Four Decades of Temporal and Spatial Dynamics in an Old-Growth Beech-Maple Forest in Southwestern Ohio, USA

Date of Award

2023

Degree Name

M.S. in Biology

Department

Department of Biology

Advisor/Chair

Ryan W. McEwan

Abstract

Old-growth forests are ecosystems that have experienced little to no anthropogenic change, granting them the ability to absorb and store vast quantities of carbon, serve as safe havens for rare and endangered species, and house menageries of biodiversity. According to global land surveys, about 36% of old-growth is left globally, with less than 6% of this existing within the United States. Data collection of species-specific rates for tree populations in repeatedly sampled permanent plots allow researchers and land managers to anticipate responses to anthropogenic and biological ecosystem stressors and to create strategic and robust conservation plans. In this project, we leverage forty-one years of scientific data collection of the old-growth forest Hueston Woods to analyze long-term dynamics during an era of compounding anthropogenic pressures. Our study site is a permanent 100 m x 105 m plot in Hueston Woods State Nature Preserve, located in Preble County, Ohio. Vegetation sampling was first implemented by Dr. John Vankat at Miami University, Ohio, in 1981 and was repeated in 1988, 1994, and 2000, before being handed to Dr. McEwan's Forest Ecology Lab at the University of Dayton for this projects sampling in 2022. We analyzed changes in woody species importance in terms of relative density, relative frequency, and relative basal area, as well as in historical canopy gap production to understand long-term forest change. The system is in a state of reaction to "multiple interacting ecosystem drivers," primarily overpopulated white-tailed deer (Odocoileus virginianus), which have existed in high enough densities to negatively impact vegetative communities in the eastern United States since the mid-to-late 20th century, and the invasive emerald ash borer (Agrilus planipennis), which has inflicted a 99% mortality rate upon the genera Fraxinus in North America since its introduction to the United States in 2002. For the overstory, we predicted that (1) importance values will remain relatively static for the first four sampling years followed by extreme changes between 2000 and 2022 due to compounding anthropogenic disturbance, and for the understory we predicted that (2) importance values will vary between all sampling years due to the stochastic nature of late successional forest understories. We predicted that aggressive white-tailed deer browse would lead to (3) a decrease in overall stand density and a decrease in woody species biodiversity. Finally, we predicted that (4) Fraxinus americana deaths due to the emerald ash borer would cause significant increases in canopy openness between the 2000 and 2022 sampling years. Both overstory and understory results revealed that importance values remained steady in the from 1981 to 2000 with extreme changes experienced between the 2000 and 2022 sampling years. In 2022, Fraxinus americana canopy trees experienced 100% mortality due to the emerald ash borer which caused extreme canopy openness. This change favored overstory species that grow quickly in high-light environments such as Liriodendron tulipifera, Prunus serotina, and Acer saccharum, and may be the cause for the decrease in Fagus grandifolia overstory importance due to an inability to compete with A. saccharum trees under these conditions. Analysis of long-term shifts in species dominance were strongly related to the relatively palatability of those species to white-tailed deer browse. From 1981 to 2022, the plot lost 52% of native species, 35% of which are highly or moderately preferred by white-tailed deer. Deer browse may also be the cause of stand density decline. Spatial data displayed a lower frequency of extreme high- and low-density patches in 2022 in comparison to all other sampling years. Species that grow quickly in gap space and are resistant to white-tailed deer browse, such as P. serotina and F. grandifolia increased in overall stand dominance. Understory resident species not preferred by deer, such as Asimina triloba and Lindera benzoin, experienced significant increases in understory importance, basal area, and density; a result that may also be influenced by increased canopy gap space. The results from this study highlight the severe negative impacts that compounding anthropogenic influences can have on vegetative communities. Action is already being taken to manage white-tailed deer browse and invasive species within Hueston Woods State Nature Preserve, including controlled hunts and mechanical and herbicidal treatments, but quantifying decadal changes may lead to developments in sustainable management plans to handle these issues going forward.

Keywords

Ecology, Environmental Science, Forestry, Biology, old-growth forests, permanent plot, Hueston Woods

Rights Statement

Copyright © 2023, author

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