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Laguna Santa Elena (8.9290° N, 82.9257° W, 1055 m a.s.l.) is a small lake in the Diquís archaeological sub-region of southern Pacific Costa Rica. Previous analyses of pollen and charcoal in a sediment core from Santa Elena revealed a nearly 2,000 year history of vegetation change, maize cultivation and site occupation that is consistent with the archaeological record from the lake basin and surrounding area. Here we present the results of new loss-on-ignition, geochemical and bulk stable carbon (δ13C) and nitrogen (δ15N) isotope analyses of the Santa Elena sediments that supplement and refine the previous reconstruction. Like many lakes in Central America and the Caribbean, Laguna Santa Elena was a magnet for humans throughout its history. As a result, the lake experienced vegetation modification by humans and maize cultivation at varying intensities over a long duration. The Santa Elena sediments provide a record of palaeoenvironmental change during times of major culture change and increasing cultural complexity in the Diquís region, which occurred during intervals of broader changes driven by external forcing mechanisms, including the Terminal Classic Drought (TCD), the Little Ice Age (LIA) and the Spanish Conquest. Our high resolution lake sediment study from Santa Elena reveals details of these events at the local scale that are unobtainable by other means, including the timing of the initial intensification of maize cultivation at ca. 1,570 cal BP (AD 380) and two intervals of population decline coinciding with the TCD at ca. 1,085 cal BP (AD 865) and near the start of the LIA at ca. 683 cal BP (AD 1267).
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This content will become publicly available on July 30, 2026
Late Holocene tundra fires and linkages to climate and vegetation in Northern Alaska
Charcoal particles in lake sediments can reveal past fires and linkages to climate and vegetation change. We use analyses of charcoal accumulation rates from two lakes on the Alaskan North Slope to reconstruct past fire activity, and charcoal morphology to identify changes in fuel sources. Charcoal peak analyses were used to calculate individual fire-return intervals (FRIs; years between fire) and mean FRIs (mFRIs) with 95% confidence intervals at local and regional scales. The Lake I4 core (RTS7U2, basal age 7046 cal year B.P.) shows shorter FRIs after ∼3000 cal year B.P. based on the >90 µm charcoal size fraction (regional burning), which coincides with Neoglacial cooling and decreasing moisture. A second higher-resolution core from nearby Kirk Lake (RTS5U3, basal age 743 years) captures short FRIs (mFRI = 198 (105–133) years), suggesting frequent burning compared to the late Holocene portion of Lake I4 core (mFRI = 378 (294–455) years). mFRIs from the larger charcoal size fractions (>125 µm; local burning) at both sites overlap with modern fire cycles observed in the region over the past 82 years. However, the Kirk Lake watershed burned more frequently than other sites in the region, likely related to abundant local shrub cover. These analyses suggest that tundra fires are related to climate variability, but local-scale feedbacks with vegetation can result in heterogenous burning, with implications for ongoing Arctic greening and warming.
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- Award ID(s):
- 1927772
- PAR ID:
- 10654439
- Publisher / Repository:
- Arctic Science
- Date Published:
- Journal Name:
- Arctic Science
- Volume:
- 11
- ISSN:
- 2368-7460
- Page Range / eLocation ID:
- 1 to 14
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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