Wednesday, November 15, 2006

Plant Community Influences on Spatial Distributions of AMF Communities.

Daniel Mummey and Matthias Rillig. The University of Montana, Health Sciences 104, Missoula, MT 59812, United States of America

Arbuscular mycorrhizal fungi (AMF) form spatially complex communities in terrestrial ecosystems with known consequences for plant community structure and soil processes. It has previously been demonstrated that AMF community subsets differentially associate with different host plants in a given community, but it is not clear how this translates into spatial patterning of AMF. Using the example of a local grassland near Missoula, Montana, USA we explored the spatial organization of AMF communities in relation to host plant distribution and (aboveground) biomass in small plots. For this purpose we employed T-RFLP (rRNA large subunit)-based fingerprinting of AMF soil communities, together with clone library construction. We found distinct spatial patterns of AMF communities, also in relation to host plant distribution. In the same grassland, we also observed distinct patterns of AMF communities in relation to shifts in dominants of a particular plant species, the invasive plant Centaurea maculosa. Further, in greenhouse experiments we explored spatial effects imposed on a given root-inhabiting community of AMF by neighboring plants with housing different AMF community subsets. Our results highlight the spatial organization of AMF communities in plant communities, give important clues as to the potential ‘spheres of influence’ of hosts, and help formulate hypotheses for the roles of AMF in influencing plant community composition.