Jay Axe, Matt Cottrill, Paula Moran, Neil Rosonthal
NSI- Section C
December 7, 2000
“Damaged Trees and Their Sufferings”
Understanding the importance of damage within a forest, through this lab we have proved and developed the idea that type of tree damage is related to location within the forest. Through speculation and statistical analysis, we have arrived the theories described within this text.
Damaged trees exist within any given forest. From exterior to core, they are located in different degrees of damage. Considered in this lab the possible forms of damage were insect infestation and wind damage. To gather information for this topic, we examined damaged trees within the proximity of Western College of Miami University of Oxford, Ohio.
In first researching the topic of trees, we specialized in the Osage orange and the effects of landscape location on the tree’s general health. Upon researching this species of tree, we found that the Osage orange species are extremely resistant to damage and are equipped to gather water in any location. Also, these trees are too sparse to study to find effects that the landscape has on the general health of the Osage orange Tree. While studying these trees preliminarily, we stumbled upon the realization that due to impending season change the Osage orange tree would soon be loosing its leaves and all the green monkey-brained shaped fruit had fallen of the tree. Therefore, obtaining accurate data under these circumstances would be near impossible.
While out observing Osage orange trees, we had noticed one particular tree with extreme damage to its lower branches. This made us think about tree damage throughout the forest. After we had realized that we could not pursue the Osage orange tree lab and we were considering our other options, we decided upon studying tree damage as a whole. Then, in attempting to apply tree damage to the universal class theme of landscape ecology we decided to compare tree damage between different landscapes. With further group analysis and discussion our lab group decided upon narrowing the focus of the student generated lab to comparing tree damage between the fringe and interior areas of the forest. After researching our new student generated lab topic and discussing the research, of damaged trees, we hypothesized that in the interior of the forest the amount of insect damage will be greater than wind damage, due to tree density and the ability of insects to travel easier between trees. Conversely, on the exterior of the forest the damage will be due more to wind because of the lack of cover and, therefore, have greater exposure to the elements.
So after beginning research on Osage orange trees, we arrived at a hypothesis about the location of two types of damage within a forest. It was through discussions, periods of research, analysis and deductions that we finally emerged at our final hypothesis that is submitted in this lab packet.
Relevance of our research question
Research on articles about tree damage and its causes included many different types of studies and conclusions that were helpful in producing our lab and hypothesis. The articles contained research about what caused the specific tree damage. The types of damage that we read about were wind and insect damage. One article describes certain tree structural defects, such as dense crown, too narrow or wide of a crotch, that make trees prone to damage, but the article does not say what locations make trees prone to damage (Sunset). A dense crown is described in this article as a top-heavy canopy of foliage that is prone to catching wind, which causes tree limbs to snap. Next, a narrow crotch is defined as a limb growing almost vertical, which can cause the wind to spilt the crotch and, thereby, breaking off the limb. Inversely, too wide a crotch, or an almost horizontal limb, can receive stress from wind and weight of rainwater on foliage. Thusly, in our lab we may infer that if there is no apparent insect damage that the cause of limb breakage is due the tree having either too dense of a crown or having a narrow or wide crotch. In another study of wind damage, set up testing the strength of trees in serve wind areas, for classification of trees damaged by wind uses the terms bent, leaning, snapped, and uprooted (Cooper-Ellis et. al.). To relate this to our lab, we will be employing these terms to describe the trunks and/or limbs of the wind-damaged trees.
To further our investigation, studying research on insect damage has given us needed insights into classifying insect damage. One study, studying the effects of leaf-eating caterpillar damage to young trees, found that if a young tree is damaged by these insects it will be healthier in the long run compared to trees that were not infested (McDonald). Because our study is being executed during the autumnal season, we will be excluding this observation, but this information to know for future studies. Another study describes how Long-Horned beetles specifically threaten any trees in the United States (Milis). It goes on to describe the damaged caused by adult beetles, which are tunnels bored into the interior of the tree. The author desires to bring to our attention how to rid the US of these pests. Identification of these beetles is the first step of getting rid of them. In the article, they are described as “shiny, jet-black beetles with distinctive white spots” (Milis 3). In our lab, we used this article to understand the threat that pest, in the form of insects, is involved in tree damage throughout the forest. We are identifying the degree that insects harm trees and hence produce a threat to our local environment.
Our research expanded on type of damage to find out where tree damage occurs. This knowledge can be used to know where trees should be planted in order to ensure their safety from tree damage.
Materials and Methods
The processes used in this lab were both analytical and observational. Before our lab lead the class on the Twenty-seventh of November, our group formatted two charts in which data collection would be taken. In preparation for this data collection, we located 40 damaged trees within walking distance of Western campus. This number of sample trees was the desired minimum number for an accurate study. These trees were be damaged by either infestation by pests or wind damage. To analyze our hypothesis about the interior verse the exterior forest areas, we divided the number of damaged trees studied into two groups. We studied 21 trees in the interior of the forest and 19 on the exterior of the forest. (These two numbers were randomly chosen because we found more damaged trees within the interior than the exterior and desired our data to reflect that.) The exterior is defined here as thirty feet into the patch from the furthest tree located on the outside of the patch, while the interior is anything thirty feet from the exterior rim of the patch. Before having the class gather data for our lab, we assigned the trees numbers (1 to 40) to simplify the data collection process. These numbers were placed on the trees with orange flagging ribbon, in order to make them easier to find during the research class period. During the class period, we divided the group into four groups and proceeded into the forest to collect data on our trees. Here are the charts we used to collect data on that day:
Before the class helped in data collection, we had filled in the first chart with the type of damage our group found the tree to have. There were some trees of which we were unsure and had the class assist us in observing which type of damage it looked more like. After we had established which type of damage was present (i.e. Wind, Insect, or Both), we began to quantify observations about the degree of damage that happened to the trees (e.g. the purpose of Chart 2). We quantified these numbers according to the following scales, in order to have comparative analysis of the damages that occur in the different areas of the forest:
For Broken/ Missing Limbs:
A 0 to 10 scale will be used.
0-being the least- i.e. no broken limbs
5-being 50% of the branches broken
10-being 100% of the branches broken
Taking an average of the exterior numbers verses an average of the interior numbers, we can get a comparison of limb breakage
For Missing Bark and Insect Holes:
A 0 to 10 scale will also be employed with 0 being none and 10 being 100% of the tree having insect holes or missing bark.
These numbers will be averaged as well for comparative analysis between the two locations.
For Angled Growth:
A terminology will be used to understand the differences in wind damage in the two locations. Here is that wording system:
Severe - > 45degree from the perpendicular
Moderate- 45degrees to 20degrees from the perpendicular
Slight- 20degrees to 10degrees from the ndicular
Irrelevant- 10degrees to 0degrees from the perpendicular
Although this data could be biased due to human error, we have complied it to merely simulate a way to understand how much tree damage occurs with different parts of the trees due to location within the forest. By graphing and analyzing this data, we could see the differences or the similarities in damage.
After we collected the data, all (including the categories of interior verse exterior and insect verses wind) were compiled into Statview 5.0 in order to get good analytical graphs and numbers of the data. We compared the damage type with the location in a Contingency test to see where are hypothesis landed in the relation to the observed data. To get the P-value of our Contingency test, we made a Statement test to see how accurate our statistics were. Finally, we constructed Cell Bar Graphs under an unpaired t-test in order to compare the numerical damage data in relation to the location. With these graphs and P-values, we could see how location related to the degree of damage to different tree parts.
Our hypothesis is that there will be more insect damage in the interior of the forest and more wind damage on the exterior of the forest. The interior of the forest will have more insect damage because of the proximity of the trees - the trees are closer on the interior of the forest than the exterior therefore insects can travel easier between the closer trees in the interior of the forest. The exterior of the forest should receive more wind damage because the tress are father apart making them more exposed to the elements and harder for the insects to travel from one tree to another to cause damage.
After gathering our data we entered all the data into Stat-View to compare the large amount of information in the data. Here are the initial charts filled in:
While in Stat-View, we calculated a P-value to test the probability that the differences in the data gathered were due to chance. Our calculated P-Value was .0158(See Chart 5). This is a very low P-Value. Since our calculated P-Value is below .05 then it can be concluded that there is a very low probability that our data was a product of chance. Therefore our data can be accepted as valid and further data analysis can proceed.
By looking at our data chart it was evident that there was more insect damage in the interior of the forest than in the exterior of the forest. To compare exact numbers we used Stat-View once again. Using Stat-View once again we were able to plot out exact numbers within a Contingency chart format. Here are those charts we constructed with Stat-View:
The first chart (3) is the actual observed values; the second (4) is the expected values that were calculated by Stat-View, and the third is the Summary Table (5), which gives the P-value discussed in the previous paragraph.
chart three: Observed Frequencies for placement and type
chart four: Expected Frequencies for placement and type
chart five: Summary Table for placement and type
For all the data there were eleven wind-damaged trees in the interior of the forest, and seventeen wind damaged trees in the exterior of the forest. Thus concluding that there is more wind damaged trees on the exterior of the forest than in the interior of the forest. In the interior of the forest there were ten insect damaged trees, and in the exterior of the forest there were only two insect damaged trees. Thus it can be concluded that there are more insect damaged trees in the interior of the forest than the exterior of the forest.
The contingency tests in Stat-View produced expected numerical values for the distribution of the different types of tree damage. For wind damage the contingency tests predicted fourteen and seven tenths trees would be damaged in the interior of the forest and thirteen and three tenths trees would be wind damaged in the exterior section of the forest. These values do not match up very well to the gathered data on wind damage, though the expected values for wind damage are relatively close as are the gathered data values. For insect damage in the forest the contingency tests predicted there would be six and three tenths trees with insect damage in the interior of the forest and five and seven tenths trees with insect damage in the exterior of the forest. These expected values are closer than the data values gathered, but the two sets of values do follow the same pattern. Both the expected and observed values have more insect damage in the interior of the forest than the exterior of the forest. The expected data values are not as accurate as they could be because we sampled twenty-one trees in the interior of the forest and nineteen trees in the exterior of the forest. The unequal values made the expected values of the contingency tests less accurate.
We also calculated the overall percentages of the locations of the tree damage through Stat-View. Here is that chart:
chart six: Percents of Overall Total for placement and type
Of the damaged trees twenty-seven and one half percent of the trees were wind damaged interior trees. Forty-two and one half percent of the trees were wind damaged exterior trees. Twenty-five percent of the trees were insect damaged trees on the interior of the forest. Only five percent of the damaged trees were insect damaged in the exterior of the forest. Fifty-two and one half percent of our damaged trees were located in the interior of the forest. Seven-seven and one half percent of the damaged trees were located in the exterior of the forest. Seventy percent of the trees were damaged by wind, while insects damaged only thirty percent of the trees. Of our data the majority of trees were damaged by wind. The most common type of damaged among the trees was wind damage on the exterior of the forest. There were four times as many insect damaged trees in the interior of the forest than there were on the exterior of the forest. The data statistics support our hypothesis.
To gather a more in depth comprehension of the tree damage we also cataloged the different aspects of the tree damage. These aspects included branch damage, insect holes, bark damage, and angled growth. Angled growth only occurred on those trees that were wind damaged, and predominately those trees in the interior of the forest. The conclusion was made that angled growth was more attributed to the trees’ need for sunlight and growing accordingly to get it, than due to damage. For further discussion of our results from these tests see Appendix A attached after the Sources Used Section.
Discussion and Conclusions
Our research for tree damage led us to better understand where tree damage mostly occurs in the forest. From the data taken, we believe our hypothesis to be true. (As discussed within the Results section and exemplified with data charts.) There is a greater amount of tree damage from insects on the interior and a greater degree of wind damage on the exterior. Our results have shown that there is a fairly equal degree of insect damage on both the interior and exterior of the forest. We believe this to be true because there are a large variety of insect species that feed on trees in the forest. Each of these species has adapted different ways of traveling to trees. The insects have adapted to fly, craw, jump, or even be carried by other organisms to get onto the trees. This is what leads us to conclude that tree damage from insects is fairly equal throughout the trees in the forest.
In terms of wind damage, our results have shown that there is a much higher degree of damage on the exterior of the forest. We conclude that this occurs because the trees are more susceptible to wind from not being surrounded by other trees. Trees that are more densely growing together have more competition for sunlight and growing space, but help each other in terms of combating wind. The trees on the exterior of the forest do not have this tight nit connection to trees, which causes them to be subjected more to wind damage.
We believe our research to be relevant because we chose patches in the forest that are virtually untouched by humans. Other ideas for relevant study could be to take data from a larger number of trees. This could allow us to get more distinct results in the difference of wind and insect damage, with respect to insect holes, missing bark, and broken limbs, in areas of the forest. We believe that with more tree sampling, there will still be the same results overall. This thought was lead to by the very low P-values we received from our data analysis, meaning our data is very unlikely to be due to chance. With these low P-values, it is very possible that the results would be the same even with more data collection.
On a broader scheme of thinking, we could use this information on tree damage to understand what is the largest factor for forests that begin to naturally disappear. We understand that in order to help save a dieing forest, you should pay more attention to the wind damage on the exterior of the forest. This will allow us to concentrate our efforts in the best way to save trees that would die on their on in the forest. Conversely, you would pay attention to insect damage as the main problems for trees on the interior of the forest. Further investigation to what kind of insects cause damage to trees would be helpful in controlling pest infestation. The types of trees that are most prone to being damaged would be helpful in narrowing where the problem mostly lies. Therefore, if someone were to study a specific tree type, they could help in finding if that type of tree follows our hypothesis guideline.
Furthermore, if someone were to further our lab study, possibly looking into how the different degrees of damage affected the overall results would be a good way to approach this lab. If someone could find there to be a correlation between the degree of damage and the location in the forest, it would be help in determining how forest are damaged even more specifically.
Also, if someone were to study the effects of the damaged trees on the forest as a whole, it would be interesting to see how our lab could help them. By being able to know what type of damage occurs where in the forest, this future group would have an advantage on their study and a way to narrow it down.
Our study was successful in broadly describing where and what causes tree damage to occur most often. It is a good start in describing what causes trees to be damaged. Our information can be used as a guide for understanding further research to specific problems in forest due to tree damage. Through studying damaged trees, we hope to have given light onto how forests may be helped if they are in danger of extinction.
“Induced defense in white oaks: Effects on herbivores, and consequences for the plant.” Ecology July 1994: 1356-1369.
“Prevent tree damage from storms.” Sunset Fall/Winter, 1996. http://www.findarticles. com/cf_0/m1216/1996_Fall-Winter/18691386/print.jhtml http://www.findarticles. com/cf_0/m1216/1996_Fall-Winter/18691386/print.jhtml
“What Tree is it.” Ohio Public Library Information Network and The Ohio Historical Society,
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