a. Despite a few good rains caused by the recent tropical storm on the Eastern coast, Oxford, and all of its wildlife, is still suffering from an unusually dry summer. Looking around, it became quite obvious to us, at least visually, that the lack of precipitation was having some dramatic effects on the flora of the Western Campus. These perceived effects raised an interesting question, one that our group felt merited a scientific investigation. The purpose of our proposed study is to discover the effects of draught on the seasonal cycle of two species of trees on Western Campus. We believe, due to our preliminary observations, that the dry summer has increased the rate at which the leaves die and fall off of the trees. We hope to answer the question “Will more leaves fall, as a result of the draught, than in other years in which the yearly rainfall is higher, and more frequent?” We predict that this year’s draught will cause significant differences in the rate of leaf fall, as compared to these other years.
b. The decision process occurred one day in class while we were discussing many different types of experiments that could be used for the Student Generated Lab. Having no real interest in microorganisms, prayer, or sunspots, Dave and I set about to devise a study that interested us. Looking out the window and thinking about what we could study on Western, we were struck with the idea of studying Western’s most prominent inhabitants, the trees. Walking to and from class everyday, we had noticed an increased amount of leaves on the ground, dry and crunching under our feet in the middle of August. The walk to and from class also made it uncomfortably obvious to us that it was very hot, and that there wasn’t a lot of precipitation. Putting these factors together, we decided they were related, and proposed to study just how much these two things were related.
c. One of the main goals of this study is to produce an accurate account of the effects of draught on two species of trees on Western Campus so that the information will be available for future classes, who hopefully will continue this research in other years in which the average rainfall differs from this year. Other studies have been done on leaf fall, but none that focus specifically on the effects of draught. These labs have focused on discovering the factors that effect leaf fall2C including the soil, weather, and several others. Knowing already that the weather, and precipitation, have an effect on leaf fall, we want to set up a starting point for people to research just how much of an effect they have on trees. Essentially, we want to establish a base year for the future classes.
d. Many of us, whether from other students, faculty, parents, or the guides at Orientation or Visitation days, have heard about Miami’s reputation for having a beautiful fall season. This reputation, as well as the abundance of trees on Western Campus, makes the effect of draught on this seasonal show an interesting topic. Discovering why this summer is already bringing about the falling of the leaves, completely skipping the usually beautiful color change, should prove to be an interesting study. With our research, and the results of studies done in future years, the time and intensity of the fall color change might even be made predictable.
a. Previous year’s students have performed studies in which they tested several factors that effect leaf fall. Their research incorporated such factors as pH levels, soil content, weather, and temperature in their study. Our study will move away from the broad topic of what effects leaf fall, instead focusing specifically on the effect of precipitation, or the lack thereof. The Mowbray and Oosting study discussed the peak time for precipitation fall, stating that “The yearly precipitation fall has two peaks, one during winter (December through March) and one during summer (July and August.)” We assumed that the drought would continue since the peak precipitation fall was hardly nothing, however Oxford endured enough rain that we decided to shift the focus of our study.
b. Our research relates to the larger question of how the shift in weather patterns is detrimental to the ecosystem, specifically deciduous trees in Ohio. The amount of these types of trees in Oxford, and specifically on Western, make it exceedingly relevant to this class, as the trees are a major player in the Western environment. Hopefully this research on draught will be able to not only help predict the time and intensity of leaf fall, but may also be used in researching the effect of draught on food crops, so that the peak of the season and the best time to harvest may be predicted, preventing crops from dying from draught before they can be harvested.
3. Materials and Methods
Dave Wellspring’s Digital Camera
Tree Nets (originally designed to keep small birds from fruit trees)
Fingers and Toes (used for counting)
a. Our proposed plan for the class experiment will be a much different approach to recording data on leaf fall then is used on our original experiment. In our original experiment we collected both statistical and visual data for a four week period, focusing on two trees. Every Thursday pictures were taken, and very fine nets were set out underneath the test trees. These nets served the purpose of collecting any leaves that fell. The nets in our experiment paralleled the usefulness of the materials used in the study by Mitchell, Coley and Webb about litter fall. Pictures were taken again on Tuesdays, and the leaves that were trapped in the net were counted. Only leaves that belonged to the tree were counted. Rather than have the entire class try to count the leaves in the net, a job that one person can do, we decided to run a different experiment so that the class could get an idea of just how many leaves are on a tree, to put the numbers we found in our experiment in perspective. We will ask the class how they believe all the leaves on a tree can be counted, and when they come to the right conclusion of estimation, we will perform the exercise. They will be split into groups , each group asked to make counts of braches, as well as the amount of leaves on each branch. The data from each group will averaged, and the estimated leaf number calculated. We believe that this a statistically sound way to scale our original lab down to a one day class lab. We will be providing the material and background information, and simply asking the class to sort and analyze.
b. We believe that this will a statistically sound experiment, at least as sound as possible given the transient nature of leaves. We were once again guided by Nancy in our quest to determine a successful way to bring this experiment into the classroom for a day. She once again helped us to simplify our experiment. We will also make much use of the weather record of this area for the past several years, which will be collected from the National Weather Service.
1. The amount of people participating in the lab will be one of the biggest factors in keeping our methods from being biased. With several groups, each with many people in it, we will have enough numbers that we will be able to average the numbers together and get a fairly accurate estimate of the numbers we are looking for. The pure amount of people should provide a fail-safe against the fact that people cannot count.
2. We will be counting the leaves along with the class, that way we will be able to keep compare to the numbers they bring us. We will also be doing all the calculating, leaving only the simple task of counting to be messed up by the masses. Hopefully, by taking the harder part of the experiment and putting it solely in the trustworthy hands of a calculator wielding individual. This marvel of modern science should keep us from getting the wrong numbers. The estimation of the numbers that the class will give us will also help, because one off number should not effect the overall estimate by too much.
c. Our most important materials will be the trees, Dave’s camera, and the class, at least for when we do the in-class activity. The camera will be used to keep a visual recording of the information that we will hopefully show in our data. The trees will be one of the most important resources, as it is the trees that will provide the leaves, which is the whole point of our project. They will also prove to be the source for our student activity, as they will have to actually observe the trees to make the estimates we require.
d. We could come up with no other solution as to how to bring our lab into the classroom except this one. This way, although signifigantly different than our original experiment, carries the essence of what we are trying to do, and thus conveys the importance and effectiveness of our efforts to the class. This will allow the students to draw their own conclusions regarding the amounts of leaves on a tree, and what our numbers reflected about the percentage of leaves that had fallen. They will have to make no direct analysis, but will hopefully draw their own conclusions about the project.
e. For our data sheets, we will be using a simple graph, as our numbers need know real graphs or charts to show the data. Simply setting up columns with numbers and dates, as well as divided by the type of trees. None of this requires extensive graphing or data analysis programs. The data sheet will appear in the results section.
f. October 3 – November 12
Thursdays: Take pictures, and clear the nets of residual leaves. Thursdays are the beginning day, the day that starts the four day collecting period.
Tuesdays: Once again, pictures will be taken to capture any change in the appearance of the trees. The leaves will be counted on this day, and the data recorded.
In Class Lab Day: We will introduce our project to the class at the beginning of the period, after which we will ask them to follow us outside and count leaves. This will not take very long at all.
4 Unfortunately, Oxford’s dry season seemed to end shortly after our decision to study it, so very little of our data actually reflects the drought. Instead, it now reflects the difference in leaf fall between species, one species having been around for millions of years. We noticed that the Ginko kept its leaves for a much longer period of time compared to the Tulip tree, or even the other trees around it. We also, as expected, that the later it got in the season, as well as the colder it got, the more leaves that fell from both trees.
Day Ginko Tulip
Oct. 8 5 276
Oct. 15 7 235
Oct. 22 9 192
Oct. 29 127 135
Nov. 5 310 110
Nov. 12 0 (all off) 96
b. Our data is a simple comparison between the leaf fall of the two trees; therefore, complex statistics will not be of much use. Our discussion will not require any numbers or comparisons that can not be seen with our table above.
c. The best display of our findings are through visuals. We took pictures every week and comparing the tree’s state of leaf fall clearly shows difference in the number of leaves remaining. The sudden fall of leaves in the Ginko tree is best expressed through the graph but easily can be visualized through the pictures. We will take four of each tree and compare them week by week. The simplicity of our results is be best presented with a combination of our table above with pictures to show the progress of the leaf fall.
a. Our prior research on the Ginko tree warned us of the sudden, rapid leaf fall. As this is exactly what happened, we were not surprised with the sudden jump in the rate falling. We also knew that the leaf fall would happen much later in the season than that of other trees, as the Ginko has adapted over the years to keep its source of energies (i.e. the photosynthetic processes in the leaves) for as long as possible. Without the drought, the Tulip tree behaved much the way that other trees behave, its leaves falling throughout the season after considerable color change. The fall of leaves was hastened by the cold weather, and the first frost, which was also expected. We can also assume from our observations that our first hypothesis was correct, despite the fact that the drought never happened. This can be inferred from the fact that the rain brought color back into the leaves on the trees, and that the leaf fall that was already occurring in early fall was halted by the return of precipitation to the Oxford region.
b. As we said before, very little has been done specifically concerning the effects of moisture on trees, at least in Western college classes. However, our information fits well with the general beliefs about the effect of rain on plants, conclusions that have been drawn since the beginning of time by any crop growing society. If it is dry, there will be no growth. This can be backed up by just about any long term study of plant growth. Observations of deserts and rainforests, and comparisons between their annual growths and rainfalls, also back up this conclusion. Additional questions, however, remain. These include just how much faster the leaf fall process would have occurred if Oxford had stayed dry, as well as what overly large amounts of precipitation, with less sun exposure, might have done. All of these could be answered with further study into the leaf fall.
c. We suggest studying several other factors besides precipitation, including exposure to the sun, and surrounding vegetation, which may have several other effects on the trees. This idea is also demonstrated in the study and analysis by Lechowicz about leaf emergence in the spring. Also, species that are more similar in nature may want to be included in the study, instead of two distinctly different trees.
a.Leaf Litter Production by Lianes and Trees in a Sub-Tropical Australian Rain Forest
Elwyn E. Hegarty
Journal of Tropical Ecology, Vol. 7, No. 2. (May, 1991), pp. 201-214.
b. Litter Fall in a New South Wales Conifer Forest: A Multivariate Comparison of Plant Nutrient Element Status and Return in Four Species
A. V. Spain
Journal of Applied Ecology, Vol. 10, No. 2. (Aug., 1973), pp. 527-556.
c. Vegetation Gradients in Relation to Environment and Phenology in a Southern Blue Ridge Gorge
Thomas B. Mowbray, Henry J. Oosting
Ecological Monographs, Vol. 38, No. 4. (Autumn, 1968), pp. 309-344.
d. Litterfall and Decomposition Processes in the Coastal Fynbos Vegetation, South-Western Cape, South Africa
D. T. Mitchell, P. G. F. Coley, S. Webb, N. Allsopp
Journal of Ecology, Vol. 74, No. 4. (Dec., 1986), pp. 977-993.
e. Why Do Temperate Deciduous Trees Leaf Out at Different Times? Adaptation and Ecology of Forest Communities
Martin J. Lechowicz
American Naturalist, Vol. 124, No. 6. (Dec., 1984), pp. 821-842.
Return to the Topic Menu or the Course Syllabus.
IMPORTANT: For each Response, make sure the title of the response is different than previous titles shown above!
DOWNLOAD the Paper Posting HTML Formating HELP SHEET!
We also have a GUIDE for depositing articles, images, data, etc in your research folders.
WEATHER & EARTH SCIENCE RESOURCES
OTHER ACADEMIC COURSES, STUDENT RESEARCH, OTHER STUFF
TEACHING TOOLS & OTHER STUFF