首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 15 毫秒
1.
Introduction According to the definition of the United Nations Educational, Scientific and Cultural Organization (UNESCO), natural hazards are naturally-occurring physical phenomena caused either by rapid or slow onset events having atmospheric, geologic and hydrologic origins on solar, global, regional, national and local scales. They include earthquakes, volcanic eruptions, landslides, tsunamis, floods and drought. Natural hazards must not automatically cause disasters (UNESCO 2005). …  相似文献   

2.
Six soils located within the Polish Carpathians,developed on calcium carbonate–rich sedimentary parent materials and representing various reference groups,were investigated in order to detect the lithic discontinuity.We propose using a multidirectional approach to assess the lithic discontinuity in these soils,one that includes grain size distribution,geochemical composition,heavy mineral content and micromorphology,supported by a traditional soil survey.A further aim of this process was to identify the possible admixture of allochthonous material of aeolian origin.The studied soils presented lithic discontinuities mostly at the contact of underlying calcium carbonate–rich coarsegrained slope deposits with the overlaying colluvium layer having a lower content of rock fragments.The significant changes in grain size distribution,especially in the silt and sand content,as well as high Uniformity Values and partially,high Lithological Discontinuity Index values,confirmed the occurrence of a lithic discontinuity in all studied soils.High heterogeneity in the soil profiles was also confirmed by the distribution of the major oxides;however,their distribution did not clearly indicate the lithic discontinuity.The most visible distinctions were noted from CaO content,which resulted from the deposition of carbonate-free materials(aeolian silts)and their mixing with the calcium carbonate–rich parent material.Furthermore,the analysis of heavy mineral content confirmed the allochthonous origin of the upper(and in some cases also the middle)parts of all profiles,which was manifested by the presence of highly weathering-resistant minerals such as zircon,epidote and various types of garnets.The micromorphological features of some of the studied soils showed distinctiveness within the soil profile,manifested by changes in b-fabric pattern,the occurrence and distribution of secondary carbonate and the coarse and fine coarse and fine ratio.Based on the high content of silt within the upper and middle parts of the soils,the content of Hf and Zr,as well as the higher content of weathering-resistant minerals,admixture of aeolian silt could be considered in some of the studied soils,yet with weak character.However,the dominance of minerals typical for metamorphic and igneous rocks suggested that the supply of aeolian silt was associated with loess covers rather than local sedimentary material.  相似文献   

3.
《山地科学学报》2020,17(6):1310-1332
Seven soil profiles developed on calcium carbonate–rich slope deposits in the Polish Carpathians were studied in order to: i) determine the micromorphological features of heterogeneous soils formed in a carbonate depositional environment, and ii) track primary and secondary calcium carbonate forms and their distribution in such stratified soils.Three cases of soils with different arrangements of calcium carbonate were distinguished, controlled mostly by slope processes. For instance, the increasing content and random distribution of angular and subangular rock fragments found in the overall soil matrix and the irregular coarse: fine size limit suggested different intensities of accumulation and mixing of soil material transported along the slope. Slope processes, together with the calcium carbonate content, mineralogical characteristics and texture influenced the type and arrangement of the bfabric pattern. The calcium carbonate distribution within the soils, besides the obvious inheritance from parent material, was governed by the translocation and mixing of deposits on slopes. The climatic conditions prevailing in the area favour the development of secondary forms of calcium carbonate.However, only three of the seven studied profiles contained pedogenic forms of calcium carbonate, yet they were distributed randomly. The occurrence,distribution and preservation of secondary carbonates depended on the content of primary calcium carbonate and soil features such as texture. The transported material down the slope may indicate a very low content of primary calcium or lack thereof,hence its pedogenic forms could not be created.  相似文献   

4.
The temporal and spatial distributions of zooplankton communities in the upper, middle, and lower reaches of the Xin'anjiang Reservoir, Zhejiang, China, were investigated monthly, between 2009 and 2010. Silver carp (Hypophthalmichthys moBtrix) and bighead carp (Aristichthys nobilis) dominated the pelagic fish community of this large, deep reservoir. Cladocerans were distributed evenly throughout the reservoir. Rotifers were mainly found in the upper reaches, while copepods tended to assemble in the lower reaches. The Pearson correlation analysis and stepwise multiple regression were used to identify the major physicochemical gradients influencing community variations. Zooplankton community distributions were influenced by water temperature, dissolved oxygen, phosphorus, nitrogen, and silicon. Excess nutrients, in particular silicon, stimulated rotifer growth. Based on these findings, it is possible to use rotifer density as a bioindicator of eutrophic status in deep reservoir ecosystems.  相似文献   

5.
The soil biological activity of mountain meadows is a significant factor that determines the health and utility of these regions. The climax stage of this area is forest, but to maintain semi-natural grassland, which is characterised by high biodiversity,low-intensity land use(mowing or grazing) is necessarily required. To understand the effect of various mowing regimes on the soil biological activity and plants, the soil microbial activity(microbial biomass carbon, dehydrogenase activity and number of the cultivable fraction of soil microbial community),annelids community(density and species composition earthworms and enchytraeids) and plant species composition were investigated. The study area was located in the Pieniny National Park in the Carpathian Mountains, in a meadow belonging to the association Dactylis glomerata-Poa trivialis. The investigated variants were divided according to mowing regime:traditional scything – hand mowing(HM), mechanical mowing(MM), or the abandonment of mowing – nonmowing(NM). The microbial activities(expressed by,e.g. microbial biomass carbon and the number of phosphorus bacteria) were affected by the mowing regime. The density of earthworms was higher in the HM and MM than in the NM variants. The largest changes in plant species composition were caused by the abandonment of mowing(NM). The mean number of plant species was positively correlated with soil moisture, earthworm density, and microbial activity(expressed indirectly by dehydrogenases activity). The soil microbial community, such as vegetative bacteria forms and ammonifying bacteria,were positively associated with pH value, and the microbial and total organic carbon content. The results presented here indicate that there is no single form of optimal management for all living organisms.Decisions about mowing regimes, or abandonment of use, should be preceded by multi-aspect studies,including plants and soil biota.  相似文献   

6.
Identifying the structure of protected mountain ecosystems is an important task for understanding conservation sustainability. The study area, the F?rt?na Valley, located in the Rize City on the Eastern Blacksea Coast, is one of the biological hotspots and a National Park of Turkey. In order to identify the structure of mountain ecosystems, we generated a GIS database for the main environmental parameters of the study area, including elevation, slope and aspect layers for topographic structure, 10 year mean values of Normalized Difference Vegetation Index(NDVI), data for vegetation structure, annual mean temperature and precipitation layers for climatic structure, main soil groups for soil structure and stream flow accumulation, stream flow length and stream order layers for hydrological structure .To identify the complex relations among environmental factors in the study area a data reduction method is applied with Principal Component Analysis (PCA). PCA is performed using data of 16 layers from Geographical Information Systems (GIS). PCA analysis reduced 16 dimensions into 5 dimensions containing 75% of the variation in all data. It is also revealed that the topographic structure, mainly altitude, dominates the ecosystems of the F?rt?na Valley, but it should be considered that the interactions of environmental factors in an ecosystem dynamics are very complex. The ecosystem structure is determined by the environmental factors direct or indirect effects on energy regulation of an ecosystem. Therefore the relationship between topographic elements and other abiotic-biotic elements in the Fcrtcna Valley are important for environmental assessment and sustainability of a protected area, and these effects are explained in this study.  相似文献   

7.
Lag correlations between sea surface temperature anomalies(SSTA) in the southeastern tropical Indian Ocean(STIO) in fall and Nio 3.4 SSTA in the eastern equatorial Pacific in the following fall are subjected to decadal variation,with positive correlations during some decades and negative correlations during others. Negative correlations are smaller and of shorter duration than positive correlations. Variations in lag correlations suggest that the use of the Indian Ocean Dipole(IOD) as a predictor of the El Nio Southern Oscillation(ENSO) at a lead time of one year is not effective during some decades. In this study,lag correlations between IOD and ENSO anomalies were analyzed to investigate why the IOD-ENSO teleconnection disappears during decades with negative correlations. Anomalies induced by the IOD in the equatorial Pacific Ocean during decades with negative correlations are still present,but at a greater depth than in decades with positive correlations,resulting in a lack of response to oceanic channel dynamics in the cold tongue SSTA. Lag correlations between oceanic anomalies in the west Pacific warm pool in fall and the equatorial Pacific cold tongue with a one-year time lag are significantly positive during decades with negative correlations. These results suggest that oceanic channel dynamics are overwhelmed by oceanatmosphere coupling over the equatorial Pacific Ocean during decades with negative correlations. Therefore,the Indonesian throughflow is not effective as a link between IOD signals and the equatorial Pacific ENSO.  相似文献   

8.
Flysch-type aquifers in the Eastern Carpathians usually feed periodic and low-discharge springs. However, in some areas, such as in the upper part of the Po?onina Wetlińska Massif, perennial springs with a relatively high discharge were identified. Therefore, the aim of this study was to identify recharge and groundwater flow patterns of three high-discharge springs based on the response of spring discharge to rainfall and on the relationship between specific electrical conductivity of water and spring discharge. The relation between spring discharge and rainfall was investigated by crosscorrelation analyses. Generally, cumulative rainfall over a period from 10 days to 3 months is most strongly correlated with discharge; however, the response time of spring discharge varies throughout the year. Faster response to rainfall occurs in the spring after snowmelt, while in the summer and autumn months the response time increases. Two flow systems were identified: 1) a relatively deep, fissure-pore flow system with a long response time to precipitation and 2) a shallow, fissure-dominated system with a short response time, which is superimposed on the longer response. A small range of specific electrical conductivity combined with the varying discharge of two springs suggests that dilution of groundwater by rainwater does not play a significant role. The differences in the studied springs' response to rainfall can be attributed to the recharge area, regolith features and local bedrock structures, i.e. occurrence of joints and faults, monoclinal dip of rock layers and gravitational slope deformations including ridge-top trenches, which, thus far, have been underestimated in determining groundwater storage capacity in the flysch part of the Carpathians.  相似文献   

9.
The risk of both severe and frequent injury associated with active pursuits in mountain areas is acknowledged. This phenomenon is all the most relevant to investigate in France that there is a growing enthusiasm for outdoor sports and recreation. This paper focuses on the social-demographic and sporting profiles of accident victims. Our intent is to better understand who is specifically at risk, while practicing mountain recreation, in the French mountains. Such identification doubtlessly constitutes an important asset in order to enhance prevention. Three critical activities are notably tackled, among some others: hiking, a widespread activity that exposes many practitioners to hazardous settings; mountaineering and ski touring, supposedly entailing the most severe injuries. In order to align the information collected, then provide estimations based on the reasoned crossing of these secondary data, we consulted and summarised all the databases that we knew of on the French territory: rescue team intervention reports, aggregated statistics from the sports ministry, sporting federation accident declarations, avalanche experts statistics, mountain guides union accident/incident reports, healthcare facilities admissions, etc. Only the sources considered to be the most reliable and representative were used, owing to the number of cases processed, the exhaustive nature of data collection, or the level of information detail available. Our method also included consultation of all the parties playing an active role in prevention, training and mountain rescue, thus ensuring a participative, co-constructive approach to the study with the people that have the best knowledge of victims’ profiles. Around fifty such parties were interviewed on the methods implemented, the benefits and limits of current data, and the main expectations in terms of accidentology progress, thus further enhancing the credibility of the study proposed in this paper. Our results show that the parent population profiles (in terms of age, gender, place of residence, etc.), weighted by the level of exposure (frequency of participation, level of engagement, etc.) appears to have an impact on the accident victim profiles. There is certainly a very marked gender bias and a serious age impact to be taken into account, as well as the influence of the level of experience, which counter certain preconceived ideas and which, at the very least, go against instinct. However, aside from a probable over-exposure of experienced or expert participants, much remains to be explained concerning the accident mechanisms and circumstances involved. At this stage, we regret the analytic deficiencies induced by a lack of knowledge concerning the parent populations in many cases, which makes interpretation difficult.  相似文献   

10.
Contemporary villages of the mountain region are subject to uncontrolled structural and spatial transformations, which cause deformation of centuries-old spatial systems of high cultural and natural value. The aim of the study is to confront the opinions of the inhabitants and experts regarding the condition of the cultural landscape of the villages in south-eastern Poland. This area belongs to the Carpathian region of Central Europe. The historical and economic conditions of the studied region,...  相似文献   

11.
Boulder block ramps are river engineering structures used to stabilise river beds. Block ramps provide a semi-natural and aesthetically pleasing solution to certain river engineering problems in mountain streams. When constructing block ramps,one can use the dissipative behaviour of large macroroughness elements randomly placed on the river bed to enhance fish migration in an upstream direction thus, in this sense, meeting the requirements of the EU Water Framework Directive. Block ramps are often designed and constructed to replace damaged drop hydraulic structures in the channels of mountain streams. This paper investigates the resilience of a particular block ramp placed in the Krzczonówka stream(Polish Carpathians) in terms of the engineering design function and its durability against damaging. A hydrodynamic analysis of a block ramp is presented before and after a flood event that changed the configuration of the blocks. The seminatural unstructured hydraulic structure was built on the Krzczonowka stream to protect gas pipes which are located beneath it. As a result of several floods, the boulder block chute described in this paper was damaged, and some boulders were dislodged and transported downstream. Our post-flood investigations of bathymetry and velocity revealed that even damaged boulder blocks, removed from the chute and displaced downstream of the structure, still provide significant energy dissipation of the flowing water. The novel of our paper is for the first time showing very detailed analysis of unstructured block ramp hydrodynamics parameters done in the field.Also the novel finding of our investigations shows that before and after the flood event the unstructured block ramp structure, is still fish friendly in terms of hydrodynamics.  相似文献   

12.
The relationship between landscape patterns and soil conservation, as well as the need for nature-based soil erosion control and landscape pattern optimization, have increasingly gained attention in the scientific and political community in the past decade. With the implementation of a series of afforestation/reforestation projects in the western China, the optimization and management of forest landscape patterns will become more important for soil conservation. In this study, the Bailongjiang W...  相似文献   

13.
《山地科学学报》2020,17(10):2354-2368
Stand structure dynamics are considered as major happenings in any forest as a response to environmental changes. However, this important topic is underrepresented in the treeline studies in the Nepal Himalayas. We aimed to investigate site-as well as species-specific changes in morphometric features(basal diameter, crown cover, density, and height) along the elevational gradient across treeline ecotones in response to recent environmental changes. The stand structure characteristics of Abies spectabilis, Pinus wallichiana, and Betula utilis across the treeline ecotone of three study sites in Eastern(Barun), Central(Manang), and Western(Dhorpatan) Nepal were analyzed to elucidate structural heterogeneities. Altogether, eight transects(20 m ×(60–250 m)) across the treeline ecotone were established. Trees of all life forms, trees( 2 m), saplings(0.5–2 m), and seedlings( 0.5 m), within each transect were enumerated and sampled for the morphometric features and age. Site-specific and species-specific stand structure dynamics were found. The rate of basal area increment was higher in Barun, but the Manang treeline, despite profound regeneration in recent years, had a low annual basal area increment. Moreover, the altitudinal distribution of age and morphometry were not consistent among those ecotones. Furthermore, intra-specific competition was not significant. The site-specific stand structure dynamics explain why treelines do not respond uniformly to increasing temperature. It invokes, in further studies, the incorporation of the tree's morphometric adaptation traits, phenotypic plasticity, and interactions between species genotype and the environment.  相似文献   

14.
CTD data on standard levels coolected during July and December in 1998 and the cubic spline interpolating method were used to study the characteristics of the transition layer temperature and salinity.The thermocline undergoes remarkable seasonal variation in the South China Sea (SCS),and especially in the region of the north shelf where the thermocline disappears in december.The thermocline is stronger and thicker in July than in December,There is no obvious seasonal variation in the halocline.Due to the upper Ekman transport caused by monsoon over the SCS,the thermocline slopes upward in July and downward in december from east to west in the northern SCS.The characteristics of the thermocline and halocline are influenced by local eddies in the SCS.The Zhujiang diluted flow influences significantly the SCS shelf‘s halocline.  相似文献   

15.
Cen  Jingyi  Wang  Jianyan  Huang  Lifen  Ding  Guangmao  Qi  Yuzao  Cao  Rongbo  Cui  Lei  L&#;  Songhui 《中国海洋湖沼学报》2020,38(3):722-732
Journal of Oceanology and Limnology - On May 24–29, 2019, a bloom occurring in Pingtan coastal areas of Fujian Province caused mass mortality of cage-cultured fish (Plectorhinchus cinctus and...  相似文献   

16.
《山地科学学报》2021,18(10):2626-2634
There are numerous studies on polar amplification and its influence on mid-latitude weather and climate. However, assessments on whether polar amplification occurs in Antarctica are rarely conducted. Based on the latest atmospheric reanalysis of ERA5 produced by European Centre for Medium-Range Weather Forecasts(ECMWF), we have defined the Antarctic amplification index, and calculated the trend of annual and seasonal Surface Air Temperature(SAT) mean during 1979-2019 for Antarctic Ice Sheet(AIS) and the trend mean of different meridional sectors of Antarctic sub regions including East Antarctic Ice Sheet(EAIS), West Antarctic Ice Sheet(WAIS) and Antarctic Peninsula(AP). Antarctic amplification shows regional differences and seasonal variations. Antarctica shows a slight warming with the largest magnitude in AP. The temperature anomalies indicate the least fluctuations in austral summer, and the more fluctuations in winter and spring. In austral summer, the warming trend domains EAIS and WAIS, while the cooling trend appears over AP. The zonal mean in Southern Hemisphere maintains a warming trend in the low latitudes, and fluctuates greatly in the middle and high latitudes. The strongest Antarctic amplification phenomenon occurs in spring, with the amplification index of 1.20. For AP, the amplification occurs in austral autumn, and the amplification index is 2.16. At South Pole and the surrounding regions, SAT for land only fluctuates largely and shows different trends in different seasons. The mechanism of Antarctic amplification is unclear till now, and its research suffers from the limitation of measured data. This suggests that future research needs progress in comprehensive ground observation network, remote sensing data accumulation, and high-resolution climate modeling with better representation of both atmospheric and cryospheric processes in Antarctica.  相似文献   

17.
Journal of Oceanology and Limnology - Magnetotactic bacteria(MTB) are ubiquitous prokaryotes that orient along magnetic field lines due to magnetosomes’ biomineralization within the cell....  相似文献   

18.
Variations in leaf functional traits of Abies georgei var. smithii at 3700, 3900, 4100, 4300, and 4390 m altitude were investigated in 15 typical plots in the Southeastern Tibetan Plateau. In each plot, three seedlings were selected, of which functional leaves in current-year sunny branches were chosen for the measurement of morphological, photosynthetic, and physiological and biochemical characteristics, and their variations were analyzed. Results showed that significant variations existed among the leaf functional traits of A. georgei var. smithii along the altitudinal gradient, as well as their physiological adaption indicators. Leaf area decreased, while the mass per area and thickness of leaf increased at an altitude above 4,100 m. The maxima of pigment, total nitrogen concentration, net photosynthesis rate during light-saturated, and when water use efficiency appeared at 4100 m altitude. In addition, A. georgei var. smithii seedlings regulated the activities of superoxide dismutase and ascorbate peroxidase to resist abiotic stress under 4100 m altitude. Meanwhile, malondialdehyde concentration and the dark respiration rate rapidly increased, which indicates that A. georgei var. smithii seedlingssuffered from heavy abiotic stress from 4100 m to 4390 m altitude. Basing on variations in leaf functional traits along the altitude gradient, we inferred that 4100 m altitude was the suitable region for A. georgei var. smithii growth in the Sygera Mountain. Moreover, the harsh environment was the main limiting factor for A. georgei var. smithii population expansion to high altitude.  相似文献   

19.
Along the Czech-German border there are four national parks, two Czech and two German, arranged in cross-border ‘pairs'. This article focuses on the southern ‘pair' formed by the parks of ?umava and Bayerischer Wald(Bavarian Forest). The aim is to evaluate and compare tourism organization in their areas, taking into account selected aspects of management: the network of hiking trails with its related infrastructure, transport accessibility, a typology of tourist centers, as well as directions and destinations of tourist movements. Based on the results, it can be concluded that the availability of geographical space for tourists is much greater in the German than in the Czech national park, and the tourism infrastructure is clearly more extensive there, including the network of tourist trails. This is mainly due to the longer and fairly uninterrupted development of tourism in this area. ?umava National Park can be identified as a model in terms of how to adjust the directions of tourist movements and the layout of the tourist trail network to the needs of natural environment. On the basis of observations in both national parks, it is possible to indicate various solutions that, after appropriate adaptation, may bring benefits to other protected areas.  相似文献   

20.
Current data from three moored Acoustic Doppler Profilers (ADPs) deployed in the southern Yellow Sea at sites A (1-24.17°E, 34.82°N), B (122.82°E, 35.65°N) in summer 2001 and site C (120.85°E, 34.99°N) in summer 2003 were analyzed in this paper. Features of the tidal and residual currents were studied with rotary spectral and cross-spectral methods. Main achievements were as follows: 1) Tides dominated the currents. At sites A and B, the semidiurnal tidal current was basically homogeneous in the whole depth, taking a clockwise rotation at site A, and near-rectilinear counterclockwise rotation at site B; while the diurnal tidal current was strong and clockwise near the surface, but decreased and turned counterclockwise with depth; at site C, semidiurnal tidal current dominated and diurnal current took the second, both of which were counterclockwise and vertically homogeneous. Inertial motion contributed to the clockwise component of diurnal fluctuations; 2) The 3-5d fluctuation of residual current w  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号