检索结果-南通市图书馆

Detecting forest landscape boundary between mountain Birch and evergreen coniferous forest in the northern slope of Changbai mountain

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 182-186页

作者： CHANG Yu+1, BU Ren-cang+1, HU Yuan-man+1, XU Chong- gang+1, WANG Qing-li+2 (1. Institute of Applied Ecology, chinese academy of sciences, Shenyang 110016, china. 2. Shenyang Branch, CAS) Institute of Applied Ecology Chinese Academy of Sciences Shenyang 110016 China Shenyang Branch CAS Shenyang China

Boundaries between different forest types in Changbai mountain Eastern china are results from complex interactions between forest ecosystems, topography, and geomorphology. Detecting and quantifying the transitional zones are highly important since high environmental heterogeneity and biodiversity are often found within these zones. In this study, we used GIS and multivariate statistics techniques(PCA and MSWA) to analyze data from Landsat TM satellite imageries and quantitatively determined the positions and widths of the landscape boundary between mountain birch and evergreen coniferous forests in the northern slope of Changbai mountain. The results showed that the widths of the landscape boundary ranges from 30—50m while using the MSWA or/and PC method. Such detected widths are consistent with field transect data that suggests a 50m transitional zone width. The results further suggest that TM data can be used in combination with GIS and statistical techniques in determining forest landscape boundaries; MSWA is more reliable than PCA, while PCA can also be used to determine the landscape boundary when transects are properly located.

关键词： Changbai mountain forest landscape boundary PCA & MSWA

MICROWAVE OBSERVATION HIGHLIGHTS OF AR5629

在线全文

学校读者我要写书评

暂无评论

天文研究与技术 1990年第4期 189-192页

作者： Zhou Aihua Xu FuyingPurple mountain observatory, chinese academy of sciences nanjing, 2.0008, china

Active Region 5629 was extraordinary for both its flare production rate in asunsport region with moderate area and for the largest X—ray flare,ever observed by theGOES spacecraft,an estimated X20 at 0118UT on 16 ***,... 详细信息

关键词： hemisphere moderate extraordinary spacecraft burst Polarization Solar everyday exceed rarely

Impacts of permafrost changes on alpine ecosystem in Qinghai-Tibet Plateau

在线全文

学校读者我要写书评

暂无评论

Science china Earth sciences 2006年第11期49卷 1156-1169页

作者： WANG Genxu1,3 , LI Yuanshou2 , WU Qingbai2 & WANG Yibo3 1. Institute of mountain Hazards and Environment, chinese academy of sciences, Chengdu 610041, china 2. Cold and Arid Regions Environmental and Engineering Research Institute, chinese academy of sciences, Lanzhou 730000, china 3. Resource and Environment School, Lanzhou University, Lanzhou 730000, china Institute of mountain Hazards and Environment Chinese Academy of Sciences Chengdu China Resource and Environment School Lanzhou University Lanzhou China Cold and Arid Regions Environmental and Engineering Research Institute Chinese Academy of Sciences Lanzhou China

Alpine cold ecosystem with permafrost environment is quite sensitive to climatic changes and the changes in permafrost can significantly affect the alpine ecosystem. The vegetation coverage, grassland biomass and soil nutrient and texture are selected to indicate the regime of alpine cold ecosystems in the Qinghai-Tibet Plateau. The interactions between alpine ecosystem and permafrost were investigated with the depth of active layer, permafrost thickness and mean annual ground temperature (MAGTs). Based on the statistics model of GPTR for MAGTs and annual air temperatures, an analysis method was developed to analyze the impacts of permafrost changes on the alpine ecosystems. Under the climate change and human engineering activities, the permafrost change and its impacts on alpine ecosystems in the permafrost region between the Kunlun mountains and the Tanggula Range of Qinghai-Tibet Plateau are studied in this paper. The results showed that the per- mafrost changes have a different influence on different alpine ecosystems. With the increase in the thickness of active layer, the vegetation cover and biomass of the alpine cold meadow exhibit a significant conic reduction, the soil organic matter content of the alpine cold meadow ecosystem shows an exponential decrease, and the surface soil materials become coarse and gravelly. The alpine cold steppe ecosystem, however, seems to have a relatively weak relation to the permafrost environment. Those relationships resulted in the fact that the distribution area of alpine cold meadow decreased by 7.98% and alpine cold swamp decreased by 28.11% under the permafrost environment degradation during recent 15 years. In the future 50 years the alpine cold meadow ecosystems in different geomorphologic units may have different responses to the changes of the permafrost under different climate warming conditions, among them the alpine cold meadow and swamp ecosystem located in the low mountain and plateau area will have a relatively

关键词： permafrost environment, alpine cold ecosystem, statistics relationship, climate change, impacts, Qinghai-Tibet Plateau.

A study on water film in saturated sand

在线全文

学校读者我要写书评

暂无评论

International Journal of Sediment Research 2010年第3期25卷 221-232页

作者： LU X. B.1 and CUI P.2 1 Dr., Laboratory for Hydraulic and Ocean Engineering, Institute of Mechanics, chinese academy of sciences, Beijing 100190, china, 2 Prof., Key Laboratory for mountain Hazard and Earth Surface Process, Institute of mountain Hazard and Environment, chinese academy of sciences, Chengdu 610041, china, Dr. Laboratory for Hydraulic and Ocean Engineering Institute of Mechanics Chinese Academy of Sciences Beijing 100190 China Prof. Key Laboratory for Mountain Hazard and Earth Surface Process Institute of Mountain Hazard and Environment Chinese Academy of Sciences Chengdu 610041 China

Water film can serve as a sliding surface and cause landslides on gentle slopes. The development of "water film" in saturated sand is analyzed numerically and theoretically based on a quasi-three-phase model. It is shown that stable water films initiate and grow if the choking state (where the fluid velocity decreases to near zero) remains steady in a liquefied sand column. Discontinuity can occur in pore water velocity, grain velocity and pore pressure after the initiation of a water film. However, the discontinuity and water film can disappear once the choking state is changed. The key to the formation of water film is the choking in the sand column caused by eroded fine grains.

关键词： Saturated sand Water film Liquefaction

Forecast Method of Multimode System for Debris Flow Risk Assessment in Qingping Town,Sichuan Province,china

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 mountain Science 2011年第4期8卷 592-602页

作者： KONG Jiming Key Laboratory of mountain Hazards and Earth Surface Processes Chinese Academy of Sciences Institute of mountain Hazards and Environment Chinese Academy of Sciences

The Wenchuan Earthquake of May 12,2008 triggered large numbers of *** heavy rain on 13 August 2010 triggered debris flows with total volume of more than 6 million cubic meters and the debris flows destroyed 500 houses and infrastructure built after the Wenchuan *** study area Qingping Town was located in the northwestern part of the Sichuan Basin of china,which needs the second reconstructions and the critical evaluation of debris *** study takes basin as the study unit and defines collapse,landslide and debris flow hazard as a geo-hazard system.A multimode system composed of principal series system and secondary parallel system were established to evaluate the hazard grade of debris flow in 138 drainage basins of Qingping *** evaluation result shows that 30.43% of study basins(42 basins) and 24.58% of study area,are in extremely high or high hazard grades,and both percentage of basin quantity and percentage of area in different hazard grades decrease with the increase of hazard *** to the geo-hazard data from the interpretation of unmanned plane image with a 0.5-m resolution and field investigation after the Wenchuan Earthquake and 8.13 Big Debris Flow,the ratio of landslides and collapses increased after the Wenchuan Earthquake and the ratios of extremely high or high hazard grades were more than moderate or low hazard grades obviously.23 geo-hazards after8.13 Big Debris Flow in Qingping town region all occurred in basins with extremely high or high hazard grades,and 9 debris flows were in basins with extremely high hazard *** model of multimode system for critical evaluation could forecast not only the collapse and landslide but also the debris flow precisely when the basin was taken as the study unit.

关键词： Multimode System Risk assessment Debris flow Landslide Wenchuan Earthquake Qingping Town

Impact of land-use change on hydrological processes in the Maying River basin, china

在线全文

学校读者我要写书评

暂无评论

Science china Earth sciences 2006年第10期49卷 1098-1110页

作者： WANG Genxu1,3, ZHANG Yu2, LIU Guimin2 & CHEN Lin3 1. Institute of mountain Hazards and Environment, chinese academy of sciences, Chengdu 610041, china 2. Cold and Arid Regions Environmental and Engineering Research Institute, chinese academy of sciences, Lanzhou 730000, china 3. Resource and Environment School, Lanzhou University, Lanzhou 730000, china Institute of mountain Hazards and Environment Chinese Academy of Sciences Chengdu China Resource and Environment School Lanzhou University Lanzhou China Cold and Arid Regions Environmental and Engineering Research Institute Chinese Academy of Sciences Lanzhou China

Since the 1960s, dramatic changes have taken place in land-use patterns characterized by the persistent expansion of cultivated land and a continuous decrease in natural woodland and grassland in the arid inland river basins of china. It is very important to assess the effects of such land-use changes on the hydrological processes so vital for water resource management and sustainable development on the catchment scale. The Maying River catchment, a typical arid inland watershed located in the middle of the Hexi Corridor in northwest china, was the site chosen to investigate the hydrological responses to land-use changes. The annual runoff, base flow, maximum peak flow, and typical seasonal runoff in both spring and autumn flood periods were selected as the variables in the hydrological processes. Statistical-trend analysis and curvilinear regression were utilized to detect the trends in hydrological variables while eliminating the climatic influence. The relationship between cultivated land-use and hydrological variables was analyzed based on four periods of land-use variation data collected since 1965. A runoff model was established composed of two factors, i.e., cultivated land use and precipitation. The impact of land use changes, especially in the large ar- eas of upstream woodland and grassland turned into cultivated lands since 1967, has resulted in a mean annual runoff decrease of 28.12%, a base flow decline of 35.32%, a drop in the maximum peak discharge of 35.77%, and mean discharge decreases in spring and autumn of 36.05% and 24.87% respectively, of which the contribution of cultivated land expansion to the influence of annual runoff amounts to 77%-80%, with the contribution to the influence of spring discharge being 73%-81%, and that to the influence of base flow reaching 62%-65%. Thus, a rational regulation policy of land use patterns is vitally important to the sustainable use of water resources and the proper development of the entire catchment.

关键词： land-use change, arid inland river catchment, hydrological process, impact, Maying River.

Ecological Footprint and Ecological Security Evaluation in the Upper Min River Basin

在线全文

学校读者我要写书评

暂无评论

Wuhan University Journal of Natural sciences 2005年第4期10卷 641-646页

作者： TU Jian-jun 1, 2 1. School of Resources and Environment Science, Southwest china Normal University, Chongqing 400715, china 2. Institute of mountain Hazards and Environment, chinese academy of sciences, Chengdu 610041, Sichuan, china School of Resources and Environment Science Southwest China Normal University Chongqing China Institute of mountain Hazards and Environment Chinese Academy of Sciences Chengdu Sichuan China

On the basis of the ecological footprint (EF) model, this paper studied theecological security in the Upper Min River Basin ecosystem. The result shows that with 2. 038 2 hm^2per capita ecological capacity (0. 422 2 hm^2 higher than per capita EF) ,and 165 825 hm^2 ecologysurplus , the ecosystem in Upper Min River is generally secure at present. But the arable land isoverweighed and omens an eco-security crisis. Meanwhile, problems such as low forest coverage rate,severe loss of water and soil,enlargement of arid-valley area, frequent occurrence of mountainhazards and degradation of pastures have been major threats to the eco-security of this region. Thecalculation result of ten-thousand-yuan ( RMB) GDP shows that the use of natural resources isextensive, and there will be a rapid increase tendency of EF in the future. In order to maintain thepresent eco-security, the ways of use natural resources must be improved in the Upper Min RiverBasin.

关键词： ecological security ecological footprint ecological capacity quantitativeevaluation the Upper Min River Basin

Impact of the Wenchuan Earthquake on Tourism in Sichuan,china

在线全文

学校读者我要写书评

暂无评论

Journal of mountain Science 2008年第3期5卷 194-208页

作者： YANG Weiqiong CHEN Guojie WANG Daojie Institute of mountain Hazard and Environment Chinese Academy of Sciences Chengdu 610041 China Graduate University of chinese academy of sciences Beijing 100049 China

An intensive earthquake, the Wenchuan Earthquake of 8.0 on the Richter scale, struck western Sichuan, china on May 12, 2008. The earthquake has tremendously affected all industries in the quake-hit areas, with no exception of the local tourism. The study of the effect of the earthquake on tourism enriches the theory of tourism, and more importantly, it well serves as the foundation for policy making. The objective of this study is to outline for readers the empirical findings on the various ways that the earthquake affected the operations and viability of tourism in the quake-hit areas. This paper is mainly divided into 3 parts. The first part is to discuss the importance of tourism in the quake-hit areas. The second is to analyze the influencing factors of tourism. The third is to assess the impact of the earthquake on tourism in Sichuan in different seasons.

关键词： Wenchuan Earthquake Tourism Impact factors of Tourism Economic Loss

On the Lower Energy Cutoff of Nonthermal Electrons in Solar Flares

在线全文

学校读者我要写书评

暂无评论

chinese Journal of Astronomy and Astrophysics 2001年第5期1卷 453-459页

作者： Wei－QunGan You－PingLi 等 Purplemountainobservatory ChineseAcademyofSciencesNanjing210008 NationalAstronomicalObservatories Ch

A quantitative method to determine the lower energy cutoff (Ec) of power-law electron beams is established. We apply this method to the 54 hard X-ray events observed with BATSE/Compton Gamma Ray observatory (CGRO). The results show that about 75% of the observed broken double power-law spectra of hard X-rays can be explained by a lower energy cutoff in the power-law electron beams. The values of Ec, varying among the flares, are all greater than the usually accepted 20 keV! On average, E~ is about 69 keV. So high a lower energy cutoff of nonthermal electrons implies that nonthermal electrons might not be as important in powering solar flares as was previously thought. Further significance of this finding is discussed.

关键词： Sun: hard X-rays - Sun: gamma-rays - Sun: flares - Sun: particles TheSun