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过刊目录

  • 2020年, 17卷, 第09期
    刊出日期：2024-06-19
      
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  • Directional seismic response to the complex topography: A case study of 2013 Lushan Ms 7.0 earthquake
    ZHAO Bo, WANG Yun-sheng, SU Li-jun, LUO Yong-hong, ZHANG Jing
    2020, 17(09): 2049-2067.
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    Azimuthal variations in site response can provide a good insight into the site amplification and seismic conditions of geohazard occurrences. In this study, multiple directional site response methods,including D-Arias(Directional-Arias), D-SER(Directional-Shaking energy ratio), D-HVSR(Directional-Horizontal to vertical spectral ratio) and D-SSR(Directional – Standard spectral ratio), are adopted to analyse seismic data of the 2013 Lushan Ms 7.0 earthquake captured by the self-established Lengzhuguan(LZG) station which consists of the complex topography of isolated ridge, large mountain and some typical micro-reliefs. The results show that the isolated ridge could cause stronger site responses than the large mountain, and whose pronounced response direction is roughly perpendicular to its ridgeline. With the growth of elevation, the siteresonant frequency decreases. The different microreliefs on the mountain cause different site responses,which present as protruding slope > linear slope. The site response mainly exists on the surficial layer of the mountain and shows that with the increase of the distance to mountain surface, the site response gets weaker, the site resonant frequency gets higher, and the pronounced response direction is perpendicular to its ridgeline.
  • Landslide data mosaicking based on an airborne laser point cloud and multi-beam sonar images
    JI Hao-wei, LUO Xian-qi, ZHOU Yong-jun
    2020, 17(09): 2068-2080.
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    Landslides are one of the most disastrous geological hazards in southwestern China. Once a landslide becomes unstable, it threatens the lives and safety of local residents. However, empirical studies on landslides have predominantly focused on landslides that occur on land. To this end, we aim to investigate ashore and underwater landslide data synchronously. This study proposes an optimized mosaicking method for ashore and underwater landslide data. This method fuses an airborne laser point cloud with multi-beam depth sounder images.Owing to their relatively high efficiency and large coverage area, airborne laser measurement systems are suitable for emergency investigations of landslides.Based on the airborne laser point cloud, the traversal of the point with the lowest elevation value in the point set can be used to perform rapid extraction of the crude channel boundaries. Further meticulous extraction of the channel boundaries is then implemented using the probability mean value optimization method. In addition, synthesis of the integrated ashore and underwater landslide data angle is realized using the spatial guide line between the channel boundaries and the underwater multibeam sonar images. A landslide located on the right bank of the middle reaches of the Yalong River is selected as a case study to demonstrate that the proposed method has higher precision thantraditional methods. The experimental results show that the mosaicking method in this study can meet the basic needs of landslide modeling and provide a basis for qualitative and quantitative analysis and stability prediction of landslides.
  • Alpine tundra species phenology is mostly driven by climate-related variables rather than by photoperiod
    QUAGLIA Elena, RAVETTO ENRI Simone, PEROTTI Elisa, PROBO Massimiliano, LOMBARDI Giampiero, LONATI Michele
    2020, 17(09): 2081-2096.
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    The study of plant phenology has frequently been used to link phenological events to various factors, such as temperature or photoperiod.In the high-alpine environment, proper timing of the phenological cycle has always been crucial to overcome harsh conditions and potential extreme events(i.e. spring frosts) but little is known about the response dynamics of the vegetation, which could shape the alpine landscape in a future of changing climate. Alpine tundra vegetation is composed by an array of species belonging to different phytosociological optima and with various survival strategies, and snowbed communities are a relevant expression of such an extreme-climate adapted flora.We set eight permanent plots with each one in a snowbed located on the Cimalegna plateau in Northwestern Italy and then we selected 10 most recurring species among our plots, all typical of the alpine tundra environment and classified in 3different pools: snowbed specialists, grassland species and rocky debris species. For 3 years we registered the phenophases of each species during the whole growing season using an adaptation of the BBCH scale. We later focused on the three most biologically relevant phenophases, i.e., flower buds visible, full flowering, and beginning of seed dispersion. Three important season-related variables were chosen to investigate their relationship with the phenological cycle of the studied species:(i) the Day Of Year(DOY),the progressive number of days starting from the 1 st of January, used as a proxy of photoperiod,(ii) Days From Snow Melt(DFSM), selected to include the relevance of the snow dynamics, and(iii) Growing Degree Days(GDD), computed as a thermal sum. Our analysis highlighted that phenological development correlated better with DFSM and GDD than with DOY.Indeed, models showed that DOY was always a worse predictor since it failed to overcome interannual variations, while DFSM and marginally GDD were better suited to predict the phenological development of most of the species, despite differences intemperature and snowmelt date among the three years. Even if the response pattern to the three variables was mainly consistent for all the species, the timing of their phenological response was different.Indeed, species such as Salix herbacea and Ranunculus glacialis were always earlier in the achievement of the phenophases, while Agrostis rupestris and Euphrasia minima developed later and the remaining species showed an intermediate behavior. However, we did not detect significant differences among the three functional pools of species.
  • Benefits of conservation-driven mowing for the EU policy species Gladiolus palustris Gaudin in mountain fen meadows: a case-study in the European Alps
    Marco CANELLA, Gianni POLONIATO, Cesare LASEN, Simone ORSENIGO, Graziano ROSSI, Jonas V.MüLLER, Thomas ABELI
    2020, 17(09): 2097-2107.
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    The sword lily Gladiolus palustris Gaudin is protected on European level and listed in Annexes II and IV of the EC Habitat Directive 92/43/EEC. It grows in nutrient-poor, calcareous meadows in central and eastern Europe. Tree encroachment in montane meadows of the European Alps as a result of recent land use changes and the abandonment of traditional farming practices threaten the survival of this species. Conservation-driven mowing is considered a feasible conservation measure for maintaining high species diversity in abandoned semi-natural grasslands. To assess the effects of tenyears of biennial mowing on a grassland community in the Dolomiti Bellunesi National Park, Italy(Site of Community Importance, Natura 2000 network), ten25 m2 plots were established whereby four plots were placed in the mowed area, four in the non-mowed area and two in a small non-mowed patch of grassland inside the mowed area. In each plot the following variables were recorded, total percentage of plant cover, percentage cover of woody species,percentage cover of herbaceous species, percentage cover and number of flowering ramets of G. palustris and a complete list of species and their percentage abundance. Mowed plots showed a higher species richness than non-mowed plots. The number of G.palustris flowering ramets and percentage cover increased manifold in mowed plots compared to nonmowed plots. The resumption of mowing forconservation purposes undertaken by the managing authority halted the process of tree encroachment and avoided a drastic change in plant composition.Periodic mowing(every second or third year) was demonstrated to be a cost-effective conservation measure in non-productive grasslands to keep grasses at bay in favour of forbs of high conversation value.
  • Evaluation of spatiotemporal variability of temperature and precipitation over the Karakoram Highway region during the cold season by a Regional Climate Model
    YANG Tao, LI Qian, CHEN Xi, YIN Gang, LI Lan-hai, Philippe De MAEYER
    2020, 17(09): 2108-2122.
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    Precipitation and temperature are two important factors associated to snow hazards which block the transport infrastructure and cause loss of life and properties in the cold season. The in-situ observations are limited in the alpine with complex topographic characteristics, while coarse satellite rainfall estimates, reanalysis rain datasets, and gridded in-situ rain gauge datasets obscure the understanding of the precipitation patterns in hazardprone areas. Considering the Karakoram Highway(KKH) region as a study area, a double nestedWeather Research and Forecasting(WRF) model with the high resolution of a 10-km horizontal grid was performed to investigate the spatial and temporal patterns of temperature and precipitation covering the Karakoram Highway region during the cold season. The results of WRF were compared with the in-situ observations and Multi-Source WeightedEnsemble Precipitation(MSWEP) datasets. The results demonstrated that the WRF model well reproduced the observed monthly temperature(R =0.96, mean bias =-3.92°C) and precipitation(R =0.57, mean bias = 8.69 mm). The WRF model delineated the essential features of precipitation variability and extremes, although it overestimatedthe wet day frequency and underestimated the precipitation intensity. Two rain bands were exhibited in a northwest-to-southeast direction over the study area. High wet day frequency was found in January,February, and March in the section between Hunza and Khunjerab. In addition, the areas with extreme values are mainly located in the Dasu-Islamabad section in February, March, and April. The WRF model has the potential to compensate for the spatial and temporal gaps of the observational networks and to provide more accurate predictions on the meteorological variables for avoiding common coldweather hazards in the ungauged and high altitude areas at a regional scale.
  • Soil erosion calculation in the hydro-fluctuation belt by adding water erosivity factor in the USLE model
    XIN Zhi-yuan, XIA Jian-guo
    2020, 17(09): 2123-2135.
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    Soils in the hydro-fluctuation belts of the reservoirs are most highly influenced by the special hydro-conditions and reservoir operation, leading to unique soil erosion process and largely accelerate soil erosion intensity. The present study aimed to estimate soil erosion rate in the hydro-fluctuation belt of the Pubugou Reservoir, Southwest China, based on the framework of Universal Soil Loss Equation(USLE).An attempt has been made to modify the original USLE by including the reservoir water erosivity(W), a new factor into the model. Soil erosion rate from different land use types were quantitatively estimated,using the USLE and the modified USLE respectively.Field observation showed that soil erosion rate in dry farmland, bare land and grassland was 4700, 44600 and 5050 t/km2, respectively. The erosion rate assessed by the modified USLE was closely related to that recorded from the field monitoring data. The findings of this study clearly highlight the importance of inclusion of the W factor to the original USLE model while assessing soil erosion in the reservoir hydro-fluctuation belt.
  • Distribution and morpho-anatomical characterization of 'Beket'(Coriaria japonica subsp. intermedia(Matsum) T.C. Huanh) in Cordillera Central Range, Northern Philippines
    Maricel A.GURON, Jones T.NAPALDET
    2020, 17(09): 2136-2147.
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    Coriaria, the only genus under family Coriariacea, receives a lot interest among botanist due to its controversial taxonomic treatment and unique phytochemistry that could be commercially important.The populations of Coriaria japonica subsp.intermedia in Cordillera Central Range(CCR),Philippines had never been studied in detail. With the need for more information on this controversial genus,the study deemed it necessary to present the distribution and morpho-anatomical description of C.japonica subsp. intermedia in CCR. A total of 123 populations were documented, found at an elevation range of 1334 to 2494 m asl and stretched between16°31'37.7 " to 17°5'47.8" N and 120°39'40.3 " to120°55'48" E. Mapping these populations showed a narrow linear pattern of distribution concentrated at the southern portion of CCR. The plant is a shrub with simple leaves, collateral buds, raceme inflorescence,bisexual flowers with persistent perianth forming an accessory fruit after fertilization. In terms of anatomy,much are of the usual dicot characters such as dorsiventral leaf with stomata concentrated in the lower epidermis, eustele with pith in the stem andpresence of secondary growth both on old stem and old root. Interesting findings of the study include the123 populations, the larger leaf measurements, longer petals and larger fruits than the original description given by Matsumura. Also, the paracytic type of stomata and presence of pith in the primary roots of C.japonica subsp. intermedia are interesting since these are common monocot characters while the plant is dicot. These findings are additional information that could help clear the controversies on the genus Coriaria. More importantly, our results could provide essential information for understanding the plant and for developing conservation strategies not just for this plant but also for the other related plants in the CCR biogeographical zone.
  • Seasonal variations in the influence of vegetation cover on soil water on the loess hillslope
    SHEN Ming-shuang, ZHANG Jian-jun, ZHANG Shou-hong, ZHANG Hai-bo, SUN Ruo-xiu, ZHANG Yi-zhou
    2020, 17(09): 2148-2160.
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    Soil water is the key factor that restricts the restoration of the local ecological systems in the Loess Plateau of China. Studying the effects of vegetation types on soil water and its seasonal variation helps to understand hydrological characteristics and provides insights into the sustainable restoration of vegetation. Therefore, the Caijiachuan watershed was chosen as the research object to investigate the water status of a 0-10 m soil layer under different vegetation types including Pinus tabulaeformis, Robinia pseudoacacia, Platycladus orientalis, apple orchard, natural forestland,farmland and grassland. By comparing the difference between soil water of different land use types and that of grassland during the same period, the seasonal changes of soil water status of different types were judged. The results show that(1) in the 0-10 m soil layer, the largest value of soil water content was in the0.3-0.4 m layer, and the lowest was in the 5.6-5.8 m layer. The depths at which the vegetation cover influenced the soil water were up to 10 m;(2) among summer, fall and spring, the soil water storage wasthe highest in the fall. In addition, the lowest value of relative accumulation was in the fall, which was the period in which the soil water recovered;(3) the soil water in the 0-10 m layer was in a relatively deficient state in the artificial forestlands, apple orchards and native forestlands, while the relative accumulation was in the farmland. In addition, the relative deep soil layers(8-10 m) had more serious deficits in the areas in which P. tabulaeformis, R. pseudoacacia and the apple orchard grew;(4) during the study period, the farmland in the summer had the largest relative accumulation(182.71 mm), and the land under R.pseudoacacia in the fall had the lowest relative deficit(512.20 mm). In the Loess Plateau, vegetation cover will affect the change of deep soil moisture and artificial forest will cause soil water loss in different degrees.
  • Changes in leaf vein traits among vein types of alpine grassland plants on the Tibetan Plateau
    WANG Chang-shun, LYU Wang-wang, JIANG Li-li, WANG Shi-ping, WANG Qi, MENG Fan-dong, ZHANG Li-rong
    2020, 17(09): 2161-2169.
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    Vein traits influence photosynthesis and drought resistance and are sensitive to climate change.It is unclear whether vein traits, similar to other leaf traits, have obvious regional characteristics and covariance with other leaf traits, especially in Tibetan Plateau grasslands. We collected 66 species from 37 sites in late July of 2012 and early August of 2013 to investigate leaf vein traits and their relationships with other leaf traits in comparison with the available global database data and to elucidate vein investment of plants with different vein types. The average vein length per area(VLA) of plants in the Tibetan Plateau was within the range of the global dataset, and the relationships among vein traits and other leaf traits of alpine plants were consistent with the global models.The VLAs of parallel-veined grasses and pinnateveined forbs were significantly lower and higher than the global mean value, respectively. The leaf mass perarea and total nitrogen content of parallel-veined grasses were significantly lower and higher,respectively, than the global mean values; the opposite was observed in pinnate-veined forbs. The parallel-veined grasses exhibited almost a four-fold higher vein biomass investment(i.e., vein mass per leaf mass) than pinnate-veined forbs in the same region. The average VLA and its relationships with other leaf traits of the alpine grassland plants on the Tibetan Plateau had no regional characteristics,suggesting a convergence in plant leaf functioning.Plants with different leaf types differ in their adaptation strategies to plateau environments, and this may relate to biomass investment into leaf veins.Our study fills the gap with regard to vein density in alpine grassland species and provides a new perspective for understanding plant physiology and ecology by calculating and comparing the proportion of vein investment among different vein types.
  • Age structure and static life tables of the endangered Juniperus phoenicea L. in North Sinai Mountains, Egypt:implication for conservation
    Emad A.FARAHAT
    2020, 17(09): 2170-2178.
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    Studying the population ecology of endangered plants provides important baseline information for its monitoring and conservation.Juniperus phoenicea L. is an endangered species in arid ecosystems in Africa and the Middle East. The static life tables, survival curve and age structure of J.phoenicea populations from two mountains in North Sinai, Egypt(Gabal(G.) El-Halal and G. El-Maghara)were investigated. In each mountain, fifteen plots were selected, and field measurements such as stand density, tree height, and crown diameter were conducted. Moreover, 44 trees were cored and crossdated according to standard dendrochronological procedures. The results showed that the tree ages ranged from 50 to 262 years at G. El-Halal and 96 to431 years at G. El-Maghara. Mature J. phoenicea individuals dominated the study area, with only a few individuals being younger than 100 years. Moreover,seedling recruitment was extremely limited. Since the studied J. phoenicea populations showed high mortality rates among both old and young individuals,there is an imminent need for establishing a conservation program to prevent its extinction in the future. Therefore, management and conservation efforts should be made to minimize human disturbance and protect the relic habitats of this endangered species at its southern distribution limits in Africa.
  • Indexing the engineering properties of residual soils in the southern slopes of Mashhad, NE Iran
    Saeedeh HOSSEINI, Gholam Reza LASHKARIPOUR, Naser HAFEZI MOGHADDAS, Mohammad GHAFOORI
    2020, 17(09): 2179-2202.
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    Residual soils are weathering products of rocks that are commonly found under unsaturated conditions. The properties of residual soils are a function of the degree of weathering. A series of index properties, engineering properties and geophysics survey examinations were performed on residual soils from two major geological formations in Iran. In the present research, the index properties of residual soils in the south of Mashhad city in Iran are investigated.Natural and artificial trenches were analyzed for evaluating the weathering profiles and collecting soil samples. Disturbed and undisturbed samples were obtained from each of the soil profile horizons resulting from weathering of different parent rocks.Subsequently, physical properties and mechanical properties of the soil samples were determined in accordance with ASTM standards. Also, the mineralogical composition, chemistry, and texture of the soil were evaluated in 51 profiles. The field observations showed the difference in the weathering profile of residual soils deposited on various rocks(igneous, sedimentary, and metamorphic). These profiles mainly consisted of two horizons includingresidual soil on top and saprolite at the bottom. The results of laboratory tests and geotechnical data showed that the properties of residual soil samples change by depth. Moreover, depending on the type of origin rock, the properties are different in various types of residual soils. In most of the samples, the moisture content of soil horizons was also increased by depth. Based on the unified soil classification(USCS), the soils of the upper horizons appeared to be classified as ML(Lean silt) and CL(Lean clay) while the soils of the lower horizons(saprolite zone) fall in SC(clayey sand), SM(silty sand), and SW(wellgraded sand) classes. Moreover, the results demonstrated that the particle size of the soil was increased by depth. Comparison of results of the geotechnical tests showed that properties of residual soils are changed by variations of depth, weathering level, and type of parent rock. Considering the concentration of the number of lines and the concentration of the points of intersection, the length and dimension fractal of lineaments in the southeastern part of the study area, it is evident that this zone possesses weathering severity and soil thickness. Fieldwork data from this zone have also verified the severity of weathering conditions. The analysis of lineaments trends in different parts of the study area indicated that the lineaments with the NW-SE trend have a strong effect on weathering development. The weathering depth depends on the orientation of bedding joints with respect to the slope in the study area. Slope inclination and soil thickness are controlled by weathering and erosion processes.
  • Prediction of loess soil-water characteristic curve by mercury intrusion porosimetry
    LI Hua, LI Tong-lu, LI Ping, ZHANG Ya-guo
    2020, 17(09): 2203-2213.
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    Mercury intrusion porosimetry(MIP) is a simple and fast way to obtain the pore distribution of soil and can be used to estimate the soil-water characteristic curve(SWCC). In previous studies, soil was assumed to be a perfect wettability material, and the contact angle(CA) of the soil-water interface was taken as zero in the SWCC prediction method.However, the CA has proved to be much greater than zero even for hydrophilic soils according to some soil wettability experiments, and it has a significant effect on predicting the SWCC. In this research, a method for predicting the SWCC by MIP, which takes the CA as a fitting coefficient, is proposed. The pore size distribution curves are measured by MIP, and the SWCCs of two loess soils are measured by pressure plate and filter paper tests. When the CA is taken as70° and 50° for the wetting and drying process,respectively, the SWCCs predicted by the pore size distribution curves agree well with the measured SWCCs. The predicted suction range of the proposed method is 0-105 k Pa. The consistency of the results suggests that utilizing the MIP test to predict the SWCC with a proper CA is effective for loess.
  • Estimating purple-soil moisture content using Vis-NIR spectroscopy
    GOU Yu, WEI Jie, LI Jin-lin, HAN Chen, TU Qing-yan, LIU Chun-hong
    2020, 17(09): 2214-2223.
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    Soil moisture is essential for plant growth in terrestrial ecosystems. This study investigated the visible-near infrared(Vis-NIR) spectra of three subgroups of purple soils(calcareous, neutral, and acidic) from western Chongqing, China, containing different water contents. The relationship between soil moisture and spectral reflectivity(R) was analyzed using four spectral transformations, and estimation models were established for estimating the soil moisture content(SMC) of purple soil based on stepwise multiple linear regression(SMLR) and partial least squares regression(PLSR). We found that soil spectra were similar for different moisture contents, with reflectivity decreasing with increasing moisture content and following the order neutral >calcareous > acidic purple soil(at constant moisture content). Three of the four spectral transformations can highlight spectral sensitivity to SMC and significantly improve the correlation between the reflectance spectra and SMC. SMLR and PLSRmethods provide similar prediction accuracy. The PLSR-based model using a first-order reflectivity differential(R ?) is more effective for estimating the SMC, and gave coefficient of determination(v2), root mean square errors of validation(RMSEV), and ratio of performance to inter-quartile distance(RPIQ)values of 0.946, 1.347, and 6.328, respectively, for the calcareous purple soil, and 0.944, 1.818, and 6.569,respectively, for the acidic purple soil. For neutral purple soil, the best prediction was obtained using the SMLR method with R ? transformation, yieldingv2,RMSEV and RPIQ values of 0.973, 0.888 and 8.791,respectively. In general, PLSR is more suitable than SMLR for estimating the SMC of purple soil.
  • Mechanical characteristics of soil-rock mixtures containing macropore structure based on 3D modeling technology
    LIU Yong, SUN Shao-rui, WEI Ji-hong, SONG Jing-lei, YU Yong-xiang, HE Wei, ZHANG Ji-xing
    2020, 17(09): 2224-2240.
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    Soil-rock mixtures containing macropore(SRMCM) is a kind of geological material with special mechanical properties. Located in the project area of Lenggu hydropower station on the Yalong River,Sichuan Province, China, there is an extremely unstable Mahe talus slide with a total volume of nearly160 million cubic meters, which is mainly composed of SRMCM. The study on the mechanical properties of SRMCM is of great significance for the engineering construction and safe operation. In this paper,laboratory tests and discrete element numerical tests based on three-dimensional scanning technology were conducted to study the influence of stone content,stone size, and the angle of the macropore structure on shear characteristics of SRMCM. The failure mechanism of SRMCM was discussed from a microscopic perspective. This work explains the internal mechanism of the influence of stone content,stone size, and the angle of the macropore structure on the strength of SRMCM through the microscopic level of stone rotation, force chain distribution, and crack propagation. As the macropore structure that intersects with the preset shear plane at a large angle could act as a skeleton-like support to resist the shear force, the fracture of the weak cemented surface of soil and stone in the macropore structure is an important cause of SRMCM destruction.
  • Assessing tourism sustainability in hill towns: Case study of Shimla, India
    Rukhsana N.BADAR, Sarika P.BAHADURE
    2020, 17(09): 2241-2261.
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    Hill towns form a popular niche in tourism destinations. They are renowned for their natural beauty and distinctive cultural traditions. Unplanned development can lead to a loss in opportunity to access the potential of these resources or cause their damage. Development decisions need to adopt a sustainable approach that balances tourism growth with the preservation of the natural and cultural assets. The present research details a comprehensive assessment tool to study the sustainability of tourism in hill towns with a focus on Shimla, a popular hill destination in India. The tool specifies seven dimensions of sustainable tourism; 1) Tourism Assets;2) Tourism Activity; 3) Tourism Related Linkages; 4)Tourism Related Leakages; 5) Environmental and Social Sustainability; 6) Infrastructure; and 7)Attractiveness. Primary data were collected through questionnaire surveys of local households and arriving tourists. Visual survey is conducted to map built-environment and land-use. Secondary data were gathered from government reports and scholarly articles. A framework of indicators and sub-indicators was developed to analyze the data at two levels – city and ward. While the appraisal of the city provides an overall view of the performance of the tourism industry, at the ward level a comparative analysis was carried out to reveal sector related potentials and issues. The study reveals the imbalanced tourismconcentration in the core of the city as compared to other wards and the gap between tourist potential and infrastructure development. These are addressed through planning recommendations for more balanced development with a focus on eco-tourism.The research helps develop a framework which paves way to sustainable tourism development in Indian hill towns.
  • Spatiotemporal evolution of land transportation networks and accessibility in inland mountainous areas 1917-2017: A case study of Southwest China
    HUANG Yan, ZONG Hui-ming
    2020, 17(09): 2262-2279.
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    Located in the western hinterland,Southwest China is a typical mountainous area covered by plateaus, mountains and hills. Its ruggedness hinders regional internal and external connections, and its poor transportation infrastructure has long constrained the socioeconomic development of Southwest China. Based on the GIS transportation database, this paper explored the spatiotemporal evolution and characteristics of the land transportation networks and the accessibility of Southwest China from 1917 to 2017. Regional accessibility in Southwest China has significantly improved, and transportation infrastructure has gradually integrated the transportation circles of the52 central cities. The transportation network has followed an evolutionary process from a "hub-spoke pattern" to a "network pattern", while the construction of a high-speed railway(HSR) has brought about significant spatial polarization. We argue that innovation in transportation technology is one of the most effective factors for promoting a significant change in regional accessibility. In addition, the spatial distribution and evolution of accessibility in Southwest China presents a verticalcharacteristic that distinguishes it from the plains, as the spillover effects of new transportation infrastructure on accessibility improvement are partly offset by the mountainous terrain. Additionally, in Southwest China, there is significant "path dependence" in the evolution of the transportation network, since a large portion of the population is concentrated along transportation corridors in mountainous areas.
  • Comprehensive evaluation of rural courtyard utilization efficiency: A case study in Shandong Province, Eastern China
    LIU Ya-qiu, WANG Ai-ling, HOU Jie, CHEN Xin-yu, XIA Jin-shan
    2020, 17(09): 2280-2295.
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    China is implementing the strategy of Rural Revitalization. Revitalizing idle and inefficient utilization courtyards is an important measure for rural revitalization. The evaluation of courtyard utilization efficiency is the basis of determining the idle and inefficient utilization courtyards in order to revitalizing it. This study provided a reference for the optimal use of rural courtyard utilization and revitalization through the quantitative comprehensive evaluation of courtyard utilization efficiency and the classification of courtyard utilization types. Taking Shandong Province in Eastern China as study area, we selected eight surveyed villages by stratified sampling method. According to the scale of the villages, full survey and sample survey were used, while middleaged men who familiar with the courtyards were selected as the respondents. Through a household questionnaire survey and face-to-face interviews from2017 to 2018, 578 questionnaires of rural courtyardsin eight villages were obtained. Then based on the functions of rural courtyard and land resource conditions, 16 comprehensive factors were formulated,involving land conditions, construction conditions and economic benefits, to build the comprehensive evaluation index system of rural courtyard utilization efficiency. Next the index weight was determined by analytic hierarchy process, and the linear weighted regression model was used to evaluate the utilization efficiency of rural courtyard. Finally, the K-means clustering analysis was used to classify the utilization efficiency of courtyards. The results showed that among the eight villages, the average utilization efficiency of courtyards was moderate(one village was low, five were moderate, and two were high). The proportions of both idle and inefficiently utilized courtyards were high. There were three vital factors leading to the idle and low efficiency of rural courtyards. They were declining rural industries,limited arable land per capita, and more farmer workers. In this case, the utilization efficiency of courtyards should be improved by transferring rural land, developing secondary and tertiary industries,evaluating the development potential of villages,classifying and optimizing courtyard utilization, so as to make full use of idle and inefficient courtyards,increase the income of farmers and collectives and promote the revitalization of rural areas.