Diversity of naturally regenerating tree species in the overstorey layer of Larix kaempferi plantations and abandoned broadleaf coppice stands in central Japan

To consider the ecological restoration potential of plantations, we investigated the influence of stand age on naturally regenerated tree species diversity in the overstorey layer of Larix kaempferi (Lamb.) Carriere plantations in central Japan and compared the results with those of a naturally regenerated broadleaf forest (abandoned coppice). In aging plantations, although stand structure was more developed and tree species diversity tended to increase, species composition did not tend towards that observed in abandoned broadleaf coppice forests. The reasons appeared to be because few species were significantly and positively correlated with stand age, newly recruited species would not associate with abandoned coppice forests, and some of the tree species occurring in younger plantations would persist in older plantations. Changing in the species composition of the overstorey as stands age is therefore considered to be difficult, particularly since the species composition of naturally regenerated trees at an earlier stage of plantation development has a marked effect on the species composition later on. If the species composition of the studied plantations is to be altered to more closely reflect that of naturally regenerated forests in the region, then it may be necessary to implement supplementary management measures.