Holocene vegetation, climate and fire dynamics in the Serra dos Órgãos, Rio de Janeiro State, southeastern Brazil

We analysed pollen and macro-charcoal from a sediment core representing the last 9840 cal yr BP, collected at 2003 m a.s.l. in a patch of upper montane Atlantic Rain Forest (UMARF) embedded in a campos de altitude (high-elevation grassland) matrix in the Serra dos Órgãos National Park, southeastern Brazil. From 9840 to 4480 cal yr BP, campos de altitude (CDA) was the dominant vegetation at the site, indicating that the climate was relatively cool and dry. However, pollen data document that UMARF was near the core site throughout the recorded Holocene. Relatively frequent high-magnitude fires occurred during the Early Holocene but became rarer in the Mid-Holocene after 4480 cal yr BP, when the climate became wetter. In the Mid-Holocene, UMARF and tree fern taxa became slightly more frequent at the site, but CDA vegetation continued to dominate most of the high-mountain landscape. A climatic change to wetter and warmer conditions during the last 1350 cal yr BP is evidenced by an increase in UMARF and even lowland forest taxa in our core, as well as the near complete absence of fire after this date.