Growth rates of ash trees inferred from annual rings in a lowland forest invaded by emerald ash borers

Link To Share This Poster: https://cdmcd.co/xvxBkg
Live Discussion Link: https://cdmcd.co/xvxBpk

Nina Kress, Sydney Kipp, Susan Roskopf and Todd D. Levine, Department of Life Sciences, Carroll University, Waukesha, WI

Background/Question/Methods
Forests are important ecosystems that sustain us through recreation, aesthetics and extractive services. As human activity disrupts both the disturbance patterns and the distribution of species, profound changes in land management and species composition will alter the community structure of our forests. The emerald ash borer (EAB) is a significant, invasive forest pest species harming ash trees throughout North America. These beetles attack ash trees, boring small holes under the bark, laying eggs in crevices, then the larvae feed on the bark until fully grown. This results in the ash trees dying in three to four years after infestation because EAB interrupts transport of water and nutrients. Understanding the process of infestation and subsequent changes in growth is essential to describing the dynamics of EAB invasions. EAB was first detected in Michigan in the early 2000s, subsequently spreading throughout the United States and Canada. The first report in Wisconsin was in 2008 and the first detection in Waukesha County was in 2012. In this study, we analyze cross sections of dead and dying ash trees infested by EAB from Prairie Springs Environmental Education Center (PSEEC) in Waukesha County, Wisconsin, USA. Trees were marked in 2012 and exhibited little growth between that time and when they were felled between 2018 and 2021. We examined tree ring structure after dead ash trees were felled. Tree rings are an important record that can be used to understand forest health history.
Results/Conclusions
Most trees were between 5 and 25 cm in diameter, with corresponding ages from less than 30 years to more than 60 years with an average of 48 years old. While there was a range of ages in our sample, ash tree ages at PSEEC are mostly homogenous, indicating a spread through the area corresponding to change in ownership and management. Trees generally exhibited a decline in growth prior to their deaths, but the timing of slowed growth varied considerably in their life cycles. Standardized growth rates for the stand declined between 2001 and 2003, remaining low thereafter. Together these growth rates revealed a concerted decline in ash tree growth throughout the stand beginning roughly 11 years before EAB was confirmed in the area. We are exploring whether EAB was in the area earlier than previously known or if there were other factors contributing to decline in tree growth, such as life stage or affronts to tree health.