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

Summary1 A glasshouse 32 P‐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, 32 P 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 32 P acquisition by S. nutans , but accounted for only 20% of 32 P 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.