Simulation of strip-gap arrangement in cedar plantations to regulate the light environment and competition between dwarf bamboo and beech seedlings

Abstract

Summary We estimate a suitable strip-gap arrangement in Japanese cedar (Cryptomeria japonica) plantations to promote the growth of beech (Fagus crenata) seedlings and control dwarf bamboo (Sasa kurilensis) in mountainous areas using a hemispherical model and United States Geological Survey Digital Elevation Model (DEM). Clarification was also sought on whether the gap arrangement should be altered with topography and original stand structure. Nine modelled plantations were established by combining tree inventory and DEM data from three C.japonica plantations. We simulated spatial and temporal variations in photosynthetic photon flux density in stands 5 years after strip-gap creation under six scenarios for each modelled stand and integrated the light responses of F. crenata seedlings and S. kurikensis into the model. Finer strip-gap mosaics with gap width narrower than half the tree height inhibit the growth of S. kurikensis and provide a wider area suitable for F. crenata growth. Our simulation indicated a suitable strip-gap arrangement should be based on the stand structure but not necessarily on topography. However, it indicated that the possible range of practical gap arrangements changed with topography. The decision-support model for gap arrangement used in this study combined with DEM data provides flexible gap creation options adaptable to specific plantations in mountainous areas.