Honeysuckle Friend or Foe

This topic submitted by Ryan Geismar, Josie Leimbach, Kerilyn Fields, Michael Hemme (hemmemd@miamioh.edu) at 1:45 am on 12/9/00. Additions were last made on Wednesday, May 7, 2014. Section: Myers

Introduction
We plan to research honeysuckle as an invasive species. There are several aspects we will observe. First, we will determine where in a forest honeysuckle prefers to grow. For example, does it grow on the outer edge or deeper within the forest? Second, we will observe the effects a creek has on the growth of honeysuckle. Does the creek act as a barrier and prevent it from spreading, or does it act as a corridor by allowing light through, thus helping it to grow? We will observe where honeysuckle grows along a creek - on one side or collected at a bend. Finally, does honeysuckle smother native plants? Does it block light from smaller plants and shrubs?
We want to measure how far into the forest honeysuckle grows, if there is a noticeable growth difference in interior samples, the health of honeysuckle growing in the interior, effects of land slope on the growth of honeysuckle, direction of slope, age of tree, and size of tree. We hypothesize that spread of honeysuckle is affected directly by:
Sunlight – Shown by the canopy cover and length of time the leaves spend on the branches. The more sunlight the more likely there will be a larger, healthier abundance.
Slope of the land – Contributes to the spread of the plant and decreases canopy cover
The creek – Acts as another edge, by allowing more sunlight in and possibly providing more fertile soil for the plant.
Abundance of the plant – The greater the number of plants, the greater the number of seeds, the greater the possibility of survival. This trend will continue exponentially unless something restricts it.
Location in the forest- The closer to the edge the larger and more abundant the bushes will be.
We hope to find that it does not flourish in the center of the forest, without the presence of a creek, due to insufficient sunlight. We also expect sloped areas to be inhabited by more honeysuckle, even in the forest interior, because of gaps in the canopy allowing sunlight to penetrate. We want to determine the age of honeysuckle in proximity to the creek compared to the specimens on the edge of the forest. This will suggest where the spreading originated. We expect that it grew near the creek and eventually began inhabiting areas exposed to more sunlight, such as the forest's edge.
We decided on this study because it sparked interest and provided many possibilities for discovery. The questions were derived through research of honeysuckle and its invasive characteristics. We also discussed research options with the professor. Honeysuckle originated in Japan and is native to eastern Asia. It was introduced to cultivation in 1862 on Long Island and is now widely naturalized in the eastern and central United States. This project applies to our class focus because it relates to nature and honeysuckle's effects on other plant life.

Research
In the past, the research on Lonicera maackii, more commonly know as honeysuckle, has been based on the effect it has on the native plant life it interacts with, as well as how it is dispersed. In the interaction, it has been found that the honeysuckle often smothers the native species, in order to create more room for its own growth. "Where L. maackii becomes established in the understory of forests, it has a negative impact on tree seedlings and herbs" (Hutchinson). This negative impact is do to the height of the plants found in the area which allows them to steal the sunlight from native plants. While honeysuckle usually has a negative effect on the plant life around it, it positively effects the soil, "The Japanese honeysuckle, a brutal invader of woodlands that can limb up and smother large trees, also protects a steep band from erosion" (Pelczar). When dealing with the dispersal of the seeds in spreading the growth, it has been found that the most prevalently dispersed through birds. However, this method has limitations, "Large expanses of land apparently act as a barrier to the dispersal of this naturalized shrub" (Hutchinson). This is the main basis of our hypothesis; “What does stop honeysuckle?” We are working to show this theory is true in many different environments including our own. Also, forest which have had little disturbances, i.e. tree clearing, etc., are more difficult for the honeysuckle to invade. "L. maackii is absent/rare in old-growth forest stands" (Hutchinson). While it does have its limitations, honeysuckle is very adaptive, "Lonicera maackii seeds are dispersed in a non-dormant condition. The shrub can establish throughout a wide range of environments" (Luken, Goessling). Their adaptability, is a threat to the native species in the area, but this threat is compounded by their speed of growth. "Japanese honeysuckle, Lonicera maackii grow much faster in an environment rich in CO2 than their native counterparts" (Sasek). By learning the growth patterns of the honeysuckle, and their rate of growth, we hope to be able to predict the trends of growth, and therefore perhaps help lead to a solution to limit growth so that the native species have a chance.

Materials and Methods
Our observation of the invasive properties of honeysuckle requires the creation of experimental tests. To run these experiments we will need the following: tape measure, canopy-measuring device, and a saw. The tape measure will be used to measure off the area in which we choose to take our samples from, and also to measure the height and width of the honeysuckle bushes. The canopy-measuring device will do just that. We need it to measure how dense the canopy is in the areas where we are taking the samples. The saw is to cut the trunk so we can count and observe the rings.
For the experiment, we will measure off twenty strips of land, one meter wide by twenty-five meters long, from the forest edge to the interior. Also, half of the sample strips should be from the creek bank inward. These sample strips of land will be five meters apart. When walking these strips, we need to take note of the slope of the ground (both steepness and direction), the canopy density, the honeysuckle population, and the height and diameter of the base of the honeysuckle. The canopy cover will be measured by the percentage of blocked sunlight by overhead branches and leaves. Slope will be put into four categories; none, slight, moderate, and significant. We will take measurements of the honeysuckle bush every five meters, along with measuring its size; we need to find out the age of the bush by cutting the trunk and counting its rings. Historical events, drought or wet season, will also be noted through observation of the rings. Observations of other invasive characteristics such as the smothering of ground cover and smaller shrubs or plants will also be noted. These tests/observations will hopefully provide results capable of answering the inquiries we have.
For Tuesday, October 24, we will split the class up in to four groups; each member of our research group will lead one of the class groups. Each group will be responsible for five strips of land one meter wide by twenty-five meters long. Two of the groups will take samples from the creek bed toward the forest interior and the other two will take samples from the forest edge inward. They will make observations on the slope of the land, canopy cover, and honeysuckle population. Also, they will take measurements of the height, width of the base, and age of the individual honeysuckle specimen. The age of the honeysuckle, however, will only be taken every five meters, by sawing the trunk in half and counting the rings.

Results

Conclusion and Discussion
The results proved our hypothesis correct with the exception of the fact that the subjects were not more abundant at the edge. It turned out that both the interior and exterior had about the same population. Also, the abundance turned out to be higher at the creek rather than the actual edge of the forest. This surprised us, since honeysuckle is classified as an edge species. Our results found that location from the edge does not affect the height of the honeysuckle. There is a direct correlation between the age and height of the tree. The reason for this being, the older the tree, the longer it has had a chance to grow. Finally, we also discovered that there was no apparent correlation between the age and the base diameter of the tree. The reason for this being is that there are multiple trunks that make up the tree. Each trunk has the possibility of being a different age, and since we only took a sample from one of the trunks, we do not know the actual age of the tree. We found that the more significant slope contained older trees. The reason for this being, the steeper slope causes less canopy cover, which makes it easier for the honeysuckle to grow. The slope also has a direst effect on the abundance of the honeysuckle with in the area, due to increased chance of seed dispersal in the area.
The only two tests, which proved to contain significant data, were the comparison of abundance and area, as well as abundance versus slope. Our t-tests for these two comparisons provided a value of less than .05. Many of our figures were based upon observation of the students performing the experiment, therefore leaving a large potential for human error. These observations included, the height of the bush above two meters, the abundance due to overlooking the smaller bushes, the canopy cover which was especially problematic due to the lack of foliage, as well as ring count due to the limitations of the human eye, also when it came to selecting a bush every five meters on which to collect samples we tended to favor the larger specimen due to the fact that they caught our eye first, and slope also was very much based on opinion. All of these things made some of our results slightly skewed.
The experiment we conducted focused on the growth of honeysuckle, as compared to many studies that focus on the effect that honeysuckle has on native species. By studying the habits of growth of honeysuckle, we may soon be able to find a way in which to limit and even end the spread of honeysuckle throughout the United States.


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