The combined effects of tree shelters, large stock and vegetation control on the early growth of conifer seedlings

摘要

Tree shelters are effective in enhancing early survival and growth and protecting planted seedlings against herbivory by mammals; they are, however, expensive. In order to be cost-effective, we need to employ silvicultural practices that maximize the benefits of using tree shelters. Thus, this study examined whether tree shelter effects on early seedling growth are enhanced by the combination of large stock and vegetation control, based on a three factor split-plot experiment for the first three years after planting the seedlings out in a fenced plantation of Japanese cedar (Cryptomeria japonica). Vegetation control involved spot and strip weeding to reduce labor costs. The experiment demonstrated the great effect of tree shelters on enhancing the early height growth of seedlings. At the end of the third growing season, sheltered seedlings were 1.5 times taller than unsheltered seedlings on average, and approximately two-thirds of sheltered seedlings had exceeded the browsing height of deer, while unsheltered seedlings had not. Using large stock and employing vegetation control also positively affected seedling height. However, combining these treatments with tree shelters intensified the positive effects on seedling height, and shortened the period during which the leader shoots of seedlings would be unprotected from the browsing without fencing. The present study thus reveals that the combination of tree shelters, large stock and vegetation control is effective in maximizing the benefit of tree shelter installation.