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Abstract

Senna reliculata ('matapasto') is a woody pioneer which colonizes Amazonian whitewater floodplains. In open areas, especially those which have suffered a strong anthropogenic impact, Senna reticulata dominates over other woody and herbaceous species forming large, apparently monospecific stands. In the present study, stands of Senna reticulata which were two and six years old were inventoried in order to describe differences of species dominance and physiognomy. Senna reliculata dominated in the first years after establishment, representing 86.4 % of all individuals in the two year old plots and forming the canopy at 4-5 m height. In the six year old plots, Senna reticulata had only 28.4 % of all individuals, and the canopy at 7-8 m height was formed by 12 species. The vitality of Senna reticulata was low in the six year old stands. The trees had higher stems but very small crowns with few leaves, enabling the co-occurring slow growing, long-lived species to take over dominance. This study shows that Senna reticulata, although considered a noxious woody weed by the local people, has a restricted period of dominance and represents the initial phase of a successional sequence that leads to a diversity comparable to that of areas which have not suffered anthropogenic impact.