Wooster Geologists

Figure 1. Title page of Amanda’s thesis including one of the key figures.

Amanda Flory (class of 2025) completed a thesis that investigated the interplay between the pace of the ocean-atmosphere climate in the Northeast Pacific that is dominated by Pacific Decadal Variability along with the volcanically-forced coolings inferred from tree-ring records. Her title page (above) summarizes the results with several known volcanic intervals linked with decade-long coolings. These coolings are inferred from a tree ring-width series located in coastal Southeast Alaska (Dude Mountain, Ketchikan, Alaska). In addition to her thesis work Amanda presented her results at the meeting of the Geological Society of America in the Spring of 2025. The take-home here is that the variability as recorded in the tree-ring record appears to be a combination internal variability of the Northeast Pacific [1] and volcanic forcing [2] contributing to the decadal variability in the climate.

Figure 2. The author (left) cores a yellow cedar (Cupressus nootkatensis) – Nick (middle) and Proto provide support.

Figure 3. Comparisons of Sitka, AK temperature records for the months of December through October of the growth year correlated with the Dude Mountain ring-width record.

This climate/tree-ring comparison (Figure 2) examines the moving correlation over time (since 1857) is based on a running 35-year correlation. Correlations change from positive (blue) to negative (red) and back to positive. This non-stationary response temperature is puzzling and is likely complex reflecting the ecological and climate-related thresholds at the site. Amanda explored the correlation between ocean heat content ([3]; see Figure 1: title page) and tree growth. The strong and steady relationship between the ocean heat content and growth suggests that the near-coastal tree-ring site is dominated by the ocean-atmosphere system immediately offshore.

Figure 4. Key volcanic events that correspond with decades of cooling.

As is the case with most theses, more crucial questions are raised and will continue to be investigated. These include continuing the examination of the yellow cedar climate response as well as applying new analyses that seek to tease out the volcanic response from the internal response of the Pacific Decadal variability in the record.

Acknowledgements: This work was supported by the National Science Foundation Grant AGS-2002454. We would like to thank Klawock’s Alaskan Youth Stewards (AYS) group for their expertise and guidance while conducting field work.

References:

[1] Schneider, N., and Cornuelle, B.D., 2005, The Forcing of the Pacific Decadal Oscillation:, doi:10.1175/JCLI3527.1.

[2] Wang, T., Otterå, O.H., Gao, Y., and Wang, H., 2012, The response of the North Pacific Decadal Variability to strong tropical volcanic eruptions: Climate Dynamics, doi:10.1007/s00382-012-1373-5

[3] Levitus, S. et al., 2012, World Ocean heat content and thermosteric sea level change (0–2000 m), 1955–2010: Geophysical Research.

Guest Blogger Grace Neuman: From mossy bogs to forgotten fields, the landscape of Northeastern Ohio holds buried stories. My Independent study, examines how two centuries of post-settlement human activity have altered the region’s ecosystems, and how we can still see those imprints today.

I investigated various ecological and historical data sources, such as tree rings, sediment cores, soil textures, soil chemistry, and radiometric dating, to trace land use patterns and forest disturbance over time. These scientific methods helped uncover both natural and human-driven shifts in the region’s environmental conditions.

Me in the lab with sediment grain size analysis equipment (PARIO).

My work focused on Brown’s Lake Bog Preserve, located on Browns Road in Shreve, Ohio. This Nature Preserve harbors remnants of Ohio’s post-glacial ecosystems and is one of the last few acidic bog ecosystems remaining in Ohio. The LiDAR map above shows the location of the Bog (BB) and the lake (BL). This kettle lake is surrounded by kames.

Sediment core (left) and various measurements (right) provided by Erika Freimuth. The sediments here record the transition of the surrounding landscape from an organic-rich bog (black mud) to a brighter clay/silt blown into the bog when the land was cleared. This profound change took place about 1820 dated by Pb-210. The blue line on the left is magnetic susceptibility and tracks the increase in eroded soil to the basin whereas the red line (organics) decreases.

The gain size analysis of the sediment deposited in the basin closely after 1820 is composed of mostly clay and silt. This grain size is consistent with eroded soils from the surrounding farmed landscape.

The dating with Cesium-137 and Pb-210 by Dr. Josh Landis of Dartmouth College yielded interesting results.  The disruption about 1950 in the graph above suggests erosion and and increase in mass accumulation of sediment likely linked to logging in the basin.

Within the Preserve is a white oak stand of trees growing on the kames. These trees were witness to the land use changes. The release in tree growth about 1820 is consistent with the inferred land use change, also not the bump in ring-widths about 1950 when the forest was again selectively logged.

One of the classic kames surrounding the bog. This work was supported by the National Science Foundation and the Copeland Fund of The College of Wooster. We thank The Nature Conservancy for management of the site and permission to core the lake. Thanks also to T.V. Lowell for procuring the core and N. Wiesenberg for his help in the lab.

The link to the full publication and supporting data can be found here.

HBI Wizard, Aaron Diefendorf (University of Cincinnati) on the forest edge of Browns Lake, Wayne County Ohio. Dr. Diefendorf and Dr. T.V. Lowell and their students (Dietrich, 2023; Corcoran et al., 202o; Freimuth et al., 2021) are the force behind investigating biomarkers secreted from diatoms in lake as records of past precipitation changes. This basic research is impressive given they are chasing molecules (shown below) that are secreted from microscopic diatoms in lake waters and in complex organic sediments that accumulate at the bottom of lakes. Wooster Geologists have participated in the field monitoring and diatom work resulting in several Independent Study projects.

Diatom-derived highly branched isoprenoids (HBIs) are lipid bio- markers found in marine and lacustrine sediments. Most of the work on these has been done in marine environments and the UC group is now extending study to lake settings.

The sampling team on a North Dakota Lake.

Locations of the 50 lakes sampled in this study (A) and expanded maps of the Indiana lakes (B) and Adirondack region lakes (C).

The University of Cincinnati team and collaborators from St. Lawrence University coring on an Adirondack lake on a spectacular fall day. T.V. Lowell (orange gloves) is the core boss who has provided “high-quality” mud from the bottom of lakes and bogs across the planet and for several Wooster classes and student theses.

References:

Last Monday there was a power outage on campus and classes were cancelled, despite this news our afternoon lab period fieldtrip went on as planned. The trip consisted of a field trip led by Nigel Brush (retired from Ashland U. and Wooster). It was a great trip on a beautiful day and we greatly appreciate Dr. Brush’s time and willingness to share his expertise of the history of our region. 

Above the students survey ice stagnation features from the top of a kame.

View of a kettle from the rim of the kettle. The kettle is located on the map below (lower right).

Map (soilexplorer.net) showing the kame and kettle terrane with the esker in the middle. The kame shown in the photo above is the circular feature in the lower right.

The Mohicanville Dam is located in one of the former Lake Craigton spillways. The dam, located in this hours glass spillway, is the site of the narrowest reach of the gorge and controls floodwaters that would otherwise inundate communities to the south. Extensive flooding in 1913, in part, prompted the US Army Corp. to build this and other flood control structures.

GoogleEarth image of the Mohicanville Dam.

Map above (from soilexplorer.net) the amazing stagnant topography of the Browns Lake Bog area. Now that Dr. Brush pointed out some additional features in the region we wonder is the feature in the upper left is an esker?

The group at Browns Lake Bog discussing the old growth forest on the kames and the relatively new forest in the flats. The the post-glacial history recorded in the sediments and tree-rings at the site has been an extensive subject of research at the College of Wooster in collaboration wit hthe University of Cincinnati over the past two decades.

The upshot of the bog ecology is that during the time of European Settlement lake core records show a pronounced influx of silt and clay from surrounding soils and the fertilization of the nutrient-limited bog allowing the establishment of vascular plants (trees and shrubs) and the setting that we see today. This model was originally put forth by by Ireland and Booth (2012) and is the subject of Grace Neuman’s (’25) IS project (blog coming soon).

Reference: Ireland, A.W., Booth, R. K., 2012, Upland deforestation triggered an ecosystem state-shift in kettle peatland: Journal of Ecology, vol. 100, p. 586-596. 

The College of Wooster Tree Ring Lab faculty, staff and students have teamed up to publish results of  an analysis of a network of tree-ring sites in Northeast Ohio to ask the question what is driving the changing climate response of the trees. The tree-ring sites include young (100-year-old) white oaks in Secrest Arboretum, Wooster, two sites of post-settlement age (about 200-years old) from Wooster Memorial Park and The Kinney Field Park both in Wooster and four old growth sites (>300 years old) from some of our favorite sites including The College of Wooster campus, Cornerstone Elementary, Browns Lake Bog, David Kline’s (the author) old growth forest on his farm and Johnson Woods the largest tract to old growth white oak forest in Ohio.

Paleoclimate class (2021) at Johnson Woods Orrville Ohio. One of the key sites in the paper and one of the key sites in the Midwest. Originally cored by Ed Cook (Lamont-Doherty Tree Ring Lab) in 1980, the site has been updated by The College of Wooster Tree Ring Lab and by Justin Maxwell at the Indiana University Tree Ring Lab. Students sampling the remanent white oak stand at Browns Lake Bog a site managed by the Nature Conservancy. 

Coring the second-growth white oaks in Wooster Memorial Park.

Another second growth site is within the Wooster city limits at the Kinney Field Park.

The College of Wooster campus maintains an impressive stand of old growth white oaks on its campus. Here members of the Holden Arboretum Tree Corps sample one the the impressive old trees.Secrest Arboretum (on the Wooster campus of the CFAES) is one of our favorite sites to cores trees. Many of the trees from  all around the world have lived in Ohio for over 100 years. Here one of the coauthors cores a white oak planted about 100 years ago.

A final word on this study. Future warming in the Midwest is projected to see increases in spring precipitation, likely decreases in late summer precipitation, which if coupled with an increase in maximum summer temperatures would increase the moisture stress on these trees. Our examination of these varying climate responses with respect to site characteristics and forest age can help future assessments of tree health and the forest’s ability to sequester carbon, as well as facilitate efforts to reconstruct climate by using a range of tree sites for intervals when sensitivity in old growth sites is lost.

These data from the sites in Northeast Ohio are available in the International Tree-Ring Databank maintained by NOAA and many of these records have been incorporated into the North American Drought Atlas contributed to the larger climate science community by Ed Cook and colleagues.

References:

Acknowledgements: This work was funded by The College of Wooster, NSF Geopaths and NSF – EAR 2039939 grants.

Wooster Earth Scientists traveled to Erie PA to attend the joint Northeast /North-Central Geological Society of America for a weekend of geology talks, posters and fieldtrips.

Above Grace presents her senior Independent study research entitled “A LAKE RECORD OF ENVIRONMENTAL CHANGE IN NORTHEASTERN OHIO SINCE EUROPEAN COLONIZATION” abstract here.

Proto presented ALASKA’S FIRST WESTERN RED CEDAR TREE-RING CHRONOLOGY described here. 

Proto here describes the winter signal that they discovered in the tree-ring record of the red coastal cedar from Southeast Alaska.

Lauren describes her Alaskan tree-ring work on the southern coast of central Alaska.

Lauren’s poster FIVE NEW MOUNTAIN HEMLOCK TREE-RING CHRONOLOGIES FROM SOUTHEAST ALASKA: NEW RECORDS OF CLIMATE – here she just shared the research with alum Nick Fedorchuk who now a professor at Southern Connecticut University.

Evie (foreground) with Anika and Ihaja looking on – explains their work on four deciduous conifers from Secrest Arbooretum. These trees may be key players in future high CO2 environments in a warming world as they were in the past. the title: USING DENDROCLIMATIC ANALYSIS OF EXOTIC DECIDUOUS CONIFERS IN AN ABORETUM TO DOCUMENT TREE GROWTH IN RESPONSE TO CLIMATE CHANGE, NORTHEAST OHIO, USA described in their abstract here. 

Amanda’s IS work is explained in this poster and her lightening talk is shown below. The title CAN VOLCANIC EVENTS FORCE DECADAL COOLING IN THE NORTH PACIFIC? is described in this abstract.

Linking short scale (1-2 year cooling forced by volcanic events) appears to serve to force cooling SSTs in the North Pacific that can persist for a few decades.

Wooster faculty also presented results of research – above Dr. Eva Lyon describes her work on a Pleistocene lake from West Virginia. Her title PALEO-LAKE BUCKEYE: A NEW SEDIMENTARY ARCHIVE OF PALEOENVIRONMENTAL CONDITIONS ACROSS THE PLEISTOCENE-HOLOCENE TRANSITION IN THE CENTRAL APPALACHIAN MOUNTAINS and abstract can be found here. . Wooster students are now working on these lacustrine sediments. G. Wiles also presented: PROGRESS IN USING TREE-RING CHRONOLOGIES TO RECONSTRUCT LAURENTIAN GREAT LAKE LEVELS, which focused on reconstructing Lake Erie levels using tree rings. Tim Fisher (U.Toledo) also presented collaborative work with Wooster on Lake Erie water levels here.

Drs. Lyon and Wiles attended a fiedtrip to Presque Isle during the meeting to examine the coastal erosion. This trip will serve as a planning trip for a potential future fieldtrip of a combined course in Paleoecology and Hydrology in the fall of 2025.

A breakwater offshore dampens the power of the waves and the piles perpendicular to shore slow the longshore drift and sediment loss of the beach.

This van at the visitor’s center is a map of the features viewed on the trip – Presque Isle and, on the Canadian side, Long Point, are spits and tombolos located on glacial moraines that formed about 14,000 years ago during deglaciation of the Laurentide Icesheet.

It was a lively group – of students, professionals and faculty.

Wooster Memorial Park has been a great resource for The College of Wooster Earth Sciences (ESCI), Biology among others. Here the ESCI course in Paleoclimate, under permit from the Friends of Wooster Memorial Park, sampled 20 second growth Eastern Hemlock with the aim of determining the climate response of the species in the Park. A recent publication by the Wooster Tree Ring Lab incorporated results from past sampling in the park that was concerned with the changing climate response of white oak trees. This oak study can be found here Wiles et al., 2025.

Lidar Map of Wooster Memorial Park – the green field in the west of the park is the approximate location of tree-ring sampling.

The class took advantage of a spectacular day for the sampling.

Nick demonstrating the coring technique using an increment borer.

Another perfect core, once trained, the five groups went into sampling mode.

For most of the group, this was their first experience coring and it was clear some were naturals at the technique.

First-ever core reveal photo – a proud dendrochronologist.

Another first.

Coring for the first time.

Coring and at the same time keeping a sharp eye out for wildlife.

A first – ever core safely archived in a reusable plastic straw.

Even the TA was caught working in this photo.

Deep in the hemlock forest – group three assesses another hemlock.

On the cliff’s edge tree workers and tourists confer.

Another core reveal photo.

Here five sizeable hemlocks lie in a row – blown down by the summer storm of 2022.

All the root throw from hundreds of downed trees is significantly changing the sediment budget in the tributaries.

From the storms and trees killed by the emerald ash borer there is plenty of wood for log jams.

A portion of the park was used for raising shade trees back in the day. Here is one of the shade trees that remains.

Reflecting on the completed coring and anxious to get to the lab work.

One of the many, diverse rocks in Rathburn Run. Special thanks to the Friends of Wooster Memorial Park and the City of Wooster for maintaining the park and allowing us to sample there.