With increasing levels of disturbance in terrestrial ecosystems, understanding how plant–mycorrhizal fungal interactions shape above and belowground communities is critical. Variation in plant growth response to arbuscular mycorrhizal (AM) fungi can lead to feedbacks, the direction and strength of which can shape plant community structure and function. Knowing which plant species benefit most (and least) from AM fungi (i.e., mycorrhizal responsiveness) may be important for guiding the restoration of disturbed habitats, such as the Palouse prairie of Eastern Washington, which is one of the most endangered ecosystems in the USA. Intensive agriculture has left the Palouse prairie highly fragmented and restoration efforts have been hindered by a legacy of soil disturbance that has negatively impacted soil microbes and facilitated the encroachment of invasive plant species. In an effort to inform restoration efforts, we tested the mycorrhizal responsiveness of 24 plant species native and non-native to the Palouse. Plants were grown with and without AM fungi in a greenhouse for four months and mycorrhizal responsiveness was calculated for each species. Data from greenhouse studies will be used to inform a field experiment to determine whether inoculations with AM fungi improve native plant establishment in the Palouse bioregion.
Results/Conclusions
Plants native to the Palouse had a stronger growth response to AM fungi than their non-native competitors. On average, native plant species had a 69% increase in total biomass in inoculated compared to uninoculated soil whereas non-native plant species had an average of 25% decrease in biomass in inoculated versus uninoculated soil. Mycorrhizal responsiveness in non-native plants ranged from -66% in Linaria dalmatica (Dalmatian toadflax) to +15% in Ventenata dubia (wiregrass). Most of the native Palouse plant species tested (7 of the 12) had a positive growth response to AM fungi. The native species Eriogonum heracleoides (Wyeth buckwheat) and Asclepias speciosa (showy milkweed) showed the strongest growth response to AM fungi, with a greater than 250% increase in biomass in inoculated versus uninoculated soils. However, some native plant species (e.g., Mimulus guttatus, Symphyotrichum spathulatum) did not respond positively to AM fungi. Understanding which plant species benefit the most and least from AM fungal inoculations may be useful in guiding restoration efforts in landscapes such as the Palouse, where the mycorrhizal communities have been disrupted by agricultural management practices and/or biological invasions.