Impacts of logging on the structure of the native understory vegetation in an area of legal reserve

The objective of this study was to assess the impacts of logging, firewood (DBH < 30 cm) and logs (DBH >= 30 cm), on the structure of the native understory vegetation in an area of legal reserve planted with Eucalyptus saligna Smith., abandoned for 40 years. The three analyzed treatments were: CCV - conventional harvesting with mechanized extraction for firewood and for logs; CIR1 - reduced impact harvesting with mechanized extraction for firewood and for logs; and CIR2 - reduced impact harvesting for firewood associated with animal extraction and with mechanized extraction for logs. The variables for studies on effects of vegetation structure were: a) three classes of tree damages: intact, damaged and dead; and b) remaining basal area (m(2). ha(-1)). The reduced impact harvesting treatments resulted in the lowest tree mortality rates, CIR1 of 32% and CIR2 of 38%. CIR1 differed statistically from CCV that presented 49% of mortality. In the harvesting for firewood, the CIR2 that used animal traction in the logging caused a reduction of 10% of initial basal area of the understory settlement, statistically differing from CIR1 and from CCV that used mechanical logging and resulted in a reduction of 26% and 30% of basal area, respectively. After extraction of logs or the end of Eucalyptus wood harvesting, the CIR1 had the lowest basal area reduction rate of 26%; statistically differing from CCV that caused 43% reduction, while the CIR2 caused 30% reduction. Therefore, it is possible to minimize the negative effects using mitigating impact techniques and, finally, the reduced impact harvesting systems are the best alternatives to logging in abandoned stands of Eucalyptus and they are a viable forest management to turn them into areas of legal reserve.