As the semester began we were presented with the problem of a student-generated lab. In the upcoming semester our group was to pick an interesting topic and create a process in which we would go about solving and proving or disproving our hypothesis. As our group started to think of ideas for our lab, we noticed fall was approaching quickly and that the leaves would soon be changing colors and starts falling to the ground. So we decided to find out for ourselves what exactly happens to the leaves after falling to the ground and how different environments will effect what happens to the leaves. As we dove further into the project we decided on finding out how would different environments effect the decomposition of different leaves. Next we picked out three trees in which we would take the leaves from; the trees are Maple, Buckeye, and birch. The environments that the leaves would be placed in were the Western duck pond, a natural environment, and the lab setting. After we set the experiment up we came up with our hypothesis which was that the leaves submerged in the duck pond will decompose slower than those in the lab, which will decompose slower than those placed in a natural setting. We believe that those in the natural setting will decompose the fastest because they are exposed to the elements, to bacteria and other factors in which the lab and the pond will not produce. Next we believe that the lab setting will decompose because lack of sun, air, and moisture which the leaves would normally come into contact with. And finally we believe the leaves place into the duck pond will decompose the slowest because the constant contact of water, we believed that because they are not drying out they will decompose the slowest.
Through our research and dedication to this project we planned to discover many details of leaf decomposition that before had never crossed our minds. The first thing we planned to accomplish was to be able to find out exactly what would be the fastest environment in which these leaves would decay. Along with which environment would decay the leaves the fastest another question arose, which type of leaves would decompose quicker, maple, birch, or buckeye. We also planned on learning what type of factors such as bacteria, moisture, and air effect water happens to the leaves. Although these parts of the student generated lab were very important we also planned on taking with us another important aspect of science. We plan on learning how to set up the process of making a hypothesis, setting up a way of solving our hypothesis, analyzing our data which results from our studies, and then putting it all together to prove or disprove our original ideas.
In order for our project to have relevance, we took a look at how leaf decay is
Crucial to everyday life. We will tie this is in with everyday occurrences. If we are hypothesizing that decomposition is a direct factor of moisture loss and therefore loss of mass, when the leaves are exposed to great amounts of water, what will be the results? For instance, when leaves fall to the ground and it rains, does that slow down the decay process? What if after the leaves fall there is a drought and no water touches the leaves, does this speed up the process of decomposition?
Our experiment relates to a larger question in many senses. We now find ourselves wondering how the decomposition of particular leaves act as fuel to our ecosystem. With decomposition the idea of reforestation is better visualized as a possibility for the future. After leaves fall they build up on the forests' floor creating a layer of nutrients and life filled litter on top of the soil. This layer is not only any important part of the food chain as it acts as food for many bacteria and other microscopic beings. But more importantly it acts as a way of recycling the nutrients back into the forest through the soil. As the leaves break the nutrients are released and are absorb back into the ground where it then helps to feed the vegetation in the surrounding area. This is part of reforestation. Without decaying leaves there is no way that reforestation can take place. Without reforestation the nutrients in the ground would not produce vegetation. Without vegetation there would be no efficient way to change CO2(carbon dioxide) into O2(oxygen). And without oxygen the world and all of its life could not exist. So as you can see the decomposition of leaves is extremely important to our everyday life. For without decomposition we would not be living right now.
Research and Relevance:
As we began our lab, we started to look for related articles that could help us with our lab and our hypothesis. As the group separated and went to the library, everyone came up with research that all were different, but many of them seemed to be quite interesting.
As we brought all our work together, we started to review the work that had been collected. The first article that was brought forth was the article of J.H.C. Cornelisson's article "An experimental comparison of leaf decomposition rates in a wide range of temperate species and types" which was published in the Journal of Ecology, volume 84n4, August of 1996. Which is contained within the pages of 573 to 582. This article had a profound affect on the work, which we were about to enter upon. In this article, J.H.C. Cornelisson writes about an experiment in which he took 125 different types of leafs and placed each species into two different bags. He then placed the two bags into two different environments, which contained different life forms. Cornelisson, through this research, found that, under the same conditions, leaves of the same condition would decompose at approximately the same rate. As we all looked at this article, we were very much intrigued by what it had to say. As we started to look at the next article, Jorge G. Cepeda's article "Decomposition Patterns of Surface Leaf Litter of Six Plant Species along a Chihuahuan Dessert Watershed" of The American Midland Naturalist which was published in volume 123n2 (April of 1990) and contained in pages 319 to 330. We started to see a pattern. In this article Cepeda describes how he had taken six different types of plants leaves to an area that it was not indigenous to. He found that those areas in which to leave are placed affect the decomposition of the leaves. The group began to notice that these two articles were working with the comparison of different leaves and in different environments. That, ultimately, became the center of our work.
As we began to work on how we were going to go at the project, we started to look at the other article that had been collected. But before we could actually begin, we had to know what caused leaves to decompose. That is when we turn to the article by C.H. Dickinson. Within Dickinson's essay, Biology of Plant Litter Decomposition, he breaks down how a leaf breaks down. It also helped us to understand a little bit how this affected the world, just wait hays, we will be getting to that. Since we now knew how a leaf decomposed, we wanted to know a little bit more on what caused the leaf to disintegrate. That is when Angana came to us, all ghitty, say that she had found the perfect article that would tell what caused the leaf to decompose. That article was by S.W May and P.G. Risser, titled Microbial Decomposition and Carbon Dioxide Evaluation at the Osage Site. Its technical report number is number 222 in the U.S. Biological Program. In this article, the two scientists described that carbon dioxide was a major factor in the break down of the leaf's infulstructure. It helped significantly in the temperature and the time process to decay material. As we read this, the whole group was kind of confused, and turn to Ms. Smith for a little bit of interpretation. That is when Angana stated that carbon dioxide helped by heating the leaf. Through this heat, the cells would start to die off and disappear. That is when the leaf initiates the decomposition process. When Angana put it into laymen's terms, it began to make sense. But where could we find environments that had carbon dioxide? That is when Marita, in her infinite wisdom, told us that carbon dioxide was everywhere. She said that she had learned that in like fourth grade and that we were all idiots. That kind of hurt but we forged on.
At this point we were kind of lost on where we where going to place our precious leaves. That is when we turn to two sources, one was the lab, "Leaf Decomposition" by Matthew Nudelman and company, and the second one was the amazing, the all great, the all knowing, the smart Hays Cummins, he was kind of like our own Wizard of Oz. Through these sources, we started to work on the process of how our lab was to go down. Through last years group we found that if we worked with two different variables, which was the different environments, and had one control, the lab, we could actually do this. We also, through the patience of Hays, decided to use three different types of leaves. This was only the beginning though. The other articles we used was, Michael Overcash's Decomposition of Toxic and Non-Toxic Organic compounds in Soils, which talked about decomposition in different environments and how temperatures affected decomposition.
We also found, through our research, the profound effect that leaf decomposition has on the world we live in today. C.F. Mason's book Decomposition stated that the nutrients that come from the decaying of leaves are a vital and constant value for the growth and the death of the forest. That for a healthy ecosystem, the ecology must have the minerals that are found in the leaf's structure. Also in Michael McCain's article in the June 1998 volume of Ecology titled "Driven By Nature; Plant Litter Quality and Decomposition", we found the forest life systems is based on its ability to recycle what dies. For the forest to flourish, the forest must reuse all the items that it may lose. This is also described in C.H. Dickinson's article, which was stated above. But as we found out, the forest is not the only ecosystem that must have decomposed leaves to survive. In J.A. Perry's article in the magazine, Bioscience, titled "X-ray Microanalysis of Leaf-Litter Decomposition in Lakes", he states that for the lake ecosystem to survive, that the microorganisms in the water must have the nutrients from the leaves to live. If the organism did not have this then they would die. Without this, certain fish, which feed off the microorganisms, would start to die off. This would greatly affect the food chain of that specific lake and may cause it to die off. We also found, off the Internet, that if leaf decomposition were to cease, that reforestation would not be possible. Without new forest, the earth population would greatly affected by the loss of oxygen in the earth's atmosphere.
MATERIALS & METHODS:
When our group got together our idea was to put Birch leaves in many different environments. As we actually put some thought into our student generated lab we decided to have more than one type of leaf and 2 different variables with one set control. So as we proceeded we went on to have Maple, Birch, & Buckeye tree leaves. Our environments were pond water, natural environments, and the lab environment. As we proceeded we collected 180 leaves of each type. We placed 60 of each leaf type in each environment. And after a set number of days we would extract 20 leaves of each type from each environment. After each collection we would have 180 leaves. We would then dry them in the oven and weigh them. Before we put the leaves into their environments we dried, numbered, and weighed every single leaf. We proceeded to do the procedure one more time. This was how we were going to find out how we were going to find out which environment would decompose leaves the quickest. Even though this experiment might seem easy, it was very complicated and involved a lot of data. We chose to have many leaves so we would have enough data in order to come up with the correct conclusion. We decided to do it this way because we wanted to have two variables, the pond, natural environment, and one control, the lab. We chose to have three types of tree leaves to see if a certain environment effected each leaf the same. As we got going with our experiment we would often go talk to Matt Nudelman, a sophomore, who did a very similar experiment. Though his experiment was a little different, many concepts were very similar, which made it a little easier for our group to continue with our experiment. It also helped us to ensure that we were on the right track.
Many of our groups members had different views on how things should be done and what some things ment. So to ensure that all of our procedures and results were equal we made sure all the group members approached all the procedures in the same manner. We wanted everyone to actually understand what we were doing. We made sure that our results were varying and giving us the right data. To make sure we were getting complete and accurate data we had a lab control that would help us determine what our results would end up being. We hoped that our data was constant with the previous collected data. To make sure that all of our results were the same, we would check up and make sure who ever collected the leaves did it correctly and made as few errors as possible. As we worked through this lab we had few, but very crucial materials that make our lab complete.
Our first main material was an oven. The oven is generally used to dehydrate (dry) anything that may be needed to. In our case we used it to take all the excess water out of the leaves. All 540 leaves were dried and then individually weighed on the digital scale. The scale was also a very important in our experiment. Losing mass was pretty much the entire objective of our lab. The materials that we used for our environments were gutter-guard, mesh screens, hemp, and emptied 20oz. Bottles of pop. With all those materials we constructed a contraption that resembled a rattrap. It consisted of three sections that housed our leaves in the pond. The mesh screens were used to separate the leaves in-groups of 20. This contraption was also very crucial in our experiment. Last we used the basic materials that were very necessary in completing our lab. We used our computers, calculators, paper, pens, pencils, and obviously our minds. With our simple materials we wanted the class to experience what we had to go through.
When we involved the class in our experiment we had them pick ten leaves off the ground and ten leaves off the tree. We had three groups and they were told to use the same leaves as we did, to determine the loss of moisture, which in turn lost mass. That is what we were trying to convey to the class. Afterwards the class processed the data into Statview. They got to see the significant difference in the masses and were able to understand what the objective of our lab was. They did not get to use the oven but they did get to see and understand why it was used to make our lab much more accurate.
A selection of leaves were placed in a cage-type object and then placed in the duck pond on Western Campus. This pond has been the home of 2 swans, a duck, and God only knows what else for (apparently) a rather long time. Because the pond also serves as a lavatory for its tenants and any passerby, large amouns of (we're guessing) swan waste accumulated on the components of the cage. This small glitch may have accounted for various things. The swan "doody" made it very difficult to separate the individual leaves from one another. What we proceeded to do was dry them out first, and then try to separate them. In the process, many leaves broke into various pieces. The maple and birch leaves separated rather easily, but the buckeye leaves were more fragile than the others. We tried to mass the leaves with their broken parts, but some small portions may have been lost in the process. This could attribute to why those particular leaves weighed a lot less coming out of the pond. The accumulation of swan "poop" could also have provided the leaves in the pond with an excess of bacteria that may have eaten away at the leaves. Ultimately the pond was supposed to serve as a natural water setting for our experiment. Unfortunately, this added factor may have sped up, or slowed down the results that may have occurred in a non-swan-infested pond.
After careful recordings of all of our data, we observed that the placement of leaves into their environments was completely random and not by number. We did not use the numbers written on the leaves as indicators of where the leaves would go, so the data was rather difficult to sort through. To simplify the understanding of the data, we renumbered the leaves according to their type and placement. Leaves placed in the natural environment would thus be numbered 1-60 for each type, leaves placed in the lab would be numbered 61-120 for each type, and leaves placed in the pond would be numbered 121-180 for each type. This renumbering system assisted us in keeping our data straight when entering it into Statview. We also assigned each period of time a specific name. The original masses were named "A" the first set of data collected were named "B" and the final set of data collecterd were named "C". The complete random placement was still maintained while the numbering became more organized.
From our meticulous analysis of our data, we came to many conclusions. Please keep in mind the miniscule margin for human error. We originally hypohesized that the leaves on the land would decompose the quickest because of their exposure to sunlight, nutrients, and micro-organisms feeding off of them. We then hypothesized that the leaves in the lab would decompose the second fastest because although bereft of sunlight, they would be exposed to oxygen and heat from the heating system, not to mention artificial light, and dry air. We guessed that without moisture, the leaves would decay somewhat quickly. Finally we gaathered that leaves in the pond would decay the slowest because with a plentiful amount of water surrounding them, they would have a harder time losing any moisture. Our results came to prove us blatantly wrong (of course we are still a little concerned about the effects of swan "cah-cah" on our pond leaves). The numerical data we garnered concluded that the leaves in the pond overwhelmingly decayed the fastest. Next was the leaves in the natural environment, and the slowest to decompose was those in the lab. Our results came as a huge surprise to us; unsuspecting Breakfast Club that we are! The results, after careful consideration, began to make a lot of sense.
B.) The statistics that we found to be most useful was, of course, the p-value from the T-test. That happy little P-value helped our group to see that although our hypothesis was completely wrong, our theory that different environments affect the decay of leaves, was still correct. Our p-value came out to be .0001 which is less than .05 so we REJECTED THE NULL HYPOTHESIS that different environments have NO relevant effect on the decay of leaves.
Another statistic we found very useful was the overall means of the sets of data. The means allowed us to see the general changes from one data collection time period to another. This in turn helped us to see whether the leaves were losing mass, gaining mass, or staying about the same in mass. One of the data tables we recorded was ultimately going to organize what percent of the original mass of each leaf remained at each different time interval. The other data table compared the actual masses from one time period to the next. These data tables correlate, but they display the data very differently. The graphs that were produced from these data tables helped us to visually see the data displayed. These are the most effective ways to display our results. Two graphs that were really effective were bar graphs that mapped the overall change in percentage of mass for each leaf, in each environment. The bar that represents the leaves in the pond shows a great decrease over the 30 day period. The pond leaves decreased to about 77% of their original masses. The laboratory leaves dcreased to about 97% of their original masses. The natural environment leaves decreased to about 98% of their original masses. The graphs, along with our numerical data, allow us to assess the information we collected.
Discussions and Conclusions:
How we got our results
One important aspect of our backgound research relied on analyzing what Matt Nudelman's NS group did last year. They took one type of leaf and place it in four different environments. Having faith in Nudelman's results, we decided not to just reconstruct a leaf decompostion lab using their same method. Instead, we wanted see if their was a different decomposition rate among different types of leaves in different environments.
In response to the route our group wanted to take with this project we chose birch, buckeye, and maple leaves for our lab. We then placed them in three very different environments. By doing this we received some surprising results. One conclusive result was that our hypothesis was rejected. Leaves in their natural environment do not decompose the fastest. In actuallity, leaves in the pond caused every type of leaf to decompose more drastically than the other types of environments.
We found that overall our three different types of leaves followed similar patterns and that according to our lab leaves decompose at a similar rate. One intriging piece of data was that our maple leaves in the natural environment actually gained a little mass. We believe that this gain in mass was due to bacteria that was on the leaf when it was weighed. Besides the one boggling piece of data that gained mass, we belive that the rest of our data follows a pattern that allows us to believe that our data is accurate. The reason for the accuracy of our data is that we carried out our data samplings with careful precision.
Relation to other Groups
When approaching leaf decomposition we basically placed three different types of leaves in three different environments. By doing this we received good comprehensive results because each type of leaf followed the same decomposition pattern for the most part. For example, every type of leaf sampled in the pond lost a greater amount mass when compared to other leaves in other environments. By doing this with three types of leaves we received three times the amount of data. Now, in our minds, another question arouses. What factors contributed to the large amount of mass loss within the pond leaves.
We think that by collaborating with a couple of other groups we could possibly investigate our results a little more in depth. Through collaboration with the "acid freaks" and the limestone group we could find out if acid rain could possibly be a catalyst in leaf decomposition. And if it is a factor in leaf decomposition then how is acid rain effecting the ecosystem, for we all know leaf decomposition is a large part of the cycle.
There is another relation to our decomposed leaves in the pond. What is in the pond that caused their drastic decomposition? Now we would want to consult with the sedimentary people. If the leaf decomposition group hooked up with the sedimentary people then we could get some interesting conclusions drawn up as to what was expediting the decomposition process of pond leaves. Our group is very curious as to what sediments and microrganims coud be possible contributors to the decomposition process of pond leaves. I mean what is in that pond that is causing their rapid decomposition. After allis it even the sediments or could it be that the swan shit is serving as the catalyst for expediting the decomposition of pond leaves.
Another group that has expaned our horizons is the honey suckle group, our across the table rivals. This group sparked the idea that maybe we should have created one more environment type. It would have been cool if we had placed leaves in shaded environments and leaves in strictly sunlit environments. This would have gave us further insight as too what role the sun plays in leaf decomposition. And we could have had some interesting discussions and analysis's of what role the sun is playing in leaf decomposition and the growth of honey suckle because there is such a close relation between the two.
Suggestions for Further Investigation
If we were to have this same, exact, class next semester then, of course, we would want to have the Haysmeister as our fearless leader, but we would also like a chance to look into student generated labs a little more in depth. We realize that there are things that could be improved and expanded within our lab process and if given a chance here are a few of them.
First of all, our "rat trap" should have been constructed a little differently. It should have had three different compartments for each type of leaf and three compartments for each time interval that the leaves should be taken out. Instead ours just had three compartments for each type of leaf. We don't think that by reconstructing our "rat trap" we would have recieved different results, but it would have made it easier for us to get them out of the pond.
Another improvement that should have been made was that we should have created some type of device to suspend the "rat trap" from resting on the bottom of the pond. One side of our "rat trap" was resting on the pond floor and the caused our birch leaves to get smothered with swan shit. From our results it looks as though the swan shit didn't cause any of discrepencies within our data, but it was one of the grossest and worst smelling things we have ever layed our hands on. So in, further investigation, we would definitely like to keep our hands clean.
Also, if we were investigate this lab even further then we think that we should maybe add more criteria for evaluating the decomposition of leaves. We would probably want a detailed investigation of physical characteristics and how they relate to the loss of mass within that particular leaf. In accompany to this detailed investigation it would be a good idea to have photographs to show the decomposition process. We believe that by doing this we could learn a lot more about decomposition. Throughout this lab we realize that the decomposition process has to deeal with a lot more than just weight loss.
The Breakfast Club
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