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401.
Praca E Laran S Lepoint G Thomé JP Quetglas A Belcari P Sartor P Dhermain F Ody D Tapie N Budzinski H Das K 《Marine pollution bulletin》2011,62(5):1058-1065
Risso’s dolphins, pilot whales and sperm whales rarely strand in the northwestern Mediterranean. Thus, their feeding ecology, through the analysis of stomach contents, is poorly known. The aim of this study was to gain further insight into the segregation/superposition of the diet and habitat of Risso’s dolphins, pilot whales and sperm whales using chemical tracers, namely, stable isotopes (δ13C, δ15N) and organochlorines. Significantly different δ15N values were obtained in Risso’s dolphins (11.7 ± 0.7‰), sperm whales (10.8 ± 0.3‰) and pilot whales (9.8 ± 0.3‰), revealing different trophic levels. These differences are presumably due to various proportions of Histioteuthidae cephalopods in each toothed whale’s diet. Similar δ13C contents between species indicated long-term habitat superposition or corroborated important seasonal migrations. Lower congener 180 concentrations (8.20 vs. 21.73 μg.g−1 lw) and higher tDDT/tPCB ratios (0.93 vs. 0.42) were observed in sperm whales compared with Risso’s dolphins and may indicate wider migrations for the former. Therefore, competition between these species seems to depend on different trophic levels and migration patterns. 相似文献
402.
People’s livelihood in several Himalayan regions largely depends on collection, use, and trade of medicinal plants. Traditional
use is generally not a problem, but commercial gathering of selected species to meet increasing national and international
demand can result in over-exploitation. Sustainable management of medicinal plants requires a clear understanding of the respective
roles, responsibilities and viewpoints of the various stakeholders involved. Through personal interviews and group discussions,
this study aimed at investigating the views of two stakeholder groups on use, trade and conservation of medicinal plants in
the Rasuwa district of Nepal. Local people and district and national organizations agreed that medicinal plants are collected
for a combination of commercial and personal uses. Perceptions on market availability differed significantly: 100 % of the
respondents from district and national organizations saw markets as easily available, against only 36 % for local people.
This could explain why medicinal plants were perceived by local people to contribute less to income generation than to livelihood
improvement. Different viewpoints were also expressed concerning the status of medicinal plants in the district: 81 % of the
respondents from district and national organizations considered that medicinal plants were threatened, compared to only 28
% for local people. Despite this disparity, both stakeholder groups agreed upon potential threats to medicinal plants: over-harvesting;
habitat loss due to land-use change and deforestation; and over-grazing by livestock. Several challenges were identified regarding
sustainable management of medicinal plants, such as ambiguous policies; lack of resources, information and infrastructures;
habitat degradation; and over-exploitation. Despite these challenges, respondents agreed that the medicinal plants sector
offers huge opportunities in the Rasuwa district, given resource availability, community awareness and motivation, and the
priority given to the sector by governments and other agencies. Proper collaboration, communication and coordination among
stakeholders are needed to grab these opportunities. 相似文献
403.
We have calculated for extragalactic Hii regions, the expected relationship between the radio flux at 11 cm and the infrared flux at 11 and 20 m based on the grain models and the parameters which fit the observations of galactic Hii regions. It is shown that the measured infrared fluxes of extragalactic Hii regions are consistent with the expected infrared fluxes for these objects. 相似文献
404.
The Kalpatta granite, of Pan-African age occurs in the southern granulite terrain of Peninsular India. Bouguer anomaly map of the Kalpatta and adjoining areas reveals a gravity low of 8–10 mGal centered over the Kalpatta granite and a minor low of 4–6 mGal over the adjacent Ambalavayal granite pluton. The residual anomaly map prepared for the Kalpatta granite has been utilized to obtain depth extent and 3-D geometry of the pluton. The analysis suggests that the Kalpatta granite is an elliptical and somewhat pear shaped body with horizontal dimensions of 6–11 km and extending to a depth of 6.5km, has steeply inward dipping contacts and the shape seen on the surface continues throughout its depth. The smooth oval shape could indicate low ductility contrast, deeper level of emplacement and permissive nature of the pluton. The 3-D depth model indicates an oblique section with much deeper levels exposed in the south, in other words, the crustal block encompassing the pluton has suffered a NNW tilt during uplift after the emplacement. It is further inferred that there was no post intrusive shape modification, the NW tilting of the region and denudation gave rise to the present outcrop pattern of the body. 相似文献
405.
406.
Morphometric analysis of Morar River Basin, Madhya Pradesh, India, using remote sensing and GIS techniques 总被引:3,自引:2,他引:1
Hydrogeological mapping and drainage analysis can form an important tool for groundwater development. Assessment of drainage and their relative parameters have been quantitatively carried out for the Morar River Basin, which has made positive scientific contribution for the local people of area for the sustainable water resource development and management. Geographical Information System has been used for the calculation and delineation of the morphometric characteristics of the basin. The dendritic type drainage network of the basin exhibits the homogeneity in texture and lack of structural control. The stream order ranges from first to sixth order. The drainage density in the area has been found to be low which indicates that the area possesses highly permeable soils and low relief. The bifurcation ratio varies from 2.00 to 5.50 and the elongation ratio (0.327) reveals that the basin belongs to the elongated shaped basin category. The results of this analysis would be useful in determining the effect of catchment characteristics such as size, shape, slope of the catchment and distribution of stream net work within the catchment. 相似文献
407.
GARY J. HAMPSON M. ROYHAN GANI HIRANYA SAHOO ANDREAS RITTERSBACHER ANDREW RANSON JOHN A. HOWELL SIMON J. BUCKLEY BRYAN BRACKEN 《Sedimentology》2012,59(7):2226-2258
Current models of alluvial to coastal plain stratigraphy are concept‐driven and focus on relative sea‐level as an allogenic control. These models are tested herein using data from a large (ca 100 km long and 300 m thick), continuous outcrop belt (Upper Cretaceous Blackhawk Formation, central Utah, USA). Many channelized fluvial sandbodies in the Blackhawk Formation have a multilateral and multistorey internal character, and they generally increase in size and abundance (from ca 10% to ca 30% of the strata) from base to top of the formation. These regional, low‐resolution trends exhibit much local variation, but are interpreted to reflect progressively decreasing tectonic subsidence in the upper Blackhawk Formation and overlying Castlegate Sandstone. The trend may also incorporate progressively more frequent channel avulsion during deposition of the lower Blackhawk Formation. Laterally extensive coal zones formed on the coastal plain during shallow‐marine transgressions, and define the high‐resolution stratigraphic framework of the lower Blackhawk Formation. Large (up to 25 m thick and 1 to 6 km wide), multistorey, multilateral, fluvial channel‐complex sandbodies that overlie composite erosion surfaces occur at distinct stratigraphic levels, and are interpreted as fluvial incised valley fills. Low amplitude (<30 m) relative sea‐level variations are interpreted as the dominant control on stratigraphic architecture in the lower Blackhawk Formation, which was deposited up to 50 km inland from the coeval shoreline. In contrast, the high‐resolution stratigraphy of the upper Blackhawk Formation is poorly defined, and channelized fluvial sandbodies are poorly organized. Vertical and laterally offset stacking of a small proportion (<10%) of sandbodies produced ‘clusters’ that are not confined by ‘master’ erosion surfaces. Avulsion is interpreted to dominate the stratigraphic architecture of the upper Blackhawk Formation. This data‐driven analysis indicates that alluvial to coastal plain stratigraphic architecture reflects a combination of various allogenic controls and autogenic behaviours. The relative sea‐level control emphasized in sequence stratigraphic models is only rarely dominant. 相似文献
408.
Spatio-temporal patterns of agricultural expansion and its effect on watershed degradation: a case from the mountains of Nepal 总被引:1,自引:1,他引:0
K. C. Krishna Bahadur 《Environmental Earth Sciences》2012,65(7):2063-2077
Expansion of agricultural at the cost of forested land is a common cause of watershed degradation in the mountain zones of
developing countries. Many studies have been conducted to demonstrate land use changes in such regions. However, current knowledge
regarding the changes, driving forces and implications of such change within the context of watershed development is limited.
This study analyses changes in spatial patterns of agricultural land use and their consequences for watershed degradation
during the 1976–2000 period along an altitude gradient in a watershed in Nepal, by means of remote sensing, GIS and the universal
soil loss equation. Estimated soil loss ranged from 589 to 620 t ha−1 y−1, while areas of extreme hazard severity (>100 t ha−1) increased from 9 to 14.5% from 1990 to 2000. Spatial distribution of soil loss in 2000 was characterized by 88% of total
soil losses being from upland agricultural areas. The study determined that without considering other forms of land degradation,
only water erosion was responsible for erosion of a substantial area in a short timeframe. Areas under upland cultivation
are in an extremely vulnerable state, with these areas potentially no longer cultivable within a period of 6 years. As sustainability
of the watershed is dependent on forests, continued depletion of forest resources will result in poor economic returns from
agriculture for local people, together with loss of ecosystem services. Thus, in order to achieve the goal of watershed development,
remaining forest lands must be kept under strict protection. 相似文献
409.
Krishnaraj Srinivasamoorthy Kannusamy Vijayaraghavan Murugesan Vasanthavigar Subramanya Sarma Sabarathinam Chidambaram Paluchamy Anandhan Rama Manivannan 《Arabian Journal of Geosciences》2012,5(1):83-94
Groundwater samples were collected from Mettur taluk of Salem district, Tamilnadu, India for two different seasons (pre-monsoon and post-monsoon) and analyzed for fluoride ion along with other chemical parameters. The major litho units of the study area are Charnockites, peninsular gneiss, and calc gneiss of meta-sedimentary group. The fluoride concentration ranges from 0.1 to 2.8?mg/L and 0.4 to 4.0?mg/L during pre-monsoon (PRM) and post-monsoon (POM) seasons, respectively. Results showed that collected water samples were contaminated by the presence of fluoride ion. During PRM and POM, 21% and 56% of samples recorded higher fluoride when compared with Indian Drinking Water Standard (1?mg/L) and (9% and 35%) of samples recorded higher fluoride when compared with World Health Organization tolerance limit (1.5?mg/L). The ratio of Na/Ca indicates high sodium content in groundwater enhances the dissolution of fluoride at higher pH. Hydrogeochemical facies indicates water-rock interaction as main source for high fluoride in groundwater. A positive correlation between pH, Mg, and F indicates high alkaline nature of water promotes fluoride leaching from source rocks into ground water. Factor analysis indicates hydro-geochemical processes like weathering, ion exchange, and anthropogenic contributes to groundwater chemistry. The saturation index indicates dissolution and precipitation contributes fluoride dissolution along with mixing. 相似文献
410.
Understanding the Unique Spectral Signature of Winter Rape 总被引:1,自引:0,他引:1
Driven by significant technological developments in the hyperspectral imaging, material mapping using reference spectra has received renewed interest of the remote sensing community. The applicability of reference spectral signatures in image classification depends mainly on the material type and its spectral signature behaviour. Identification and spectral characterization of materials which exhibit unique spectral behaviour is the first step in this approach. Consequently there have been active researches for the identification of surface materials which exhibit unique spectral signatures. The uniqueness of reflectance signature of winter rape relative to its co-occurring crop species was reported in this study. Reflectance spectral libraries constructed from field spectral reflectance measurements collected over five agricultural crops (alfalfa, winter barley, winter rape, winter rye, and winter wheat) during four subsequent growing seasons were classified by the linear discriminant analysis (LDA). Further, the reference field spectral database was used for the spectral feature fitting and classification of a historical HyMAP airborne hyperspectral imagery acquired at a separate site, by spectral library search. Results indicate the existence of a meaningful spectral matching between image and field spectra for winter rape and demonstrate the potential for transferring spectral library for hyperspectral image classification. The observed consistency in the discrimination of winter rape demonstrates experimentally the fundamental principle of remote sensing which suggests the theoretical existence of unique spectral signatures for materials which can be incorporated as reference spectral signatures for hyperspectral image classification. 相似文献