Forest fires are often regarded as having only detrimental effects on the ecosystems of the areas where they occur. Approximately two thirds of forest fires are caused accidentally and destroy acres of woods because they are uncontrolled and difficult to stop (http://www.infoplease.com/spot/forestfire1.html). These forest fires destroy healthy trees and shrubs that supported wildlife and the intense heat that they produce, vaporizes some of the essential nutrients from the soil into the atmosphere, preventing successful plant re-growth (http://flame.fl-dof.com/Env/nrf.html). With all of the negative effects of uncontrolled forest fires, is it possible to have prescribed forest fires under controlled conditions that promote better plant re-growth? We hypothesize that the ashes, which result from the burning of both indigenous and invasive species of plants from the southern Ohio region, will promote stronger plant growth (based on the height of the plant) when used to fertilize radishes. The purpose of this experiment is to simulate the effects of the change in soil composition that results from the on the re-growth of vegetation.
We created the concept of this experiment following the nature walk that we went on as a class at the beginning of the course. When we learned about honey suckle, the invasive plant in this region, and we learned about the negative effects that this weedy plant has on bio-diversity, we decided that a topic which related to a possible solution for this problem would be most relevant to our area. We believe that a controlled forest fire in this region could eliminate some of the competition between the weedy plants and other species, and would fertilize the soil in order to strengthen the renewed plant growth. Our experiment would help us accomplish the following: determine whether plants grow stronger in soil that is fertilized by the ashes of 4 different plants.
This research is particularly interesting because it suggests that forest fires might be beneficial for some wooded areas. This is a notion that most people are uncomfortable with because the destruction of any forested area is assumed to be harmful, even if the forest fire might yield positive results in the long run. Providing evidence that forest fires could supplement future plants with nutrients that would promote better lant growth. Also, since forests accumulate fuels, it is important for there to be smaller scale, occasional fires that will expend the fuel in small doses. As opposed to allowing for the fuels to build up and releasing them in a single, large-scale fire that would be much more devastating for the wildlife (http://flame.fl-dof.com/Env/nrf.html). It is our hope that through this project, we might be able to educate people about the positive effects of forest fires and their necessity to the balance of the fuels in the ecosystem. It is strongly suggested to analyze the different forest communities and their fire cycles, and realize we are falling way behind the natural cycle by thousands of acres. Analyst say, “We should be burning 5,000 acres or more a year just to keep up with current annual fuel accumulations, but we are lucky if we achieve 1,000 acres” (Wuerthner 1995). Research has shown that nutrients such as phosphorus, potassium, and calcium are returned to the soil after nitrogen is released in the fire. The fire also releases the seeds of some species that require the heat of the fire to initiate germination and thrives in the newly fertilized soil. Therefore, the plants colonizing these rich ashbeds are more vigorous than those growing outside them (Anderson). These regenerative effects are little known to the public and need attention to support the often misunderstood effects of forest fires.
History and culture have shown the benefits of forest fires in places where the indigenous people live off of their land. The Zulu often have regular cool fires that do not exceed a half a meter tall to promote hunting, so that the area is fertile for the animals (Woods 1995). In Madagascar, fires are used to remove the old, dry, unpalatable grass stalks and release nutrients, fertilizing new growth. They override the competitive effects of selective grazing, giving favored forage species a better chance. Finally, they can accelerate the growth of resprouts in areas of sufficient moisture by exposing the soil to the sun. This green bite is critical to cattle health--the protein-rich grass resprouts carry the cattle through the late dry season (Kull 2000). The importance of forest fires needs to be more widely accepted in order to help balance our ecosystem and allow the public to broaden their perspectives on other natural occurances in nature as well, rather than continuing to passively harm the earth.
MATERIALS AND METHODS
Reforestation as a result of forest fires is an important process to the balance of the ecosystem. Therefore, testing the result of ashes from invasive and native species on the growth of new vegetation is a vital part of assisting in regeneration. The experiment includes finding invasive and native species in the area of Southern Ohio and burning the plants (Honeysuckle, Norway Maple, American Beech, and Russian Olive) to create approximately 15 grams of ash that will be placed on top of soil already containing germinated radish seeds. The growth of the radish plants will be periodically measured, charted, and using these results, conclusions will be drawn on the effects of forest fires on new plant growth.
To decide which plants would be appropriate for the experiment, the assistance of an expert was enlisted to identify local pervasive plants. Honeysuckle, Norway Maple, American Beech, and Russian Olive were identified as common plants in the area, and therefore deemed good variables to test. Radishes were also chosen because of their easily recorded growth and heartiness in maturation. The samples of plant are to be burned on thermopads to safely and accurately record the temperature at which they flame to produce ash. The readings will also give a good estimation of the temperature at which forest fires either start due to natural causes like heat, lightning, intense sun, or even volcanic eruptions. The information will also provide a good idea of the limits of controlled fires that could potentially start a forest fire.
Because the effects of ash on plant growth are being tested, the ash will be added on top of the soil at the beginning of the investigation. The variables will consist of 75 small pots each containing radishes. 4 trays of 15 pots will be necessary for each variety of ash. The remaining 15 pots will be controls for the actual growth of radishes without the influence of ash. The plants will be watered as needed and checked for sprouting, and eventually growth, twice a week for the duration of 3 months. The results will be recorded, charted, and statistically compared to determine whether or not our hypothesis is correct.
This experiment is statistically sound because large sample size of each species tested will ensure accuracy of data. The population and consistency in the project will verify the outcome. The reason for this consistency is to produce accurate results that can give a better idea of the effects of forest fires. Choosing the number of samples was arbitrary as the objective is to find the effects of pervasive species on the regeneration of vegetation. To ensure that the results are not biases, many pots and radish samples have been allotted for the experiment to guarantee consistency and comparison. Though there are inevitably going to be errors, one error that seems to be the result of the lab is that there is little chance that we can actually use our small scale representation to accurately resemble a real forest fire. Therefore, our tests will only form a theory. The data collected by the class can also not be guaranteed, but since the class size is on a large scale, there is room for more discrepancy and ability to curve our results for better accuracy. The methods of collecting data and the importance of consistency will definitely be prevalent when introducing the project to the class due to the specific samples and precise measurements necessary to arrive at any conclusion. It is very vital in the experiment that procedures are executed to their best because of such a small estimated discrepancy between the radish growths.
Materials that are important to discovering the results of forest fires on regeneration include our 15 gram, each, ash samples of Norway Maple, American Beech, Honeysuckle, and Russian Olive plants; and the plant being tested, the 75 radishes, initially germinated. These plants will in essence, grow together in the soil, another important material. This soil also must be vermiculite, which will ensure the soil content devoid of previously mixed nutrients that may alter or bias the results. The amount will be the same in each pot, another important material to host the experiment, needing 75 pots. We plan on burning the plants in a metal container that is set down on concrete in order to ensure that the fire stays contained. Caplets that measure the temperature of a fire will be used when we burn the branches of the plants. A digital scale will measure the amount of amassed ash in grams to collect the required amount and other tools such as beakers, gloves, or goggles for protection and transportation of the ash.
The class will be involved in the study by assisting in the measuring process, which will be demonstrated so there is a consistency among calculations. The rulers will sit at the top of the soil long-ways, and the height of the growth, if any, will be measured in millimeters. The measurements will be taken at eye level and recorded on a chart that has specified slots on a grid for each individual radish plant. This collection of data will also be in trials so that more than one classmate is measuring the same plant, to ensure accuracy. The class will be asked to deliver it to the group member in charge of keeping the collective data and the results will be looked over for any major discrepancies. Data will be processed at the designated time to review the results statistically. We will calculate the mean growth of each type of fertilized plant that was measured the final time on November 15, and then we will use the ANOVA test to compare the means of these plants fertilized by the different types of ashes. We will also use the Chi-Square test in order to compare the expected (control- no ashes) value to each of the four different observed values (measured for the plants fertilized by the different types of ashes). This will help us to determine if the means of the heights for the plants that were fertilized with the different types of ashes are statistically different from the control, which was not fertilized with ashes.
The data sheet that assists this experiment will consist of the axes of time (days), and the samples heights with 75 spaces: 15 Norway Maple, 15 American Beech, 15 Honeysuckle, 15 Roman Olive, and 15 Control Radishes (millimeters). (See Attached Proposed Data Sheet).
Oct. 12 Burn the plants in order to obtain the ashes.
Oct. 14 Plant the seeds in the plots and fertilize with the ashes.
Oct. 15-Nov.15: Collect Data (includes twice weekly measuring height of plants. The Class is also involved in the collection of data in this part of our experiment.) Also, caring for the plants (i.e. watering).
Nov. 18-Nov. 22: Analyze data (includes performing statistical tests and noting the effects)
Nov. 20-Nov. 25 Write results (create drafts and final paper)
MODIFIED MATERIALS AND METHODS
The procedure was slightly modified from the intended methods. The methods that the group actually implemented were the following: the group decided on measuring the growth of radishes. To get the best statistical results it was determined that 15 radishes would be grown for every type of ash and there would also be 15 control plants. The group collected potting trays with compartments that were 1in. x 2in. x 3in. The group then filled each individual compartment with peat soil because that type of soil does not have any nutrient composition. In the soil the group planted two radish seeds for every compartment, that way there was a better chance of having at least one seed germinate. The group let the seeds establish for one and a half weeks, then if both seeds grew the group took out the smaller of the two sprouts.
During the time that the seeds were establishing the group collected branches and leaves from the four plants the were to be tested (Honey Suckle, Russian Olive, Norway Maple, and American Beech.) The branches and leaves were then dried out and kept separated from one another in plastic bags. Once dry the plants were then burned on top of an upside-down garbage can with a butane-lighter to start the flame and keep the fire going. (All the plants were burned individually and all ash was cleared before burning a new plant.) Tempil pellets were wrapped in aluminum foil and placed in the center of the branches to measure the temperature of the fire. Since both the 38 and 66 degree C pellets melted we can assume that the temperature was over 66 degrees C. Once all of a plant was burned the ashes were put into a small plastic Ziploc baggy; each pile of ash got its own bag.
After all of the ash was collected the group added it to the growing radish plants. Two milliliters of ash were placed in each compartment, to fertilize the soil of each individual plant. The group used a beaker to measure out the ash. Fifteen of the radishes were kept unfertilized by ash to be used as a control group.
The plants were kept in a green house with a consistent temperature and watered every weekday with distilled water.
The group measured the growth of the plants once a week for three weeks. The group used the same ruler to do the measurements each time. A group member would obtain measurements by placing the ruler at the base of the soil next to the radish being measured. Then the member would pull the radish being measured up straight so that there would be no bends or twists in the plant. With the ruler next to the plant the member would measure to the base of the tallest leaf. The measurement was then recorded to the nearest millimeter on a table that was consistent for all three weeks.
After all of the data was collected the group discussed with the teacher (Vivian) what type of statistical analysis should be done with the data. Then the group plugged the raw data into Statview and ran various tests.
We were able to generate data from 3 consecutive weeks of measuring each plant 2 days after we fertilized the plants with the ashes from beech, maple, honey suckle, and russian olive plants. The three sample sizes for each week were 75.
Tables 1, 2, and 3 display the results of a paired t-test which was conducted with the help of StatView in order to compare the means of each variable group (beech, maple, honey suckle, and russian olive) to the mean of the control group for each week. Out null hypothesis in each case was that the mean of the control group was equal to the mean of the individual variable group (beech, maple, honey suckle, or russian olive). In Table 1, we failed to reject the null hypothesis for the beech, honey suckle, and russian olive groups because their t-tests resulted in p-values that were greater than .05. However, the p-value for the maple group was .0188, leading us to reject the null hypothesis. For the second week, we failed to reject the null hypothesis for the honey suckle (p-value=.0825) and the russian olive (p-value=.0502) groups meaning that there was no statistically significant difference between the means of the heights from those two groups and the control group. For the beech and the maple, we were able to reject the null hypothesis (p-value<.05), which would lead us to believe that the means of the heights from these two groups were significantly different from that of the control. In the t-test results for the third week, we rejected the null hypothesis for each group because the p-values for each test were considerably less than .05.
We also ran a t-test for the means of the heights of each plant group (beech, maple, honey suckle, and russian olive) combining the measurements from the three weeks and found that the p-value for each group was less than .05. This led us to reject the null hypothesis and conclude that the overall, each group that was treated with the ashes had a significantly higher mean height than the control group.
Graphs 1.A, B, C, D, and E are line plots that were constructed using StatView, which include the ranges in values of the heights of the plants from each group (control, beech, maple, honey suckle, and russian olive) for each week. Both the control and the honey suckle graphs1.A and D show that there was a consistent and linear growth over the course of the three weeks. The beech, maple, and russian olive groups, which are depicted in graphs1.B, C, and E, show that there seemed to be an exponential growth in the plant heights where the plants showed an increase in the rate of growth over the course of the three weeks.
In graphs2.A, B, C, and D we ran a bivariate linear regression using StatView, which test the control versus each treatment group from all of the weeks together. These graph were inconclusive based on the small R- squared values, which indicated that there’s no linear relationship between the any of the treatment groups and the control.
The results show that there is significantly more growth in the plants fertilized with ash, which supports our hypothesis.
The greater rate of growth in the treated plants could have also been experimented in a different manner. Alternative experimental plants might have affected the results, as radishes are very hearty in general. The experiment could have included a variety of plants to see if the ash was consistently increasing the rate of growth. Not only the rate of growth, but also if the ash, which provides nutrients, makes a healthier, heartier plant. The health of the plant was difficult to asses in radishes, because of their aforementioned hearty nature. Also, the method of ash infiltration with the soil might have also been varied. According to our research, the composition of post-burn vegetation includes chemicals such as C, N, P, K, CA, and Mg at varying levels of concentration (Vijver et al 1999). Because the resident greenhouse manager advised us not to fertilize plants when they were just beginning to sprout, the ash additions were not made till the latter weeks of the experiment. However, at times, the group held reservations of whether we waited too long to implement the ash as the plants were just starting to grow. We may have had even more consistent results if an additional week allowed for another data collection. Our results indicate an exponential growth in the fertilized plants versus a linear growth in the control. The exponential growth, however, may have become a linear growth, indicating that the ashes only have a temporary fertilization effect. Therefore, at that time, we might have considered adding the ashes again to see the if the growth began to continue exponentially again, verifying our results.
Using young new radishes also makes us wonder if the same exponential growth would occur in established, less susceptible plants such as older trees. However, because our experiment was inspired by regenerated forests as a result of forest fires, we assume that the ashes would be used for new plants. But testing the growth on older plants would even further verify our results.
Qualitative measurements were also a large source of error in our experiment, as “measuring from the base of the plant to the tallest start of a leaf” can leave room for at least a centimeter variation. However, the disparity in the results was so significant that precise measuring seems auxiliary. Our measurements were conducted by the same person every time, thereby decreasing the variety in judgments of height.
Other sources that could have affected the growth of our plants along with the ashes, could have included location of our plants in the greenhouse, whether they were moved around or not, determining sunlight exposure, neighboring plants, and consistency of watering times as executed by the greenhouse staff.
As expected the plants began at the same time and grew in synch with each other, but then eventually as the ashes took effect, the differences in growth rate became evident, indicating to the group, healthier plants. Though the ashes may not have been the only factor in their rapid growth, as compared to the control groups, they have significant difference in size. Therefore, we conclude to reject the null hypothesis and acknowledge the positive effects of ash on new vegetation.
Anderson, Robert. “Still Life.” Natural History. (1995): Vol. 104, Issue 12, p.74.
Kull, Christian A. “Madagascar’s Burning Issue.” Environment. (220): Vol. 44, Issue 3, p. 8-12
Johnson, David. “Fire Zone” http://www.infoplease.com/spot/forestfire1.html
Woods, Michael. “Under Fire.” Geographical Magazine. (1995): Vol. 67, Issue 12, p.30-34.
Wuerthner, George. “Fire Power.” National Parks. (1995): Vol. 69, Issue 5/6, p. 32-38/
“Natural Role of Fire” http://flame.fl-dof.com/Env/nrf.html
Vijver, Van de, Poot, P., Prins, H.H.T. 1999. Causes of increased nutrient concentrations in post-fire regrowth in an East African savanna. Plant and Soil 214, 173-185.
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