Learning to Read the More-than-Human Archives: Dendrochronology and “Talkative Trees”

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This is the third post in a five-part series showcasing the research coming out of three projects hosted at Nipissing University’s Centre for Understanding Semi-Peripheries (CUSP) and supported by Kirsten Greer, Canada Research Chair in Global Environmental Histories and Geographies of the Semi-Peripheries.

I am a dendrochronologist and paleoclimatologist in the Department of Geography at the University of Nevada, Reno. However, my journey to geography actually started in the Earth Sciences Department at Dalhousie University. That’s right, I’m actually a geologist by training. Not only that, but my Master’s degree from the University of Saskatchewan, and my PhD from the University of Arizona, are also in the Geosciences, not Geography.

“Talkative Trees” webpage of Empire, Trees, Climate module

So how did I get here and why am I writing about my research in a forum about environmental history? Well, I suppose you could consider paleoclimatologists a form of environmental historians, since we study what climate was like in the past and our work has formed the basis of many studies of environmental history. Moreover, paleoclimatologists study the past using various archives that we call proxies, and much of our work consists of figuring out what these various archives are telling us. For example, if one looks at our team’s Historical Geographic Information System (HGIS) on “Talkative Trees,” this terminology harkens back to the title of a 1929 article in National Geographic written by A.E. Douglass (the founder of dendrochronology as a discipline), in which he wrote about “Reading the diaries of trees.” To a dendrochronologist, a forest is an archive and we must learn how to understand the language.

A.E. Douglass (1929) “The secret of the Southwest solved by talkative tree rings” National Geographic Magazine 56(6): 736–770.

As a dendrochronologist, my chosen proxy is tree rings. However, I also use stable isotope geochemistry (another tool with wide applications). If I were to stretch to the limit my analogy comparing paleoclimatology to history, one could say that being a dendrochronologist means that tree-rings are my chosen archive and that stable isotope geochemistry is one of the “languages” that I read when looking at that archive. Because these are in essence both tools and archives, the sorts of questions I can apply them to are also quite broad.

I have studied tree rings and isotopes from sub-fossil wood from the Canadian Arctic in order to understand what ecosystems and climate were like 3.5-3.8 million years ago. I have studied spruce beetle outbreaks in Alaska, historic mercury pollution in Wyoming, and worked to reconstruct 400 years of storm track changes in western North America. However, I also work with environmental historians and historical geographers on questions that touch on the historical record. For example, I am collaborating with Dr. Scott Mensing (a paleoecologist) and Dr. Ned Schoolman (a historian) on a project to look at how climate and societal land use practices are reflected in lake sediments and historical records in northern Italy. As with a historian who can take their research skills to explore multiple topics, I am exploring how my tools can be used to tackle multiple issues. How did I get involved in a project looking at tracing the timber trade in the North Atlantic. Well, I can start that story in this way: “A dendrochronologist and a historical geographer walk into a bar…” At the time of this project’s inception, I was a professor at Nipissing University in Ontario, and Kirsten Greer had just been hired as a new Canada Research Chair. One of the advantages of working at a smaller institution like Nipissing is that it forces one to seek unlikely collaborations, because most departments are so small. This led to our hashing out an idea for this project. My role on this project was to use dendrochronological and isotopic techniques to determine where  timbers used in the construction of various buildings in Bermuda originally came from. Originally, we were also going to try to use these timbers to provide climatic information, however, many more samples would have been required to meet that final ambitious aim of our project than we were fully able to collect. I believe that even being able to clearly identify where the exact pieces of timber we sampled would have originally grown is quite the accomplishment. For more details see the “Talkative Trees” project webpage.

Dendochronology at the Dockyards

Although not originally part of the project, at the request of the National Museum of Bermuda, we were asked to determine if we could make a master chronology out of Bermuda cedar. The museum thought this would be helpful to them to assist in the dating of old buildings built of that wood. The Bermuda Department of Conservation Services was also interested in a chronology to determine the age of Bermuda cedar on the island. Bermuda cedar is an endangered species appearing on the International Union for the Conservation of Nature red list of endangered species, and no chronology had ever been made from this species.

Locations of the Bermuda Cedar samples marked by tree icons

For my part, I was a little skeptical as to whether this objective would meet with success. Bermuda is a semi-tropical locale, and so I didn’t know whether it even produced annual rings. Our budget was also unlikely to stretch to cover the sort of intra-annual stable isotope work that had been done on tropical trees elsewhere in the world, but I felt we owed it to our collaborators to give it a try. We collected living and dead Bermuda cedar cores from many parts of Bermuda and obtained “cookies” (discs from stumps) where we could get them.

Increment borer used to extract section of wood tissue for analysis

I ended up putting my best person on the daunting task of trying to determine if Bermuda cedar crossdates. A Masters student, Jehren Boehm had just started in my lab at the University of Nevada, Reno and had lots of prior experience crossdating Pinon and Junipers in Nevada as an undergraduate. With considerable effort Jehren was able to determine that “While a faint common signal was detected amongst Bermuda cedar across [Bermuda], more compiled cross sections and geochemical analysis are required to produce a statistically robust regional chronology.” (Boehm, 2019) On the face of it, this result did seem inconclusive, but this study does suggest that there is potential, and with a little more work we may indeed be able to produce a master chronology for Bermuda cedar. We just might need another hurricane to hit so that we can obtain more cookies.

The author coring a tree with an increment borer

My Favourite Part

In addition to the ability to see how all the different pieces of the projects have come together, my favourite part of the Empire, Trees, Climate module is actually the “Vantages of Bermuda” Section. I really enjoyed the use of the story map format to present a story regarding the likely location of where the painter (Savage) or photographer (Platt) were standing when the images were created. I also really enjoyed the use of Savage’s watercolours throughout the series as I think it added an excellent set of visuals to the project. One other really fun parts about seeing these various projects is also seeing some of the connections to other areas of research, including the A Global Tradition module, which is a survey of the McGill University Field stations and the research conducted at these locations. I personally was not part of these projects, but my own research has taken me to Axel Heiberg Island where I conducted fieldwork studying the Eocene fossil forests there as part of my MSc research. In 2016, I even gave a short lecture to a group of McGill University students, who were on their way out to the McGill Arctic Research Station (MARS) on Axel Heiberg, when we overlapped at the Polar Continental Shelf Program complex in the town of Resolute Bay, Nunavut. I have been considering doing additional field work on Axel Heiberg to do work in the Geodetic Hills and surrounding area to scout for Miocene and Pliocene forests, and my colleagues and I had discussed using MARS as a base of operations. So it was quite fun to read more about the history of MARS and where they worked on Axel as part of this story map project.

Map of Meteorological Station on Axel Heiberg Island
Establishing an Arctic Research Station on Axel Heiberg Island


Boehm, J. (2019) “Dendrochronological potential of Bermuda cedar.” Unpublished Masters thesis. University of Nevada, Reno.

Douglass, A.E. (1929) “The secret of the Southwest solved by talkative tree rings” National Geographic Magazine 56(6): 736–770.

Greer, K., Hemsworth, K., Csank, A., & Calvert, K. “Interdisciplinary research on past environments through the lens of Historical-Critical-Physical Geographies (H-CPG),” Historical Geography 46 (2018): 32-47

Schoolman, E., Mensing, S., & Piovesan, G. “From the Late Medieval to Early Modern in the Rieti Basin (AD 1325–1601): Paleoecological and Historical Approaches to a Landscape in Transition,” Historical Geography 46 (2018): 103-128.

Feature image: “King Street looking out on to Whites Island in Hamilton Harbour.” Johnson Savage MD Collection, National Museum of Bermuda 

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Adam Csank is an Assistant Professor in the Department of Geography at the University of Nevada, Reno. His research involves the application of dendrochronology and stable isotope geochemistry to reconstruct past environments, explore plant responses to climate, and understand historic trade networks and land use patterns. He has worked in the Canadian Arctic, Alaska, Ontario, the western United States and the Caribbean.

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