Case Study: American Beech at Rock Creek Park

American beech (Fagus grandifolia) leaves in early autumn.
Photographer: Gary Fleming
Consider the rise of American beech at Rock Creek Park. Already common throughout the natural upland communities of the park, it may become even more abundant in the future, shifting the species balance in several natural communities at Rock Creek Park. Why? American beech has several advantages—historic and new—over other tree species in the existing upland forests at Rock Creek Park.

  • American beech does not need direct sunlight, but can both germinate and grow to reproductive maturity in the shade of other established trees. (An oak, by contrast, may spend its whole life as an immature sapling if a sunlit opening doesn’t appear in the leafy canopy above!)
  • American beech doesn’t require nutrient-rich soils (which are in short supply in Rock Creek Park).
  • It can grow on very dry hillsides (which are bountiful in Rock Creek Park).

A smooth-barked American beech tree (Fagus grandifolia) among younger beeches in a winter forest.
Photographer: Sam Sheline, courtesy of NatureServe
That has always been true. What is new are the environmental pressures:

  • There have been no significant fire disturbances in Rock Creek Park since it was established in 1890. Fire historically kept American beech out of dry, fire-prone hilltops. (Beech's thin bark offers it no protection in fire.)
  • Disease removed American chestnut from hillside forest canopies a century ago, leaving gaps for other sun-tolerant species to fill. American beech—tolerant of either sun or shade—was already present in the shady subcanopy of some of those forests, and was a natural replacement for American chestnut (along with oaks).
  • The population explosion of hungry white-tailed deer in the late 1900s has seemed to give American beech a significant regenerative advantage over oaks and other tree species whose seedlings deer more readily eat. (Learn more about the population dynamics of white-tailed deer at Rock Creek Park.)

American beech is a beautiful and important tree in many natural communities at Rock Creek Park, but the overall health of these communities is dependent on a natural mix of tree species. If American beech became the sole dominant canopy tree species, then the whole forest could be threatened in the event of fire or the disastrous beech bark disease. Unless a more natural mix can be restored, however, American beech might be the most likely native tree, in the long term, to dominate many of the future forest stands of Rock Creek Park.