Fagus grandifolia growth and mortality a decade after the emergence of Beech leaf disease

Beech leaf disease (BLD) is poised to cause major declines in American beech ( Fagus grandifolia ) across the eastern United States and parts of Canada. Given the dominance of this tree, quantifying impacts of this emerging disease is critical. Using long-term data from an existing field experiment (originally established to explore the impacts of soil chemistry on forests), we quantify rates of mortality and growth in American beech afflicted with BLD near the disease's epicenter. Since the initial observation of BLD in Cuyahoga County, OH in 2014, 75 of the 263 (29 %) American beech trees within our study have died. Most of this mortality was recent, with 2021–2023 displaying the highest levels of beech mortality (56 trees dying across the three years). Mortality was distributed unevenly across size classes, with the highest rates of mortality occurring in trees <25 cm DBH. Mortality rates were influenced by beech abundance, suggesting that areas with high concentrations of beech may experience higher rates of mortality. In addition, beech grew more slowly in recent years (2017–2022), suggesting a probable slowing of growth rates associated with BLD. Further, we observed lower growth rates in plots with the addition of soil amendments, but only before the arrival of BLD. As a dominant tree in many forests, this decline in American beech could catalyze larger stand-level changes in forest composition and function as BLD persists on the landscape and continues to spread into new areas.