Lab 5: Campus Trees Phenology Project

Transcription

1 Lab 5: Campus Trees Phenology Project The Maples at Oak Ridge Researchers at Oak Ridge National Laboratory have been working to better understand and predict the consequences of climate change on organisms and the ecosystems in which they interact. Their work has shown that some trees, including maples, respond to climate change conditions (warmer temperatures and higher CO 2 concentrations) by delaying leaf color change and abscission (leaf fall; Norby et al., 2000). In Tennessee, these findings were interpreted as great news. Color tours of the Great Smoky Mountains are a huge component of the tourism industry for the state and longer autumn seasons mean more tourists and more money! The maple syrup industry was similarly intrigued a longer growing season means more time for the trees to make and store sugar. A larger store of sugar means more syrup available to harvest the following spring. However, economy does not always correlate with ecology. The research also showed that when the leaves grown at higher CO 2 and temperature did eventually fall, they were more likely to be green when they fell compared to leaves grown under control conditions. In order to understand the relevance of green leaves falling from trees, it is important to know that as leaves change color during autumn, they are actively moving valuable nutrients (e.g., nitrogen in chlorophyll) back into the stem of the tree for storage over winter. As the green chlorophyll pigments are broken down in order to move these nutrients, the yellow and red pigments that were always present in the leaves become more visible. If leaves fall while still green, those valuable nutrients fall back to the ground and are lost to the plant. What effect do you think this might have on the trees in the following spring and summer? Might there be consequences for the animals that rely on the trees for food? What impact might the high nitrogen leaves have on the bacteria and fungi that decompose the fallen leaves? Phenology The study of the timing of recurring biological events, along with the causes and consequences of these events, is known as phenology. In Michigan, many phenological events are an ordinary part of our seasonal landscape. For example, the appearance of wildflowers and mushrooms each spring, the emergence of mosquitoes each summer, bird and butterfly migrations in spring and fall, the ripening of apples, peaches, and cherries in summer, and the dormancy and hibernation of animals in winter. Many phenological events are tied to environmental cues, such as changes in temperature or day length. The Intergovernmental Panel on Climate Change (IPCC) has identified phenology as a critical area for research aimed at better understanding the impacts of climate change on organisms and ecosystems. The consequences of change in the timing of phenologic events are generally not isolated to individual organisms, but instead, may trigger cascades of events in which other organisms and entire systems may be affected. Databases and long term records as tools in the study of science Many biological questions, including how do phenological patterns of trees change over time? require significant time to answer much longer than we have in a single semester. Studies directed at measuring and documenting patterns in nature were significant in the emergence of biology as a scientific discipline. For example, Darwin s insights about evolutionary processes and Mendel s contributions to our understanding of inheritance both followed years of nearly obsessive documentation of patterns they observed in nature. Long term observational records remain critical in the study of some of biology s most significant questions. As a result of the long term atmospheric sampling efforts at Mauna Loa, HI, and other locations, climate change trends can now be mapped against very precise records of CO 2 concentration. Even at MSU, a seed viability experiment initiated in 1879 by Dr. W. J. Beal continues today! 1

2 What you will do: In this lab, you will work with your lab team to: 1) collect data about tree size (size correlates with growth) for 3 trees on campus 2) enter your data (dbh and height) into a lon capa database for permanent record 3) observe your assigned trees for the remainder of the semester and document the dates of spring phenologic events (budburst, full leaf, first flower) 3) discuss questions you have about factors that might contribute to variation in phenologic events, such as bud break 4) work with your class to design a project related to phenology and strategize about how you will collect data that addresses that question. Project Objectives For this study, we will be focusing our attention on leaf color change and leaf fall in autumn; bud break and leaf/flower emergence in spring. As a result of participating in this lab activity, you will: 1) practice the process of the scientific method as it applies to the study of phenology, including: a. observe variation in a natural system b. develop methods for quantifying and documenting patterns in phenologic events c. collect, analyze, and interpret data d. communicate your findings in written and oral forms 2) contribute to a long term database documenting phenological patterns for local campus trees. Your observations allow future students and researchers to investigate phenological patterns in local campus trees resulting from: microclimate variability (e.g., proximity to campus buildings) seasonal/annual variation in climatic or other variables (e.g., temperature, precipitation, pests and pathogens) differences among species or groups of species (e.g., maples vs. oaks; introduced vs. native species, etc.) differences in age and/or growth rates of trees (e.g., young vs. old trees; rapidly growing vs. slower growing trees) human activities (e.g., campus construction projects, landscaping activities such as fertilizer/pesticide application, mulching, pruning, etc.) Methods Part 1. Collect data (record in the Raw Data, Field Notes, and Observations section of your post lab) by locating and documenting initial measurements of height and dbh for your study subjects. A. Locate the 3 campus trees that your team will study. Your TA will provide you with a map, tree ID numbers, and other instructions to help you locate your tree. Record information that will help you find your trees again in the future and communicate their location to others. B. Measure the height of each tree in meters. A detailed method for estimating tree height using a clinometer is included at the end of this lab (appendix A). Repeat your measurement of height at least 3 times from different locations/angles or by different team members to obtain your best estimate. Record ALL your raw data, including calculations! C. Measure the diameter at breast height (dbh) for each tree (in meters). A detailed method for estimating dbh is included at the end of this lab (appendix B). Repeat your measurement of circumference at least 3 times to obtain your best estimate. Record ALL your raw data, including calculations! 2

3 Part 2. Summarize your data (include in the Data Analysis and Results section of your postlab) Organize your quantitative raw data into tables and calculate means for height and dbh. Be sure to include appropriate titles for each table and clearly label all columns and rows to indicate the types of data included in the cells. Your calculated means represent your best estimate of height and dbh. Be sure that both measures are calculated in meters. Part 3. Enter your data into lon capa. Browse to: Log in using your MSUNet ID. If prompted, enter the course, BS110, Spring 2009 BS110 Lab A screen will appear titled, Course Actions. Click on Navigate Contents in the menu bar at the top of the screen. Enter your dbh and height data for each of your 3 trees. The value you enter must be measure in METERS and should be your best estimate of that measure. If you repeated the measure 6 times, then the value you enter should be the mean of those 6 measures. Part 4. Discuss ideas and questions about phenology with your group. Use your discussion to begin the process of deciding what project your lab section will work on for the semester. Use the following questions to start your thinking about phenology. Discuss your ideas with your group members, but record your responses to the questions individually. Your responses will constitute the Conclusions and Reflections section of this postlab. 1. Brainstorm with your team members to provide other examples of phenological changes that you have or will witness as residents of Michigan. 2. For each of the cases below, what other organisms, or groups of organisms, could potentially be impacted by the following phenological changes? In each case, describe a mechanism that explains how the phenological change impacts other organisms. a) An unusually early frost in mid September causes the leaves of maple trees to fall while they are still green. b) An exceptionally warm period in late January causes bud break and flowering in fruit trees (cherries, apples, peaches). The warm period is followed by two weeks of sub zero temperatures in February. c) Severe summer drought causes a 3 4 week delay in the maturation rate of corn. d) Extended cold weather in spring causes honeybees to remain dormant a month longer than usual. 3. List 3 experimental questions you might be interested in investigating related to spring phenology in the context of this project. Briefly (in a sentence or 2) describe the methods you would use for each of these studies. 3

4 Post Lab Arrange your data, analyses and conclusions using the following headers and respective items under each heading. A. Raw Data, field notes and Observations (3 pts) Include all your raw measures for dbh and height, including variables needed for the calculations (angles of inclination, height of person measuring, distance to tree, all replicates, etc). Show your work for calculations. B. Data Analysis and Results (3 pts) Organize your raw data into tables that also shows your summary measures (e.g., mean, standard deviation, etc.). Be sure to include all appropriate titles and legends for your tables. C. Conclusions and Interpretations (6 pts) Work with your group to discuss the questions in part 4 of the lab. Write your own answers to the questions individually. *Please visit the website and view the post lab rubric for this lab. 4

5 Appendix A. Estimating Heights of Trees Using a Clinometer Using a clinometer. A clinometer is a tool that is used to measure angles. Forestry suppliers sell specialized clinometers for accurately measuring heights of trees, however a simpler (and much cheaper) version can be constructed using a protractor, straw, and string. Loop a 6 to12 inch piece of string through the hole in a standard protractor. Attach a weight to the free end of string (the weight holds the line plumb to form a straight line). Tape a plastic straw onto the protractor through the 90 horizontal, as shown. Sight the top of the distant object (tree) through the straw, keeping the junction of string and straw at eye level. Measure the angle of inclination (elevation) by reading the intersection of the string on the protractor. 5

6 Calculate height. The angle of elevation is the angle formed between two lines: 1) your sightline that runs from your eye to the top of the tree and, 2) a line that runs parallel to the ground at your eye s height. Recall from your trigonometry class that: tangent of angle (θ) = length of side opposite the angle/ length of side adjacent to angle. Here, θ is the angle of elevation you measured with the protractor. Therefore, Tangent θ = height of tree/distance between you and tree Solving for height of tree, Height of tree = [tangent θ][distance between you and tree] This would be perfect if you actually measured the angle of elevation from the ground. However, recall that your measurement was taken at the height of your eye, not at ground level. To adjust for this, you will need to add the height of your eye to your estimate of tree height. Height of tree = [tangent θ][distance between you and tree] + height of your eye Note: keep all your measurements in the same units (m, ft, inches, etc.) 5.2 ft is not the same as 5 ft 2 in! Table of Angles and Their Tangents Angle Tangent Angle Tangent Angle Tangent

7 Appendix B. Estimating Diameter at Breast Height Diameter at Breast Height, or dbh, is a standard measure taken by foresters, land managers, and timber industries. In conjunction with other species specific information, dbh can be used to estimate tree age and growth rates. Foresters standardize the measurement of dbh by measuring the circumference of trees at 1.3 m from ground level. If the surface of the ground is uneven, take the highest average point at the base of the tree as your ground level. At 1.3 m from ground level, measure the circumference of your tree with a flexible tape measure be sure to keep the tape level at all points around the tree trunk. Use your measure of circumference (and memory of math!) to estimate diameter: Recall, circumference = 2πr, where r = radius, and diameter (d) = 2r. Therefore, circumference = πd. Solve for d: d = circumference/π 7