SOIL NUTRIENTS AND VEGETATION STRUCTURE IN A NEOTROPICAL SEASONAL WETLAND

The Pantanal is a large and diverse wetland whose main attribute is the flood pulse that alters soil nutrients and contributes to spread an invasive tree (Vochysia divergens Pohl) for more than four decades forming monospecific stands (locally known as Cambarazal). Our goal was to investigate soil nutrients and vegetation structure in a seasonal flooded forest dominated by Vochysia divergens Pohl in the Northern Brazilian Pantanal. There was an increasing of H+Al, H, OM, S, P, Al and CEC concentration after flooding, but only Fe showed a significant increasing. There was a decreasing of pH, Cu, Zn, Mg, Ca+Mg and sand values after flooding, but only values of Mn, clay and silt showed a significant decreasing. There was no variation in concentration of B and K after flooding. We found 14 species distributed in 13 families. Vochysia divergens had the highest abundance followed by L. parvifolia and M. elliptica. The mean diameter was 28.36 cm, density was 839.98 individuals. ha(-1), and average basal area was 66.16 m(2). ha(-1). The plant community had a negative diameter distribution while Vochysia divergens population had a Gaussian distribution. The diversity was higher with less Vochysia divergens dominance. Thus, flooding affected soil nutrients and dominance of invasive species affected species distribution and diversity in a Neotropical seasonal wetland.