Anthropogenic alterations of pollinator systems have led to the decline of biodiversity in aboveground and belowground communities. Re-establishing native plants in disturbed landscapes is key to improving the biodiversity and function of both communities in ecological restorations. In this study, we leveraged an existing tallgrass prairie restoration experiment to test whether soil microbial inoculations impact the number and type of pollinator visits in a tallgrass prairie restoration. Plots were established in 2016, and before treatments were applied (local arbuscular mycorrhizal [AM] fungi, whole prairie soil, or no inocula), non-native Bromus inermis (smooth brome) was eliminated from half of the plots through solarization and the other plots were mowed. Surveys of insect pollinators were conducted every other week from June – mid-August, 2019 (5 survey times in total). At each sampling time, data was collected on the number of pollinator visits made by eight focal groups (Apocrita, Bombus, Wasp, Lepidoptera, Coleoptera, Syrphidae, Nematocera, Brachycera), the number of flowering stems of a focal species, and plant community composition in each plot. Understanding how soil inoculations impact plant-pollinator interactions is key to restoring ecological function of degraded habitats.
Results/Conclusions
The total number of insect visits was >175 % higher in solarized plots compared to plots in which brome had been mowed. After three years, mowed plots contained very few forbs and remained dominated by grasses in all soil treatments. Inoculation with whole soil was associated with higher native plant richness within the first year of the experiment. In summer 2019, the number of hymenoptera (Apocrita, Bombus, and Wasps) visits was 25% higher in plots inoculated with whole soil compared to plots inoculated with AM fungi or uninoculated controls. In brome plots, visits by Nematocera were lowest in the AM fungal treatments but there was no difference in Nematocera visits between whole soil and uninoculated treatments. The average number of flowering stems was >10% higher in plots inoculated with whole soil compared to AM fungal plots or uninoculated controls. The number of insect visits was highest in mid-July, driven by the high numbers of Bombus visiting Monarda fistulosa during peak blooming. The number of insect visits was lowest in May when only Penstemon digitalis was blooming. Inoculation with native soil microbes increased the flowering stem number of key focal species, providing critical resources for insect pollinators in an ecological restoration.