The objective of this work was to contribute to a better understanding of the heterogeneity of the Semidecidual Seasonal Alluvial Forest. The results from a floristic-structural survey performed in an 1-ha plot classified as "Dense Forest", located at RPPN SESC Pantanal (Municipailty of Barão de Melgaço/ MT, Brazil - 16º45'S; 56º15'W) are presented. It was sampled 648 individuals ha-1, representing 42 species, 41 genus and 28 families; diversity index H'= 2.67 (var. 0.0067). The families with the highest diversity were Fabaceae (5 spp.), Moraceae (4 spp.), Meliaceae and Annonaceae (3 spp. each). Among the sampled species, 38 % were evergreen, 31% were deciduous and 26% were semi-deciduous. Of all the individuals, 12% were identified as semi-deciduous, 21 % were deciduous and 61% were evergreen. Of all the individuals, 63% were categorized as pioneer. The especies with the highest structural importance was Attalea phalerata (VI= 78.75) due to its high density (20% of the total sampled individuals), frequency (90%) and high basal area (21.15 m² ha-1). On second level of importance, Pseudobombax longiflorum and Guarea guidonia (VI= 36.93 and 36.14 respectively) were recorded. The results corroborate that the strong presence of Leguminosae representatives, as well as those of palm species seems to be a common element among FESD sites. In addition, Myrtaceae was the characteristic element of the more eastern sites and A.phalerata was the typical and differentiate element in the innermost sites,both represented by the studied area.
Diversity; Floristic; Phytosociology
