Impacts of portable-sawmill logging on stand structure and regeneration in the lowland forests of West New Britain, Papua New Guinea

Abstract

Summary Small-scale portable-sawmill logging, an option for reduced—impact logging, is promoted across Papua New Guinea by NGOs as a sustainable development mechanism for village communities. It can provide a technically feasible tool for landholders to manage their commercial forest resources rather than selling logging rights to international companies. Despite over 20 years of operational practice, however, there has been little research on the effects of portable sawmilling or its silvicultural effectiveness. This study investigated the effects of well-planned and controlled portable-sawmill logging on stand structure and regeneration in lowland hill forest at Kilu in West New Britain. Logging effects were compared with natural changes in unlogged forest. Tree diameter increment, tree health and stem mortality were assessed for a 1-ha logged stand and a 1-ha unlogged stand over 29 months. Regeneration was assessed within the logged stand and in three logging gaps over 61 months. Portable-sawmill logging, harvesting 1–2 trees ha−1, caused 1–6% of the ground area to be heavily disturbed. The logging gaps promoted abundant regeneration of primary and secondary species. Early regeneration was dominated by secondary species (61%), but after 61 months primary species became dominant and the secondary species accounted for only 9% of the juvenile population. Impacts in this study were small when compared with those found by studies of conventional industrial logging in PNG, but the differences were less marked when compared with conventional logging at similar harvest intensities elsewhere. A slightly higher harvest intensity warrants consideration to reduce the impact per stem harvested.