Mycotrohic prairie plants demonstrate fungal specific growth responses

Background/Question/Methods

Shifts in the plant life history traits are apparent during succession of the tallgrass prairie. Generally, early successional plants grow and reproduce quickly, while late successional plants are more stress tolerant and allocate more resources below ground. Evidence is accumulating that belowground symbionts, such as arbuscular mycorrhizal (AM) fungi, can play an important role in grassland system dynamics. Restoration practitioners have begun to incorporate mycorrhizae into tallgrass prairie restorations, often in the form of a mixed commercial inoculum. However, predicting how native prairie plants will respond to particular AM fungal isolates has not been thoroughly researched.

To investigate how plants from different successional stages would respond to a variety of locally adapted fungal isolates, we grew six early and six late successional plant species in monoculture with seven native AM fungal species and a non-inoculated control. We analyzed plant growth response in a mixed model with species within successional stage identified as a random effect and decomposed plant response into a priori orthogonal contrasts.

Results/Conclusions

AM fungal inoculation proved to be the largest determinant of plant size (p=0.001) with successional stage also being a significant predictor of plant size (p=0.05), with early successional plant species being larger and plants being larger with inoculation. We tested whether  plants from different successional stages would respond differently to AM fungi, and found that late successional species were more responsive to fungi in general than early successional species (p<0.0001).  We also found significant variation in plant response to specific fungal species (p=<0.0001) and that plant growth response to specific fungal species was dependent on the successional stage of that plant (p=0.004).

Our results suggest that soil symbionts can drive plant community dynamics. That late successional plant species are more responsive to fungi and have greater specificity, suggesting that applying specific fungal species could increase the competitive ability of target plant species, potentially shifting plant community structure towards late successional prairie plants.