By Leah Brooks, Marketing Coordinator at Mt. Cuba Center
Since the onset of European colonization and the subsequent exclusion of forest fires, historic fire regimes in Eastern North America have been disrupted or halted. To see an example of how deeply entrenched the aversion to fire is in the public collective, you need look no further than one of the most recognizable and the longest-running public service announcement campaign featuring Smokey Bear. Created in 1944 with the popular slogan, “Only you can prevent forest fires,” this wildfire prevention campaign has educated millions of Americans about fire safety in natural areas. The language of the slogan was broad, implying that all fires occurring in forests are detrimental and should therefore be prevented. This left no room for nuance about fires set intentionally in order to manage lands. In 2001, Smokey’s catchphrase was updated to read “Only you can prevent wildfires.” The new slogan helps clarify that the campaign’s goal is the prevention of unwanted, human-caused wildfires rather than the elimination of safe and intentional prescribed fires.
Prescribed fire can be an important tool for land management and conservation. Many vegetation communities and habitats across the United States evolved with, and were driven by, periodic disturbance from low and high intensity fires. Low intensity fires burn at lower temperatures and thus don’t cause as much harm to plant tissues as high intensity fires do. Mature fire-tolerant species such as red oak (Quercus rubra) and mountain laurel (Kalmia latifolia) are able to survive and recover from low intensity burns, while species that are not tolerant succumb to the fire. Without periodic fires, we are losing fire-adapted vegetation and forest communities through the process of mesophication.
Mesophication is a positive feedback loop in which suppression of fire allows tree species that are fire sensitive and shade tolerant to establish and grow. These mesophytic (moist-loving) species create a dense canopy that causes the forest floor to become cooler, shadier, and more moist. In such conditions, leaf litter becomes less flammable and is less likely to catch fire and burn. This in turn leads to more fire suppression, and the cycle continues, driving plant diversity to decline as fire-resistant species disappear from the area.
The decline of fire-resistant trees such as oaks (Quercus spp.) and hickory (Carya spp.) and the rise of mesophytic species such as American beech (Fagus grandifolia) and tulip poplar (Liriodendron tulipifera) has far reaching ecological consequences. Oak and hickory are important keystone genera that support more wildlife interactions than American beech and tulip poplar. When tree density trends more towards mesophytic species, we don’t just lose the fire-tolerant species, we also lose the animals that have co-evolved alongside and rely on them for survival.
By implementing intensive forest thinning and reintroducing prescribed fire at historic fire regime intervals, Mt. Cuba Center is working to reverse the mesophication process in some of the Dry-Mesic Oak Forest areas in our Natural Lands. Management is informed by site-specific historic vegetation analyses and regional fire scar and dendrochronology records. The first year of management activities included initial mechanical and chemical removal of unwanted plant species and the reintroduction of prescribed fire. Pre-burn vegetation monitoring in the understory and overstory shows us what the future species composition would have been had no action been taken, while post-surveys show an initial response to our management techniques. The work to transform the oak forest community guides adaptive management, informing the efficacy of management techniques and projecting the trajectory of the future forest.
The results comparing one year of pre- and post-burn data show that thinning and burning successfully altered the existing tree canopy. Burning restarts the understory by cycling nutrients from the fire, reducing competition, and opening light gaps. Our Natural Lands team will continue to manage the resulting flush of tree seedlings by caging oaks to prevent deer browse. Mt. Cuba’s goal is to shift the forest composition to be more heavily dominated by red oak (Quercus rubra) and chestnut oak (Quercus montana). In the future, we plan to return the historic fire interval in these oak woodlands by burning approximately every 15 years. We also plan to compare and contrast this site to other sites across Mt. Cuba’s property, including sites that are more constrained, where we only have capacity to thin the site. This work will improve forest quality by enhancing habitat in suburban forested areas, and help us understand how restoration in suburban properties can be implemented to optimize forest restoration despite site constraints.