We are studying how a particular type of fungus—mycorrhizal fungi—are affected by climate change, and how their responses to climate change could contribute to losses of coniferous forests in California following wildfire. Mycorrhizal fungi colonize plant roots and grow hyphae into the soil. The hyphae scavenge for nutrients that the fungi transfer to plants in exchange for carbohydrates. Most plants require mycorrhizal fungi to grow well. They essentially fertilize the plant. They also likely help conifer seedlings obtain water as they grow after wildfires. High temperatures and drought can be extreme in surface soils of fire scars, and seedlings may struggle to access water in lower soil depths without mycorrhizal fungi. If climate change harms mycorrhizal fungi that assist conifer seedlings, the seedlings may not reestablish in the fire scar. Instead, shrubs or grasses with hardier mycorrhizal fungi could take over.

We are testing these possibilities by conducting field, laboratory, and modeling experiments. We will examine soil conditions and water stress in the Bobcat fire scar in Southern California. This fire scar spans a range of climates. We will also conduct a set of laboratory experiments in which we determine the ability of mycorrhizal fungi and plants to tolerate extreme soil conditions. We will integrate the knowledge we gain into models that simulate soils, ecosystems, and landscapes under climate change. This way, we can predict whether mycorrhizal fungi contribute to shifts from coniferous forests to shrublands or grasslands in response to climate change and wildfires.