Plant-soil feedbacks and soil mycorrhizal data

Climate change intensifies fire activity, raising questions about the impact of fire-induced changes in soil biota on plant-soil feedbacks and plant invasions. We explored effects of plant-soil feedbacks and heat to simulate fire on mutualistic arbuscular mycorrhizal (AM) fungal communities and invasive plant growth. Soils were collected from a dominant native grass (Chionochloa macra) and two invasive hawkweeds (Hieracium lepidulum, Pilosella officinarum) in a New Zealand grassland, then heated to 30 ºC, 45 ºC and 60 ºC. In an experiment, hawkweeds exhibited greater biomass in Pilosella soils, which also had the highest AM fungal richness. Heat had little effect on plant biomass or AM fungi composition and richness. Hawkweeds alter AM fungal communities relative to the dominant native grass, but moderate heating of soil caused by fires could facilitate Hieracium invasion. Further, plant-soil feedbacks by Pilosella could facilitate invasion by Hieracium, suggesting the potential for microbially-mediated invasional meltdown.