South Kyushu Research Articles

Geochemistry of Neogene Nansatsu volcanic rocks in South Kyushu, Japan

ABSTRACT We report the whole-rock major and trace element and Sr – Nd – Pb isotopic compositions of volcanic rocks from the Nansatsu area in South Kyushu. We analysed samples from the Oldest stage (middle Miocene), Older stage (late Miocene), and Middle stage (early Pliocene) Nansatsu volcanic rocks, which are andesite to dacite in composition, with an island-arc trace element signature. The compositional variabilities within the Older and the Middle stage rocks are relatively small compared to those in the Oldest stage and Quaternary volcanic rocks. Isotopic characteristics suggested that the Oldest stage volcanic rocks had magma sources similar to regional ilmenite-series granitoids of later ages (Outer Zone granitoids), which incorporated a substantial amount of graphite-bearing accretionary sediments (Shimanto Supergroup). The sources for the Older and Middle stage magmas were similar to those of primary Quaternary basalts in South Kyushu, indicating that Pliocene and Quaternary volcanic rocks in South Kyushu share a common mantle source, despite the change in the nature of volcanic activity from andesite-dominated to more variable volcanism of basalt to rhyolite.

Spatial variations in the consolidation of sediments in the Neogene Miyazaki forearc basin, Southwest Japan

The Neogene Miyazaki Group comprises forearc basin sediments exposed onland in South Kyushu in Southwest Japan, and is characterized by significant spatial variations in consolidation despite the minor differences in depositional ages. The Miyazaki Group is divided into three lithofacies (the Aoshima, Miyazaki, and Tsuma facies) from south to north. To evaluate the factors controlling lithification in the basin, the physical properties of the sedimentary rocks and the calcareous nannofossil biostratigraphy were investigated. The upper parts of the Aoshima and Miyazaki facies and the lower part of the Tsuma Facies were deposited at the same time (5–6 Ma), and have minor differences in maximum paleo-temperatures (97–116, 85–99, and 80–94 °C, respectively), but major differences in porosity (15.9%, 25.5%–26.9%, and 26.1%–31.6%) and consolidation yield stress (38.2, 13.8–16.2, and 13.6–15.5 MPa). These findings indicate that the porosity reduction associated with consolidation is a more important control on the lithification than the depositional age and maximum temperature. There is a large difference in maximum burial depth between the Aoshima (>3500 m) and Miyazaki facies (<1600 m). It represents variations in sedimentary depositional environments in the Miyazaki Group: the Aoshima Facies were deposited in the deep-marine depocenter and deeply buried, whereas the Miyazaki and Tsuma facies were in the shallower marine facies and shallowly buried. After the deposition, only the southern part of the Miyazaki forearc basin was largely uplifted, making distribution of the highly consolidated sedimentary rocks there. The large amount of uplift in the Aoshima Facies was apparently due to the subduction of the Kyushu–Palau Ridge beneath the forearc basin.

Dating of a fault zone distributed in the South Kyushu shear zone based on fission-track thermochronology and U-Pb dating

Dating of a fault zone distributed in the South Kyushu shear zone based on fission-track thermochronology and U-Pb dating

Bursa atrophy at 28 days old caused by variant infectious bursal disease virus has a negative economic impact on broiler farms in Japan

ABSTRACT Infectious bursal disease (IBD), caused by IBD virus (IBDV), is highly contagious, immunosuppressive and causes a negative economic impact on poultry industry. IBDV-vaccinated broiler farms at south Kyushu, Japan had a bursa-to-bodyweight ratio (BB ratio) reduction at 28 days (d) old, followed by high mortality 30 d later. We analysed the influence of the IBDV on atrophy of the bursa of fabricius (BF) and the subsequent mortality after 30 d. Ten broilers were sampled at each timepoint from the farm with high mortality at 21, 25, 28 and 35 d. A second flock from the same farm was sampled at 14, 21, 25, 28, 35 and 42 d. IBDV was detected in BF samples at 25, 28 and 35 d and at 21, 25, 28 and 35 d in the first and second flocks, respectively, using immunohistochemical staining and RT-PCR. IBDV isolates from both flocks were closely related to the China KM523643 strain. Histopathology and TUNEL assay indicated apoptosis, severe lymphoid depletion, vacuoles within follicles, lymphoid follicle atrophy and fibrosis in the BF. We observed 75% of the polyserositis and 10% of the airsacculitis at 30 D in dead broilers. The antigenic variant IBDV infection was appeared to be the main influencing factor on BF atrophy and BB ratio reduction in the broilers. High mortality in the broilers after 30 d could be due to secondary infection. The disease caused by IBDV had a negative economic impact in the farm. RESEARCH HIGHLIGHTS New variant IBDV caused bursa atrophy and reduced BB ratio in 28-day-old broilers. After vIBDV had infected broilers, at 21 days old they became immunosuppressed. High mortality at 30 days old in broilers was due to secondary infection. New vIBDV has a negative economic impact on broiler farms in Japan.

Study on moths of the Herminia decipiens complex (Lepidoptera, Erebidae, Herminiinae) with descriptions of three new species.

Asian herminiine moths of the Herminia decipiens complex are revised and five allopatric species are recognized, i.e. Herminia decipiens (Hampson, 1898) in Nilgiri Hills, Khasi Hills, South China, Indochina, Malay Peninsula, H. terminalis (Wileman, 1915) in Taiwan, H. yuksam sp. nov. in East Nepal, Sikkim, H. borneo sp. nov. in Borneo and H. amamioshima sp. nov. in Amami-oshima Is., Shimo-Koshikijima Is. and South Kyushu (Kagoshima). Key to all species is given.

Dynamics of an old evergreen coppice in southwestern Japan with special focus on a typical coppice species (Castanopsis cuspidata) and a climax species (Distylium racemosum)

We investigated stand dynamics of an abandoned evergreen coppice (c.a. 100 years old) over the course of 21 years in south Kyushu, Japan. The study stand showed a change in species composition from being dominated by Castanopsis cuspidata to Distylium racemosum, that is, from a typical coppice species to a typical climax species of the region. However, the relative dominance of Castanopsis spp. appeared to remain very high in the study stand compared to that in the Aya Research Site, a typical old-growth forest in the region, due to abundant C. cuspidata canopy trees of coppice origin. This suggests that the species composition of the study stand remained distinct from that of climax forests in the region. On the other hand, D. racemosum did not show a significant change in diameter at breast height (DBH) class frequency distribution from 1996 to 2017, probably due to the slow growth of this species. However, generalized linear models (GLMs) were used to identify the factors affecting better DBH growth of this species in the gap, indicating the potential for further development of the population structure when small trees are released from suppression of canopy trees. This suggests, inversely, that the development of the D. racemosum population was heavily suppressed by abundant C. cuspidata canopy trees of coppice origin that survived to the age of nearly 100 years. Further, large typhoons are suggested to cause severe canopy disturbances that remove canopy trees of C. cuspidata, which might be important for promoting further forest succession, even for a nearly 100-year-old evergreen old coppice.

Specialized pollination by honeybees in Cymbidium dayanum, a fall–winter flowering orchid

AbstractFloral biology and pollination mechanisms of Cymbidium dayanum, an endangered epiphytic orchid, were investigated in south Kyushu, Japan. The flowering period spanned approximately 4 months from fall to winter, with the inflorescences often blooming asynchronously on each plant and individual flowers commonly lasting for a month. The nectarless flowers are self‐compatible but cannot autonomously self‐pollinate; the orchid needs to attract pollinators by deceit for capsule production. The field observations showed that the flowers were pollinated exclusively by the Japanese honeybee Apis cerana japonica, despite its long flowering period. The worker bees pollinated flowers and/or received the pollinarium on the thorax, while escaping from the labellum chamber. The natural fruit‐set ratios at the population level, an estimate of pollination success, varied interannually but were generally low, as the result of infrequent flower visits by honeybee workers owing to the cold winter climate and the lack of a nectar reward. Because most flowers that were artificially pollinated in the winter successfully developed into capsules, the coldness was not considered a direct cause of the low fruit‐set ratios. Our results explicitly indicate that the bee pollination niche could be available to temperate plant species even during mid‐winter. We inferred advantages for the winter flowering of C. dayanum.

Euler‐Vector Clustering of GPS Velocities Defines Microplate Geometry in Southwest Japan

AbstractI have used Euler‐vector clustering to assign 469 GEONET stations in southwest Japan to k clusters (k = 2, 3,..., 9) so that, for any k, the velocities of stations within each cluster are most consistent with rigid‐block motion on a sphere. That is, I attempt to explain the raw (i.e., uncorrected for strain accumulation), 1996–2006 velocities of those 469 Global Positioning System stations by rigid motion of k clusters on the surface of a spherical Earth. Because block geometry is maintained as strain accumulates, Euler‐vector clustering may better approximate the block geometry than the values of the associated Euler vectors. The microplate solution for each k is constructed by merging contiguous clusters that have closely similar Euler vectors. The best solution consists of three microplates arranged along the Nankaido Trough‐Ryukyu Trench between the Amurian and Philippine Sea Plates. One of these microplates, the South Kyushu Microplate (an extension of the Ryukyu forearc into the southeast corner of Kyushu), had previously been identified from paleomagnetic rotations. Relative to ITRF2000 the three microplates rotate at different rates about neighboring poles located close to the northwest corner of Shikoku. The microplate model is identical to that proposed in the block model of Wallace et al. (2009, https://doi.org/10.1130/G2522A.1) except in southernmost Kyushu. On Shikoku and Honshu, but not Kyushu, the microplate model is consistent with that proposed in the block models of Nishimura and Hashimoto (2006, https://doi.org/10.1016/j.tecto.2006.04.017) and Loveless and Meade (2010, https://doi.org/10.1029/2008JB006248) without the low‐slip‐rate boundaries proposed in the latter.

2. 南九州主要火砕流の層準について(日本火山学会 1973 年度秋季大会講演要旨)

2. 南九州主要火砕流の層準について(日本火山学会 1973 年度秋季大会講演要旨)

十六・十七世紀の東アジア海域と華人知識層の移動 : 南九州の明人医師をめぐって

十六・十七世紀の東アジア海域と華人知識層の移動 : 南九州の明人医師をめぐって

Tracing subducted sediment inputs to the Ryukyu arc-Okinawa Trough system: Evidence from thallium isotopes

Sediments are actively subducted in virtually every arc worldwide. However, quantifying their contributions to arc lavas and thereby establishing budgets of how sediments participate in slab-mantle interaction is challenging. In this contribution we use thallium (Tl) abundances and isotopic compositions of lavas from the Ryukyu arc (including south Kyushu) and its back-arc basin, Okinawa Trough, to investigate the influence of sediments from arc to back-arc. We also present extensive geochemical data for sediments and altered oceanic crust (AOC) outboard of the northern (DSDP Sites 296, 442B, 443 and 444) and central (DSDP Sites 294 and 295) part of the Ryukyu arc. The Tl isotopic compositions of sediments change systematically from lighter outboard of northern Ryukyu arc to heavier outboard of central Ryukyu arc. The feature reflects the dominance of terrigenous material and pelagic sedimentation outboard of the northern and central Ryukyu arc, respectively. Central and northern sections of Ryukyu arc and Okinawa Trough display larger range of Tl isotopic variation than southern section, which is consistent with more pelagic provenance for sediments outboard of central and northern Ryukyu arcs than that of expected sediments outboard of southern Ryukyu arc. Identical Tl, Sr, Nd and Pb isotope variations are found when comparing arc and back arc lavas, which indicates that sediments fluxes also account for the Tl isotopic variations in the Okinawa Trough lavas. Two-end-member mixing models of Tl with Pb, Sr and Nd isotopes require sediment inputs of< 1%, 0.1–1% and 0.3–2% by weight to the depleted mantle source to account for all these isotopic compositions of lavas from northern, central and southern portion of the Ryukyu arc and Okinawa Trough. Bulk mixing between mantle and sediment end members predict very similar sediment fluxes when using Tl, Sr, Nd and Pb isotopes, which indicates that fractionation of these elements must have happened after mixing between mantle and sediments. This conclusion is corroborated by model calculations of mixing between sediment melts with fractionated Sr/Nd ratios and mantle wedge, which show that no arc lava plot on such mixing lines. Thus bulk sediment mixing, rather than sediment melt, is required for the generation of the lavas from the Ryukyu arc and Okinawa Trough. The requirement of bulk sediment mixing occurring before trace element fractionation in the sub-arc mantle is consistent with models where mélange layers form at the top of the slab and are the principle source material for arc lavas. In addition, the fact that sediment components observed in the Ryukyu arc and Okinawa Trough lavas are similar, suggests that transport of mélange material to the source regions of the arc and back arc is equally efficient. This feature is most readily explained if mélange material is transported from the slab as diapirs.

Modeling for diversifying electricity supply by maximizing renewable energy use in Ebino city southern Japan

Energy modeling is the forecasting and projecting of the energy supply and demand for the future. Models focus on predicting energy production, consumption, and costs for various energy resources. Particularly in developing a renewable energy resource based transition model is a critical task because of many uncertainties on computing of renewable resources. After Fukushima disaster and forced an energy system change in Japan by shutting down almost all nuclear power plants the electricity supply and CO2 emission have to be managed by specific energy planning and transition to maximize renewable energy resources which are an important decision. The aim of this paper is to model the energy supply and demand in Ebino city south Kyushu, Japan. The maximum renewable energy supply and electricity demand of Ebino city are analyzed. Electricity demand of the city in 2014 was 162GWh/year and CO2 emission from electricity production was 84570 tons/year. Six different scenarios with a different share of renewable energies are proposed and modelled. Results show that by applying scenarios 5 and 6 renewable energy's share increased from 10% in 2010 to 37.3% for scenario 5 and 54.2% for scenario 6 in 2020 as a target year. Also in scenario 6 by running 20MW of the wind and solar power plants in 2016 extra electricity can be transferred to the utility grid by 11.9, 13.6, and 14.8GWh/year in 2016, 2018, and 2020 respectively.

Structure of Northeastern Sakurajima, South Kyushu, Japan, Revealed by Seismic Reflection Survey(＜Special Section＞Sakurajima Special Issue)

Structure of Northeastern Sakurajima, South Kyushu, Japan, Revealed by Seismic Reflection Survey(＜Special Section＞Sakurajima Special Issue)

A2-13 薩摩半島南部大野岳火山の活動時期について(新燃岳2011年噴火と南九州の火山,口頭発表)

A2-13 薩摩半島南部大野岳火山の活動時期について(新燃岳2011年噴火と南九州の火山,口頭発表)

Ants (Hymenoptera: Formicidae) as potential egg predators of lepidopteran pests of sweet potato, Ipomoea batatas (Solanales: Convolvulaceae), in Japan

The sweet potato Ipomoea batatas (L.) Lam., which has extrafloral nectaries, was visited by nine indigenous ant species in south Kyushu, Japan. These ant species were evaluated for their ability to remove the eggs of two lepidopteran species—Aedia leucomelas (Linnaeus) and Spodoptera litura (Fabricius)—through ant-exclusion experiments. The results showed that Tetramorium bicarinatum (Nylander), one of the dominant ant species, is an efficient predator of lepidopteran eggs. This ant species removed A. leucomelas eggs from ant-visited plants in six trials conducted from mid-July to mid-October, with high removal rates (90–100%) occurring from mid-September onward. On ant-excluded plants, only 0–18% of exposed eggs were removed by ants that accidentally invaded the plants. Tetramorium bicarinatum also removed egg masses and the hatchlings of S. litura. The mean percent area of egg-laden leaves eaten by S. litura larvae was lower on ant-visited plants (0.9%) than on ant-excluded plants (57.3%). In contrast, Formica japonica Motschulsky, another dominant ant species, was not observed removing the eggs or larvae of the lepidopteran species. These results show that certain indigenous ant species are efficient as biocontrol agents. Thus, individual ant species need to be investigated for their ability to control insect pests in various crops.

Vegetation and its regeneration study based on plant demography on Mt. Kurino-dake, South Kyushu, Japan with special reference to vertical forest zones and seedlings of canopy species

Vegetation and its regeneration study based on plant demography on Mt. Kurino-dake, South Kyushu, Japan with special reference to vertical forest zones and seedlings of canopy species

A Verification of Estimation Accuracy of Lightning Current Waveform and Charge Transfer from Measured E‐Field Waveform

SUMMARYTo establish effective countermeasures on power facilities against lightning damage, it is necessary to clarify the lightning characteristics such as current parameters at the area of interest. In order to collect lightning current parameters effectively, the authors have observed electric and magnetic field waveforms simultaneously at south Kyushu, where the lightning flash density in summer is high. Based on observed electric field waveforms, the lightning current parameters have been estimated by adopting the Diendorfer–Uman model (DU model) as the return‐stroke model. In this paper, the accuracy of the estimated return‐stroke current waveform is verified by comparison with directly measured return‐stroke current waveform, along with the accuracy of the estimated charge transfer from the electric field waveform measured with a slow antenna.

Study of segment-based ecoregions using fish fauna for conserving river environments in Kyushu, Japan

Selecting sites for river restoration projects or performing ex post evaluation must be done in ecoregions with comparable biological integrity. Moreover, to evaluate the integrity of a river ecosystem that varies from the headwater to downstream regions, adjustments of the ecoregion according to the longitudinal change in biota must be made. We defined regions where biota are identical according to the direction of change along the stream path as “segment-based ecoregions.” We delineated segment-based ecoregions using fish fauna data for two ecoregions in Japan: the northeast Kyushu, and south Kyushu. The northeast Kyushu ecoregion was divided into three segment-based ecoregions, and south Kyushu ecoregion into five segment-based ecoregions. Classifying fish fauna within the same ecoregion enables classification by differences in the longitudinal change in the stream path rather than by differences in watersheds. Specific topographic regions such as the amphitheater areas of the south Kyushu ecoregion was classified as independent segment-based ecoregions. We further defined indicator fish species for each segment-based ecoregion. Indicator fish species reflected the fish fauna of each ecoregion in the midstream area, such as migratory Gobiidae of the south Kyushu ecoregion. Applying the segment-based ecoregion concept helps compare the biological integrity of fish fauna depending on a common environmental type between watersheds.

Experimental study on the dynamic deformation characteristics of volcanic soil "Shirasu" on equivalent granular void ratio

Shirasu is a volcamic soil which is widely distributed in South Kyushu in Japan. It contains non plastic fines which was created by its fragment of coarse particles. In this study, a series of bender element tests on Shirasu was performed with varying its fines content. As a result, it was observed that the shear modulus of Shiarasu was decreased with increasing the fines content although void ratio decreased as fines content increased. However, it was found that there is a unique relationship between shear moduli of Shirasu and the equivalent granular void ratio, in which the proper contribution factor b for fines was assumed. Based on the findings in the study, an empirical formula to express the shear moduls of Shirasu with various fines content was developed as the function of the fines content, the equivalent granular void ratio and the effective confining stress.

日本の地方都市における人口変化

Population trends of cities in rural regions of Japan are surveyed. First, population change rates during the period 2005–2010 of 401 cities in “Hokkaido and Tohoku,” “Hokuriku and Koshin-etsu,” “Chugoku and Shikoku,” and “Kyushu and Okinawa” regions are calculated. Few cities gained population, for example, Sapporo, Sendai, Fukuoka, and the satellite cities. On the other hand, cities that lost more than 5% of their populations are distributed in peripheral regions such as Sanriku Coast of Iwate and peninsulas and islands of west and south Kyushu. Generally, a positive relationship between population size of cities and those change rates is observed. Next, using long-term statistics, periods when cities in rural regions recorded peak populations are specified. The peaks tended to concentrate in two periods, that is, 1947–1955 and 2005–2010. Finally, cohort change rates are shown in 30 cities where prefectural government offices are located. Major cities such as Sapporo, Sendai, and Fukuoka have maintained stable inflows of young people since 1985. However, about one third of the prefectural capitals lost youngsters and received no populations of other age groups in recent years. From the viewpoint of population changes, almost all cities in rural regions in Japan are in a challenging situation. The “foothold” or “hub cities” in rural regions became exceptions in Japan.