Online labs to introduce undergraduate students to scientific concepts and practices in tree-ring research

Figures & data

Table 1. TREX labs and the classes that they were tested in, number of instructors, number of students, type of evaluation/feedback method, and type of instructor feedback.

	Undergraduate class	# of instructors	# of students	Type of student evaluation/feedback method	Type of instructor feedback
Lab 1 & 2 combo	Intro to Sustainability (Four sections)	2	16, 22, 15, 18	Lab grades, student surveys, class discussion	Instructor survey and Informal discussion
Lab 1	Fundamentals of Earth Science (Section 1)	1	18	Lab grades, student surveys, class discussion	Instructor survey and Informal discussion
Lab 2	Fundamentals of Earth Science (Section 2)	1	9	Lab grades, student surveys, class discussion	Instructor survey and Informal discussion
Lab 3	Weekend Field Course	2	33	Student surveys & informal discussions	Instructor survey
Lab 4	Hydrology	1	18	Informal discussions	Informal discussion
Lab 5	Weekend Field Course	(same instructors as Lab 3)	(same students as Lab 3)	Student surveys & informal discussions	Instructor survey
	Global Climate Change	1	20	Informal discussions	Informal discussion

Figure 1. (a) Students learn to date and measure tree rings using a high-resolution scan of an original juniper sample from a pilaster at Pueblo Bonito, Chaco Canyon, New Mexico, that was collected in 1922 by A.E. Douglass and Neil Judd. Students are guided to develop their own “skeleton plot” (b) and compare it to the one pictured here to see if they can determine the year the tree was felled to build the pueblo.

Figure 2. A screen capture showing how student measure annual ring width from a high-resolution scan using ImageJ software. The yellow line shows the measurement of one annual ring, in this case the year 2002. The results tab shows measurements from three rings, starting with the ring with three dots on it, an indicator of a century ring, in this case the year 2000.

Table 2. TREX labs, key questions addressed, datasets/multimedia used in each lab, and student tasks (Reproduced with permission from Davi et al., 2019).

TREX Labs:	Key Questions:	Datasets, Software, Platforms, and Media:	Student Tasks:
Lab 1. Launching an Expedition: Introduction to dendrochronology and the nature of science. Time required: 90 minutes.	How do scientists take tree-core samples? What site characteristics are important for tree-ring studies? How do scientists get funding for research? How do scientists learn about what has already been done?	Virtual 360° field exploration ITRDB Google Scholar Scientist interviews NSF Research News Animation: Identifying Climate Sensitive Trees Video(s): Historical video	Virtually explore and describe sites Watch interviews Explore NSF website Search the ITRDB
Lab 2. Humpty Dumpty and Drought in the Hudson Valley: Focuses on a premier climate-sensitive site in the US Northeast and on how scientists use tree rings to developed a drought record of the region. Time required: 180 minutes.	What site characteristics are important for tree-ring studies? Why are some trees more sensitive to climate than others? How do you take tree-core samples? Why are some rings narrow? Do trees record climate?	Virtual 360° field exploration Video(s): Scientist interviews Video(s): Tree sampling High-resolution scans of tree cores from the site Meteorological databank (PDSI, KNMI Climate Explorer)	Virtually explore and describe sites Identify narrow rings Find online meteorological data Compare ring patterns to meteorological data Meet the Challenge
Lab 3. Tree Rings and the Ancestral People of Pueblo Bonito: Focuses on the history of dendrochronology and how scientists calendar date historic structures. Time required: 180 minutes.	What site characteristics are important for tree-ring studies? How do scientists assign exact calendar dates to tree-ring samples and historical structures? How might have drought affected the ancient Puebloan people? How could a drought affect your life?	Virtual 360° field exploration Video(s): History of dendrochronology High-resolution scans of tree samples. NIH ImageJ software and tutorial Drought reconstruction interactive	Virtually explore and describe sites Skeleton plot Compare plots to historical work Determine tree felling year Measure tree rings Evaluate drought reconstructions Graphing
Lab 4. Sharing a River: The Colorado River Story: Stresses the importance of the Colorado River as a resource and how tree-ring data informs water resource management. Time required: 180 minutes.	Who are entitlement holders and how is the Colorado River used? What site characteristics are important for tree-ring studies? How are tree rings used to reconstruct drought? What information can we learn from tree rings about streamflow? How do we better manage water resources?	Virtual 360° field exploration Video: Colorado River Map interactives Digital scans of tree cores NIH ImageJ software and tutorial National Weather Service drought maps Reconstruction Interactive	Virtually explore and describe sites Evaluate current drought maps Compare supply/ demand data, snowmelt/streamflow Measure samples Compare work to published datasets Evaluate streamflow reconstruction
Lab 5. Warming and the Boreal Forests: Students learn how tree-ring records are used to develop a temperature reconstruction, evaluate trends, and relate extreme years to major volcanic events. Time required: 180 minutes.	What are the boreal forests? What site characteristics are important for tree-ring studies? How do you find previously published data and related science literature? How do scientists develop long tree-ring records? What do tree rings in the northern hemisphere tell us about climate? What role can serendipity play in science? Can large-scale volcanic events affect climate?	Virtual 360° field exploration ITRDB Google Scholar Animation: Identifying Climate Sensitive Trees Video(s): Interview Video (s): History of Dendrochronology High-resolution scans of tree cores NIH ImageJ software and tutorial Temperature reconstruction interactive	Explore the ITRDB Research: peer-reviewed articles Virtually explore and describe sites Measure tree samples Compare measurements to published data Evaluate interactive temperature reconstruction Identify short and long-term trends Identify extreme years. Research volcanic events

Table 3. Selected “Stop and Think” questions, aligned to the learning goals, that are embedded within each lab.

Lab 1 Launching and Expedition	What types of trees and tree-ring sites are the most useful for tree-ring research? Why are trees growing in landscaped areas not useful to study past climate conditions? What is the dominant limiting factor to tree growth at high altitudes? How close is the nearest tree-ring research site from where you live?
Lab 2 Humpty Dumpty and Drought in the Hudson Valley, NY	Why are the trees on the talus slope ideal for use in tree-ring research? Which years consistently stand out for being very narrow or wide compared to their neighbors? Describe any similarities you see between the data you graphed in Climate Explorer and the tree-ring "marker years" that you identified in Part 2.
Lab 3 Tree Rings and the Ancestral People of Pueblo Bonito, NM	Describe the site based on your observations. Be sure to emphasize the types of vegetation you see (how many different types of trees, shrubs), the density of that vegetation, the soil or lack of soil, the presence or absence of water, and any other characteristics you may observe. Post a screen capture image of a wood sample that you found inside the Pueblo that you believe would be suitable for further research. How do megadroughts of the past compare to droughts that have occurred in the past 100 years? Given what you have learned about drought through time based on tree rings, would it change your mind about living in that region? If you were a water manager for New Mexico, how would this data affect your thinking about managing water?
Lab 4 Sharing a River: The Colorado River Story	What three years had the lowest flow volume in the Colorado River? What was the difference between water used and the total water available in 2002? Give two reasons that you think would account for the rising demand for water in the Colorado River Basin. Do you see similarities in tree growth compared with the stream flow records at both locations? Do narrow rings match up with low flow years?
Lab 5 Warming and the Boreal Forests	Describe the nature of the forest along the East Glacial Trail. Are the forests diverse? Are there shrubs and other plants? Is there a lot of soil that you can see? Do you see mostly broad leaf deciduous trees, or conifers? Describe the site conditions and forests you see in the two 360° images from Mongolia. How does this Mongolian forest differ from the one you looked at near the Mendenhall Glacier in Alaska? Compare the graph of your sample to the related master tree-ring chronologies above. Does the data from the core/cores that you measured look similar to the related master chronology from the same region? Why/why not? Looking at the master chronologies above, describe the patterns that you see. What are the extreme narrow (reflecting cold) and extreme wide (reflecting warm) years? List five periods of 5-10 years in duration that were unusually warm or cold over the past 1000 years.

Table 4. The survey given to faculty prior to classroom testing, and during the faculty workshop.

a. Was the point of the lab clear? Were the tasks and instructions clear? If not, what problems did you see? Any suggestions for improvement?

b. Were the Stop and Think questions appropriate? Did the material support them?

c. Were the materials comprehensibly written? Any suggestions for improvement?

d. Are the directions for the technology components included in the lab adequately outlined for students?

e. If you were to use this lab in your class, do you think it would be engaging and interesting to your students?

f. If you were to use this lab in your class, do you think it would be challenging? Too easy?

g. What difficulties might you anticipate for yourself or your students?

h. How many class sessions or hours do you estimate this lab would take in your class?

i. Does the sequence of activities flow coherently from activity to activity?

j. Do you have any suggestions of additional learning experiences to include in the sequence? Should any parts of the existing activities be deleted?

k. 4. Other suggestions or comments on lab structure, format, or content?

Figure 3. Stop and Think question grades for Fundamentals of Earth Science (FES) TREX Lab 1. (light blue, n = 18), Lab 2 (orange, n = 9), and for Introduction to Sustainability (SUS) using a combination of Lab 1 (Part 1) and Lab 2 (Part 1-3), Class 1 (grey, n = 16), Class 2 (yellow, n = 22), Class 3 (dark blue, n = 15), and Class 4 (green, n = 18).

Figure 4. Student survey results for; A. Intro to Sustainability based on a combination of Labs 1 and 2 (n = 71); B. Fundamentals of Earth Science, Lab 1 (n = 18); C. Fundamentals of Earth Science, Lab 2 (n = 9); and D. A combination of Lab 2 and 5 for a two-day field workshop for mixed-majors with two groups of students (n = 33 total).

Table 5. Summary of student feedback after completing the TREX Labs 1 and 2 in Fundamentals of Earth Science.

Main themes from student survey feedback
Difficulties:	Worked well:
using technology (e.g. Excel) more time needed not comfortable interpreting data intimidated by mapping intimidated by graphing navigating multiple screens at the same time prefer to work with the actual wood cores	virtual exploration video interviews introductory materials generating maps manipulating interactive graphs working on digital cores connecting annual tree growth to annual climate connecting climate to people

Davi, N., Pringle, P., Lockwood, J., Fiondella, F., & Oelkers, R. (2019). Tree-ring expeditions (TREX): Online labs that guide students to think like scientists. Tree-Ring Research, 75(2), 160–166. https://doi.org/https://doi.org/10.3959/1536-1098-75.2.160

 Web of Science ®Google Scholar