Quantifying Plant Mediation of Ecosystem Multifunction in Response to Fire and Warming

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This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2).Wildfire and warm temperatures affect how ecosystems function, but their impacts can also be mediated by plant communities. For example, wildfire and warming may speed up decomposition rates in the soil, but this trend can be slowed if the plant community produces leaves that are thicker and tougher to decompose. Ecosystems are shaped by disturbances like fire, and when these disturbances change, some species may be unable to survive. This project examines how fire severity and experimental warming interact to shape plant traits, plant communities, and multiple ecosystem functions such as decomposition and plant productivity. The project studies ponderosa pine forest understory communities in Arizona. This work is of critical importance as the climate warms and increasingly severe fires occur over large area of the western United States. Results from the study provide valuable information about biodiversity, ecosystem function, and ecosystem stability in the future. In addition, the project trains a new generation of scientists in ecosystem science.The project implements an experimental manipulation of temperature that mimics future climate scenarios across a fire severity gradient that encompasses a range of fire severities. The project addresses three key hypotheses: 1) Fire severity, climate alteration, and their interactions will strengthen abiotic filtering relative to untreated controls; 2) Fire severity, climate alterations, and their interactions will reduce plant trait diversity relative to untreated controls; and 3) The relative importance of indirect, plant mediated effects of fire severity and climate alterations will increase over time, ultimately leading to a reduction in ecosystem function in burned and warmed plots. Changes in the plant community and ecosystem function are quantified, and then used to calculate two metrics of ecosystem function. Finally, structural equation modelling is used to answer our overarching research question: How does the understory plant community mediate the effects of fire severity and climate change on ecosystem multifunction over time?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.