To clarify the effect of the gradient in inundation duration and substrate particle size composition with elevation on the growth of Salix gracilistyla seedlings, we compared tree height, root depth, dry weight, and shoot/root biomass allocation of current-year seedlings at several elevations above the waterline on a gravel bar along the Miya River, Japan. Low dry weight at low elevations, where the inundation duration exceeded half of the growing season, suggests that the long inundation duration reduced seedling growth. Flooding disturbance also suppressed seedling growth at low elevations. Seedlings had high tree height, deep root depth, and low TR (shoot/root biomass) ratio at high elevations that were inundated for several days only during the growing season. The water retention of substrate at high elevations was higher than that at low elevations because of a higher proportion of small-diameter substrate. Seedlings at high elevations could endure drought because of the higher proportion of belowground tissue and deeper root depth than seedlings at low elevations. The inundation duration, substrate type, and disturbance intensity differed among elevations above the waterline, affecting the growth of S. gracilistyla seedlings.

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Suitable habitats for beech (Fagus crenata Blume) forests in the year 2100 were predicted in Shirakami Mountains, using a classification tree model and two climate change scenarios (RCM20 and CCSR/NIES), Possible future changes of the forests were discussed. According to the predictive distribution model ENVI, developed with four climatic and five land variables, major controlling factors for the forest distributions were warmth index (WI) and winter precipitation (PRW). Since PRW shows little changes under the two climate change scenarios, WI is the major factor controlling the forest distributions in the future. The suitable habitats for the forests (probability≥0.5) in 2100 were predicted to shrink from the current 95.4% to 0.6% (RCM20) or 0% (CCSR/NIES). Elevation equivalent to the warmth index (WI) of 85.3, that is the lower range limit for F. crenata dominant forests, currently exist at 43 m a.s.l.; however, this will shift upwards in 2100 at 588 m (RCM20) or 909 m (CCSR/NIES). Judging from the field and literature surveys, altitudinal range for F. crenata dominant forests in the study area was between 260 and 1,070 m. Forest management-plan maps showed that c. 80% of the forests in the heritage area are between 150 and 200 years old. This indicates that many F. crenata canopy trees will be mature or senescent in 2100. Temperature increase in the lower range limit of the forests would cause F. crenata tree death and density reduction, and cause the growth of other deciduous, broad-leaved trees such as Quercus crispula and Q. serrata.

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In cold regions with snowfall in Japan, unsuccessful Cryptomeria japonica plantations are often intended to convert into more natural forest in recent years. To improve such a practice, we examined effects of weeding frequency (initial 10-years, vs. only initial 3-years) on density and growth of planted Fagus crenata, the most representative species in primeval forests, and naturally colonized broadleaved species. Although planted F. crenata was suppressed by colonized species, the mortality was lower in the infrequent site (TE) than in the frequently weeded site (WD). The mean diameter at breast height and crown diameter of the F. crenata of 8 year-old were larger in WD, but tree height was significantly large in TE. Moreover, the rate of snow pressure damage was higher in WD. Regarding the colonized broadleaved species, Betula maximowicziana and B. ermanii disappeared completely in WD in the study period, probably because of their sensitivity to aboveground cuttings. Only Prunus grayana, a species with high sprouting ability, was remained in the lower canopy layer. In contrast, in TE, these three species were established with F. crenata, forming the stratified canopy structure. We strongly recommend reducing the weeding frequency to restore natural stand characteristics in the conversion management in this region.

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The Forestry Department of the Ise Shrine is planning to produce timbers in the Ise Shrine Forest to rebuild the temples for the Shikinen Sengu Ceremony held every 20 years. Thus, this study proposes a stand density control system for the sustainable production of large timbers through the application of a system yield table to this forest. A system yield table known as the Local Yield Table Construction System (LYCS) was used to predict tree growth with the parameters newly introduced from the growth data of Chamaecyparis obtuse in the Kishuu area and the Ise Shrine Forest. We estimated the mean DBH and mean height of 35∼100 year-old trees assuming the specific management scheme involving long rotation and low density control. The LYCS produced a good fit to the actual growth and suggested a possible application to various thinning strategies. In addition, the LYCS was successfully adapted for the Shrine Forest in terms of various settings such as density control. Finally, we proposed a thinning plan for the sustainable production of timbers for the Shikinen Sengu Ceremony, including harvesting costs and labor availability.

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Male sterile sugi (Cryptomeria japonica D. Don) trees, “Shindai 1,” “Shindai 5,” were found in Niigata Prefecture, Japan. There were no significant differences in the appearances of male flowers and needles between these trees and the common wild type. We investigated the cyiological characteristics and inheritance of the male sterility trait in Shindai 1 and Shindai 5. We also determined the differences between Shindai 1, Shindai 5 and another male sterile tree, “Toyama MS”. Microsporogenesis in Shindai 1 and Shindai 5 produced normal microspores, but the microspores began to contract and clump. In the pollen dispersal season, the microspores agglomerated. Degeneration of microspores in Shindai 1 and Shindai 5 are different each others and also differ from that in Toyama MS in which microspores collapsed after expansion. All F₁ seedlings obtained from Shindai 1 and Shindai 5 produced pollen in male flowers, but F₂ seedlings segregated into 75% fertile and 25% sterile seedlings. Backcrossed seedlings obtained from Shindai 1 segragated into 50% fertile and 50% sterile seedlings. Moreover, seedlings obtained from a cross of Shindai 1 and Toyama MS F₁, Shindai 5 and Toyama MS F₁, Shindai 5 and Shindai 1 F₁ had only fertile male flowers. The male sterility trait in Shindai 1 and Shindai 5 are nuclear sterility controlled by a pair of recessive genes, and the male sterility in Shindai 1 and Shindai 5 are controlled by a different genetic mechanism than in Toyama MS.

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It is necessary to establish stable timber production in order to have a sustainable forest. We investigated the stabilizing effect of two forest management policies: transformation into a normal forest and rotation change. We selected a Japanese cedar forest under private ownership in Kuma-cho, Ehime Prefecture, as the subject of our study. The annual changes in stand volume and timber production were estimated using our forest resources prediction model. The results were compared according to four forest management plans. When we made this model, we regarded the forest as a mass of stands, using the stand density control diagram as a theoretical base. This model predicted various quantities of forest under an assumptive forest management plan. Four forest management plans were compared: normal and pre-normal stand and 50-year and 100-year rotations. The results showed that the transformation into a normal forest was effective in stabilizing the quantity of timber production, while making adjustments in rotation alone was not as effective. Therefore, we propose a change from the present forest into a normal forest, accompanied by adjustment of the quantity of stand volume and timber production to demand by rotation in the Japanese cedar forest of Kuma-cho.

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Data on the Japanese larch (Larix kaempferi Carr) forest damaged by glaze in Hidaka Hokkaido in February 2004 was analyzed to work toward developing a system that minimizes glaze damage. The distribution shape of the percentage of damaged trees in each diameter class reflects that the trees can roughly be classified into five types: (1) trees with mean diameter that were more damaged than the rest, (2) trees with smaller diameters that were more damaged than the rest, (3) trees with larger diameters that were more damaged than the rest, (4) trees with variable damage rate regardless of the diameter, and (5) trees with fixed damage rate regardless of the diameter. It was assumed that these differences in the distribution shape were related to meteorological factors such as wind and icing. A linear discriminant analysis of the light and heavy damaged stands through a stand density control diagram showed that the discriminant rate had reached 75%. To identify the region where damage reduction is expected in the stand density control diagram, the borderline between the safe and the unsafe regions was drawn using the linear discriminant function and yield index (Ry=0.9) curve. Moreover, the critical slenderness ratio curve elucidated the relationship between the average tree height and slenderness ratio obtained by logistic approximation, and we found that the critical slenderness ratio changes with every growing stage. These results suggest that thinning in proportion with initial density is important in order to reduce glaze damage in forests.

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We examined the reproductive ecology of the burrower bugs (Macroscytus japonensis) that suck seeds of cherry (Prunus verecuude) dispersed on forest floors and induce rotting of the seeds. The burrower bugs cached the cherry seeds in the soil at 1 cm depth and sucked the cached seeds in the laboratory. The cherry seeds sucked by the burrower bugs, even if by the first instar nymphs, consequently rotted. Forty-three percent of the first instar nymphs fed a cherry seed survived to adulthood. The burrower bugs were most active under the crown of cherry trees from mid-June to mid-July when their seeds were dispersed, and their nymphs were found from late July to late August under cherry tree crowns. These results suggest that the burrower bugs breed on the forest floor under the cherry trees and that they are important seed predators for cherry trees. The burrower bugs sucked the seeds of six of eight species collected in the study area and fed to them. Therefore, they may induce the dispersed seeds of several species besides P. verecunda to rot.

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Beech trees often dominate the natural forests in northeast part of Japan. This is partly attributable to heavy snow environment in these districts. Deep snow cover during winter season may contribute to protect seeds on the ground from wood mice otherwise they totally feed or remove seeds. To verify this hypothesis, at sites around and far from stems of canopy trees, we compared snow disappearance date, seedling densities and seed removal rate by rodents. Snow cover around stems disappeared earlier than far sites. Correspondingly, seedlings were scarcely found around stems, while seedling banks established 2~3 m apart from mother stems. Moreover, seed predation rate by mice were higher around stems than sites far from stems. However, experimental addition of snow pack around stems depressed the predation rate significantly. These results suggest that snow cover prevents rodents from seed feeding and plays an important role for successful regeneration. This may also be one of the reasons why beech tree can establish at high density level in snowy regions.

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The longhorn beetle, Apriona japonica, damages various broad-leaved trees. In a mixed forest of Robinia pseudoacacia and Celtis sinensis at Uchinada, Ishikawa Prefecture, barkfeeding adults are thought to attack C. sinensis primarily and to deposit eggs mainly on R. pseudoacacia. In order to verify the utility of fenitrothion-spraying to control A. japonica adults, I sprayed the branches of C. sinensis trees with 4.4% fenitrothion twice in the field, just before the occurrence of A. japonica adults and three weeks later. A. japonica adults were killed continuously throughout the period that they occurred on C. sinensis trees. I reared A. japonica adults in the laboratory on C. sinensis branches that were sprayed with 0.44% fenitrothion once and/or twice at a three-week interval. All adults were killed within three days when they fed on the branches sprayed once 1~4 weeks and those sprayed twice 4~6 weeks before the experiments, respectively. These results suggest that spraying fenitrothion should be effective in the management of A. japonica adults and that spraying of 0.44% fenitrothion twice at a 3 week interval can kill nearly 100% of adults over a period of nine weeks.

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We investigated changes in the spatial distribution of trees in a 90-year-old Chamaecyparis obtusa plantation owned by Hieizan Enryakuji Temple using the L-function. The plantation is an example of long-rotation silviculture for producing large-diameter timber. After two thinning treatments, minimurn nearest neighbor distance increased from 0.15 m to 1.19 m and tree distribution pattern became increasingly regular. The greatest change in tree distribution pattern was observed in the midslope position where large-diameter trees were harvested in the previous thinning. Sufficient tree spacing was realized by the last two thinnings. However, heavy thinning treatments may have caused a decline in standing volume. Quantitative analysis of tree distribution and stand growih using spatial statistics will contribute to establishing protocols for long-rotation silviculture in old-aged plantations.

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The Japanese squirrel (Sciurus lis) is largely dependent on Japanese red pine (Pinus densiflora) for their habitat, and its local extinction are supposed to be affected by the expansion of a pine wilt disease. In this study, we examined the relationship between number of food remain and the density of squirrels in 43 ha study area of pine forest at northern Mt. Fuji from June 2003 to August 2005. The density of squirrels was estimated by trapping and radio-tracking. Food remains of pine cones on the forest floor were counted every month. The number of cones eaten by squirrels was significantly correlated with the density of squirrels. Next, based on these density criteria of the food remains, we determined a suitable structure of the pine forests for squirrels. The vegetation and the number of remained cones were compared 30 woodlots within 15 km² area of northern Mt. Fuji. Squirrels tended to use more frequently the forest with more number of tree species and evergreen trees in the middle layer.

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