检索结果-南通市图书馆

Micro-site Conditions of Epiphytic Orchids in a human impact Gradient in Kathmandu Valley, Nepal

在线全文

学校读者我要写书评

暂无评论

Journal of Mountain Science 2012年第3期9卷 331-342页

作者： Yagya Prasad ADHIKARI Anton FISCHER Hagen Siegfried FISCHER Geobotany Department of Ecology and Ecosystem Management Technische Universitt München Hans-Carl-von-Carlowitz-Platz 2 D-85354 Freising Germany

We studied distribution and site conditions of epiphytic orchids in a gradient of human interference in Kathmandu valley, central Nepal. The aim was to understand the recent distribution pattern of epiphytic orchids, with respect to (i) the micro-site conditions and (ii) the type and intensity of land use. The occurrence of epiphytic orchids was recorded for a grid with 1.5 km cell size. The cells represent different types and intensities of human impact. Site factors such as bark rugosity, bark pH, diameter at breast height (dbh; 1.3 m) of host trees, exposure to wind and sunlight intensity were recorded. With regard to the species richness and abundance of epiphytic orchids, we compared different human impact categories from very strong human impact (settlement area) to very low human impact (national park). Remote sensing was used for a supervised classification of land cover. Ficus religiosa turned out to be the most important host species for orchids in urban areas, while Schima wallichii and Alnus nepalensis significantly host orchids in the other categories. Both species richness and abundance of epiphytic orchids were significantly higher under very low human impact (forest in national park) and also some remaining patches of primary forest than the other regions. Micro-climate is crucial for orchid populations. Host bark pH, bark rugosity, sunlight intensity and host exposure were significantly different for all human impact categories in order to harbour epiphytic orchid species. Habitats with a mixture of mature trees are suitable and essential for the conservation of viable populations of epiphytic orchids in settled areas. The study reveals that to improve the population size of orchids it is essential for future urban forestry to: (i) Protect old trees as carriers of existing epiphytic orchid diversity, (ii) protect medium old trees to ensure that they may become old trees, (iii) plant new host trees for the future, (iv) plant in groups instead of sing

关键词： human impact Host tree Micro-climate Epiphytic orchids Remote sensing Conservation Nepal

Genetic diversity of Mansonia altissima A. Chev. under different regimes of human impact in the Akure Forest Reserve,Nigeria

在线全文

学校读者我要写书评

暂无评论

Forestry Studies in China 2010年第4期12卷 193-200页

作者： Akindele AKINNAGBE Oliver GAILING Reiner FINKELDEY Department of Forest Genetics and Forest Tree Breeding Georg August University

Mansonia altissima is an important West African timber tree species. For the purpose of examining the effect of human impact on its genetic diversity, genetic diversity and spatial genetic structure of the species under different regimes of human impact were investigated in the Akure Forest Reserve, Nigeria, using 504 amplified fragment length polymorphism （AFLP） markers. The results indicate a very low genetic diversity in M. altissima within the forest reserve （He = 0.045; PPL = 16.75%; Br = 1.162）. The highest genetic diversity was observed in the primary forest （H e= 0.062; PPL - 21.00%; Br = 1.204）, with the lowest genetic diversity in the isolated forest patch （He = 0.032; PPL = 9.00%; B r= 1.089）. A significant and pronounced spatial genetic structure was found in the logged forest and in the isolated forest patch. In contrast, the primary forest exhibited very weak spatial genetic structuring. As expected, no spatial genetic structure was found in the planted stands of M. altissima. From a conservation point of view, our results suggest that genetic diversity ofM. altissima is at risk in the forest reserve. The scale of human impact in the study area could pose a serious threat to the maintenance of genetic diversity of the species. These results would offer practical applications in the conservation of other tropical tree species.

关键词： AFLP Mansonia altissima human impact genetic diversity spatial genetic structure tropical rainforests

Assessment of human impacts on Vegetation in Built-up Areas in China Based on AVHRR,MODIS and DMSP_OLS Nighttime Light Data,1992–2010

在线全文

学校读者我要写书评

暂无评论

Chinese Geographical Science 2014年第2期24卷 231-244页

作者： LIU Qinping YANG Yongchun TIAN Hongzhen ZHANG Bo GU Lei College of Earth and Environmental Sciences Lanzhou University School of Management Tianjin Polytechnic University Key Laboratory of Western China's Environment Systems of the Ministry of Education Lanzhou University Department of Cultural Geography Faculty of Spatial ScienceUniversity of Groningen

Since the reform and opening-up program started in 1978,the level of urbanization has increased rapidly in *** urban expansion and restructuring have had significant impacts on the ecological environment especially within built-up *** this study,ArcGIS 10,ENVI 4.5,and Visual FoxPro 6.0 were used to analyze the human impacts on vegetation in the built-up areas of 656Chinese cities from 1992 to ***,an existing algorithm was refined to extract the boundaries of the built-up areas based on the Defense Meteorological Satellite Program Operational Linescan System(DMSP_OLS)nighttime light *** improved algorithm has the advantages of high accuracy and ***,a mathematical model(human impacts(HI))was constructed to measure the impacts of human factors on vegetation during rapid urbanization based on Advanced Very High Resolution Radiometer(AVHRR)Normalized Difference Vegetation Index(NDVI)and Moderate Resolution Imaging Spectroradiometer(MODIS)*** values greater than zero indicate relatively beneficial effects while values less than zero indicate proportionally adverse *** results were analyzed from four aspects:the size of cities(metropolises,large cities,medium-sized cities,and small cities),large regions(the eastern,central,western,and northeastern China),administrative divisions of China(provinces,autonomous regions,and municipalities)and vegetation zones(humid and semi-humid forest zone,semi-arid steppe zone,and arid desert zone).Finally,we discussed how human factors impacted on vegetation changes in the built-up *** found that urban planning policies and developmental stages impacted on vegetation changes in the built-up *** negative human impacts followed an inverted′U′shape,first rising and then falling with increase of urban ***′s national policies,social and economic development affected vegetation changes in the built-up *** findings can provide a scientific basis for municipal planning de

关键词： vegetation change human impact urbanization built-up areas nighttime light data Normalized Difference Vegetation Index(NDVI)

Landscape pattern and its effect on ecosystem functions in Seoul Metropolitan area:Urban ecology on distribution of the naturalized plant species

在线全文

学校读者我要写书评

暂无评论

Journal of Environmental Sciences 2003年第2期15卷 199-204页

作者： Sun-Kee Hong In-Ju Song Hyun-Ok Kim Eung-Kyong Lee Environmental Planning Institute Seoul National UniversitySeoul Development InstituteTechnical University BerlinEnvironmental Planning Institute Seoul National University Seoul 151-742 Korea Seoul 100-250 KoreaGermanySeoul 151-742 Korea

During land transformation process in the human history, naturalized plants were introduced to several land use patterns by the different ways of plant itself. Including some naturalized plants that had been contribute to land restoration, many naturalized plants have been invaded to original habitat or landscape for native plants. Once the plants were colonized, they extend their area and population size. Urban developed areas often give an important role of source habitat for naturalized plants and expanding their population size. In recent, this situation is appearing as one of environmental problems about the urban landscape management controlling the naturalized plants that invaded in the developed area and conserving the native vegetation. This paper is focusing on relationships between distribution of habitat of naturalized plants and landscape patch in urban area in Seoul. Gangdong-Gu, one of the administrative areas in Seoul was selected for this study. We examined the recent land use change using LANDSAT TM data and spreading of the representative naturalized plants (Robinia pseudoacacia and Eupatorium rugosum) by Seoul Biotope Mapping Project and field survey in 1999. As a result, these two species were often occurred in the same habitat and distributed in forest edge disturbed by man. Their distribution patterns were related to landscape indices (patch size and shape) in the forest edge.

关键词： biotope mapping ecosystem management human impact landscape pattern naturalized plants urban ecology

Forest fragmentation and human population varies logarithmically along elevation gradient in Hindu Kush Himalaya-utility of geospatial tools and free data set

在线全文

学校读者我要写书评

暂无评论

Journal of Mountain Science 2017年第12期14卷 2432-2447页

作者： DAS Pulakesh BEHERA Mukunda Dev MURTHY Manchiraju Sri Ramachandra Centre for Ocean River Atmosphere and Land Sciences Indian Institute of Technology Kharagpur International Centre for Integrated Mountain Development (ICIMOD)

Hindu Kush Himalaya(HKH) is the largest and the most diverse mountain region in the world that provides ecosystem services to one fifth of the total world population. The forests are fragmented to different degrees due to expansion and intensification of human land use. However, the quantitative relationship between fragmentation and demography has not been established before for HKH vis-à-vis along elevation gradient. We used the globally available tree canopy cover data derived from Landsat-TM satellite to find out the decadal forest cover change over 2000 to 2010 and their corresponding fragmentation levels. Using SRTMderived DEM, we observed high forest cover loss up to2400 m that highly corroborated with the population distribution pattern as derived from satellite observation. In general, forest cover loss was found to be higher in south-eastern part of HKH. Forest fragmentation obtained using ‘area-weighted mean radius of gyration' as indicator, was found to be very high up to 2400 m that also corroborated with high human population for the year 2000 and 2010. We observed logarithmic decrease in fragmentation change(area-weighted mean radius of gyration value),forest cover loss and population growth during 2000-2010 along the elevation gradient with very high R^2 values(i.e., 0.889, 0.895, 0.944 respectively). Our finding on the pattern of forest fragmentation and human population across the elevation gradient in HKH region will have policy level implication for different nations and would help in characterizing hotspots of change. Availability of free satellite derived data products on forest cover and DEM, griddata on demography, and utility of geospatial tools helped in quick evaluation of the forest fragmentation vis-a-vis human impact pattern along the elevation gradient in HKH.

关键词： Tree canopy cover Topography Diachronic analysis Biogeography human impact

Denaturing gradient gel electrophoresis fingerprinting of soil bacteria in the vicinity of the Chinese Great Wall Station, King George Island, Antarctica

在线全文

学校读者我要写书评

暂无评论

Journal of Environmental Sciences 2013年第8期25卷 1649-1655页

作者： Qi Pan Feng Wang Yang Zhang Minghong Cai Jianfeng He Haizhen Yang Key Laboratory of Yangtze River Water Environment Ministry of Education College of Environmental Science and Engineering Tongji University Jinan Municipal Engineering Design and Research Institute Co. Ltd. Key Laboratory for Polar Science of State Ocean Administration Polar Research Institute of China

Bacterial diversity was investigated in soil samples collected from 13 sites around the Great Wall Station, Fildes Peninsula, King George Island, Antarctica, using denaturing gradient gel electrophoresis （DGGE） of 16S rRNA genes. The classes α-, β-, and γ-Proteobacteria, as well as the phylum Actinobacteria, were found to be the dominant bacteria in the soils around the Great Wall Station. Although the selected samples were not contaminated by oil, a relationship between soil parameters, microbial biodiversity, and human impact was still seen. Sample sites in human impacted areas showed lower bacterial biodiversity （average H′= 2.65） when compared to nonimpacted sites （average H′= 3.05）. There was no statistically significant correlation between soil bacterial diversity and total organic carbon （TOC）, total nitrogen, or total phosphorus contents of the soil. Canonical correlation analysis showed that TOC content was the most important factor determining bacterial community profiles among the measured soil parameters. In conclusion, microbial biodiversity and community characteristics within relatively small scales （1.5 km） were determined as a function of local environment parameters and anthropogenic impact.

关键词： Antarctica 16S rRNA gene denaturing gradient gel electrophoresis human impact

Identifying the sources of organic matter in marine and riverine sediments of Bohai Bay and its catchment using carbon and nitrogen stable isotopes

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Oceanology and Limnology 2015年第1期33卷 204-209页

作者：张彦卢学强刘红磊刘琼琼于丹 Tianjin Academy of Environmental Sciences

Carbon and nitrogen stable isotopes are useful tracers for distinguishing marine and terrestrial plant sources of sedimentary organic matter(OM),and for identifying OM from different types of *** analyzing the carbon and nitrogen stable isotopes of marine and riverine sediments from Bohai Bay and its catchment,we were able to identify the source of OM in these *** stable carbon isotope values of Bohai Bay sediments were between-22.94‰ and-23.90‰,while those of riverine sediments were from-24.45‰ to-32.50‰.Marine algae were the main source of OM in Bohai Bay ***,lacustrine algae were the main source of riverine sediments,not terrestrial *** nitrogen isotopes in Bohai Bay sediments decreased in eastward direction,with increasing distance from the coastline,which suggested a higher degree of impact from human activities along the coast.

关键词： stable isotope source of organic matter human impact Bohai Bay

Petrography of alluvial sands as a past and present environmental indicator:Case of the Loire River(France)

在线全文

学校读者我要写书评

暂无评论

International Journal of Sediment Research 2013年第3期28卷 285-303页

作者： Jean-Jacques MACAIRE Isabelle GAY-OVEJERO Michel BACCHI Constantin COCIRTA Luc PATRYL Stéphane RODRIGUES University Franqois-Rabelais of Tours University Francois-Rabelais of Tours SARL RIVE 4. Commissariat a l'Energie Atomique-CEA DAMDIF

Four sample sets of the Upper and Middle Loire river sands were analyzed in order to study the impact of natural and anthropogenic factors on their petrographic composition in space(on an 800 km stretch) and *** was determined by modal analysis of three sand-size fractions using a polarizing optical microscope and calculated for each sample("standard sand" = Sst).The watershed is composed mainly of endogenic(Massif Central) and sedimentary(southern Parisian Basin) rocks.B-set sands collected in channels for different water flows in 1996 show that Sst compositions vary by only 5%.Present-day sands in the Upper Loire and Middle Loire have very high petrographic immaturity comparing to others worldwide fluvial sands,although bio-climatic conditions favor sand maturation by source-rock weathering in the *** shows the strong impact of the Massif Central on sediment yield due to relief rejuvenation as a consequence of the formation of the Alps during the *** sands stored during the Weichselian and the Holocene in the Middle Loire floodplain,although partly weathered since their deposition,show higher inputs from the endogenic rocks of the Massif Central than present-day *** can be explained by Weichselian periglacial conditions and the development of crop farming since the Neolithic,which favored mechanical erosion,particularly in the Massif Central which is characterized by a cold,humid climate and steep *** upstream-downstream change in the composition of presently deposited sand is low in the diked *** shows however that basalt and some heavy mineral grains are vulnerable to abrasion during transport and indicates a marked sediment yield from ancient sediment stored in the *** is in line with the high incision of the river bed over the last 150 years partly due to dam construction and aggregate mining.

关键词： Fluvial sand Sand petrography Sediment source Tectonics impact human impact Loire river

Rainfall patterns of Algerian steppes and the impacts on natural vegetation in the 20^th century

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Journal of Arid Land 2018年第4期10卷 561-573页

作者： Fahima BELALA Azziz HIRCHE Serge D MULLER Mahmoud TOURKI Mostefa SALAMANI Mohamed GRANDI TaharAIT HAMOUDA Madjid BOUGHANI Laboratory of Plant Ecology Faculty of Biological SciencesUniversity of Sciences and Technology Houari BoumedieneWilaya 16000Algeria Scientific and Technical Research Center on Arid Regions Biskra 7000Algeria Institute of Evolutionary Sciences University of Montpellier-CNRSMontpellier 34095France Department of Hydraulics University of Badji MokhtarAnnaba 23000Algeria Faculty of Nature Sciences University of Saad DahlabBlida 9000Algeria Faculty of Sciences University of Yahia FaresWilaya 26000Algeria

Since 1960, the steppe regions of North Africa have been subject to an increasing desertification, including the degradation of traditional pastures. The initially dominant species （Artemisia herba-alba, Lygeum spartum and Slipa tenacissima） declined and were progressively replaced by other species （Atractylis serratuloides and Salsola vermiculata） that are more tolerant to the new conditions. It is not clear whether these changes are due to anthropogenic reasons or climatic determinism. We have carried out a statistical analysis of the climate to detect putative rainfall changes during the 20th century in the Algerian steppes based on data from 9 meteorological stations, including 2 Saharan stations （El Oued and Touggourt）, 3 pre-Saharan stations （Biskra, Laghouat and Ain Sefra） and 4 steppe stations （Djelfa, Saida, M6ch6ria and E1-Bayadh） located in the arid high plains, which represent the bioclimate diversities of the region. Previous studies suggested that significant rainfall changes for the 20th century only had records in the south of the Oran region. Most of the studies, however, looked at restricted territories over limited periods, and did not integrate the rainiest period 2004-2014. Our work is designed to integrate all the longest time series of meteorological data available for the steppe regions of Algeria. Our results confirm the spatial rainfall distribution （significant rainfall changes only recorded in the southwestern region） evidenced by previous studies, and reveal a decreasing rainfall gradient from northeastern to southwestern Algeria. Moreover, the results reveal a trend of significant decrease of rainfall in the southern Oran region, marked by two drought periods in 1980- 1985 and 1999-2003. However, with the exception of the southwestern region, rainfall overall has not declined since the beginning of the 20th century. While less marked in other regions, the drought appear to have affected all territories of the Algerian steppe. Consequent

关键词： climate arid and semi-arid regions drought rangeland degradation human impact North Africa