Manipulation of soil microbial communities is a common method of enhancing plant survivorship and growth during ecological restoration. Arbuscular mycorrhizal fungi (AMF) are an important group of soil fungi which improve plant nutrition and alter patterns of nutrient cycling in the rhizosphere. Inoculating plants with soil collected from a reference community (“whole soil transfers”) has been shown to increase AMF colonization and growth in many plant species; however, the influence of “whole soil transfers” on nutrient cycling and acquisition remains poorly described.
We investigated the influence of microbial inoculants on AMF communities and nutrient dynamics by inoculating Liriodendron tulipifera and Prunus serotina tree saplings sourced from three populations with either a commercially produced microbial inoculum or soil collected from a mature mixed forest near our restoration site. An equal number were left uninoculated as controls. Soil and leaves were collected after one growing season for nutrient determination and molecular analysis of AMF communities. We predicted inoculation would elicit significantly different AMF communities and that trees receiving “whole soil transfers” would have increased nitrogen and phosphorus content in both soils and foliar tissue. We investigated the influence of “whole soil transfers” from conspecific and heterospecific trees in a supplemental experiment.
Results/Conclusions
Analysis of terminal restriction fragment length polymorphism (TRFLP) data indicated a significant effect of inoculation treatment on AMF community structure. Inoculation treatment also influenced nutrient dynamics in rhizospheric soil and leaf tissue. Prunus trees inoculated with “whole soil transfers” had significantly higher soil carbon to nitrogen ratios than control trees. In Liriodendron, trees inoculated with “whole soil transfers” had significantly increased soil inorganic phosphorus content in comparison to control trees. A significant population by treatment interaction also influenced soil inorganic phosphorus in Liriodendron. Additionally, we noted a significant suppression of foliar inorganic phosphorus in Liriodendron trees inoculated with the commercial product. Preliminary results from our supplemental experiment also indicate that tree response to inoculation with “whole soil transfers” is species specific.
An accurate understanding of the influence of microbial inoculation on fungal community structure and nutrient dynamics will enable restoration practitioners to develop and implement effective protocols for reforestation. Our results suggest that “whole soil transfers” from reference plant communities influence soil nutrient availability and plant nutrition in two temperate tree species. Appropriately sourced “whole soil transfers” may facilitate nutrient cycling, restoring an important ecosystem service often lost in degraded ecosystems.