Interactive influences of distance from seed source and management practices on tree species composition in conifer plantations

Abstract

To examine which factors (i.e., distance from seed source and management practices) interactively affect habitat affinity, functional traits and strata (size categories) of naturally regenerated tree species in conifer plantations, we studied tree species composition in Cryptomeria japonica (sugi) plantations that differed in their management history and proximity to natural forests in central Japan. Although distance from natural forests (i.e., seed source) to plantations was an important variable for colonization of plantations by naturally regenerated trees, we found that the effects of management (e.g., number of rotations) were stronger than distance from natural forests. Interactive effects of management and distance from natural forests on species composition in plantations were observed. Some habitat affinity and functional traits, particularly seed dispersal traits of naturally regenerated tree species were related to this distance. Species composition of large and small saplings of naturally regenerated tree species in plantations located near natural forests resembled those of the tree layer of natural forests; however, the species composition in the tree layer in plantations was not similar. If such saplings successfully developed into the plantation canopy, the conversion of plantations would meet ecological restoration targets. Because this study showed that management variables strongly influence naturally regenerated trees in plantations, management decision-making for successful ecological restoration should consider not only distance from seed sources but also management practices.