Effects of reduced impact logging on the forest regeneration in the central Amazonia

Selective logging can alter the biota (presence of seed source) and distribution of resources (light and soil factors), modifying the performance of seedlings. To evaluate these effects on forest regeneration processes is of critical importance, since reduced impact logging (RIL) has been advocated as a potential tool for conservation. We describe the abiotic alterations caused by selective logging and examine the effect of disturbances on the abundance and performance of seedlings of seven trees species. To test long-term effects we evaluated the regeneration process in a chronosequence spanning 11-years after logging in which 144 plots were sampled, representing an area of 300,000 ha in the central Amazonia. Seedling performance was affected by habitat alterations caused by logging. Growth is enhanced in logged sites for up to three years after logging for all species. However, in five out of seven species, the mortality rates found in logged were higher than the ones in control sites up to 11 years after logging. For most species the presence of a seed source is the most important factor determining the number of regenerating individuals. This effect of dispersal limitation on seedlings can affect tree regeneration on logged areas, since no rules limit the number of individuals per species that can be harvested per hectare. Demographic responses to abiotic alterations resulting from selective logging affect tree species regeneration patterns, and in a long term can influence the structure of tropical forest communities. We concluded that over time the habitat becomes less suitable for species regeneration on logged areas. These results indicate that RIL can have more effects on tree regeneration than previously supposed. Methods to minimize these effects (mainly on survivorship rates) should be considered in future management plans.