Mycorrhizal-mediated phosphorus transfer between tallgrass prairie plants Sorghastrum nutans and Artemisia ludoviciana

1. A glasshouse P-32-labelling study examined arbuscular mycorrhizal (AM)-mediated transfer of phosphorus between individuals of two tallgrass prairie species, an obligately mycotrophic grass (Sorghastrum nutans Vitm.) and a facultatively mycotrophic forb (Artemisia ludoviciana Nutt.). 2. Regardless of which species served as donor, P-32 was transferred between both intra- and interspecific neighbours via AM mycelia. However, nutrient transfer via AM fungi was not uniform between neighbouring species. 3. Conservative estimates indicate that interplant transfer via AM fungi accounted for > 50% of the total P-32 acquisition by S. nutans, but accounted for only 20% of P-32 uptake into A. ludoviciana. 4. While this study did not show conclusively that a common mycelial network acted as a conduit for nutrient transfer, it clearly demonstrated that mycorrhizae facilitated transfer. 5. The results indicate that differential movement of plant resources via AM mycelium may be a mechanism whereby a dominant, highly mycotrophic grass extends competitive advantage over a less mycotrophic, subdominant forb species in grasslands.