Logging intensity effects on genetic diversity, effective population size, spatial genetic structure and gene flow in Araucaria angustifolia (Araucariaceae)

Araucaria angustifolia is an endangered species with more than 97% of its natural populations extinct. Logging of the species in the few remaining natural populations is highly restricted, though not readily accepted by farmers and logging companies. Consequently, political pressures have emerged for a return to logging of the species. Assessing the sustainability of such logging requires studies of a range of impacts on the remaining populations, including their genetic viability. We investigated the effect of two logging intensities (LI: 18.4 and 31.9% of trees) on genetic diversity, intrapopulation spatial genetic structure (SGS), effective population size (Ne), and pollen and seed dispersal in three A. angustifolia permanent sample plots (blocks) established in a remnant of Araucaria Forest in Brazil. Microsatellite analysis was performed for all adult and juvenile trees pre- and post-logging seedlings. After selective logging, the greatest loss of alleles and the greatest decrease in Ne were observed from the highest LI. Logging increased SGS, while the distance and patterns of pollen and seed dispersal were different for both pre- and post-logging scenarios, with pollen dispersed over greater distances than seed. Pollen dispersal distance post-logging and seed dispersal distance pre- and post-logging decreased with the increased distance between parents. After logging, Ne reduced from 28.8 (LI= 18.4%) to 30.5% (LI= 31.9%), and some alleles were lost. Under the conditions evaluated in this study, selective logging of A. angustifolia is not adequate. To achieve truly sustainable forest logging, new rules that combine higher minimum DBH, lower logging intensity and longer cutting cycles must be adopted. Furthermore, extensive genetic studies must be performed before logging any individual from a natural population.