Amur Honeysuckle (Lonicera maackii ) has been invading the Oxford area, as well as the rest of Southwest Ohio, since it was introduced to the area in the nineteen-sixties. L. maackii has invasive tendencies in this environment, and often competes with native plants of the area for natural life sources. L. maackiís aggressive, invasive behavior results in its domination of many forests and the killing of many of local plants. Once our research group had decided to focus our research on the invasive shrub, L. maackii, we began to develop ideas for how we would conduct the actual research. Since our research group knew that L. maackii was invading the forests, we decided on an experiment that would test the distribution of Lonicera maackii in the outskirts our local Western Woods.
The distribution of L. maackii in and around forests is significant in determining the extent of its invasive properties. Since L. maackii has only been recently introduced into the Southwestern Ohio region, many of the indigenous plants of the area do not have a defense against it. It competes with other plants in the forest, causing many of them to be starved for nutrition and space.
Included in our research groupís background information are summaries of the many experiments that have previously been conducted concerning how L. maackii affects its environment, and the effects of the environment upon L. maackii. Our experiment and research seeks to measure the amount of L. maackii that occurs fifty meters into the Western Woods. This will help us determine the density of L. maackii, thus leading our research group to better understand the aggressive nature of this invasive plant.
II. Relevance of our Research Question
L. maackii is an Asian exotic shrub, which was introduced to the U.S. as an ornamental plant. However, it has since invaded and currently dominates many forests in the Eastern U.S. and Southwestern Ohio (Hutchinson et al., p. 1118). It was recently introduced to Oxford, Ohio in the 1960ís and has repeated its invasion here as well (Hutchinson et al., p. 1119). Since the encroachment of L. maackii, numerous studies have been conducted with the purpose of determining the factors that may contribute to its invasibility. This incursion of the L. maacki is worrisome since it tends to suffocate the native plants by reducing the light, nutrients, and moisture that reaches them. In large quantities, it also has negative affects on tree seedlings and herbs.
The research of others has greatly enhanced the research conducted by our own group. By reading the studies that scientists had previously completed, we became more aware of the different factors that may play a role in our own research and became further informed of the effects and significance of L. maackii. The extensive research conducted by Andrew Gould explained the effects of L. maackii upon native plants to the Southwestern Ohio region. Although the purpose of his research was not identical to ours, his research enriched our knowledge of L. maackii and different research methods. Our research group discussed the different methods that Gould used in order to develop our own more successfully. Dr. Charles E. Williams of Clarion University also conducted research on L. maackii. His findings informed our research group of the general nature of the invasive plant, including its extensive history and itís growth tendencies. We learned of its growth habitat in both foreign and native areas and learned of control techniques used by humans to regulate the spread of the shrub. By reading his research work, we gained a broader, more complete knowledge and background of L. maackii.
Our purpose for research relating to the distribution of L. maackii in the outskirts of Western Woods is to deliberately test an area where the plant is supposed to thrive. Several studies have been conducted on other treeís canopy cover and the effects of light on the abundance and health of the L. maackii. This species seems to thrive in an open environment, in opposition to more thickly forested areas (Luken, p. 264). In fact, it has been determined that as the canopy cover from other surrounding trees increase, the canopy of the L. maackii tends to decrease (Hutchinson et al., p. 1120). However, as soon as the thick canopy is disrupted, the L. maackii is able to thrive. This observation exhibits that, as the amount of light in the forest increases, the health of the L. maackii improves. (Luken et al., p. 1959). In fact, Luken et al. found in their research that the new leaves that are exposed to 100% light show increased thickness, higher stomatal density, and increased carbon fixation ability than the new leaves exposed to less light (p. 1959). The studies that they have conducted also found that L. maackii seedlings that are grown in the shade grow very slowly and may even show negative growth patterns (p. 1960). After reading the reports on the studies conducted by other researchers, our group has decided to test the factors of thick canopy and light quantity by measuring the distribution of L. maackii in the outskirts of Western Woods. On the main path the canopy is thin and the light quantity is high. This will cause the distribution of L. maackii in the forest to be denser than anywhere else in the forest. As the light quantity decreases into the forest and as we measure distances further from the bright clearing of the path, our research group hypothesizes that the growth pattern of L. maackii will become less frequent in the interior of the woods than the outskirts of the woods. In our studies, we also plan to consider the other factors that may play a role in the abundance of L. maackii in the forest. If the research that was done before us is correct, the quantity of L. maackii should decrease as we get farther into the Western Woods.
III. Materials and Methods
In order to obtain data accurately for the purpose of determining the distribution of L. maackii in a forest, we must determine the area covered by L. maackii. We collected data starting at the main path of the Western Woods behind Boyd Hall. The other research groups collected the majority of the data for our experiment in our Natural Systems I class. Therefore, the data was determined and recorded by groups of size averaging five people. In order to determine the forest area covered by L. maackii, the transect method was used.
First, one member of the group held the loose end of the fifty meter tape measure at the edge of the path. Then a second member of the group walked with the reel end of the tape measure into the woods. This person tried to maintain the tape measure in a straight line as he/she moved into the woods. Once the fifty meters of the tape measure were laid down into the forest, the five members of the group reconvened at the edge of the path to measure and record the data (see data sheet). One data sheet was distributed to each group. The data sheet was used to record the information gathered from each of the different transects. There will be a different table used to record the data from each of the different transects. Each table consisted of two columns that allowed the students to document the covered and uncovered portions of the tape measure.
The method each group used for determining the amount of L. maackii along each transect was as follows. The measurements were calculated by recording exactly where the growths of L. maackii stopped and started along each transect. All shrubs below and above, including overhanging branches were included in this measurement. Each group repeated this process for their designated transects with each measured area being ten meters apart. This allowed our research group to collect data from twenty different transects, with ten transects located on each side of the main path of the Western Woods behind Boyd Hall. Each spot where the student research groups ran a transect was marked with a number attached to a branch along the woods, so that each group knew where to run the transect. Each group knew which areas they were to collect data for by the numbers marked on their data sheet. By conducting our research in this manner, we made the methods of data collection as identical as possible.
Upon receiving a complete set of numerical data from our research, our research group determined the meters covered by L. maackii for ten-meter segments for each transect. The numerical data that we attained was entered into Microsoft Excel, which allowed our research group to present our data in spreadsheet form. Through the use of the spreadsheet, we were able to find the absolute cover of L. maackii of each transect. After our research group calculated the absolute cover of each individual transect, we were able to calculate the mean of all of the different transects in ten-meter increments. Still using Microsoft Excel, we then were able to construct histograms of the mean coverage of L. maackii, as well as histograms exhibiting the individual distribution of the shrub along each separate transect by ten-meter increments.
After doing all that could be done in Microsoft Excel, we transferred the data that was entered into the spreadsheets into StatView, through which our research group was able to obtain statistical information regarding the data gathered.
While our research group gathered data in the Western Woods with the rest of the research groups, we immediately noticed upon our entrance that the densest population of L. maackii appeared around the edges of the forest. The collection of the data went smoothly due to the simplicity of the task, and the data that we received and processed is true to what the population exhibited in the Western Woods.
The results that we obtained through gathering the data is displayed through graphs and tables constructed by our research group. While constructing these graphs and tables, we carefully considered what means would be most appropriate in accurately portraying and representing our findings. A series of histograms and tables represent the data that we collected in the Western Woods regarding L. maackii.
(See attached sheets for graphs and tables.)
The results of the data that our research group obtained through gathering data regarding the growth density of L. maackii in the Western Woods helped prove our hypothesis to be true. The growth of L. maackii around the outskirts of the forest is, indeed, denser than the growth of the shrub farther into the woods. We can observe this through the statistical tables and histograms, which provide a visual interpretation and description of our research groupís findings.
In order to determine the results of the paired t-test, our research group combined all of the transects measured and divided the meters covered into intervals of ten meters. Every interval was then compared to the other ten-meter segments so that their relationships to one another could be easily determined. Upon examining the P-values for each comparison, our research group observed that there was a significant statistical difference between the first ten meters and the last ten meters of the transects compared. Our research group determined that when the 0-10 meter section of the transect was compared to the 40-50 meter section of the transect, the P-value was one of the lowest received. Through this, we were able to determine that there was a larger population of L. maackii present within the first ten-meter section than in the last ten-meter section. This proves our research groupís hypothesis to be correct.
Our research group chose not to pay as close attention to the P-values that were received through comparing intervals that are close to one another. We opted not to stress the importance of these statistics as much as those that we received through comparing those from further distances. This decision was made because the differences between them were not as statically significant as those who were located at further distances from each other. This could be observed by looking at the mean differences of each section when they are compared to another section relatively close to it. Since the mean values were low, the P-values were relatively high, and although statistically useful, they were not particularly significant in our study.
Through examining the P-values received from the paired t-test, it is evident that the P-value received from comparing the ten-meter interval to the fifty-meter interval is not the lowest. This irregularity in the data is explained in the paragraph below.
Histogram #1 exhibits the mean cover of L. maackii in the Western Woods. By examining this histogram, it is evident that there is a higher coverage of L. maackii within the first ten-meter increment than any of the following increments. The coverage of L. maackii decreases steadily through the following 30-meter increments, however, the final ten-meter increment displays a rise in the coverage of L.maackii. This rise could be descriptive of several determining factors, and this irregularity also explains the fluctuation of P-values in the paired t-test. The Western Woods is a forest that is interwoven with many separate footpaths. A path that cuts through the area that we were measuring could account for a disruption of the naturally thick coverage of the innards of the forest. Since the Western Woods is dense and populated by thick shrubs, as well as both standing and fallen trees, it was often difficult for the gatherers of the data to create straight transects through the designated plots of woods. This accounts for human error, and may have resulted in more than one area being less than fifty meters deep into the woods, as well as the possibility that some areas of those transects were measured more than once, due to these crooked transects. Lastly, since we were deprived of ample supplies, only one of the tape measures used in creating transects in the woods was an actual fifty-meter measuring tape. The other two measuring tapes were twenty and thirty meters in length. This may have caused difficulty in measuring exactly fifty meters into the woods, for research groups with these measuring tapes had to stop, measure the L. maackii coverage, then repeat the process on the same transect two or three times.
Histogram #2 through histogram #6 exhibit breakdowns of every individual transect measured in ten-meter increments. Overall, these histograms display the steady decrease in L.maackii coverage. There are few inconsistencies in the overall trends apparent in these histograms. This plausibly is due to the reasons discussed in the paragraph above.
Our research group has become aware of and discussed the many factors that we were not able to test at the time of our research that might have affected the growth of L. maackii shrubs within and along the Western Woods. We would suggest to anyone continuing research regarding L. maackii to incorporate the following considerations into their experiments. It is important to take into consideration the surrounding area of a forest when measuring for L. maackii coverage.
If the woods were next to a manicured field, the field may affect the growth of the forest, especially around its outskirts. This is especially likely if the field is treated with fertilizers, insecticides, or other which may harm or encourage the growth of L. maackii. The presence of a field also indicates the absence of canopy cover, which would ordinarily block direct sunlight. Therefore, the edge of the forest would be exposed to direct sunlight, encouraging the growth of L. maackii. Likewise, an adjacent parking lot would lack a canopy cover to block direct sunlight, and L. maackii would thrive at the edge of a forest in this situation. However, if on a downhill slope from the parking lot, the forest could be exposed to wastes draining from the area, which may affect the growth and health of L. maackii.
In our situation, the Western Woods is located on a downhill slope, which may result in the runoff of water and nutrients from the areas above it. It is possible that the amount of water at the edge of the forest might contribute to or inhibit the growth of L. maackii. Other factors which affect the growth of L. maackii may include the direction which Western Woods faces, the length of time it receives direct sunlight, and the age and development of the forest, since older forests have larger trees which block out more sunlight. These are important factors to consider when conducting research, since L. maackiiís growth and propagation increases with the abundance of direct sunlight.
Our research group has utilized various studies by other scientists on L. maackii to formulate a hypothesis for its distribution in our local Western Woods, that the growth pattern of L. maackii would become less frequent in the interior of the woods than that in the outskirts of the woods. Using a transect method to collect data from the Western Woods, we were able to acquire data in support of our hypothesis. Our data analysis and graphs show that the growth of the L. maackii shrub does decrease as we measured further into the forest. As a result, our research group is able to conclude that our hypothesis was correct, where the growth pattern of the L. maackii becomes less frequent in the interior of the woods than in the outskirts of the woods.
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7. Williams, Dr. Charles E. (1998). Japanese Honeysuckle (Lonicera japonica
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