The southern border of the Amazon region presents a peculiar type of forest called Seasonal Evergreen Forest, which has currently undergone several environmental impacts due to the agriculture frontier expansion from the Northern state of Mato Grosso. Due to the lack of studies on this type of forest, the objective of this study was to identify the floristic composition and phytosociological structure of the arborous component from a forest area in the Trairão Farm, Querência - MT, Brazil. The vegetation sampling was composed of the distribution of 200 quadrant-points in which the four individuals closest to each point, with DAP (diameter to height breast) equal or superior to 10 cm were considered. The total density of the sampled area was 728 ind./ha distributed into 49 species, 39 genera and 24 families. The species presenting the highest richness was Fabaceae (five species), followed by Burseraceae and Euphorbiaceae, with four species each, and considered as the richest in some Amazon forest areas. The species of highest Importance Value (IV) were Ocotea leucoxylon (Sw.) Laness., Xylopia amazonica R.E. Fr. and Myrcia multiflora (Lam.) DC., Chaetocarpus echinocarpus (Baill.) Ducke and Protium pilosissimum Engl., but did not present the same representativity as in other Seasonal Evergreen Forest area, evidencing structural differences within this phytogeographic unit. The majority of individuals from this community present slender size, with diameter ranging from 10 to 14.9 cm and height from 10.6 to 16.5 m. The Shannon index (3.17) may be considered as low in relation to the Amazon Forest in which the diversity is above 4.0.
Amazon region; floristic; phytosociology; Seasonal Evergreen Forest; Mato Grosso
