Section 2.2: Creating a Timeline


Students will:

  • Collate findings to develop a community-specific timeline of significant events (i.e. a mining operation, insect outbreak) that may have impacted the environment.

Key Terms

Data / Dendrochronology

See content or Module Glossary for definitions

Constructing a Timeline

Once the research of the impacts is noted and confirmed by students, the information can be organized into a timeline of events. For example, if the research data shows there was a decrease in tree growth in 1965, it could be speculated that something happened in the community at that time. Was there a drought? An insect outbreak? Did a mining operation begin? Have students do some digging into the historical record of the community where the tree was sample from and construct a linear timeline like the one in Figure 2. More instructions can be found in our Creating a Timeline Lesson.

Figure 2 shows an example of a linear timeline used to display the environmental events impacting a tree.
Figure 2 shows an example of a linear timeline used to display the environmental events impacting a tree.

In order to effectively and efficiently analyze the data, the MAD Lab and the CLS need a linear timeline (additional example found in our Creating a Timeline Lesson as well as shown in Figure 3 and 4). We recognize that other cultures may represent time in a non-linear way and that is a great place to explore for different perspectives! For the scientific research aspect of TREE, we will need one linear timeline submitted; students can still construct a timeline that incorporates various perspectives of time. Encourage students to consult various resources to gather a holistic perspective. Additional ideas/resources, along with student worksheets, are found in our Creating a Timeline Lesson and other brainstorming sheets can be found in the Student Field Book but the majority of the instructions are in the lesson. Once students have completed the table, they can then compile that information in a timeline.

Remember that the timeline is required in order to complete the citizen science portion of the TREE program.

Creating a Timeline Lesson

Collect research on the various impacts on a tree and create a linear timeline. Lessons can be downloaded and adapted from the link:

Examples of Timelines

Yellowknife Example Timeline.jpg
Figure 3 shows an example of a well-done linear timeline of human impacts with resources cited. There is still more information that could be added to this timeline about environmental impacts such as insects or drought but this is a very good place to start. The online website Canada’s historical climate database ( has a lot of this information that can help construct your timeline. Be sure to check it out!

Townsville Example Timeline.jpg
Figure 4 shows an example of a not so good linear timeline with no resources cited. They are missing a lot of useful information and some of their descriptions are a bit vague. How would you change this timeline?

Submitting Your Timeline

After the students have gathered the samples and finished the linear timeline, pack up all your samples with the timeline and mail it back to the Research team. If students completed any non-linear timelines, the CLS Education Team would love to see them as well!

Once we receive the kit received, it will be time for the laboratories to get busy. Tree ring research, or dendrochronology, provides long-term records of past temperature, rainfall, fire, insect outbreaks, landslides, hurricanes, and ice storms. The data collected from this research will expose how the trembling aspen in your area have responded to environmental and human events. The data will then be aligned with the linear timeline and the elemental analysis from the CLS to gain a better understanding of the environmental changes in your forest (see Module 5 and Module 6 for more information). See Figure 5 as an example of how dendrochronology data and elemental analysis can tell the story of a tree’s life.

Figure 5 shows an example of the data your students can get from a tree core that has been analyzed by the MAD Lab and the CLS.
Figure 5 shows an example of the data your students can get from a tree core that has been analyzed by the MAD Lab and the CLS.

The top three graphs in Figure 5 show changes in 3 elements of interest while the bottom graph shows how the ring width changes over time, reflecting tree growth. By comparing the three graphs, students and researchers can make connections. Does the spike in tree ring width before 1995 have something to do with the slight increases in nickel and copper? What was happening in the community at this time? Why does zinc and copper continue to increase and the ring width decrease as the tree ages? The TREE program tries to suggest answer these questions.