Pollen representation and successional vegetation change on the sandstone plateau of Araracuara, Colombian Amazonia

The floral composition of the vegetation on the sandstone plateaus near Araracuara (Colombian Amazonas) was studied on the basis of 92 vegetation relevees. We compared the vegetation data with samples of the modern pollen rain in the 18 relevees that had non-barren pollen samples. By using the association index of Davis [Rev. Palaeobot. Palynol. 40 (1984) 295–315] and correspondence analysis, we evaluated to which degree pollen spectra reflect the actual vegetation. Rain forest taxa appeared overrepresented in the pollen rain on the sandstone plateau. Poaceae, Xyris, Cyperaceae, and Melastomataceae showed highest correspondence between pollen rain and measured vegetation cover, whereas Bonnetia, Bromeliaceae, and Ochnaceae showed an intermediate level of accuracy. Pollen analysis of a 25-cm sediment core, reflecting vegetation changes on the Araracuara sandstone plateau during the latest Holocene cm, showed a transition from open Rapateaceae-dominated vegetation to a Bonnetia martiana-dominated scrub. Successional stages in the pollen record were interpreted as discrete vegetation communities in the field, all occurring at present day as part of a mosaic-like vegetation. The pollen record included a substantial number of genera and families in which C 4 and CAM physiological pathways are common.