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Title: Information Sheet, Foundry Branch, Stream Bed Plants, and Glover-Archbold Park, Washington, D.C.




Instructors’ Note

A student in Forest Ecology (fall 2002) at Georgetown University (GU), Washington, D.C., produced this report as an individual class project which had a limit of about 20 hours.   Goals of the projects included:

(1) learning about a relatively natural forest (Glover-Archbold Park which is adjacent to Georgetown University), the “open urban forest” of GU Campuses, and the “urban forest” in residential neighborhoods near GU.

(2) providing information about these subjects to interested parties via the Internet.

These are short projects that lay groundwork for further investigation in their respective areas.   Therefore, these are pilot projects.   To see all of the 2002 projects, please use the keyword FE2002R on this Website.   Projects of future Forest Ecology students might continue lines of investigation of the 2002 projects.

E. M. Barrows and N. Bakkour, instructors



Variation of Plant Species in the Stream Bed in Glover-Archbold Park, Washington D.C.


Michael Bernstein
Department of Biology
Georgetown University
Forest Ecology 355, Fall 2002

Abstract

In this investigation, I attempted to determine what plant species live in the stream bed in Glover-Archbold Park. To accomplish this task, I ran five random east-west transects across the stream and identified the plants within 1 m on each side of the transect. The abundances of each species were also recorded so the relative success rate of the plants could be deduced. Furthermore, I classified the species as invasive or native to determine the percentage of invasion in the streambed. My results show that invasive species are more successful than the natives, accounting for 77% of the species examined. Finally, I speculate as to the reasons why certain plant species were observed in certain transects and absent in others.

Introduction

Although it is easy to become fascinated and engulfed in the large tree specimens and extensive biodiversity contained in Glover-Archbold Park, one must not overlook the beauty and importance of the streambed or the species that inhabit it. In general, streambeds are channels through which natural streams of water runs or used to run. The stream in Glover-Archbold appears to fluctuate between the extremes, depending on the amount of precipitation it receives. During times of intense drought, no running water exists in the stream, and only a few spots hold standing water. On the other hand, after days of abundant rainfall, water runs throughout most of the stream. More frequently, though, the latter is observed. The amount of water flowing in the stream inevitably affects what types of plant species can occupy it at a given time; some may be adept at establishing strong roots in the streambed and survive strong water flow while others may be susceptible to these kinds of conditions and can be easily washed away. An additional factor that contributes to the amount of water flow is the width of the stream. The Glover-Archbold stream meanders for the entire length of the park, alternating between narrow and wide banks along the way. Narrow banks cause an increase in water velocity and may limit the types or number of plants that can survive, while wider banks slow the water flow, facilitating the survival of plants with weaker roots.

Another feature affecting plant diversity in the streambed is the presence of invasive, as opposed to native, species. Invasive species threaten the integrity of forests and frequently prevail over native plants in obtaining necessary resources. Native species are often rendered defenseless while the invaders thrive in their new environment. They often crowd out native herbaceous species, reduce light levels to the forest floor, limit regeneration, or simply displace native shrubs and saplings. In a nearby park, Rock Creek Park, more than one-third (36%) of the 656 documented plant species are exotic, and of these, 41 are considered aggressive invaders (Salmons 1998). It is reasonable to assume that a similar invasion is occurring in Glover-Archbold Park.

In the following investigation, the aim was to determine and classify the plant species living in the streambed of Glover-Archbold Park. I discovered the types of plant species that inhabit the streambed as well as their relative abundances. Once all of the species were recorded, I identified those that were invasive or native to establish the amount of invasion that the park has experienced and the success rate of each. Lastly, an examination of all of the data was required so as to conclude which species appeared to be the most successful of those observed and the factors that determine whether or not a certain species lived in a particular location in the stream.

Materials and Methods

I ran five random east-west transects across the stream and took a census of the plants within 1 m on each side of the five transects as well as recorded the species abundances. I chose variable locations for the transects, one with dense vegetation, others with sparse vegetation, and one with little plant life. The plants were than classified as either invasive or native. Finally, the results were tabulated and organized into the subsequent table.

Results and Discussion Although there were clearly dominant plant species present at nearly every plot, the investigation proved that the variation exists in the streambed. In the examination, 17 species were identified and a total of 131 plants were recorded. Of these 131, 101 were categorized as alien, leaving only 30 as native (Table 1). According to these numbers, invasive species represent 77% of the plants observed, which is a significant increase from the 36% invasion documented in Rock Creek Park. Thus, the streambed appears to present an environment in which alien plants can flourish and out-compete native species for vital resources.

This investigation also revealed that the survival of the plants may be dependent on the width of the stream banks. At plot 2 where the banks were close together, I saw no vegetation. Although there was no water running during the days of observation, I can speculate that the narrow banks cause an increase water velocity, which forcefully washes away any plant life living in the area. On the contrary, when the bank widened, dense greenery appeared, though the Asiatic Waterpepper was undoubtedly the most prominent (Table 1). As I continued down the stream toward plot 4, I noticed scattered vegetation with much diversity. The wide banks at this location appeared to aid the existence of some woody plants that were not observed at other transects. Although large woody plants were conspicuously absent, the light water flow allowed for the survival of woody seedlings, such as Red Maple and Eastern Sycamore. At the fifth plot, which contained an area of standing water, it seemed that mostly vines were able to survive, while the running stream must have uprooted any tree seedlings.

In conclusion, I learned that the streambed in Glover-Archbold Park has considerable variability for with only five plots, 17 different plant species were classified. Furthermore, I concluded that invasive plants appeared to be most successful, representing more than three-quarters of the species identified. And lastly, analyses of the transects showed that survival of certain plant species seemed dependent on the width of the banks and the amount of potential water flow.

Acknowledgments

I would like to thank Dr. Edd Barrows for granting me the opportunity to experience and enjoy fieldwork and assisting me with any hurdles that I encountered. I would also like to thank Kellie Rooney for spending many hours with me in Glover-Archbold Park so that I could complete my project. Lastly, thank you to my parents and my sister for supporting me in all my endeavors and giving me all the encouragement in the world.

Literature Cited

Salmons, S. 2000. Rock Creek Park Invasive Non-Native Plant Mitigation Program Final Report. Internet file. http://www.nps.gov/rocr/natural/final.htm






Table 1. The plant species in the five transects in the Foundry Branch (= streambed of Glover-Archbold Park) listed in order of their abundance within transect.
Transect 1. Intermediate Vegetation
Taxon (genus, species, etc) Common Name Family Division Habit Invasive or Native Number of Individuals
Polygonum cespitosum Asiatic Waterpepper Polygonaceae Anthophyta Forb Invasive 14
Ulmus americana American Elm Ulmaceae Anthophyta Tree Native 3
Morus alba White Mulberry Moraceae Anthophyta Tree Invasive 2
Geum Avens Rosaceae Anthophyta Forb Native 1
Oxalis europea European Yellow Wood Sorrel Oxalidaceae Anthophyta Forb Native 1
Ampelopsis brevipedunculata Porcelainberry Vitaceae Anthophyta Woody vine Invasive 1
Fraxinus americana White Ash Oleaceae Anthophyta Tree Native 1
Lindera benzoin Spicebush Lauraceae Anthophyta Tree Native 1
Transect 2. No Vegetation
Transect 3. Dense Vegetation
Polygonum cespitosum Asiatic Waterpepper Polygonaceae Anthophyta Forb Invasive 63
Liriodendron tulipifera Tulip-tree Magnoliaceae Anthophyta Tree Native 7
Ampelopsis brevipedunculata Porcelainberry Vitaceae Anthophyta Woody vine Invasive 2
Rhus radicans Poison Ivy Anacardiaceae Anthophyta Shrub, woody vine Native 1
Morus alba White Mulberry Moraceae Anthophyta Tree Invasive 1
Transect 4. Scattered Vegetation
Polygonum cespitosum Asiatic Waterpepper Polygonaceae Anthophyta Forb Invasive 7
Rhus radicans Poison Ivy Anacardiaceae Anthophyta Shrub, woody vine Native 2
Ailanthus altissima Tree-of-heaven Simaroubaceae Anthophyta Tree Invasive 2
Ampelopsis brevipedunculata Porcelainberry Vitaceae Anthophyta Woody vine Invasive 1
Platanus occidentalis Eastern Sycamore Platanaceae Anthophyta Tree Native 1
Poales (order) Grasses, Sedges, Rushes 3 Families Anthophyta Poads Native 1
Prunus serotina Wild Black Cherry Rosaceae Anthophyta Tree Native 1
Fraxinus americana White Ash Oleaceae Anthophtya Tree Native 1
Acer rubrum Red Maple Aceraceae Anthophyta Tree Native 1
Transect 5. Standing Water
Rhus radicans Poison Ivy Anacardiaceae Anthophyta Shrub, woody vine Native 8
Polygonum cespitosum Asiatic Waterpepper Polygonaceae Anthophyta Forb Invasive 4
Hedera helix English Ivy Araliaceae Anthophyta Woody vine Invasive 3
Albizia julibrissin Mimosa Fabaceae Anthophyta Tree Invasive 1






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