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Rock Creek Park Natural Communities and More

Walking the trails of Rock Creek Park, it is easy to be taken with its wooded beauty. Whether or not you know anything about its plant communities, it is gorgeous greenery. But, as with all things in nature, if you look more closely, you will see layer upon layer of fascinating patterns.

What accounts for these patterns in Rock Creek Park? What can we learn about how things in nature interact with each other? What clues can we piece together that will narrate part of the story of Rock Creek Park’s natural communities?

Patterns

There are both subtle and bold patterns among the forests through which the park trails curve and climb. If you are familiar with any species of the trees, shrubs, or other plants around you, you may notice the abundance of some of those plants on certain parts of the landscape and their conspicuous absence on others. If you observe closely, you can find groups of plants that occur together regularly when certain environmental conditions are met.

Those groups of plants, in patterns that repeat themselves across the landscape of a region, are called “natural communities.” Ecologists study and name these communities—the Chestnut Oak / Mountain Laurel Forest, or the Red Maple Seepage Swamp, for instance. These natural communities function as essential habitat for wildlife species. Some animals may be found in most natural communities, some in only one or a few.

Some natural communities share broad characteristics and can be grouped together in what’s called an ecological system. An example is a River Floodplain Ecological System consisting of natural communities found on floodplains.

The more we learn about natural communities, the more fascinating they are—and the more precious, as we discover the roles they play in nature.

Explore these patterns:

Natural Communities

Ecologists recognize eight distinct natural communities that you can find along the trails at Rock Creek Park—some in the hills, some in the valleys. What parts of the landscape does each inhabit, and why? Explore each one below.

Sometimes the vegetation you see in Rock Creek Park will not look like any of the natural communities described above. Perhaps you are in a semi-natural community, a not-so-natural community, or a transition between communities. Find out more!

Explore All Natural Communities at This Location

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    Semi-Natural Communities

    Rock Creek park has many acres of semi-natural communities, which are plant communities growing in areas where the soil and/or vegetation was substantially disturbed in the past by a severe natural disturbance, or human activities such as plowing, logging, or quarrying.

    Because semi-natural communities are an integral component of the Rock Creek Park landscape, they are included in the Rock Creek Park Map, and are briefly described here. The vegetation in these areas is relatively young and is giving way (or succeeding) to other, more natural communities. As vegetation in a successional community changes over time, there is a turnover in the wildlife that use the area. For instance, grassland birds in an abandoned field eventually give way to woodland birds as the field succeeds to forest.

    As vegetation in a successional community changes over time, there is a turnover in the wildlife that use the area. For instance, grassland birds in an abandoned field eventually give way to woodland birds as the field succeeds to forest.

    The first three semi-natural communities on the list below have official names and codes because they are familiar patterns across the Mid-Atlantic and are part of an official classification called the USNVC. The last four help describe what is found at Rock Creek Park, but are not regionally recognized semi-natural communities.

    Explore semi-natural communities:

    Canopy tuliptree leaves unfurling
    New leaves of canopy tuliptree (Liriodendron tulipifera)  unfurling in spring. (Foreground: northern spicebush (Lindera benzoin) leaves.)

    Sam Sheline / CC BY 2.0

    Successional Tuliptree Forest (Rich Type)

    Although it may look like an intact natural community with its magnificently towering, straight tuliptrees, the Successional Tuliptree Forest (Rich Type) is a semi-natural community because it likely grew up in response to a human-induced disturbance. How do we know that? Tuliptree (also called tulip poplar or yellow poplar) doesn’t produce many seedlings in an established forest. Instead, this species germinates and grows best where disturbance has exposed the mineral soil and produced a large sunlit opening in the forest canopy.

    After a forest has been cleared, if tuliptree seeds are present in the seed bank or are blown in by the wind from nearby trees, they are quick to germinate. Tuliptree is often among the first trees to come back on moist soil, often shading out slower-germinating competitors for sunlight. An even-aged stand of pure tuliptree, therefore, is evidence of forest regrowth from some past major disturbance.

    At Rock Creek Park, the Successional Tuliptree Forest (Rich Type) grows in areas that may have been cleared and farmed long ago. Upwards of a century has passed since the soil disturbance that created most examples of this semi-natural forest and the regrown forest appears quite majestic in some areas today.

    This tuliptree-dominated community can be found occasionally throughout the park on somewhat moist, well-developed soils. The understory is often lush, containing northern spicebush and various herbaceous plants. In some sites, groundwater may supply extra base minerals. These forests tend to be heavily invaded by non-native plant species.

    As older tuliptrees in stands of the Successional Tuliptree Forest (Rich Type) die out, they might be replaced by American beech and oak trees. These replacement species can germinate on the shady forest floor, where they stand poised to take the place of tuliptrees in the forest canopy when given the sunlight and space to do so. However, since some tuliptrees have reportedly lived to be 300+ years old, it could be a long time before these stands of pure tuliptree give way to a mix of tree species, unless storms or other disturbances bring down mature trees.1

    Abbreviated Common Name: Successional Tuliptree Forest (Rich Type)
    Scientific Name: Liriodendron tulipifera / (Cercis canadensis) / (Lindera benzoin) Forest
    Scientific Name Translated: Tuliptree / (Eastern Redbud) / (Northern Spicebush) Forest
    Classification Code: CEGL007220

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    Base of a triple-trunked tuliptree
    Triple-trunked tuliptree ( Liriodendron tulipifera) — likely regrown from a stump.

    Erin Lunsford Jones, courtesy of NatureServe

    Successional Tuliptree – Oak Forest

    At Rock Creek Park, this community is characterized by the dominance of tuliptree with some similarly-aged oak including white oak and northern red oak in the canopy. Non-native invasive species are often dominant in the shrub layer and field layer. This forest commonly has a weedy appearance because it consists of relatively small trees growing close together, and contains an abundance of non-native species in the understory.

    The Successional Tuliptree – Oak Forest occurs in small patches throughout the park on land where the vegetation was heavily disturbed—perhaps logged—but the soil was not plowed.

    This community is distinguished from the Successional Tuliptree (Rich Type) by the presence of oak in the canopy, and by a low diversity of native shrubs and herbaceous plants. Northern spicebush is not common here. As this successional forest ages, its distinctiveness from the Mesic Mixed Hardwood Forest or other natural communities gradually disappears, except perhaps for its greater abundance of invasive species in the understory.

    Abbreviated Common Name: Successional Tuliptree – Oak Forest
    Scientific Name: Liriodendron tulipifera – Quercus spp. Forest
    Scientific Name Translated: Tuliptree – Oak species Forest
    Classification Code: CEGL007221

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    Successional Virginia Pine Forest

    Virginia pine, like tuliptree, is an early successional tree, but exposed mineral soil is essential for its seedlings to get established, and it can tolerate drier conditions than tuliptree. Through the 1970s, pine trees were frequent components of upland forest communities in Rock Creek Park2, where they may have become established in areas cleared for agriculture or Civil War forts and sight-lines. Many have since died, but some can still be seen near the Rock Creek Golf Course and Horse Center. As the park’s forests age and mature, the Successional Virginia Pine Forest is fast disappearing. When a pine tree dies in the interior of a forest, oak or American beech usually replaces it in the forest canopy.

    Currently, Virginia pine trees are more often encountered as part of the Coastal Plain Oak Forest in the Fort Circle Parks, or as individual remnants within other natural communities such as the Mixed Oak / Heath Forest between Bingham Drive and Wise Road in the northern portion of the park core.

    Abbreviated Common Name: Successional Virginia Pine Forest
    Scientific Name: Pinus virginiana Successional Forest
    Scientific Name Translated: Virginia Pine Successional Forest
    Classification Code: CEGL002591

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    Successional Mixed Deciduous Forest

    Successional Mixed Deciduous Forests in Rock Creek Park are of variable composition and age. Most of these stands are a mix of native and non-native sun-loving, fast-growing “weedy” tree species that colonize disturbed ground. Typical native species include black locust trees, tuliptree, elms, box-elder, and poison ivy, and native cherry species. Non-native species include Norway maple, honeysuckle shrubs, multiflora rose shrubs, English ivy, and non-native cherry species.

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    Successional Vine-Shrubland

    The Successional Vine-Shrubland is dominated by non-native invasive vines and shrubs. Live native trees may be present but they may be sparse and choked by vines.

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    Planted Evergreen Forest

    Planted Evergreen Forests are areas at Rock Creek Park where evergreen trees appear to have been planted in the past. Evidence of planting may be more or less obscured in today’s landscape depending on the length of time since planting occurred, and how long ago the stand was last thinned of other kinds of trees and shrubs.

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    Historic Quarry

    The so-called Historic Quarry semi-natural community at Rock Creek Park is dominated by hardy and fast-growing non-native invasive trees, vines, shrubs, and small plants. Not too many native plants can be found growing in these areas that were formerly disturbed by quarrying.

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    Not-So-Natural Communities

    Lawns, golf courses, and maintained meadows are neither natural communities nor semi-natural communities. We'll call them not-so-natural communities. Sometimes called “cultural vegetation,” these areas are managed and maintained by human intervention. Rock Creek Park has several types of these non-natural vegetation communities.

    Maintained Meadows

    The National Park Service maintains about a dozen or more small areas as meadows for wildlife diversity. Many creatures, such as field mice and their predators, butterflies, pollinator insects, and grassland birds benefit from openings such as these. These open areas are maintained by occasional mowing. In the past, it’s possible that fires caused by lightning and Native Americans may have created infrequent prairie-like openings in what is now Rock Creek Park.

    Picnic area along Rock Creek in spring.
    Rock Creek picnic area in the Rock Creek floodplain.

    Erin Lunsford Jones, courtesy of NatureServe

    Picnic Areas

    Rock Creek Park has several picnic areas near the creek. While the trees remain typical of floodplain communities, the understory is maintained as lawn by regular mowing.

    Golf Course and Other Landscaped Areas

    Another category of not-so-natural communities is landscaped areas, such as the Rock Creek Golf Course and any other regularly mowed areas, and plantings around buildings.

    Stormwater Retention Ponds

    Wetland swales dominated by cattails were created to slow down and filter urban runoff before it enters streams. These human-made wetlands occur northeast of the core park, in the Fort Circle Parks area.

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    Ecological Systems

    Natural communities don’t exist in isolation, but rather occur in a larger context, called ecological systems. Ecological systems consist of groups of natural communities that tend to occur together and that share certain natural processes, such as flooding or fire. Rock Creek Park’s natural communities belong to four ecological systems.

    Ecological systems, with their natural processes, provide a helpful context in which to understand natural communities and help predict what types of plants and animals might thrive there: You wouldn’t expect to find a water-loving, flood-adapted natural community on a dry ridgetop, nor would you expect to find a fire-adapted natural community along the banks of a river.

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    1. Fleming GP. 2007. Personal Communication re: vegetation communities at Rock Creek Park. Vegetation Ecologist.
    2. Anderson RR, Mcfaden DM, Kramer RJ, Dee JC, Jones GC. 1977. Rock Creek Park and Rock Creek and Potomac Parkway: vegetation community structure and automated classification of vegetation communities. 1

    Part of a series of articles titled Rock Creek Park Ecology.

    Rock Creek Park

    Last updated: July 26, 2024