Millennial-scale variability of vegetation and fire activity in a northern Cerrado driven by an east-west rainfall gradient during the Holocene

This paleoecological study investigates vegetation variability and fire regimes in Northeastern Brazil (NEB)'s Cerrado. We present high-resolution pollen and charcoal records from a palm swamp located in a Cerrado in Chapada das Mesas National Park, in the southwest of Maranhao State. The Vereda do Dodo sedimentary core is 187 cm deep and covers the past 6000 years. Our results show first the presence of an open cerrado between 6000 and 5200 cal yr BP with no fire activity and a gradual expansion of the palm Mauritia and woody cerrado after 5000 cal yr BP. This is synchronous with other studies of northeastern and central Brazil. At c. 4300 cal yr BP, sterile samples suggest a strong dry event, also recorded in other eastern NEB records. Frequent burnings lasted until 2600 cal yr BP, when fires stopped and Mauritia, arboreal cerrado, and gallery forest taxa expanded under increased moisture rates. The increase of southern hemisphere summer insolation and the warmer tropical Atlantic Ocean enhanced the monsoon system over eastern Amazonia and western NEB in agreement with speleothem records. Our study reveals that northern Cerrado biodiversity was very sensitive to SASM dynamics, a different pattern from eastern NEB vegetation and climate.