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过刊目录

  • 2022年, 19卷, 第09期
    刊出日期：2024-06-19
      
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  • Morphodynamic development of the Terkhiin Tsagaan Lake Depression,Central Mongolia: Implications for the relationships of Faulting, Volcanic Activity, and Lake Depression Formation
    Altanbold ENKHBOLD, Ulambadrakh KHUKHUUDEI, Timothy KUSKY, CHUN Xi, Gansukh YADAMSUREN, Byambabayar GANBOLD, Tuvshin GERELMAA
    2022, 19(09): 2451-2468.
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    Data on the origin and morphology of lake depressions caused by volcanism are scarce in Mongolia. Previous studies focused on climate change patterns based on Terkhiin Tsagaan Lake sediment.We present a result of existing reconstructions of lake depression development and changes in the hydrology system during the Khorgo volcanic activation and the Holocene environmental change. A depression of the Terkhiin Tsagaan Lake is formed by a lava flow barrier from the Khorgo volcano. However, the Khorgo volcanic eruption and the lake depression that could shape a large lake have arisen instead from a fault. The morphometric analysis and field measurements indicate that the derivation of the Terkhiin Tsagaan Lake depression and Khorgo volcano may have evolved from movement on a sinistral strike-slip fault, which is about 70 km long.The southern mountains and rivers were displaced from northwest to southeast along the Terkh Fault.The offset along Terkh Fault is 4.02-5.28 km in the depression of the Terkhiin Tsagaan Lake. After movement, a wide valley of the Terkh River developed in the present landscape. The active Khorgo Volcano formed along the Khorgo Fault. The Terkhiin Tsagaan Lake is formed by blocked water from the PaleoTerkh River after lava damming from the Khorgo Volcano. The initial paleo-lake area was about 195.7km~2, which was three times larger than the modern lake. The current water volume of the Terkhiin Tsagaan Lake is 0.351 km~3 while the volume of the paleo-lake was 2.248 km~3. Based on this volume indicator the paleo-lake was 6.4 times larger than the current lake. Overflowing water from the lake depression formed the Suman River by a drying canyon through the lava plateau, but the canyon is along the Terkh Fault. Changes in the water volume of Terkhiin Tsagaan Lake and erosion of Suman River canyon are inversely related to each other. We present the morphometric relationships between the lava plateau of Khorgo Volcano and development of Terkhiin Tsagaan Lake depression.
  • Comprehensive interpretation of the Sedongpu glacier-related mass flows in the eastern Himalayan syntaxis
    ZHANG Xiao-peng, HU Kai-heng, LIU Shuang, NIE Yong, HAN Yun-zhong
    2022, 19(09): 2469-2486.
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    Glacier-related mass flows(GMFs) in the high-mountain cryosphere have become more frequent in the last decade, e.g., the 2018 Sedongpu(SDP) GMFs in the Himalayas. Seismic forcing,thermal perturbation and heavy rainfall are common triggers of the GMFs. But the exact role of seimic forcing in the GMF formation is poorly known due to scarity of observational data of real cases. Here the evolution processes of the GMFs and the detachment of the trunk glacier in SDP are reconstructed by using remote sensing techniques, including feature-tracking of multi-source optical satellite imagery and visual interpretation. The reconstruction demonstrates that the high frequency of GMF events in SDP after the Milin earthquake on 18 November 2017 was mainly attributed to the earthquake-induced glacial stress changes and destablisation. The post-earthquake velocity of the trunk glacier is about three times of that in December 2016 and December 2017. The median glacier-surface velocity raised to 0.32 m d-1between November 2017 and June 2018, being 14%-77% higher than that of pre-earthquake, which is initiated by the seismic forcing and then aggravated by additional loading of ice/rock avalanches,infiltration of liquid water, progressively crevassed glacier, and local compressional deformation.Ensuing surge motion of the trunk glacier resulted from high temperature and heavy precipitation between July and September 2018. We infer that the trunk glacier is more sensitive to the thermal perturbation after the Milin earthquake, which is the predominant cause in sudden surge movement. These findings reveal comprehensive mechanisms of quakeinduced, low-angle, glacial detachment and multisource-driven GMF in the Himalayas.
  • Degradation and recovery of alpine meadow catenas in the source zone of the Yellow River, Western China
    BRIERLEY Gary, LI Xi-lai, FRYIRS Kirstie, GAO Jay, SHI Yan, PERRY George L.W., CULLUM Carola
    2022, 19(09): 2487-2505.
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    Process interactions on catenas have supported grazing adapted ecosystems and sustained biodiversity values in the source zone of the Yellow River in western China for millennia. In recent decades, anthropogenic disturbance and climate change have threatened the integrity of these systems,impacting upon environmental values and their capacity to sustain local livelihoods. Collaborations between local experts and a team of international researchers during a workshop and field excursion to this area in July 2019 developed a cross-disciplinary,process-based model of alpine meadow catenas. This paper relates the contemporary health of these grassland-wetland systems to their ‘best achievable state' under prevailing boundary conditions,differentiating stages of degradation and recovery in relation to climate and land use changes. Recovery is underway for alpine meadow catenas at Maqin.Reduced land use pressures(stocking rates) and longer growing seasons have enhanced grasslandwetland conditions. However, recovery prospects are limited for local areas of extremely degraded grasslands(heitutan), as breached abiotic thresholds have resulted in soil and nutrient loss and reduced capacity for water retention. While lagomorphs and rodents act as ecosystem engineers when alpine meadows are in a healthy state, irruptions locally increase the proportion of bare ground and inhibit recovery potential. Management options that support recovery of alpine meadows are presented for differing stages of degradation.
  • Machine learning model for snow depth estimation using a multisensory ubiquitous platform
    Sofeem NASIM, Mourad OUSSALAH, Bj?rn KL?VE, Ali Torabi HAGHIGHI
    2022, 19(09): 2506-2527.
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    Snow depth estimation is an important parameter that guides several hydrological applications and climate change prediction. Despite advances in remote sensing technology and enhanced satellite observations, the estimation of snow depth at local scale still requires improved accuracy and flexibility. The advances in ubiquitous and wearable technology promote new prospects in tackling this challenge. In this paper, a wearable IoT platform that exploits pressure and acoustic sensor readings to estimate and classify snow depth classes using some machine-learning models have been put forward.Significantly, the results of Random Forest classifier showed an accuracy of 94%, indicating a promising alternative in snow depth measurement compared to in situ, LiDAR, or expensive large-scale wireless sensor network, which may foster the development of further affordable ecological monitoring systems based on cheap ubiquitous sensors.
  • Old climatically-buffered infertile landscapes(OCBILs): more than harsh habitats, Atlantic Forest inselbergs can be drivers of evolutionary diversity
    Felipe de CARVALHO ARAúJO, Natália de AGUIAR-CAMPOS, Cleber Rodrigo de SOUZA, Eduardo de Paiva PAULA, Rubens Manoel dos SANTOS
    2022, 19(09): 2528-2543.
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    Granite-gneiss rock outcrop inselbergs are ancient stable ecosystems with old, climaticallybuffered infertile landscapes(OCBILs). Although inselbergs provide key ecosystem services, little is done for their conservation and, so far, a lot of their unknown evolutionary history has already been lost by human activities. Using a fine-scale approach, here we tested if habitat and environmental filtering(the inselberg's harshness) affect the evolutionary diversity of an Atlantic Forest inselberg in Brazil. We recorded all trees with a diameter at breast height ≥ 5cm in 20 plots in four habitat types(total sampled area of 0.8 hectares), from highest to lowest: island,hillside, foothill, and semideciduous forest(matrix).We also collected soil samples for chemical, textural and physical soil characterization. We fitted linear models to test the effects of soil and habitat on plotlevel metrics of phylogenetic diversity and structure,lineage diversity, phylogenetic β-diversity, and evolutionary distinctiveness. We found that the upper inselberg habitats contain a distinct set of ancient,closely related, harsh-tolerant lineages, as well as a subset of lineages that persist under harsh conditions with a certain degree of water availability. The inferior inselberg habitats harbor higher lineage diversity than expected by chance. Soil strongly predicted evolutionary diversity. We concluded that soil depth,slope, nutrients and texture(environmental filtering)and habitat types and topography(habitat filtering)shape the evolutionary history contained in fine-scale inselberg habitats, which should encourage the conservation of these ancient ecosystems.
  • Spatiotemporal variation of the loose deposits in Baisha River Basin after the 2008 Wenchuan earthquake
    LYU Jiao-rong, BAO Yu-hai, XIE Hang-yu, LI Hong, HU Yun-hua, HE Xiu-bin
    2022, 19(09): 2544-2555.
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    Extensive landslides were triggered by the Wenchuan earthquake(in China) on 12 May 2008,causing a tremendous amount of loose material suspended on the hillslopes, likely to be eroded and transported by rain. It is of great significance to study the long-term variation of the quantity and spatiotemporal distribution of loose deposits after a great earthquake in order to understand the restoration process, to assess the risk of future soil erosion, including geological hazards, and to further develop ecological governance strategy. In this study,information about the multi-temporal loose deposits on the ranges of the Baisha River Basin, an alpine valley near the epicenter, was extracted by objectoriented remote sensing interpretation, and analysis on their spatiotemporal variation showed that the earthquake in 2008 resulted in loose deposits covering an additional area of 81.09 km2, with a volume estimated at 0.357 billion m3. Within five years after the earthquake, the vegetation had recovered rapidly, and the extent of the deposits was significantly less. From 5 to 13 years after the earthquake, the vegetation continued to recover but at a slower rate and a decreasing trend in newly formed deposits was evident. The total area, volume and quantity of the loose deposits gradually stabilized. The geometric mean center of the loose deposits gradually moved back towards the upstream area after the earthquake and, by 2021, the mean center was about 4 km away from its pre-earthquake position. Taking the mean center of the loose deposits in 2008 as the center, the deposits in the downstream area shrank significantly after the earthquake, but collapses and landslides of deposits persisted in the upstream area to the west-southwest, west-northwest and northnorthwest from the mean center, indicating future source areas of new loose deposits in the basin.
  • Effect of Zn~(2+)-Cu~(2+) combined heavy metal on mechanical properties and microstructure of clayey soil
    MA Qiang, WU Nian-ze, XIAO Heng-lin, LI Wen-tao, XIANG Jun-chen
    2022, 19(09): 2556-2569.
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    The strength deterioration mechanism of soil polluted by heavy metals plays a crucial role in the research of mine site pollution. In this study, an unconfined compressive strength(UCS) test, a p H test, a scanning electron microscopy(SEM) test, a low filed nuclear magnetic resonance(NMR) test, and an X-ray diffraction(XRD) test were conducted on Zn~(2+),Cu~(2+) and the combination of Zn~(2+) and Cu~(2+) polluted soil to investigate the strength deterioration mechanism. The results show that both the UCS and p H value of soil decrease with increasing heavy metal concentration. The UCS of Zn~(2+)-Cu~(2+) combined polluted soil is between Zn~(2+) and Cu~(2+) polluted soil at the same total concentration. However, the deterioration rate of combined heavy metal polluted soil is less than the sum of deterioration rate of the two single polluted soils at the same total concentration. In addition, heavy metal cations in polluted soil cause flocculent gels of cosmids to shrink,the micropores to become smaller and the macropores to become larger. The porosity increases slightly with the increase of heavy metal concentration due to decreased pH value. The results from SEM, low field NMR, and pH could explain the dynamic evolution process of soil structure with different heavy metals and concentrations, which provides an experimental basis for mine-site polluted heavy metal treatment technology and the prediction of clayey soil strength deterioration.
  • An enhanced method for estimating snow water equivalent in the central part of the Tibetan Plateau using raster segmentation and eigenvector spatial filtering regression model
    CHENG Qi-shan, CHEN Yu-min, YANG Jia-xin, CHEN Yue-jun, XIONG Zhe-xin, ZHOU An-nan
    2022, 19(09): 2570-2586.
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    Snow water equivalent(SWE) is an important factor reflecting the variability of snow. It is important to estimate SWE based on remote sensing data while taking spatial autocorrelation into account. Based on the segmentation method, the relationship between SWE and environmental factors in the central part of the Tibetan Plateau was explored using the eigenvector spatial filtering(ESF)regression model, and the influence of different factors on the SWE was explored. Three sizes of 16 ×16, 24 × 24 and 32 × 32 were selected to segment raster datasets into blocks. The eigenvectors of the spatial adjacency matrix of the segmented size were selected to be added into the model as spatial factors,and the ESF regression model was constructed for each block in parallel. Results show that precipitation has a great influence on SWE, while surface temperature and NDVI have little influence. Air temperature, elevation and surface temperature have completely different effects in different areas.Compared with the ordinary least square(OLS) linear regression model, geographically weighted regression(GWR) model, spatial lag model(SLM) and spatial error model(SEM), ESF model can eliminate spatial autocorrelation with the highest accuracy. As the segmentation size increases, the complexity of ESF model increases, but the accuracy is improved.
  • Morphological characteristics of rock fissure networks and the main factors affecting their soil nutrients and enzyme activities in Guizhou Province, China
    WANG Mei-quan, GUAN Qing-wei, HUANG Zong-sheng, ZHAO Jia-hao, LIU Zheng-ji, ZHANG Hao, BAO Xun-wen-qian, WANG Lei, YE Yu-qian
    2022, 19(09): 2587-2600.
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    Rock fissures constitute the main habitat type in the karst rocky desertification(KRD) area, but the effects of their network morphology on soil properties remain unknown. To address this, we investigated 46 rock vertical profile plots in Guizhou Province of China and classified their habitats using the morphological characteristics of their fissure networks. The response characteristics of soil nutrients and enzyme activities to the rock fissure morphologies in different rock habitats were discussed, and the main factors affecting soil nutrients and enzyme activities were comprehensively analyzed. Rock fissure networks were divided into three types: Type 1, a random type, with a low dip angle, long trace length, multiple turns, multiple connections, and high density; Type 2, a uniform type,with a moderate dip angle, moderate trace length,fewer turns, fewer connections, and moderate density;and Type 3, an aggregation type, with a high dip angle,short trace length, fewer turns, moderate connections,and low density. Soil nutrient levels and enzyme activities were the highest in Type 1, followed by Types 2 and 3. There were no significant differences between the total phosphorus and available phosphorus content in Types 1-3. The dip angle,fractal dimension, and average trace length were identified as the main factors affecting soil nutrients and enzyme activities, and Type 1 was the most conducive for soil nutrient and enzyme accumulation.The restoration of Type 2 and 3 areas should be emphasized in future research, as these results will help guide vegetation restoration in KRD areas.
  • Quartz luminescence dating of a centennial coastal foredune from Changle in Fujian Province, East China Sea
    JIN Jian-hui, LI Zhi-zhong, LING Zhi-yong, QIU Jun-jie
    2022, 19(09): 2601-2610.
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    The Aeolian foredunes in the southern coast of China are records of paleoenvironmental changes for marine monsoon region. Intensive studies have been conducted to decipher their formation and paleoenvironmental implications in which chronology played a key role. However, robust dating results are still limited due to the scarcity of organic materials for radiocarbon and the limited application of quartz optically stimulated luminescence(OSL). Here, we collected 11 OSL samples and 140 grainsize samples from the Changle section with a thickness of 7 m from a coastal foredune in Fujian Province. The dating results indicated that the section spanned a time period from 0.32±0.04 ka(depth of 700 cm) to 0.18±0.02 ka(depth of 80 cm), after removal of age outliers. According to the OSL ages and sedimentary structural characteristics, the section could be divided into two stages, i.e. the stable accumulation period with an age range of 0.32-0.18 ka from the depth of 700 cm to 80 cm, and the activation period above the depth of 60 cm, at which the dune erosion was retained. The foredune development due to increased transport of dune sediment at the top part of the section was the result of recent human activities.Inside the foredunes, normal cross-bedding was generated by seasonal changes in wind direction.Seasonal changes in the wind direction were the primary cause for various sedimentary bedding within the dunes.
  • Stable isotopes of water as a tracer for revealing spatial and temporal characteristics of groundwater recharge surrounding Qinghai Lake, China
    LI Dong-sheng, CUI Bu-li, ZHAO Yun-duo, ZUO Feng-lin
    2022, 19(09): 2611-2621.
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    Studying spatial and temporal characteristics of regional groundwater recharge will guide the scientific management and sustainable development of regional water resources.This study investigated stable isotopes(δ~(18)O and δ~2 H) of precipitation,groundwater,river water and lake water during 2019-2020 in Qinghai Lake Basin to reveal the spatial and temporal characteristics of groundwater recharge.The local meteoric water line was simulated using ordinary least squares regression(δ~2 H=7.80δ~(18)O+10.60).The local evaporation lines of the river water,lake water and groundwater were simulated asδ~2 H=6.21 δ~(18)O-0.72,δ~2 H=5.73 δ~(18)0-3.60 and δ~2 H=6.59 δ~(18)0+1.76,respectively.The δ~2 H and δ~(18)O of river water and groundwater were in more depleted values due to the recharge by precipitation at high altitudes or precipitation effects,and the δ~2 H and δ~(18)O of the lake water were in more enriched values because of evaporation.The relationship between theδ~2 H and δ~(18)O of groundwater and river water was not significantly different,indicating a strong hydrological connection between the groundwater and river water surrounding Qinghai Lake.Additionally,the maximum values of δ~(18)O and the minimum values of lc-excess of groundwater in most regions were both in August,and the minimum values of δ~(18)O and the maximum values of lc-excess of groundwater in most regions were both in October.Therefore,the groundwater was recharged by soil water with strong evaporation in August and recharged by precipitation at high altitudes in October.The recharge rate of groundwater was relatively fast in areas with large slopes and large hydraulic gradients(e.g.,south of Qinghai Lake),and in areas with strong hydrological connections between the groundwater and river water(e.g.,the Buha River Valley).Those results can provide data support for protection and utilization of water resources in Qinghai Lake Basin,and provide reference for groundwater research in closed lake basins on the Qinghai-Tibet Plateau.
  • Monitoring glaciers in the Chenab basin with SBAS InSAR technology
    DING Yue-kai, LIU Rui, FAN Yi-fei, ZHOU Ling-xiang, JI Qin, ZHANG Hong, XIAO Zuo-lin
    2022, 19(09): 2622-2633.
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    The Chenab basin is located in northwest India and eastern Pakistan. Glaciers in Chenab basin,as local freshwater resources, are very important to the regional ecological environment and development. At the same time, SBAS InSAR can monitor the deformation of the ground for a long time, the monitoring accuracy can reach mm level,and can obtain the time series change of deformation, whcih provides a new idea and method for glacier detection. In this study, the deformation from SBAS InSAR was combined with glacial area data to study the glacial changes in Chenab Basin.Sentinel-1 and Landsat series images were used to obtain the deformation and change in the area of glaciers by SBAS InSAR and the semi-automated method. The results showed that glaciers in the Chenab basin retreated rapidly, especially in the past ten years. The glacier area decreased by 88.05 km2in 1990～2000 and 118.86 km2 in 2000～2010, and the glacier area decreased by 236.01 km2 in 2010～2020, which was the largest rate of change of 9.49%. Moreover, glacial deformation decreased in 2020, and the deformation rate ranged from-146.3mm/a to 119.52 mm/a. Most glaciers had deformation rates between-50 mm/a and 50 mm/a.Influenced by precipitation and temperature, glacial deformation in the Chenab basin started to change in August, the maximum accumulation was 6,828.43mm, and the minimum ablation was-20,656.41 mm.
  • Effects of soil organic matter components and iron aluminum oxides on aggregate stability during vegetation succession in granite red soil eroded areas
    LIN Zhe, HUANG Zhi-gang, LIAO Da-lan, HUANG Wan-xia, HUANG Juan, DENG Yu-song
    2022, 19(09): 2634-2650.
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    Soil aggregates determine the basic structure of soil,and their composition and stability are influenced by the various types of cementitious substances occurring in soil.To explore the main limiting factors of soil aggregation in the process of vegetation succession with granite as the parent material,five stages of vegetation succession in an eroded area were selected:bare land(BL),grassland(GL),grassland shrub transition land(GS),shrubland(SL) and secondary forest(SF).Soil samples were collected to determine the composition and stability of aggregates.The contents of organic and inorganic cementitious substances,including organic matter components and iron aluminum oxides,were determined at five soil aggregate grain levels.The results indicated that the stability of soil aggregates and the>0.25 mm water-stable aggregate content(WR_(0.25)) increased with vegetation succession.Based on the Le Bissonnais(LB) method,the mean weight diameter(MWD) of soil aggregates increased,and the relative dissipation index(RSI) and relative mechanical crushing index(RMI) decreased.The humic acid(HA) and fulvic acid(FA) contents in soil aggregates increased with vegetation succession,and the soil humus content at the SF stage increased by more than 13.54% over the BL level.Upon different vegetation succession stage,the iron and aluminum oxides for the SL and the SF were at a high level,and the contents of free-form iron oxide(Fe_d) and amorphous iron oxide(Fe_o) for BL were high.Correlation analysis indicated that the soil humic degree(PQ) and the contents of amorphous alumina(Al_o) were positively correlated with aggregate stability to varying degrees.Redundancy analysis(RDA) revealed that PQ values of 1-2 mm(PQ_2) and 0.25-0.5 mm(PQ4) aggregates,the contents of Fe_o of bulk soil(Fe_(oB)),>2 mm(Fe_(o1)),1-2 mm(Fe_(o2)),and<0.25 mm(Fe_(o5)) aggregates,and the contents of Al_o of>2 mm(Al_(o1)) aggregates could explain 99.4% of the changes in soil aggregate stability at different vegetation succession stages.Al_(o1) had a contribution rate of 71.2% and is the key factor for improving the stability of soil aggregates.
  • Spatial patterns of leaf nitrogen and phosphorus stoichiometry across southeast to central Tibet
    WANG Wei, ZHAO Jia-min, XING Zhen
    2022, 19(09): 2651-2663.
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    Leaf N and P stoichiometry in terrestrial ecosystems has been widely investigated in recent years owing to the importance of these elements in improving the predicted vegetation responses to global changes. The vertical distribution of leaf N and P stoichiometry has attracted increasing attention because of the dramatic changes in environmental factors at regional scales. However, the characteristics of leaf N and P stoichiometry in the southeast Qinghai–Tibet plateau(SET) are not clear, although this area is sensitive to global change. Here, we analyzed the leaf N and P concentrations in dominant plant species on natural altitudinal gradients on the Duoxiongla(DXL), Sejila(SJL), Mila(ML), and Gangbala(GBL) mountains across the SET all the way to central Tibet. Our results showed that the leaf N concentrations were comparable among the regions,whereas the leaf P concentrations dramatically decreased from SET to central Tibet(CT). The leaf N concentrations were 23.6, 21.3, 20.8, and 22.4 g kg~(-1),and the leaf P concentrations were 2.40, 2.49, 1.94,and 1.59 g kg~(-1) on the SJL, DXL, ML and GBL mountains, respectively. The leaf N/P ratios on the DXL, SJL, ML, and GBL mountains were 8.81, 10.3,11.2, and 14.2, respectively. Considering the increasing trend of the leaf N/P ratio from southeast Qinghai–Tibet plateau to central Tibet, N limitation might widely exist in well vegetated ecosystems in the Qinghai–Tibet plateau.
  • Influence of topography, soil properties and plant community on the biomass of Abies georgei var. smithii seedlings in Southeast Tibet
    ZHANG Xin-sheng, ZHOU Chen-ni, LU Jie
    2022, 19(09): 2664-2677.
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    Biomass of seedlings at different developing stages of growth is important information for studying the response of species to site conditions.The objectives of this study was to explore the distribution characteristics of AGB(above-ground biomass) and BGB(below-ground biomass) of Abies georgei var. smithii seedlings of different ages, and investigate the effects of topography(slope aspect,altitude),plant community characteristics(crown density, species diversity, etc.), and soil properties(soil physical and chemical properties) on the biomass and its allocation. Seedlings in five age classes(1–2, 3–4, 5–6, 7–8, and 9–10 years old) were collected by full excavation from 6 elevations(3800 m,3900 m, 4000 m, 4100 m, 4200 m, 4300 m) on the north and south slopes of Sejila Mountain in Tibet. 15seedlings of each age class were investigated at one altitude. The individual effects of seedling age(SA)and the interaction effects of SA, slope aspect(SL),and elevation(EG), namely, SL×EG, SL×SA, EG×SA,and SL×EG×SA, had significant effects on the AGB of the seedlings(p<0.05), whereas BGB was only significantly affected by SA(p<0.001). The AGB and BGB of the seedlings showed a binomial growth trend with the increase in seedling age, and had an allometric relationship at different elevations, α(allometric exponential) varied from 0.913 to 1.046 in the northern slope, and from 1.004 to 1.268 in the southern slope. The biomass of seedlings on the northern slope was remarkably affected by stand factors, with a contribution rate of 47.8%, whereas that on the southern slope was considerably affected by soil factors with a contribution rate of 53.2%. The results showed that age was the most important factor affecting seedling biomass. The allometric pattern of seedling biomass was relatively stable, but in a highaltitude habitat, A. georgei var. smithii seedlings increased the input of BGB. Understanding seedling biomass allocation and its influencing factors is useful for evaluating plants' ability to acquire resources and survival strategies for adaptation to the environment in Tibet Plateau.
  • Assessing the impacts of climate change and anthropogenic activities on vegetation in southwest China
    ZHANG Yu-xin, LIU Qin, WANG Yu-kuan, HUANG Jing-han
    2022, 19(09): 2678-2692.
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    The topography and geomorphology of southwest China are complex, and the intensity of human activities not balanced. The impact of climate change and anthropogenic activities on vegetation shows temporal and spatial differences. Therefore, we used normalized difference vegetation index(NDVI)to analyze the impact of climate change and anthropogenic activities on vegetation in four provinces and municipality in the southwest China from 2000 to 2015. The results showed that(1) NDVI increased 0.004–0.005/yr during this period. About 57.74%–69.09% of the area with significant changes was found to be primarily affected by anthropogenic activities during all four seasons and the growing season, while 6.05%–10.74% and 5.09%–9.77% of the area was affected by temperature and precipitation,respectively.(2) The impact of temperature and precipitation changes were spatially heterogeneous.Temperature had a positive impact during spring and summer in the northwestern region. Furthermore,NDVI was positively affected in the southwestern and eastern regions, while the western region was negatively affected by precipitation. Summer temperatures and precipitation had the greatest impact throughout the year.(3) Returning farmland to forests and improving agricultural management demonstrated positive impacts of anthropogenic activities on the vegetation, while areas with significant negative impacts due to anthropogenic activities were located near the provincial capitals of the four provinces and municipality. This study can provide a scientific basis for accurately identifying key ecological protection areas in Southwest China.
  • Liveability experience of mountain-base residents: the case of Idi-Ori-Shasha Mountain, Ibadan, Nigeria
    Taiwo Oladapo BABALOLA, Abubakar Alhaji AHMED, Ayobami Abayomi POPOOLA, Tolulope Mary ADEDEJI, Olajumoke Ololade TUNJI-ADEPOJU
    2022, 19(09): 2693-2702.
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    The increasing influx of people to mountain base environments has opened up the area to a myriad of problems that threaten the liveability of the residents and the sustainability of the environment. Yet, sufficient empirical investigations have not looked at the particular issues that threaten their liveability experience. Using the case of Idi-OriShasha mountain, this study examined the condition of informal urbanization at the mountain-base and equally investigated residents' living experiences. We conducted questionnaire survey with closed and open-ended questions to collect data from 65 out of 533 houses within a buffer of 250 m from the mountain and retrieved 50 completed householdhead survey. The results revealed that majority of the residents were not satisfied living at the mountainbase because of the inadequate facilities that have contributed to their current living conditions. Also,mountain-base residents are liable to many liveability threats such as noise pollution, sleeplessness,building/wall cracks, destructive erosion, and water inaccessibility. The study recommends adequate infrastructural provision intervention in the area in order to upscale liveability dimensions and general residents' living conditions. Conversely, similar studies could be conducted elsewhere for validation and comparison of findings.
  • Stability analysis of complex terrain slope based on multi-source point cloud fusion
    ZAN Wen-bo, ZHANG Wen-jie, WANG Ning, ZHAO Chun-chen, YANG Qian, LI Hao
    2022, 19(09): 2703-2714.
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    Numerical modelling is a common routine for slope stability analysis in the complex terrain, and the accuracy of topographic survey has a great impact on the results. In this study, a combination of unmanned aerial vehicle(UAV) photogrammetry and 3D laser scanning technique was first proposed to establish a high-precision digital elevation model(DEM), which could be accurate to 0.2 m, fulfilling the engineering requirements. Then, a series of 3D/2D finite element models(FEM) were constituted on the basis of DEM to investigate the slope stability in the complex terrain. The results indicate that the deformation of complex terrain slope is chiefly triggered by compression-shear failure and the failure zones are mostly distributed on the middle-upper part and the scarp. Furthermore, the complex terrain slope is divided into concave, convex, concave-convex and convex-concave slope according to the topographical curvature, and the factor of safety(FOS) is as follows:the maximum value 1.8504 for the concave-convex slope, the minimum value 1.1129 for the convexconcave slope, and the median for either concave or convex slope. The inflection points and curvature of the slope jointly determine the shape of nonlinear slope, dominating the morphological effect on the slope stability, so the rational use of section morphological effect will be conducive to the overall stability of the slope. For four representative slopes,the plastic deformation first emerges into the middle,then progressively develops to the upper, and finally forms the connected failure zones.
  • Flow characteristics in curved open channel with partial suspended vegetation
    ZHANG Qiao-ling, JING He-fang, LI Chun-guang, WANG Wei-hong, ZHANG Wen-sheng
    2022, 19(09): 2715-2728.
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    Suspended vegetation in open channels such as natural river, lake, reservoir usually affect the flow structure, causing the change of the water environment, sediment transport, bed deformation.In order to study the water flow behavior in curved open channels under the influence of suspended vegetation, experiments were conducted in a Ushaped flume with 180° bend where the suspended vegetation substituted by cylindrical glass rods were partially placed. The particle image velocimeter(PIV)system was employed to measure the flow velocities of various cases with different vegetation arrangements and roots length. Comparison and analysis were conducted for measured data, such as water level,velocity, head loss, Reynolds stress, and turbulence kinetic energy(TKE) to obtain certain general rules of water flow in open curved channels with suspended vegetation. It can be found from the measured data that the water level and the head loss in the vegetation area are closely related to the arrangements of the suspended vegetation. Furthermore, the drag force of the vegetation can not only lead to smaller increments of longitudinal TKE above the vegetation tail than that below it, but also lead to the flow velocities in vegetation area much smaller than areas without vegetation. In addition, suspended vegetation weakens the vortex strength near the water surface and increases the vortex strength below the vegetation tail, and the flow velocity in the vegetation area has a close relationship with the suspended vegetation length in the water. Therefore, it can be concluded that the reasonable arrangements of suspended vegetation group in curved open channel can protect the concave bank from being scoured, and protect the convex bank from being deposited.
  • Geomechanics model test and numerical simulation of 2G-NPR bolt support effect in an active fault tunnel
    REN Shu-lin, HE Man-chao, LIN Wei-jun, ZHANG Teng-wu, TAO Zhi-gang
    2022, 19(09): 2729-2741.
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    Active faults are a common adverse geological phenomenon that can occur during tunnel excavation and has a very negative impact on the construction and operation of the tunnel. In this paper, the grade IV rock surrounding the cross-fault tunnel with poor geological conditions has been chosen for the study. The support capacity of 2nd Generation-Negative Poisson's Ratio(2G-NPR) bolt in an active fault tunnel has been carried out on the basis of relevant results obtained from the geomechanical model test and numerical investigations of failure model for existing unsupported fault tunnel.The investigation shows that surrounding rock of the tunnel is prone to shear deformation and crack formation along the fault, as a result, the rock mass on the upper part of the fault slips as a whole.Furthermore, small-scale deformation and loss of blocks are observed around the tunnel; however, the 2G-NPR bolt support is found to be helpful in keeping the overall tunnel intact without any damage and instability. Due to the blocking effect of fault, the stress of the surrounding rock on the upper and lower parts of the fault is significantly different, and the stress at the left shoulder of the tunnel is greater than that at the right shoulder. The asymmetrical arrangement of 2G-NPR bolts can effectively control the asymmetric deformation and instability of the surrounding rock. The present numerical scheme is in good agreement with the model test results, and can reasonably reflect the stress and displacement characteristics of the surrounding rock of the tunnel.In comparison to unsupported and ordinary PR(Poisson's Ratio) bolt support, 2G-NPR bolt can effectively limit the fault slip and control the stability of the surrounding rock of the fault tunnel. The research findings may serve as a guideline for the use of 2G-NPR bolts in fault tunnel support engineering.