Research: The Ridgewood Reservoir
As seen through the eyes of a horticulturalist and naturalist, the Ridgewood Reservoir represents a unique opportunity to study the process of forest succession in an urban environment. Forest succession is the process whereby formerly wooded areas, which were cleared by man, attempt to return to their natural forest state. The process happens in stages with distinct plant communities representing each phase of succession. Early succession plants grow quickly and with vigor, as they lay the groundwork for future phases of succession. Building upon the changes made to the soil and the accumulated organic matter provided by the pioneer species, secondary succession begins to take place. These plant communities tend to have a longer lifespan and grow at a slower rate. At this stage many climax species have begun to take hold in the plant community. As time progresses, these climax species begin to dominate the landscape, ushering in the final phase of forest succession, the climax forest. This process can take hundreds if not thousands of years to run its course, and the Ridgewood Reservoir is still but an infant.
Drained in the early 1990’s, the reservoir’s three basins display the classic signs of an early succession forest. Red Maple (Acer rubrum), Grey Birch (Betula populifolia), Pin Oak (Quercus palustris), and Sweetgum (Liquidambar styraciflua) are among several early succession tree species found in the reservoir. Other genera include Willow (Salix sp.) and Poplar (Populus sp.) as well as an expanding group of perennial herbs and grasses. Woolgrass (Scirpus cyperinus) and Soft Rush (Juncus effusus) along with Showy and Licorice Goldenrods (Solidago speciosa, Solidago odora), Violets (Viola sp.), and Indian Hemp (Apocynum cannibinum) make up the herbaceous layer.
As the reservoir is located in an urban setting, there are unfortunately several invasive exotic species competing for space as well. The rim of the reservoir basins are dominated by Oriental Bittersweet (Celastrus orbicularis), Mugwort (Artemesia vulgaris), Poison Ivy (Toxicodendron radicans *), and Porcelain berry (Ampelopsis brevipeduncularis) among others. However, the interior of the basins have proven to be more difficult for invasives to gain a foothold. Only a handful of exotics have been able to compete down in the center of the basins. Those include Buckthorn, (Rhamnus frangula), Japanese Knotweed ( Polygonum cuspidatum), and the Common Reed (Phragmites australis) and a few others.
Whether the natives or the exotics will triumph in the end is hard to say. Much depends on how the space is managed as well as whether any secondary succession species can gain a foothold. Many early succession plants have a simple motto: “live fast and die young.” The presence of Red Oak (Quercus rubra) is an encouraging sign that the next phase of succession is slowly beginning. With plenty of time, good management and patience, the Ridgewood Reservoir could still achieve the magnificence and splendor of our native eastern forests.
*(Poison Ivy is native to the US but thrives in disturbed areas)
– Uli Lorimer
Curator of Native Flora Brooklyn Botanic Garden
Plant List (PDF)