To investigate the mechanisms causing male sterility of four Cryptomeria japonica D.Don individuals (Fukushima-1, Fukushima-2, Shindai-11, and Shindai-12), histological information was collected using light, fluorescence, scanning electron and transmission electron microscopes. In the four sterile males, the tetrads developed just as for fertile individuals in the microspore formation process. However, they did not release any microspores after callose dissolution because the microspores adhered to each other, and showed no pollen dispersal. In these sterile males, each microspore adhered partially since proendexine of the exine was not developed, though it generally develops during the period when microspores are enclosed by the callose wall. The release of the Ubisch bodies from the tapetum was not observed after callose dissolution, and the amount of translucent amorphous substances gradually increased. Our results suggested that the male sterility of these C. japonica individuals was caused by abnormal behaviors of microspore cytoplasm and tapetum without normal supply of the substances that compose the exine of the pollen wall.

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This research reveals that the static resistance of trees varies according to whether trees depend on soil water conditions in the case of Japanese larch, whether they originated in seeding or transplanting in the case of Japanese oak, and whether they grow close together or not in the case of Japanese larch. This is verified by experiments of pulling down trees that grow in different conditions. It has been said that forests play important roles in preventing sediment disasters. However, it has been unknown to what extent which kinds of trees contribute to preventing debris flow in mountain areas. Therefore, we compared differences of the maximum tree-pulling moment of several kinds of trees that have different soil water conditions, different origins in growing, and different grove density by conducting experiments of pulling down the trees. In the experiments, we calculated the maximum tree-pulling moment whenever a heavy machine or TIR FOR pulled down a tree by drawing a wire passed around the tree at a height of one meter. The experiments show three results. First, there are no differences of the maximum tree-pulling moment even among trees that depend even on different soil water conditions. Second, the maximum tree-pulling moment of trees originated in seeding is the same as for those in transplanted. Finally, there are negative correlations between the maximum tree-pulling moment and the grove density

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This study investigated the incidence of Clitocybe root rot of cherry trees in Matsue-Jozan Park between March 2002 and March 2010. Of the trees studied, 63% were identified as diseased, and 37% were dead. This severe damage may be attributable to the application of wood chips to the study trees. Somatic incompatibility tests were used to determine the genet distribution of the isolates obtained from infected or dead trees. The 70 isolates obtained were classified into 10 genets. Nine genets were found in 1∼11 trees. The remaining genet was found in 27 trees, of which 25 were widely separated in a 50×75 m plot. Eleven saplings were paired with and planted near dead trees and rapidly died within 2∼4 years after planting; the isolates obtained from these saplings were the same as those obtained from the dead trees located nearby. These results suggest that the pathogen was transmitted via air-borne basidiospores and spread clonally underground in the park. The isolates from trees separated by 270 m from each other were identified as belonging to the same genet, suggesting that inocula of the pathogen were transmitted between the trees.

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Castanopsis cuspidata, which is considered as a late successional species in a warm-temperate, evergreen broad-leaved forest, has often expanded its range in abandoned secondary forests of Kyoto City. To clarify changes in species composition and diversity in the course of succession, we established two study plots with different successional stages, i.e. one was located in a mid-succecssional forest dominated by deciduous broad-leaved species, such as Quercus variabilis and Q. serrata, and the other was located in a late-successional forest dominated by evergreen broad-leaved species of C. cuspidata, and examined their species composition and diversity in relation to stem size class. In larger size classes (stem length ≥ 100 cm), species diversity was similar for the two plots. However, species composition differed between them: shrub, deciduous, and/or wind-dispersed species were more abundant in a mid-successional plot than in a late-successional. In smaller size classes (stem length < 100cm), species composition became similar and species diversity decreased in the two plots because evergreen broad-leaved tree species, such as C. cuspidata and Q. glauca, extremely increased in number in both plots. Although bird-dispersed species established in smaller size classes in the mid-successional plot, few individuals of shrub, deciduous, and/or wind-dispersed species occurred there in smaller size. These results suggest that species richness will decrease in this region without any intervention.

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We examined whether pre-dispersal feeding by insects (pre-insects) or the status of acorns facilitates acorn infestation by insects that feed on post-dispersal acorns (post-insects) of Quercus crispula. In an Abies-Tsuga natural forest, we sowed the acorns with different types of holes and germination status under the canopy of Q. crispula in late May 2009: germinated or ungerminated acorns with larval emergence holes of pre-insects, those with artificially bored holes, and those without holes. One month later, acorns were collected to check the infestation by post-insects. We found that the spermathophagpus scolytid beetles penetrated acorns regardless of the types of holes on the acorns or germination status, whereas infestation by moth larvae was concentrated on the germinated acorns or the ungerminated acorns with artificial holes. Therefore, emergence holes alone neither facilitate nor inhibit acorn infestation by post-insects, whereas post-insects tend to infest germinated acorns. In particular, germination facilitates acorn infestation by moth larvae.

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To investigate the effects of elevation, thermal conditions (MB index), topography and direction of slope on the damage of pine death in Kyoto City, the pine mortalities at 445 stands of Japanese red pine (Pinus densiflora) forest were evaluated by visual diagnosis. The pine mortality decreased at pine stands above 500 m of elevation or lower than 27 of MB index, respectively. Elevation was as accurate as MB index to predict pine mortality. The mortality was lower on mountain ridges than on slopes. Difference in the pine mortality according to slope direction was not clear. An elevation-based hazard map for pine wilt disease was constructed because handling this criterion was easier than MB index. The overall results indicated that as most of pine forests essential for landscape conservation in Kyoto City are located at less than 500 m of elevation, control programs should be carried out exhaustively at this place.

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