The studies in the Ogawa Forest Reserve (OPR) were initiated by a group of plant ecologists and gradually expanded into a comprehensive project covering various aspects of biology, soil science, and silviculture. The project was integrated as part of the Forest Ecosystem Team under the BIO-COSMOS Program funded by the Ministry of Agriculture, Forestry and Fisheries. As the coordinators of the Forest Ecosystem Team, we are pleased that reports of the long-term studies carried out in the OFR are being published in this first volume on Japanese ecosystems in the Ecological Studies series. Scientists and researchers have made numerous contributions to the field of forest ecology