GIS-based weights-of-evidence modelling of rainfall-induced landslides in small catchments for landslide susceptibility mapping   总被引：10，自引：0，他引：10  

Ranjan Kumar Dahal  Shuichi Hasegawa  Atsuko Nonomura  Minoru Yamanaka  Takuro Masuda  Katsuhiro Nishino 《Environmental Geology》2008,54(2):311-324

Landslide susceptibility mapping is a vital tool for disaster management and planning development activities in mountainous terrains of tropical and subtropical environments. In this paper, the weights-of-evidence modelling was applied, within a geographical information system (GIS), to derive landslide susceptibility map of two small catchments of Shikoku, Japan. The objective of this paper is to evaluate the importance of weights-of-evidence modelling in the generation of landslide susceptibility maps in relatively small catchments having an area less than 4 sq km. For the study area in Moriyuki and Monnyu catchments, northeast Shikoku Island in west Japan, a data set was generated at scale 1:5,000. Relevant thematic maps representing various factors (e.g. slope, aspect, relief, flow accumulation, soil depth, soil type, land use and distance to road) that are related to landslide activity were generated using field data and GIS techniques. Both catchments have homogeneous geology and only consist of Cretaceous granitic rock. Thus, bedrock geology was not considered in data layering during GIS analysis. Success rates were also estimated to evaluate the accuracy of landslide susceptibility maps and the weights-of-evidence modelling was found useful in landslide susceptibility mapping of small catchments.  相似文献   

Sixteen-year phytoplankton biomass trends in the northwestern Pacific Ocean observed by the SeaWiFS and MODIS ocean color sensors     

Eko Siswanto  Makio C. Honda  Kazuhiko Matsumoto  Yoshikazu Sasai  Tetsuichi Fujiki  Kosei Sasaoka  Toshiro Saino 《Journal of Oceanography》2016,72(3):479-489

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OCTOPUS,an Octo parameter underwater sensor,for use in biological oceanography studies     

Takashi Ishimaru  Hirotaka Otobe  Toshiro Saino  Hiroshi Hasumoto  Toshisuke Nakai 《Journal of Oceanography》1984,40(3):207-212

A realtime monitoring system for observing physical, biological, and optical oceanographic parameters in shallow waters was developed. It consists of a CTD with oxygen sensor, anin situ fluorometer, anin situ transmissometer, and anin situ quanta meter together with an on-deck quanta meter. The system is also equipped with a water sampling device. Water sampling can be done during the upward cast on the basis of depth profiles of temperature, salinity, oxygen,in situ fluorescence, transmittance, and underwater irradiance taken during the downward cast.  相似文献   

Variation in mesozooplankton community structure in the Japan/East Sea (1991–1999) with possible influence of the ENSO scale climatic variability     

Sanae Chiba  Toshiro Saino   《Progress in Oceanography》2003,57(3-4):317

Seasonal and interannual change in mesozooplankton community structure in the offshore Tsushima Current area of the Japan/East Sea was studied in relation to climatic events and temporal variability of the upper water column environment from 1991 to 1999. We observed a clear seasonal succession in zooplankton community structure from a cold-water copepod-dominated community in winter and spring to a gelatinous, carnivorous and warm-water copepod-dominated community in summer and autumn. The mean abundance (inds. m⁻³) of the spring community was 3–4-fold higher than that of the other season. The spring community structure varied considerably between years: the community characterized by the summer–autumn type zooplankton assemblage appeared in 1991–1993 and 1998, while the community characterized by high abundance of cold-water copepods appeared in the mid 1990s. Time series profiles of water density and nutrients showed the thickness of the surface warm Tsushima Current and the cold subsurface water increased and decreased, respectively, limiting nutrient supply to the surface water in 1992 and 1998. These results suggest that a thick, warm surface layer might reduce the reproductive success and survival ratio of the cold-water copepods both directly and indirectly, by hindering their upward migration to the surface where food is available, and by limiting phytoplankton growth due to nutrient depletion, respectively. A Monsoon Index (MOI) showed weaker winter wind stress in 1992 and 1998, which might have attenuated formation of the cold subsurface layer in the northern Japan/East Sea and been responsible for surface warming of the study area. Since 1992 and 1998 were El Niño years, this study revealed that ENSO related climatic variability on an interannual time scale considerably influenced the lower trophic level ecosystem in the Japan/East Sea.  相似文献   

Variation of carbon and nitrogen uptake capacity in a regional upwelling area around Hachijo Island     

Jota Kanda  Toshiro Saino  Akihiko Hattori 《Journal of Oceanography》1985,41(6):373-380

Capacities for inorganic carbon, nitrate and ammonium uptake were measured around Hachijo Island, 300 km south of Tokyo, where local upwelling occurred. The phytoplankton population inside the upwelling area had a high capacity for nitrate uptake and a low capacity for uptake of ammonium. Nutrient concentration and phytoplankton biomass were higher in the upwelling plume than outside. On a chlorophylla basis, phytoplankton populations inside the upwelling area showed a lower capacity for carbon and nitrogen uptake than those outside the upwelling. Low temperature, relatively limited availability of light caused by extensive water mixing within the upwelling plume, and the difference in species composition of phytoplankton must be considered in explaining these lower uptake capacities.  相似文献   

An Ecosystem Model Including Nitrogen Isotopes: Perspectives on a Study of the Marine Nitrogen Cycle     

Chisato?YoshikawaEmail author  Yasuhiro?Yamanaka  Takeshi?Nakatsuka 《Journal of Oceanography》2005,61(5):921-942

We have developed an ecosystem model including two nitrogen isotopes (¹⁴N and ¹⁵N), and validated this model using an actual data set. A study of nitrogen isotopic ratios (δ¹⁵N) using a marine ecosystem model is thought to be most helpful in quantitatively understanding the marine nitrogen cycle. Moreover, the model study may indicate a new potential of δ¹⁵N as a tracer. This model has six compartments: phytoplankton, zooplankton, particulate organic nitrogen, dissolved organic nitrogen, nitrate and ammonium in a two-box model, and has biological processes with/without isotopic fractionation. We have applied this model to the Sea of Okhotsk and successfully reproduced the δ¹⁵N of nitrate measured in seawater and the seasonal variations in δ¹⁵N of sinking particles obtained from sediment trap experiments. Simulated δ¹⁵N of phytoplankton are determined by δ ¹⁵N of nitrate and ammonium, and the nitrogen f-ratio, defined as the ratio of nitrate assimilation by phytoplankton to total nitrogenous nutrient assimilation. Detailed considerations of biological processes in the spring and autumn blooms have demonstrated that there is a significant difference between simulated δ¹⁵N values of phytoplankton, which assimilates only nitrate, and only ammonium, respectively. We suggest that observations of δ ¹⁵N values of phytoplankton, nitrate and ammonium in the spring and autumn blooms may indicate the ratios of nutrient selectivity by phytoplankton. In winter, most of the simulated biogeochemical fluxes decrease rapidly, but nitrification flux decreases much more slowly than the other biogeochemical fluxes. Therefore, simulated δ¹⁵N values and concentrations of ammonium reflect almost only nitrification. We suggest that the nitrification rate can be parameterized with observations of δ¹⁵N of ammonium in winter and a sensitive study varying the parameter of nitrification rate.  相似文献   

Effect of seasonal change in gas transfer coefficient on air–sea CO2 flux in the western North Pacific     

Xuanrui Xiong  Yoshio Masuda  Taketo Hashioka  Tsuneo Ono  Yasuhiro Yamanaka 《Journal of Oceanography》2015,71(6):685-701

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The role of crabs (Macrophthalmus japonicus) burrows on organic carbon cycle in estuarine tidal flat,Japan     

Sosuke Otani  Yasunori Kozuki  Ryoichi Yamanaka  Hiromitsu Sasaoka  Tetsu Ishiyama  Yoshihito Okitsu  Hajime Sakai  Yoji Fujiki 《Estuarine, Coastal and Shelf Science》2010,86(3):434-440

The objective of this study is to elucidate the burrow structure and to clarify the role of burrows in material cycle in the tidal flat. In our work, we focused on the dominant species in muddy tidal flat, crab Macrophthalmus japonicus.Burrow structure of Macrophthalmus japonicus was investigated on a Katsuura river tidal flat in Tokushima prefecture, Japan, using in situ resin casting. Sampling was conducted in August 2006, and a total of 48 burrow casts were obtained. Burrows consisted mainly of J-shaped structures (98%) while the rest belonged to U-shaped structures (2%). The maximum measured burrow volume was 120 cm³ and wall surface area was 224 cm², while maximum burrow length and depth were 23.2 cm and 16.5 cm, respectively. Burrow volume and surface area were strongly correlated with carapace width of M. japonicus. Investigation of the individual number of M. japonicus in 13 quadrats (50 × 50 × 20 cm) was conducted using 2 mm sieve. The number of M. japonicus was 15–31 ind./m². Using cohort analysis we estimated that surface area of burrows was 0.07–0.15 m²/m².CO₂ emission rate was measured at the surface sediment during the period from June to December 2008. Results varied from 13.8 ± 2.2 to 49.4 ± 3.2 mg CO₂/m²/h, and organic carbon decomposition was 3.8 ± 0.6–13.5 ± 0.9 mg C/m²/h. This leads the increase of organic carbon decomposition by 1.1 times, because of the expansion of the tidal flat surface area by burrowing activity. Organic carbon decomposition in burrow walls therefore contributed to organic matter decomposition in the tidal flat. These results indicated that in situ activities of Macrophthalmus japonicus significantly influence the material cycle and it is important to consider the existence of burrow in order to understand the fluxes of materials and to evaluate the purification function of the tidal flat.  相似文献   

Spatial variation in sap flow velocity in semiarid region trees: its impact on stand‐scale transpiration estimates     

Tomonori Kume  Kyoichi Otsuki  Sheng Du  Norikazu Yamanaka  Yi‐Long Wang  Guo‐Bin Liu 《水文研究》2012,26(8):1161-1168

In this study, we aimed to clarify spatial variations in xylem sap flow, and to determine the impacts of these variations on stand‐scale transpiration (E) estimates. We examined circumferential and radial variations in sap flow velocity (F_d) measured at several directions and depths in tree trunks of black locust (Robinia pseudoacacia) and native oak (Quercus liaotungensis), both of which have ring‐porous wood anatomy, in forest stands on the Loess Plateau, China. We evaluated the impacts of circumferential variations in F_d on stand‐scale transpiration estimates using a simple scaling exercise. We found significant circumferential variations in F_d in the outermost xylem in both species (coefficients of variation = 20–45%). For both species, F_d measured at the inner xylem was smaller than that of the outermost xylem and the F_d at the depth of > 10 mm was almost zero. The simple exercises showed that omitting circumferential variations in F_d affected the E estimate by 16–21%, which was less than the effects of omitting within‐tree radial and tree‐to‐tree variations in F_d in both species. These results suggest that circumferential variations in F_d can be a minor source of error for E estimates compared with within‐tree radial and tree‐to‐tree variations in F_d, regardless of the significant circumferential variations. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Temporal changes in tree-ring nitrogen of Pinus thunbergii trees exposed to Black-tailed Gull (Larus crassirostris) breeding colonies     

Lopez C.M. Larry  Mizota Chitoshi  Yamanaka Toshiro  Nobori Yoshihiro 《Applied Geochemistry》2010

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