← Projects · NSF‑1660185

Developing a network of n-alkane hydrogen isotope records to identify drivers and impacts of Holocene droughts

This project addresses patterns and drivers of past droughts and their effects on humans and the biosphere. The researchers analyze lake-sediment cores to develop records of precipitation variability associated with past shifts in major drivers of atmospheric circulation that influenced the broader circum-Caribbean region, including the U.S. Gulf Coast. The precipitation records are compared to evidence of past human activity and biomass burning in lake watersheds, to explore local consequences of regional shifts in atmospheric drivers. The work forms the foundation for an expanded network of precipitation reconstructions across the region that will allow examination of processes at a larger spatial scale and of additional drivers. The project provides experience in multi-laboratory collaborative research to four faculty and ten or more graduate and undergraduate students. Results are broadly disseminated through publications and presentations, and the researchers share findings with K–12 students and teachers in Tennessee and North Carolina through outreach projects that include hands-on activities and authentic research.

The researchers develop precipitation records using compound-specific hydrogen isotope analyses of n-alkanes in lipids from sediment cores at five lakes along two transects that cross climate and ecosystem regions. Hydrogen isotope analysis of lipids in sediment cores is an alternative to oxygen isotope analysis of biogenic carbonates that can be applied in a wide variety of lakes, making it possible to develop a network of sites using the same precipitation proxy. Records from existing cores in Costa Rica serve as the western anchor in a larger network of precipitation records planned through the broader circum-Caribbean region, including the U.S. Gulf Coastal Plain. The hydrogen isotope analyses document the geography of multi-decadal drought during the Terminal Classic Drought (~1200–850 cal yr BP), the Little Ice Age (~500–100 cal yr BP), and at other times, and reveal whether these were exceptional or outlier droughts for the Holocene as a whole. Comparison with local paleoenvironmental and archaeological evidence shows how past droughts affected vegetation, fire regimes, and prehistoric agriculture.

Team

Personnel related to the project

Principal investigators

Dr. Sally P. Horn, Professor, Department of Geography, University of Tennessee–Knoxville
Dr. Chad S. Lane, Associate Professor, Department of Earth and Ocean Sciences, UNC Wilmington
Dr. Douglas W. Gamble, Professor and Chair, Department of Earth and Ocean Sciences, UNC Wilmington

Faculty associate

Dr. Erik Johanson, Assistant Professor, Department of Geosciences, Florida Atlantic University

Graduate research assistants

Matthew Kerr, Ph.D. Student, University of Tennessee–Knoxville
Mathew Boehm, Ph.D. Student, University of Tennessee–Knoxville
Morgan Douglas, M.S. Student, UNC Wilmington
Krysden Schantz, M.S. Student, UNC Wilmington
Elizabeth Yanuskiewicz, M.S. Student, UNC Wilmington
Elizabeth MacLennan, M.S. Student, University of Tennessee–Knoxville

Undergraduate research assistants

Luke R. Blentlinger, Eric Collins, Julie Coulombe, Akhil Gosai, Allen Prince, Emma Reed, Trell Stroud, and Wesleigh Wright (University of Tennessee–Knoxville); Bonnie Williams and Audrey K. Taylor (UNC Wilmington, the latter now a Ph.D. student at Notre Dame)

Output

Publications related to this project

2018
Horn, S.P., Johanson, E.N., Haberyan, K.A., Boehm, M.S., Johanson, J.L., Sánchez P., M., and Hernández V., M. Initial limnological observations at five small lakes in southern Pacific Costa Rica. Cuadernos de Investigación UNED / UNED Research Journal 10(1): 119–134.
2016
Horn, S.P. and Haberyan, K.A. Lakes of Costa Rica. Pp. 656–682 in Kappelle, M. (Ed.), Costa Rican Ecosystems. Chicago: The University of Chicago Press.
2016
Lane, C.S., Horn, S.P., Taylor, Z.P., and Kerr, M.T. Correlation of bulk sedimentary and compound-specific δ¹³C values indicate minimal pre-aging of n-alkanes in a small tropical watershed. Quaternary Science Reviews 145: 238–242.
2014
Lane, C.S., Horn, S.P., and Kerr, M. Beyond the Mayan lowlands: impacts of the Terminal Classic Drought in the Caribbean Antilles. Quaternary Science Reviews 86: 89–98.
2013
Lane, C.S., and Horn, S.P. Terrestrially derived n-alkane δD evidence of shifting paleohydrology in highland Costa Rica. Journal of Arctic, Antarctic, and Alpine Research 45: 342–349.

Conference

Presentations related to this project

2019
Johanson, E.N., M.T. Kerr, S.P. Horn, L.R. Blentlinger, and C.S. Lane. A 4,200-year record of fire history from the southern Pacific Costa Rica lowlands. AAG Annual Meeting, Washington, D.C.
2019
Horn, S.P., M.S. Boehm, M.T. Kerr, E. Reed, W. Wright, C.S. Lane, M. Arford, and J. Graham. New proxy analyses from Laguna Martinez, Costa Rica. AAG Annual Meeting, Washington, D.C.
2019
Kerr, M.T., S.P. Horn, and C.S. Lane. A revised chronology of paleohydrology and vegetation change at Laguna Bonillita, Costa Rica. AAG Annual Meeting, Washington, D.C.
2019
Yanuskiewicz, E., C.S. Lane, E. Johanson, M.T. Kerr, and S.P. Horn. Compound-specific stable carbon isotope analysis of vegetation and land-use change at Laguna Los Mangos, Costa Rica. AAG Annual Meeting, Washington, D.C.
2018
Blentlinger, L.R., S.P. Horn, M.T. Kerr, and C.S. Lane. Hydrogen isotope analysis of n-alkanes in sediments of Emerald Pond, Abaco Island, The Bahamas. SEDAAG Annual Meeting, Johnson City, TN.
2018
Kerr, M.T., S.P. Horn, and C.S. Lane. Sedimentary nitrogen as a proxy for prehistoric forest clearance and site abandonment in southern Pacific Costa Rica. SEDAAG Annual Meeting, Johnson City, TN.
2018
Kerr, M.T., Horn, S.P., and Lane, C.S. A 10,000 year hydrogen isotope record of precipitation variability from highland Costa Rica. AAG Annual Meeting, New Orleans, LA.
2018
MacLennan, E., Horn, S.P., Kerr, M.T., Lane, C.S., and Ellis, K. A compound-specific hydrogen isotope record of precipitation from coastal North Hispaniola. AAG Annual Meeting, New Orleans, LA.
2018
Horn, S.P., Johanson, E.N., Haberyan, K.A., Boehm, M.S., Johanson, J.L., Sánchez P., M., and Hernández V., M. Limnological observations at five Costa Rican lakes. 3rd Biennial Geography Symposium, Knoxville, TN.
2018
Blentlinger, L., and Horn, S.P. Experiments with magnetic susceptibility. 3rd Biennial Geography Symposium, Knoxville, TN.
2018
Collins, E., and Horn, S.P. Comparing size measurements of prehistoric maize pollen grains in Costa Rica and the Dominican Republic. 3rd Biennial Geography Symposium, Knoxville, TN.
2018
Johanson, E.N., S.P. Horn, C.S. Lane, and J.A. Cecil. Fire history across the Little Ice Age in southern Pacific Costa Rica. AAG Annual Meeting, New Orleans, LA.
2017
Blentlinger, L.R., S.P. Horn, E.N. Johanson, M.T. Kerr, C.S. Lane, M.S. Boehm, and J.A. Cecil. Proxy analyses of wetland sediments in Costa Rica. SEDAAG Annual Meeting, Starkville, MS.
2017
Blentlinger, L.R., S.P. Horn, E.N. Johanson, M.T. Kerr, J.A. Cecil, C.S. Lane, and M.S. Boehm. Reconstructing past environments in Costa Rica through analyses of wetland sediments. University of Tennessee Discovery Day, Knoxville, TN.
2017
Taylor, Z.P., C.S. Lane, and S.P. Horn. Hydrogen isotope evidence of climatic control on prehistoric agricultural activity in southern Costa Rica. AAG Annual Meeting, Boston, MA.
2017
Johanson, E.N., S.P. Horn, and C.S. Lane. Pre-Columbian agriculture, fire, and Spanish contact: a 4,300-year record from Laguna Los Mangos, Costa Rica. AAG Annual Meeting, Boston, MA.
2017
Kerr, M.T., C.S. Lane, and S.P. Horn. Compound-specific stable hydrogen isotope (δD) analysis of lake-sediment cores: a key method for reconstructing prehistoric droughts and effects. XI Congreso de Antropología, San José, Costa Rica.
2017
Horn, S.P., C.S. Lane, E.N. Johanson, M. Sanchez, Z.P. Taylor, and M.T. Kerr. Stable carbon isotope ratios in Costa Rican lake sediments as a proxy for forest clearance and crop cultivation. XI Congreso de Antropología, San José, Costa Rica.
2016
Horn, S.P., M. Sánchez, C.S. Lane, Z. Taylor, M.T. Kerr, Johanson, E.N., and J.A. Cecil. Late Holocene fires in Costa Rica: patterns and drivers. AAG Annual Meeting, San Francisco, CA.
2016
Kerr, M.T., S.P. Horn, and C.S. Lane. Precipitation variability over the past 2,500 years at Laguna Bonillita, Costa Rica. AAG Annual Meeting, San Francisco, CA.
2016
Johanson, E.N., S.P. Horn, and C.S. Lane. A 4,000-year record of paleoenvironmental change and agriculture intensification from Laguna Los Mangos in southern Pacific Costa Rica. AAG Annual Meeting, San Francisco, CA.
2015
Johanson, E.N., S.P. Horn, and C.S. Lane. Late Holocene paleoenvironments and human–environment interactions from southern Pacific Costa Rica: two new records. AAG Annual Meeting, Chicago, IL.

Broader impacts

Outreach related to this project

University of Tennessee summer "Kids U" course on climate change and human society

At the University of Tennessee, GRA Matthew Kerr shared research on climate change and humans with high school students in a summer course he developed on the "Collapse of Civilizations," which he taught for the fourth time in 2017 through UT's Kids U summer program.

University of Tennessee "Mastodon Matrix" workshop for teachers

In December 2017, Horn, Kerr, and GRA Mathew Boehm partnered with the Tennessee Geographic Alliance to run a Mastodon Matrix workshop for K–8 teachers on using encasing sediment from mastodon excavations for hands-on teaching about fossils and paleoenvironmental change. The workshop used material donated to Horn by the Paleontological Research Institution in New York, and teachers took home "goody bags" of mastodon matrix to use with their students.

Oceans 17 program for high school juniors and seniors (UNCW)

In summer 2017, two groups of 15 high school juniors and seniors in the Marinequest Oceans 17 summer education program at the UNCW Center for Marine Science conducted two-day mini-projects in the UNCW stable isotope facility under the supervision of Co-PI Lane, analyzing the bulk isotopic composition of flora and fauna collected along salinity gradients to observe impacts on vegetation distributions and establish trophic relationships between marine organisms based on stable nitrogen isotope analyses. Lane gave lectures on stable isotope applications in biological and geological research, including an introduction to compound-specific hydrogen isotope analyses and their application to paleoclimate reconstructions, and worked individually with student groups touring the GC-IRMS system as they awaited their bulk isotope results.