Climate and Tree Growth in a Temperate Coastal Rainforest, Southeast Alaska
What: This Advanced research project aims to develop tree-ring chronologies for red and yellow cedar trees in Alaska and use these data in climate analyses and modeling.
When: June 28-July 26, 2025
Where: The College of Wooster, Wooster, OH and Southest Alaska.
Who: Five students, and project directors Dr. Greg Wiles and Nick Wiesenberg (The College of Wooster).
Prerequisites: None; coursework in statistics or data analysis preferred.
Expectations and Obligations:
1. Participation in field work and data analysis during the summer (4 weeks).
2. Write an abstract and present a poster at a conference (Arctic Workshop in spring 2026).
3. Write a short contribution (4-6 pages text + figures) to be published in the Proceedings of the Keck Geology Consortium 2026 Volume (first draft due Mid-February).
PROJECT DESCRIPTION
Tree-rings are exactly calendar-dated records of environmental change, and in southern Alaska, trees are primarily sensitive to temperature variations. This project aims to (1) develop tree-ring chronologies adding to a growing network of records from Alaska and the Yukon (Figure 1) and (2) use these data in climate analyses and modeling. Previous studies have utilized tree ring records to reconstruct local to hemispheric temperatures (Wiles et al., 2014; Wilson et al, 2016; Anchukaitis et al., 2017), glacier mass balance (Malcomb and Wiles, 2013), and hydroclimate in North America (Wiles et al., 2023).
Figure 1: Tree-ring chronologies from Alaska and the Yukon – this project will be adding to this dataset and using the network for climate reconstruction and modeling (E.R. Cook, pers. Comm.).
The Wooster Tree Ring Lab (WTRL) in collaboration with the Alaska Youth Stewards (AYS) has been actively investigating new tree-ring sites in the forests of Southeast Alaska (SEA). AYS serves the Tlingit-Haida community in SEA preparing youth for environmentally-related careers and college. Our collaboration began in 2020 and has grown to include communities in Hoonah, Angoon, Kake and Klawock all Tlingit villages in SEA. Three of these villages (Kake, Hoonah and Klawock) have been visited in the summers of 2022 through 2024 and the fourth, Angoon, is the destination of the 2025 field season described here. The aim of these visits is to work in the field with the AYS groups, visiting sites AYS groups have discovered, and together, sampling spruce, red and yellow cedar, and mountain hemlock stands. The proposed work in Angoon centers on their remarkable spruce and cedar sites, which are of interest because of their high economic and cultural value. From these collections, we will assemble ring-width and blue intensity tree ring chronologies (Wiles et al., 2019; Wilson et al, 2019), analyze them for their climate significance and connect the tree-ring data to issues of forest health, and potentially as a record of past indigenous use, such as bark stripping (McGrath et al., 2014).
Since 2020, AYS groups have discovered significant sites of dendroclimatic value including the first red cedar site from Alaska, two, 700-year old yellow cedar sites (Figure 2), and a 500 year- old mountain hemlock treeline site. A range of scientific questions can be explored with these data in combination with previous collections (Figure 1) and local knowledge. For yellow cedar, which has been in decline for a century or more at some sites (Gaglioti et al, 2021), there are questions of tree health and ecological succession. Among the questions are: What are the dynamics that appear to be allowing red cedar to occupy new ecological niches with the demise of yellow cedar (B. Buma personal communication)? How unusual is the decline of yellow cedar, is it part of its ecology or an unprecedented phenomenon (Gaglioti et al.,2021)? Finally, the expansive question addressed in this project is how can this growing network be further utilized to investigate the climate of the Gulf of Alaska (GOA) and the larger climate system? These broad ideas can be further refined into hypotheses that students can then test using this annually dated network of records.
Figure 2: Upper Graph – The 700+ year ring-width series from Kake Alaska. This series was built in collaboration with the Kake AYS in the summer 2023. The release in recent decades is due to the death of some of the yellow cedar in the stand due to warming, loss of insulating snow and frost damage. The intervals around 1696 and 1810 are associated with volcanically-forced cooling in the Northern Hemisphere (Leland et al., 2023). Lower Graph – The Northeast Ohio tree-ring series is a plot of ring- widths from more than 1000 series from old and second growth oak stands and series from historical barns and houses. Keck participants in Wooster will add to this record and learn the fundamentals of sampling, data collection and analyses prior to the Alaska trip. The release in ring-widths about 1820 is due to European Settlement in the region. Note that this series, primarily a record of hydroclimate, contains the 1696 and 1810 decreased growth intervals, which are connected, in part, to changes in temperature in the North Pacific (see graph above).
Potential Student Projects
Individual projects will depend on student interests. There is a wide range of projects that can leverage newly developed red and yellow cedar ring-width chronologies and anticipated further sampling of red cedar at Angoon. Given the extensive network of tree-ring data from the region, and the updating of tree-ring records in Ohio and Ketchikan (Figure 2) interesting connections can be made between North Pacific temperatures and North American hydroclimate. The volcanic signal from an 1809 CE eruption in tree-ring records has been examined in detail (Leland et al., 2023), however, the 1696-1700 interval also linked to volcanic cooling has not been investigated (Figure 2) for the North Pacific. How the various tree species respond to climate (ie., seasonal differences and future rates of warming; Gaglioti et al., 2022, 2024) and their use in modeling hydroclimate in North America (Wiles et al., 2023) are emerging areas of research that leverage concepts in ecology and aspects of large-scale teleconnections.
In addition, new directions could be pursued that examine the linkages between the human history of Gulf of Alaska and climate. This would include examination of Tlingit oral histories (ie. Cerne et al., 2020; Hinkley et al., 2022, 2023) as well as possible linkages between the Bering (Bell et al., 2016) and the Cook expeditions in the 18th century. Studies could reconstruct aspects of climate conditions during the years of these expeditions (ie, sea surface temperatures and storminess) and examine the historical record. The WTRL also maintains a collection of tree-ring records from the coastal Russian Fareast (D’Arrigo et al. 2014; Wiles et al., 2014; Deck et al., 2017) and thus an East-West North Pacific comparison of tree-ring records and climate can be further explored. Our collaborators at LDEO-TRL, University of Alaska-Fairbanks (B. Gaglioti; Gaglioti et al., 2019, 2021, 2022, 2024) and The Environmental Defense Fund (Buma et al, 2019) are all currently actively working in the region will be among the group of experts we can meet with remotely as needed.
Project Logistics
This project will span the final days of June and the first three weeks of July. The group will first meet in Wooster for an orientation to tree-ring sampling built around updating an old growth tree-ring site close to the Wooster campus (Figure 2). During these first days, students will take a wilderness first aid course and work on the core samples from our archives. Additionally, the group will read and discuss some of the scientific issues of North Pacific climate prior to traveling to Alaska, becoming familiar with climate analysis software, the literature, and the scientific questions that students can potentially address.
The group will then travel to Juneau, Alaska where we will stay for two days updating the easily accessible sites in the surrounding coastal range as well as hiking to Mendenhall Glacier. The Juneau tree-ring sites were originally sampled in 1999 by the WTRL and LDEO-TRL. Updating the Juneau sites will serve as an orientation to Alaska’s coastal forests and potentially serve as a student project. We will then travel to Angoon via ferry and meet with the AYS group. Activities while in Angoon will consist of our core tree-ring instruction and sampling and activities driven by the AYS curriculum involving aspects of subsistence living (ie., fishing and cleaning fish, canning bull kelp and beach asparagus, berry picking as well as other service-based projects in the community).
After the stay in Angoon the group will return to Juneau and fly back to the Wooster Tree Ring Lab in Ohio where we will commence data collection and further develop student’s individual projects. In addition, the group will also need to periodically update the AYS groups as results become available. Earth Sciences at Wooster maintains a Wooster Geologists blog and students will make entries to this as well as build a poster of the experience in Alaska.
References
Anchukaitis, K.J., R. Wilson, K. Briffa, U. Büntgen, E.R. Cook, R.D. D’Arrigo, N. Davi, J. Esper, D. Frank, B. Gunnarson, G. Hegerl, S. Helama, S. Klesse, P.J. Krusic, H. Linderholm, V. Myglan, T. J. Osborn, Z. Peng, M. Rydval, L. Schneider, A. Schurer, G. Wiles and E. Zorita, 2017, Last millennium Northern Hemisphere summer temperatures from tree rings: Part II: spatially resolved reconstructions, Quaternary Science Reviews 134: 1-18, JQSR-D-16-00439R1.
Bell, B. B., Luna, Eduardo T., Deck, C. B., Wiesenberg, N. and Wiles, G., 2016, North Pacific Climate and the C.E. 1741 Vitus Bering Expedition to Alaska: Geological Society of America Abstracts with Programs. Vol. 48, No. 7, doi: 10.1130/abs/2016AM-285664.
Buma B, Bisbing S, Wiles G, Bidlack A., 2019, Primary succession observations over a century do not support textbook explanations of facilitation/sequential change. Ecology. https://doi.org/10.1002/ecy.2885.
Cerne, C., Wiles G.C., Wiesenberg, N., Gaglioti, and Lapke, A., 2020, Tree-ring and Oral History Together Guide the Prehistory of Hoonah and Glacier Bay, Alaska: Annual Meeting of the American Geophysical Union, December 2020.
D’Arrigo, R., Wilson, R., Wiles, G., Anchukaitis, K., Solomina, O. Davi, N., Deser, C., Dolgova, E., 2014, Tree ring reconstructed temperature index for coastal northern Japan: implications for western North Pacific variability, International Journal of Climatology, doi.org/10.1002/joc.4230.
D’Arrigo R, Davi N, Jacoby G, Wilson R, Wiles G. 2014, Dendroclimatic Studies: Tree Growth and Climate Change in Northern Forests. AGU Monograph (Book), Wiley, ISBN: 978-1-118-84872-2.
Deck, D., G. Wiles, V. Matskovsky, T. M. Kuderina, Frederick, S., O. Solomina, R.D’Arrigo, and N. Wiesenberg, 2017, Climate response of Larch and Birch across an elevational transect and hemisphere-wide comparisons, Kamchatka Peninsula, Russian Far East: Special Issue of Forests, 8:315; doi:10.3390/f8090315.
Gaglioti, B. V., Mann, D. H., Wiles, G. C., Andreu-Hayles, L., Hansen, W. D., & Wiesenberg, N. (2024). Forest-wide growth rates stabilize after experiencing accelerated temperature changes near an Alaskan glacier. Geophysical Research Letters, 51, e2024GL109469. https://doi. org/10.1029/2024GL109469
Gaglioti, B.V., Mann, D.H., Williams, A.P., Wiles, G.C., Oelkers, R., Jones, B.J., and Andreu Hayles, L., 2019. Traumatic resin ducts in Alaska: Mountain hemlock trees provide a new proxy for winter storminess: Journal of Geophysical Research, Biogeosciences, doi:10.1029/2018JG004849.
Gaglioti, B.V., Mann, D., Wiles, G. and Wiesenberg, N., 2021, Is the modern-day dieback of yellow-cedar unprecedented? Canadian Journal of Forest Research 51 (12), 1953-1965.
Gaglioti, B.V. Mann, D.H., Wiles, G.C., 2022, Ecosystems at Glacier Margins Can Serve as Climate- Change Laboratories: Geophysical Research Letters 49 (13), doi.org/10.1029/2022GL098574.
Hinkley, L., W. Zhao, N. Wiesenberg, E. Peabbles, B. Gaglioti, J. Fu and G. C. Wiles, 2022, Cedar Tree Ring Histories from Southeast Alaska: A Collaborative Student Project: The national meeting of the American Geophysical Union (AGU), Chicago.
Hinkley, L.W., Cooper, T., Gaglioti, B., Navareaz, J., Wiesenberg, N. and Wiles, G.C., 2023, The intersection of oral histories and tree-ring chronologies in Southeast Alaska: Geological Society of America Abstracts with Programs. Vol. 55, No. 6, doi: 10.1130/abs/2023AM-392714
Malcomb, N.L. and Wiles, G.C., 2013, Tree-ring based reconstructions of North American glacier mass balance through the Little Ice Age. Quaternary Research, http://dx.doi.org/10.1016/j.yqres.2012.11.005.
McGrath, S., Howell, W., Wiesenberg, N., Mennett, C., and Wiles, G., 2014, Three hundred years of continuity: a yellow cedar bark stripping site on Pleasant Island, Icy Strait, Southeast Alaska: Geological Society of America Abstracts with Programs. Vol. 46, No. 6, p. 247.
Leland, C., D’Arrigo, R., Davi, N., Anchukaitis, K. J., Andreu-Hayles, L., Porter, T. J., et al. (2023). A spatiotemporal assessment of extreme cold in northwestern North America following the unidentified 1809 CE volcanic eruption. Paleoceanography and Paleoclimatology, 38, e2022PA004581. https://doi.org/10.1029/2022PA004581
Trouet, V., Van Oldenborgh, G.J., 2013. KNMI Climate Explorer: A web-based research tool for high- resolution paleoclimatology. Tree-Ring Research 69(1):3-13.
Wiles, G.C., D’Arrigo, R.D., Barclay, D., Wilson, Jarvis, S. K., Vargo, L., Frank, D., 2014, Surface air temperature variability for the Gulf of Alaska over the past 1200 years: The Holocene, DOI: 10.1177/0959683613516815.
Wiles, G.C., Solomina, O., D’Arrigo, R.D., Anchukaitis , K., Gensiarovsky, Y. and Wiesenberg, N., 2014, Reconstructed Summer Temperatures over the Last 400 Years Based on Larch Ring Widths: Sakhalin Island, Russian Far East: Climate Dynamics, DOI:10.1007/s00382-014-2209-2.
Wiles G., Charlton J, Wilson R, D’Arrigo R, Buma B, Krapek J, Gaglioti B, Wiesenberg N, Oelkers R., 2019, Yellow-cedar blue intensity tree ring chronologies as records of climate and forest-climate response, Juneau, Alaska, USA. Canadian Journal of Forest Research, https://doi.org/10.1139/cjfr- 2018-0525
Wiles, G.C., Devereux, K., Gaglioti, B.V., D’Arrigo, R.D., 2023, A 420-Year Perspective on Winter Lake Erie Levels: Geophysical Research Letters 50 (1), doi.org/10.1029/2022GL099911.
Wilson, R., D’Arrigo, R., Andreu-Hayles, L., Oelkers, R., Wiles, G., Anchukaitis, K and Davi, N., 2017, Blue Intensity based experiments for reconstructing North Pacific temperatures along the Gulf of Alaska: Clim. Past Discuss., doi:10.5194/cp-2017-26.
Wilson, R., Anchukaitis, K., Briffa, K., Büntgen, U., Cook, E., D’ Arrigo, R., Davi, N., Esper, J., Frank, D Gunnarson, B., Hegerl, G., Helama, S., Klesse, S., Krusic, P., Linderholm, H., Myglan, V., Osborn, T., Rydval, M., Schneider, L., Schurer, A., Wiles, G., Zhang, P. and Zorita, E., 2016, Last millennium Northern Hemisphere summer temperatures from tree rings: Part I: the long-term context: Quaternary Science Reviews (2016), pp. 1-18 DOI information: 10.1016/j.quascirev.2015.12.005
Wilson, R., K Anchukaitis, L Andreu-Hayles, E Cook, R D’Arrigo, N Davi, L Haberbauer, P Krusic, B Luckman, D Morimoto, R Oelkers, G Wiles, C Wood, 2019, Improved dendroclimatic calibration using blue intensity in the southern Yukon. The Holocene, 29(11), 1817-1830, https://doi.org/10.1177/0959683619862037.