1. Modifications of Amazonian forests by pre-Columbian peoples are thought to have left ecological legacies that have persisted to the modern day. Most Amazonian palaeoecological records do not, however, provide the required temporal resolution to document the nuanced changes of pre-Columbian disturbance or post-disturbance succession and recovery, making it difficult to detect any direct, or indirect, ecological legacies on tree species.

2. Here, we investigate the fossil pollen, phytolith, and charcoal history of Lake Kumpaka, Ecuador, during the last 2415 years in c. 3-50 year time intervals to assess ecological legacies resulting from pre-Columbian forest modification, disturbance, cultivation, and fire usage.

3. Two cycles of pre-Columbian cultivation (one including slash-and burn cultivation, the other including slash-and-mulch cultivation) were documented in the record around 2150-1430 cal. yr BP and 1250-680 cal. yr BP, with following post-disturbance succession dynamics. Modern disturbance was documented after c. 10 cal. yr BP. The modern disturbance produced a plant composition unlike those of the two past disturbances, as fire frequencies reached their peak in the 2415-year record. The disturbance periods varied in intensity and duration, while the overturn of taxa following a disturbance lasted for hundreds of years. The recovery periods following pre-Columbian disturbance shared some similar patterns of early succession, but the longer-term recovery patterns differed.

4. Synthesis. The trajectories of change after a cessation of cultivation can be anticipated to differ depending on the intensity, scale, duration, and manner of the past disturbance. In the Kumpaka record, no evidence of persistent enrichment or depletion of intentionally altered taxa (i.e. direct legacy effects) was found but indirect legacy effects, however, were documented and have persisted to the modern day. These findings highlight the strengths of using empirical data to reconstruct past change rather than relying solely on modern plant populations to infer past human management and ecological legacies, and challenge some of the current hypotheses involving the persistence of pre-Columbian legacies on modern plant populations.

A sediment core was collected in July 2014 using a Colinvaux-Vohnout piston sampler (Colinvaux, De Oliveira & Moreno 1999) from 19.5 m water depth. The core sections were wrapped in the field, transported to Florida Institute of Technology, and stored at 4 °C. Samples (0.5 cm³) for pollen (n = 126) and phytoliths (n = 131) were subsampled at 5-20 cm resolution and samples for charcoal (n = 515) were subsampled at 1-5 cm resolution. Pollen samples were treated according to standard methodology (Fægri, Kaland & Krzywinski 1989), including 10% HCl, 10% KOH, 10% NaP₂O₇, sonic bath, acetolysis (9:1 ratio of (CH₃CO)₂O and H₂SO₄), and heavy liquid flotation (sodium metatungstate, density: 2.0-2.1 g/mL). Pollen samples were spiked with exotic Lycopodium spores for the calculation of pollen concentrations (Stockmarr 1971). Pollen samples were mounted in glycerol and a minimum of 300 terrestrial pollen grains were counted per sample. Phytolith samples were treated according to standard methodology (Piperno 2006), including H₂O₂, HCl, KMnO₄, and heavy liquid flotation (Bromoform (CHBr₃), density: 2.3). A minimum of 200 phytoliths were counted in each sample. Charcoal samples were prepared according to standard methodology (Whitlock & Larse 2001; McMichael et al. 2012), including H₂O₂ and filtering (160 µm size mesh).

References:

Colinvaux, P, De Oliveira, P & Moreno, E. 1999. Amazon: Pollen Manual and Atlas. Harwood Academic Press, New York.

Fægri, K., Kaland, P.E. & Krzywinski, K. (1989) Textbook of pollen analysis. The Blackburn Press, New Jersey.

McMichael, C., Piperno, D.R., Bush, M.B., Silman, M.R., Zimmerman, A.R., Raczka, M.F. & Lobato, L.C. (2012) Sparse pre-Columbian human habitation in western Amazonia. Science, 336, 1429-1431.

Piperno, D.R. (2006) Phytoliths: A comprehensive guide for archaeologists and paleoecologists. Alta Mira Press, Lanham, MD.

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

Whitlock, C. & Larse, C. (2001) Charcoal as a fire proxy., Tracking environmental change using lake sediments. Terrestrial, algal, and siliceous indicators. Eds Smol, JP, Birks, HJB & Last, WM. Kluwer, Dordrecht.

The Excel file includes fossil pollen, phytolith, and charcoal data from Lake Kumpak^a, Ecuador. Data are available in raw counts for pollen and phytoliths and as mm³/cm³ for charcoal. The data file includes four tabs: Site, Pollen, Phytolith, and Charcoal.

File: Lake_Kumpaka_Ecuador_pol_phy_cha.xls