Explorations of Urban Dendrochronology in Louisville, Kentucky, USA

Urban trees and forests provide a variety of social and environmental benefits, but their function, and therefore the benefits they provide, can be enhanced or diminished by human influences. More work is needed to understand how urban forests mitigate, and are affected by urban heat, pollution, and other anthropogenic influences, especially in light of modern urbanization and climate change. As concentrated sites of accelerated environmental change, urban forests may also provide insight into how regional ecosystems may respond to expected, global-scale changes. One way to examine urban forests is through dendrochronology, but tree-ring methods have been applied rarely in urban areas, typically avoided in favor of areas with limiting climates and older trees. The objective of ongoing work in Louisville, Kentucky is to explore dendrochronology as an avenue for research into the growth and sensitivity of urban trees in relation to anthropogenic factors. We developed white oak tree-ring chronologies for six sites across the urban-rural gradient in Louisville, including two each of urban, peri-urban, and non-urban sites. We find that (1) growth patterns and climate-growth response, with some short-term differences, are comparable across the urban-rural gradient and that (2) land-use histories and disturbance likely drive differences. Across all six sites, tree growth sensitivity to climate variables is shifting or declining over the instrumental period. Extreme dry and wet years are the main driver of marker rings in all chronologies, but this may change with shifting sensitivities. In all, we find no signal that is unique to trees from urban environments.