This isn’t a post of how or what to do in restoration work. It’s a post pondering terminology. It’s important to have the right words to describe and communicate about situations and certainly it’s fun to be the inventor of these words! But we must critically evaluate these words and their meaning. Applying them at face value could misguide your restoration plans. Let’s dig in!

Mesophication is a hypothesized process coined to describe a positive feedback cycle where a microenvironment of cool, damp and shaded conditions make the fuel beds less flammable (Nowacki and Abrams 2008). The term was coined in response to the fire suppression policies of 1920 and assumed that degraded oak habitats were uniquely degraded with fire intolerant, shade-tolerant tree species, defined as mesophytes, because of the lack of fire. This is a very narrow definition with implications that if fire is returned to the land, all will return to its original state. This very restrictive definition inadequately describes what is happening to our oak savannas and oak-hickory woodlands. Why? For one, this term focuses on trees and completely ignores the invasive woodies that dominate our understory.

A couple photos of our degraded oak hickory woods. There is so much more happening here than simply mesophication.

The term “mesophication” indicates that the degradation of oak habitats is primarily driven by shade tolerance and a lack of fire, yet there are mesophilic species, such as red maples, that can grow in shade conditions and will persist despite repeated burns because they are prolific resprouters (Woodbridge et al 2022).  This would be the same for the invasive woody species that are impairing our oak woods and the role of invasive species cannot be ignored. ,

Mesophication focuses on a single outcome due to a single cause and that is simply not the case with anything in nature. Our unhealthy oak ecosystems cannot be explained away with the oversimplified mesophication term. Additionally, our knowledge base has expanded since this term was coined; we know nature is complex and single-issue focuses are impractical and unwise. Moving beyond mesophication and fire reintroduction requires acknowledging these other drivers of oak woodland degradation. Let’s explore other challenges leading to the loss of our healthy oak landscapes.

Researchers have credited the loss of oak dominance to mesophication (aka fire exclusion) but fail to recognize other factors that favor the degradation of oak savannas and oak-hickory woodlands (Alexander et al. 2021). While fire may have been the primary disturbance in the 1800s that maintained our Driftless Area oak savannas and oak woodlands, that is not the case today and the emphasis on fire exclusion as the main driver overshadows these factors. (Alexander et al. 2021, Pederson et al. 2015).

Moreover, the focus on mesophication tends to gloss over the broader spectrum of degradation pathways in oak systems, such as soil compaction, nutrient cycling disruptions, and herbivory pressure from deer or other animals. These abiotic and biotic factors have resulted in highly variable responses in our eastern wooded areas (Woodbridge et al 2022). Our restoration strategies need to account for these other forces.

2. Topographic variation

The physical landscape — elevation, aspect, and topography — are other drivers to be considered since mesophication effects differ with steep slopes (Woodbridge et al. 2022)

3. Stand age

The degree of mesophication was greater in older stands and stands with more variable tree diameters than younger woods (Woodbridge et al. 2022).

A resprouting multiflora rose

We need to broaden the conversation beyond the oversimplifying, fire-centric narrative of mesophication. A more holistic view integrated the range of abiotic and biotic factors contributing to oak woodland and savanna decline. Going forward, considering these additional factors in restoration practices should provide a more comprehensive approach, balancing invasive species control, fire regimes, deer management, and site-specific interventions. This holistic perspective also suggests that while fire plays a role, it’s not a silver bullet for restoration, and targeted, multifaceted management strategies are necessary for success.

Mesophication is not the same as oak decline (Larsen et al. 2023). A general understanding of how oaks regenerate is needed but we’ll save that for another post. While oaks can withstand a certain intensity of fire, light and moisture are more important than fire. Oaks are a keystone species, a foundational genus, and the most important species for insect herbivores (Alexander et al. 2021). Their acorns are a vital food sources for at least 96 bird and mammal species (Alexander et al. 2021).

Focusing on mesophication as the sole driver of degradation neglects the complexities introduced by species such as honeysuckle, autumn olive, and multiflora rose. These invasives not only contribute to dense understory layers but also outcompete native species, further complicating the process of ecological restoration. Even when fire is reintroduced, the resprouting ability and persistence of these invaders make it difficult (but never impossible!) to reverse the degraded conditions.

Alexander, Heather D., Courtney Siegert, J. Stephen Brewer, Jesse Kreye, Marcus A. Lashley, Jennifer K. McDaniel, Alison K. Paulson, Heidi J. Renninger, and J. Morgan Varner. 2021. Mesophication of oak landscapes: Evidence, knowledge gaps, and future research. BioScience 71(5): 531-542.

Charton, Katherine T. and Ellen I. Damschen. 2024. Grassland woody plant management rapidly changes woody vegetation persistence and abiotic habitat conditions but not herbaceous community composition. Journal of Applied Ecology: 1-13.

Larsen, Chris PS, Stephen J. Tulowiecki, David Robertson, and Gregory J. Bream. 2023. Environmental drivers and species traits of mesophication and xerophication in forests of western New York State. Forest Ecology and Management 548: 121433. 

Nowacki, Gregory J. and Marc D. Abrams. 2008. The demise of fire and “mesophication” of forest in the Eastern United States. BioScience 58(2): 123-138.

Pederson, Neil, Anthony W. D’Amato, James M. Dyer, David R. Foster, David Goldblum, Justin L.  Hart, Amy E. Hessl et al. 2015. Climate remains an important driver of post-European vegetation change in the eastern United States. Global Change Biology 21(6) 

Woodbridge, Margaret, Tara Keyser, and Christopher Oswalt. 2022. Stand and environmental conditions drive functional shifts associated with mesophication in eastern US forests. Frontiers in Forests and Global Change 5: 991934.