Arbuscular mycorrhizal inoculum source influences plant survival and growth in an urban prairie restoration

Background/Question/Methods

Interactions between plant species and arbuscular mycorrhizal fungal (AMF) species have been demonstrated to vary; ranging from mutualistic to parasitic.  Less beneficial species of AMF tend to produce spores prolifically, are commonly found in early successional environments, and associate with weedy or less conservative plants.  These AMF species are often easier to propagate by culturing.  In contrast, some beneficial AMF do not produce spores frequently, are characteristic of later successional environments, and associate with long-lived conservative perennial plants. These AMF species are often difficult to propagate by culturing. The use of commercially propagated mycorrhizal inoculum is increasingly popular in ecological restoration practice, but life history strategies of commercially propagated AMF species may not be compatible with the later successional plant communities, which are the restoration target.  We tested the effect of AMF inoculum source on four mid-successional prairie plants common in prairie restorations: Allium cernuum, Lespedeza capitata, Ratibida pinnata, and Schizachyrium scoparium.  We compared plant survival and growth response of the four plant species when associated with a mixture of seven AMF species cultured from native prairie (native), a commercially produced AMF inoculum (commercial), and a sterile control in an urban prairie restoration project located in Chicago, Illinois.

Results/Conclusions

Plant species survival and growth response was not consistent across all four plant species.  A. cernuum exhibited significantly lower mortality and larger plant size with the native inoculum than the commercial inoculum.  L. capitata exhibited lowest mortality in live (native or commercial inoculum) soil over the sterile control and overall plants were significantly taller in the native inoculum than the commercial inoculum.  S. scoparium did not experience any significant effects of inoculum source on survival; however plants were significantly larger with native inoculum.  The effects of inoculation on R. pinnata were evident in the plants’ response to a post-planting herbivory event.  R. pinnata plants inoculated with commercial inoculum experienced significantly more herbivory than plants inoculated with native inoculum or the sterile control.  One month post-herbivory, plants inoculated with native inoculum had significantly more leaves, though the significant difference in growth effects diminished by the second year of sampling.  These data demonstrate that for these four prairie plant species, the use of native inoculum promoted survival and growth better than commercial inoculum.  This study suggests that AMF currently used in commercial production may not be as beneficial to restored prairie communities as AMF cultured from a native prairie system.