Showing papers in "Journal of Mountain Science in 2016"

Mapping the vegetation distribution of the permafrost zone on the Qinghai-Tibet Plateau

Abstract: In this paper, an updated vegetation map of the permafrost zone in the Qinghai-Tibet Plateau (QTP) was delineated. The vegetation map model was extracted from vegetation sampling with remote sensing (RS) datasets by decision tree method. The spatial resolution of the map is 1 km×1 km, and in it the alpine swamp meadow is firstly distinguished in the high-altitude areas. The results showed that the total vegetated area in the permafrost zone of the QTP is 1,201,751 km2. In the vegetated region, 50,260 km2 is the areas of alpine swamp meadow, 583,909 km2 for alpine meadow, 332,754 km2 for alpine steppe, and 234,828 km2 for alpine desert. This updated vegetation map in permafrost zone of QTP could provide more details about the distribution of alpine vegetation types for studying the vegetation mechanisms in the land surface processes of high-altitude areas.

Review of studies on land use and land cover change in Nepal

Abstract: Land use and land cover (LULC) in Nepal has undergone constant changeover thepast few decades due to major changes caused by anthropogenic and natural factors and their impacts on the national and regional environment and climate. This comprehensive review of past and present studies ofland use and land cover change (LUCC) in Nepal concentrates on cropland, grassland, forest, snow/glacier cover and urban areas. While most small area studies have gathereddata from different sources and research over a short period, across large areas most historical studies have been based on aerial photographs such as the Land Resource Mapping Project in1986. The recent trend in studies in Nepal is to focus on new concepts and techniques to analyze LULC status on the basis of satellite imagery, with the help of geographic information system and remote sensing tools. Studies based on historical documents, and historical and recent spatial data on LULC,have clearly shown an increase in cropland areas in Nepal, and present results indicating different rates and magnitudes. A decrease in forest and snow/glacier coverage is reported in most studies. Little information is available on grassland and urban areas frompast research. The unprecedented rate of urbanization in Nepal has led to significant urban land changes overthe past 30 years. Meanwhile,long term historical LUCC research in Nepal is required for extensive work on spatially explicit reconstructions on the basis of historical and primary data collection, including LULC archives and drivers for future change.

Anthropogenic disturbances and their impact on vegetation in Western Himalaya, India

Abstract: The present study assesses anthropogenic disturbances and their impacts on the vegetation in Western Himalaya, India on the basis of various disturbance parameters such as density, Total Basal Cover (TBC) of cut stumps, lopping percentage and grazing intensities. On the basis of canopy cover and frequency of disturbances (%), the studied forests were divided into highly disturbed (HD), moderately disturbed (MD) and least disturbed (LD) categories. The HD forests had the lowest canopy cover, lowest density and lowest TBC and the LD had the highest canopy cover, highest density and highest TBC. The MD forests occupied the intermediate position with respect to these parameters. Species richness was least in HD forests, highest in one of the MD forests while LD forest occupied an intermediate position. The percentage of regenerating species was lowest (54%) in HD and highest (72%) in MD. The density of seedlings and saplings was higher in one of the MD forests as compared to HD and LD. We concluded that the moderate disturbances do not affect the vegetation adversely; however the increased degree of disturbance causes loss in plant diversity; affects regeneration and changes community characteristics. Construction of hydroelectric projects at various places in the study area was found to be one of the most important sources of anthropogenic disturbances in addition to the routine anthropogenic disturbances like grazing, fuelwood collection and fodder extraction. If all proposed dams in the Indian Himalaya are constructed combined with weak national environmental impact assessment and implementation, it will result in a significant loss of species. Therefore, various agents of disturbances should be evaluated in cumulative manner and any developmental activities such as hydropower projects, which trigger various natural and anthropogenic disturbances, should be combined with proper cumulative environmental impact assessment and effective implementation to minimise the anticipated loss of vegetation.

Landslide susceptibility assessment of the region affected by the 25 April 2015 Gorkha earthquake of Nepal

Abstract: Nepal was hit by a 7.8 magnitude earthquake on 25th April, 2015. The main shock and many large aftershocks generated a large number of coseismic landslips in central Nepal. We have developed a landslide susceptibility map of the affected region based on the coseismic landslides collected from remotely sensed data and fieldwork, using bivariate statistical model with different landslide causative factors. From the investigation, it is observed that most of the coseismic landslides are independent of previous landslides. Out of 3,716 mapped landslides, we used 80% of them to develop a susceptibility map and the remaining 20% were taken for validating the model. A total of 11 different landslide-influencing parameters were considered. These include slope gradient, slope aspect, plan curvature, elevation, relative relief, Peak Ground Acceleration (PGA), distance from epicenters of the mainshock and major aftershocks, lithology, distance of the landslide from the fault, fold, and drainage line. The success rate of 87.66% and the prediction rate of 86.87% indicate that the model is in good agreement between the developed susceptibility map and the existing landslides data. PGA, lithology, slope angle and elevation have played a major role in triggering the coseismic mass movements. This susceptibility map can be used for relocating the people in the affected regions as well as for future land development.

Empirical assessment of adaptation to climate change impacts of mountain households: development and application of an Adaptation Capability Index

Abstract: The present study proposes an index to assess the potential for adaptation to climate change for households in the mountainous regions. The index provides a realistic approach to recognize social and natural factors which contribute to successful adaptation and addresses several household functions, such as social networking, livelihood strategy, adjustment strategies, resource availability and accessibility. The proposed Adaptation Capability Index (ACI) is analytically defined, mathematically formulated and field tested on mountainous households in urban and semi-urban regions of the Uttarakhand Himalaya in India. To gather data on the topic relevant to the ACI, a household scale questionnaire was developed and administered to 120 heads of households through face-to-face interviews. The results highlight higher adaptive capability of urban households and low adaptation capacity of rural households due to poor farm productivity, low accessibility and availability of resources and technological input. Future programs and policies must include and implement regulations to remedy attributive factors responsible for higher adaptation. This paper may be applicable to other mountainous regions and may provide insights for effective adaptation strategies to climate change.

Seismic damage of mountain tunnels during the 5.12 Wenchuan earthquake

Abstract: A number of mountain tunnels suffered significant damage to various extent during the 2008 Wenchuan earthquake in China. Damage ranging from small to heavy cracking was observed both at the portal and inside the tunnels, while some sections close to the faults completely collapsed. A summary of qualitative data collected from reports and papers is presented regarding the behavior of the 55 mountain tunnels near the epicenter during the earthquake. Based on the seismic investigation and data collection of mountain tunnels, the tunnel damage is classified into six most common damage models involving cracking, spalling, shear failure, dislocation, pavement uplift and collapse. Detailed study and discussion are then carried out on the damage models. In order to examine the influencing factors of the damage magnitude of the mountain tunnels, the correlations between epicentral distance, earthquake intensity, overburden depth, geological condition and damage levels are analyzed. The relationships between earthquake parameters and different damage models are developed and discussed. Also, suggestions are provided to improve the seismic resistance of mountain tunnels.

The influence of elevation on soil properties and forest litter in the Siliceous Moncayo Massif, SW Europe

Abstract: Understanding the effects of elevation and related factors (climate, vegetation) on the physical and chemical soil properties can help to predict changes in response to future climate or afforestation forcings. This work aims to contribute to the knowledge of soil evolution and the classification of forest soils in relation to elevation in the montane stage, with special attention to podzolization and humus forms. The northern flank of the Moncayo Massif (Iberian Range, SW Europe) provides a unique opportunity to study a forest soils catena within a consistent quartzitic parent material over a relatively steep elevation gradient. With increasing elevation, pH, base saturation, exchangeable potassium, and fine silt-sized particles decrease significantly, while organic matter, the C/N ratio, soil aggregate stability, water repellency and coarse sand-sized particles increase significantly. The soil profiles shared a set of properties in all horizons: loamy-skeletal particle-size, extreme acidity (pH-H2O<5.6) and low base saturation (<50%). The most prevalent soil forming processes in the catena include topsoil organic matter accumulation and even podzolization, which increases with elevation. From the upper to lower landscape positions of wooded montane stage of the Moncayo Massif, mull-moder-mor humus and an Umbrisol-Cambisol-Podzol soil unit sequences were found.

Dynamics of land use change in a mining area: a case study of Nadowli District, Ghana

Abstract: In a developing country like Ghana, the study of land use and land cover change (LULCC) based on satellite imageries still remains a challenge due to cost, resolution and availability with less skilled man power. Existing researches are skewed towards the southerly part of Ghana thereby leaving the Northern sectors uncovered. The maximum likelihood classification (MLC) algorithm was employed for the LULCC between 2000 and 2014 in Nadowli: an area characterized by an upsurge in mining in the Northern belt of Ghana. A spatial-social approach was utilized combining both satellite imagery and socio economic data. Land use transition matrix, land use integrated index/degree indices was used to depict the characters of the change. A semi structured interview, pair wise ranking and key informant interviews were used to correlate the socio economic impact of the different LULC. Overall changes in the landscape showed an increase in bare ground by 19.22%, open savannah by 16.8% whereas closed savanna decreased by 50%. Land use change matrix showed increasing trends of bare ground at the expense of vegetation. The integrated land use index highlighted the bare ground and built up areas rising with a decreasing closed vegetation woodlot. Large farm size are shrinking whiles majority of the people view mining as the main socio economic activity affecting the environment and the reduction in vegetation. This study therefore provides a strategic guide and a baseline data for land use policy actors in the Northern belt of Ghana. This will aid in developing models for future land use change implications in surrounding areas where mining is on the rise.

Landslide risk perception and communication for disaster risk management in mountain areas of developing countries: a Mexican foretaste

Abstract: The increasing impact of disasters at local, national, regional and global scales in recent decades has provided enough evidence to urgently direct attention towards the necessity of disaster risk reduction and management, and this requires knowledge. Knowledge without communication is barren, and to communicate the risk of disaster it is necessary to understand the perception of the people at risk. In particular, this paper deals with the necessity to delineate strategies of risk communication in pursuance of risk knowledge as a core of disaster risk reduction and management, especially in mountain areas of developing countries. To portray this issue, an analysis of landslide risk perception in terms of experience, landslide risk awareness, exposure, preparedness, and risk communication and trust was undertaken in the municipality of Teziutlan, Puebla, Mexico, an area that has been affected for several decades by episodes of mass movement. Analysis of the responses to a risk perception questionnaire has offered valuable insights in terms of the information and knowledge most required by the people living in the area of interest, in order to devise a realistic and functional strategy to communicate the risk of a landslide disaster. This includes better understanding of controlling factors and drivers of this risk, and the establishment of potential trusted sources of risk communication. Beyond considering practical matters of risk assessment and management, risk perception and communication can increase the resilience of vulnerable people, and can enhance capacity building for present and future generations.

Long-range precipitation forecasts using paleoclimate reconstructions in the western United States

Abstract: Long-range precipitation forecasts are useful when managing water supplies. Oceanic-atmospheric oscillations have been shown to influence precipitation. Due to a longer cycle of some of the oscillations, a short instrumental record is a limitation in using them for long-range precipitation forecasts. The influence of oscillations over precipitation is observable within paleoclimate reconstructions; however, there have been no attempts to utilize these reconstructions in precipitation forecasting. A data-driven model, KStar, is used for obtaining long-range precipitation forecasts by extending the period of record through the use of reconstructions of oscillations. KStar is a nearest neighbor algorithm with an entropy-based distance function. Oceanic-atmospheric oscillation reconstructions include the El Nino-Southern Oscillation (ENSO), the Pacific Decadal Oscillation (PDO), the North Atlantic Oscillation (NAO), and the Atlantic Multi-decadal Oscillation (AMO). Precipitation is forecasted for 20 climate divisions in the western United States. A 10-year moving average is applied to aid in the identification of oscillation phases. A lead time approach is used to simulate a one-year forecast, with a 10-fold cross-validation technique to test the models. Reconstructions are used from 1658-1899, while the observed record is used from 1900-2007. The model is evaluated using mean absolute error (MAE), root mean squared error (RMSE), RMSE-observations standard deviation ratio (RSR), Pearson’s correlation coefficient (R), Nash-Sutcliffe coefficient of efficiency (NSE), and linear error in probability space (LEPS) skill score (SK).The role of individual and coupled oscillations is evaluated by dropping oscillations in the model. The results indicate ‘good’ precipitation estimates using the KStar model. This modeling technique is expected to be useful for long-term water resources planning and management.

Particle breakage and the mobilized drained shear strengths of sand

Abstract: This paper presents particle breakage and the mobilized drained shear strengths of sand with the purpose of clarifying the influence of particle breakage on the mobilized shear strengths of sand. Several drained triaxial tests were carried out on Silica sand No.5 under 3 MPa confining pressure to produce the pre-crushed sands in simulating the high-pressure shear process on soil to result in particle breakage, and then the pre-crushed sands were re-sheared in series of drained triaxial tests to investigate the mobilized strengths of the pre-crushed sands in detecting the influence of particle breakage. It was found that, by deteriorating strain-stress behavior, particle breakage resulted in change of stress-dilatancy behavior in translation and rotation of the relation of the dilatancy factor and the effective principal stress ratio. For a given initial void ratio, particle breakage resulted in impairment of dilatancy behavior of soil to be more contractive in deterioration of the mobilized friction angle and the mobilized dilatancy angle and reduction of void ratio. However, particle breakage resulted in increase of the mobilized basic friction angle especially before failure. In addition, the influence of particle breakage on the mobilized strengths was revealed to be influenced by the shear stress-strain state.

Characteristics of landslide in Koshi River Basin, Central Himalaya

Abstract: Koshi River basin, which lies in the Central Himalayas with an area of 71,500 km(2), is an important trans-boundary river basin shared by China, Nepal and India. Yet, landslide-prone areas are all located in China and Nepal, imposing alarming risks of widespread damages to property and loss of human life in both countries. Against this backdrop, this research, by utilizing remote sensing images and topographic maps, has identified a total number of 6877 landslides for the past 23 years and further examined their distribution, characteristics and causes. Analysis shows that the two-step topography in the Himalayan region has a considerable effect on the distribution of landslides in this area. Dense distribution of landslides falls into two regions: the Lesser Himalaya (mostly small and medium size landslides in east-west direction) and the Transition Belt (mostly large and medium size landslides along the river in north-south direction). Landslides decrease against the elevation while the southern slopes of the Himalayas have more landslides than its northern side. Change analysis was carried out by comparing landslide distribution data of 1992, 2010 and 2015 in the Koshi River basin. The rainfall-induced landslides, usually small and shallow and occurring more frequently in regions with an elevation lower than 1000m, are common in the south and south-east slopes due to heavy precipitation in the region, and are more prone to the slope gradient of 20 degrees similar to 30 degrees. Most of them are distributed in Proterozoic stratum (Pt-3 epsilon, Pt-3 and Pt2-3) and Quaternary stratum. While for earthquake-induced landslides, they are more prone to higher elevations (2000 similar to 3000 m) and steeper slopes (40 degrees similar to 50 degrees).

Experimental investigation on the relevance of mechanical properties and porosity of sandstone after hydrochemical erosion

Abstract: Under the effect of chemical etching, the macroscopic mechanical properties, mesoscopic structure, mineral content, and porosity of rocks undergo significant changes, which can lead to the geological disasters; thus, an understanding of changes in the microscopic and macroscopic structure of rocks after chemical etching is crucial. In this study, uniaxial mechanical tests and nuclear magnetic resonance (NMR) spectroscopy were carried out on sandstone samples that had been previously subjected to chemical erosion under different pH values. The aim was to study changes in properties and mechanical characteristics, including deformation and strength characteristics, of the rock, and microscopic pore variation characteristics, and to perform preliminary studies of the chemical corrosion mechanism. Results show that different chemical solutions have a significant influence on the uniaxial compressive strength, the axial strain corresponding to the peak axial stress, elastic modulus, etc. With the passage of time, porosity increases gradually with exposure to different chemical solutions, and exposure to chemical solutions results in large changes in the NMR T2 curve and T2 spectrum area. Sandstone exposed to different chemical solutions exhibits different corrosion mechanisms; the root cause is the change of mineral.

Deep-seated large-scale toppling failure in metamorphic rocks: a case study of the Erguxi slope in southwest China

Abstract: Deep-seated large-scale toppling failure presents unique challenges in the study of natural slope deformation process in mountainous regions. An active deep-seated toppling process was identified in the Erguxi slope located in southwest China, which affected a large area and damaged critical transportation infrastructure with the volume of the deforming rock mass exceeding 24×106 m3. It poses significant risks to the downstream Shiziping Hydropower Station by damming the Zagunao River. Field investigation and monitoring results indicate that the deformation of the Erguxi slope is in the advanced stage of deep-seated toppling process, with the formation of a disturbed belt but no identifiable master failure surface. It was postulated that the alternating tensile and shear strength associated with the hard/soft laminated rock strata of metasandstone and phyllite layers preclude the development of either a tensile or shear failure surface, which resulted in the continuous deformation and displacement without a catastrophic mass movement. The slope movement is in close association with the unfavorable geological conditions of the study area in addition to the construction of transportation infrastructure and the increase of the reservoir level. On the basis of the mechanism and intensity of the ongoing toppling deformation, a qualitative grading system was proposed to describe the toppling process and to evaluate the slope stability. This paper summarized the field observation and monitoring data on the toppling deformation for better characterizing its effect on the stability of the Erguxi slope. The qualitative grading system intends to provide a basis for quantitative study of large-scale deep-seated toppling process in metamorphic rocks.

Spatial assessment of forest cover and land-use changes in the Hindu-Kush mountain ranges of northern Pakistan

Abstract: Anthropogenic activities and natural processes are continuously altering the mountainous environment through deforestation, forest degradation and other land-use changes. It is highly important to assess, monitor and forecast forest cover and other land-use changes for the protection and conservation of mountainous environment. The present study deals with the assessment of forest cover and other land-use changes in the mountain ranges of Dir Kohistan in northern Pakistan, using high resolution multi-temporal SPOT-5 satellite images. The SPOT-5 satellite images of years 2004, 2007, 2010 and 2013 were acquired and classified into land-cover units. In addition, forest cover and land-use change detection map was developed using the classified maps of 2004 and2013.The classified maps were verified through random field samples and Google Earth imagery (Quick birds and SPOT-5). The results showed that during the period 2004 to 2013 the area of forest land decreased by 6.4%, however, area of range land and agriculture land have increased by 22.1% and 2.9%, respectively. Similarly, barren land increased by 1.1%, whereas, area of snow cover/glacier is significantly decreased by 21.3%. The findings from the study will be useful for forestry and landscape planning and can be utilized by the local, provincial and national forest departments; and REDD+ policy makers in Pakistan.

Experimental study of motion characteristics of rock slopes with weak intercalation under seismic excitation

Abstract: In order to investigate the effect of a weak intercalation on slope stability, a large-scale shaking table model test was conducted to study the dynamic response of rock slope models with weak intercalation. The dynamic response of the prototype slopes were studied in laboratory with the consideration of law of similitude. The initiation failure was observed in the rock slope model with a counter-tilt thin-weak intercalation firstly, not in the slope model with a horizontal thin-weak intercalation. Furthermore, it was interesting that the fracture site is shifted from crest top to the slope surface near the weak intercalation, which is different with the location of failure position in a normal layered slope. We also discussed the effect of the dip angle and the thickness of weak intercalation on the failure mechanism and instability mode of the layered rock slope. From the experimental result, it was noted that the stability of the slope with a counter-tilt weak intercalation could be worse than that of the other slopes under seismic excitation. The findings showed the difference of failure in slopes with a horizontal and counter weak intercalation, and implicated the further evaluation of failure of layered slopes caused by seismic loads.

The characteristics of rill development and their effects on runoff and sediment yield under different slope gradients

Abstract: Rill formation is the predominant erosion process in slope land in the Loess Plateau, China. This study was conducted to investigate rill erosion characteristics and their effects on runoff and sediment yielding processes under different slope gradients at a rate of 10°, 15°, 20° and 25° with rainfall intensity of 1.5 mm min-1 in a laboratory setting. Results revealed that mean rill depth and rill density has a positive interrelation to the slope gradient. To the contrary, width-depth ratio and distance of the longest rill to the top of the slope negatively related to slope gradient. All these suggested that increasing slope steepness could enhance rill headward erosion, vertical erosion and the fragmentation of the slope surface. Furthermore, total erosion tended to approach a stable maximum value with increasing slope, which implied that there is probably a threshold slope gradient where soil erosion begins to weaken. At the same time, the correlation analysis showed that there was a close connection between slope gradient and the various indices of soil erosion: the correlation coefficients of slope gradient with maximal rill depth, number of rills and the distance of the longest rill from the top of the slope were 0.98, 0.97 and -0.98, respectively, indicating that slope gradient is the major factor of affecting the development of rills. Furthermore, runoff was not sensitive to slope gradient and rill formation in this study. Sediment concentration, however, is positively related to slope gradient and rill formation, the sediment concentrations increased rapidly after rill initiation, especially. These results may be essential for soil loss prediction.

Rangeland degradation assessment in Kyrgyzstan: vegetation and soils as indicators of grazing pressure in Naryn Oblast

Abstract: Rangelands occupy more than 80% of the agricultural land in Kyrgyzstan. At least 30% of Kyrgyz pasture areas are considered to be subject to vegetation and soil degradation. Since animal husbandry is the economic basis to sustain people's livelihoods, rangeland degradation presents a threat for the majority of the population. We present for the first time an ecological assessment of different pasture types in a remote area of the Naryn Oblast, using vegetation and soils as indicators of rangeland conditions. We analysed the current degree of utilization (grazing pressure), the amount of biomass, soil samples, and vegetation data, using cluster analysis as well as ordination techniques. Winter pastures (kyshtoo) are characterized by higher pH values (average of 7.27) and lower organic matter contents (average of 12.83%) compared to summer pastures (dzailoo) with average pH values of 6.03 and average organic matter contents of 21.05%. Additionally, summer pastures show higher above-ground biomass, and higher species richness and diversity. Our results support the hypothesis that winter pastures, which are located near settlements, suffer from over-utilisation, while the more distant summer pastures are subjected to much lower grazing pressure.

Trends in major and minor meteorological variables and their influence on reference evapotranspiration for mid Himalayan region at east Sikkim, India

Abstract: Estimation of evapotranspiration (ET) for mountain ecosystem is of absolute importance since it servesas an important component in balancing the hydrologic cycle. The present study evaluates the performance of original and location specific calibrated Hargreaves equation (HARG) with the estimates of Food and Agricultural Organization (FAO) Penman Monteith (PM) method for higher altitudes in East Sikkim, India.The results show that the uncalibrated HARG model underestimates ET0 by 0.35 mm day-1 whereas the results are significantly improved by regional calibration of the model.In addition, this paperalso presents the variability in the trajectory associated with the climatic variables with the changing climate in the study site. Non-parametric Mann-Kendall (MK) test was used to investigate and understand the mean monthly trend of eight climatic parameters including reference evapotranspiration (ET0) for the period of 1985 - 2009. Trend of ET0 was estimated for the calculations done by FAO PM equation. The outcomes of the trend analysis show significant increasing (p ≤ 0.05) trend represented by higher Z-values, through MK test, for net radiation (Rn), maximum temperature (Tmax) and minimum temperature (Tmin), especially in the first months of the year. Whereas, significant (0.01 ≥ p ≤ 0.05) decreasing trend in vapor pressure deficit (VPD) and precipitation (P) is observed throughout the year. Declining trend in sunshine duration, VPD and ET0 is found in spring (March - May) and monsoon (June – November) season. The result displays significant (0.01≤p ≤ 0.05) decreasing ET0 trend between (June - December) except in July, exhibiting the positive relation with VPD followed by sunshine duration at the station.Overall, the study emphasizes the importance of trend analysis of ET0 and other climatic variables for efficient planning and managing the agricultural practices, in identifying the changes in the meteorological parameters and to accurately assess the hydrologic water balance of the hilly regions.

Variations of bacterial and fungal communities along a primary successional chronosequence in the Hailuogou glacier retreat area (Gongga Mountain, SW China)

Abstract: New terrestrial habitats have emerged and a primary succession has developed in the retreat area (29A degrees 34'N, 102A degrees 00'E, 2951-2886 m) after the retreat of the Hailuogou glacier. To investigate soil microbial changes along the primary successional chronosequence, mixed soil samples were collected at six sites at different ages (2 young sites, 2 mid-aged sites, and 2 old sites). The RNA was extracted and amplified. Bacterial 16S rRNA and fungal 18S rRNA were analyzed using high-throughput 454 pyrosequencing analysis. Overall, pyrosequencing showed that Proteobacteria, Acidobacteria, Bacteroidetes and Actinobacteria were the main bacterial phyla, and the fungal communities were strongly dominated by the phyla Ascomycota and Basidiomycota in the retreat area. The Shannon diversity index (H-shannon) of bacteria was 6.5-7.9, and that of fungi was 2.2-4.1 in these sites. For the bacterial communities, diversity and evenness values were highest on the mid-age sites and were relatively low on the young and old sites. A similar trend was observed for the fungal communities. In contrast, soil properties showed significant linear distributional trends (increase or decrease) with the age of the site. Combining the linear change patterns of soil properties, the highest values of bacterial and fungal evenness and diversity in the mid-aged sites indicated that there was less environmental stress and more niches for microbial communities in the middle successional stage compare with other stages. In addition, our analysis showed that microbial communities were the main drivers that build a soil organic matter pool to expedite pedogenesis for ecosystem succession. This primary succession in the Hailuogou glacier retreat area is developing rapidly compared with that in other glacier retreats.

Soil organic carbon contents, aggregate stability, and humic acid composition in different alpine grasslands in Qinghai-Tibet Plateau

Abstract: Alpine grassland soils on Qinghai-Tibet Plateau store approximately 33.5 Pg of organic carbon (C) at 0–0.75 m depth and play an important role in the global carbon cycle. We investigated soil organic C (SOC), water-soluble organic C (WSOC), easily oxidizable organic C (EOC), humic C fractions, aggregate-associated C, aggregate stability, and humic acid (HA) composition along an east-west transect across Qinghai-Tibet Plateau, and explored their spatial patterns and controlling factors. The contents of SOC, WSOC, EOC, humic C fractions and aggregate-associated C, the proportions of macro-aggregates (2-0.25) and micro-aggregates (0.25-0.053 mm), and the aggregate stability indices all increased in the order alpine desert < alpine steppe < alpine meadow. The alkyl C, O-alkyl C, and aliphatic C/aromatic C ratio of HA increased as alpine desert < alpine meadow < alpine steppe, and the trends were reverse for the aromatic C and HB/HI ratio. Mean annual precipitation and aboveground biomass were significantly correlated with the contents of SOC and its fractions, the proportions of macro- and micro-aggregates, and the aggregate stability indices along this transect. Among all these C fractions, SOC content and aggregate stability were more closely associated with humic C and silt and clay sized C in comparison with WSOC, EOC, and macro- and micro-aggregate C. The results suggested that alpine meadow soils containing higher SOC exhibited high soil aggregation and aggregate stability. Mean annual precipitation should be the main climate factor controlling the spatial patterns of SOC, soil aggregation, and aggregate stability in this region. The resistant and stable C fractions rather than labile C fractions are the major determinant of SOC stocks and aggregate stability.

Evaluation of water resources conserved by forests in the Hani rice terraces system of Honghe County, Yunnan, China: an application of the fuzzy comprehensive evaluation model

Abstract: The Hani Rice Terraces System, based on gravity-flow irrigation, is one of the Globally Important Agricultural Heritage Systems (GIAHS) pilot sites selected by FAO in 2010. The water resource plays an important role in the sustainable development of this system. The value of water conserved by the forest is influenced by natural, economic and social factors. In this paper, the water quality, per capita water resources, per capita GDP and population density are chosen as indices to construct an index system for a comprehensive evaluation of water resources value. The weights of these indices are 0.443, 0.31, 0.141 and 0.106 respectively, which are determined by the analytic hierarchy process (AHP) method. The water resources value has been assessed by the fuzzy comprehensive evaluation model. The results show that the water resources value in the Hani Rice Terraces System is 4.25 RMB/m3. Evaluating the value of water resources in the Hani Rice Terraces System can provide a reference for ecological compensation, for raising public awareness of the importance of protecting the system, and ultimately achieving its sustainable development.

Driving force and changing trends of vegetation phenology in the Loess Plateau of China from 2000 to 2010

Abstract: Changes in vegetation phenology are key indicators of the response of ecosystems to climate change. Therefore, knowledge of growing seasons is essential to predict ecosystem changes, especially for regions with a fragile ecosystem such as the Loess Plateau. In this study, based on the normalized difference vegetation index (NDVI) data, we estimated and analyzed the vegetation phenology in the Loess Plateau from 2000 to 2010 for the beginning, length, and end of the growing season, measuring changes in trends and their relationship to climatic factors.The results show that for 54.84% of the vegetation, the trend was an advancement of the beginning of the growing season (BGS), while for 67.64% the trend was a delay in the end of the growing season (EGS). The length of the growing season (LGS) was extended for 66.28% of the vegetation in the plateau. While the temperature is important for the vegetation to begin the growing season in this region, warmer climate may lead to drought and can become a limiting factor for vegetation growth. We found that increased precipitation benefits the advancement of the BGS in this area. Areas with a delayed EGS indicated that the appropriate temperature and rainfall in autumn or winter enhanced photosynthesis and extended the growth process. A positive correlation with precipitation was found for 76.53% of the areas with an extended LGS, indicating that precipitation is one of the key factors in changes in the vegetation phenology in this water-limited region. Precipitation plays an important role in determining the phenological activities of the vegetation in arid and semiarid areas, such as the Loess Plateau. The extended growing season will significantly influence both the vegetation productivity and the carbon fixation capacity in this region.

Geospatial susceptibility mapping of earthquake-induced landslides in Nuweiba area, Gulf of Aqaba, Egypt

Abstract: Earthquake induced landslides are one of the most severe geo-environmental hazards that cause enormous damage to infrastructure, property, and loss of life in Nuweiba area. This study developed a model for mapping the earthquake-induced landslide susceptibility in Nuweiba area in Egypt with considerations of geological, geomorphological, topographical, and seismological factors. An integrated approach of remote sensing and GIS technologies were applied for that target. Several data sources including Terra SAR-X and SPOT 5 satellite imagery, topographic maps, field data, and other geospatial resources were used to model landslide susceptibility. These data were used specifically to produce important thematic layers contributing to landslide occurrences in the region. A rating scheme was developed to assign ranks for the thematic layers and weights for their classes based on their contribution in landslide susceptibility. The ranks and weights were defined based on the knowledge from field survey and authors experiences related to the study area. The landslide susceptibility map delineates the hazard zones to three relative classes of susceptibility: high, moderate, and low. Therefore, the current approach provides a way to assess landslide hazards and serves for geo-hazard planning and prediction in Nuweiba area.

Failure mechanism and stability analysis of the Zhenggang landslide in Yunnan Province of China using 3D particle flow code simulation

Abstract: Based on the principle of 3D particle flow code, a numerical landslide run-out model is presented to simulate the failure process of the Zhenggang landslide (in southwestern China) under the effect of water after a rainfall. The relationship between the micro-mechanical parameters and the macro-shear strength of the grain material is determined through numerical calibrations. Then the rainfall effect is considered in numerical simulations and rain-induced sliding processes are performed, which help us to discuss the mechanism of deformation and failure of this landslide together with field observations. It shows the Zhenggang landslide would most likely be activated in Zone I and would gain momentum in Zone II. In order to prevent the potential disaster, a tailing dam is advised to be designed about 175 m downstream from the current landslide boundary of Zone II. Verified by field observations, the presented landslide model can reflect the failure mechanism after rainfall. It can also provide a method to predict the potential disaster and draft disaster prevention measures.

Spatial distribution of mountainous regions and classifications of economic development in China

Abstract: China is a mountainous country with a great diversity of landform and geomorphology. This diversity underlines the need for regionalization and classification. This study defines the mountain terrains and regions with three criteria - elevation, relative height, and slope, and examines the extent of mountainous regions by using county as the basic administrative unit. According to the three parameters of economic base, resident income and development potential, we classified the economic development level in mountainous regions of China. The findings reveal that the extent of the mountainous region accounts for 74.9% of the Mainland China's total area. The economic development of mountainous regions in China is classified into 4 main types and 23 subtypes.

Exploring seven hundred years of transhumance, climate dynamic, fire and human activity through a historical mountain pass in central Spain

Abstract: A high-altitude peat sequence from the heart of the Spanish Central System (Gredos range) was analysed through a multi-proxy approach to determine the sensitivity of high-mountain habitats to climate, fire and land use changes during the last seven hundred years, providing valuable insight into our understanding of the vegetation history and environmental changes in a mountain pass close to a traditional route of transhumance. The pollen data indicate that the vegetation was dominated by shrublands and grasslands with scattered pines in high-mountain areas, while in the valleys cereals, chestnut and olive trees were cultivated. Strong declines of high-mountain pines percentages are recorded at 1540, 1675, 1765, 1835 and 1925 cal AD, which may be related to increasing grazing activities and/or the occurrence of anthropogenic fires. The practice of mountain summer farming and transhumance deeply changed and redesigned the landscape of the high altitudes in central Spain (Gredos range) since the Middle Ages, although its dynamics was influenced in some way by climate variability of the past seven centuries.

Estimation of soil reinforcement by the roots of four post-dam prevailing grass species in the riparian zone of Three Gorges Reservoir, China

Abstract: Soil erosion and bank degradation is a major post-dam concern regarding the riparian zone of the Three Gorges Reservoir. The development and succession of vegetation is a main countermeasure, especially to enhance bank stability and mitigate soil erosion by the root system. In this study, the roots of four prevailing grass species, namely, Cynodon dactylon, Hemarthria altissima, Hemarthria compressa, and Paspalum paspaloides, in the riparian zone were investigated in relation to additional soil cohesion. Roots were sampled using a single root auger. Root length density (RLD) and root area ratio (RAR) were measured by using the WinRHIZO image analysis system. Root tensile strength (T-R) was performed using a manual dynamometer, and the soil reinforcement caused by the roots was estimated using the simple Wu's perpendicular model. Results showed that RLD values of the studied species ranged from 0.24 cm/cm(3) to 20.89 cm/cm(3) at different soil layers, and RLD were significantly greater at 0-10 cm depth in comparison to the deeper soil layers (> 10 cm). RAR measurements revealed that on average 0.21% of the reference soil area was occupied by grass roots for all the investigated species. The measured root tensile strength was the highest for P. paspaloides (62.26 MPa) followed by C. dactylon (51.49 MPa), H. compressa (50.66 MPa), and H. altissima (48.81 MPa). Nevertheless, the estimated maximum root reinforcement in this investigation was 22.5 kPa for H. altissima followed by H. compressa (21.1 kPa), P. paspaloides (19.5 kPa), and C. dactylon (15.4 kPa) at 0-5 cm depth soil layer. The root cohesion values estimated for all species were generally distributed at the 0-10 cm depth and decreased with the increment of soil depth. The higher root cohesion associated with H. altissima and H. compressa implies their suitability for revegetation purposes to strengthen the shallow soil in the riparian zone of the Three Gorges Reservoir. Although the soil reinforcement induced by roots is only assessed from indirect indicators, the present results still useful for species selection in the framework of implementing and future vegetation recovery actions in the riparian zone of the Three Gorges Reservoir and similar areas in the Yangtze River Basin.

Spatio-temporal variation of spring phenology in Tibetan Plateau and its linkage to climate change from 1982 to 2012

Abstract: The influence of climate change on vegetation phenology is a heated issue in current climate change study. We used GIMMS-3g NDVI data to detect the spatio-temporal dynamics of the start of the growing season (SGS) over the Tibetan Plateau (TP) from 1982 to 2012 and to analyze its relationship with temperature and precipitation. No significant trend was observed in the SGS at the regional scale during the study period (R (2) = 0.03, P = 0.352). However, there were three time periods (1982-1999, 1999-2008 and 2008-2012) with identifiable, distinctly different trends. Regions with a significant advancing trend were mainly scattered throughout the humid and semi-humid areas, whereas the regions with a significant delaying trend were mostly distributed throughout the semi-arid areas. Statistical analysis showed that the response of the SGS to climate change varies spatially. The SGS was significantly correlated with the spring temperature and the start of the thermal growth season (STGS) in the relatively humid area. With increasing aridity, the importance of the spring temperature for the SGS gradually decreased. However, the influences of precipitation and winter temperature on the SGS were complicated across the plateau.

An evaluationon using soil aggregate stability as the indicator of interrill erodibility

Abstract: Aggregate stability is a very important predictor of soil structure and strength, which influences soil erodibility. Several aggregate stability indices were selected for estimating interrill erodibility of four soil types with contrasting properties from temperate and subtropical regions of China. This study was conducted to investigate how closely the soil interrill erodibility factor in the Water Erosion Prediction Project (WEPP) model relates to soil aggregate stability. The mass fractal dimension (FD), geometric mean diameter (GMD), mean weight diameter (MWD), and aggregate stability index (ASI) of soil aggregates were calculated. A rainfall simulator with a drainable flume (3.0 m long ×1.0 m wide ×0.5 m deep) was used at four slope gradients (5°, 10°,15° and 20°), and four rainfall intensities (0.6, 1.1, 1.7 and 2.5 mm/min). Results indicated that the interrill erodibility (Ki) values were significantly correlated to the indices of ASI, MWD, GMD, and FD computed from the aggregate wet-sieve data. The Ki had a strong positive correlation with FD, as well as a strong negative correlation with ASI, GMD, and MWD. Soils with a higher aggregate stability and lower fractal dimension have smaller Ki values. Stable soils were characterized by a high percentage of large aggregates and the erodible soils by a high percentage of smaller aggregates. The correlation coefficients of Ki with ASI and GMD were greater than those with FD and MWD, implying that both the ASI and GMD may be better alternative parameters for empirically predicting the soil Ki factor.ASI and GMD are more reasonable in interrill soil erodibility estimation, compared with Ki calculation in original WEPP model equation. Results demonstrate the validation of soil aggregation characterization as an appropriate indicator of soil susceptibility to erosion in contrasting soil types in China.