Research focuses on tree rings to study climate in southwest Wisconsin

July 9, 2013
Sara Allen and her daughter Shea coring at the Platteville Mound.
Core sample

PLATTEVILLE, Wis.­­­ – Do you live in southwest Wisconsin and have an old oak tree? If so, University of Wisconsin-Platteville’s Sara Allen wants to know.

Allen, a post-baccalaureate research fellow in the Tree-Ring, Earth, and Environmental Sciences Laboratory with a double major in geography and history and a minor in biology from Platteville, Wis., is spearheading a research project titled “Establishing the Long-Term Range of Variability in Drought Conditions for Southwest Wisconsin” that involves taking core samples from more than 400 old growth oak trees throughout Wisconsin’s Driftless Region.

The two-year project, which began at the beginning of June, is funded by a $162,953 grant from the U.S. Geological Survey through the UW Water Resources Institute, which coordinates research programs that are involved in solving present and emerging water resource problems.

Under the mentorship of Dr. Evan Larson, UW-Platteville associate professor of geography, Allen and intern McKaylee Duquain, a forest sciences and botany major at UW-Madison, are working on the project. Six to eight undergraduate students will assist them in their research over the next two years.

In her research, Allen is using dendrochronology, a scientific method of assigning exact calendar dates to the annual growth rings of trees and analyzing patterns of tree-ring width to gain insight about past environmental conditions.

“Studying the tree rings in old oak trees is an incredible look into the past because the rings provide information about climate variation going back 300 to 400 years,” stated Allen. “This climate history can help us better understand current weather and the impact it has on our environment.”

Allen explained that southwest Wisconsin has had a variety of extreme weather events over the last few years, such as the flooding in 2008, severe drought last summer and heavy rainfalls that have drenched much of the region so far this year. Because the area is agricultural, these extreme weather fluctuations have had a negative impact on farmers’ crop production.

“Data from tree-ring measurements helps us understand the frequency of these weather fluctuations,” Allen continued. “As a result, we are better able to prepare for extreme events in the future so that we can effectively manage our natural ecosystems, our agricultural ecosystems and our water resources.”

“In the fieldwork, I will work with a team of undergraduate research assistants to collect tree-ring samples from about 400 living white oak and burr oak trees in 12 counties in the Driftless Area of southwest Wisconsin,” Allen continued. “Some of these oak trees have been here since before European settlement, so they have a lot to tell us about the history of the climate in this region.”

Using an increment borer that contains a bit with a hollow tube inside, Allen extracts a thin core of wood. The tree rings are visible on this core. Allen and the other researchers will analyze tree-ring width patterns within the cores for signs of long-term variability in rainfall and climate conditions. Generally, wide rings indicate years of good growth while narrow rings represent stressful times which, in turn, represents how the trees’ growing environment changes from year to year.

The timing of core extraction is very important because coring leaves a small opening in the tree, which may make the tree more vulnerable to infection from diseases such as oak wilt. Caution is taken by extracting cores in the fall, after diseases are less active and the tree has shut down its growing season.

Larson stated that this research will expand the understanding of climate and create a more complete picture of the range of potential drought conditions that southwest Wisconsin may face in the future.

“Data from the tree rings will provide a context for climate change predictions, which will help community planners understand a broader range of climate variability including the frequency of extreme events that will impact the environment,” said Larson. “This research will lay the foundation for similar efforts across the state.”

Allen said she is thankful to have the opportunity to work on this research project.

“This project is giving me hands-on experience conducting research and working in the field of dendrochronology,” she said. “The project will help people become more aware of changing climate, understand how it is affecting our region, and hopefully, take ownership of it. I hope to share my enthusiasm for this research with the new interns in the fall and use my experiences to help them learn and grow. This research can have a huge impact on our understanding of the effects of climate change on our regional environment. I am so excited to be a part of it.”

Allen’s research is one of several ongoing projects in UW-Platteville’s TREES Lab with a focus on better understanding the past to inform our actions in the future. The lab is a center of excellence in undergraduate research and conducts federally- and locally-funded research across Wisconsin, the Great Lakes Region, the United States, Canada and Sweden.

Anyone living in southwest Wisconsin who would like an old oak tree considered for this research study, contact Sara Allen at (608) 342-6149.

Written by: Laurie A. Hamer, communications specialist, College of Liberal Arts and Education, (608) 342-6191,


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