Studies of the vegetation of a white-sand black-water igapó (Rio Negro, Brazil)

Summary The vegetation analysis of a Central Amazonian igapó, a forest under severe environmental stress — poor soil and seasonal flooding, reveals the existence of the dominant species Myrciaria dubia with a M.I.V. 75. The Shannon diversity index of this forest is 4.358 bits per individual, of which 75.73% is attributable to the evenness value. Species distributions change along the moisture gradient. Though many species exhibit the tendency of zonal distribution, the boundaries of zones are not abrupt. The authors suggest that species distribution is the result of physiological difference to flood tolerance. Further research should be directed to the comparison of flood tolerance of the plants which occur in the following three areas: permanent water-logged area, beach area with open canopy and upper area with closed canopy. The various adaptive strategies to seasonal inundation and drought, and the reproductive potential of the forest also merit further studies.