Big Oak

Big Oak in Autumn by Cathie Bruner

This spectacular white oak, with its wide-spreading branches, could tell us so many things about the past if only we were able to hear its stories. While we cannot say for sure if the surrounding vegetation was prairie, savanna, or very open woodland, the outspread branches tell us that the land was drenched with sunlight for many years.

Trees only invest this kind of energy in spreading out branches if they receive sufficient calories from the sun to justify the investment. Trees that grow in a forest grow straight and tall before they put out branches to capture light. Trees in a field or prairie can afford to start sending out branches much lower on their trunks, because they don’t need to compete with their neighbors to capture a lion’s share of the local energy budget.

In historic aerial photographs of the Jackson Farm, it’s possible to distinguish this large tree surrounded by fields (labeled “Second Point Oak”). Because growing conditions over the years affect the size of a tree, it is difficult to determine age based on size alone, but we know that it was growing here before the land was farmed. To assess its age more accurately, we would need to core the trunk-an invasive procedure we do not want to risk because it might introduce disease or insects that could shorten the life of this magnificent tree.

Big Oak in Winter by Bryn Scriver.

Surrounding trees and shrubs sprang up after grazing and cultivation ended on this land, something you can see if you compare historical air photos from 1927 to 1999. The dense growth not only crowded this tree, but blocked the sunlight needed to keep it alive.

In 1996, to initiate a new ecological management plan written by ecologists Virginia Kline and Brian Bader, the UW Grounds Department removed green ash, American elm, and choke cherry from this site so the outstretched limbs of this ancient tree would once again receive the sunlight that keeps them alive.

Since then, Preserve staff and volunteers have been expanding the protective circle of restoration, removing invasive plants and replanting the area with savanna and open woodland species that perhaps long ago shared the soil with the very old roots of this special tree.

A tour group passes under the Big Oak. Photo by William Cronon.

In a sense this tree isn’t just a symbol of the Lakeshore Nature Preserve’s past. We hope it is also a prophecy of the Preserve’s future.

Savanna vegetation was once much more common in the area of the UW campus than it is today, with large open-grown oak trees like this one widely spaced in a landscape of prairie grasses and sedges. (See the original land survey notes to see how it looked to the first surveyors of this land.)

Restoring savanna is in many ways a much more difficult challenge than restoring prairie, but we are hoping that the few open-grown oaks that still remain in this part of the Preserve can serve as the starting point for a gradual transition toward savanna in certain areas.