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Scientific name: : : : :
Common Name: Information Sheet, Lawrence Kelleher

Country: USA
State/District: DC
County: not applicable
Date (D-M-Y): 1 - 12 - 2003

Photographer: E. M. Barrows

Identifier: E. M. Barrows
Collector: not applicable
Location: Washington, D.C., Area
Keywords: A FE2003R Forest Ecology
Additional Information:

Instructors' Note

A student in Forest Ecology (fall 2003) at Georgetown University (GU), Washington, D.C., produced this report as an individual class project which had a limit of about 25 hours.

Goals of the course projects included:

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

(2) learning about the scientific process while working on a hands-on field project.

(3) learning about answering scientific questions and testing hypotheses.

(4) 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.

The first emphasis was on working with the scientific process, and the second emphasis was on conclusively answering questions (or conclusively testing hypotheses) as the allotted time allowed.

To see all of the 2003 online projects, please use the keyword “FE2003R” on this Website.

Projects of future Forest Ecology students might continue lines of investigation of these and past projects.

E. M. Barrows and Kyle M. Brown, instructors

American Beech Root Exposure is Positively Corrected with Slope Erosion

Lawrence J. Kelleher
Georgetown University
Forest Ecology 355
Fall 2003


The aim of this study was to determine if there is a correlation between root exposure of American Beeches and the slope of the land on which the trees reside. Root exposure is an indication of erosion of soil from around tree bases. The study of 20 trees demonstrated that a correlation exists between these variables. For every 1° increase in slope, there is a 5.4 cm increase in the amount of root exposed.


The objective of my study is to determine if there is a relationship between root exposure of American Beeches, in Glover-Archbold Park (GAP), and the slope of the land on which they are located. The exposure of the roots indicates that erosion has taken place, and may be used as a measure of erosion. Due to the large amount of rainfall throughout 2003, I hypothesized that there is a significant amount of the root exposure, thereby indicating that erosion has taken place. However, I was not able to tell when the erosion had occurred, and the erosion could have occurred in previous years. Also, I hypothesize that the slope of the ground on which the tree is located is positively correlated with its down-slope root exposure.

Glover-Archbold Park is a "finger park" of Rock Creek Park (Barrows 2003). It is composed of one major stream, the Foundry Branch, and can be considered an urban forest. Neighborhoods and buildings surround GAP, yet it is still home to a variety of wildlife. One of the major tree species in the GAP is the American Beech.

In this investigation, I studied the American Beech because of its prominence in GAP. It is easily recognizable by its smooth gray branches and trunk. Its leaves are alternate, simple, and serrated. According to Barrows (2002), the versatile American Beech can live in a variety of habitats including closed forests, successional areas, and forest exteriors, and its habit differs with location. The American Beech plays several key roles in forests. Its hollow trunks provide shelter for different forest organisms. Also, American Beeches are food of organisms such as a moth species, a weevil species, and White-tailed Deer.

Erosion is the detachment of soil and sediments by hydrological (fluvial) processes and the action of the wind (U.S. Global Change Information Office 2003). Erosion can be very devastating to a habitat. It reduces the amount of nutrients that are available to plants and can reduce the diversity and abundance of soil organisms. Erosion can be used as a good indicator of the health of an ecosystem, and erosion estimates are significant to the issues of land and water management.

It is important to recognize that soil erosion can also occur through the actions of Humans. The building of communities around an ecosystem, such as GAP, is "human intervention." Humans probably increased the erosion in GAP when they felled its large trees during the Civil War, and we are still increasing its erosion by flooding Foundry Branch with precipitation runoff.

Materials and Methods

I collected data in both the northern and southern areas of GAP in October and November 2003. The southern area as the region of GAP that lies south of Reservoir Road, and the northern portion, north of this Road. I sampled the 20 trees non-randomly in these areas, 10 from each area. I chose American Beeches of different ages and sizes. I chose them non-randomly from various locations throughout GAP. The slopes on which sample trees grew varied greatly.

After the trees were selected, I measured the length of the longest exposed root in centimeters. Also I measured the slope of the land on which the tree was located. In order to do this, I used a level and two poles. The slope was calculated using geometry after two measurements were taken (the distance of root exposure for a tree’s base and the vertical distance from point of greatest root exposure to the baseline of a tree’s trunk). I used the level to determine the plane of the baseline to enable correct measurements. I considered the amount of root exposed to be an indication of the amount of erosion that has taken place; the longer the exposed root, the greater the amount of erosion.

Results and Discussion

Twenty trees had a mean of 114.2 cm (3.4 – 402.3 cm) root exposure (Table 1). The average slope on which trees grew was 26.1° (1.9 – 72.4°) .

Length of root exposure is positively correlated with slope of the ground (Figure 1). There is a slight increase in the amount of exposed root as the slope of the ground increases. Two of the datum points do not follow the general trend. These are the root exposures that occur at 14.3° and 34.6°. This variation may be due to the fact that these trees are located in an area where there is an above average amount of erosion that is taking place.

The slope of the best-fit regression line (Figure 1) indicates the increase in the amount of root exposure verses land angle. The slope of the line is approximately 5.43, indicating that there is a 5.43 cm increase in root exposure for every 1° increase in slope. There is a significant correlation between length of exposed roots and downward slope of the bank on which a tree is growing (linear regression, r2 = 0.883, P < 0.001). Twenty trees was an adequate sample to find the correlation.

A fault of this study is that the trees were not chosen in a randomly and the data may therefore be biased. In future studies, a random number table should be used so the study sites are picked in a randomly. This would help to ensure that the data are not skewed based on a particular factor in the area of the Park where most of the trees were studied. However, I did chose a sample of trees that are growing an a large range of slope angles.

This study will make it possible to perform future studies that can compare the amount of erosion that takes place from year to year. It is possible that the data used in this experiment can be used as a basis to see if further erosion is taking place. Also, it may be important to try to correlate the health of a tree to the amount of erosion that has taken place. The study would be much more relevant if it were conducted throughout the entirety of GAP rather than in just small sections of northern and southern GAP.

Due to time restrictions, I was unable to determine if there was a correlation between the amount of exposed root of a tree and how long it stands before it falls due to erosion. It is important for future studies to observe this so as to inform National Park Service (NPS) about erosion and tree falls.


I thank Dr. E. M. Barrows for supplying me with the necessary equipment and guidance throughout the course of this investigation. I would also like to thank Matthew J. Fanelli, my research partner, for venturing into the woods with me and aiding me with my more difficult measurements.

Literature Cited

Barrows, E. M. 2002. Information Sheet, American Beech. Internet file. (15 December 2003)

Barrows, E. M. 2003. Information Sheet, Glover-Archbold Park, Washington, D.C. Internet file. (15 December 2003)

U.S. Global Change Information Office. 2003. Soil and sediment erosion. Internet file. (15 December 2003)

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