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过刊目录

  • 2024年, 21卷, 第02期
    刊出日期：2024-06-19
      
  • 全选
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  • Problem identification and revitalization strategies for the recovery and reconstruction of traditional villages in the Ms 6.8 Luding Earthquake
    HUANG Chao, QIU Jian, LIU Chun, JIANG Rui, ZHAO Chuanrong, ZHANG Yi
    2024, 21(02): 361-379.
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    Post-disaster reconstruction is a topic of global concern, and traditional villages have special heritage attributes and need to face more requirements and obstacles in post-disaster reconstruction. This paper summarizes four concepts based on the research on post-disaster reconstruction both domestically and internationally, as well as the recovery and reconstruction of cultural heritage. Through a field survey of traditional villages in the Ms 6.8 Luding earthquake-stricken area, it is found that there are problems such as insufficient awareness of heritage value, misalignment of scientific reconstruction technology, and insufficient protection of reconstruction elements during the reconstruction process. Traditional villages face the risk of declining or even loss of heritage value. In order to effectively protect traditional villages and inherit the carrier of regional culture, four targeted reconstruction response strategies are proposed, i.e., to "establish special planning for traditional village preservation", "emphasize recovery of the authenticity of village heritage", "ensure elements for village heritage recovery" and "promote the activation and utilization of village heritage", based on the problems discovered during the survey and the four concepts summarized in the research on post-disaster reconstruction of traditional villages. The research results hope to provide useful reference for ancient cultural areas affected by earthquakes on how to protect cultural heritage during the post-disaster reconstruction process.
  • Understanding livelihood vulnerability:a perspective from Western Sichuan's ethnic rural settings
    YU Yongqian, JING Zheng, WANG Yan, QIU Xiaoping, YANG Xueting, XU Yun
    2024, 21(02): 380-396.
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    To explore the livelihood status and key influencing factors of rural households in the minority areas, we collected flat data from 284 rural households in 32 villages across 12 counties of Western Sichuan from 2021 to 2022. We conducted participatory household survey on the livelihood status of the rural households and try to identify the key factors to influence their livelihood vulnerability using multiple linear regression. The results showed that: the livelihood situation of the rural households is relatively vulnerable. The vulnerability varies significantly with the income levels, education levels, and income sources. The vulnerability of farm households, categorized from low to high livelihood types, follows the sequence: non-agricultural dominant households, non-agricultural households, agricultural dominant households, and pure agricultural households. The degree of damage to the natural environment, education costs, loan opportunities, the proportion of agricultural income to annual household income, and the presence of sick people in the household have significant positive effects on the livelihood vulnerability index(LVI) of rural households; while help from relatives and friends, net income per capita, household size, household education, agricultural land area, participation in industrial organizations, number of livestock, purchase of commercial houses, drinking water source, and self-supply of food have significant negative effects. Based on the findings, we believe that local rural households operate in a complex livelihood system and recommend continuous interventions targeting key influences to provide empirical research support for areas facing similar situations.
  • Comparison of debris flow susceptibility assessment methods: support vector machine, particle swarm optimization, and feature selection techniques
    ZHAO Haijun, WEI Aihua, MA Fengshan, DAI Fenggang, JIANG Yongbing, LI Hui
    2024, 21(02): 397-412.
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    The selection of important factors in machine learning-based susceptibility assessments is crucial to obtain reliable susceptibility results. In this study, metaheuristic optimization and feature selection techniques were applied to identify the most important input parameters for mapping debris flow susceptibility in the southern mountain area of Chengde City in Hebei Province, China, by using machine learning algorithms. In total, 133 historical debris flow records and 16 related factors were selected. The support vector machine(SVM) was first used as the base classifier, and then a hybrid model was introduced by a two-step process. First, the particle swarm optimization(PSO) algorithm was employed to select the SVM model hyperparameters. Second, two feature selection algorithms, namely principal component analysis(PCA) and PSO, were integrated into the PSO-based SVM model, which generated the PCA-PSO-SVM and FS-PSO-SVM models, respectively. Three statistical metrics(accuracy, recall, and specificity) and the area under the receiver operating characteristic curve(AUC) were employed to evaluate and validate the performance of the models. The results indicated that the feature selection-based models exhibited the best performance, followed by the PSO-based SVM and SVM models. Moreover, the performance of the FS-PSO-SVM model was better than that of the PCA-PSO-SVM model, showing the highest AUC, accuracy, recall, and specificity values in both the training and testing processes. It was found that the selection of optimal features is crucial to improving the reliability of debris flow susceptibility assessment results. Moreover, the PSO algorithm was found to be not only an effective tool for hyperparameter optimization, but also a useful feature selection algorithm to improve prediction accuracies of debris flow susceptibility by using machine learning algorithms. The high and very high debris flow susceptibility zone appropriately covers 38.01% of the study area, where debris flow may occur under intensive human activities and heavy rainfall events.
  • Method for determining the position of landslide slip-surface with a typical inclinometric curves
    CHEN Hao, WU Hong-gang
    2024, 21(02): 413-432.
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    In the actual monitoring of deep hole displacement, the identification of slip surfaces is primarily based on abrupt changes observed in the inclinometric curve. In conventional identification methods, inclinometric curves exhibiting indications of sliding can be categorized into three types: B-type, D-type, and r-type. The position of the slip surface is typically determined by identifying the depth corresponding to the point of maximum displacement mutation. However, this method is sensitive to the interval of measurement points and the observation scale of the coordinate axes and suffers from unclear sliding surfaces and uncertain values. Based on the variation characteristics of these diagonal curves, we classified the landslide into three components: the sliding body, the sliding interval, and the immobile body. Moreover, three different generalization models were established to analyze the relationships between the curve form and the slip surface location based on different physical indicators such as displacement rate, relative displacement, and acceleration. The results show that the displacement rate curves of an r-type slope exhibit a clustering feature in the sliding interval, and by solving for the depth of discrete points within the step phase, it is possible to determine the location of the slip surface. On the other hand, D-type slopes have inflection points in the relative displacement curve located at the slip surface. The acceleration curves of B-type slopes exhibit clustering characteristics during the sliding interval, while the scattered acceleration data demonstrate wandering characteristics. Consequently, the slip surface location can be revealed by solving the depth corresponding to the maximum acceleration with cubic spline interpolation. The approach proposed in this paper was applied to the monitoring data of a landslide in Yunnan Province, China. The results indicate that our approach can accurately identify the slip surface location and enable computability of its position, thereby enhancing applicability and reliability of the deep-hole displacement monitoring data.
  • Elevation transition of aquatic insects closely matches a thermal feature in the Yungas of Northwestern Argentina
    Alexandra BUITRAGO-GUACANAME, Carlos MOLINERI, Andrés LIRA-NORIEGA, Daniel Andrés DOS SANTOS
    2024, 21(02): 433-448.
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    Temperature is a key factor that shapes the distribution of organisms. Having knowledge about how species respond to temperature is relevant to devise strategies for addressing the impacts of climate change. Aquatic insects are particularly vulnerable to climate change, yet there is still much to learn about their ecology and distribution. In the Yungas ecoregion of Northwestern Argentina, cold-and warm-adapted species of the orders Ephemeroptera, Plecoptera, and Trichoptera(EPT) are segregated by elevation. We modeled the ecological niche of South American EPT species in this region using available data and projected their potential distribution in geographic space. Species were grouped based on their ecogeographic similarity, and we analyzed their replacement pattern along elevation gradients, focusing on the ecotone where opposing thermal preferences converge. Along this interface, we identified critical points where the combined incidence of cold and warm assemblages maximizes,indicating a significant transition zone. We found that the Montane Cloud Forest holds the interface, with a particularly greater suitability at its lower boundary. The main axis of the interface runs in a N-S direction and falls between 14℃-16℃ mean annual isotherms. The probability of a particular location within a basin being classified as part of the interface increases as Kira's warmth index approaches a score around 150. Understanding the interface is critical for defining the thermal limits of species distribution and designing biomonitoring programs. Changes in the location of thermal constants related to mountainous ecotones may cause vertical displacement of aquatic insects and vegetation communities. We have recognized significant temperature thresholds that serve as indicators of suitability for the interface. As global warming is anticipated to shift these indicators, we suggest using them to monitor the imprints of climate change on mountain ecosystems.
  • Using satellite-derived land surface temperatures to clarify the spatiotemporal warming trends of the Alborz Mountains in northern Iran
    ROSHAN Gholamreza, SARLI Reza, GHANGHERMEH Abdolazim, TAHERIZADEH Mehrnoosh, NIKNAM Arman
    2024, 21(02): 449-469.
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    The Alborz Mountains are some of the highest in Iran, and they play an important role in controlling the climate of the country's northern regions. The land surface temperature(LST) is an important variable that affects the ecosystem of this area. This study investigated the spatiotemporal changes and trends of the nighttime LST in the western region of the Central Alborz Mountains at elevations of 1500–4000 m above sea level. MODIS data were extracted for the period of 2000–2021, and the Mann–Kendall nonparametric test was applied to evaluating the changes in the LST. The results indicated a significant increasing trend for the monthly average LST in May–August along the southern aspect. Both the northern and southern aspects showed decreasing trends for the monthly average LST in October, November, and March and an increasing trend in other months. At all elevations, the average decadal change in the monthly average LST was more severe along the southern aspect(0.60℃) than along the northern aspect(0.37℃). The LST difference between the northern and southern aspects decreased in the cold months but increased in the hot months. At the same elevation, the difference in the lapse rate between the northern and southern aspects was greater in the hot months than in the cold months. With increasing elevation, the lapse rate between the northern and southern aspects disappeared. Climate change was concluded to greatly decrease the difference in LST at different elevations for April–July.
  • Tracing suspended and bed sediments during high and low water periods using geochemical characteristics-Case study:Vazrood watershed, northern Iran
    KARIMI Nabiyeh, GHOLAMI Leila, KAVIAN Ataollah, KHALEDI DARVISHAN Abdulvahed
    2024, 21(02): 470-483.
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    Complete and comprehensive information about sediment dynamic and identification of hotspots of sediment production and transport are necessary for understanding the erosion processes and increasing the efficiency of soil and water conservation practices. Numerous studies used the sediment fingerprint techniques to investigate the contribution of different sources in suspended and bed sediment yield of the watersheds. However, the contribution of various land use/land covers in suspended and bed sediment yield for the great Caspian Sea basin is in an aura of ambiguity and the present study was conducted to gather information about an important part of this area in northern Iran, where rangelands are located upstream of Hyrcanian forests and dense agricultural lands are located downstream. The surface soil of different land use/land covers including forest, rangeland, agriculture and streambank lands were sampled in 30 points. Suspended and bed sediments were sampled in the watershed outlet in two high and low water periods. Geochemical characteristics of soil and sediment samples containing 59 elements were measured using ICP-OES GBC Integra. The reliable and suitable tracers from 59 elements were then selected using Range test, Kruskal-Wallis and Discriminant Function Analysis, respectively, in Finger Pro package of R software. The results showed that for suspended sediment, streambank and rangeland had the highest contributions of 86.2% and 47.5%, respectively, in two high and low water periods. For bed sediment, in two high and low water periods, rangeland and streambank had the highest contributions of 73.8% and 84.4 %, respectively. Land use change and especially human activities such as agriculture, road construction and development of residential areas along the main river riparian zone has led to a significant increase in suspended and bed sediments.
  • Uphill or downhill? Cropland use change and its drivers from the perspective of slope spectrum
    PAN Sipei, LIANG Jiale, CHEN Wanxu, PENG Yelin
    2024, 21(02): 484-499.
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    The continuous decrease of low-slope cropland resources caused by construction land crowding poses huge threat to regional sustainable development and food security. Slope spectrum analysis of topographic and geomorphic features is considered as a digital terrain analysis method which reflects the macro-topographic features by using micro-topographic factors. However, pieces of studies have extended the concept of slope spectrum in the field of geoscience to construction land to explore its expansion law, while research on the slope trend of cropland from that perspective remains rare. To address the gap, in virtue of spatial analysis and geographically weighted regression(GWR) model, the cropland use change in the Yangtze River Basin(YRB) from 2000 to 2020 was analyzed and the driving factors were explored from the perspective of slope spectrum. Results showed that the slope spectrum curves of cropland area-frequency in the YRB showed a first upward then a downward trend. The change curve of the slope spectrum of cropland in each province(municipality) exhibited various distribution patterns. Quantitative analysis of morphological parameters of cropland slope spectrum revealed that the further down the YRB, the stronger the flattening characteristics, the more obvious the concentration. The province experienced the greatest downhill cropland climbing(CLC) was Shannxi, while province experienced the highest uphill CLC was Zhejiang. The most common cropland use change type in the YRB was horizontal expansion type. The factors affecting average cropland climbing index(ACCI) were quite stable in different periods, while population density(POP) changed from negative to positive during the study period. This research is of practical significance for the rational utilization of cropland at the watershed scale.
  • Temperature trends and its elevation-dependent warming over the Qilian Mountains
    ZHAO Peng, HE Zhibin, MA Dengke, WANG Wen, QIAN Lihui
    2024, 21(02): 500-510.
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    Understanding temperature variability especially elevation dependent warming(EDW) in high-elevation mountain regions is critical for assessing the impacts of climate change on water resources including glacier melt, degradation of soils, and active layer thickness. EDW means that temperature is warming faster with the increase of altitude. In this study, we used observed temperature data during 1979-2017 from 23 meteorological stations in the Qilian Mountains(QLM) to analyze temperature trend with Mann-Kendall(MK) test and Sen's slope approach. Results showed that the warming trends for the annual temperature followed the order of T＿min > T＿mean > T＿max and with a shift both occurred in 1997. Spring and summer temperature have a higher increasing trend than that in autumn and winter. T＿mean shifts occurred in 1996 for spring and summer, in 1997 for autumn and winter. T＿max shifts occurred in 1997 for spring and 1996 for summer. T＿min shifts occurred in 1997 for spring, summer and winter as well as in 1999 for autumn. Annual mean diurnal temperature range(DTR) shows a significant decreasing trend(–0.18℃/10a) from 1979 to 2017. Summer mean DTR shows a significant decreasing trend(–0.26℃/10a) from 1979 to 2017 with a shift occurred in 2010. After removing longitude and latitude factors, we can learn that the warming enhancement rate of average annual temperature is 0.0673℃/km/10a, indicating that the temperature warming trend is accelerating with the continuous increase of altitude. The increase rate of elevation temperature is 0.0371℃/km/10a in spring, 0.0457℃/km/10a in summer, 0.0707℃/km/10a in autumn, and 0.0606℃/km/10a in winter, which indicates that there is a clear EDW in the QLM. The main causes of warming in the Qilian Mountains are human activities, cloudiness, ice-snow feedback and El Nino phenomenon.
  • Phenology of different types of vegetation and their response to climate change in the Qilian Mountains, China
    ZHAO Kaixin, LI Xuemei, ZHANG Zhengrong, LIU Xinyu
    2024, 21(02): 511-525.
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    The Qilian Mountains(QM) possess a delicate vegetation ecosystem, amplifying the evident response of vegetation phenology to climate change. The relationship between changes in vegetation growth and climate remains complex. To this end, we used MODIS NDVI data to extract the phenological parameters of the vegetation including meadow(MDW), grassland(GSD), and alpine vegetation(ALV) in the QM from 2002 to 2021. Then, we employed path analysis to reveal the direct and indirect impacts of seasonal climate change on vegetation phenology. Additionally, we decomposed the vegetation phenology in a time series using the trigonometric seasonality, Box-Cox transformation, ARMA errors, and Trend Seasonal components model(TBATS). The findings showed a distinct pattern in the vegetation phenology of the QM, characterized by a progressive shift towards an earlier start of the growing season(SOS), a delayed end of the growing season(EOS), and an extended length of the growing season(LOS). The growth cycle of MDW, GSD, and ALV in the QM species is clearly defined. The SOS for MDW and GSD occurred earlier, mainly between late April and August, while the SOS for ALVs occurred between mid-May and midAugust, a one-month delay compared to the other vegetation. The EOS in MDW and GSD were concentrated between late August and April and early September and early January, respectively. Vegetation phenology exhibits distinct responses to seasonal temperature and precipitation patterns. The advancement and delay of SOS were mainly influenced by the direct effect of spring temperatures and precipitation, which affected 19.59% and 22.17% of the study area, respectively. The advancement and delay of EOS were mainly influenced by the direct effect of fall temperatures and precipitation, which affected 30.18% and 21.17% of the area, respectively. On the contrary, the direct effects of temperature and precipitation in summer and winter on vegetation phenology seem less noticeable and were mainly influenced by indirect effects. The indirect effect of winter precipitation is the main factor affecting the advance or delay of SOS, and the area proportions were 16.29% and 23.42%, respectively. The indirect effects of fall temperatures and precipitation were the main factors affecting the delay and advancement of EOS, respectively, with an area share of 15.80% and 21.60%. This study provides valuable insight into the relationship between vegetation phenology and climate change, which can be of great practical value for the ecological protection of the Qinghai-Tibetan Plateau as well as for the development of GSD ecological animal husbandry in the QM alpine pastoral area.
  • Local failure mechanism of sand-blocking fence in latticed dune along desert roads
    LI Liangying, LV Lele, LI Qi, WANG Zhenqiang, YANG Youhai, YIN Wenhua
    2024, 21(02): 526-537.
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    The latticed dunes in the Tengger Desert are widely distributed, and the sand-blocking fence placed here are highly susceptible to local failure due to complex wind-sand activities, posing a serious threat to the safe operation of the highway. To explore the local failure mechanism of sand-blocking fence in the latticed dune area, the local failure of sandblocking fence in the latticed dune areas along the Wuhai-Maqin Highway in China was observed. Taking the first main ridge of the latticed dune as the placement location, the structure of the wind-sand flow field of sand-blocking fence placed at top, the bottom and the middle of windward slope was analyzed by Computational Fluid Dynamics(CFD). The results show that when placed at top of the first main ridge, the wind speed near the sand-blocking fence is the highest, up to 15.23 m/s. Therefore, the wind load strength on the sand barrier is correspondingly larger, up to 232.61 N·m~(-2). As the strength of material continues to decrease, the nylon net is prone to breakage. The roots of the angle steel posts are susceptible to hollowing by vortex action, which can cause sand-blocking fence to fall over in strong wind conditions. When placed at the bottom of windward slope, wind speed drop near sand-blocking fence is greatest, with the decrease of 12.48-14.32 m/s compared to the original wind speed. This is highly likely to lead to large-scale deposition of sand particles and burial of the sand-blocking fence. When placed in the middle of windward slope, sand-blocking fence is subjected to less wind load strength(168.61N·m~(-2)) and sand particles are mostly deposited at the bottom of windward slope, with only a small amount of sand accumulating at the root of sand-blocking fence. Based on field observations and numerical modelling results, when the sand-blocking fence is placed in latticed dune area, it should be placed in the middle of the windward slope of the first main ridge as a matter of priority. Besides the sand-blocking fence should be placed at the top of the first main ridge,and sand fixing measures should be added.
  • Numerical simulation on sand sedimentation and erosion characteristics around HDPE sheet sand barrier under different wind angles
    ZHANG Kai, ZHANG Peili, ZHANG Hailong, TIAN Jianjin, WANG Zhenghui, XIAO Jianhua
    2024, 21(02): 538-554.
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    For the safety of railroad operations, sand barriers are utilized to mitigate wind-sand disaster effects. These disasters, characterized by multidirectional wind patterns, result in diverse angles among the barriers. In this study, using numerical simulations, we examined the behavior of High Density Polyethylene(HDPE) sheet sand barriers under different wind angles, focusing on flow field distribution, windproof efficiency, and sedimentation erosion dynamics. This study discovered that at a steady wind speed, airflow velocity varies as the angle between the airflow and the HDPE barrier changes. Specifically, a 90° angle results in the widest low-speed airflow area on the barrier's downwind side. If the airflow is not perpendicular to the barrier, it prompts a lateral airflow movement which decreases as the angle expands. The windproof efficiency correlates directly with this angle but inversely with the wind's speed. Notably, with a wind angle of 90°, wind speed drops by 81%. The minimum wind speed is found at 5.1H(the sand barrier height) on the barrier's downwind side. As the angle grows, the barrier's windproof efficiency improves, extending its protective reach. Sedimentation is most prominent on the barrier's downwind side, as the wind angle shifts from 30° to 90°, the sand sedimentation area on the barrier's downwind side enlarges by 14.8H. As the angle grows, sedimentation intensifies, eventually overtakes the forward erosion and enlarges the sedimentation area.
  • Adaptation analysis and fusion correction method of CMIP6 precipitation simulation data on the Qinghai-Tibetan Plateau
    PENG Hao, QIN Dahui, WANG Zegen, ZHANG Menghan, YANG Yanmei, YONG Zhiwei
    2024, 21(02): 555-573.
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    In order to obtain more accurate precipitation data and better simulate the precipitation on the Tibetan Plateau, the simulation capability of 14 Coupled Model Intercomparison Project Phase 6(CMIP6) models of historical precipitation(1982-2014) on the Qinghai-Tibetan Plateau was evaluated in this study. Results indicate that all models exhibit an overestimation of precipitation through the analysis of the Taylor index, temporal and spatial statistical parameters. To correct the overestimation, a fusion correction method combining the Backpropagation Neural Network Correction(BP) and Quantum Mapping(QM) correction, named BQ method, was proposed. With this method, the historical precipitation of each model was corrected in space and time, respectively. The correction results were then analyzed in time, space, and analysis of variance(ANOVA) with those corrected by the BP and QM methods, respectively. Finally, the fusion correction method results for each model were compared with the Climatic Research Unit(CRU) data for significance analysis to obtain the trends of precipitation increase and decrease for each model. The results show that the IPSL-CM6A-LR model is relatively good in simulating historical precipitation on the Qinghai-Tibetan Plateau(R=0.7, RSME=0.15) among the uncorrected data. In terms of time, the total precipitation corrected by the fusion method has the same interannual trend and the closest precipitation values to the CRU data; In terms of space, the annual average precipitation corrected by the fusion method has the smallest difference with the CRU data, and the total historical annual average precipitation is not significantly different from the CRU data, which is better than BP and QM. Therefore, the correction effect of the fusion method on the historical precipitation of each model is better than that of the QM and BP methods. The precipitation in the central and northeastern parts of the plateau shows a significant increasing trend. The correlation coefficients between monthly precipitation and sitedetected precipitation for all models after BQ correction exceed 0.8.
  • Identifying flow regime in the aquifer of fractured rock system in Germi Chai Basin, Iran
    VAEZIHIR Abdorreza, SEPEHRIPOUR Ali, TABARMAYEH Mehri
    2024, 21(02): 574-589.
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    Considering the importance of fractured rock aquifers in the hydrogeologic process, this research aimed to analyze the flow regime, internal degree of karstification, and estimate storage volume in fractured rock aquifers of the Germi Chai Basin in northwest Iran, which is attributed to its active tectonics, erosion, and the lithological diversity. Given the geological setting, the hypothesis is that this basin is characterized by a high degree of karstification and diffuse or intermediate flow regime leading to variation in discharge flow rate. The hydrodynamic and hadrochemical analysis was conducted on 9 welldistributed springs across the basin from 2019 to 2020. The maximum flow rate in most of the springs appeared in the early wet season despite their different levels of fluctuations on the monthly discharge time series. Analyzing the spring recession curve form revealed an aquifer containing multiple micro-regimes with α recession coefficients and a degree of karstification ranging between 0.001 to 0.06 and 0.55 to 2.61, respectively. These findings indicated a dominant diffuse and intermediate flow system resulting from the development of a high density of fractures in this area. The electrical conductivity of the spring changes inversely proportional to the change in flow discharge, indicating the reasonable hydrological response of the aquifer to rainfall events. Hydrograph analysis revealed that the delay time of spring discharge after rainfall events mostly varies between 10 to 30 days. The total dynamic storage volume of the spring for a given period(2019-2020) was estimated to be approximately 1324 million cubic meters reflecting the long-term drainage potential and high perdurability of dynamic storage. Estimating the maximum and minimum ratio revealed that the springs recharging system in Germi Chai Basin comes under the slow aquifers category. This finding provides valuable insight into the hydrogeological properties of fractured rock aquifers contributing to effective water management strategy.
  • Influence of edaphic factors on distribution and condition of Himalayan silver birch(Betula utilis D. Don) communities in the northwestern Indian Himalayas
    Khashti DASILA, Renu RAWAL, Tanay BARMAN, Sher Singh SAMANT, Anita PANDEY, Veena PANDE
    2024, 21(02): 590-606.
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    The basic concept of phytosociology is crucial for the assessment of species composition and dynamic ecological succession of forests supporting ecological services, functions, disturbance, and resilience that lead to the development of integrated areas such as ecological niche modeling and contribute to identifying the valuable bio-indicators which can be used in framing conservation and management planning. B. utilis is one of the most dominant tree species of treeline ecotone in the Himalayan Region. The species is also considered as indicator species for monitoring the past and recent climate change impact. The current study was carried out in the natural populations of B. utilis from the sub-alpine zone of North-western Indian Himalaya. The birch dominated forest harbors a total of 305 plant species comprising Angiosperms(51 families, 160 genera and 277 species), Gymnosperms(03 families, 05 genera and 07 species) and Pteridophytes(07 families, 11 genera and 21 species) with Asteraceae, Ranunculaceae and Rosaceae as dominant family. Birch forests are found dominant in shady moist habitat and North West aspect. Geographical characteristics, anthropogenic and developmental activities affect the population structure of B. utilis and associated species. However, the species has fair regeneration status in the study area. The acidic nature of soil pH and spatial variation in edaphic characteristics may be due to geographical differences, rooting patterns and litter accumulation of below and above-ground vegetation. Biomass estimation of a representative population of B. utilis from each site showed that TAGBD, TCD and TBD were found maximum in ST3(Hamta Pass Ⅱ site). The CCA analysis determined that environmental variables such as altitude, organic matter, available phosphorous, organic carbon, available nitrogen, and electrical conductivity played a significant role in determining tree species composition and distribution in B. utilis dominated forests.
  • Precipitation and anthropogenic activities regulate the changes of NDVI in Zhegucuo Valley on the southern Tibetan Plateau
    ZHAO Wanglin, WANG Hengying, ZHANG Huifang, ZHANG Lin
    2024, 21(02): 607-618.
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    Whether climate change or anthropogenic activities play a more pivotal role in regulating vegetation growth on the Tibetan Plateau is still controversial. A better understanding on grassland changes at a fine scale may provide important guidance for local government policy and grassland management. Using two of the most reliable satellite NDVI products(MODIS NDVI and SPOT NDVI), we evaluated the dynamic of grasslands in the Zhegucuo valley on the southern Tibetan Plateau from 2000 to 2020, and analyzed its driving factors and relative influences of climate change and anthropogenic activities. Here, the key indicators of climate change were assumed to be precipitation and temperature. The main results were:(1) the grassland NDVI in Zhegucuo valley did not reflect a significant temporal change during the last 21 years. The variation of precipitation during the early growing season(GSP) resembled that of NDVI, and the GSP was positively correlated with NDVI. At the pixel level, the partial correlation analysis showed that 37.79% of the pixels depicted a positive relationship between GSP and NDVI, while 11.32% of the pixels showed a negative relationship between temperature during the early growing season(GST) and NDVI.(2) In view of the spatial distribution, the areas mainly controlled by GSP were generally distributed in the southern part, while those affected by GST stood in the eastern part, mainly around the Zhegucuo lake where most population in Cuomei County settled down.(3) Decreasing NDVI trends were mainly occurred in alpine steppe at lower elevations rather than alpine meadow at higher elevations.(4) The residual trend(RESTREND) analysis further indicated that the anthropogenic activities played a more pivotal role in regulating the annual changes of NDVI rather than climate factors in this area. Future studies should pay more attention on climate extremes rather than the simple temporal trends. Also, the influence of human activities on alpine grassland needs to be accessed and fully considered in future sustainable management.
  • Impacts of road on plant invasions in the Middle Mountain region of central Nepal
    Ananda ADHIKARI, Adarsha SUBEDI, Achyut TIWARI, Bharat Babu SHRESTHA
    2024, 21(02): 619-632.
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    Biological invasion is triggered by human development activities such as the construction and expansion of road networks. Road verges serve as important habitats and corridors for the distribution of invasive alien plant species(IAPS) between geographically distant habitats. However, the trajectory of plant invasion and the data regarding the impact of roads on IAPS distribution are relatively poor in Nepal. Here, we surveyed two road types(main roads and feeder road) in the Middle Mountain region of central Nepal in order to investigate how different road types are driving the dispersal of IAPS along road verges and the adjacent natural habitats. Systematic sampling was conducted at ca 2.5 km intervals along the roads. At each sampling site, paired plots(25 m × 4 m) were sampled: one adjacent to and along the road, and another 20 m away and parallel to it in the interior habitat. Our results revealed that the main road verges had a higher cover(33%) and a larger number of IAPS(14 species) than the feeder road(25%; 10 species). The IAPS cover and richness were significantly higher along verges than in the adjacent interior habitats for both road types, indicating that roads are contributing as corridors for the dispersal of IAPS in the Middle Mountain areas of central Nepal. Further, elevation,tree canopy, and disturbances(grazing/mowing/trampling) were found to be the key factors that determine spatial distribution of IAPS along road verges. We emphasize that regular monitoring of vegetation along the road verges can help with the early detection and control of potential IAPS in the region before they become problematic.
  • A semi-infinite beam theoretical model on predicting rock slope subsidence induced by underground mining
    LIU Xinrong, WANG Nanyun, ZHONG Zuliang, DU Libing, LIANG Erwei
    2024, 21(02): 633-647.
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    When the mining goaf is close to the cliff, rock slope subsidence induced by underground mining is significantly affected by its boundary conditions. In this study, an analytical method is proposed by considering the key strata as a semi-infinite EulerBernoulli beam rested on a Winkler foundation with a local subsidence area. The analytical solutions of deflection are derived by analyzing the boundary and continuity conditions of the cliff. Then, the analytical solutions are verified by the results from experimental tests, FEM and In SAR, respectively. After that, the influence of changing parameters on deflections is studied with sensitivity analysis. The results show that the distance between goaf and cliff significantly affects the deflection of semi-infinite beam. The response of semi-infinite beam is obviously determined by the length of goaf and the bending stiffness of beam. The comparisons between semi-infinite beam and infinite beam illustrate the ascendancy of the improved model in such problems.
  • Triaxial mechanical properties and precursors of instability damage in rocks with different laminar dip angles
    SUN Xiaoming, SHI Fukun, DING Jiaxu, TAO Zhigang, HE Linsen, YANG Liu, ZHANG Yong, MIAO Chengyu
    2024, 21(02): 648-661.
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    To investigate the mechanical failure characteristics of volcanic breccia with different bedding dip angles in deep layers, triaxial compression experiments were conducted on specimens taken from volcanic rock layers in the Junggar Basin, Xinjiang. By changing the confining pressure, we compared the mechanical properties, acoustic emission characteristics, and fractal features of the acoustic emission sequence for volcanic breccia with different bedding dip angles. The research results indicate that as the bedding dip angle increases, peak strength, internal friction angle, and cohesion exhibit a “U-shaped” variation pattern. The correlation dimension of the acoustic emission amplitude was calculated using the G-P algorithm, revealing that volcanic breccia exhibits fractal characteristics. Furthermore, a positive correlation between the correlation dimension and the bedding dip angle was observed. When the stress of the test specimen reaches 0.8σ_c, there is a significant decrease in the fractal dimension, serving as a criterion for predicting the failure of the specimen. By analyzing the changes in fractal dimension at different stress levels, the slope of the fractal dimension ΔD <-0.5 can be used as a precursor to failure for test specimens with a bedding dip angle of 15° ≤ β ≤ 45°. Similarly, when the bedding dip angle of the specimen is 0° ≤ β < 15° or 45° < β ≤ 90°, ΔD < 0 can be considered as a precursor to specimen failure. This study provides theoretical references for understanding the failure patterns of volcanic rock.
  • Topographic seismic effects and avalanche hazard:A case study of Mount Siella(L'Aquila, Central Italy)
    Ferdinando TOTANI
    2024, 21(02): 662-675.
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    In mountainous areas, snow avalanches could be triggered by the shaking produced by earthquakes. The forces induced by the earthquake can cause an irregular increase of shear strength load down the slope, for the presence of complex surface and buried morphologies. Topographic irregularities generate maximum effects of waves amplification linked to wavelengths comparable to the horizontal dimension of the topographic feature. For this reason, the selected time-histories represent an appropriate input for the two-dimensional numerical response analyses when a dynamic phenomenon produce the resonant motion of a whole mountain. This represents an important earthquake-induced hazard in snowcovered mountain areas with high probability of seismic events. Some valleys are located in regions with scare ground motion data and investments on infrastructures are not always accompanied by adequate protection against earthquake-induced avalanches. The paper points out a simple deterministic approach for selecting a set of real accelerograms applied to a real case of Siella Mountain(Central Italy) where a large avalanche destroying a tourist facility of Rigopiano resort on 18 January 2017. The selected time histories were used as input for the two-dimensional numerical model of the subsoil to evaluate the topographic seismic amplification in ridge and compare it with the results of other authors. These methods suggest that morphology-related inertial effects should be considered as an overload action on snow layers when controlling multi-hazard studies and spatial planning.
  • Impact resistance performance and optimization of the sand-EPE composite cushion in rock sheds
    YU Bingxin, ZHOU Xiaojun, TANG Jianhui, ZHANG Yujin, ZHANG Yuefeng
    2024, 21(02): 676-689.
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    Rock sheds are widely used to prevent rockfall disasters along roads in mountainous areas. To improve the capacity of rock sheds for resisting rockfall impact, a sand and expandable polyethylene(EPE) composite cushion was proposed. A series of model experiments of rockfall impact on rock sheds were conducted, and the buried depth of the EPE foam board in the sand layer was considered. The impact load and dynamic response of the rock shed were investigated. The results show that the maximum impact load and dynamic response of the rock shed roof are all significantly less than those of the sand cushion. Moreover, as the distance between the EPE foam board and rock shed roof decreases, the maximum rockfall impact force and impact pressure gradually decrease, and the maximum displacement, acceleration and strain of the rock shed first decrease and then change little. In addition, the vibration acceleration and vertical displacement of the rock shed roof decrease from the centre to the edge and decrease faster along the longitudinal direction than that along the transverse direction. In conclusion, the buffering effect of the sand-EPE composite cushion is better than that of the pure sand cushion, and the EPE foam board at a depth of 1/3 the thickness of the sand layer is appropriate.
  • Machine learning-enhanced Monte Carlo and subset simulations for advanced risk assessment in transportation infrastructure
    Furquan AHMAD, Pijush SAMUI, S.S.MISHRA
    2024, 21(02): 690-717.
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    The maintenance of safety and dependability in rail and road embankments is of utmost importance in order to facilitate the smooth operation of transportation networks. This study introduces a comprehensive methodology for soil slope stability evaluation, employing Monte Carlo Simulation(MCS) and Subset Simulation(SS) with the "UPSS 3.0 Add-in" in MS-Excel. Focused on an 11.693-meter embankment with a soil slope(inclination ratio of 2H:1V), the investigation considers earthquake coefficients(k_h) and pore water pressure ratios(r_u) following Indian zoning requirements. The chance of slope failure showed a considerable increase as the Coefficient of Variation(COV), seismic coefficients(k_h), and pore water pressure ratios(r_u) experienced an escalation. The SS approach showed exceptional efficacy in calculating odds of failure that are notably low. Within computational modeling, the study optimized the worst-case scenario using ANFIS-GA, ANFIS-GWO, ANFIS-PSO, and ANFIS-BBO models. The ANFIS-PSO model exhibits exceptional accuracy(training R~2 = 0.9011, RMSE = 0.0549; testing R~2 = 0.8968, RMSE = 0.0615), emerging as the most promising. This study highlights the significance of conducting thorough risk assessments and offers practical insights into evaluating and improving the stability of soil slopes in transportation infrastructure.These findings contribute to the enhancement of safety and reliability in real-world situations.