|Budget Amount *help
¥3,400,000 (Direct Cost : ¥3,400,000)
Fiscal Year 1993 : ¥400,000 (Direct Cost : ¥400,000)
Fiscal Year 1992 : ¥500,000 (Direct Cost : ¥500,000)
Fiscal Year 1991 : ¥2,500,000 (Direct Cost : ¥2,500,000)
1.Effect of the feeding by herbivorous insects upon the tree-growth
(1), Growth of Sweet gum, Liquidambar styraciflua, infested with the Giant silk moth, Caligula japonica. Onthe damaged year, annual stem growth were equal to 46-52% of the growth of preceding year, and on the next year of the defoliation, the stem growth were 85-90%. The effects of artificial defoliation during the growing season were not suffered great influences upon the growth of young Sweet gum.
(2), In the case of damages by the Cedar tussock moth, Caliteara argentata, to Japanese cedar, Cryptomeria japonica, the stem growth on the next year of the defoliation were 2.8-11.5% of the growth of preceding year. The defoliation by the Cedar tussock moth had greatest influences upon the growth of Japanese cedar.
2.Relations of artificial defoliation during the growing season and the withering of the treated trees.
Tree-species survived the all test trees were as follows ; Liquidambar styraciflua, Acer buergerianum
es withered one tree or more were as follows ; Pinus nigra, P.sylvestris, P.contorta, P.pinaster, P.banksiana, P.armandi, Cyclobalanopsis glauca, Castanopsis cuspidata, Idesia polycarpa, Eucommia ulmoides, Quercus serrata
3.Little-fall and its annual fluctuations in a Sweet gum and eastern white pine stand
(1), In a Sweet gum stand, Leaf-falls were 4.31-5.00ton/ha・y (4.71ton on an average).The faces of herbivorous insects were collected varied much from 23.0 to 2,366.3kg/ha・y and its amount was mainly composed by the feces of the Giant silk moth. The feces of other herbivorous insects except the Giant silk moth were weighed at 12.6-46.2kg/ha・y. Total littler-falls were summed up 4.80-6.52ton/ha・y (5.43ton). A sweet gum stand eaten by the Giant silk moth developed new leaves at about 2.0ton/ha soon a month after the defoliation.
(2), In a eastern white pine stand, annual leaf-litter were collected from 3.78 to 5.87ton/han・y(4.92ton). The feces of the herbivorous insedts were collected 70.5-272.8kg/ha・y(137.6kg). These faces were much a little than the feces obatained in various healthy forest stand, but that seemed to be ordinary level in the healthy pine stands. Less