Modern pollen-vegetation-climate data set based on surface and rodent midden samples from the Atacama Desert (Chile) and its potential application to Late Quaternary reconstructions

DE PORRAS, M.E.; GONZÁLEZ, L.A.; MALDONADO, A.

Berna

Congreso; XXVIII INQUA Congress; 2011

The palaeoecological and palaeoclimatical dynamics of the Atacama Desert (Chile) during the last 50,000 yrs has particularly been inferred from the combined analysis of pollen and plant macrofossils from fossil rodent middens. However, the actual meaning of the fossil pollen assemblage changes in vegetation and climate terms could improve if the modern relationships between them were better understood. The present study therefore aims to establish the pollen-vegetation-climate relationships at the arid and semiarid areas of northern Chile (18°-29°S) based on the development of a two-part modern pollen data set including surface and rodent midden samples. Surface pollen samples were collected along six elevational climatic west-east transects at 18°, 20°, 23°, 25°, 28° and 29°S on the western slopes of the Andes whereas the modern rodent midden samples along three of these transects and random sites over the study area. Given the biotic origin of the rodent midden pollen assemblages, pollen taphonomy was complementarily studied. Both modern pollen data sets represent the different vegetation belts (Asteraceae and Adesmia scrub, Prepuna, Puna and High Andean steppe) at the western slope of the Andes as well as their latitudinal heterogeneity reflecting therefore the climatic gradient (precipitation mainly). However, the subsets show some differences related to the diversity and the anemophilous-enthomophilous pollen types balance that provide complementary information to picture the vegetation composition and physiognomy. Even though the actual potential of the modern data set needs to be evaluated, the results of the present study indicates that the two-part (surface and rodent midden) modern pollen data set is the best option to interpret the Atacama Desert pollen record in vegetation and climatic terms.