How to weigh a tree

Overview / Objectives

Overview

In this lesson students pick a tree they see everyday, perhaps one at school. They measure the tree's circumference and estimate its height using similar triangles. Using that information and the type of tree they calculate the tree's weight and the CO2 sequestered in the tree. They relate the sequestered CO2 to the CO2 produced by their families and the school.

The material for this lesson is presented two ways. There is a sample lesson which your students can use online. You can also follow the lessons via class discussions. This allows individualization by you and your students. The second approach is a collection of the models and data used in the lesson. You can pick and choose from these tools and other material you find to design your own lesson.

Depending on the time you can commit to this activity, you can either help the students work through the algorithm used to calculate the carbon in your tree or you can move straight to the completed model. The computational science skills involved in this lesson involve learning how to use computer models and evaluating their output.

A note on the formulas used to calculate the carbon in your tree. I am using formulas derived by foresters to estimate the weight of classes of trees in the forests of the southeastern U.S. Similar studies and formulas are available for trees in different sections of the U.S. and, I assume, the world. These formulas are used extensively by the forestry industry to plan where and when to harvest their forests. The formulas are a best fit for the data and as such more of an estimate rather than an exact value. I contacted my county extension agent to get the formulas. He didn't know the formulas but he forwarded my request to foresters in my state who were eager to help me. Most of the trees in the studies were in stands of trees, not an isolated tree in a grassy field.

This lesson leads into a second lesson that looks at the "Carbon Sequestration by Forest" over time. This is provided by a professional model, built by a team of Dutch scientists at the Wageningen University and Research Center, Silviculture and Forest Ecology Group.

I have provided an answer key to my lessons. The student questions are in red and suggested answers are blue.

Objectives

The students will gain an appreciation of their dynamic interaction in the carbon cycle. They will learn the role of trees in counterbalancing the CO2 that people produce.

This lesson will introduce the students to Computational Science. They will use computers and calculators to compute values that will help them understand the science of the carbon cycle. Computational Science is a powerful new way to do science.

National standards addressed:

Science

THE INTERDEPENDENCE OF ORGANISMS

-The atoms and molecules on the earth cycle among the living and nonliving components of the biosphere.

-Living organisms have the capacity to produce populations of infinite size, but environments and resources are finite. This fundamental tension has profound effects on the interactions between organisms.

-Human beings live within the world's ecosystems. Increasingly, humans modify ecosystems as a result of population growth, technology, and consumption. Human destruction of habitats through direct harvesting, pollution, atmospheric changes, and other factors is threatening current global stability, and if not addressed, ecosystems will be irreversibly affected.

MATTER, ENERGY, AND ORGANIZATION IN LIVING SYSTEMS

-The complexity and organization of organisms accommodates the need for obtaining, transforming, transporting, releasing, and eliminating the matter and energy used to sustain the organism.

-As matter and energy flow through different levels of organization of living systems--cells, organs, organisms, communities--and between living systems and the physical environment, chemical elements are recombined in different ways. Each recombination results in storage and dissipation of energy into the environment as heat. Matter and energy are conserved in each change.

NATURAL RESOURCES

-Human populations use resources in the environment in order to maintain and improve their existence. Natural resources have been and will continue to be used to maintain human populations.

-The earth does not have infinite resources; increasing human consumption places severe stress on the natural processes that renew some resources and it depletes those resources that cannot be renewed.

ENVIRONMENTAL QUALITY

-Natural ecosystems provide an array of basic processes that affect humans. Those processes include maintenance of the quality of the atmosphere, generation of soils, control of the hydrologic cycle, disposal of wastes, and recycling of nutrients. Humans are changing many of these basic processes, and the changes may be detrimental to humans.

-Materials from human societies affect both physical and chemical cycles of the earth.

-Many factors influence environmental quality. Factors that students might investigate include population growth, resource use, population distribution, over consumption, the capacity of technology to solve problems, poverty, the role of economic, political, and religious views, and different ways humans view the earth.

National Science Standards were taken from: http://www.nap.edu/html/nses/html/

Mathematics

Formulate Questions that can be addressed with data and collect, organize, and display relevant data to answer them.

Use Visualization, spatial reasoning, and geometric modeling to solve problems.

Use geometric models to gain insights into, and answer questions in, other areas of mathematics;

Use geometric ideas to solve problems in, and gain insights into, other disciplines and other areas of interest such as art and architecture.

Understand Measurable Attributes of objects and the units, systems, and processes of measurement.

Make decisions about units and scales that are appropriate for problem situations involving measurement.

National Mathematics Standards were taken from: http://standards.nctm.org/document/chapter7/index.htm

You may find it useful to open the student version of:

How to weigh a tree

in a separate window. This will allow you to toggle between the teacher discussions and the student lesson.