检索结果-南通市图书馆

The Impact of Deforestation in Anambra State： The Ekwusigo Example

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Life Sciences 2012年第10期6卷 1150-1157页

作者： Joel Ekwutosi Umeuduji Chukwuma Onyebueke Egbuonu department of geography & Environmental Management University of Port Harcourt Port Harcourt 5323 Nigeria

It is a fact that demographic and socio-economic developments are exploitatively exerting severe pressure on forest resources in Nigeria. Not only has the economy of the people been severely affected but also the environment has witnessed accelerated soil erosion, especially in Eastern Nigeria. Accordingly, this study set out to explore the environmental and socio-economic impacts of deforestation using an empirical case. Two forested and two deforested sites in Ekwusigo L.G.A of Anambra State were closely studied with respect to deforestation indices. From the data generated, Student＇s t-test was used to attempt a statistical comparison of the forested and deforested sites. The findings indicate that forest cover depletion affected both the canopy openness and the number of non-timber forest products in the area, Finally, the paper stressed the need to maintain a sustainable plant cover while economically harnessing forest resources.

关键词： Deforestation plant cover canopy openness non-timber products economical harnessing environment.

Satellite remote sensing of grasslands:from observation to management

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Plant Ecology 2016年第6期9卷 649-671页

作者： Iftikhar Ali Fiona Cawkwell Edward Dwyer Brian Barrett Stuart Green department of geography University College CorkCorkIreland Spatial Analysis Unit TeagascDublinIreland EurOcean-European Centre for Information on Marine Science and Technology LisbonPortugal School of Geographical and Earth Sciences University of GlasgowGlasgowUK

Aims Grasslands are the world’s most extensive terrestrial ecosystem,and are a major feed source for *** increasing demand for meat and other dairy products in a sustainable manner is a big *** a field scale,Global Positioning System and ground-based sensor technologies provide promising tools for grassland and herd management with high *** the growth in availability of spaceborne remote sensing data,it is therefore important to revisit the relevant methods and applications that can exploit this *** this article,we have reviewed the(i)current status of grassland monitoring/observation methods and applications based on satellite remote sensing data,(ii)the technological and methodological developments to retrieve different grassland biophysical parameters and management characteristics(***,grazing intensity)and(iii)identified the key remaining challenges and some new upcoming trends for future *** Findings The retrieval of grassland biophysical parameters have evolved in recent years from classical regression analysis to more complex,efficient and robust modeling approaches,driven by satellite data,and are likely to continue to be the most robust method for deriving grassland information,however these require more high quality calibration and validation *** found that the hypertemporal satellite data are widely used for time series generation,and particularly to overcome cloud contamination issues,but the current low spatial resolution of these instruments precludes their use for field-scale application in many *** trend may change with the current rise in launch of satellite constellations,such as RapidEye,Sentinel-2 and even the microsatellites such as those operated by Skybox *** imagery has not been widely used for grassland applications,and a better understanding of the backscatter behaviour from different phenological stages is needed for more reliable products i

关键词： remote sensing agricultural grassland grassland biomass pasture management grazing intensity

Microstructures, Fabrics, and Seismic Properties of Mylonitic Amphibolites: Implications for Strain Localization in a Thickening Anisotropic Middle Crust of the North China Craton

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Earth Science 2024年第3期35卷 769-785页

作者： Siqi Liu Bo Zhang Jinjiang Zhang Jian Zhang Lei Guo Tao Wang Baoyou Hang Xiaorong Li Key Laboratory of Orogenic Belts and Crustal Evolution School of Earth and Space SciencesPeking UniversityBeijing 100871China department of Earth Sciences The University of Hong KongHong KongChina Institute of geology Chinese Academy of Geological SciencesBeijing 100037China

Strain localization processes in the continental crust generate faults and ductile shear zones over a broad range of scales affecting the long-term lithosphere deformation and the mechanical response of faults during the seismic *** anisotropy originated within the continental crust can be applied to deduce the kinematics and structures within orogens and is widely attributed to regionally aligned minerals,e.g.,***,naturally deformed rocks commonly show various structural layers(e.g.,strain localization layers).It is necessary to reveal how both varying amphibole contents and fabrics in the structural layers of strain localization impact seismic property and its interpretations in terms of *** present microstructures,petrofabrics,and calculate seismic properties of deformed amphibolite with the microstructures ranging from mylonite to *** transition from mylonite to ultramylonite is accompanied by a slight decrease of amphibole grain size,a disintegration of amphibole and plagioclase aggregates,and amphibole aspect ratio increase(from 1.68 to 2.23),concomitant with the precipitation of feldspar and/or quartz between amphibole *** intensities of amphibole crystallographic preferred orientations(CPOs)show a progressively increasing trend from mylonitic layers to homogeneous ultramylonitic layers,as indicated by the JAm index increasing from 1.9–4.0 for the mylonitic layers and 4.0–4.8 for the transition layer,to 5.1–6.9 for the ultramylonitic *** CPO patterns are nearly random for plagioclase and *** amphibole aggregates in the amphibolitic mylonite deform by diffusion,mechanical rotation,and weak dislocation creep,and develop CPOs *** polymineralic matrix(such as quartz and plagioclase)of the mylonite and the ultramylonite deform dominantly by dissolution-precipitation,combined with weak dislocation *** mean P and S wave velocities are estimated to be 6.3 and 3.5 km/

关键词： amphibolitic mylonite microstructures petrofabrics seismic property middle crust rheology tectonics.

Epi- and endobiont faunal communities on an Egyptian Mediterranean rocky shore: species composition and their competition for space

在线全文

学校读者我要写书评

暂无评论

Journal of Oceanology and Limnology 2021年第1期39卷 198-207页

作者： Magdy EL HEDENY Mohamed RASHWAN Sebastián RICHIANO Saleh AL FARRAJ Ghada AL BASHER department of geology Faculty of ScienceAlexandria UniversityAlexandria 21568Egypt department of Biological and Geological Sciences Faculty of EducationAlexandria UniversityAlexandria 14037Egypt Instituto Patagónico de Geología y Paleontología(CONICET-CENPAT) Puerto Madryn 9120Argentina department of Zoology College of SciencesKing Saud UniversityP.O.Box 2455Riyadh 11451Saudi Arabia

The exposed calcareous rocky area of the Abu Qir Headland,east of Alexandria,Egypt which range from coarse grains,through pebbles,cobbles,and boulders to rocky platforms,was signifi cantly colonized by sclerobionts(epibionts and endobionts).The epibiont species diversity was comparatively higher than that of *** communities included bryozoans(the anascan-grade cheilostome Bifl ustra savartii),serpulid(Hydroides elegans,Spirobranchus ***,Vermiliopsis striaticeps and Protula or Apomatus)and spirorbid(Spirorbis)wormtubes,and balanoid barnacles(Amphibalanus amphitrite,Balanus trigonus,and Perforatus perforatus).The cheilostome bryozoan colonies,which developed extensive sheets,proliferated on the study rocky shore either encrusting the bioeroded basement directly,or encrusting other epilithic taxa,particularly balanoid barnacles and serpulid *** displayed a remarkable marginal competitive interaction(overgrowth and stand-off)for space on the study rocky *** the other hand,endobionts were not well represented on the studied rocky shore *** was possible to identify three ichnotaxa:Gastrochaenolites,Maeandropolydora,and *** fi ndings documented represent a signifi cant contribution to our knowledge of sclerobionts composition,sequence of their colonization and/or bioerosion,and their mutual relationships on the intertidal rocky shore of the Abu Qir Headland.

关键词： sclerobionts encrustation bioerosion Mediterranean Egypt

Assessing the Impact of Climate Change on Maize (<i>Zea mays</i>) and Cassava (<i>Manihot esculenta</i>) Yields in Rivers State, Nigeria

在线全文

学校读者我要写书评

暂无评论

Atmospheric and Climate Sciences 2018年第2期8卷 274-285页

作者： Susan I. Ajiere Vincent E. Weli department of geography and Environmental Management University of Port-Harcourt Choba Rivers State Nigeria

Globally climate change has threatened agriculture and food security which is of great importance to the economy of a nation. In Nigeria it has become a great concern to the government and people because of the obvious changes in the climate systems, therefore, assessing the impact of climate change on crop yield in an oil producing state is of great importance especially where rain fed agriculture is the main determinant for crop yield. Expost-facto research method in the context of quasi experimental research design was adopted for the study. Data for rainfall and temperature and that for crop yields were obtained from Nigerian Meteorological Agency (NIMET) and federal ministry of Agriculture;Agricultural Development Program (ADP) respectively. Analysis of data was achieved using descriptive statistics, trend graphs and multiple linear regressions. Results showed that there had been a steady but gradual increase in the annual minimum, maximum and mean temperatures over the study period of thirty years and a decrease in rainfall. Mean temperature is increasing annually at the rate of 0.0253 per annum and rainfall is decreasing at the rate of -0.5817 mm per annum. The multiple regression model showed r2 values of 0.28 for maize and 0.29 for cassava revealing that only 28% - 29% of maize and cassava yields could be explained by rainfall and temperature in the state and the result was significant at p < 0.05 revealing that cassava and maize yields significantly depended on rainfall and temperature. This study strongly advocates for a better and practicable environmental policies and improved agricultural techniques alternative source of water which will include irrigation farming, mulching since it is evident that there is a reduction in rainfall and increase in temperature in the state while creating sustainable food security.

关键词： Climate Change Maize Cassava Food Security Rivers State Nigeria

Late Mesozoic Exhumation of the Huangling Massif:Constraints on the Evolution of the Middle Yangtze River

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Acta Geologica Sinica(English Edition) 2024年第1期98卷 250-264页

作者： SU Jianchao LIN Xu LI Chang’an Jolivet MARC WU Lin CHENG Feng DENG Bin WU Zhonghai CHEN Xiaokang HU Chengwei School of geography and Information Engineering China University of GeosciencesWuhan 430074China College of Civil Engineering and Architecture China Three Gorges UniversityYichangHubei 443002China Géosciences Rennes CNRS-UMR6118Univ RennesRennesFrance State Key Laboratory of Lithospheric Evolution Institute of Geology and GeophysicsChinese Academy of SciencesBejing 100029China Key Laboratory of Orogenic Belts and Crustal Evolution Ministry of EducationSchool of Earth and Space SciencesPeking UniversityBeijing 100871China State Key Laboratory of Oil and Gas Reservoir geology and Exploitation/Chengdu University of Technology Chengdu 100871China Institute of Geological Mechanics Chinese Academy of Geological ScienceBeijing 100081China

Plate subduction leads to complex exhumation processes on *** Huangling Massif lies at the northern margin of the South China *** the Huangling Massif was exhumed as a watershed of the middle reaches of the Paleo-Yangtze River during the Mesozoic remains under *** examined the exhumation history of the Huangling Massif based on six granite bedrock samples,using apatite fission track(AFT)and apatite and zircon(U-Th)/He(AHe and ZHe)*** samples yielded ages of 157–132 Ma(ZHe),119–106 Ma(AFT),and 114–72 Ma(AHe),*** modeling revealed that three phases of rapid cooling occurred during the Late Jurassic–Early Cretaceous,late Early Cretaceous,and Late *** exhumation processes led to the high topographic relief responsible for the emergence of the Huangling *** integrated of our new data with published sedimentological records suggests that the Huangling Massif might have been the watershed of the middle reaches of the Paleo-Yangtze River since the *** that time,the rivers flowed westward into the Sichuan Basin and eastward into the Jianghan *** subduction of the Pacific Plate beneath the Asian continent in the Mesozoic deeply influenced the geomorphic evolution of the South China Block.

关键词： apatite zircon (U-Th)/He fission track Huangling Massif Yangtze River

High-Precision Structural Map of Southeast Cameroon Using Phase Filters on Potential Gravimetric Data

在线全文

学校读者我要写书评

暂无评论

Open Journal of Earthquake Research 2022年第4期11卷 89-107页

作者： Nzeuga Alain Rodrigue Bisse Salomon Bertrant Amaya Adama Kenfack Fokem Alpha Baster Ngah Christian Gislain Leonel Ndjounguep Juscar Nanfa Tefak Fatoumata Maelle Ngoumou Paul Claude Assembe Stéphane Patrick Pokam Kengni Serge Hugues department of Petroleum Gas and Exploration School of Geology and Mining Engineering University of Ngaoundere Meiganga Cameroon department of Geological Mapping and Geomatic School of Geology and Mining Engineering University of Ngaoundere Meiganga Cameroon department of Mining geology School of Geology and Mining Engineering University of Ngaoundere Meiganga Cameroon Postgraduate School of Science Technology and Geosciences University of Yaounde I Yaounde Cameroon Institute of Mining and Geological Research Ministry of Scientific Research Yaounde Cameroon department of Geophysics School of Geology and Mining Engineering University of Ngaoundere Meiganga Cameroon department of Physics Faculty of Science University of Bamenda Bambili Cameroon

The south-east of Cameroon encompasses a wide variety of geological structures among which we can cite the Congo Craton (CC), the Sanaga Fault (SF), the Yaoundé Domain, the Panafrican belt, the Protozoic series and the Dja complex. The presence of all these structures justifies the great tectonic activity to which this area was subject from the rupture of Pangea to the creation of the different plates that exist today. In this work, we will bring out a high-resolution structural map of the study area by applying the qualitative analysis of the phase filters on 200,900 points of gravimetric data obtained from the combination of the XGM2016 and ETOPO1 models. Then, with these same data, we will bring out another structural map with the maxima method called Multi-Scale Horizontal Derivative of Vertical Derivative (MSHDVD) which will be compared to the first in order to show the limits of the MSHDVD method. To do this, we will first use the extension method to highlight the map of residual anomalies, then a combination of derivative, gradient and phase filters to highlight the geological structures responsible for fracturing in this area. Phase filters have the advantage that they make it possible to highlight all the geological edges responsible for the fracturing without taking into account the depth, while the MSHDVD method highlights the existing geological contacts (edges) at depths well defined by the examiner. The structural map obtained with the MSHDVD method shows that the major structural direction in this zone is W-E while that obtained from the interpretation of the phase filters is more precise and shows that the major structural direction in this area would be N-S and this result would be in perfect agreement with the tectonics of East Cameroon.

关键词： Gravimetry Potential Field Data Edge Detection Structural Mapping Southeast Cameroon

Investigation of Spring Waters to Assess the Geo-ecological State of Landscape and Soil

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Agricultural Science and Technology(A) 2013年第8期3卷 592-602页

作者： Gero Webel Jochen Kubiniok department of Physical geography and Environmental Research Saarland University Saarbriicken D-66041 Germany

The purpose of the investigation was to assess the opportunity to use spring waters as indicator for the load state of rural landscape ecosystems. In the periods from 2000-2003 and 2011-2012, the physical and chemical water quality of 55 freshwater springs in the German federal state of the Saarland was investigated in monthly intervals. The catchment areas of the springs represented the prevailing geological formations in the Saarland as well as the main land use types such as forest, grassland and arable land. The results show a clear correlation between the nitrate content and the share of arable land in the closer catchment area of the springs. The problem of acidification and related processes occurs mainly at the sites with acid parent rock material and accordingly substrates deficient in lime. Very low pH-values between 4 and 5 are observed and the aluminum concentration levels are consistently increased. Especially at sites with low calcium content in the geological substrate, a progressive destruction of the clay minerals can be assumed. In the extremely acidic spring waters, which showed the highest aluminum contamination during the measurement 10 years ago, the aluminum-values decreased slightly. This indicates that the clay minerals in these locations are already completely destroyed. Thus, it can be concluded that the investigation of spring waters provides information on the geo-ecological conditions in catchment areas. By means of the multi-temporal approach, changes of land use or other influences by human activities can be detected.

关键词： Spring water surface water soil land use nitrate acidification aluminum.

The uptake diversity of soil nitrogen nutrients by main plant species in Kobresia humilis alpine meadow on the Qinghai-Tibet Plateau

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Science China Earth Sciences 2012年第10期55卷 1688-1695页

作者： WANG WenYing MA YongGui XU Jin WANG HuiChun ZHU JinFu ZHOU HuaKun department of Life and geography Sciences Qinghai Normal University Xining 810008 China Northwest Institute of Plateau Biology Chinese Academy of Sciences Xining 810008 China Center for Agricultural Resources Research Institute of Genetics and Developmental Biology Chinese Academy of Sciences Shijiazhuang 050021 China

We studied the uptake of ammonium, nitrate, and a variety of amino acids by alpine plant species in the Kobresia humil alpine meadow ecosystem in situ. We examined the extent of niche separation in uptake of N source by different plant species in alpine communities, and investigated the contribution of symbiotically fixed N to the total N in alpine meadow. The results are （1） δ15N natural abundance values of 13 plant species lie between -2.680‰ and 5.169‰, and the scope is 7.849‰. （2） Le- guminous plants, such as Trigonella ruthenica, Gueldenstaedtia diversiffolia, and Oxytyopis ochrocephala, and non-legumi- nous plant Gentiana straminea uptake low amounts of 15N labeled ammonium, nitrate, glycine or aspartate in soil. （3） As far as the plant uptake of organic N is concerned, Kobresia humilis, Poa pratensis, and Gentiuna spathutifolta can effectively uptake organic nitrogen, and about 37%-40% of the nitrogen of these species comes from soil organic nitrogen sources （such as glycine and aspartate）. Stipa aliena can effectively uptake nitrate, and 60% of its nitrogen comes from soil nitrate. Potentilla anserina, Poa pratensis, and Thalictrum alpinum can effectively absorb ammonium in comparason to other plant species in the meadow, and about 25%-27% of the nitrogen in these plants comes from soil ammonium. （4） The contribution of leguminous fixed N to total N is 7.48%-9.26% in Kobresia humilis alpine meadow. （5） These data show many plant species of alpine meadow may effectively utilize dissolved organic nitrogen such as amino acids, and these plants have diverse ways to uptake soil nitrogen in alpine meadows. Based on the results we can partly explain why there are abundant biodiversities and how plants at alpine habitat utilize the limited soil N sources.

关键词： Kobresia humilis alpine meadow 15N tracer technique plant organic nutrition soil nitrogen