Japan Archipelago Research Articles

Soil prokaryotic and fungal biome structures associated with crop disease status across the Japan Archipelago.

Archaea, bacteria, and fungi in the soil are increasingly recognized as determinants of agricultural productivity and sustainability. A crucial step for exploring soil microbiomes with important ecosystem functions is to perform statistical analyses on the potential relationship between microbiome structure and functions based on comparisons of hundreds or thousands of environmental samples collected across broad geographic ranges. In this study, we integrated agricultural field metadata with microbial community analyses by targeting 2,903 bulk soil samples collected along a latitudinal gradient from cool-temperate to subtropical regions in Japan (26.1-42.8 °N). The data involving 632 archaeal, 26,868 bacterial, and 4,889 fungal operational taxonomic units detected across the fields of 19 crop plant species allowed us to conduct statistical analyses (permutational analyses of variance, generalized linear mixed models, randomization analyses, and network analyses) on the relationship among edaphic factors, microbiome compositions, and crop disease prevalence. We then examined whether the diverse microbes form species sets varying in potential ecological impacts on crop plants. A network analysis suggested that the observed prokaryotes and fungi were classified into several species sets (network modules), which differed substantially in association with crop disease prevalence. Within the network of microbe-to-microbe coexistence, ecologically diverse microbes, such as an ammonium-oxidizing archaeon, an antibiotics-producing bacterium, and a potentially mycoparasitic fungus, were inferred to play key roles in shifts between crop-disease-promotive and crop-disease-suppressive states of soil microbiomes. The bird's-eye view of soil microbiome structure will provide a basis for designing and managing agroecosystems with high disease-suppressive functions.IMPORTANCEUnderstanding how microbiome structure and functions are organized in soil ecosystems is one of the major challenges in both basic ecology and applied microbiology. Given the ongoing worldwide degradation of agroecosystems, building frameworks for exploring structural diversity and functional profiles of soil microbiomes is an essential task. Our study provides an overview of cropland microbiome states in light of potential crop-disease-suppressive functions. The large data set allowed us to explore highly functional species sets that may be stably managed in agroecosystems. Furthermore, an analysis of network architecture highlighted species that are potentially used to cause shifts from disease-prevalent states of agroecosystems to disease-suppressive states. By extending the approach of comparative analyses toward broader geographic ranges and diverse agricultural practices, agroecosystem with maximized biological functions will be further explored.

Integrative taxonomy reveals a new gall midge genus and species (Diptera: Cecidomyiidae) developing in the flower buds of Pongamia pinnata (Fabaceae) in Japan

Abstract The Ryukyu Archipelago of Japan is a biodiversity hotspot with a remarkable diversity of endemic plants and animals. Although recent biodiversity surveys have highlighted that gall midges (Diptera: Cecidomyiidae) are the most species-rich taxon of insects worldwide, only 43 species are known presently in the Ryukyus. In this study, an undescribed gall midge developing in the flower buds of Pongamia pinnata (Fabaceae) was found on Ishigaki Island, southern Ryukyus, Okinawa Prefecture, Japan. Morphologically, the gall midge belongs to the supertribe Cecidomyiidi (Cecidomyiidae: Cecidomyiinae), but it does not fit the definition of any of the tribes and genera classified of Cecidomyiidi. A molecular phylogenetic analysis including the main tribes of Cecidomyiidi was conducted and reinforced the results of morphological examination. Therefore, Ishigakidiplosis karamaeElsayed,gen. nov. et sp.nov. was introduced for what is no doubt a previously unnamed species. This new genus sheds light on the unique gall midges of the Ryukyus and highlights the importance of conducting further surveys to elucidate their diversity and evolutionary relationships to other known gall midges.

Species diversity and distribution of genus Pampus (Pelagiaria: Stromateidae) based on global mitochondrial data

Due to the highly similar external morphology of the Pampus species, misidentifications frequently occur and hinder the understanding of the taxonomy and species distributions of the genus. In this study, we generated 271 mitochondrial sequences and obtained 1,226 sequences from the public databases to understand the species diversity and distributions of the genus Pampus. Most phylogenetic analyses and species delimitations congruently concluded seven valid species within the genus Pampus (i.e., P. argenteus, P. candidus, P. chinensis, P. cinereus, P. liuorum, P. minor, and P. punctatissimus). Sequences of P. argenteus are reported through the northern South China Sea to the Japan Archipelago, which covered the type locality of P. echinogaster. Sequences of P. echinogaster in the public databases are all identified as P. argenteus, suggesting that the species should be synonymized with P. argenteus. Furthermore, sequences of P. griseus were identical to our P. cinereus data and, therefore, should be treated as a synonym of the latter. Inference on divergence time and ancestral distribution implied that the genus Pampus originated in the central Indo-Pacific region around 8.35–11.33 million years ago (the late Miocene), associated with the rise of the Indonesian–Australian Archipelago biodiversity hotspot. The divergence between P. cinereus and P. liuorum dated back to 1.20–1.72 million years ago, which might be related to glacial isolation during the Mid-Pleistocene transition.

Mummified Seed Cones of Pinus prehwangshanensis sp. nov. (Subgenus Pinus, Pinaceae) From the Upper Pleistocene of Guangdong, South China: Taxonomical Significance and Implication for Phytogeography and Ecology

Anatomical characters of Cenozoic pine seed cones are known mainly from North American fossils, while data on cone anatomy of Cenozoic species from Asia remain scarce. To date, only one seed cone of Pinus from the Miocene of eastern China has been studied using micro-computed tomography (micro-CT). A new fossil-species, Pinus prehwangshanensis sp. nov., of mummified seed cones from the upper Pleistocene of South China is described using a combination of scanning electron microscopy (SEM) and micro-CT. The new fossil-species combines a mosaic of seed cone morphological and anatomical characters observed in the group of closely related East Asian extant species of subgenus Pinus, section Pinus, subsection Pinus, comprising Pinus taiwanensis, Pinus hwangshanensis, Pinus luchuensis, Pinus thunbergii, and Pinus densiflora. The data obtained indicate that the characteristic anatomical features of this group were formed no later than the end of the Pleistocene. Based on the external seed cone morphology, the East Asian pine fossils confirm the existence of floristic exchange between continental Asia and the Japan archipelago prior to the formation of the Sea of Japan and later, in the middle Miocene to the late Pliocene, when the connection between the Japanese islands and Eurasian continent became re-established. Pollen grains associated with the new fossil-species are similar to those of some extant pine species related to P. thunbergii. A taxonomic and ecological analysis of the Pleistocene plant taxa from the Maoming Basin suggests that the regional climate was a humid subtropical monsoon with hot wet summers and cool dry winters, similar to the present-day climate of northeastern Vietnam.

Long-distance dispersal from island to island: colonisation of an oceanic island in the vicinity of the Asian continent by the land snail genus Karaftohelix (Gastropoda: Camaenidae)

ABSTRACT Ullung Island is an oceanic island in the Sea of Japan about 130 km distant from the Korean peninsula. The biota of this oceanic island is thought to be derived from the closest continental region while the importance of long-distance dispersal from other areas for the formation of the Ullung Island biota was considered negligible. In this study, we have examined the origin of the Ullung Island-endemic land snail Karaftohelix adamsi (Kuroda & Hukuda, 1944) using a molecular phylogenetic approach with two mitochondrial (COI and 16S rRNA) and nuclear (ITS regions) DNA sequences. Our results revealed that K. adamsi has originated from the northernmost region of the Japanese archipelago or Sakhalin Island, most likely from Rebun Island of Hokkaido, by long-range dispersal across a distance of 1200 km. This finding reveals that the biota of the oceanic Ullung Island has not exclusively originated from the Asian mainland, but that some elements have originated from the more distant archipelago of Japan and the Far East of Russia.

An unknown species of Leucochloridium (Trematoda: Leucochloridiidae) from northern Honshu, Japan.

Pulsating broodsacs of Leucochloridium sp. (Trematoda: Leucochloridiidae) were found from amber snails (Succinea lauta) in Iwate, the northern part of Honshu, Japan. A pattern with red-brown vertical stripes was characteristic of the broodsac. Very similar broodsacs were already detected from Okinawa Islands, the southern archipelago of Japan, and tentatively identified as Leucochloridium cf. passeri. A phylogenetic analysis based on DNA sequences of mitochondrial cytochrome c oxidase subunit 1 (cox1) showed that Leucochloridium sp. is different at species level from L. cf. passeri and that both species are related to Leucochloridium vogtianum from Europe. In this study the definitive identification of larval Leucochloridium sp. was impossible, but the resulting phylogeny confirmed that at least 4 species of Leucochloridium are distributed in Japan, depending on locality and climate. The DNA barcode generated in this study will be useful in detecting the adult stage of Leucochloridium sp. from birds.

Population Genetic Differentiation on the Hydrothermal Vent Crabs Xenograpsus testudinatus along Depth and Geographical Gradients in the Western Pacific

Connectivity in deep-sea organisms must be considered across both depth gradient and horizontal geographical scales. The depth-differentiation hypothesis suggests that strong environmental gradients (e.g., light, temperature, pressure) and habitat heterogeneity in the deep-sea can create selection pressure, and this can result in genetic population divergence. The hydrothermal vent crab Xenograpsus testudinatus (Xenograpsidae) is common in vents at Kueishan Island, Taiwan, ranging from 10 to about 300 m depths. Xenograpsus testudinatus has also been found in shallow water vents (3–20 m) at Kagoshima and the Izu archipelago of Japan. We examine the sequence divergences in the mitochondrial COI, 16S rRNA and D-loop genes, to test the hypothesis that there is significant genetic differentiation among populations of X. testudinatus along the depth gradient at Kueishan Island (30, 200, 209–224 and 250–275 m), and among different geographical regions (Kueishan, Kagoshima and the Izu archipelago) in the West Pacific. There is neither significant population differentiation among shallow or deep-sea vents, nor between geographical locations. Vertical migration of zoea, upwelling on the eastern coast of Taiwan and the strong effect of the Kuroshio Currents has probably resulted in a high level of planktonic larval dispersal of X. testudinatus along the depth and geographical gradients in the Western Pacific.

ICESat-2 Applications for Investigating Emerging Volcanoes

Submarine volcanism in shallow waters (<100 m), particularly in remote settings, is difficult to monitor quantitatively and, in the rare formation of islands, it is challenging to understand the rapid-paced erosion. However, these newly erupted volcanic islands become observable to airborne and/or satellite remote sensing instruments. NASA’s ICESat-2 satellite laser altimeter, combined with visible imagery (optical and microwave), provide a novel method of evaluating the elevation characteristics of newly emerged volcanoes and their subaerial eruption products. Niijima Fukutoku-Okanoba (NFO) is a submarine volcano 1300 km south of Tokyo (Ogasawara Archipelago of Japan) that periodically breaches the ocean surface to create new islands that are subsequently eroded. The recent eruption in August 2021 is a rare opportunity to investigate this island evolution using high-resolution satellite datasets with geodetic-quality ICESat-2 altimetry. Lansdat-8 and Planet imagery provide a qualitative analysis of the exposed volcanic deposits, while ICESat-2 products provide elevation profiles necessary to quantify the physical surface structures. This investigation determines an innovative application for ICESat-2 data in evaluating newly emerged islands and how the combination of satellite remote sensing (visible and lidar) to investigate these short-lived volcanic features can improve our understanding of the volcanic island system in ways not previously possible.

Stratigraphic reconstruction of the lower–middle Miocene Goto Group, Nagasaki Prefecture, Japan

AbstractThe Goto Islands are located at the westernmost tip of the Japan archipelago, and preserve a lower–middle Miocene sedimentary sequence deposited during rifting of the continental margin and opening of the Sea of Japan. The stratigraphy of the Goto Group and new K–Ar, fission‐track, and U–Pb age data were used to determine the initial conditions of rifting in southwest Japan. The thickness of the Goto Group is 2000–3000 m. The lower unit (ca. 22–17.6 Ma) consists of thick, greenish, volcaniclastic rocks with basaltic volcanic material, representing the initial stages of continental rifting. The middle unit (ca. −17.6 Ma) consists of alternating sandstones and shales deposited in lacustrine and meandering fluvial environments in a syn‐rift sedimentary basin during a period of volcanic activity. The upper unit (ca. 17.6–16.8 Ma) consists of thick sandstones of fluvial–deltaic facies that were deposited during rapid subsidence at the continental margin. This unit was deposited by a large fluvial system that flowed into the Sea of Japan. These sequences contain relatively cooler to warmer flora (Daijima‐type) and record the warm period of the Miocene Climatic Optimum. The Goto felsic volcanic rocks (16.8 ~ 15.4 Ma) unconformably overlie the Goto Group, and granitic magmatism (ca. 16–14.5 Ma) occurred after sedimentation of the Goto Group. The widespread lacustrine, meandering–braided fluvial, and vast deltaic systems of the Goto Group, and felsic volcanism, were formed due to rapid subsidence that produced a horst‐and‐graben basin during the early stages of rifting of a volcanic arc along the eastern margin of Eurasia. These events occurred from 22.0 to 16.8 Ma before and during the formation of the Sea of Japan.

Significant Asymmetry of the Bilateral Upper Extremities of a Skeleton Excavated from the Mashiki-Azamabaru Site, Okinawa Island, Japan.

The human skeleton of a young adult male with marked asymmetry of the bilateral upper extremities was excavated from the Mashiki-Azamabaru site (3000–2000 BCE) on the main island of Okinawa in the southwestern archipelago of Japan. The skeleton was buried alone in a corner of the cemetery. In this study, morphological and radiographic observations were made on this skeleton, and the pathogenesis of the bone growth disorder observed in the left upper limb was discussed. The maximum diameter of the midshaft of the humerus was 13.8 mm on the left and 21.2 mm on the right. The long bones comprising the left upper extremity lost the structure of the muscle attachments except for the deltoid tubercle of the humerus. The bone morphology of the right upper extremity and the bilateral lower extremities was maintained and was close to the mean value of females from the Ohtomo site in northwestern Kyushu, Japan, during the Yayoi period. It is assumed that the anomalous bone morphology confined to the left upper extremity was secondary to the prolonged loss of function of the muscles attached to left extremity bones. In this case, birth palsy, brachial plexus injury in childhood, and acute grey matter myelitis were diagnosed. It was suggested that this person had survived into young adulthood with severe paralysis of the left upper extremity due to injury or disease at an early age.

Existe-t-il un Paléolithique inférieur au Japon ?

All Lower Paleolithic sites discovered by Mr. Shinïchi FUJIMURA from 1981 to 2000 were falsified by himself. We wonder if Lower Paleolithic sites really exist (corresponding to a period of 30,000years ago in Japan) in the archipelago of Japan. We examined cultures of sites likely dating to the Early Upper Paleolithic and Lower Paleolithic discovered in the archipelago of Japan. While Japan was continuous with the continent in the Mindel glaciation (400,000years ago) or in the Riss glaciation (200,000years ago), Homo erectus or Homo heidelbergensis with the lithic industry of the Acheulean arrived in the archipelago of Japan. Thereafter, they survived on the islands of Japan cut the continent to the Upper Paleolithic while keeping the industry.

Le Paléolithique supérieur du plateau de Musashino et les hauteurs de Tama aux alentours de Tokyo

The Upper Paleolithic at the region of Tokyo that itself called also the Japanese Preceramic age that possesses a large number of excavations and those studies during the dawn of Paleolithic study in this country. The Preceramic age or the Upper Paleolithic has been raised the curtain by the discovery of a piece in obsidian, in 1949, in the loam of Kantô, at Iwajyuku site. We explain above, on the stratigraphy, the chronology and the situation and the evolution of site around Tokyo. It is a region to the highest density of the Upper Paleolithic sites in the archipelago of Japan and the systematic excavation according to the stratigraphy of loam formation has been done for the first time in the country. The authentic chronology has been proposed to the years 60s that based on the discovered lithic industries on the plateau of Sagamino and Musashino. This chronology was used for a long time that it made a role like a norm for the whole country. Not only, after again an accumulation of the research until the present, we understand the different periodic activities between the Tama hills, the plateau of Musashino, the plateau of Sagamino, the North of Kantô district and the plateau of Simôssa. Of course, there is a complex circumstance that the apparition and the disappearance of various types of lithic instruments are different, and every type tools are not universal around Tokyo area, in the district of Kantô. The final of Upper Paleolithic on the archipelago of Japan divides extensively in two parts East-west that the East of Japan is characterized by the well-organized aspect microlithic tendency and the west is characterized by the trend of microlite, trapeze and tool on transverse blade. In such general tendency, the region of Kantô is located therefore in the center on the archipelago of Japan that it showed sets of every different time.

Le Paléolithique de l’île de Kyûshû

The Upper Paleolithic of this region divides in five chronological stages. The first stage is an oldest period on the archipelago of Japan. The lithic industry of the stage is composed by the denticulate, the pointed scraper, the pick and the bifacial tool. The second half of the first stage is characterized the emergence of Kiridashi type backed knife and trapezoidal backed knife. The debitage (flaking) of the first half and the second half is non-blade technique. The second stage is characterized newly by the apparition of willow leaf type backed knife and partial retouching backed knife. The knife-to-back of the type of Kiridashi and the trapezoidal knife-to-back exist again while constantly joining the willow leaf type backed knife and the partial retouching baked knife. The blade debitage was present, principally the one of various flakes. As for the second half of the second stage, the willow leaf type backed knife and the partial retouching backed knife are represented mainly, besides the Kiridashi type baked knife and the trapezoidal backed knife mingled with this typological composition. The debitage was founded on the blade technique. The point on flake (tanged flake point) and the trihedral faced point appeared at the third stage that is a big instrument of hunt. It is likely that the behavior for hunting the big game would have been brought while passing by the land-bridge toward the Kyushu Island during the Maximum-Coldness of the last glaciation. Regarding the fourth stage, the point on flake disappeared, and the industry is essentially composed of trihedral faced point and the spear type point. The flat trihedral faced point and spear type point appeared, and the trihedral faced point appeared on the western part of South-Kyûshû and the part of northern Kyûshû. The culture of the trihedral faced point tips at the third stage on the Kyûshû Island that prolongs until the concerned stage. The fifth stage is the end of the Upper Paleolithic that is characterized by the Microlithic Culture. It is characterized by the miniaturize of the backed knife. At the end, the microlithisation resuscitates at the end of the Upper Paleolithic.

Le Paléolithique des îles du Sud-Ouest du Japon

There are two lithic industries in the beginning of the Upper Paleolithic including the vestiges that have been discovered in the islands of Oshumi, close to the island of Kyushû. This lithic industry is characterized by the presence of axes with partially polish cutting, denticulate, hammers and millestones that are common in western Japan. It is characterized by numerous lithic instruments for the treatment of the plant food. The discovered vestiges of which one found the pebbles cluster inside pitfalls that are the oldest on the archipelago of Japan. According to these particularities of the lithic industry and vestiges, it is likely that this human group is semi-settled. And this human group of the beginning Upper Paleolithic was identical typologically and technically to the human group of the island of Kyushû. Therefore, it is possible that they came down from the southbound Kyushû Island, to the concerned islands. As for the islands of Amami, we investigated sites, nevertheless all that have been unearthed, in small extents provided a small quantity of the archaeological material. Indeed, one could not seize very well retails until now. There is a mixture of various, non-resolute opinions. The islands of Okinawa and those of Sakishima in southern extremity of the Japanese territory provided humans rests of the Upper Paleolithic, nevertheless no lithic industry of the same time have been found. Thereafter of the situation, the origins of the culture and the technique concerned the human rests remain unclear.

Le Paléolithique supérieur dans la péninsule coréenne et l’archipel du Japon

There is one decisive gate between the Asian continent and the archipelago of Japan which is the strait of Tsushima that exists between the Korean peninsula and the archipelago. The strait is very narrow; however, the depth is relatively deep. If the sea level did not fall down to at least 130 meters below the present level, the terrestrial bridge would not be formed there. We know the former case concerning the first human population of which crossed this maritime gate of human groups 50,000 years ago. One supposes that the men did not have any means to cross there without the terrestrial bridge previous to 50,000 years. According to the studies of the abyssal drills of the Sea of Japan that one noted several lowering of the sea level according to the marine isotopic stages (MIS): 2, 6, 10, 12, 16, 18 and 20. With regard to the marine isotopic stage 2 that correspond to the Maximum-coldness of the last glacial when the sea dropped in below 125 meters in relation to the present level. According to study of the seismic stratigraphy and according to the obtained ages of seabed sediments by the method of carbon 14 that one concluded the concerned strait remained always like a marine channel and narrow during the last glacial (Park et al., 2000). We notice the typological common points between the lithic industry of the Korean peninsula and the one of the Kyushu island during the marine isotopic stage 2 (MIS-2) which are the tanged point (flake point), the bifacial point to triangular section (point to three retouched faces), etc. However, there are some differences in the composition of tools and the fabrication technique. Regarding the cultural origin and the big human migration, we cannot prove them for now. Such situation showed that some obstacles existed between such two regions. There are no common features on the flaking technique and the typology before 50,000 years in these two regions since we do not have any affirmative overdraft.

日本列島における この35 年間の木材遺体研究の展開と展望

日本列島における この35 年間の木材遺体研究の展開と展望

Population genetic structure of the insular Ryukyu flying fox Pteropus dasymallus

AbstractSmall isolated populations are vulnerable to both stochastic events and the negative consequences of genetic drift. For threatened species, the genetic management of such populations has therefore become a crucial aspect of conservation. Flying foxes (Pteropus spp, Chiroptera) are keystone species with essential roles in pollination and seed dispersal in tropical and subtropical ecosystems. Yet many flying fox species are also threatened, having experienced dramatic population declines driven by habitat loss and hunting. The insular Ryukyu flying fox (Pteropus dasymallus) ranges from the Ryukyu Archipelago of Japan through Taiwan to the northern Philippines and has undergone precipitous population crashes on several islands in recent decades. To assess the population genetic structure and diversity in P. dasymallus, and its likely causes, we analyzed mitochondrial and microsatellite DNA. Both markers showed significant genetic differentiation among most island populations, with mitochondrial haplotypes showing some mixing across the regions, likely reflecting historical colonization and/or dispersal events. In contrast, microsatellite markers showed an overall pattern of isolation by distance; however, this pattern appeared to be driven by the presence of deep ocean trenches between geographically distant populations. Thus, the current distribution of P. dasymallus and its subspecific diversity appear to have arisen through vicariance coupled with a long history of restricted gene flow across oceanic barriers. We conclude that isolated island subgroups should be managed separately, with efforts directed at reducing further declines in genetic diversity.

Classification of volcanic soils in the Soil Classification System of Japan and verification based on forest soils

ABSTRACT In 2017, the Japanese Society of Pedology (the Fifth Committee for Soil Classification and Nomenclature) established the Japanese soil classification system. In the classification system, all the soils derived from volcanic ejecta (volcanic ash, pumice, scoria, etc.) are classified into the Great Group of Andosols, excluding Man-made and Organic soils, although some volcanic soils were classified into other soil groups, such as the Podozols and Brown forest soils in the previous classification systems. The aim of the present study was to verify and propose revision for the new system based on physicochemical data collected from forest soils across the Japan archipelago. Approximately 20% of the forest soils have andic properties and were classified into the Andosols in the Soil Classification System of Japan, which is consistent with the Andisols in Soil taxonomy and Andosols in World Reference Base for Soil Resources, excluding a few soils with low andic horizon thickness. Many other forest soils that were not classified into Andosols possessed some of the regosolic andic properties, and it was challenging to classify them into Regosolic Andosols or Brown forest soils. Therefore, additional diagnostic activities on the volcanic ejecta and glass are required to classify such soils appropriately. In the new classification system, the Fulvic Andosols soil group was abolished and substituted with the Humic and Brown-humic subgroups under the Non-allophanic and Allophanic Andosols, respectively. The revision was consistent with the traditional forest soil classification system. In conclusion, the classification of volcanic soils in the Soil Classification System of Japan was verified using forest soil data in Japan. Abbreviations CFSJ: Classification of Forest Soils in Japan (1975); CSCSJ: Comprehensive Soil Classification System of Japan, 1st approximation (2011); SCSJ: Soil Classification System of Japan (2017); ST: Keys to Soil taxonomy, Twelfth Edition (2014); USCSJ: Unified Soil Classification System of Japan, 2nd Approximation (2002); WRB: World Reference Base for Soil Resources (2014, 2015 updated)

NOAA Marine Geophysical Data and a GEBCO Grid for the Topographical Analysis of Japanese Archipelago by Means of GRASS GIS and GDAL Library

This article analyzes topographical and geological settings in the Japan Archipelago for comparative raster data processing using GRASS GIS. Data include bathymetric and geological grids in NetCDF format: GEBCO, EMAG2, GlobSed, marine free-air gravity anomaly and EGM96. Data were imported to GRASS by gdalwarp utility of GDAL and projected via PROJ library. Methodology includes data processing (projecting and import), mapping and spatial analysis. Visualization was done by shell scripting using a sequence of GRASS modules: ‘d.shade’ for relief mapping, ‘r.slope.aspect’; for modelling based on DEM, ‘r.contour’ for plotting isolines, ‘r.mapcalc’ for classification, ‘r.category’ for associating labels, and auxiliary modules (d.vect, d.rast, d.grid, d.legend).The results of the geophysical visualization show that marine free-air gravitational anomalies vary in the Sea of Japan (–30 to above 40 mGal) reflecting density inhomogeneities of the tectonic structure, and correlating with the geological structure of the seafloor. Dominating values of geoid model are 30–45 m reflecting West Pacific rise, determined by deep density inhomogeneities associated with the mantle convention. Sediment thickness varies across the sea reflecting its geological development with density of 2 km in its deepest part and thinner in central part (Yamato Rise). The aspect map and reclassified map express gradient of the steepest descent.

A possible new oldest pottery group in the Southern Ryukyu Islands, Japan: Comparative analysis of elemental components of potsherds from the Shiraho-Saonetabaru Cave Site

Ancient potsherds dating to about 10,000 years BP excavated in the Shiraho-Saonetabaru (SRS) cave site in the Southern Ryukyu Islands in the southwestern part of Japan archipelago are the oldest example of pottery usage in the island region of the southern East China Sea, including the Northern and Southern Ryukyu Islands, Taiwan, and the Philippines. However, their cultural continuity and relationship with the following period or with any other regions have not been elucidated as their condition made analysis extremely difficult.In this study, we conducted a chemical analysis of typical potsherds from the Shiraho-Saonetabaru cave site using an X-Ray fluorescence microscope. Although analyzing their visible peculiarities was difficult because of fragmentation and chemical analysis with sample destruction was impossible because of their scarcity value, our method enabled us to unravel the elemental characteristics of their paste despite possessing only very small samples that could not be destroyed. We also compared these oldest potsherds with those of the following period in the same region using statistical multivariate analysis; the results showed that the oldest potsherds differed from the later ones, suggesting a new model of chronological transition for the first pottery usage in this region. This study represents a novel approach to identifying the oldest potsherds in the southern East China Sea region, and also provides a new solution to the problem of what to do with smaller ceramic fragments that are relatively rare.