Collaborative Research: INTEGRATION OF PLANT-SOIL FEEDBACKS WITH RESILIENCE THEORY FOR PINON WOODLANDS UNDER DROUGHT

Severe drought is causing trees to die around the world, including in the piñon-juniper woodlands that occupy hundreds of millions of hectares of the western US. Unfortunately, new seedlings are not replacing the trees that have died. These seedlings may need beneficial soil microbes, which have also declined under drought. This project tests this by adding beneficial microbes to piñon seedlings planted into areas of experimental severe drought and nearby areas with normal conditions. DNA sequencing will identify the important microbes. Greenhouse experiments will expand this idea across the range of piñon pine by comparing seedling growth in soils from sites with different severities of drought. This project will develop new methods to restore piñon trees in areas devastated by drought. The seedlings of most tree species rely on beneficial microbes to survive and grow. Thus, results will also inform management of other forests across the US. This project trains graduate, undergraduate, high school students, and local school teachers to allow the research to reach additional participants. Drought is common in the western US and other parts of the world and can lead to tipping points at which ecosystems lose resilience – the capacity to withstand disruption without a change in function. This research investigates plant-soil feedback as a general mechanism to promote the resilience of terrestrial ecosystems to drought. Experiments leverage a large-scale, historical forest drought experiment to evaluate the hypothesis that positive species-specific plant-soil feedbacks between trees (piñon pine) and specialist soil microbes (ectomycorrhizal fungi) increase resilience by benefiting seedling recruitment. Field inoculations and laboratory assays will determine the degree to which recovery hinges on keystone fungi and their functional traits. This project achieves generalization across the geographic range of piñon pine with a greenhouse experiment to detect the threshold level of drought that degrades the resilience conferred by plant-soil feedback. This research integrates theory and experiments to promote synthesis across spatial scales that advances understanding of how environmental change disrupts biological interactions and how these interactions influence resilience to environmental change. This project has high potential to broaden understanding of how soil microbes sustain terrestrial ecosystem resilience and to advance use-inspired research through the discovery of practical solutions (soil inoculants) to maximize the resilience of woodlands to drought. 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.