Mesophication

Mesofication is a term coined by Nowacki and Abrams (2008) describing the widespread conversion of fire-maintained open prairie, savanna, and woodland to closed mesic forest in the Midwest and Eastern United States. They explain the process following fire suppression, whereupon “fire-maintained open lands converted to closed-canopy forests. As a result of shading, shade-tolerant, fire-sensitive plants began to replace heliophytic, fire-tolerant plants. A positive-feedback cycle – which we term “mesofication” – ensued, whereby microenvironmental conditions (cool, damp, and shaded conditions; less flammable fuel beds) continually improve for shade-tolerant mesophytic species and deteriorate for shade-intolerant, fire-adapted species. Plant communities are undergoing rapid compositional and structural changes, some with no ecological antecedent. Stand-level species richness is declining, and will decline further, as numerous fire-adapted plants are replaced by a limited set of shade-tolerant, fire-sensitive species. As this process continues, the effort and cost required to restore fire-adapted ecosystems escalate rapidly.”

This process of mesophication is happening all over the Midwestern and Eastern US, on practically any land not in agricultural production. Drive through the driftless area in Southwest Wisconsin and see the wooded hillsides where maples and buckthorn are replacing the once plentiful bur oak groves. Look around at state, county, and city parks like Governor Nelson, Blue Mounds, Indian Lake, and Elver Park. Look even in our restoration areas like the UW Lakeshore Nature Preserve and Arboretum. Look everywhere tractors fail to plow, fires fail to burn, and herbivores fail to graze and you’ll find land in varying phases of mesophication; losing diversity and slipping further into ecological dysfunction.

We can restore functional savannas, but it will require clearing the woody vegetation, and opening up the ground to sunlight so grass can grow. Goats can help with brush clearing and cows/sheep/horses to maintain understory grasslands. But we have to do it now. The longer we wait, the more fragile the last remaining oaks become, and the more defunct the remnant seed banks in the soil become. Once mesophication is complete and the oaks have disappeared, we’ll have lost our opportunity to restore one of the most beneficial, functional, and beautiful ecosystems that once covered the entire Midwest.

Nowacki, G.J., and M.D. Abrams. 2008. The Demise of Fire and “Mesophication” of Forests in the Eastern United States. Bioscence 58(2): 123-138.

Comments

Tony Jovan

Here in Toronto (Ontario), the Parks Department has planted maples in a Black Oak savanna (High Park). The maples are now reproducing everywhere, at the expense of the herbs, forbs and oak trees. They have introduced prescribed burns into the land management regime, however they cannot understand why the fires do not burn nor carry. Hmmm.

pclarkallen

Interesting to plant maples in a black oak savanna. Black oaks generally grow in dry and sandy soils, which are no good for maples. But if the maples are reproducing everywhere, they’re obviously doing okay. There is a similar site here at UW’s Arboretum, where maple and basswood were planted in the 1960s underneath open-grown white oak trees to “give mother nature a boost” and speed up forest succession. Tragic. Maple leaves are moist and decompose rapidly, making them poor fuel for understory fires. Oak leaves are dry and recalcitrant. They will last for years dry on the ground waiting to burn. It’s hard to maintain an open woodland with maples in the mix. They are just too good and creating moist and nutrient rich conditions around them.