Projection of the probability of local extinction of canopy tree species in forest landscapes

Abstract

Tree species are endangered mainly by the exploitation of old-growth forests, and in Japan by a change from traditional coppicing (Satoyama) to monoculture plantations. The protection of old-growth forest or the revival of traditional Satoyama management might avoid local extinctions. To evaluate these possibilities, we developed a model to project the dominance and probabilities of local extinction of tree species in deciduous forests by combining land-use change and canopy tree replacement matrices. The land-use change matrix represents the probability of land-use transition during a unit interval (25 years). We calculated the probabilities of transition among old-growth forest, immature secondary forest, mature secondary forest, conifer plantation, and pasture from historical records. The probabilities of canopy replacement in old-growth and secondary forests were estimated from canopy–understory associations. Changes in canopy composition after logging of old-growth and secondary forests and forest recovery following abandonment of clear-cut plantations and pasture were estimated from field data. Using the combined matrix model, we projected the abundance and probabilities of local extinction of 19 tree species under four scenarios: business as usual, forest protection, Satoyama (traditional coppice management), and Satoyama forest protection. Satoyama management increased the abundance of disturbance-dependent species but contributed little to the reduction of local extinction. Forest protection decreased extinction probabilities and the dominance of tree species did not change greatly. In particular, forest protection greatly decreased the local extinction probabilities of species with continuous recruitment in old-growth forest, such as Fagus crenata, F. japonica, and Acer mono, but Satoyama did not.