White oaks are a keystone species in the Central Hardwood Forest Region, for many reasons from aesthetics to cultural, ecological and economic value. White oak is used in a variety of commercial forest products from whiskey barrels to flooring, cabinetry and furniture as well as pulpwood for paper production. The species also has importance for wildlife as both a source of food and shelter.
Despite its widespread range across much of the central and eastern United States and long lifespan (surpassing 200 years), white oak has historically been managed by generalized prescriptions developed on red oaks. This is in part due to the more rapid seedling/sapling aboveground growth of northern red oak compared to white oak, which has made it an easier study subject. White oak will commonly wait several years to start its aboveground growth, instead putting its resources largely into roots, while red oak is more immediate.
A newly-funded HTIRC project, co-led by Drs. Morgan Furze and Mike Saunders, aims to change reduce the knowledge gap surrounding white oaks, specifically looking at the physiology of white oaks and the trees’ response to
drought and prescribed fire.
“I was drawn to this project because naturally I could see how physiology could help solve this problem of understanding how white oaks successfully regenerate,” Furze said. “Mike Saunders is an expert on white oak regeneration and can speak to people about forest management in a way that I cannot. I can bring the physiology part to it, and tell you how the plants work and function in response to their environment. Bringing together the fundamental physiological perspective with someone who has an amazing forest management and applied perspective, we can have a bigger impact with our work.
“White oaks are declining and being replaced by other tree species like maple. In order to have forests that are canopy dominant for white oak, we need to rethink the management practices we are using and that is what we hope our study will provide some insight into. We’re hoping that by understanding the physiology of white oaks and how it impacts their ability to regenerate and persist, we will be able to improve white oak management.”
The project “Understanding the Role of Carbohydrate Dynamics on White Oak Regeneration” will build upon the master’s thesis project of Eli Gafney (2025), which evaluated artificial white oak regeneration along light and competition gradients. Gafney’s work studied the response of planted white oak seedlings in an enrichment/underplanting contest. Seedlings were planted under a variety of light and understory competition conditions. In a shade house study, Gafney compared white and northern red oak response to a similar range of light conditions and used honeysuckle as a competitor. This allowed for physiological measurements and more detailed analysis of biomass allocation.
In general, this project will look at how planted (or artificially regenerated) white oak seedlings respond to various stressors.
“My hope is to refine the growing conditions needed for successful artificial regeneration of white oak,” Saunders explained. “What management treatments are needed? When are they needed? For how long? And how can we best spend resources to favor white oak.”
When a tree photosynthesizes, it makes sugars that it can convert into starch. The sugars and starch can then be used for a number of things from growth to respiration, reproduction and chemical defense production, but they can also be stored away for later use.
“Think of it like an emergency fund,” Furze explained “Plants can put away those carbohydrates into their savings bank and when a stressful situation comes along where they can’t photosynthesize and make new carbohydrates, they can reach into that savings account and pull out those stored carbohydrates. That will allow them to survive and persist until conditions become favorable again. It is very much analogous to animals storing fat. If you didn’t eat lunch for some reason and you have a situation where you need to do something stressful to your body, hopefully you have some fat reserves that can bide you some time until you have a chance to eat your next meal.”
So, what can researchers learn from carbohydrates in white oaks?
White oaks once dominated eastern North American forests, but they have been declining over time due to changes in land use as well as changes in the environment. In order to regain canopy dominance, white oak management must prioritize their regeneration. One way that oaks have been found to survive and thrive is through the use of fire.
“White oaks are adapted to rely on fire disturbances to maintain their dominant position in the forest,” Furze said. “In many cases they will actually survive, thrive and regenerate better in this environment, as it opens the forest canopy. They have less competition from their neighboring trees and invasive species, creating a very favorable environment for white oak seedlings to establish and grow up. When a white oak gets burned by fire, it resprouts, which means it regrows new shoots from the pre-existing plant. That resprouting process is driven by carbohydrates. We know that the carbohydrates that are stored in the roots are going to help build the body of the new growth, but we really don’t have any idea about how white oaks store and use their carbohydrates specifically. We want to know what carbohydrates are doing in white oaks and also how that changes and influences resprouting success as they respond to prescribed fire and drought and other stressors.”
The first step in that process is gathering root samples from existing white oak and red oak plots, approximately three years old, to get baseline carbohydrate measurements. Then, these can be compared to show species similarities and/or differences. Root samples are being analyzed for sugar and starch measurements. They will be retested again over time to see how the measurements change naturally when seasons change. Although researchers are taking samples from the roots, it is not enough to damage them. The sample size needed to test carbohydrates in roots is around 10 milligrams of dried and ground tissue, or about the amount of salt you can pinch between two fingers.
Part of the existing red and white oak plot at Lugar Farm, which is being measured for carbohydrates in the roots, also was burned in a top kill fire this past spring to simulate surface fire conditions. The resulting resprouts also will be measured to see their carbohydrate levels following fire.
“As those sprouts become able to photosynthesize and make new carbohydrates, we are curious if the emergency fund in the roots will refill,” Furze explained. “We will burn them again eventually and see how many sprouts come up the next time. Will we see a pattern of the trees using up the reserves and then refilling them or with repeated fire will they just deplete their reserves and never replenish them? These results could allow us to determine if carbohydrate reserve levels influence resprouting and sprout success. We are also interested in understanding the timing of burns in relation to other stressors in the environment such as drought.”
The second part of the project is taking place in a greenhouse, where some white oak seedlings will first undergo a simulated burn by way of a blowtorch, while others will not be burned. All of the trees will then be placed back in the greenhouse where some trees will receive regular water supply, while others will be placed in simulated drought conditions.
“Our experimental design with some droughted and some not and some treated with fire and some not will give us several combinations. Then, we can tease apart the impacts of drought versus fire or the combined stressors,” Furze shared. “We’re interested in looking at what happens if prescribed burns occur in a drought year. What impact does that have on the capacity to resprout and the success of new resprouts? We are doing burn then drought, but you could also think about it the other way, too. If there has been a drought, should you burn now or give them time to recover before burning.”
While the findings of the experiment are still a few years away, possible outcomes from the project could go a long way toward understanding the resilience of white oaks. Studying carbohydrate dynamics and gaining knowledge about what is going on in the root system of white oaks in general can give researchers a better understanding of the species’ physiology. This, in turn, will allow for forest managers to make better predictions regarding their resilience in the face of other environmental stressors.
“At the bare minimum, I hope this project will open people’s eyes to the fact that we should potentially reconsider forest management practices to be more species specific and perhaps move away from applying management practices learned from red oak to white oak,” Furze concluded. “An amazing end goal would be if we find something about the timing or frequency of prescribed burns that could change how forests are managed.
“What we are doing now is the first step. Later we can explore this across different aged stands and different environments and in forests with different species composition. There are many biotic and abiotic interactions that will help build a bigger picture over time, but, for now, we will hopefully increase our foundational knowledge about white oak regeneration and how things work.”
