Changes in vegetation and human-environment interactions during the Holocene in the Lake Pueyrredon area (Southern Patagonia)

This paper reconstructs the vegetation history of the Lake Pueyrredon area during the Holocene and contextualizes the use of space and resources by hunter-gatherer groups according to palaeoenvironmental evolution. The pollen analysis of the Los Flamencos lake sequence is presented and integrated with local archaeological pollen data. Early Holocene vegetation consisted of a dwarf-shrub-grass steppe associated with cold conditions. From 7,600 cal bp a shrub vegetation with forest patches is inferred, suggesting a high moisture availability and possibly involving an eastwards displacement of the forest-steppe ecotone boundary. Human occupation, previously interrupted by the Hudson volcano eruption, and use of space is evident in this period. Between 6,600 and 5,400 cal bp an environmental change to drier conditions suggests a heterogeneous shrub steppe and the higher availability of floristic resources possibly used by hunter-gatherer groups. The predominance of shrub steppe with dwarf shrubs from 5,400 cal bp indicates more arid than current conditions, which correlates with a higher human-environment interaction related to changes in the lake configuration allowing new north-south circulation roads and vice versa, and major floristic resources availability. A decrease in dwarf-shrubs indicates a slight increase in moisture availability since 3,550 cal bp, suggesting a weakening of the westerly winds. The results indicate local and regional changes in vegetation linked mainly to moisture availability and Southern Westerly Winds fluctuations. The integration of pollen, archaeological and palaeogeographic information available and its comparison with other fossil records studied in Patagonia complement palaeoenvironmental reconstruction and explain the changes in a regional palaeoenvironmental framework.