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Closing dendrochronology gaps in the American tropics

• Why is dendrochronology important to me?


Dendrochronology is important for me because it allows us to assess annually a suite of processes that trees have been subject to. Currently, there are many variables that we can measure in tree rings with annual resolution and all of them allow us to study different processes: ring width, density, isotopes, blue intensity, non-structural carbohydrates, or anatomical features such as cell size, pore quantity, etc. For instance, in my research, I use ring widths as a proxy for carbon sequestration and isotopes to assess water use efficiency.


• How did I get into dendrochronology?


I am a forest engineer from Colombia. When I was taking classes, I was intrigued about forest management in the tropics, and I was surprised by the huge information gaps we had regarding tropical tree growth, mainly in native species.





I got into dendrochronology after I took a natural forest silviculture class with Professor Jorge Ignacio del Valle. He was doing pioneer work in dendrochronology in Colombia because he was convinced of the periodicity of tree growth in the tropics. Even though at that time there were not too many studies supporting this statement and it was still a belief that tropical trees did not form annual growth rings. He taught us about the importance of having a way to assess tree growth with annual resolution and the many applications that might have such as sustainable forest management, ecology, climatology, and even a way to assess climate change’s impact on tree growth. After the semester was over, he recruited me to work for him as an undergrad research assistant, and I started working on my first dendrochronology project which turn into my undergrad thesis.


• What am I currently doing? Tropical dendrochronology, ecology, and filling the gaps.


I am currently a four-year Ph.D. candidate in the biology department at the University of Miami. My research focuses on filling the gaps in tropical dendrochronology, dendroecology, and assessing how climate change is affecting tree growth rates in different ecosystems throughout the American continent. To address this big question, me and my advisor Dr. Kenneth Feeley designed two projects similar projects in different ecosystems.


The first project examines long-term growth patterns at multiple sites spanning the climatic niches of two tropical tree species and water use efficiency (Jacaranda copaia and Virola sebifera) along an altitudinal gradient in the Northern Andes of Colombia between 100-1700 m asl. Through tree-ring analyses, we are characterizing decadal-to-centurion-scale changes in tree growth in relation to species’ climatic niches as modeled from the species’ distributional data. We will identify how growth rates are changing through time and in relation to a sample population’s position within a species’ range. The sampling design will allow us to test the prediction that the effects of warming will depend on where the sampled populations fall within the species’ ranges. Accordingly, we predict the growth rates of J. copaia and V. sebifera to be decreasing in populations located at lower elevations but increasing in populations located at higher elevations because of global warming. We expect that the water use efficiencies of trees in Colombia are increasing over time as they respond to increased evaporation and greater water loss caused by climate change coupled with the effects of “carbon fertilization”.



The second project evaluates annual tree growth increments of South Florida trees and water use efficiencies of South Florida trees. We will assess how global warming is affecting subtropical tree growth rates (and hence rates of carbon sequestration) over long time scales and in relation to species’ geographic ranges. Specifically, South Florida is in the southern extent and therefore the hotter part of Quercus virginiana and Pinus elliottii ranges, but it is also in the northern extent and therefore the cooler part of Swietenia mahagoni and Bursera simaruba ranges. As such, the proposed sampling design will allow us to test the prediction that the effects of warming will depend on where the sampled populations fall within a species’ range. We predict that the growth rates of Q. virginiana and P. elliottii are decreasing but those of S. mahagoni and B. simaruba are increasing. We also predict that the water use efficiencies of trees in South Florida are increasing over time as they respond to increased evaporation and greater water loss caused by climate change coupled with the effects of “carbon fertilization”.


• Diversity, Equity, Inclusion, and Justice.


Since the end of the pandemic, our department started working to improve its diversity, equity, and inclusion standards. I offered myself to help in this area because I felt that as a senior and more experienced grad student, I start my Ph.D. late, and I am older than the average grad student in the department. Before starting my Ph.D., I worked for more than 10 years in the private and public sectors in Colombia and that allowed me to gain experience managing relationships, learn to work as part of a team, etc. Also, I think that as part of a minority from a developing country I can offer a different point of view to help us have a more diverse, equitable, and inclusive work environment.

One of the department’s first actions was the creation of the diversity, equity, and inclusion committee. I am part of this committee since 2021, and we have been developing a bill of rights to help students deal with abusive relationships from their advisors because there is usually a gap for grad students. We are considered students sometimes and workers in other situations.

Twitter @ManuelBernalE

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