Culm Diameter Comparisons of Yellow- groove Bamboo (Phyllostachys aureosulcata) in Glover-Archbold Park, Washington, D.C.

Two stands of the alien invasive bamboo species, preliminarily identified as Phyllostachys aureosulcata, (Yellow-groove Bamboo) reside in Glover-Archbold Park (GAP), a quasi-natural forest in Washington, D.C. I tested the null hypothesis that culm diameter does not differ between two stands (North and South Groves). A culms emerges from the ground with the diameter that it will have as a mature shoot, and culm diameter is an indicator of the health and vigor of a bamboo stand. The mean culm diameter in the South Grove was larger than the mean diameter in the North Grove. In addition, this study explores some of the factors that may correlate with the difference in size found between the two stands.

There are over 1200 bamboo species (Poaceae: Bambusoideae) in the world (Lewis Bamboo Groves, Inc. 2003). Bamboo species vary in height from dwarf, one-foot plants through giant timber plants that can grow to over 100 feet tall. One can use general growth characteristics to classify bamboos. Some bamboos are runners, which spread exuberantly and are capable of overrunning their surrounding habitat within a growing season (Lucas 2003). Others species, classified as clumpers, tend to expand more slowly from their original plantings. Temperate bamboos are often runners.

Glover-Archbold Park, located directly adjacent to the western boundary of Georgetown University Main and Medical Campuses, and hosts thousands of organism species, both native and alien. At the southern-most entrance to the GAP, one of the alien invasive plant species dominates the western slope – putatively identified as Phyllostachys aureosulcata (Yellow-groove Bamboo) (South Grove). About 0.4 miles north of this stand, a second, smaller stand of this species resides to the left of the trail in the valley section of the Park (North Grove).

Yellow-groove Bamboo’s name derives its yellow sulcus on its green culm. The "culm" of a bamboo plant is its stalk or "trunk," if it is a tree-sized species. A "sulcus" is the groove, or depression, in the internode of a culm. This Bamboo grows up to about 30 feet. This species is distinguished by the zig-zag pattern occurring on the lower quarter of some of its culms. I used this distinguishing feature to identify Yellow-groove Bamboo in the GAP. Yellow-groove Bamboo is one of the cold-hardier bamboo species, capable of withstanding temperatures down to -15̊ F. I visited the two Groves in mid-December when temperatures dropped below freezing and snow covered the ground. The bamboo stands appeared unaffected by the cold. This species prefers well-drained soils high in organic matter.

The Yellow-groove Bamboo is a mid-sized plant and considered extremely sturdy for planting purposes by the American Bamboo Society (Abrahamsen 2003). Its culms reach their maximum height in their first growing seasons and then, each year after that, usually add branches until achieving maturity in 5 through 7 yr . Yellow-groove Bamboo originated in China, came to the United States sometime in the 19^th century and is now found across the country. According to the U.S. Department of Agriculture, the Yellow-groove Bamboo grows primarily in the Mid-Atlantic Region and the southern states of Virginia, West Virginia, Kentucky, Tennessee, and South Carolina.

My study records the diameters of culms from the two stands of Yellow-groove Bamboo and attempts to determine if a significant difference exists in the relative vigor of the two stands based on culm size. As stated in McClure (1966), "The rate of development of the clump depends very largely, even in the same species, on the conditions under which it has been grown." I hypothesized that I would find bigger, healthier bamboo culms in the South Grove, which grows at an edge of the GAP. This grove gets more direct sun than the North Grove. This fact is important when one considers that the Yellow-groove Bamboo is a sun-loving plant. Finally, the majority of the South Grove is located on a hillside where moisture drains much more readily than in the flat area where the North Grove grows. It is in a central part of the GAP where it competes with many nearby trees.

Using the American Bamboo Society’s Website (Abrahamsen 2003), I putatively identified GAP’s bamboo species as P. aureosulcata by the yellow grooves present on its culms and the zig-zag pattern at the base of some of its culms. I collected information about the two bamboo stands during multiple outings in late October and early November. I chose 20 culms nonrandomly from each stand, trying to obtain a representative sample. Diameter measurements were taken with tape measure at breast height (d.b.h. = 4.5 feet off the ground). I straightened the culms of leaning plants to the best of my ability to measure them at breast height. Finally, I tabulated culm diameters from the two Groves. The Laboratory of Entomology and Biodiversity used SPSS 12.0 to perform a t-test on culm diameters.

The diameters of the randomly selected culms were 0.83 in ± 0.18 SD (range 0.56–1.18, N = 19) in the North Grove, and 1.81 in ± 0.31 SD (range 1.12–2.30, N = 19) in the South Grove (Table 1). The culms of the South Grove were statistically larger than those of the North Grove (two-tailed t-test, d.f. = 18, P < 0.001).

My data analysis supports my alternate hypothesis. Culm diameter differs between the two Groves. The South Grove, located on the fringe of the GAP, has much thicker culms than the North Grove, located in the interior of the park. As noted previously, culm diameter is one indicator of species health in that larger culms occur in more robust shoots. Thus, apparently the more favorable conditions found at the southern site are contributing to the superior vigor and size of the Yellow-groove Bamboo located there. The North Grove Yellow-groove Bamboo are evidently competing with the already well-established plant species found in the interior of the park. The North Grove grows in a shadier area and in moister ground than the South Grove. These factors may limit culm size.

As in all research, possibilities for error and bias exist. For example, I did not sample randomly and this might have introduced sampling biases. I did not sampling the culms of the innermost parts of the Grove because the culms were very dense. Consequently, my data set is from the peripheral area of the Groves. Additionally, on my second visit to the North Grove, snow had fallen and bent some of the culms with its weight. Consequently, my measurements were taken at an angle and may have been less accurate.

In conclusion, I found that culm diameter in the South Grove of Yellow-groove Bamboo was statistically larger than in the North Grove. I hypothesize that certain factors including sunlight, slope, and competition affect culm size. Future researchers have numerous opportunities to build upon my research. They should look at pH levels in the soil. Certain bamboo species tend to grow in soils of a very specific pH; perhaps the pH levels are more favorable towards the southern end of the GAP than in its interior for Yellow-groove Bamboo. An analysis of the plant species surrounding the Groves might determine whether there is a correlation between the size and health of the Bamboo and the presence of other plant species. Attaining concrete data for moisture levels in the soil could help researchers explore the effects of soil moisture on the Bamboo growth: the South Grove is mostly on a steep slope, whereas the North Grove resides at the base of the GAP, where soil moisture might be greater. Because temperate bamboos prefer dry, well-drained soils, perhaps poor drainage in the North Grove is a factor that reduced culm size. If further studies are to occur on the Yellow-groove Bamboo in the Glover-Archbold Park, they need to happen soon. The National Park Service (NPS) is eliminating this invasive species as part of its mission to return parks to as close to their natural states as possible. The NPS has removed much of the Bamboo in the South Grove in the last few years.

I would like to thank, first and foremost, Dr. E. M. Barrows for his guidance and patience in working with the only non-science major of the class. Speaking of the class, praise needs to be shared and spread amongst it – without tips and assistance, I would have been lost. Finally, I thank my roommate, Eric Pohlman, for lending me his tape measure.

Abrahamsen, Barry. 2003. Introduction to Bamboo. American Bamboo Society. Internet file. http://www.americanbamboo.org/GeneralInfo.html (10 December 2003)

Lucas, Susan. 2003. Growing, Using and Maintaining Temperate Bamboos. American Bamboo Society. Internet File. http://www.americanbamboo.org/GeneralInfoPages/LucasTemperateBambos.html (10 December 2003)

McClure, F.A. 1966. The Bamboos. Smithsonian Institution Press, Washington, D.C. 345 pp.