It is important to be able to assess the risk of wind damage to stands in a long rotation forestry operation. In this study a mechanistic model was used to examine the effect of different planting densities and thinning frequencies on the resistance of Japanese larch stands to wind damage. Critical wind speeds at a height of 10 m above ground level required to cause uprooting or stem breakage was used as the index of resistance to wind damage. All wind damage to trees was uprooting. The resistance of stands at lower planting densities was higher than that of stands at higher planting densities. Differences in thinning frequency affected stand resistance: management for a low yield index (Ry=0.6∼0.7) increased the resistance of stands compared with management for a high yield index (Ry=0.7∼0.8). As stand age increased, resistance to wind damage decreased until a tree was 20∼30 years of age. Thereafter, resistance to wind damage increased as stand age increased. This 20- to 30-year period coincided with the period during which slenderness ratios (H/D) were the highest of all growing stages. Differences in a long rotation forestry operation at high site index had a strong effect on the resistance to wind damage.

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The resistance force was measured as hung-up trees were passed through the crowns of remaining trees in a Chamaecyparis obtusa stand. The average resistance force was 1.0 kN. A large force was needed to remove manually a tree hung up between two standing trees in an overcrowded thinning stand. The size of a hung-up tree did not have an effect on the resistance force, while leaning angle at which the tree was hung-up influenced the resistance force strongly. The distance between the remaining trees affected the resistance force, which increased exponentially as the distance between the remaining trees decreased.

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We analyzed the species composition of the timbers in a traditional farmhouse and surrounding forests in Iiyama (central Japanese snowbelt). In addition, we analyzed forest stand structure. Among the beech (Fagus crenata), oak (Quercus spp.), Japanese zelkova (Zelkova serrata), and cedar (Cryptomeria japonica) that comprised the 302 structural timbers (15.75 m³) in the house, the majority in terms of number and summed volume was cedar (226 timbers, 9.49 m³), while beech constituted the largest volume of planed timber (1,005 cm³/timber). The adjacent forests consisted of secondary beech and oak (Q. serrata-Q. crispla) stands and cedar plantations, and these species made up most of the house timbers. We were able to classify the beech stands into four developmental stages, suggesting the sustainable use of this species in the past. The fourth beech stand developmental stage comprised large, densely packed trees (dbh ≥ 60 cm; height ≥ 24 m), suggesting a source for water as well as building timbers. Stands of large beech are characteristic of snowbelt forests and provide appropriately large timbers for the load-bearing structures of houses that are partially buried in heavy snow every winter.

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To examine the effects of understory vegetation on infiltration capacity, a series of field infiltration test was conducted by using an oscillating nozzle rainfall simulator at 14 sites in steep Japanese cypress plantation. The simple regression analysis among the maximum final infiltration rate (FIR_max), percentage vegetation cover and dry weight of surface cover materials such as understory vegetation were also conducted. The FIR_max for the 14 sites ranged from 5 to 322 mm h⁻¹, and significant correlations were found between the FIR_max and the dry weight, percentage cover of understory vegetation. The lower FIR_max was observed at the site where the percentage vegetation cover was less than 50%, suggesting that Hortonian overland flow may occurs under natural rainfall. This indicated that the cover abundance of 3 or less based on the Braun-Blanquet’s method may result in the significant reduction in infiltration rate. The results indicate that densely vegetated surface can maintain high infiltration capacity on forested steep hillslopes, and cover abundance of the Braun-Blanquet’s method were useful to estimate infiltration capacity in Japanese cypress plantation. This study suggested that the measurement of understory vegetation cover can be used to assess the degradation of unmanaged Japanese cypress plantation, and to establish soil and water conservation practice based on the management of infiltration capacity.

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Diallel analyses were performed on basal bending due to snow pressure in sugi (Cryptomeria japonica). Four mating sets, which consisted of 5×5 diallel crosses excluding self-pollinated families, from different trials were investigated at stand age 10. The results of ANOVA showed that significant effects of the general combining ability (GCA) were observed in the three data sets and that special combining ability was not observed in all the data sets. Relationships between the averages of crossing families in each trial and estimated GCA of their parents were investigated. The averages were estimated precisely from parents’ GCA in the three data sets, and significant differences in GCA between mating parents were observed. Reciprocal differences of GCA were not observed in all the data sets. Furthermore, the maternal and paternal averages were equivalent, and their relationships on the intercept and slope of the regression line were 0 and 1, respectively. It is concluded that reciprocal difference has little influence on basal bending.

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To clarify the influence of micro-topography on patterns of acorn dispersal by wood mice, we performed an acorn dispersal experiment using acorns containing magnets and a magnetic locator in the lower and crest areas of a slope in a lucidophyllous forest established on a steep slope. Most acorns were dispersed further down the slope from their installed locations, remaining within approximately 4 and 14 m of the lower and crest area of the slope, respectively. The lower slope was characterized as having numerous exposed rocks and formed a valley which is likely to have further limited the downward movement of acorns. These results showed that acorn dispersal by wood mice is generally limited by slope gradient. Further, acorn dispersal to the lower parts of the slope and the other side of the valley was limited by the valley itself. Conversely, several acorns were dispersed up the slope, indicating the important role of wood mice for acorn dispersal, even though the overall proportion of acorns dispersed this way in a single year is likely to be low.

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As a part of a study estimating the maximum dispersal distance of beech seeds by various bird species near the northern range boundary of beech (Fagus crenata), a varied tit (Parus varius) was captured and a small radio transmitter was attached to the bird in late autumn at a beech forest in Kuromatsunai, Hokkaido. The bird was then tracked for five days by the radio-telemetry method. By using triangulation with two azimuths and the MCP (minimum convex polygon) method, the home range of the varied tit was estimated to be between 2.1 ha and 6.5 ha per day and 11.4 ha in total. The maximum seed dispersal distance by the bird was estimated as 163 m and 529 m. Although the study period was more than a month longer, estimated home ranges for other Paridae overseas showed similar values (14.7 ha for Poecile hudsonica and 12.6 ha for Parus montanus), suggesting that the method applied in this study was reasonably valid. Near the northern range boundary of beech, isolated beech communities are separated from each other by distances between ca. 2 and 4 km. Thus, it is hard to consider that these communities were initially established from beech seeds dispersed by varied tits.

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In a Chamaecyparis obtusa plantation, we examined the effect of thinning on soil animal communities. The community composition and individual densities of soil animals were compared between a rich-understory plot with thinning management (the thinned plot) and a poor understory plot without thinning (the delayed thinning plot). Soil animals sampled from both the litter and soil layers were classified after collection by the Tullgren method. In both layers, the taxa in the delayed thinning plot were significantly poorer than those in the thinned plot. The densities of oribatida mites and collembolans, both of which were dominant taxa, were significantly lower in the delayed thinning plot than in the thinned plot for both litter and soil samples. Our results suggest that lack of management of forests such as no thinning has a negative effect on the community composition and density of soil animals in the forest floor.

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In recent years, a new concept has been developed of “biomats” that are comprised of a litter layer that exists in the surface of the forest soillayer, layers of dense root networks, and so on. One of the functions of forest soils is help runoff prevention (function) by filtering turbid water. In order to evaluate this turbid filtration function, it is important to correctly evaluate the role that “biomats” (the layers with high permeability) play in this function. Therefore, with the objective of quantitatively evaluating the turbid filtration capacity of biomats, preliminary experiments were conducted to gain a clear understanding of what factors might affect filtration. As a result, it was found that there was a positive correlation between the turbid filtration function of biomats and the volume of biomats in a unit area of a forest.

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