C. Nunes da Cunha  and W.J. Junk

The woody vegetation of the northern Pantanal of Mato Grosso near Poconé can be divided into Cerrado, Cerradão, and semi-deciduous and deciduous forests occurring on non-flooded habitats, and different types of floodplain forests occurring in periodically inundated habitats. An analysis of a 440-m long, 20-m wide transect crossing a levee at Cassange River, a right-hand affluent of Cuiabá River, showed 50 tree species. Of these, 12 species occurred only in areas of prolonged flooding, 24 species showed a wide distribution on the topographic gradient, and 14 species occurred only on dry habitats that become flooded for short periods only during extreme flood events. Species distribution on the flood gradient is shown, and the impact of the flood pulse on phenology and community structure is discussed. The low number of highly flood-adapted species is interpreted as the result of pronounced, long-lasting paleoclimatic dry periods. A broad ecological amplitude with respect to flooding seems to be the most efficient strategy of tree occupation in the Pantanal under actual hydrological and climatic conditions. Data from other inventories are used to present a general model of tree distribution in the northern part of the Pantanal of Mato Grosso.