Every Tree Tells a Story



	Every Tree Tells a Story Naida Lefthand, Regina Sievert and Julie Cajune Flathead Indian Reservation, Pablo, MT
	Summary Students learn about tree growth and investigate environmental factors that affect it. Grade level Second Time required 90 minutes, plus a fieldtrip Materials Tree rounds from a variety of trees Magnifying glasses Rulers Science journals Precipitation data for the last ten years Graph paper Goals By completing this lesson, students will learn about the parts of a tree and how trees grow, discover how environmental conditions can affect the growth of a tree and gain experience in using the process skills in an investigation. Science standards addressed National Science Standards Abilities necessary to do scientific inquiry Constancy, change and measurement Organisms and environments Changes in Earth and sky Science and technology in local challenges American Indian Science Standards Plant and animal life cycles as exemplified in traditional American Indian concepts such as the Medicine Wheel Various forms of scientific and technological work currently engaged in by American Indian men and women and in what ways their fields require the process of problem identification, design and solution Changes in Earth's surface, weather fluctuations and movements of celestial objects and how they affected historical American Indian community locations, annual migrations, and agricultural and ceremonial cycles. Teacher tips Obtain tree rounds (cross sections of trees) that students can examine. The Tribal Forestry Department can assist in obtaining rounds that illustrate the variation in growth due to environmental conditions such as drought, injury, disease, excessive precipitation, and fire. By using recently cut trees, you can talk to students about environmental conditions for the last few years that they might remember and that would show up in the tree rings. Encourage students to examine the rings with magnifying glasses and to measure the difference in ring size with rulers. The CSKT Natural Resources Department keeps records of average precipitation for the Flathead Reservation. Contact them to get precipitation numbers for the last ten years. Background information Tree trunks gain width by the addition of annual rings of cells produced in the cambium layer. The cambium layer is found just below the phloem, which is just beneath the bark. The annual ring can actually look like two rings, a lighter one and a darker one. The lighter ring is usually added during the wetter spring months when the tree is growing more rapidly, and so is wider than the darker part of the ring. The darker part of the ring contains smaller cells packed more closely together, that are added during the drier summer months when the tree is growing more slowly. The age of a tree in years can be determined by counting the rings of lighter and darker cells and dividing the total by two. The annual rings can also indicate the environmental history of an area. For example, during poorer growing conditions such as drought years, trees grow more slowly due to lack of moisture, thus rings are smaller in width. Sunlight and temperature are other factors that can affect growth rate and ring width. Trees on north facing slopes, for example, get less sunlight relative to those on south facing slopes, and so their rings tend to be narrower. Scars in the rings may indicate injury due to fire, insects, or mechanical trauma. Unusual colors may indicate that fungus was living on the tree. Procedure Engagement Facilitate a class discussion about how humans grow and what kinds of things can affect a child's growth. Discuss with students the growth of trees. Show a tree round and discuss the annual rings. Use the vocabulary words in context as you explain. Allow students to look at the rings as you walk around with the round. Ask them to note whether the rings all look the same. Ask them to predict what might cause variations in the rings. Exploration Provide student pairs with tree rounds, rulers and magnifying glasses. Allow them to explore the rounds for a few minutes. Ask students to draw their rounds in their science journals. Ask them to label annual ring, heartwood, cambium, and bark. Have them count the rings to age the tree. Ask them to write about and draw observations about the tree rings in their journals. Ask students to hypothesize about the life of the tree in terms of the environmental conditions that affected its growth, based on the appearance of the rings. Have them write their hypothesis in their journal. Explanation Ask student pairs to report their observations and hypotheses to the class. Create a chart of the environmental conditions that the students propose and how they can affect tree growth. Elaboration Have students make a graph of the annual average precipitation for the last ten years on the Flathead Reservation. Ask them to predict how they think the tree rings will look for those ten years. Then compare the appearance of the tree rings to the data and discuss. Invite a tribal forestry professional on a fieldtrip or for a classroom visit to talk with students about tree growth conditions. Ask them to discuss conditions specific to trees on the Flathead Reservation such as fire, needle rust, mistletoe and pine bark beetle, and how tribal forestry is managing the forests. A core sample could be taken and discussed. Evaluation Set up a performance based assessment for students as follows. Lay out a variety of tree rounds. Give students a list of conditions that fit the profiles of the annual rings found on the rounds, and ask them to match the specific round to the condition. Some example conditions might be: This tree was attacked by insects four years ago. It rained about five and seven inches every year for the last five years. For the five years before that, it rained between twenty and thirty inches each year. A fire occurred in this tree's home area three years ago. Review student journals for their observation, hypothesis formation and recording process skills, and for their correct use of vocabulary. Vocabulary cambium heartwood annual ring precipitation hypothesis