The study was carried out on the gallery forest of the Bacaba Stream (14º41'S and 52º20'W) in Nova Xavantina-MT. It evaluated the changes in the structure of the vegetation from 1999 to 2006. In 1999, it was delimited 141 permanent plots in three portions of the gallery forest (upper, middle and lower), in a topographic gradient, and all individuals with breast height circumference > 15cm were measured. In the 2006 inventory, it was sampled 135 species, 113 genera and 49 families. The hierarchical position of the species showed significant changes in comparison to 1999. In the upper portion the most important species (IV) were: Astrocaryum vulgare, Diospyros guianensis and Calophyllum brasiliense. This portion could have been the most affected by the fire which occurred in 2001 inasmuch as one typical species of anthropic system occupied the first VI place. In the middle, the most important species in 2006 were: Aspidosperma subincanum, Tetragastris altissima and Hymenaea courbaril. In the lower, only Mauritia flexuosa maintained the same hierarchical position in the previous hierarchical inventory, the greatest hierarchical change was presented by the pioneer species, suggesting a vegetation closure. Of the 10 species with the greatest IV in 2006, none was common to the three forest portions. Distinct vegetation structure traits among areas geographically so close may be related to environmental heterogeneity. Changes in IV recorded in species of the three forest portions reinforce the idea that this one presents a high dynamics.
Astrocaryum vulgare; Environmental heterogeneity; Riparian forest
