Tree species distribution in várzea forests of Brazilian Amazonia

Amazonian várzea forests are floodplains inundated by nutrient-rich white-water rivers occurring along the Amazon River. They are regularly flooded for up to 210 days per year by water columns of 10-15 m. Topographic variation results in different flooding amplitudes and durations along the flooding gradient, where the different tolerance to flooding of different plant species results in a vegetation zonation. We made a revision of literature about the vegetation composition of várzea floodplain forests of Brazilian Amazonia along the Amazon River. 22 studies were selected. Basing on the distribution of inventories which are concentrated in three main areas around three larger cities Belém, Manaus and Tefé, we classified the inventories into three regions: 1. Region A: Estuary region with flooding regime influenced by daily inundations linked to the tides. 2. Region B: Central Amazonia near Manaus. 3. Region C: Western part of Brazilian Amazonia bordering Peru and Colombia, including Tefé and the "Reserva de Desenvolvimento Sustentável Mamirauá". Summarizing the analysed species lists, 36 species were registered in all sampled regions including the estuary. The region A + C have 63 species in common, region B + C 143, and A + B have 50 woody species in common. In the inventories analysed here, an increase of species numbers from East to West can be confirmed but it is difficult to state whether this is not an artefact due to local sampling. Vertical zonation patterns are difficult to discuss due to the lack of comparable data. The inventoried areas are small, and there is an urgent need for a comparable floristic inventories spread over the whole basin. Destruction is spreading rapidly and the traditional use of the forests and its resources is changing to a destructive exploitation which already has changed much of the physiognomy and diversity of this unique ecosystem