Shifting tree species composition of upland oak forests alters leaf litter structure, moisture, and flammability

In historically open-canopied and fire-dependent upland oak (Quercus spp.) forests of the central eastern United States, fire exclusion is contributing to an increase in competing non-oak tree species that are often shade-tolerant fire-sensitive. As these encroach abundance declines, becoming denser will likely become cooler, moister, less flammable through a hypothesized feedback loop termed mesophication. To better understand how this gradual shift forest composition could affect flammability leaf litter, primary fuel systems, we measured litter traits moisture dynamics two pyrophytic oaks three non-oaks, implemented experimental burns on plots (~3-m2) with beds comprised single- mixed-species litter. Non-oaks produced thinner, smaller leaves greater specific area compared oaks, had higher initial content, associated low flammability. Our confirmed was lower than decreased linearly increasing contribution bed. These species-driven changes fuelbed may provide mechanism whereby encroaching create self-promoting conditions favorable for regeneration oaks. Thus, without other management interventions, our ability reintroduce into systems as tool prevent further compositional shifts improve decline species’ fine bed increases.