North Hokkaido Research Articles

Genetic relations among wild populations of Saccharina japonica in the western North Pacific

We performed microsatellite polymorphism analysis for wild populations of Saccharina japonica, a kelp species that is, among wild production areas, mainly produced in Hokkaido, is indispensable as an ingredient of Japanese food that differs in application and value depending on the origin (variety), growing in southern Sakhalin, Primorsky Krai, and Hokkaido to investigate the genetic relations among the populations. A total of 230 alleles (Polymorphic Information Content: 0.08–0.69) were detected from 18 loci. In the analysis by region, the differentiation index (Fst) and genetic distance (DS) were lower between the Sakhalin southwestern-end populations or the Sakhalin southern coast populations and the Hokkaido populations. However, gene structure analysis showed that the clusters dominant in the kelp in the Sakhalin or Hokkaido population group also existed in the other population group, suggesting that genes are exchanged between these regions. When analyses were performed by origin, one of the Sakhalin southwestern-end populations formed a clade with the Hokkaido populations in the phylogenetic tree, both having similar genetic structure, and the Fst and DS values were particularly low with the Hokkaido East populations (S. japonica var. diabolica. The Fst and DS values were also low between the five Sakhalin southern populations – a sister group with the Hokkaido East populations in the phylogenetic tree – and the North Hokkaido populations (S. japonica var. ochotensis), indicating that these Sakhalin southwestern-end and southern populations may be used as alternatives to Hokkaido populations for culinary purposes.

Stream water quality in relation to watershed‐scale practical forest management in a cool‐temperate natural forest in northern Japan

AbstractThe water chemistry of a stream reflects the biogeochemical processes occurring in upstream forests. Anthropogenic disturbances in forests, such as cutting trees, altering the nitrogen (N) cycle, and increase in N leaching from the soil to streams, potentially cause acidification or eutrophication downstream. In forests with dense understory vegetation, mechanical site preparation following tree cutting is commonly used to improve the early establishment of tree seedlings. In cool‐temperate forests in northern Hokkaido, Japan, dense understory vegetation (mainly comprising Sasa dwarf bamboo) inhibits forest regeneration after tree cutting. Soil scarification is a common site preparation technique for eliminating Sasa bamboo and improving forest regeneration. Long‐term data are useful for examining the temporal changes in stream water chemistry exposed to different specific forest management practices under changing environment (e.g., climate change and atmospheric N deposition). For 14 years (2003–2016), we observed the stream water chemistry in naturally forested watersheds and at one point after the confluence of all streams in Uryu Experimental Forest of Hokkaido University (North Hokkaido Experimental Forests Site of JaLTER) in northern Japan. We also monitored stream discharge, water level and stream water temperature in each watershed. Water samples were collected from the outlets of 10 watersheds. The forest management practice in each watershed includes clear‐cutting, soil scarification in sparse forest with dense understory Sasa, and clear‐cutting and soil scarification followed by soil replacement. Long‐term data in the six unmanaged watersheds are also valuable as a background information to analyze the effect of long‐term climate, environment and vegetation changes on stream water chemistry. The measured water quality data of 1,873 water samples include the ion concentrations (Cl−, NO3−, SO42−, Na+, NH4+, K+, Mg2+, and Ca2+), pH, and electrical conductivity (EC) in the stream water. The range of the concentrations of Cl−, NO3−, SO42−, Mg2+, and Ca2+ in the stream water across all the watersheds throughout the observed periods (minimum to maximum) were 3.35–23.67, 0.01–8.68, 0.83–4.01, 0.45–2.55 and 0.72–6.16 mg L−1, respectively. Similarly, the stream pH and EC ranged from 6.04 to 7.53 and 3.14 to 9.47 mS m−1, respectively.The complete data set for this abstract published in the Data Paper section of the journal is available in electronic format in MetaCat in JaLTER at http://db.cger.nies.go.jp/JaLTER/metacat/metacat/datapaper%202020‐04.1/jalter‐en. [Correction added on 7 September 2020, after first online publication: JaLTER URL has been updated.]

Submarine Landslides on the Western Slope of the Kuril Basin, Sea of Okhotsk

Landslide processes on the western slope of the Kuril Basin were studied using bathymetry and seismic data obtained under the international KOMEX and SSGH projects. Slope areas containing landslides, landslide blocks and mass-transport deposits were distinguished. Large-scale landslides occupying an area of more than 100 km2 are located in such areas of open continental margins as the slopes of the North Hokkaido Marginal Plateau and Terpeniya Ridge. Landslide blocks up to 2 km in size and mass-transport deposits are located in submarine canyons and fans in Terpeniya Bay. The age of landslides has been estimated as Middle Pleistocene–Holocene. Landslides are most likely triggered by seismic activity and gas saturation of sediments. Subsequent slope failure seems quite probable within the study area, and landslides capable of generating tsunamis may occur.

北海道北部,愛別-上川周辺の後期新生代火成岩類のK-Ar年代

北海道北部,愛別-上川周辺の後期新生代火成岩類のK-Ar年代

The earliest pottery of the eastern part of Asia: Similarities and differences

There are many reasons why the earliest pottery of East Asia is so interesting for researchers. One of them is that it is a unique source for reconstruction of cultural diversity within Late Pleistocene. According to Russian archaeologists, for such reconstruction it is necessary to find out how pots were made (clay paste composition, way of shaping, surface treatment, firing and decorating) and how pots looked. Based on this perspective it is possible to divide the earliest ceramic assemblages of East Asia into three groups. First of them include the Incipient Jomon ones, their differentia is plain (without rough surface treatment) pottery ornamented by hands (pinch, nail impression, clay application) and a comparatively high level of unification. Second group comprises Osipovka assemblages compactly located within the Low Amur river basin. They are quite polymorphous but have common distinctive traits such as grog temper, comb design of different pattern and combing surface treatment. The third group is the most extended and diverse. Its key feature is only cord surface treatment in a very special manner of rolling of a cord wrapped stick. Astoundingly, the assemblages with this trait occupy the territory from southernmost China to Transbaikalia (Studenoe-1, Ust-Karenga), and Middle Amur river basin (Gromatukha). So, it is possible to say they have Inner-Asia spatial distribution. Thus, we can see three different areas of spatial distribution of earliest ceramic assemblages within the eastern part of Asia. Tracking their Holocene fate, we can find confirmation of such conclusion and suppose that Sakhalin, North Hokkaido and Russia Maritime form the forth – non-ceramic – area in Late Pleistocene.

2-B01 北海道,白滝黒曜石流紋岩溶岩群のマグマ活動(その1) : 黒曜石の岩石組織・化学組成と溶岩の内部構造(北海道の岩石学,口頭発表)

2-B01 北海道,白滝黒曜石流紋岩溶岩群のマグマ活動(その1) : 黒曜石の岩石組織・化学組成と溶岩の内部構造(北海道の岩石学,口頭発表)

2-B02 北海道,白滝黒曜石流紋岩溶岩群のマグマ活動(その2) : マグマ温度と噴出時の粘性係数,溶岩流流動過程(北海道の岩石学,口頭発表)

2-B02 北海道,白滝黒曜石流紋岩溶岩群のマグマ活動(その2) : マグマ温度と噴出時の粘性係数,溶岩流流動過程(北海道の岩石学,口頭発表)

Lead isotope ratios in six lake sediment cores from Japan Archipelago: Historical record of trans-boundary pollution sources

Sediment cores from six lakes situated from north to south on the Japanese Archipelago were collected during 2009–2010 to investigate the hypothesis that deposition of lead (Pb) was coming from East Asia (including China, South Korea and eastern part of Russia). Accumulation rates and ages of the lake sediment were estimated by the 210Pb constant rate of supply model and 137Cs inputs to reconstruct the historical trends of Pb accumulation. Cores from four lakes located in the north and central Japan, showed clear evidence of Pb pollution with a change in the 206Pb/207Pb and 208Pb/207Pb ratios in the recent sediment as compared to the deeper sediment. Among the six studied lakes, significant inputs of anthropogenic lead emissions were observed at Lake Mikazuki (north Hokkaido in north Japan), Lake Chokai (north of Honshu), and Lake Mikuriga (central part of Honshu). Pb isotopic comparison of collected core sediment and previously reported data for wet precipitation and aerosols from different Asian regions indicate that, before 1900, Pb accumulated in these three lakes was not affected by trans-boundary sources. Lake Mikazuki started to receive Pb emissions from Russia in early 1900s, and during the last two decades, this lake has been affected by trans-boundary Pb pollution from northern China. Lake Chokai has received Pb pollutant from northern China since early 1900s until 2009, whereas for the Lake Mikuriga the major Pb contaminant was transported from southern China during the past 100years. The results of our study demonstrate that Japan Archipelago has received trans-boundary Pb emissions from different parts of East Asian region depending on location, and the major source region has changed historically.

Variations in the geochemical structure of the mantle wedge beneath the northeast Asian marginal region from pre- to post-opening of the Japan Sea

Deep asthenospheric processes and the dynamic mechanism of magmatism in the northeast Asian marginal region are of significant interest but have been difficult to study in detail. We completed comprehensive studies on Japan Sea basalts including petrography, whole-rock major and trace elements, Sr–Nd–Pb isotopic compositions, and K–Ar geochronology, then combined our results with previous research to study the tectonic evolution of northeast Asia. The Japan Sea basalts, divided into Upper and Lower layers of Site 794 (US794, LS794), and Upper and Lower layers of Site 797 (US797, LS797) based on their stratigraphic level, belong to the calc-alkalic series and are characterized by flat HREE with significantly positive anomalies of Ba, Sr, and Pb, and slight anomalies of Eu (δEu=0.81–1.21). The US797 sample group has lower LREE, LILE and relatively depleted radioactive isotope ratios (87Sr/86Sr=0.704051–0.704254; 143Nd/144Nd=0.513035–0.513139; 206Pb/204Pb=17.758–18.223), whereas the sample groups LS797, US794, and LS794 have relatively higher incompatible elements and slightly enriched isotopic values (87Sr/86Sr=0.704248–0.705222; 143Nd/144Nd=0.512705–0.512917; 206Pb/204Pb=18.077–18.377) due to the involvement of Pacific subducted fluid and sediments. K–Ar and 40Ar–39Ar geochronological data indicate age ranges of LS797, US794, and LS794 samples of 17.7±0.5–21.2±0.8Ma, significantly older than those of US797 (15.1±0.9–17.2±0.7Ma). Our data compiled with other data show sharply defined Sr–Nd isotopic variations of the Cenozoic basalts from Sikhote-Alin, the Japan Sea, the back-arc side of NE Japan and SW Hokkaido, and north Hokkaido from a slightly enriched to a depleted isotopic signature at 23–24Ma, 17±2Ma (15–19Ma), 15Ma, and >12Ma, respectively, indicating that the upwelling asthenosphere beneath northeast Asia progressed eastward relative to the lithosphere. We conclude that the temporal and spatial variations of basaltic magma sources in the northeast Asian marginal region are closely associated with the extension of the Japan Sea.

Variation in regional diet and mandibular morphology in prehistoric Japanese hunter–gatherer–fishers

Previous research has identified a relationship between mandibular morphology and diet (e.g., coarse or tough diets result in more robust mandibles). Prehistoric Japan is an excellent place to explore the significance of this relationship in shaping mandibular morphology due to the pronounced regional dietary variation. South/West Honshu Jōmon engaged in broad spectrum foraging, Northeastern Honshu Jōmon were fisher–gatherers, Hokkaido Jōmon were maritime (sea mammal) foragers. We test the hypothesis that diet variation across temporal and spatial zones will be reflected in mandibular morphological traits. Metric measurements were utilized to test for regional differences with both archaeological time period and biological sex as covariants. ANOVA results for region with time period as a covariate indicates all variables except corpus height and breadth are significantly different among regions but for the time period covariate, only corpus breadth and dimensions of ascending ramus are significant. ANOVA for region with biological sex as a covariate indicates all variables except corpus height are significantly different. Biological sex as a covariate demonstrates significant p-values for chin height, bicondylar breadth and minimum ascending ramus breadth. Generally, North Hokkaido and Southwest Hokkaido, exhibit the largest mandibular ascending rami and tallest anterior mandibles, whereas Northeast and South/West Honshu have smaller mandibles. Multivariate analysis indicates a separation between North and Southwest Hokkaido and South/West Honshu, whereas Northeast Honshu partially overlaps these dietary zones. Differences in mandibular morphology are better explained by regional diets than by temporal trends and biological sex.

Survey of tick fauna and tick-borne pathogenic bacteria on Rishiri Island, off north Hokkaido, Japan

Tick fauna and tick-borne pathogenic bacteria were surveyed on Rishiri Island, off the northwest coast of Hokkaido, Japan. We collected Ixodes pavlovskyi and Ixodes persulcatus from vegetation, Ixodes angustus from Myodes rex, and Ixodes tanuki from Mustela itatsi and Felis silvestris catus. Borrelia garinii, the cause of Lyme disease in Eurasia, and Rickettsia helvetica and Rickettsia tarasevichiae of the spotted fever group were detected from I. persulcatus. These results indicate a potential threat of Lyme disease and spotted fever group rickettsiosis on Rishiri Island. It is possible that an introduced species, Mu. itatsi, contributes to maintenance of the infectious diseases as a blood source for the ticks on the island.

Petrology and Geochemistry of Adakitic Dacites and High-MgO Andesites, and Related Calc-alkaline Dacites from the Miocene Okoppe Volcanic Field, N Hokkaido, Japan

In the Okoppe area of North Hokkaido, Japan, the eruption of adakitic and calc-alkaline dacites was followed by high-Mg andesite (HMA) and calc-alkaline dacite during the Middle Miocene (12–10 Ma). Adakitic dacite is characterized by high Sr/Y and low Y, with Sr and Nd isotopic compositions identical to those of mid-ocean ridge basalt. It has higher MgO contents than adakites generated by experimental melting of metabasalt and amphibolite, and higher Ni and Cr contents than either Archean trondhjemite–tonalite–granodiorite or Early Cretaceous adakitic granites, which are considered to represent partial melts of subducted oceanic crust. This provides compelling evidence that adakitic dacite magma from Okoppe resulted from interaction of a melt derived from subducted oceanic basaltic crust and the overlying mantle wedge peridotite, with little modification to the adakitic melt signature and Sr and Nd isotopic values. The compositional variations in the Toyono adakitic dacite and associated calc-alkaline dacite probably resulted from mixing of the reacted magma and an evolved silicic dacite magma formed by fractional crystallization of the reacted magma. A disequilibrium phenocryst assemblage in the HMA may result from mixing of boninite and silicic andesite that resulted from crustal melting. Calc-alkaline dacites associated with the HMA were derived by fractional crystallization of silicic andesite and assimilation of crust with an enriched Sr isotopic signature. The most likely tectono-magmatic model for the production of adakitic dacite and HMA involves upwelling of hot asthenosphere into the subcontinental lithosphere beneath North Hokkaido and the back-arc side of the NE Japan arc, coincident with the spreading of the Kurile back-arc basin and Japan Sea back-arc basin. This resulted in a high geothermal gradient in the mantle wedge beneath North Hokkaido. The subsequent melting of a limited part of the cool oceanic crust subducting beneath Hokkaido produced adakitic magmas, which interacted with the overlying mantle wedge peridotite. These magmas subsequently reacted with an evolved calc-alkaline melt en route to the surface. Boninitic magma derived from the ascending hot asthenosphere in part reacted with crust-derived silicic andesitic magma, undergoing simultaneous fractional crystallization.

Melting of crustal rocks as a possible origin for Middle Miocene to Quaternary rhyolites of northeast Hokkaido, Japan: Constraints from Sr and Nd isotopes and major- and trace-element chemistry

Felsic volcanic rocks (mainly rhyolites) and basalts found in northeast Hokkido, Japan, result from intense volcanism during the Middle Miocene (14–9Ma), Late Miocene (8–6Ma) and Pliocene to Quaternary (5–2Ma). Rhyolites were examined to determine any genetic relationship to coeval basalts, high magnesian andesite (HMA), lower crustal rocks and mantle peridotite.Rhyolites have initial Sr and Nd isotopic ratios (SrI and NdI) which overlap with coeval north Hokkaido basaltic rocks and HMA. Previously published Sr and Nd isotopic data show that most Middle Miocene to Quaternary (14–0Ma) basaltic rocks from north Hokkaido have a relatively narrow SrI- and NdI- range (SrI 0.70299 to 0.70400, and NdI 0.51281 to 0.51311), with no temporal variation in either SrI or NdI. Basalt and HMA from three locations are, however, more undepleted in terms of both SrI and NdI than other north Hokkaido basaltic rocks. Some of rhyolites (termed undepleted rhyolites here) have similar SrI and NdI to some north Hokkaido basalts and HMA. Rhyolites with similar SrI and NdI to other north Hokkaido basaltic rocks are termed depleted rhyolites.Although the similarity of SrI and NdI between rhyolites and coeval basalts and HMA can be accounted for by fractional crystallization, this process is inconsistent with the REE chemistry of basalts, HMA and rhyolites, and with the results of fractional crystallization modeling. However, a few rhyolites may result from the fractional crystallization of basaltic and HMA magmas with assimilation of some metasedimentary rocks. Small degrees of partial melting of a metazomatized mantle peridotite is an unlikely mechanism to explain the genesis of rhyolites according to REE chemistry and partial melt modeling of an amphibole bearing spinel lherzolite source.Gabbros of the Hidaka metamorphic belt are a possible source for isotopically depleted rhyolites, as both the rhyolites and gabbros have similar SrI and NdI. I-type tonalite and some gabbros in the Hidaka metamorphic belt are possible source rocks for isotopically undepleted rhyolites based on similarity in SrI and NdI. These hypotheses are supported by partial melt modeling of olivine gabbro and I-type tonalite respectively.A possible tectono-magmatic model for the production of post-Middle Miocene rhyolites from NE Hokkaido involves upwelling of the asthenosphere during the Middle Miocene, associated with the spreading of the Kurile back-arc basin and Japan Sea back-arc basin. This would have resulted in thinning of the overlying lithosphere beneath north Hokkaido, and the production of asthenosphere-derived basaltic rocks with low SrI and high NdI throughout north Hokkaido since the Middle Miocene, but less common production of lithosphere-derived basaltic rocks and HMA (with high SrI and low NdI). Basaltic magmas formed since the Middle Miocene either erupted, or caused melting of the crust, resulting in the generation of rhyolitic magma.

K-Ar ages of the Oshidomari lava from the Rishiri Volcano, off northern Hokkaido, Japan: Insight into the incipient stage of volcanic activity

Two K-Ar ages (0.30±0.19 Ma and 0.39±0.17 Ma) were obtained from the Oshidomari lava from the Rishiri Volcano, off north Hokkaido, Japan. The age data indicate the lava was erupted in the Middle Pleistocene. We newly propose an incipient stage of volcanic activity followed by the initial stage.

2003～2005年の北海道道央・道北地域におけるタマネギ乾腐病発生実態

2003～2005年の北海道道央・道北地域におけるタマネギ乾腐病発生実態

北部北海道，中期～後期中新世フェルシック火山岩におけるSr-Nd同位体比組成の多様性

北部北海道，中期～後期中新世フェルシック火山岩におけるSr-Nd同位体比組成の多様性

K-Ar age and paleomagnetic direction of a lava flow in the Minatomachi Formation, Rishiri Island, off north Hokkaido, Japan

K-Ar age and paleomagnetic direction of a lava flow in the Minatomachi Formation, Rishiri Island, off north Hokkaido, Japan

K-Ar ages of Middle and Late Pleistocene lavas from the Rishiri Volcano, off northern Hokkaido, Japan

K-Ar ages of 0.07±0.02Ma, 0.09±0.02Ma, 0.50±0.31Ma, and 0.09±0.04Ma were newly obtained for the Ponmoshirito lava dome, Oshidomari pon’yama lava dome, Oshidomari lava and Minamihama lava respectively, from the Rishiri Volcano off north Hokkaido, Japan. Data for three of the lavas (not the Oshidomari lava) confirm an eruptive history in which the initial stage of volcanic activity lasted from 130 to 70ka.

Historical Evaluation of the Yamada-Type Wind Turbine

The Yamada-type wind turbine was the sole mass produced small scale wind turbine produced during the mid Showa period of Japan. The Yamada-type wind turbines were used all over Japan, particularly in the north Hokkaido and Tohoku area, in the era of post World War II. Although it is thought that the experience and knowledge derived from them is very useful for further development of small scale wind turbines, there are few reports on them. In this paper, the authors investigate the Yamada-type wind turbine and Mr. Yamada himself-from the aspect of history of technology.

北部北海道 海別火山、利尻火山における沈み込み物質の影響

北部北海道 海別火山、利尻火山における沈み込み物質の影響