Although the necessity for hamlet-scale demographic analysis has been repeatedly pointed out, there has been little research due to scarcity of data. The purpose of this paper is twofold: (1) to explore the feasibility of hamlet-scale demographic analysis using the population census and (2) to examine the merger of hamlets from a demographic perspective using a cohort analysis. Thus, we chose the merger of three hamlets in the Fudo district of Joetsu City, Niigata Prefecture, in 2020. The results follow. (1) The population of hamlets after 1965 could be ascertained from censuses by interpreting census enumeration districts as hamlets, but it was not possible to similarly use censuses after 2000. (2) Fudo Elementary School became independent and expanded in the 1950s because of the large population of the cohort born during 1946-1955, i.e. the “independent-school generation.” In the post-2000 era, as a response to the declining birth rates and subsequent closure of elementary schools, there has been a call for this generation to forge a new bond. (3) The population of people aged in their 60s and 70s who serve as district officers peaked in 2015 and has been declining since. In summary, this hamlet merger was conducted by the “independent-school generation” who were old enough to be designated as district officers and had prepared for a future population decline. Future tasks are to examine the life of each of the “independent-school generation” and to improve hamlet-scale demographic analysis considering gender and social mobility trends.

The natural regeneration processes of a Chamaecyparis obtusa forest using selective cutting were reconstructed by tree-ring analysis, and the effects of disturbance on the regeneration were examined. This research was conducted at the Akasawa Experimental Forest, Kiso district, central Japan, in a stand lacking dwarf bamboo in the undergrowth. About 30 years after a selective cutting conducted in 1984-1986, the height distribution of regenerating C. obtusa individuals consisted of two groups, a larger group with heights of 2-3 m or more, and a smaller group. Tree-ring analysis revealed that the former corresponded to the advanced population recruited before the cutting and the latter to the newly recruited population emerging after the cutting. The growth of the advanced population was vigorous from 1945 to 1960, but then declined greatly. Growth increased after the cutting, and again after an undergrowth removal conducted in 1997. These findings suggest that there was a canopy opening event around 1940 that improved light conditions and caused the recruitment of the advanced population. Subsequent inferior light conditions reduced sapling growth and survival, but the selective cutting prevented their ultimate extinction and allowed for a return to vigorous growth. The advanced population will eventually play the leading role in the next generation forest, and the newly recruited population will function as prospective successors in the future. Repeated disturbances at several-decade intervals that improve light conditions are likely to contribute to the success of natural regeneration practice.

Nut weevils (genus Curculio) are major pre-dispersal seed predators that determine subsequent Fagaceae tree recruitment. In this study, we investigated seed production, size, and germination in two oak species (Quercus serrata and Quercus crispula) and the chestnut Castanea crenata, as well as tree species preferences among larvae of different Curculio species. We collected a total of 105 seeds from beneath 10 trees of each species. Larvae emerging from the seeds were reared in pudding cups covered with rearing mats, and mature weevils were identified to species. The success or failure of germination of each acorn was recorded. The highest feeding damage rate was observed in C. crenata nuts (50.5％), followed by acorns of Q. crispula (41.0％) and Q. serrata (24.8％). In both Q. serrata and Q. crispula, acorn size was significantly positively correlated with the number of Curculio larvae that emerged from the acorns. Three nut weevil species (Curculio sikkimensis, Curculio dentipes, and Curculio distinguendus) matured from acorns of Q. serrata and Q. crispula, whereas only C. sikkimensis matured from nuts of C. crenata. Only the dominant weevil species, C. sikkimensis, selected C. crenata nuts. Germination success increased with acorn size in Q. serrata, with fewer acorn weevil larvae (indicating less feeding damage) in Q. crispula, and was not significantly affected by acorn size or number of acorn weevil larvae in C. crenata.