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  • Mary Arthur

Kentucky Roots

Updated: Dec 15, 2022

After 30 years as a Forest Ecologist at the University of Kentucky (UK), Mary Arthur is shifting her life's focus to a "retirement" stage. She took some time to reflect on her incredible, influential career for our new CAFMS blog. Read the story behind the science, below.

When I moved to Kentucky with my 6-month-old daughter on New Year’s Day 1993, the U-Haul loaded with all of our belongings broke down a mile from our new home in frigid weather that dropped to -4F overnight. We found someone to tow the truck to our new (old) house, where we found that the roof was leaking into the downstairs bedrooms. Welcome to Kentucky! This was an inauspicious start, especially since before interviewing for an Assistant Professor position at UK I could barely find Kentucky on a map. Fortunately, I like the cold and if you love forests and the intricate dialogue between humans and the environment, Kentucky has a way of growing on you.

As a new professor at a land-grant University, I was tasked with identifying a research focus that is relevant to the region. I had worked in New York, in northern hardwood forests, and Colorado, where I conducted my PhD research tracing nutrients through a subalpine spruce-fir forest. I initially had little to go on as a starting place for my Kentucky-based research, and a very short timeline to sort it out! The high tree species diversity of Kentucky’s forests alone overwhelmed my tree ID skills; I felt like I was starting at zero. Happily, several faculty saw my need for local knowledge, helped me hone my ID skills in a new forest, and shared their knowledge of the ecology of the region.

I quickly discovered the rich human and ecological history held within Kentucky’s forests. Unraveled through information from archaeology, palynology, forest ecology, and historical accounts, these histories shed light on the complicated impacts that humans have had on forest structure and species composition over thousands of years. In the early 1990s, much of what I now know about the presence of Indigenous Peoples and their use of forests was still emerging, whereas the impacts of Euro-Americans were more readily-available in written histories and thus more visible on the landscape. As I was casting about for research ideas centered in Kentucky to complement my research program in the northern hardwood forest, I looked for opportunities to learn more about the ecological impacts of disturbances mediated by current human populations. A colleague mentioned that in the Red River Gorge Geological Area (RRGGA) of the Daniel Boone National Forest (DBNF), ridgetops were increasingly dominated by white pine, and that this increasing prevalence was linked to the absence of fire on those uplands. Forest Service managers were looking to partner with a researcher at UK to experiment with the use of prescribed fire to reverse this encroachment.

The expansion of white pine on ridgetops had been linked to active suppression of fires since the 1930s, based on former U.S. Forest Service (USFS) employee Rita Wehner’s research dating white pine trees on these ridges. I soon learned that neither the historical and ecological role of fire in these ecosystems, nor the impacts of fire suppression, had been firmly established as key factors influencing forest dynamics in this region. I jumped into a collaboration with the DBNF with great excitement to be starting on my Kentucky-based research, and a good amount of naiveté for where it would all lead. So much of what I learned about the forests in the RRGGA, I learned from the District Ranger Donnie Richardson, who gently and respectfully shared his decades of on-the-ground knowledge with me and encouraged and supported the research. As it turned out, this initial foray into prescribed fire research yielded the clearest results of my career: prescribed fire is highly effective in killing white pine trees less than 6 inches in diameter and 30 years of age; repeated every 10-15 years, the understory can effectively be kept free of new white pine seedlings and saplings.

That initial study with its clear results opened the door for a central focus of my career by revealing that white pine was just one small element of the forest dynamics unfolding in these forests in the absence of fire. In retrospect, it was apparent that white pine was just the flag, visually signaling the change that was afoot. As an evergreen, it was easy to spot in the understory and much easier to see than the shifting composition of understory deciduous tree species; a phenomenon that was later described as “mesophication” by Nowacki and Abrams (2008).

We had essentially solved the fire riddle related to white pine, so I adjusted my focus. I found a new set of important questions about how fire influences the dramatic increase in the mesophytic hardwood species like red maple. This increase lowers light levels to the point that oak seedlings can't develop to saplings or grow into the overstory. At that point, the focus of my research shifted to exploring how prescribed fire, and repeated fire, altered forest regeneration patterns and longer-term regeneration processes. Through this research I was able to initiate a vital and long-term collaboration with the DBNF. We experimented with repeated prescribed fire and a fire-free interval to examine the impacts on upland oak forest dynamics. Our research on the effects of prescribed fire on forest stand dynamics and oak seedling establishment and development unfolded over 25+ years and demonstrated that prescribed fire has modest positive effects on oak regeneration, particularly notable after a fire-free interval. Perhaps more importantly, the continued absence of fire clearly leads to continuous in-growth of mesophytic, fire-sensitive species, like red maple, in the understory and into the canopy. Thus, the failure to burn, or disturb these stands in other ways, will lead to the continued closing of the canopy and reduced oak recruitment. Beyond the relationships between fire and oak regeneration, our findings also demonstrated how the absence of fire alters forest hydrology, leaf litter composition and decomposition, and fuels.

As we were developing this important body of research on prescribed fire, the forest managers kept sharing different, more positive stories about the effects of fire on oak regeneration. I thought that their insights might be tied to sites where uncontrolled fire, or wildfire, had been present. I hoped for an opportunity to study the effects of wildfires, which typically burn with more variable severity than prescribed fires and include some patches of very high severity. In 2010, the Fishtrap wildfire was accidentally started while a fire ban was in effect during an exceptionally dry fall in the RRGGA. It burned 674 ha of forest land over two weeks, from late October until November 9th, before it was fully contained. Despite hundreds of campers sleeping nearby when the fire started, everyone was safely evacuated. This fire provided an opportunity to examine the ecological effects across a gradient of burn severity because it occurred primarily on US Forest Service land, where our partnership paved the way to learn about the impacts. My research group initiated a study of the effects on species composition, regeneration, and forest dynamics, in close collaboration with DBNF personnel. Key findings from this work illustrated that higher fire severity is linked with greater regeneration success of oaks and pines, whereas mesophytic species such as red maple are agnostic to fire severity, regenerating with equal success across sites regardless of burn severity. Current research on the Fishtrap site (led by my final MS student) explores the relationship between burn severity, forest stand structure, and microclimate, with the aim of learning more about how rapidly changing climate in combination with fire may alter forest conditions and species composition.

And, as I clean out my office, including data files I found from my PhD dissertation research conducted more than three decades ago,- I am reflecting on the past 30 years as a Professor, returning again and again to a few questions: How does it all add up? What were the most important contributions of my career? How did I contribute to our understanding of fire in upland oak ecosystems of the Southern Appalachian region and the unfolding dialogue among managers and scientists around the use of prescribed fire? And, what were the key elements to building a fire ecology research program in Kentucky that helped to inform fire management practices in the region?

From my current vantage point, much of what “adds up” to define a career well spent was being in a position to nurture undergraduate and graduate students in realizing their interests, passions, and abilities. I'm proud of being a part of launching future forest ecologists and natural resource professionals, a good many of whom eventually became colleagues in positions with state and local agencies and non-profits. Of course, more closely tied to what I was explicitly hired to do, to be a forest ecologist with a research program at a land-grant university, was the steady stream of research grants, scientific publications, research presentations, and other metrics of a successful research career. Fortunately, the two were inextricably linked: running an active research program led to engaging students in the pursuit of answers to research questions that helped inform management decisions. My research program gave many students the opportunity to do field work, learn how science is done, and gain experience in their chosen field. Indeed, one of the great things about being a student at a land-grant university is that faculty are all fully engaged in research, and that research finds its way into the classroom and onto field trips, and provides opportunities for experiential learning.

Throughout the 25+ years of research collaboration with the USFS DBNF, we have developed one of the longest-running fire research programs in the southern Appalachians. This partnership, and the work we have done together, has helped build our understanding of fire ecology in upland oak ecosystems. Along the way, we refined our understanding of the oak-fire hypothesis (Arthur et al. 2017) with the (now obvious) revelation that it isn’t fire, per se, that alters stand dynamics through impacts on seedling regeneration. It's the interplay between the impacts of fire disturbance and barriers to regeneration at different life stages of each species on the landscape. The USFS partnerships have been centered in Kentucky, where managers in the Cumberland Ranger District and the Supervisors Office of the DBNF worked closely with my team to identify sites for experimentation, developed goals for prescribed burning, implemented the burns, and provided financial and in-kind support as available. Notable partners in this work were former DBNF Fire Management Officer EJ Bunzendahl and Cumberland District Silviculturist Jeff Lewis, DBNF Soil Scientist Dr. Claudia Cotton, DBNF Botanist David Taylor, and many others. These partners played an essential role in sharing the findings with their networks of forest and fire managers across agencies and NGOs. This work was funded, in part, by two grants from the Joint Fire Science Program, which supported research conducted by my research group and the Bent Creek Experimental Forest, in collaboration with Dr. David Loftis and Dr. Tara Keyser.

Our work together since the early 1990s was enormously impactful for its contribution to the emerging literature on fire and upland oak stands, but perhaps much more so because of the close collaboration between

my research team at UK and forest managers in the DBNF. Because forest managers were invested in the research and involved at every step from experimental site selection to burn implementation, this long-term collaboration helped to shape the direction of fire management in this region. As it turned out, an active research program was a powerful vehicle for collaboration in addressing interesting ecological questions that helped to inform management decisions all while training the next generation.

Woman smiling, standing in a forest, wearing a purple jacket
Mary smiling while visiting some of her remaining study sites in eastern Kentucky.

I couldn’t have asked for more from my career in Kentucky. And over these past 30 years, Kentucky has grown on me to the point that, as I step into retirement, which I prefer to call “the Third Act of my life,” I intend to stay here. I love the Kentucky woods and have planted firm roots here, both relational and arboreal.

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