A wealth of information can be found encoded in the rings of trees. Tree rings tell us of past weather conditions, forest fires and even the dates of solar flares. Dendochronology, the study of tree rings, reconstructs past events and conditions by examining the traits of the annual growth rings, namely their width. Our group decided it would be interesting to do some dendochronology here on Western. Our question was, just what are the effects of annual rain fall and average temperatures on the growth on maple trees here on campus? Are there direct correlations between weather and growth? Does greater than average rain tend to stimulate growth or flood the roots? Is heat detrimental or beneficial for growth? Do freezing temperatures have a significant effect? To determine the answers to these questions, we will compare core samples we obtain with weather records over a twenty year time span.
We hypothesize that higher annual rain fall will result in more growth. Years with little rainfall will have minimal increases in tree diameter. Years with fewer days with freezing temperatures and days of extreme heat (above 95 degrees C) will result in the most growth. Warmer-than-average years will get more growth and cooler-than-average years will result in less growth. The most growth, then, will be found during warm, wet years.
This lab will be very informative as to the effects of weather on tree growth. After the completion of the lab, we will able to confidently state the effects of temperature and rain fall on tree growth, regardless if the data supports our hypothesis or not. Also, it will give us and the rest of the class hands-on experience with coring techniques and methods of measuring annual growth as they will be coring and collecting data in our class lab. Our group is steadily gaining knowledge about the process that forms tree rings and information that can be obtained from them.
Through our extensive research, our group was able to find three labs performed by other college students relating to our topic. Recently, another Miami student performed a similar study comparing the tree growth of white oak trees to the changing climate conditions over the past seventy years. He hypothesized that a lower than normal precipitation and excessively low temperatures would diminish tree growth. Because his lab is very similar to ours, we will use it as an example of both the effective and ineffective approaches to performing the experiment (Seiler). Similarly, a group of students at Penn State University completed a lab centered around core samples. They were attempting to observe how the trees in their area were affected by a fire that occurred a few years before. The students wanted to see if the rings would show evidence of the fire. To do this, they used the same techniques we will be using to core the trees. For this reason, we will use this lab as a reference on how we will obtain our data on the environmental factors influencing tree growth (Taylor). The third lab we were able to find was performed by a group of New England students that also studied core samples. In their lab, they analyzed the effects that environmental events have on tree growth. This is another source of comparison we can use for our lab. We can analyze their procedure in order to improve ours (Benjamin).
Our group came across an interesting article about a study done on tree rings in Siberia titled, "Long-term Temperature Trends and Tree Growth in the Taymire". In this study, experimenters deduced that in recent years there had been greater trends in tree growth during the warmest seasons. After extensive research, they were able to determine that the trends in tree growth over the past thirty years differed considerably from those of recent years. From this data obtained by the experiment, the researchers were able to conclude that the greater tree growth in recent years can be attributed to global warming. This study is an example of the useful information that can be obtained by studying tree rings (Jacoby, Gordon, et al). "Wood Anatomy", a similar article we discovered on the topic of tree rings, discusses the various characteristics of trees and focuses on the different layers, such as the sapwood and the pith. Another topic in this article dealing with our lab is the use of tree rings to determine the affects of temperature on tree growth. We can use this as a basis for our analysis of the tree rings and the effects of weather on trees over time ("Wood Anatomy").
The last resource our group was able to find is a website devoted to dendrochronology. It is located on the University of Tennessee webpage. We can use this site to help us formulate and analyze data on the core samples. This useful website also gives us links to other web pages on the same topic if we should need any further information. If needed there are experts there we can contact for assistance (Grassino-Mayer, Henri D.).
III. Materials and Methods
We will be using a borer to obtain core samples from a group of maple trees behind Boyd Hall. These trees can be reached taking the service trail that cuts through the woods south of Boyd and taking a left at a pile of asphalt. These trees will be of roughly the same diameter and environment. We will take the samples and measure the annual growth. We will obtain weather records for over the past twenty year. The testing should be statistically sound because we are taking samples from trees of similar age and in similar situations cutting down on other factors. Unfortunately, we do not have enough time and people to take the number of samples needed to be completely statistically correct. We picked maple trees because they are abundant in this area. We are measuring the growth for the past twenty years because the more years we take data from the more accurate the trends we observe will be. We are limited by time for taking any more data than that. The data collected by students will be trustworthy because we will adequately demonstrate and explain coring methods and supervise them in the field. We will also assist them in the field.
The most important material will be the borer. This is how all of our samples will be obtained. We will also be using a dbh tape, a special measuring tape calibrated for measuring tree diameter. We will be using Stat View to create graphs of the data we collect for comparison purposes. We will research weather data from the internet. We will use this data to determine how the weather has affected the trees in the area we research.
The class will be taking an active role in helping us to collect this data. First, we will demonstrate how to successfully core a tree without causing harm to it. Then each group will be assigned a tree from which they will make their own core sample. Then they will measure the annual growth rings and record their data. The data will be turned into us for processing.
Timeline: During week nine we had the proper coring method demonstrated to us. We also checked out the borer that we and the class will be using. On week nine we will choose the trees we will test, measure the diameter of these trees and take our own core samples . On week ten we will measure the annual growth of these samples and record the data. We will also mark the trees to be used during the student lab. On week eleven the class will perform their lab. They take measurements and turn them in to us. Our project will be completed by week sixteen.
In summary, we will be taking core samples of maple tree of similar size and location. Some of these samples will be obtained by other students in our class as part of our student participation portion of our lab. These samples will be measured to find the annual growth. These figures will be compared to rain fall and temperature records from the past twenty years. We will be looking for a correlation between the growth of trees and the amount of rain and average temperature. We have hypothesized that there is a direct correlation between warm, wet weather and an increase in tree growth. We are looking forward to the lab and hope the rest of the class is, too.
Benjamin, Mike. Forests In Cross Section. New England, 1999.
Grassino-Mayer, Henri D. Ultimate Tree-Ring Web Page. www.web.utk.edu/~grissino/.
August 26, 2000.
Jacoby, Gordon, et al. "Long-term Temperature Trends and Tree Growth in the Taymire Region of Northern Siberia." Quarternary Research July 1999: 312-318.
Seiler, Shawn. The Effect of Climate on White Oak Trees in Oxford, Ohio. http://jrscience.wcp.miamioh.edu/courses/climate405-501.html
Taylor, Alan H. Research at the Penn State Tree Ring Lab. www.geog.psu.edu/tree/research.html. Penn State University, 9-7-00.
"Wood Anatomy" Agriculture, Forestry, and Soils: Forestry Biological and Biomedical Science:
Plant Science: Plant Anatomy and Morphology. 4 Sept. 2000
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