Effects of the reduced impact logging on natural regeneration in a terra firme dense forest in the municipality of Paragominas in Brazilian Amazonia

The motivation for this study was the scarcity of information on ecological sustainability of natural forests in areas affected by logging. The objective was to find out if there is any difference in regeneration between the unlogged area and the logged area; regeneration among years after logging; and to evaluate the capacity of the natural regeneration on recovery of the floristic composition and structure of the logged forest. Natural regeneration was evaluated in three areas in different occasions (2000, 2003 and 2006) over a seven-year period at Rio Capim forest management unit, in the municipality of Paragominas, Para state. Data were collected in gaps, primary and secondary skid trials, and log decks and in the remaining forest, considering individuals from 2.5 cm to 10.0 cm diameter. Richness, abundance, diversity, evenness and floristic similarity were evaluated. Changes occurred in the floristic composition and abundance of individuals in DBH 2.5-10.0 cm, in the seven-year study period, mainly in the primary skid trials and log decks. In the remaining forest, dynamics of species and individuals was higher for shade-tolerant species, but in gaps, skid trials and log decks pioneer species were dominant. In the log decks and skid trails the abundance of individuals with DBH greater than 2.5 cm was very low. Natural regeneration in areas opened by logging showed only a few timber species with commercial value being influenced by the remaining forest. Therefore, one can suggest that seedlings (DBH < 2.5 cm) of natural regeneration of commercial species must be assisted by post-harvesting silviculture; and seedlings produced in nurseries must be planted in gaps to guarantee a reasonable stock of commercial timber species for future harvests.