Vine Growth on Ash-leaved Maples and Trees-of-heaven along the Capital Crescent Trail, Washington, D.C.

Abstract

The purpose of this study is to test the hypotheses that Ash-leaved Maples and Trees-of-heaven on the Capital Crescent Trail in Washington, D.C., host a different number of vine species and have different percent coverages by vines. After examining 100 specimens of each tree species, my observations indicate that though almost the same vine species can be found on each tree, Ash-leaved Maples generally have a greater number of vine species per tree. Ash-leaved Maples were also had a greater coverage by vines. Finally, it seems that not all vines were present to the same amount, but that English Ivy was most common on Ash-leaved Maples, and Asian Clematis was most common on Trees-of-heaven.

Introduction

In this study, I examined vine growth on Ash-leaved Maples (Acer negundo) and Trees-of-heaven (Ailanthus altissima) along the Capital Crescent Trail (CCT) in Washington, D.C. I tested the hypotheses that the trees were hosts to different species of vines and that they have different amounts of vine coverage, as well.

The Capital Crescent Trail is an 11-mile path that stretches from Lyttonsville, Maryland, in West Silver Spring, through Bethesda, Maryland to Georgetown, Washington, D.C. It is a popular recreation area for joggers, roller-bladers, bicyclists, and walkers and offers beautiful views of the Potomac River and the Rock Creek Stream Valley. Many trees, shrubs, and other organisms live and grow on each side of the paved trail (Phyillaier 2003).

Ash-leaved Maples and Trees-of-heaven are large autotrophs that are common in forests throughout the eastern United States. They are most often found in forests, forest edges, successional areas, and yards, and both are important in forest succession. Also, both provide food for many other kinds of organisms (Barrows 2002a).

Ash-leaved Maples and Trees-of-heaven can grow up to 70 feet tall and up to 4 feet in diameter (Athenic Systems 2003). Their large stature makes them prime hosts for vines, plants with woody or herbaceous stems that climb up or over other organisms or structures. Vines are unable to hold themselves upright and, therefore, depend upon trees, such as the Ash-leaved Maple or Tree-of-heaven, for support. Vines common on the CCT include Asian Bittersweet (Celastrus orbiculatus), Asian Clematis (Clematis terniflora), English Ivy (Hedera helix), Japanese Honeysuckle (Lonicera japonica), Japanese Wisteria (Wisteria floribunda), Kudzu Vine (Pueraria lobata), Poison Ivy (Rhus radicans), Porcelainberry (Ampelopsis brevipedunculata), and wild grape species.

Asian Bittersweet (AB) is an invasive, woody vine that lives in disturbed areas such as abandoned homes, fence rows, roadsides, and forest edges, usually in direct sunlight. It grows rapidly and covers other plant species, many of them native, and harms them by weighing them down, blocking sunlight, and reducing nutrients in the surrounding soil (Ohio Department of Natural Resources).

Asian Clematis (AC) is an invasive vine found throughout the eastern and central United States. It can grow from 20 through 30 feet long and is used widely as an ornamental vine in yards. However, it requires a large area to grow and often grows over native species, blocking sunlight to the underlying plants (The Plant Database 2000).

English Ivy (EI) is a woody, evergreen vine that can grow up to 150 feet long. It is a noxious, alien species that grows thickly on trees and other structures. It can kill trees by blocking them from the sun or felling them with its heavy weight (Barrows 2002b).

Japanese Honeysuckle (JH) is a woody, semi-evergreen, invasive vine that can grow up to more than 30 feet long. It is found primarily in disturbed areas, such as yards, fence rows, roadsides, forest edges and abandoned fields in the eastern and central United States. It kills native plant species by forming thick canopies on them and reducing light availability (Virginia Native Plant Society 1995).

Japanese Wisteria (JW) is a deciduous, invasive vine from Asia that is common throughout the eastern United States, although it is most abundant in southern U.S. It is generally an ornamental vine used on walls, balconies, and trellises, but it also grows over trees and other plants. It may kill other plant species and is very poisonous to Humans (International Programme on Chemical Safety 2003).

Kudzu Vine (KV) is an alien, invasive vine from Japan that is common from Connecticut through northern Florida and as far west as Texas. It is a woody, perennial vine that can grow up to 200 feet long and forms thick blankets over other plants, often killing them in competition for sunlight (Barrows 2002c).

Poison Ivy (PI) is a woody vine that grows in many forms, as a thick woody vine, a thin vine, or a vine-like bush. It may grow on other plants and compete for sunlight, but does not form thick mats that kill its host plants. It grows in forests, forest edges, successional areas, yards, and fields and provides food for many organisms, though it causes a painful dermatitis in many people (Barrows 2002d).

Porcelainberry (PB) is an alien, invasive woody vine that forms thick blankets on other plants and compete for sunlight and kills covered plants. It provides nectar and other food to many different organisms (Barrows 2001).

There are several species of wild grape, which are in the family Vitaceae. They can be found throughout the United States, most often by streambanks, sandy soils, dry woods, or thickets. Wild grapes are native to North America and may kill other plant species by forming thick blankets of vines over them (Rodenhouse 1998).

Materials and Methods

I collected data in the Georgetown section of the CCT in October 2003. I walked approximately 2 mi, observing trees on the bank side, along the Potomac River, and on the opposite side of the Trail. In a nonrandom manner, I selected the first 100 Ash-leaved Maples and the first 100 Trees-of-heaven within 10 ft of the path for study. For each tree, I recorded a number I assigned to each, the location (opposite or bank), diameter at breast height (d.b.h.), vine species present, and percent coverage of vines, estimating coverage to the best of my ability. I measured the d.b.h. with a tape measure and identified any vine species unknown to me with the help of Professor Edward Barrows, a professor of biology at Georgetown University.

To eliminate biases, I used a random-number table to randomly choose 50 Ash-leaved Maples and 50 Trees-of-heaven to study for this project. After tabulating my data (Tables 1 and 2), I found means and performed Student’s t-tests to compare the number of vine species present on each type tree and percent coverage of vines. Finally, I graphically organized the vine species found on each tree species (Figure 1) and performed a Chi-Square test to determine if particular vine species had a preference for Ash-leaved Maples or Trees-of-heaven.

Results and Discussion

I found nine different vines on Ash-leaved Maples on the CCT, including AB, AC, EI, JH, JW, KZ, PB, PI, and WG (Table 3). Only seven trees out of 50 (14%) had no vines (Table 1).  Trees-of-heaven had all the same vines as Ash-leaved Maples, with the exception of KZ and JW. Also, 15 of 50 trees (30%) did not have vines (Table 2). These percentages suggest that vines may have a slight preference for Ash-leaved Maples.  However, this preference may be explained by the size of the trees, as well. Ninety percent of Trees-of-heaven were small (d.b.h < 5.5 in) (Table 2), while only 26% of Ash-leaved Maples were considered small (Table 1).  This suggests a positive correlation between tree size and vine presence. 

Ash-leaved Maples had 1.40 ± 0.88 SD (range 0–4, N = 50) vine species per tree, while Trees-of-heaven had 0.980 ± 0.09 SD (range 0–3, N = 50) vine species per tree. There is a significant difference in the means of the two species (t = 2.4, d.f. = 98, P < 0.05), suggesting that while most vine species are the same, Ash-leaved Maples generally have more vine species per tree. There was also a significant difference between coverages of vines in the two species (t = 2.58, d.f. = 98, P < 0.05). Ash-leaved Maples had a mean coverage code of 2.94 ± 1.13 SD (range 1–4, N = 50), and Trees-of-heaven, a value of 2.34 ± 1.19 SD (range 1–4, N = 50); thus, it seems Ash-leaved Maples are also covered to a greater degree than Trees-of-heaven.

The vines were not present to an equal degree in each tree species.  There was a significant difference in the vines on the Ash-leaved Maples (X² = 199, d.f. = 7, P < 0.05). Seventy-two percent of trees observed had English Ivy growing on them, while only 2% had Kudzu or Japanese Wisteria.  This indicates that Ash-leaved Maples are more likely to be host to English Ivy than other vines on the CCT. Only 4% of Trees-of-heaven, on the other hand, had English Ivy growing on them.  Therefore, English Ivy seems more likely to grow on Ash-leaved Maples than Trees-of-heaven. There is also a significant difference between vines on Trees-of-heaven (X² = 74, d.f. = 6, P < 0.05). Thirty-eight percent were host to Asian Clematis, 30% had no vines, and none of the Trees-of-heaven were host to Japanese Wisteria or Kudzu. These results indicate that Trees-of-heaven are more likely to be host to Asian Clematis than other vines, and they are more likely to have this vine than Ash-leaved Maples, of which only 10% had Asian Clematis.

There are several biases in this project. First, I did not choose the trees completely randomly. I studied only trees on the Georgetown end of the CCT, which may have unusual features affecting vine growth. My using randomly assigned transects of the trail would have allowed me to get a better idea of the most common vines that associate with Ash-leaved Maples and Trees-of-heaven. Also, I studied trees of all different sizes, with Trees-of-heaven generally being smaller than Ash-leaved Maples. This difference in size between the two trees may have affected the types, number, and sizes of vines growing on the species. Finally, I approximated at percent coverage of vines on each tree, which may have caused many errors in my data.

In conclusion, it appears that Ash-leaved Maples and Trees-of-heaven on the CCT do not have equal amounts of vines species present or equal coverage by vines. Ash-leaved Maples seem to have more vine species and coverage. In order to better understand the relationship between trees and vines, future studies should examine the health of trees with and without vines and also possibly remove vines from trees already covered. Other studies may also include examining other tree species and studying other parts of the forest.

Acknowledgements

I thank Professor Edward Barrows (Department of Biology, Georgetown University) for assisting me with this project and for making the time to visit my site to help me identify vines. I also thank Daniel S. Kjar for helping to format my report and put it online. Finally, I thank Megan E. Brooks for her patience as we collected our data on the Capital Crescent Trail.

Literature Cited