Most insects in temperate regions and tropical regions with distinct dry seasons exhibit seasonal life cycles that are adapted to seasonal climatic conditions. These insects tend to exhibit seasonal fluctuations in abundance at certain stages of their life cycle. Previous studies have shown that most insect species in several taxa display no clear seasonal patterns in their population fluctuations in the Bornean lowland tropical rainforests, where seasonal climatic changes are minimal, and there are no distinct dry seasons. However, the responses of insect populations to aseasonal climatic conditions in the tropical rainforest areas of the Southeast Asian tropics have not been sufficiently studied, and patterns in temporal population trends need to be investigated for a wider range of insect taxa. In this study, we investigated the temporal population trend of 11 abundant cicada species using data of individual numbers of cicada species collected by monthly light-trapping for the four years from 1993 to 1997. The majority of the target cicada species did not show any clear seasonal patterns in their population fluctuations. In contrast, clear seasonal patterns were detected in the population trends of two cicada species, Dundubia vaginata and Purana sp. 2., with the abundance peaking around March and November, respectively.

This study evaluated the greenhouse gas (GHG) emissions reduction potential of utilizing empty fruit bunch (EFB) pellets from Indonesia as a power generation fuel in Japan. EFB is commonly processed through mulching or combustion; thus, these methods were used as the reference scenarios to compare emissions with EFB pellet utilization. Additionally, we assessed whether EFB pellets could outperform coal-fired and liquid natural gas (LNG) combined cycle power generation in terms of GHG emissions reduction. The life-cycle GHG emissions for EFB pellet utilization in Japan were calculated at 285 kg-CO₂eq per metric ton of EFB (at 60 % moisture content, wet basis), surpassing the reference scenario by 278−279 kg-CO₂eq. Compared to coal-fired power generation, EFB pellet utilization achieved a 33 % GHG emissions reduction, but emissions exceeded those of LNG combined cycle generation. The primary emissions source was biogas derived CH₄ released during wastewater treatment in pellet production. A sensitivity analysis, considering biogas treatment rates and power generation efficiency, demonstrated that EFB pellet use could reduce GHG emissions relative to LNG combined cycle generation under specific conditions. These include operation in large-scale power plants with a generation efficiency of at least 40 % and a biogas reduction rate of 49 %. The findings suggest that EFB pellet utilization in Japan could contribute to GHG emissions reduction if a stable supply system is established to support large-scale power plants. Successful implementation requires developing incentives for biogas treatment at pellet mills and accurately assessing EFB availability to prevent competition with existing uses.

We collected Crotalaria calycina (Fabaceae) from a rangeland on Ishigaki Island. This is the first record of this species in Japan in 47 years, since 1977. A vegetation survey conducted to assess its habitat revealed that Crotalaria calycina and several coexisting grassland species were only found on the hilltop that had never undergone land consolidation and was maintained through cattle grazing. However, the dominance of invasive species in this habitat suggests that they likely have invaded from surrounding other parcels, indicating the importance of continued grazing to ensure the persistence of the species. Morphological measurements were generally consistent with literature values, except for the size of stipule, but further ecological and phylogenetic studies are required to understand its conservation values and phylogenetic origin. To properly conserve this plant, monitoring surveys need to be carried out regularly, because there are high risks of habitat loss due to development and/or abandonment of rangelands in Ishigaki Island.

‘Database for radial variations of anatomical characteristics and wood properties in tropical trees (DaRV-tropics)’ is constructed using data collected by the Laboratory of Forest Products and Wood Material Science, School of Agriculture, Utsunomiya University, Japan, to promote effective utilization of forest resources. The concept to construct this database is ‘how we can construct a database easier’ and ‘how we can maintain it easier’. The first edition of DaRV-tropics includes 39 study project data consisted of 298 individual trees from 35 species (24 genera from 14 families) collected from Indonesia, Malaysia, and Thailand. DaRV-tropics includes radial variations of measured traits, such as basic density, compressive strength parallel to grain, length and diameter of wood fiber and vessel element, vessel frequency, and wall thickness of wood fiber, as well as mean values. Our database has made it possible to provide basic information that contributes to the development of research on tropical hardwoods.