Late Holocene climate dynamics and human impact inferred from vegetation and fire history of the Caatinga, in Northeast Brazil

Abstract

Holocene vegetation changes are good indicators of climate change/and or human impacts. The environmental history in the semi-arid region with Caatinga vegetation in Northeast Brazil has been still little studied. A 420 cm-long sediment core collected in a mire at the Catimbau National Park, State of Pernambuco, has been analyzed for pollen, spores, charcoal, and sedimentological characteristics. The core is dated by three AMS radiocarbon dates and is at the bottom of the core about 2800 cal yr BP old. Results indicate three different periods of sedimentological and environmental characteristics. The first period from 2800 to 2150 cal yr BP is characterized by the dominance of the pioneer tree Cecropia, and high charcoal amounts, indicative of strong environmental disturbances due to frequent fires. The vegetation compositions with less frequent ferns suggest the predominance of relatively dry conditions. In the following period between 2150 and 450 cal yr BP, the Moraceae-dominated forest with ferns suggesting wetter conditions. The increased occurrence of the Orbignya palm, as well as the bean Phaseolus, combined with abundant charcoal, suggest even stronger influence of Amerindians in the area. During the last period, after 450 cal yr BP, arboreal species were replaced by herbaceous taxa, indicating more open vegetation. The fire regime has been reduced. This evidence points to the return of drier conditions and the complete decline of the Amerindian population in the area, after the arrival of European colonizers.