Pollen-based characterization of montane forest types in north-eastern Brazil

Abstract

Surface soil samples were collected in three mountainous massifs in north-eastern Brazil to characterize the different vegetation types according to their respective pollen assemblages. Complementary approach between pollen and vegetation data shows that the pollen rain accurately reflects the following three main forest types: i) a dense ombrophilous forest (or tropical moist broadleaf forest) characterized by Myrtaceae associated with high percentages of Miconia, Guapira, Ilex, Moraceae-Urticaceae undif. or Byrsonima, ii) a seasonal semi-deciduous montane forest characterized by an increase of Arecaceae associated with Fabaceae-Mimosideae, Myrtaceae, Piper, Cecropia, Urera and Mitracarpus, and iii) a seasonal deciduous forest dominated by Fabaceae-Mimosideae and Arecaceae tree taxa associated with Alternanthera, Cyperaceae and Mitracarpus. Using of botanical data from several plots of ombrophilous forest, in which several surface soil samples have been collected, allows to roughly estimate the over- and underrepresentation of pollen taxa relative to their floristic abundance. Furthermore, distribution of surface soil samples at different altitude and mountain sides also allows to characterize vegetation variation according to several environmental parameters. The precipitation increase with altitude is confirmed as the main environmental factor controlling vegetation distribution. However, the forests located close to the crest with a proportion increase of pollen taxa characteristic of heliophilous and pioneer trees (Alchornea, Miconia, Clusia), are also influenced by changes of edaphic conditions. In addition to provide useful information in under standing of fossil pollen records, this approach improves our understanding of the ecosystem functioning in mountainous massifs in north-eastern Brazil. A useful knowledge for conservation or restoration purposes.