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Pollen and charcoal from Tolhuaca National Park, south-central Chile

Cite this dataset

Abarzúa, Ana M.; Martel-Cea, Alejandra; González, Mauro E. (2024). Pollen and charcoal from Tolhuaca National Park, south-central Chile [Dataset]. Dryad. https://doi.org/10.5061/dryad.msbcc2g5p

Abstract

Aim: Few paleoenvironmental studies have been performed in Araucaria-Nothofagus forests, which are highly vulnerable to ongoing threats from climate change and anthropogenic activities. The primary goal of this work is to reconstruct past environmental changes related to fire disturbances over the last 1800 years in Tolhuaca National Park, Chile.

Location: Tolhuaca National Park, Araucanian region (38.2°S; 71.8°W), Northwestern Patagonia, Chile.

Taxa: Araucaria araucana (Araucariaceae), Nothofagus spp. (Nothofagaceae).

Methods: We completed charcoal and pollen analyses to create two new paleoecological records that span 1800 years. We compared the lake-based reconstruction with the available local tree-ring fire scar chronologies from the last 430 years. Using these data, we compute forest index changes, biomass burning trends, and compare with estimates of archaeological radiocarbon density. We place our inferences with context of published regional paleoclimatic proxies from the Patagonian-Andean region.

Results: Our results showed that fire activity was higher than present between 200 and 1500 CE, with peaks around 200-400 CE and 1100-1500 CE. Periods with high fire activity are associated with reduced forest cover, as Araucaria declined when mixed-severity fire regime occurred for extended periods. Pollen assemblages suggested a shift from dry to wet climate conditions at 1500 CE, and from 1750 CE onward, the arrival of exotic species reflected the land-use changes related to forest clearance and transhumance practices.

Main conclusions: The paleoenvironmental reconstructions showed changes in vegetation, fire, and climate over the past 1800 years in TNP. Wildfires have been the main disturbance process modifying the vegetation structure in the Araucaria and Nothofagus forests. Since 1750 CE intensive post-Hispanic land-use changes (forest clearances by fire and logging) took place in the study area, reducing the native vegetation cover. Climate variability, modulated by SAM-like and ENSO-like conditions, influenced the fire activity (availability and flammability of fuels), concomitantly with high archaeological density. The recent (after 2000 CE) increase of catastrophic wildfires may negatively affect the conservation strategies of Araucaria-Nothofagus forests.

README: Pollen and charcoal from Tolhuaca National Park, south-central Chile

Research article:

Fire-climate-human dynamics over the last 1800 years in the mesic Araucaria-Nothofagus forests.

Authors: Martel-Cea, Alejandra (1,2,3), Abarzúa, Ana M. (2,4), González, Mauro E. (5,6,7), Jarpa, Leonora (2), Hernández, Marjorie (2).

Journal: Journal of Biogeography

Year: 2024

DOI: 10.1111/jbi.14839

Corresponding author: anaabarzua@uach.cl

Affiliations:

(1) Corporación Centro de Estudios Avanzados en Zonas Áridas, La Serena, Chile

(2) Instituto Ciencias de la Tierra, Ciencias, Universidad Austral de Chile. Valdivia, Chile

(3) Laboratorio Natural Andes del Sur, Universidad Austral de Chile. Valdivia, Chile

(4) Núcleo de Estudios Transdisciplinarios del Cuaternario del Sur de Chile (TAQUACh), Universidad Austral de Chile. Valdivia, Chile

(5) Instituto de Conservación Biodiversidad y Territorio, Facultad de Ciencias Forestales y Recursos Naturales, Universidad Austral de Chile. Valdivia, Chile

(6) Centro de Ciencia del Clima y la Resiliencia (CR2). Santiago, Chile

(7) Centro del Fuego y Resiliencia de Socioecosistemas (FireSES), Universidad Austral de Chile. Valdivia, Chile

DATASET: Pollen and charcoal from Tolhuaca National Park, south-central Chile.

https://doi.org/10.5061/dryad.msbcc2g5p

The dataset contains the palynological and charcoal sedimentary records from two lakes in the Tolhuaca National Park located in the western Andes Cordillera, northern Patagonia. Data cover the past 1800 years in Verde Lake and the 1100 years in Malleco Lake.

Location of the lakes:

Verde Lake: 38.213896°S; 71.734825°W, 1394 m a.s.l.

Malleco Lake: 38.215660°S; 71.822219°W, 893 m a.s.l.

Description of the data and file structure

Two Excel files (xls) that contain the raw data pollen, including the taxa, depth, chronology, and Lycopodium-tracer information per sample, and the charcoal counts along with the volume of sediment, depths, and chronology per sample. Both pollen and charcoal records were analyzed in the core "VERD01" of Verde Lake, and the core "MALL09" of Malleco Lake.

"TolhuacaNP_Verde_Lake.xls" file contains two spreadsheets:

Sheet "Pollen Verde Lake":

  • Column A: name of variables
  • Column B to W: 22 sediment samples.
  • Row 1: "Depth (cm)" corresponds to the depths of the 22 samples in the sediment core.
  • Row 2: "Age (Common Era)" is the estimated age of each sediment sample. It is equivalent to the Anno Domini -AD- years.
  • Row 3 to 83: the raw counts of 81 pollen/spore morphotypes of the Verde Lake.
  • Row 84: counts of charcoal microparticles from pollen slides.
  • Row 85 to 88: contains the information of the tracer/spike Lycopodium clavatum to compute pollen, spore, and charcoal microparticle concentrations.

Sheet "Charcoal Verde Lake":

  • Column A: "Depth (cm)" contains the depths of 112 analyzed samples of the core.
  • Column B: "Age (yr cal BP)" correspond to the estimated age of each sample in calendar years before present. 0 yr cal BP is the year 1950 CE.
  • Column C: "Volume (cm3)" is the wet sediment volume of each sample for charcoal analysis.
  • Column D: "Charcoal counts (>125µm)" correspond to the raw counts of charcoal macroparticles larger than 125 µm.

"TolhuacaNP_Verde_Malleco.xls" file constains two spreadsheets:

Sheet "Pollen Malleco Lake":

  • Column A: name of variables
  • Column B to Y: 24 sediment samples.
  • Row 1: "Depth (cm)" corresponds to the depths of the 24 samples in the sediment core.
  • Row 2: "Age (Common Era)" is the estimated age of each sediment sample. It is equivalent to the Anno Domini -AD- years.
  • Row 3 to 105: the raw counts of 103 pollen/spore morphotypes of the Malleco Lake.
  • Row 106: counts of charcoal microparticles from pollen slides.
  • Row 107 to 110: contains the information of the tracer/spike Lycopodium clavatum to compute pollen, spore, and charcoal microparticle concentrations.

Sheet "Charcoal Malleco Lake":

  • Column A: "Depth (cm)" contains the depths of 103 analyzed samples of the core.
  • Column B: "Age (yr cal BP)" correspond to the estimated age of each sample in calendar years before present. 0 yr cal BP is the year 1950 CE.
  • Column C: "Volume (cm3)" is the wet sediment volume of each sample for charcoal analysis.
  • Column D: "Charcoal counts (>125µm)" correspond to the raw counts of charcoal macroparticles larger than 125 µm.
Sharing/Access information

For additional information, please contact to:

Ana M. Abarzúa: anaabarzua@uach.cl

Alejandra Martel-Cea: jmartel.cea@gmail.com

Methods

Chronology: Two sediment cores were collected in Verde (112 cm) and Malleco (120 cm) lakes using an UWITEC gravity corer. Radionuclide measurements using a gamma spectrometer were performed to estimate the 210Pb, 226Ra (to support 210Pb activity), and 137Cs activities on the first 20 cm). In addition, AMS radiocarbon dating was performed in both lakes. Radiocarbon ages were calibrated using the SHCal20 curve (Hogg et al., 2020). The age-depth models were computed using an integrated chronology based on 210Pb, 137Cs, and 14C dates through Bayesian analyses in “rPlum” package (Aquino-López et al., 2018; Blaauw et al., 2020) in R platform.

Charcoal analyses: To infer fire regime, macroscopic (>125 µm) charcoal fractions were analyzed in Verde and Malleco cores. 2 cm3 of sediment were taken at 1 cm intervals for the length of the core, sieved through 125 μm and 250 μm screens, following the methodology outlined by Whitlock and Larsen (2001). 

Pollen analyses: Verde and Malleco cores were subsampled for 1 cm3 (Verde) and 2 cm3 of sediment (Malleco) at discrete 2 to 5 cm intervals. The samples were analyzed using conventional procedures (Faegri & Iversen, 1989). To calculate pollen concentration and accumulation rate, two tablets of Lycopodium clavatum were added to each sample (Stockmarr, 1971). Pollen identification was carried out using a modern reference collection (Palynology Lab-UACh) and palynological keys (Heusser, 1971; Markgraf & D'Antoni, 1978).

References:

Aquino-López, M. A., Blaauw, M., Christen, J. A., & Sanderson, N. K. (2018). Bayesian Analysis of 210Pb Dating. Journal of Agricultural, Biological and Environmental Statistics, 23(3), 317-333. doi:10.1007/s13253-018-0328-7

Blaauw, M., Christen, J. A., & Aquino-López, M. A. (2020). rplum: Bayesian Age-Depth Modelling of '210Pb'-Dated Cores. R package version 0.1.4.  https://CRAN.R-project.org/package=rplum

Faegri, K., & Iversen, J. (1989). Textbook of pollen analysis. Londres: John Wiley & Sons Ld.

Heusser, C. J. (1971). Pollen and spores of Chile: Modern types of the Pteridophyta, Gymnospermae, and Angiospermae. Tucson: University of Arizona Press.

Hogg, A. G., Heaton, T. J., Hua, Q., Palmer, J. G., Turney, C. S. M., Southon, J., . . . Wacker, L. (2020). SHCal20 Southern Hemisphere Calibration, 0–55,000 Years cal BP. Radiocarbon, 62(4), 759-778. doi:10.1017/RDC.2020.59

Markgraf, V., & D'Antoni, H. L. (1978). Pollen Flora of Argentina. Modern Spores and Pollen Types of Pteridophyta, Gymnospermae and Angiospermae. Tucson: The University of Arizona Press.

Stockmarr, J. (1971). Tablets with spores used in absolute pollen analysis. Pollen spores, 13, 615-621. 

Whitlock, C., & Larsen, C. (2001). Charcoal as a proxy fire. In J. P. Smol, H. J. B. Birks, & W. M. Last (Eds.), Tracking Environmental Change Using Lake Sediments: Terrestrial, Algal, and Siliceous Indicators (Vol. 3, pp. 75-97). Dordrecht, The Netherlands: Kluwer Academic Publishers.

Funding

Fondo Nacional de Desarrollo Científico y Tecnológico, Award: 1171400, ANID

Fondo Nacional de Desarrollo Científico y Tecnológico, Award: 1201528, ANID

Fondo Nacional de Desarrollo Científico y Tecnológico, Award: 1231573, ANID

Fondo Nacional de Desarrollo Científico y Tecnológico, Award: 1231344, ANID

Fondo Nacional de Desarrollo Científico y Tecnológico, Award: 3220525, ANID