The plant microbiome, including endophytes, mycorrhizal fungi, beneficial soil bacteria, and other biota can influence plant health and plant community dynamics. As a result, there have been frequent calls to include microbial communities within ecological restoration efforts. Whole soil communities collected from remnant prairies have been found to promote restored prairie plant establishment. However, whole soil inoculations present an additional dilemma; in order for whole soils to be included in restorations, they must be harvested from intact reference ecosystems, which are often scarce and small. Thus, we have begun to identify key soil microbes to include in a restoration. Within tallgrass prairies, mycorrhizal fungi are important microbes, as most plant species are responsive to arbuscular mycorrhizal (AM) fungi. For this study, we compare the growth and survival of transplanted prairie plant seedlings to inoculation with whole rhizosphere soils versus AM fungal communities isolated from these soils. We collected whole rhizosphere soil from remnant old growth grassland communities in Illinois, Kansas and Oklahoma. From these same locations, we also cultured diverse AM fungal communities. In five restorations projects in Illinois (1), Kansas (2) and Oklahoma (2), we inoculated mid- and late-successional seedlings with either whole rhizosphere soil or AM fungal inocula.
Results/Conclusions
We found that whole soil biota and AM fungi inoculations consistently improved plant survival (p<0.0001) and growth (p<0.0001) across our five restoration locations during the first growing season and these patterns continued during the three year period we collected data from these sites. We found evidence that AM fungi are a keystone guild in the plant rhizosphere microbiome, as AM fungi and whole soil inoculations were indistinguishable in their ability to improve plant growth and survival as indicated by a non-significant contrasts comparing plant survival and growth with the two living inocula types (both p=0.2). Interestingly, survival of forb, legume, and grass functional groups were all similarly improved with both AM fungi and whole soil microbiome inoculation, as indicated by non-significant contrasts comparing AM fungi vs. whole soil inoculation by functional group interaction (survival p=0.5, growth p=0.2). Restoration location was important to seedling survival (p=0.02), however all sites benefited from both AM fungi and whole soil inoculation. These studies highlight the importance of the plant microbiome in native plant restoration. We suggest that reference ecosystem AM fungi can be used as an alternative to whole soil biota inoculations in disturbed soils that may require rhizosphere amendment.