STRUCTURAL EVOLUTION OF BRACATINGA STANDS IN CURITIBA METROPOLITAN REGION, PARANA, BRAZIL

The objective of this research was to study the structural evolution of tree species in stands of bracatinga, along twenty years. The bracatinga (Mimosa scabrella Bentham) is a short-lived pioneer species that characterizes its stands. Under the bracatingas it is formed an understory with other tree species which will replace bracatinga over the years and it is too treated as if it were bracatinga's firewood, when the area is submitted to clear cutting at every 7 years and bracatinga regeneration is again induced by burning the area. The succession process in stands of bracatinga has not been studied yet and is useful to identify the age when other trees species dominate the stands. The data for this research came from 320 sample plots measured between 1998 and 2011, distributed in stands of bracatinga aged 3 to 20 years. The DBH (diameter at breast height) and total height of all species with a DBH >= 5 cm were measured. It was observed that, at age 11, the set of others species outnumber bracatinga. At age 19 tree species already have a diameter distribution similar to that one of a forest in a more advanced stage. Generally speaking it was observed that after age 10, the stands of bracatingastart toshow a configuration of a desne pole stand.