Rock Creek has two main plant groupings: deciduous forests and wetlands. Each grouping contains different types of plants and animals. Rock Creek Park is one of the world's great urban forests, and forests are found throughout the Rock Creek Watershed. Wetlands are located primarily in the upper watershed. When you're out and about in the natural areas along Rock Creek, see if you can identify these plant groupings and read on to find out about their importance.
A deciduous forest is one in which most of the trees lose their leaves every year. The dominant tree species vary by elevation and the surrounding terrain. In Rock Creek's more mature upland areas or slopes, the dominant tree species are oaks (pictured below) and hickories. In lowland areas the dominant tree species are tulip populars, red maples, and sycamores. Other species that might include the green ash, black walnut, holly, black gum, and beech.
Deciduous forests also contain woody understory vegetation including dogwoods, ironwood, mountain laurel, spicebush (pictured below), and blueberries.
A wetland is land where the ground is saturated with water long enough to support vegetation that thrives in wet conditions. Wetlands support a wide variety of plants and animals, so wetlands tend to contain a higher number of rare, threatened, and endangered species. Wetlands account for approximately five percent of the total area of the upper Rock Creek watershed. Some plants associated with wetlands include black willow, smooth alder, buttonbush, swamp white oak, skunk cabbage, arrowhand, and cardinal flower (pictured below).
Cardinal flower (Image Copyright Information)
Importance of Plants
Plants such as these are more than just pretty things to look at. Trees and plants help make Washington and the surrounding suburbs cooler and play a major role in helping maintain our air and water quality. Rock Creek Park is the largest unbroken forest habitat within the District and provides habitat and food for much of the our widlife. It's important for forests to be large enough to provide a variety of animal habitats, contain a variety of tree and other plant species (including some rare and/or mature species)), and to have a variety of forest layers (tree canopy, undestory trees, shrubs, and smaller plants).
Wetlands serve a a variety of functions, including animal habitat and breeding ground, habitat for rare plants, maintenance and improvement of water quality, and greenhouse gas storage.
Non-native invasive plants are a big problem in the natural areas along Rock Creek. There are dozens of plant species that do not grow here naturally, but were brought to the area by people as ornamental plantings or for food. Some of these plants grow too well and are now taking over our parklands. They outcompete native plants for light, nutrients, water, and soil. They displace whole plant communities by smothering existing plants, increasing ground-level humidity, and changing soil chemistry and microorganisms.
The loss of native plant communities cause widespread damage. Invasive vines are covering, choking, and killing trees in many areas of parkland. Now whenever a large tree falls, invasive species move in to fill the void. Birds, wildife, insects, and other living things are adapted to specific plant communities. When plants are lost, the food, nesting sites, and habitats they provide are lost, with resulting damge to the animals that depend on them. Native plants also support the quality and functions of our wetlands and streams, as well as the natural beauty of our parks.
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