Estimation of the annual primary production of the lichen Cetrariella delisei in a glacier foreland in the High Arctic, Ny-Ålesund, Svalbard     

Masaki Uchida  Takayuki Nakatsubo  Hiroshi Kanda  Hiroshi Koizumi 《Polar research》2006,25(1):39-49

The fruticose lichen Cetrariella delisei is among the dominant lichen species in the deglaciated High Arctic areas of Svalbard. As part of a study of carbon cycling in the High Arctic, we aimed to estimate the primary production of lichen in a deglaciated area in Ny-Ålesund, Svalbard (79° N), by examining the effects of abiotic factors on the net photosynthesis ( Pn ) and dark respiration ( R ) rates of C. delisei . Experiments were conducted in the snow-free season of 2000 using an open-flow gas exchange system with an infrared gas analyser. Positive photosynthetic activities were observed on rainy days or soon after rainfall when the thallus water content was high, whereas photosynthetic activities dropped below the detectable limit on clear days because of the low thallus water content. Under a sufficiently high thallus water content and close to light saturation, Pn was nearly constant over a wide temperature range of 4–20 °C, while R increased with increasing temperature. We constructed a model for estimating the net primary production ( NPP ) of lichen based on the relationships between abiotic factors and the CO₂ exchange rate. The mean, minimum and maximum NPP values in the snow-free season, estimated using meteorological data obtained from 1995–2003, were 5.1, 1.0 and 8.4 g dry wt. m⁻² snow-free season⁻¹, respectively. These results suggest that NPP is highly variable and the contribution of lichen to carbon input is small compared with that of vascular plants and mosses in the study site.  相似文献   

Bedrock structure in Adapazari, Turkey—a possible cause of severe damage by the 1999 Kociaeli earthquake     

Masao Komazawa  Hitoshi Morikawa  Kajuro Nakamura  Junpei Akamatsu  Keiichi Nishimura  Sumio Sawada  Ayfer Erken  Akin Onalp 《Soil Dynamics and Earthquake Engineering》2002,22(9-12):829-836

The 1999 Kocaeli earthquake brought serious damage to downtown of Adapazari. To study why strong motions were generated at the town, a bedrock structure was investigated on the basis of Bouguer gravity anomaly, and SPAC and H/V analyses of microseisms. It was revealed that, the basin consists of three narrow depressions of bedrock with very steep edges, extending in E–W or NE–SW directions along the North Anatolia faults, and the depth to bedrock reaches 1000 m or more. Downtown of Adapazari is located 1–2 km apart from the basin-edge. It is considered that, the specific configuration of bedrock amplifies ground motions at the downtown area by focusing of seismic waves and/or interference between incident S-waves and surface-waves secondarily generated at the basin-edge. Studying 3D bedrock structure is an urgent issue for microzoning an urban area in a sedimentary basin.  相似文献   

Active arc-arc collision tectonics     

Kazuo Amano  Masaki Takahashi 《Island Arc》1997,6(2):143-143

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Metamorphism and metamorphic K–Ar ages of the Mesozoic accretionary complex in Northland, New Zealand     

Yujiro  Nishimura  Philippa M.  Black  Tetsumaru  Itaya 《Island Arc》2004,13(3):416-431

Abstract A southwest dipping Mesozoic accretionary complex, which consists of tectonically imbricated turbiditic mudstone and sandstone, hemipelagic siliceous mudstone, and bedded cherts and basaltic rocks of pelagic origin, is exposed in northern North Island, New Zealand. Interpillow limestone is sometimes contained in the basaltic rocks. The grade of subduction‐related metamorphism increases from northeast to southwest, indicating an inverted metamorphic gradient dip. Three metamorphic facies are recognized largely on the basis of mineral parageneses in sedimentary and basaltic rocks: zeolite, prehnite‐pumpellyite and pumpellyite‐actinolite. From the apparent interplanar spacing d₀₀₂ data for carbonaceous material, which range from 3.642 to 3.564 Å, the highest grade of metamorphism is considered to have attained only the lowermost grade of the pumpellyite‐actinolite facies for which the highest temperature may be approximately 300°C. Metamorphic white mica K–Ar ages are reported for magnetic separates and <2 µm hydraulic elutriation separates from 27 pelitic and semipelitic samples. The age data obtained from elutriation separates are approximately 8 m.y. younger, on average, than those from magnetic separates. The age difference is attributed to the possible admixture of nonequilibrated detrital white mica in the magnetic separates, and the age of the elutriation separates is considered to be the age of metamorphism. If the concept, based on fossil evidence, of the subdivision of the Northland accretionary complex into north and south units is accepted, then the peak age of metamorphism in the north unit is likely to be 180–130 Ma; that is, earliest Middle Jurassic to early Early Cretaceous, whereas that in the south unit is 150–130 Ma; that is, late Late Jurassic to early Early Cretaceous. The age cluster for the north unit correlates with that of the Chrystalls Beach–Taieri Mouth section (uncertain terrane), while the age cluster for the south unit is older than that of the Younger Torlesse Subterrane in the Wellington area, and may be comparable with that of the Nelson and Marlborough areas (Caples and Waipapa terranes).  相似文献   

A deep seismic transect from Hovgård Ridge to northwestern Svalbard across the continental-ocean transition: A sheared margin study     

O. Ritzmann  W. Jokat  W. Czuba  A. Guterch  R. Mjelde  Y. Nishimura 《Geophysical Journal International》2004,157(2):683-702

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Future supercontinent assembled in the northern hemisphere     

Masaki Yoshida  M. Santosh 《地学学报》2011,23(5):333-338

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Habitability analyses of aquatic bacteria     

Md. Nurul Haider  Masahiko Nishimura  Minoru Ijichi  Ching-chia Yang  Wataru Iwasaki  Kazuhiro Kogure 《Journal of Oceanography》2018,74(2):197-207

Habitability is defined as an ability of an organism to inhabit different environments. Habitability of organisms, however, cannot be inferred from analyses such as a whole genome or community structures. A recently developed database, the MetaMetaDB, gives us information from what kind of environments one particular 16S rRNA sequence data has ever been obtained, and thus enables us to infer the habitability of the bacterium in question. In order to check the applicability of this database to study the habitability of aquatic bacteria, samples collected at two Naka River stations, one estuarine station from Naka River Estuary, two coastal stations at Oarai in Ibaraki Prefecture, Japan and one station in the Kuroshio Current of the western North Pacific were examined. The phylotypes were tracked against the MetaMetaDB and it was reasonably found that the low-salinity stations were dominated by sequences with “freshwater and groundwater”, “human” and “wastewater” habitat identities, while the high-salinity stations were dominated by those with a “marine” identity. The phylotypes of low-salinity stations with a particular habitat identity were absent or rare in the high-salinity stations and vice versa. The MetaMetaDB also showed that sequences of Cyanobacteria or related phylogenetic groups may be present in the human gut, as well as the probable distribution of the relatives (ancestors/descendants/siblings) of some bacteria. These overall findings proved that the MetaMetaDB is useful as a new tool to infer microbial habitability and it gives us new information on the possible origin and ecology of microorganisms in the environments.  相似文献   

Tropical synoptic-scale wave disturbances over the western Pacific simulated by a global cloud-system resolving model     

Yoshiki Fukutomi  Chihiro Kodama  Yohei Yamada  Akira T. Noda  Masaki Satoh 《Theoretical and Applied Climatology》2016,124(3-4):737-755

Lower-tropospheric tropical synoptic-scale disturbances (TSDs) are associated with severe weather systems in the Asian Monsoon region. Therefore, exact prediction of the development and behavior of TSDs using atmospheric general circulation models is expected to improve weather forecasting for this region. Recent state-of-the art global cloud-system resolving modeling approaches using a Nonhydrostatic Icosahedral Atmospheric Model (NICAM) may improve representation of TSDs. This study evaluates TSDs over the western Pacific in output from an Atmospheric Model Intercomparison Project (AMIP)-like control experiment using NICAM. Data analysis compared the simulated and observed fields. NICAM successfully simulates the average activity, three-dimensional structures, and characteristics of the TSDs during the Northern summer. The variance statistics and spectral analysis showed that the average activity of the simulated TSDs over the western Pacific during Northern summer broadly captures that of observations. The composite analysis revealed that the structures of the simulated TSDs resemble the observed TSDs to a large degree. The simulated TSDs exhibited a typical southeast- to northwest-oriented wave-train pattern that propagates northwestward from near the equator around 150 ^° E toward the southern coast of China. However, the location of the simulated wave train and wave activity center was displaced northward by approximately a few degrees of latitude from that in the observation. This displacement can be attributed to the structure and strength of the background basic flow in the simulated fields. Better representation of the background basic states is required for more successful simulation of TSDs.  相似文献   

Predominance of parallel‐ and cross‐predation in anglerfish          下载免费PDF全文

Masaki Yasugi  Michio Hori 《Marine Ecology》2016,37(3):576-587

Several studies in the last 20 years have revealed that morphological asymmetry in fish can be characterized as ‘antisymmetry’. Antisymmetry is a lateral dimorphism in which each population consists of individuals with well‐developed left sides (lefties) and well‐developed right sides (righties). This dimorphism influences predator–prey interactions. In some piscivorous fishes, it has been found that predators can catch more prey of the opposite morphological type to themselves (cross‐predation) than of the same morphological type (parallel‐predation). Our previous work clarified that the predominance of cross‐predation is caused by lateralized behaviors of predators and prey that correspond to their morphological antisymmetry. Moreover, based on the results of our behavioral observations, we hypothesized that parallel‐predation can predominate when predators encounter the potential prey frontally. To test this hypothesis, in the present study we investigated the relationship between lateral morphological types of anglerfish (Lophiomus setigerus) and those of the prey fishes found in their stomachs. Anglerfish attract potential prey using their first dorsal fin (illicium) as a lure, and their frontal encounters with potential prey fishes were photographed in situ and observed in an aquarium. The results of a stomach contents analysis indicated that parallel‐predation predominated in five benthopelagic prey fish species (perches and eels). By contrast, five benthic prey fishes (gobies and weevers) exhibited the predominance of cross‐predation. These results not only demonstrate the predominance of parallel‐predation in a natural fish community, but also suggest that the relationship between morphological types of predator and prey species can be reversed depending on the lifestyle of prey.  相似文献   

Diagnosis of earth-fill dams by synthesised approach of sounding and surface wave method     

Shin-ichi Nishimura  Toshifumi Shibata  Takayuki Shuku 《Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards》2016,10(4):312-319

The spatial distribution of the strength inside the earth-fill is identified by the sounding tests. In this research, the Swedish weight sounding (SWS) is employed, and the spatial high-density test is performed to identify the spatial correlation structure. Furthermore, the synthesised approach of the SWS and surface wave method, which is one of the geophysical method, is proposed to compensate the shortage of each approach. Consequently, the correlation structure of an earth-fill could be identified accurately, and the high resolution of the spatial distribution could be visualised based on the survey results.  相似文献