Modified soil community effects on the growth, establishment, and herbivore defense of Erigeron glaucus

The invasion of velvetgrass (Holcus lanatus) into native northern Californian coastal prairie creates an ideal opportunity for examining natural levels of soil biodiversity under field settings.  H. lanatus is reducing both aboveground plant biodiversity and belowground arbuscular mycorrhizal (AM) fungal diversity.  Using the soil communities from native uninvaded and invaded areas we can explore the role of the soil community, and particularly AM fungal diversity, on a coastal endemic, the seaside daisy (Erigeron glaucus).  We found that the soil community beneath H. lanatus, even in the absence of H. lanatus, reduced E. glaucus seedling establishment and growth.  Thus, invaded soil reduced E. glaucus fitness even in the absence of a competitor.  We are also exploring whether tolerance and resistance of E. glaucus to herbivory is mediated by invaded and native soil communities.  Different AM fungal communities have large effects on E. glaucus, and soil modification by H. lanatus creates the ideal setting for exploring how soil communities alter aboveground plant interactions with herbivores and other species.