We studied regeneration patterns of the four canopy dominants, Abiessachalinensis (Fr. Schm.) Masters, Piceajezoensis (Sieb. et Zucc.) Cam, Piceaglehnii (Fr. Schm.) Masters, and Betulaermanii Cham., of an old-growth (>400 years) boreal coniferous forest in northern Japan. Age and size structure, height growth, and diameter growth of tree populations in a 40 × 40 m plot were analyzed. Seedling establishment was restricted to nurse logs and mounds (98%), where the influence of dwarf bamboo (Sasasenanensis (Franch. et Sav.) Rehd.) was limited. Abiessachalinensis had a high density (10 263/ha) but a high mortality (8.4%/year for saplings, 1.7%/year for canopy trees) and a short canopy residence time. It also showed a more rapid tree-ring width increase after disturbances. Piceaglehnii had a low density (1450/ha) but a low mortality (6.9%/year for saplings, 0.1%/year for canopy trees) and a longer residence time in the canopy. Piceajezoensis had an intermediate density (8206/ha) and its mortality rate for canopy trees (0.9%/year) was lower than that of A. sachalinensis, although its sapling mortality rate (8.1%/year) was similar to that of A. sachalinensis. Betulaermanii had a higher mortality (14.1%/year for saplings, 2.4%/year for canopy trees) than the conifers. On the other hand, B. ermanii had the highest height growth and P. glehnii had the lowest. The mortality and average height growth of saplings showed a trade-off relationship. The trade-off relation in life history strategy may contribute to the coexistence of these species. The proportion of the gap area created in the forest was 1.2–2.4%/year, and a forest turnover time calculated from aboveground volumes was 87–99 years. These values were similar to a weighted mean of the estimated life times of the constituent species, 71 years for A. sachalinensis, 123 years for P. jezoensis, and 49 years for B. ermanii.

AbstractmRelationships between leaf or shoot size, number, and arrangement in response to light were investigated to test the hypothesis that these characteristics are linked. In order to test this hypothesis, the divergence in allometry and shoot dynamics in saplings of Japanese beech (Fagus crenata) obtained from four populations and having different leaf sizes were examined in a nursery under both full sun and shade conditions. Trees with different leaf sizes also showed large differences in canopy structure, particularly when shade-grown saplings were compared. The final leaf mass distributions of the large-leaf populations were conical or ªbottom -heavyº, while those of the small-leaf populations were planar or ªtop -heavyº. The slope of the allometric relations between leaf mass and shoot and branch mass in small-leaved populations were steeper than those in large-leaf populations. The four populations were classified into two growth types: populations producing a few large leaf and shoot modules corresponded to ªstem growth typeº, and those producing many small leaf and shoot modules corresponded to ªleaf growth typeº. These kinds of intra-specific variation in architecture and growth of F. crenata trees may influence the structure and dynamics of forests in accordance with differences in competitive ability or sensitivity to disturbances such as windstorm.

Reforestation, which converts abandoned farmland back into forestland by planting woody species, can provide habitat for wildlife, including the brown bear (Ursus arctos Linnaeus, 1758). In the Shiretoko World Heritage site, northern Japan, where brown bears occur at high density, conifers have been planted since the 1970s to reforest abandoned farmland. In this area, brown bears were first observed digging for cicada nymphs (Lyristes bihamatus Motschulsky, 1861) from 2000. Our preliminary observations suggested the emergence of digging behavior might be associated with reforestation. We examined whether reforestation provided a foraging habitat for brown bears. We found that digging occurred only within the restored conifer forests, but not within the natural forest. The densities of cicada nymphs in the restored forests were higher than in the natural forest. These results indicate that the reforestation of abandoned farmland provides a foraging habitat for brown bears by increasing the availability of cicada nymphs in the Shiretoko World Heritage site.

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