This doctoral dissertation research project will examine the factors contributing to the observed decline in oak (Quercus) species regeneration across the deciduous forests of the eastern United States. Using a variety of field-based and analytical methods, this project will investigate the multiple factors that may be contributing to decline rates in oak regeneration, including disturbance regime modifications, climatic change, land-use history legacies, and abiotic environmental conditions. Project results will provide much-needed insights into the complex dynamics occurring in oak forests across the eastern U.S., and they will increase theoretical knowledge regarding the ecosystem effects of land-use legacies and multiple, interacting forest drivers, such as canopy disturbances and drought events. Because oak forests offer important ecological, economic, and social benefits to society by producing food and habitat for wildlife, supporting associated vegetative communities, providing valuable timber, and offering scenic opportunities for recreation, this project will assist in the conservation of these benefits by providing information and insights regarding the mechanisms that are reducing the range of oak-dominated forests. The project also should suggest possible forest-management plans to prevent the loss of this important genus. The project will offer special education and training opportunities for undergraduate students who will assist with both field data collection and laboratory analysis. Results from this project will be disseminated broadly through scholarly publications and presentations and through educational outreach activities at land-management offices in the study area. As a Doctoral Dissertation Research Improvement award, this award also will provide support to enable a promising student to establish a strong independent research career.
Having dominated eastern deciduous forests for the past 5,000 years, the ecological, commercial, and societal importance of oak forests represents a distinctive long-term legacy across the eastern U.S., but oak species throughout the region are failing to regenerate due to the increased abundance of understory shade-tolerant species that prohibit light from reaching oak seedlings and saplings on the forest floor. The goal of this project is to elucidate the relative importance and the site-specific nature of the multiple forest drivers and to identify interactions among different drivers. The doctoral student will use forest-inventory, dendrochronological, and land-survey analysis methods to investigate multiple drivers of this compositional shift across the Driftless Area in southwestern Wisconsin, an area undergoing significant decreases in oak regeneration. She will examine land surveys from the 1840s and 1940s alongside modern forest inventory data to identify the forest development trajectories occurring throughout the study area. She will employ dendroecological methods to document canopy disturbance histories and to quantify the relationship between climate and radial tree growth. She will use structural equation modeling to analyze the relative influence of land-use legacies, canopy-disturbance history, climate, and site-specific abiotic factors on oak regeneration.
