Symposium 1. Tree rings from national forest inventories: a timely opportunity to assess tree growth across space and through time

Chaired by : Girardin, M.-P., Babst, F., de Rose, J., Evans, M., Gutierrez, G., Klesse, S.

Tree-ring time series provide long-term, annually resolved information on the growth of individual trees. However, public tree-ring archives contain a considerable portion of data collected from trees that have been selected with specific research questions in mind (e.g., for climate reconstruction).  This makes these archives a biased representation of the sensitivity of forest ecosystems to ongoing climate variation (e.g. temperature, precipitation), including non-stationarity (i.e., global warming and associated changes to Earth’s climate). Many public collections also lack the tree and forest information needed to quantify forest-level growth, making it very difficult to scale-up tree-level information to ecosystem estimates of biomass accumulation and carbon sequestration. National forest inventories (NFIs), by comparison, are systematic observatories of forest ecosystems designed specifically for large-scale inference. Yet, this spatial information comes at relatively low temporal (e.g. decadal) resolution and hampers the investigation of forest responses to annual climate variability as well as seasonal and climate extremes. When tree-ring data are collected in NFIs (or other statistically designed) forest plot networks, multiple influences on tree growth can be captured in an unbiased and representative way—not just climate, but also competition, disturbance processes, and other environmental factors (atmospheric CO2 concentration, N deposition)—which is critical to parse their effects and understand how they may interact. A systematic effort to sample tree rings in NFIs can yield unprecedented temporal and spatial resolution of the drivers of forest and carbon dynamics. This symposium aims to showcase the latest work on the development and applications of tree rings collected from NFIs and forest plot networks. Applications of NFI tree-ring data may include retrospective analyses of spatial variations in productivity and climate sensitivity, efforts to improve carbon accounting, examinations of climate change impacts, and assessments of mitigation potential critical for Earth’s habitability.

Symposium 2. Common garden experiments to evaluate tree adaptation in a changing climate

Chaired by: Depardieu, C., Girardin, M.-P., Chhin, S., Rozenberg, P. 

Current and projected changes in climate are estimated to be from 10 to 100 times faster than the natural adaptive capacity of trees whose generation times are long. As extreme climatic events are becoming more frequent and exert a strong selection pressure on tree populations, there is an urgent need to better characterize the genetic variability involved in the response of trees to climate. There is currently a lack of knowledge on the role of genetic variability in tolerance to climatic variations and on population evolution in trees. This context advocates the use of multidisciplinary approaches and innovative tools to measure traits that reflect how and when climate exerts selective constraints on trees. The concurrent analysis of tree-ring traits derived m from dendroecology, wood anatomy, and genotypes from provenance tests allows the quantification of the genetic variability associated with traits important for climate adaptation, within and between populations planted on the same site. This symposium aims to showcase the latest work on the development and applications of tree rings and genomics from provenance testing under common garden experiments. In particular, we will show that the development and implementation of interdisciplinary projects is the key to quickly and effectively preparing tree species for future climate. The studies presented at this symposium may include those that assess genetic differentiation, climate sensitivity across populations, support land use planning efforts, identify adequate seed sources for reforestation, and increase forest performance and value under future climatic constraints.

Symposium 3. Ecophysiological interpretations of stable isotopes in dendroecology

Chaired by : Szejner, P., Lavergne, A., Voelker, S., Guerrieri, R., Csank, A.

The interpretation of stable isotopes in a dendroecological framework can provide powerful insights into how trees adjust physiologically in response to the environment. This symposium aims to bring together researchers who use stable isotopes in tree rings to address ecophysiological responses to environmental changes from intra-annual to multi-decadal resolution. We hope this symposium will enable fruitful discussions and new ideas and help identify new research directions aiming to foster new collaborations between researchers within the scientific community. Therefore, we welcome submissions presenting new scientific approaches on tree-ring isotopic observations and comparisons to data and models based on forest dynamics, ecophysiology, hydrology, biogeochemistry and, remote sensing. Specific topics this session is anticipated to include:

1.         Changes in carbon isotope discrimination and water-use efficiency in response to environmental changes (climate, atmospheric CO2, atmospheric deposition).

2.         Seasonal and environmental changes recorded in intra-annual isotopic variations (Studies using xylogenesis, Quantitative wood anatomy, and isotopes).

3.         Changes in water source and source versus relative humidity interactions. (Oxygen isotopes)

4.         Using d15N in tree rings to assess changes in environmental conditions (Nitrogen availability, atmospheric deposition).

5.         Impacts of climate change on plant functioning under different environmental conditions (dry versus humid) (multi-species interactions).

6.         Forest responses to disturbances (e.g., fires, outbreaks, etc.).

7.         Improvements of vegetation models using multiple tree ring parameters.

8.         Projections of forest responses to future climate change informed by stable isotopes.

Symposium 4. Dendrogeochemistry: moving beyond potential

Chaired by: Csank, A., Daux, V., Belmecheri, S. Voelker, S. Lavergne, A.

In their book chapter in 2011 Gagen et al. (2011) highlighted the need for stable isotope dendroclimatology to move beyond studies that simply demonstrate ‘potential’. This symposium, more than a decade since this publication, will focus on dendrogeochemical studies that demonstrate that the field has moved beyond studies focused on ‘potential’. In particular, this session will strive to identify compelling new insights into unique aspects of reconstructions that can be developed through the use of dendrogeochemical records. We also welcome submissions that present multi-proxy studies including isotopes to highlight the advantages that can be gained by expanding our dendroclimatological toolbox.

This symposium should thus serve to stimulate new advances and collaborations by showing how geochemical records from tree-rings can be used as a valuable tool in ways that serve to complement or enhance what can be gained through traditional ring width-based dendroclimatology.

Tree ring stable isotopes, for example, can record different, or stronger, climate signals than those available from traditional tree-ring proxies, do not require detrending, and thus can provide a more comprehensive view of past climates. New high resolution radiocarbon studies from tree rings have improved our ability to date archaeological material, as well as provided insight into past cosmogenic events, finally providing evidence of the elusive solar signals originally sought by A.E. Douglass. Advances in dendrogeochemistry of mercury, and other heavy elements has provided important insight into historic patterns of atmospheric pollution, wildfire and volcanic activities. This session aims to demonstrate to the tree-ring community how far beyond potential dendrogeochemistry has come.

Symposium 5. Applications of dendrochronology in urban environments

Chaired by: King, G., Rissanen, K.

As of 2020, 56% of the world’s population live in urban areas. These individuals benefit from numerous ecosystem services provided by urban forests, including urban heat island mitigation, energy use reduction, stormwater interception, wildlife and pollinator habitat provision, air pollution removal, and carbon sequestration. Urban greenspaces are also often the most accessible avenue for exposure to the natural environment, providing additional aesthetic, recreational, and psychological benefits. However, we know surprisingly little about urban tree growth often applying knowledge from non-urban ecosystems. Dendrochronology offers a valuable field-based method that can improve quantification of urban tree growth, evaluate response to environment, and project how planted trees can be expected to perform in various environments in the future. A few possible avenues of investigation include: the potential to measure the impact of urban land-use on urban forest growth, evaluate the scale and monetary value of carbon sequestration, determine the spatial and temporal legacies of environmental pollution using urban trees for biomonitoring, and assess resistance and resilience of urban forests to extreme climatic events. This potential is also challenged due to larger spatial heterogeneity in growth conditions and many co-occurring anthropogenic effects (e.g. soil compaction, mechanical wounding, excess irrigation, salinity, etc.) that may impact cross-dating and developing common growth curves.

Symposium 6. Advancing (Ameri)Dendro Allyship

Chaired by: Copes-Gerbitz, K., Axelson, J., Gentry, C.

Allies have emerged as key enablers of diversity and inclusivity initiatives in the workplace, in professional associations, and in everyday life. But what is an ally? What skills are required to be an effective ally? How do we hold ourselves and our community members accountable for being effective allies? This symposium will provide a deeper understanding of what it means to be an ally and the skills to help advance allyship as individuals and as a community. Furthermore, this symposium will bring together different perspectives of allyship and provide attendees an opportunity to ask questions and practice important allyship skills in a safe and welcoming space.

Specifically, we envision a 1.5-hour session that includes a facilitated panel discussion, bystander intervention training, and an opportunity to discuss the topics covered in more detail. First, the facilitated panel discussion will bring together 4-5 individuals in different careers and career stages related to dendrochronology who will speak to why allyship is important and how they have worked to enact it within their own lives and careers (~30 minutes). This panel will include time for audience questions. Then, there will be a bystander intervention training that includes small group activities to help attendees learn and practice skills necessary to act as effective allies (~45 minutes). This training will ideally help address some of the problematic scenarios or explore the opportunities discussed in the panel. Finally, we will close with a small or large group session (depending on audience size) for final questions and reflections (~15 minutes). 

Symposium 7. Historical Timbers and Wooden Artifacts as Archives: New Glimpses On Trees, Ecology, and People

Chaired by: Leland, C., Rochner, M. Domínguez Delmás, M., de Graauw, K., Pederson, N. 

Information garnered from historical timbers and wooden artifacts (e.g. houses, barns, ships) can greatly enhance our understanding of human, ecological, and climate history, especially in regions where few old-growth forests and trees remain, tree longevity is relatively short (less than 300-400 years), and environmental conditions break down wood rather quickly, like in mesic to wet regions Over the last decade plus, the application of tree-ring techniques on wooden archaeological material is quickly growing beyond the dating of historic structures and climate reconstructions. New advances and recent works have highlighted a range of applications, including ecological change and disturbance, human-environment interactions, and deeper questions about historical human development (e.g. trade and migration through provenancing materials). 

Our symposium will feature a diverse set of international scientists who work with materials and data from historical timbers and wooden artifacts in different subdisciplines including ecology, human history, and astrophysics. Speakers will cover the breadth of these studies, including the movement of wooden materials between broad regions, cultural and economic uses of wood material, shipwrecks, and new approaches in provenancing wooden pieces created by people and moved to new regions or continents. We also hope to feature a geneticist to educate us about the application of new techniques that could be applied to tree-ring research and, specifically, historical timbers and wooden artifacts.

Symposium 8. Dendrochronological progress in tropical Americas

Chaired by: Andreu-Hayles, L., Ferrero, E., Anchukaitis, K., Locosselli, G., Tejedor, E., Rodriguez-Morata, C.

Dendrochronological archives in the tropics of the Americas have been under-studied for a long time. Some of the challenges include the Identification of tree-ring boundaries in certain tree species, absence of winter dormancy associated to low temperatures in most of the cases, and logistic difficulties of fieldwork in remote sites. However, part of the slow progress is also related to the fact that historically much less resources have been invested in dendrochronological research in the tropics than in other regions of the world. Nevertheless, more studies have been published over the last decade leading to important achievements such as the expansion of tree-ring networks due to an increase in the number of available chronologies from a wide variety of tree species, as well as different methodological approaches. In addition to tree-ring width (TRW), now stable carbon and oxygen isotopes, Quantitative Wood Anatomy, autofluorescence and chemistry provide means to develop tree-ring research in the tropical region. In this symposium, we will show progress done in the Tropical Americas highlighting studies from different countries. Mexico has been pioneering with the development of over 40 TRW chronologies, while new TRW chronologies in Guatemala can contribute to a better management of water resources. In South America tree-ring chronologies were generated from multiple tree species measuring distinct parameters at the western (dry) and eastern (wet) flanks in Central Andes of Peru and Bolivia, while in the seasonally dry forests of Brazil, alive and subfossil tree-ring records have been developed. This symposium intends to provide new insights into forest responses to climate, stand dynamics or other environmental events, based on tree-ring analyses, and updated on more useful methodologies with the main goal being to push tropical dendrochronology for the following decades through international collaborative research.