The separation of filled and empty seeds of Japanese larch and F₁ hybrid larch was carried out in ethanol by the density method and then the effect of this treatment on seed germination was investigated. In the flotation tests, 99.5% ethanol was found to be most suitable for separation of filled and empty seeds. 94.0-97.3% of the filled seeds sank in 99.5% ethanol and 93.1-98.7% of the sunken seeds were filled seeds. The influence of ethanol immersion on seed germination was different between Japanese larch and F₁ hybrid larch. For Japanese larch, germination percentages of the flotation in ethanol and control treatments were 36.4-50.9 and 66.7-81.0%, respectively. On the other hand, for F₁ hybrid larch, germination percentages of the flotation in ethanol and control treatments were 94.2 and 88.3%, respectively. These results indicated that filled seeds of Japanese larch and F₁ hybrid larch could be separated from empty seeds at a very high proportion by flotation in ethanol and this treatment may inhibit seed germination.

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The post-clearcutting regeneration of Magnolia stellata, an endangered tree species endemic to the hilly Tokai region of Japan, has been investigated. Regeneration by sprouting and seedling establishment was evaluated in a plot measuring 30 m × 10 m between April and November in 2012. After clearcutting, the dominant species (in terms of total number of sprouts) within the plot were Ilex pedunculosa, M. stellata, Hydrangea paniculata and Gamblea innovans. H. paniculata accounted for most of the taller nearest neighbors of M. stellata individuals and was therefore considered to be the primary competitor of M. stellata. The mortality rates for stumps and individuals of M. stellata were 19 and 12%, respectively. Stump death was independent of age and size, so individuals with few stumps were most likely to die. Stumps with diameters of 12-20 cm produced the greatest numbers of sprouts, so this stump diameter was regarded as optimal for regeneration by sprouting. In total, 175 seedlings germinated from seed banks were identified after clearcutting.

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We conducted reciprocal interspecific crosses between Magnolia stellata and M. salicifolia and investigated whether there are differences in the development of fruits and seeds and the germination rate of seeds between reciprocal interspecific crosses. After 60-90 days from the hand pollination, the proportion of aborted fruits was higher for the interspecific cross of M. stellata as maternal parents than for that of M. salicifolia as maternal parents. Moreover, the fruit set, seed set and female reproductive success in the interspecific cross of M. stellata as maternal parents were all lower than those of M. salicifolia as maternal parents. The germination rate of seeds produced from the interspecific crosses in which maternal parents were M. stellata was lower than that in which maternal parents were M. salicifolia, but its difference was not statistically significant. Therefore, the occurrence of unidirectional interspecific hybridization in which M. salicifolia is a maternal parent and M. stellate is a paternal parent under nature conditions may be caused mainly by a failure in the fruit maturation and seed development in the interspecific cross of M. stellate as maternal parents.

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Field experiments conducted on coastal forests after the 2011 Tohoku earthquake tsunami revealed that the tree size influenced the tree damage rate and its status (uprooting or stem breakage). In this study, to examine these results from the physical standpoint, the critical flow velocities for uprooting and stem breakage were calculated using a simple dynamics model and using field data from Misawa, Aomori Prefecture, Japan. The calculations showed that the damaged trees in the field experiments had relatively low critical flow velocities. In particular, trees with crown base heights of ≤ 6 m suggested relatively low critical flow velocities. According to the predicted status obtained using calculations, most of the trees were uprooted. This result was consistent with those of the field experiments. The influence of slenderness ratio on the critical flow velocity was not apparent. This approach can facilitate the comparisons of tree damage mechanisms in respective forests.

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Three, four, and five millimeters soil aggregate samples were collected from the A horizons of a Japanese cypress (Chamaecyparis obtusa Endl) and broad leaf stand and incubated for 14 d under three different moisture conditions: dry, repeated dry-wet cycle, and wet. The 3- and 4-mm aggregates from both stands incubated under repeated dry-wet conditions were easily dispersed by slaking, whereas similarly incubated 5-mm aggregates were not as readily dispersed. The degree of aggregate dispersion varied by aggregate size, with larger aggregates being less readily dispersed than smaller aggregates. Moreover, there was no clear difference in degree of aggregate dispersion between stands. Aggregate dispersion was not observed in aggregates incubated under wet conditions.

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In order to revitalize depopulated areas, rural development using local natural resources is important. This case study examined the role of human network in rural development using social network analysis, focusing on Kuzumaki Town in Iwate Prefecture. The present and former town mayors were located displaying their leadership at the center of their respective networks when they are or were in office. The core network consisted of the town mayor, vice-town mayor, leaders in joint public-private ventures and forest association in the town. The highly cohesive network between these local leaders across sectional barriers supported the town mayors' leadership. In addition, the dense network has remained stable across the two periods, forming bonding social capital. On the other hand, actors in the core network had a lot of ties with actors not only inside but also outside the town, functioning as bridging social capital to obtain diverse resources from outside the town.

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Forest stand characteristics as the individual size is not reflected in the biomass estimations, because the biomass expansion factors (BEF) of Japan are a constant value by the stand age and the tree species. In this study, the biomass expansion factors of Pinus thunbergii coastal forests were estimated. We discussed about the relationship between the each BEF and individual size, individual growth. In addition, we considered the distributions of the BEF of the each DBH in the forest stand. As a result, the value of the BEF was decreasing with passage of time (growth) at the same individual, and thereafter it became constant. In addition, the distributions of the BEF in the forest stand were seen that small-diameter trees had large values and in more big-diameter trees had constant values. From the above, the values of the BEF were considered possibility different depending on the percentage of decrease of BEF with individual's growth, and the stand composition. Therefore, it is necessary to calculate the BEF at a level of individual tree, forest stand or region.

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We investigated the mean crown lengths of Japanese cedar trees in 12 overcrowded mature plantations. In pooling the data for unthinned young and overcrowded mature plantations, the mean crown length of Japanese cedar trees in each plantation was positively correlated with mean upper tree height in each plantation. However, the average mean crown length of trees in overcrowded mature plantations was 5.9 m, which was only slightly greater than that of trees in unthinned young plantations (5.4 m). Thus, if intensive thinning is not conducted, the crown lengths of mature trees will not steadily increase.

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