Early successional prairie plants are less mycotrophic and have greater specific root length than late successional prairie plants

Background/Question/Methods

Early successional plant species have developed a distinct set of traits which distinguish them from late successional plant species. Early successional plants such as ruderal, weedy and invasive plants, grow fast, mature early and allocate heavily to reproduction and are thereby able to rapidly colonize disturbed lands, thus hindering the establishment of a native late successional plant community.  In addition to life-history trade-offs mediating the colonization of disturbed lands, there is an emerging view that soil fungi play a vital role in mediating plant community dynamics. Symbiotic fungi such as arbuscular mycorrhizal (AM) fungi can enhance plant community diversity and plant.  To study the response of prairie plants to AM fungi, we selected thirty-two prairie plant species from 6 different plant families that included eleven early, eleven middle, and eight late successional species and grew them with and without AM fungal inoculum with replication.  We analyzed plant biomass and root structure using a mixed model with species within successional stage identified as a random effect and decomposed successional stage into A PRIORI orthogonal contrasts.

Results/Conclusions

Plant successional stage was one of the largest determinants of total plant size (p=0.0007), as early successional species had faster growth rates than middle and late successional species (p=0.0001) that resulted in increase of 93% in total plant biomass. Inoculation with mycorrhizal fungi increased plant biomass by 39% (p=0.001).  In general, early successional species showed a 5.5% increase in plant biomass with inoculation, while plants from middle and late successional stages were 93% and 198% larger, respectively, with inoculation (p=0.0001).  Root architecture, as measured by root tips per mass, was significantly affected by plant family (p=0.0001) and successional stage (p=0.01) with early successional stages having more root tips per mass than later successional species. Analysis of correlations of population means (best linear unbiased predictors) demonstrated that mycorrhizal responsiveness, as measured by the mass of AM inoculated plant relative to the mass of sterile grown plants, was negatively correlated with average plant mass (p=0.005) and the number of root tips per mass (p=0.03).  Our results indicate that early successional species are less mycotrophic, but have increased root length relative to late successional plant species.