Updating The College of Wooster Oak Tree Ring Record

Guest blogger: Adam Wood

The Modern Climate Change course in the fall of 2026 (MCC26) took on the task of updating the campus oak ring-width tree ring chronology. It was last cored over a decade agoand is one of he few sites of Ohio’s remaining old growth (those trees greater than 250 year old). Not only is 2026 the 250th anniversary of the nation, it is also the first year of the College campus as an arboretum – the Abbey Arboretum.

Nick Wiesenberg (center) directs the coring operation.

Coring Trees on Campus:
Home to several old growth white oak trees, The College of Wooster has “tree witnesses” to the last 250 years of changing climate and land use. Old growth trees, specifically those of the white oak (Quercus alba) have been found to date back to the late 1600s CE in Ohio. Using dendrochronology the  MCC26 class were able to count the individual tree rings in each tree core and assign calendar years to each growth band and combine this data with previous year’s efforts to update the college’s tree ring chronology to 2025.

Methodology:
On September 28, 2026, the MCC class with the help of COW technician Nick Wiesenberg used increment borers to core the oaks. In total, 22 trees were sampled for the update.

Adam, who is working on assembling all the old growth sites across Ohio for his
senior Independent Study, cores one of the 300 year old oaks on the campus.

Li, our cartographer, takes a core using an increment borer.

Maddie extracts an additional core as Li records the vital meta data.

We recruited Arjan (left) and Cooper also Earth Science majors to help the effort.
Arjan is doing his IS on natural springs in the Wooster area and Cooper is mapping
and working out the geologic history of Fern Valley, The College of Wooster Field
Station in Holmes County. Many thanks for their help.

Lab work:
The cores from these sites were then sanded and the ring widths measured in the COW Tree Ring Lab. Cores were initially dated by manually counting the number of rings. For precise ring-width measurements (0.01 mm) we used the VELMEX measuring tables in the lab, computer software tracked the distance between the ring boundaries writing the data to digital files. The cores were then crossdated with previous collections from the campus to produce the indices of the ring-width chronology.

Madeline measures one of the older oak cores.

Maddie’s first core.

Li marks a core prior to measuring.

Adam is a veteran in the lab, here marking one of the campus cores.

The New Chronology:
The resulting standardized indices compiled into chronologies end in 2025 the final full ring measured. Due to low sample depth in the earliest dates the series was truncated at 1720 CE. The chronology now spans 1643-2025 and is a combination of 57 cores. A release (marked increase in ring-widths) at 1is clear (graph below), as well as the 1895 drought. The release coincides with the establishment and initial construction of The College of Wooster campus. Prior to the establishment of the College, the land was a 20-acre hilltop of oak trees grassland (Gasbarre 2019). The construction of the College is likely the reason for the release in 1866, as cutting of the canopy would have permitted access to greater sunlight and nutrients for the oaks, and thus wider rings. Prior to 1866, the trees did not exceed a width of ~1.3 mm. The sudden rise in width, nearly reaching 2.5 mm, also records other events like in 1895 drought.

Next steps:
The class is now examining the tree ring series as a record of droughts, past volcanic events linked to changes in hydroclimate, identification and significance of the releases, as well as the possible changing climate signal in the tree growth. In addition, thanks to the assistance and guidance of the Special Collections librarian, Rebecca Roper, the MCC26 class was able to review items from the college archives pertinent to the history of the college and its trees. Additional linkages can be made by comparing our tree ring data to archival records.  For example we know that the college faced a deadly onset of Dutch Elm disease around 1968 and into the 70s’. According to a report at the time from the Wooster Reporter, in the spring of 1970, the college was forced to cut down multiple of their elms which sat on Quinby Quadrangle (the front of Kauke Hall) which may be evident in our record. Furthermore, reports of the Chapel construction affecting the water table and documented lightening strikes on trees may be link to some of the tree ring variability.

Acknowlegements:
Special thanks to Nick Wiesenberg (Departmental technician) for his help. Special Collections librarian Rebecca Roper helped our historical efforts and Phil Olsen, director of grounds, granted us permission to core these oaks.

The collection archived in the Wooster Tree Ring Lab. The data from this update will be contributed and added to the existing tree-ring data archived here.

Source: https://woostergeologists.scotblogs.wooster.edu/2026/09/25/updating-the-college-of-wooster-oak-tree-ring-record/