Abstract
Following the Second World War, the number of Cupressaceae plantations in Japan increased, in accordance with government policy for the restoration of timber resources and conservation of soil and water. Currently, these even-aged plantations occupy approximately 44% of the forested area and 24% of the national land area of Japan. Although many of these plantations have become available as timber resources, there are several silviculture-related problems associated with reforestation following clear-cutting of these plantations. The abundant annual precipitation in Japan allows for dominance by competitive vegetation, which makes natural regeneration difficult and increases the cost of silvicultural operations during and after the planting of seedlings. Because the number of seedling producers has decreased, there has been little incentive to keep seedling production techniques up to date. Additionally, damage to planted seedlings by the overabundant sika deer (Cervus nippon) population has increased dramatically in the last dozen years or so. To determine how to overcome these difficulties, various studies are underway in Japan. For example, seedling studies have examined the relationship between seedling size and competitive ability with other species in reforested areas, and have led to the development of lower-cost systems to produce customized Cupressaceae seedlings, as well as measures to minimize transplanting damage to seedlings. Previous studies have shown that no-weeding operations might lower the risk of sika deer browsing seedlings, although this silvicultural countermeasure may potentially reduce seedling growth. Studies have also examined the types of physical protection against sika deer browsing that are most efficient. We must combine these findings into a unified silvicultural system for successful restoration via lower-cost plantations.
Highlights
L reforestation following clear-cutting of these plantations
A similar policy was undertaken after World War II; grasslands were reforested, and natural broadleaf tree forests were converted into Cupressaceae plantations, with some Pinaceae plantations of Japanese larch (Larix kaempferi Carrière) at higheraltitude regions and on Hokkaido and Sakhalin fir (Abies sachalinensis Mast.) on Hokkaido (1951–1986)
The area of conifer plantations increased from 49,300 km2 in 1951 to 103,500 km2 in 2007 and these even-aged plantations currently occupy approximately 44% of the forest area and 24% of the national land area of Japan (Forestry Agency 2010) (Fig. 3)
Summary
In terms of morphology and physiology, is a critical component of successful plantation establishment. A review of a large database of seedling survival in many species in North America (e.g., Douglas-fir and loblolly pine) showed that container seedlings are generally more tolerant to transplant shock and have higher survival rates in harsh environments than bare-root seedlings (Grossnickle and El-Kassaby 2016). A proper seedling production protocol, with specified growing conditions and quality control, must be established to develop a successful reforestation program in Japan Both stocktype traits and the conditions of the potential transplant site should be considered to maximize survival against transplant shock. Several studies have examined seedling performance based on species characteristics in relation to container cell volume, plant density, and nursery conditions in European and North American species (e.g., Douglas-fir, black spruce, western hemlock, longleaf pine, and cherrybark oak) (Landis et al 2010) These data were derived from long-term research on seedling stocktypes that started in the 1960s. Further research is needed to clarify the effects of cavity size on the physiological and morphological traits of seedlings of different species
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