Interactive effects of fire and plant invasion on belowground processes and microbiome functions

Nonnative weedy plants can promote wildfires. In the Southwestern U.S., for example, weedy grasses can fill gaps between native cacti, significantly increasing fire fuel availability, leading to bigger fires. To reduce impacts of this weed-fire connection scientists have traditionally focused on the planting of native plant species.

Focusing on plants alone, however, might be misplaced. Important processes that affect fire behavior might occur below ground, in the soil, and may play a crucial role in post-fire habitat recovery. This project will study the bacteria and viruses (microbes) and the different types of organic matter in soil to better understand the relationship between weedy plants and wildfire.

Once the researchers understand these soil processes, they will design inocula that contain soil and plant seeds that promote recovery in damaged areas. Combining the right belowground (soil) and aboveground (seeds) ingredients, the researchers hope to create an environment where soil microoganisms promote growth of native plants, which in turn provide nutrients back to the soil that promote growth of beneficial microbes.

The project will publicize its results to land managers via workshops, extension publications, and the EcoRestore digital portal. In addition, high school students participating in a free outdoor science program will collect data, identify plants and maintain experimental plots.

With increasing temperature, drought severity and fire frequency, western US forests have the potential to transform from net sinks to net sources of CO2. In addition, invasive grasses can create sustained, novel, grass-fire cycles. To understand the effects of grass-fire cycles belowground, the researchers will investigate: (1) the interactive effects of fire and plant invasion on the microbiome and biogeochemistry of the soil; and (2) changes in soil viruses and their role on necromass entombment and carbon sequestration.

Finally, to test effective and economically viable approaches to assist post-fire recovery, the project will design and deploy inocula to disturbed areas based on different formulations of plant seeds and soils with the ultimate goal of priming the ecosystem towards soil carbon sequestration. In addition to the outreach activities described above, the project will include training opportunities for a Ph.D. student and several undergraduates.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.