Evaluating forest management status across ownership types based on stand structure typology for sustainable use in conifer plantations

Effective forest resource management is required not only to sustain harvests but also to promote ecosystem conservation. However, the final decision-making authority for forest management lies with the landowner, and policies promoting resource management must also consider the characteristics of forest conditions under each ownership type. In this study, we used National Forest Inventory (NFI) data to determine the current structures of Japanese cedar plantations, as well as differences among ownership types. The basal area of cedar trees and tree species diversity were calculated, and cluster analysis identified four distinct clusters: high-mixed, low-mixed, intensively managed, and dense plantation forests (PF). Notable relationships emerged between ownership and cluster types. Canopy stratification, the number of standing dead trees, and number of naturally regenerated trees differed significantly among the clusters. Furthermore, national forests had considerably more high-mixed PF (characterized by high species diversity and a mix of planted and naturally regenerated trees), consistent with the implementation of successful diversification. Community forests exhibited more intensively managed PFs, signifying effective management resulting from communal efforts and economies of scale. Individually owned forests were predominantly dense PFs, often reflecting under-managed conditions with high tree density, potentially owing to factors such as aging owners and low timber prices. Stand structure appears to be influenced by long-term forest management practices and site-environmental factors. Stand structure evaluation using NFI data could help monitor and evaluate progress in achieving the policy goal of converting monospecific PF into more diversified planted forests. • Cedar plantation forests were classified by BA of planted trees and tree species diversity. • The composition of stand types differed among the ownership types. • National forests had more high-mixed stands than other ownership types. • Common and individually owned forests were intensively-managed and dense, respectively. • Stand structure may reflect long-term management and site conditions.