS, USA on adjacent areas heavily invaded with Bothriochloa bladhii, a non-native warm-season bunchgrass. In these areas, previous attempts at restoration to native plant communities had been unsuccessful. In experiment 1, we established six replicate plots of each of the following four treatments: (a) whole prairie soil with native prairie seeds; (b) sterile prairie soil with native prairie seeds; (c) only native prairie seeds; and (d) non-seeded control. In experiment 2, seedlings of five native prairie plant species (Andropogon gerardii, Pascopyrum smithii, Ratibida columnifera, Asclepias syriaca, and Lespedeza capitata), were established in the greenhouse (nurse plants) with one of four soil inoculums: whole prairie soil, spores collected directly from Konza, AM taxa selected as beneficial to warm-season grasses, and sterile prairie soil. Nurse plants were transplanted into one of 24 replicate plots established following eradication of B. bladhii.
Results/Conclusions
In experiment 1, inoculation with whole prairie soil did not improve seed germination, however, addition of native soil microbes significantly improved native species seedling survival (41%), compared to sterile prairie soil or non-inoculated treatments (12-18%). Inoculation with native microbial communities significantly decreased re-establishment of B. bladhii; at the end of the growing season, plots receiving native soil comprised 33% B. bladhii canopy cover, compared to 70% in plots receiving no soil inoculum. In experiment 2, end-of-season nurse plant survival was substantially improved by inoculation with native soil microbes. While grass seedling survival was generally not improved following inoculation with native soil microbes, forbs survival was significantly improved when grown with native soil microbes. These studies indicates restoration success of degraded grasslands can be improved by additions of native plant seeds in combination with native soil microbial communities.