Optimizing Strip-cutting Patterns for Sustainable Timber Production Under Spatial Constraints in Okinawa, Japan

Abstract

Increasing the self-sufficiency rate of wood has been one of the most pressing issues in Okinawa where more than 90% of wood used are imported either from other countries or from different prefectures. However, forests also provide an important habitat for forest dependent rare and endemic wildlife species in Okinawa. Therefore, sustainable timber production must be achieved by periodic timber extractions which ensures minimum impacts on habitats of those wildlife species. Strip-cutting which remove trees from a series of narrow clear-cuts leaving adjacent strips uncut have been suggested as a low impact timber extraction method, which have been introduced in several locations in Okinawa. However, this cutting system has only been conducted on experimental basis and is scattered, hence, it has not led to stable timber production. Carefully developed harvest schedule, which considers forest growth and spatial distribution of strips, are necessary to achieve efficient sustainable timber production. In this study, we developed strip-cutting scheduling model in order to control spatial distribution of strip cutting over the planning horizon. To illustrate how the proposed model assembles spatial information, and ultimately contributes to the study of strip-cutting schedule for sustainable timber production under spatial constraints, we apply our proposed model to a section of forest in Ishigaki Island, Okinawa and conduct a simple simulation analysis for two management scenarios. Our model explores spatial strip cutting patterns which prohibit timber extraction activities in designated areas set aside for wildlife species and leaves adjacent strips uncut.