Late Quaternary environmental dynamics in the Atacama Desert reconstructed from rodent midden pollen records

Abstract

In the past two decades, much has been learned about the late Quaternary climate history of the Atacama Desert with some details still unclear about the seasonality, timing and extent of wet and dry phases. Modern climate studies reveal that, far from exhibiting a unique pattern, seasonal precipitation originates from many sources and mechanisms. For the last 16 ka, we attempt to sort out these complexities in pollen records from four fossil rodent midden series spanning 22°–25°S in northern Chile. Widespread wet conditions prevailed during the late Pleistocene and early Holocene, particularly between 13 and 9 ka, evidenced by <400 m lowering of pollen zones (plant communities) compared to today. Regional differences in the timing and magnitude of this displacement may be related to the prevailing source (tropical/extra‐tropical) or mode (NNW/SE) of tropical precipitation through time. Wet conditions persisted well into the early Holocene, lasting ∼1–1.5 ka longer than previously suggested. The pollen record suggests extreme drying ∼8 ka, possibly associated with a northward shift of the Inter Tropical Convergence Zone, tracking minimum insolation values at subtropical latitudes during the austral summer. The establishment of conditions similar to today happened ∼4 ka. Copyright © 2017 John Wiley & Sons, Ltd.

Multiscale climate change impacts on plant diversity in the Atacama Desert

“…Blue line: Temperature estimated from the Antarctica Epica Dome C (temperature difference from the average of the last 1,000 years) (Jouzel & Masson‐Delmotte, ). Gray boxes: Central Andean Pluvial Event (CAPE) Includes CAPE I (17,500–13,800 cal year bp ) and CAPE II (12,700–8,500 cal year bp ) (De Porras et al., , modified from Quade et al., ). (b) Last 40 years.…”

“…Middens are deposited episodically and mostly discontinuously, nevertheless our ages distribution covers the different climatic events described in Figure a. After collection, middens were processed to identify macrofossils and pollen (results published in De Porras et al., ; Latorre et al., , comparisons in Figure ) and an unprocessed subsample of each midden was retained as a voucher specimen (used here to extract aDNA). Figure S1 shows photographs and a workflow summary for the aDNA recovery and analyses.…”

“…Number of taxa identified from the same fossil rodent middens (Cerros de Aiquina or CDA sites) using different techniques. Macrofossil data were obtained from (Latorre et al., ) and pollen data were obtained from (De Porras et al., )…”

“…Moisture or precipitation changes followed, with a period of increased precipitation (by around 500 mm), originally described as the Central Andean Pluvial Event (CAPE) in two distinct intervals (CAPE I: 15,900–13,800 and CAPE II: 12,700–9,700 cal year bp ) (Quade et al., ). Here, we follow the recommendation of a recent revision of different paleoclimate records (De Porras, Maldonado, De Pol‐Holz, Latorre, & Betancourt, ) from the central‐southern Atacama Desert, which defines widespread wet conditions from ~17,500–13,800 (CAPE I) and 12,700–8,500 cal year bp (CAPE II).…”

Late Quaternary records and chronology of environmental change in the Southern Hemisphere – a contribution to SHAPE

“…De Porras et al . () overcome this problem by analysing pollen records from rodent midden sequences at four sites, spanning the last 16 cal ka. Elevational shifts in vegetation over time inferred from the pollen records provide insight into changes in source and amounts of precipitation including the establishment of similar‐to‐present conditions at ∼ 4 cal ka.…”