|Budget Amount *help
¥3,300,000 (Direct Cost : ¥3,300,000)
Fiscal Year 1998 : ¥800,000 (Direct Cost : ¥800,000)
Fiscal Year 1997 : ¥2,500,000 (Direct Cost : ¥2,500,000)
Deciduous coppice forests dominated by Quercus serrata are widely distributed around cities and farm and mountain villages in Japan. Afforestation by conifers was actively made there during 1950's to 1970'. But recently the new trend towards natural reproduction by making full use of native broad-leaved tree species have been growing among people. The mother tree method and the shelterwood method have a number of advantages ; e.g. easily performed, enable to shorten the regeneration period and so on. Various fundamental studies and technical tests were carried out in order to examine applicability of these natural reproduction methods for Q.serrata. The canopy trees produced good seed crop almost every two years, bumper seed crop at intervals of 6 or 8 years. Larger number of mature seeds were supplied at years when the trees bore more seeds. Most of seeds fell right under tree crowns or near around them and collected mainly at low spots on the ground surface. The seed fall was followe
d by leaf fall and the leaves also collected in the same manner to cover seeds. So seeds could avoid desiccation damage. Seedlings showed , already at current year stage, high photosynthetic ability in leaves, 60 to 70 % of young trees, and the photoinhibition of photosynthesis was not observed. Daytime stomatal conductance of current year seedlings was kept relatively high even in non rain fall periods in summer, probably due to marked development of their root system. At the following year weeds and shrubs started to grow thick and suppressed certain parts of the seedlings. It appeared, however, that the regeneration of Q.serrata would succeed finally, if vigorous growth of bamboo grasses could be restricted artificially. Use of backhoe was extremely effective for removing under-ground system of bamboo grasses etc. Although soils were compacted by using such heavy machinery, the influence on photosynthetic performance and growth reaction of the seedlings was negligible.
4. 雑草木の刈り払いや除去をおこなわない限り,多くの稚樹は数年で雑草木に埋まる.しかし,各雑草木種の被度が同一でも,雑草木種により稚樹成長への影響が,異なっていた.最も強い被圧をもたらすのは,ササ類であった.ササ類の繁茂を抑制できれば,更新は成功するとみられ,小型バックホウによる地下茎除去がきわめて効果的であった. Less