The building of railways on seasonally frozen ground is inevitable as China pursues economic development and the improvement of its citizens' living standards. However, railway construction in seasonally frozen soil areas is often faced with frost heave, leading to uneven subgrades which seriously threaten traffic safety. This article summarizes extant research results on frost heave mechanism, frost heave factors, and anti-frost measures of railway subgrades in seasonally frozen soil areas.

Black Carbon (BC), as a driver of environmental change, could significantly impact the snow by accelerating melting and decreasing albedo. Systematic documentation of BC studies is crucial for a better understanding of its spatial and temporal trends. This study reviewed the BC studies in the ice core and remote lake sediments and their sources in the northern hemisphere. The literature surveyed points to around 2.9 to 3.7 times increase of BC in the European Alps and up to a three-fold increase of BC in the Himalayan-Tibetan Plateau (HTP) after the onset of industrialization in Europe and Asia, respectively. BC concentration from Greenland ice core showed seven times increase with an interrupted trend after 1950's. South Asian emissions were dominant in the HTP along with a contribution from the Middle East, whereas Western European and local emissions were responsible for the change in BC concentration in the European Alps. In the Arctic, contributions from North America, Europe and Asia persisted. Similarly, a historical reconstruction of lake sediments records demonstrates the effects of emissions from long-range transport, sediment focusing, local anthropogenic activities, precipitation and total input of flux on the BC concentration.

Latitudinal permafrost in Northern Northeast (NNE) China is located in the southern margin of the Eurasian continent, and is very sensitive to climatic and environmental change. Numerical simulations indicate that air temperature in the permafrost regions of Northeast China has been on the rise since the 1950s, and will keep rising in the 21^st century, leading to extensive degradation of permafrost. Permafrost degradation in NNE China has its own characteristics, such as northward shifts in the shape of a "W" for the permafrost southern boundary (SLP), discontinuous permafrost degradation into island-like frozen soil, and gradually disappearing island permafrost. Permafrost degradation leads to deterioration of the ecological environment in cold regions. As a result, the belt of larch forests dominated by Larix gmelinii has shifted northwards and wetland areas with symbiotic relationships with permafrost have decreased significantly. With rapid retreat and thinning of permafrost and vegetation change, the CO₂ and CH₄ flux increases with mean air temperature from continuous to sporadic permafrost areas as a result of activity of methanogen enhancement, positively feeding back to climate warming. This paper reviews the features of permafrost degradation, the effects of permafrost degradation on wetland and forest ecosystem structure and function, and greenhouse gas emissions on latitudinal permafrost in NNE China. We also put forward critical questions about the aforementioned effects, including: (1) establish long-term permafrost observation systems to evaluate the distribution of permafrost and SLP change, in order to study the feedback of permafrost to climate change; (2) carry out research about the effects of permafrost degradation on the wetland ecosystem and the response of Xing'an larch to global change, and predict ecosystem dynamics in permafrost degradation based on long-term field observation; (3) focus intensively on the dynamics of greenhouse gas flux in permafrost degradation of Northeast China and the feedback of greenhouse gas emissions to climate change; (4) quantitative studies on the permafrost carbon feedback and vegetation carbon feedback due to permafrost change to climate multi-impact and estimate the balance of C in permafrost regions in the future.

Nebkhas, discrete mounds of sand and vegetation, are a common landscape feature critical to the stability of desert ecosystems and supported by limited precipitation. Nebkha morphology and spatial pattern vary in landscapes, but it is unclear how they change along precipitation gradients in arid and semi-arid regions. In this study we determined morphology and soil nutrient patterns of nebkha from different regions of northwestern China. The objective of this study was to understand zonal differences among nebkhas and how morphological characteristics and soil nutrient patterns of nebkha change along a precipitation gradient in northwestern China. Our results shows that mean annual precipitation (MAP) had significant effects on morphological characteristics of nebkhas such as height, area, and volume which significantly decreased with an increase in MAP. MAP had significant positive effects on shrub cover and species richness of nebkha. Soil nutrients such as soil organic matter (SOM), total carbon (TC), total nitrogen (TN), and total phosphorus (TP) in the 0-10 cm layer increased with an increase of MAP, and soil nutrient content within nebkhas was higher than in inter-nebkha areas. We concluded that nebkhas are "fertile islands" with an important role in ecosystem dynamics in study regions. Further, MAP is a key factor which determined zonal differences, morphological, and soil nutrients patterns of nebkhas. However, disturbance, such as animal grazing, and planted sand-stabilizing vegetation accelerated the degeneration of nebkha landscapes. We recommend implementation of protective measures for nebkhas in arid and semi-arid areas of China.

This work presents a reference system overview to improve the efficiency of biological improvement of saline-alkali soil developed during the last thirty years, ranging from connotation, general methods and species, soil desalination, soil structure, soil organic content, microbial flora, enzyme activity, yield and economic benefits. The reference system presented is divided into three main groups: suitable varieties, suitable cultivation measures, and a comprehensive evaluation system. There has been a lot of research on biological improvement of saline alkali soil, but these studies are very fragmented and lack a comprehensive standard system. Also, there is a lack of practical significance, particularly with regard to optimal species, densities and times of sowing for particular regions. On the other hand, the corresponding cultivation measure is very important. Therefore, a reference system plays an important role to the effect of biological improvement of saline alkali soil.

This study was conducted to investigate the qualitative and quantitative phytochemical content of the crude extracts of Archidium ohioense, Pelekium gratum, and Hyophila involuta with different alcoholic solvents (ethanol, methanol, Seaman's Schnapps, fresh oil-palm wine, and fresh Raffia-palm wine). The mosses were collected from their natural populations on the central campus of the Obafemi Awolowo University, Ile-Ife, Nigeria. The yield of the extracts was weighed for all the solvents, and the qualitative and quantitative evaluations of the extracts were carried out using standard methods. The results of phytochemical analysis of the crude extracts from the mosses showed the presence of saponins, cardiac glycosides, triterpenes, alkaloids, flavonoids, and steroids. The quantitative phytochemical analysis of the crude extracts showed that ethanolic extracts of Hyophila involuta had the highest flavonoid content (288.37±0.10 mg RE/g), and Raffia-palm-wine extracts of Hyophila involuta had the highest saponin content (224.70±0.02 mg/g), while the methanolic extract of Archidium ohioense had the highest cardiac glycosides content (63.71±0.14 mg/g), and the Raffia-palm wine extract of Hyophila involuta had the highest alkaloids content (102.50±0.12 mg/g). Raffia- and oil-palm wines were observed to be the most effective solvents for all the mosses studied, followed by Seaman's Schnapp, while methanol and ethanol were less effective. The study concluded that the extracts of the mosses studied contain pharmacologically active constituents that can be used for therapeutic purposes.

Land surface actual evapotranspiration is an important process that influences the Earth's energy and water cycles and determines the water and heat transfer in the soil-vegetation-atmosphere system. Meanwhile, the cryosphere's hydrological process is receiving extensive attention, and its water problem needs to be understood from multiple perspectives. As the main part of the Chinese cryosphere, the Tibetan Plateau faces significant climate and environmental change. There are active interaction and pronounced feedback between the environment and ET_a in the cryosphere. This article mainly focuses on the research progress of ET_a in the Tibetan Plateau. It first reviews the ET_a process, characteristics, and impact factors of typical underlying surfaces in the Tibetan Plateau (alpine meadows, alpine steppes, alpine wetlands, alpine forests, lakes). Then it compares the temporal and spatial variations of ET_a at different scales. In addition, considering the current greening of cryosphere vegetation due to climate change, it discusses the relationship between vegetation greening and transpiration to help clarify how vegetation activities are related to the regional water cycle and surface energy budget.

The Ecological-living-productive land (ELPL) classification system was proposed in an effort to steer China’s land pattern to an ecological-centered path, with the development model shifting from a single function into more integrated multi-function land use. The focus is coordinating the man-land contradictions and developing an intensive, efficient and sustainable land use policy in an increasingly tense relationship between humans and nature. Driven by socioeconomic change and rapid population growth, many cities are undergoing urban sprawl, which involves the consumption of cropland and ecological land and threatens the ecological balance. This paper aims to quantitatively analyze the critical effects of ELPL changes on eco-environmental quality according to land use classification based on leading function of ecology, living and production from 1990 to 2015 with a case study of Xining City. Also, four future land use scenarios were simulated for 2030 using the Future Land Use Simulation (FLUS) model that couples human and natural effects. Our results show a decrease in productive land (PL) and an increase in ecological land (EL) and living land (LL) in Xining City. Forestry ecological land (FEL) covered the top largest proportion; agriculture productive land (APL) showed the greatest reduction and urban and rural living land (U-RLL) presented a dramatic increase. The eco-environmental quality improved in 1990-2010, mainly affected by the conversion of APL to FEL and GEL. However, the encroachment of U-RLL into APL, other ecological land (OEL) and FEL was the main contributor to the decline in eco-environmental quality in 2010-2015 as well as the primary reason for the increase area of lower-quality. The Harmonious Development (HD)-Scenario, characterized by a rational allocation of LL and PL and a better eco-environment, would have implications for planning and monitoring future management of ELPL, and may represent a valuable reference for local policy-makers.

Light-absorbing impurities on glaciers are important factors that influence glacial surface albedo and accelerate glacier melt. In this study, the quantity of light-absorbing impurities on Keqikaer Glacier in western Tien Shan, Central Asia, was measured. We found that the average concentrations of black carbon was 2,180 ng/g, with a range from 250 ng/g to more than 10,000 ng/g. The average concentrations of organic carbon and mineral dust were 1,738 ng/g and 194 μg/g, respectively. Based on simulations performed with the Snow Ice Aerosol Radiative model simulations, black carbon and dust are responsible for approximately 64% and 9%, respectively, of the albedo reduction, and are associated with instantaneous radiative forcing of 323.18 W/m² (ranging from 142.16 to 619.25 W/m²) and 24.05 W/m² (ranging from 0.15 to 69.77 W/m²), respectively. For different scenarios, the albedo and radiative forcing effect of black carbon is considerably greater than that of dust. The estimated radiative forcing at Keqikaer Glacier is higher than most similar values estimated by previous studies on the Tibetan Plateau, perhaps as a result of black carbon enrichment by melt scavenging. Light-absorbing impurities deposited on Keqikaer Glacier appear to mainly originate from central Asia, Siberia, western China (including the Taklimakan Desert) and parts of South Asia in summer, and from the Middle East and Central Asia in winter. A footprint analysis indicates that a large fraction (>60%) of the black carbon contributions on Keqikaer Glacier comes from anthropogenic sources. These results provide a scientific basis for regional mitigation efforts to reduce black carbon.

Determining an optimal sample size is a key step in designing field surveys, and is particularly important for detecting the spatial pattern of highly variable properties such as soil organic carbon (SOC). Based on 550 soil sampling points in the near-surface layer (0 to 20 cm) in a representative region of northern China’s agro-pastoral ecotone, we studied effects of four interpolation methods such as ordinary kriging (OK), universal kriging (UK), inverse distance weighting (IDW) and radial basis function (RBF) and random subsampling (50, 100, 200, 300, 400, and 500) on the prediction accuracy of SOC estimation. When the Shannon's Diversity Index (SHDI) and Shannon's Evenness Index (SHEI) was 2.01 and 0.67, the OK method appeared to be a superior method, which had the smallest root mean square error (RMSE) and the mean error (ME) nearest to zero. On the contrary, the UK method performed poorly for the interpolation of SOC in the present study. The sample size of 200 had the most accurate prediction; 50 sampling points produced the worst prediction accuracy. Thus, we used 200 samples to estimate the study area's soil organic carbon density (SOCD) by the OK method. The total SOC storage to a depth of 20 cm in the study area was 117.94 Mt, and its mean SOCD was 2.40 kg/m². The SOCD kg/(C?m²) of different land use types were in the following order: woodland (3.29) > grassland (2.35) > cropland (2.19) > sandy land (1.55).

Based on an investigation of four published batches listing 3,140 national intangible cultural heritage (ICH) projects in China and using GIS and some quantitative analysis methods, the spatial structure was investigated and the characteristics and distribution discussed. The distribution of ICHs in China is agglomerative and spatially dependent. From the view of ICH type, each type is distributed in different places, for different reasons, with history being the most important one we found. Nationwide, high-density cores are located in the Beijing-Tianjin-Hebei region and the Yangtze River Delta region. High densities of ICH are concentrated in flat, water-rich regions where broad-leaved forests dominate plains and low mountain areas—areas that have fertile soil, pleasant weather, a long history of culture, ethnic agglomeration, and development. This paper suggests that development of the ICH should be based on discovering unknown items, to break the existing pattern of strong cohesion and high density, and to seek a balanced development of the whole.

The Soil and Water Assessment Tool (SWAT) was implemented in a small forested watershed of the Soan River Basin in northern Pakistan through application of the sequential uncertainty fitting (SUFI-2) method to investigate the associated uncertainty in runoff and sediment load estimation. The model was calibrated for a 10-year period (1991-2000) with an initial 4-year warm-up period (1987-1990), and was validated for the subsequent 10-year period (2001-2010). The model evaluation indices R² (the coefficient of determination), NS (the Nash-Sutcliffe efficiency), and PBIAS (percent bias) for stream flows simulation indicated that there was a good agreement between the measured and simulated flows. To assess the uncertainty in the model outputs, p-factor (a 95% prediction uncertainty, 95PPU) and r-factors (average wideness width of the 95PPU band divided by the standard deviation of the observed values) were taken into account. The 95PPU band bracketed 72% of the observed data during the calibration and 67% during the validation. The r-factor was 0.81 during the calibration and 0.68 during the validation. For monthly sediment yield, the model evaluation coefficients (R² and NS) for the calibration were computed as 0.81 and 0.79, respectively; for validation, they were 0.78 and 0.74, respectively. Meanwhile, the 95PPU covered more than 60% of the observed sediment data during calibration and validation. Moreover, improved model prediction and parameter estimation were observed with the increased number of iterations. However, the model performance became worse after the fourth iterations due to an unreasonable parameter estimation. Overall results indicated the applicability of the SWAT model with moderate levels of uncertainty during the calibration and high levels during the validation. Thus, this calibrated SWAT model can be used for assessment of water balance components, climate change studies, and land use management practices.

The Hexi Inland River Basin in an arid region of northwestern China was chosen as the study area for this research. The authors define the vulnerability of an oasis social-ecological system to glacier change; select 16 indicators from natural and socioeconomic systems according to exposure, sensitivity, and adaptive capacity; and construct a vulnerability-assessment indicator system aimed at an inland river basin in the arid region of Northwestern China. Vulnerability of the oasis social-ecological system affected by glacier change in the study area is evaluated by Spatial Principal Component Analysis (SPCA) under the circumstance of glacier change. The key factors affecting the vulnerability are analyzed. The vulnerability of the oasis social-ecological system in the Hexi Inland River Basin affected by glacier change is of more than medium grade, accounting for about 48.0% of the total number of counties in the study area. In terms of the spatial pattern of the vulnerability, the oasis economic belt is the most vulnerable. With the rapid development of the area's society and economy, the exposure of the system to glacial changes is significantly increased; and an increase in glacial meltwater is not enough to overcome the impact of increased exposure, which is the main reason for the high vulnerability. Based on the result of the vulnerability analysis and combined with the present industrial structure in the Hexi Inland River Basin, near-, medium-, and long-term adaptation initiatives are put forward in the article.

Characterizing spatial and temporal variability of soil salinity is tremendously important for a variety of agronomic and environmental concerns in arid irrigation areas.This paper reviews the characteristics and spatial and temporal variations of soil salinization in the Ili River Irrigation Area by applying a geostatistical approach.Results showed that:(1) the soil salinity varied widely,with maximum value of 28.10 g/kg and minimum value of 0.10 g/kg,and was distributed mainly at the surface soil layer.Anions were mainly SO₄^2- and Cl^-,while cations were mainly Na⁺ and Ca²⁺;(2) the abundance of salinity of the root zone soil layer for different land use types was in the following order:grassland >cropland >forestland. The abundance of salinity of root zone soil layers for different periods was in the following order:March >June >September;(3) the spherical model was the most suitable variogram model to describe the salinity of the 0-3 cm and 3-20 cm soil layers in March and June,and the 3-20 cm soil layer in September,while the exponential model was the most suitable variogram model to describe the salinity of the 0-3 cm soil layer in September.Relatively strong spatial and temporal structure existed for soil salinity due to lower nugget effects;and(4) the maps of kriged soil salinity showed that higher soil salinity was distributed in the central parts of the study area and lower soil salinity was distributed in the marginal parts. Soil salinity tended to increase from the marginal parts to the central parts across the study area.Applying the kriging method is very helpful in detecting the problematic areas and is a good tool for soil resources management.Managing efforts on the appropriate use of soil and water resources in such areas is very important for sustainable agriculture,and more attention should be paid to these areas to prevent future problems.

The sufficient bond between concrete and rock is an important prerequisite to ensure the effect of shotcrete support. However, in cold regions engineering protection system, the bond condition of rock and concrete surface is easily affected by freeze-thaw cycles, resulting in interface damage, debonding and even supporting failure. Understanding the micromechanisms of the damage and debonding of the rock-concrete interface is essential for improving the interface protection. Therefore, the micromorphology, micromechanical properties, and microdebonding evolution of the sandstone-concrete interface transition zone (ITZ) under varying freeze-thaw cycles (0, 5, 10, 15, 20) were studied using scanning electron microscope, stereoscopic microscope, and nano-indentation. Furthermore, the distribution range and evolution process of ITZ affected by freeze-thaw cycles were defined. Major findings of this study are as follows: (1) The microdamage evolution law of the ITZ under increasing freeze-thaw cycles is clarified, and the relationship between the number of cracks in the ITZ and freeze-thaw cycles is established; (2) As the number of freeze-thaw cycles increases, the ITZ's micromechanical strength decreases, and its development width tends to increase; (3) The damage and debonding evolution mechanisms of sandstone-concrete ITZ under freeze-thaw cycles is revealed, and its micromechanical evolution model induced by freeze-thaw cycles is proposed.

The cluster planting pattern (3 plants per hole) for cotton (Gossypium hirsutum L.) may increase economic yield over those of the traditional planting pattern (1 plant per hole) in arid regions of China. This increase in yield depends on either increased biomass production or greater partitioning to fruit. This study was conducted to determine whether differences in biomass accumulation or partitioning to reproductive growth contributed to higher yield in the cluster planting pattern compared with the traditional one. Growth parameters, biomass accumulation, crop growth rate and partitioning between cluster planting pattern and traditional planting pattern was compared in northwest of China. The biomass production and partitioning in cluster planting plot was higher than in traditional planting one. Biomass accumulation was faster early in the clustered treatment, and it was also higher at harvest time. Total dry matter production per unit area was significantly higher than in the traditional planting. On a per plant basis, dry matter accumulation was faster and total biomass production was significantly higher in the cluster planting pattern. Numbers of sympodia and boll sizes were also larger, indicating that facilitation among plants was promoting crop yield. The increase in yield in the cluster planting treatment occurred through increased partitioning of dry matter to fruits than in the traditional planting pattern, resulting in more bolls and increased lint yield in arid regions.

Regarding the freezing damage of high-grade highway subgrade in seasonally frozen area, the thesis explores the effect on the dynamic behavior of subgrade soil under freeze-thaw cycles and draws the change law of parameters (including dynamic strength, dynamic cohesion, and internal friction angle; and dynamic elastic modulus) of high-grade highway-subgrade soil with the number of freeze-thaw cycles. It aims to provide the reference for operation and maintenance of a high-grade highway. Conclusions: (1) Dynamic strength tends to decline evidently after freeze-thaw cycles, with 60%~70% decline after three cycles, and remains stable after five to seven cycles. (2) With the number of freeze-thaw cycles increasing, the internal friction angle fluctuates within a certain range without an obvious change law, only presenting the tendency of dropping off. The dynamic cohesion declines obviously, about 20%~40% after seven freeze-thaw cycles, and then tends to be stable. (3) With the number of freeze-thaw cycles increasing, the dynamic elastic modulus and maximum dynamic elastic modulus are inclined to decrease distinctly. After five freeze-thaw cycles, the former declines 30%~40% and then remains stable. Meanwhile, the latter falls 20%~40%.

Soil moisture is a critical state affecting a variety of land surface and subsurface processes. We report investigation results of the factors controlling vertical variation of soil moisture and sand transport rate of three types of dunes on the southeastern margin of the Mu Us Sandy Land. Samples were taken from holes drilled to a depth of 4 m at different topographic sites on the dunes, and were analyzed for soil moisture, grain-size distribution and surface sediment discharge. The results show that: (1) The average soil moisture varies in different types of dunes, with the following sequences ordered from highest to lowest: in the shrubs-covered dunes and the trees-covered dunes the sequence is from inter-dunes lowland to windward slope to leeward slope. The average moisture in the bare-migratory sand dunes is sequenced from inter-dunes lowland to leeward slope to windward slope. (2) Vegetation form and surface coverage affect the range of soil moisture of different types of dunes in the same topographic position. The coefficient of variation of soil moisture for shrubs-covered dunes is higher than that of other types of dune. (3) The effect of shrubs on dune soil moisture is explained in terms of the greater ability of shrubs to trap fine-grained atmospheric dust and hold moisture. (4) The estimated sand transport rates over sand dunes with sparse shrubs are less than those over bare-migratory dunes or sand dunes with sparse trees, indicating that shrubs are more effective in inhibiting wind erosion in the sandy land area.

Probable maximum precipitation (PMP) is widely used by hydrologists for appraisal of probable maximum flood (PMF) used for soil and water conservation structures, and design of dam spillways. A number of methods such as empirical, statistical and dynamic are used to estimate PMP, the most favored being statistical and hydro-meteorological. In this paper, PMP estimation in mountainous regions of Pakistan is studied using statistical as well as physically based hydro-meteorological approaches. Daily precipitation, dew point, wind speed and temperature data is processed to estimate PMP for a one-day duration. Maximum precipitation for different return periods is estimated by using statistical approaches such as Gumble and Log-Pearson type-III (LP-III) distribution. Goodness of fit (GOF) test, chi-square test, correlation coefficient and coefficient of determination were applied to Gumble and LP-III distributions. Results reveal that among statistical approaches, Gumble distribution performed the best result compared to LP-III distribution. Isohyetal maps of the study area at different return periods are produced by using the GIS tool, and PMP in mountainous regions varies from 150 to 320 mm at an average value of 230.83 mm. The ratio of PMP for one-day duration to highest observed rainfall (HOR) varied from 1.08 to 1.29 with an average value of 1.18. An appropriate frequency factor (K_m) is very important which is a function of mean for observed precipitation and PMP for 1-day duration, and K_m values varies from 2.54 to 4.68. The coefficient of variability (C_v) varies from minimum value of 28% to maximum value of 43.35%. It was concluded that the statistical approach gives higher results compared to moisture maximization (MM) approach. In the hydro-meteorological approach, moisture maximization (MM) and wind moisture maximization (WMM) techniques were applied and it was concluded that wind moisture maximization approach gives higher results of PMP as compared to moisture maximization approach as well as for Hershfield technique. Therefore, it is suggested that MM approach is the most favored in the study area for PMP estimation, which leads to acceptable results, compared to WMM and statistical approaches.

Canopy effect refers to the phenomenon in which moisture accumulates underneath an impervious cover. A canopy effect can lead to full saturation of the soil underneath the impervious cover. A recent theoretical study separates the canopy effect into two types. The first one is caused by evaporation-condensation in unsaturated soils, while the second one is induced by freezing-enhanced vapour transfer in unsaturated soils. To validate experimentally these two types of canopy effect and to reveal their mechanisms, moisture-migration experiments were carried out, using a newly developed laboratory apparatus for unsaturated frozen soils. Six conditions were applied to the calcareous sand, with different initial water contents and boundary temperatures. The results show that water content in the upper portion of the sample increased under an upward temperature gradient, and the increment of water content was greater if the soil was subjected to freezing. For the freezing cases, the depth of the peak water content was in line with the freezing front. And the greater the initial water content, the more the water content accumulated at the freezing front. However, a lower cooling rate seemed to facilitate vapour migration. For the unfrozen cases, the water content in the upper portion of the sample also increased; and the increases became more apparent with a higher initial moisture content. The temperature gradient can also inhibit the vapour migration. A less steep temperature gradient always resulted in a more notable inhibition effect. Test results seem to verify the theory of the canopy effect.

In this study, a systematic survey of cultural airborne fungi was carried out in the occurrence environments of wall paintings that are preserved in the Tiantishan Grottoes and the Western Xia Museum, China. A bio-aerosol sampler was used for sampling in four seasons in 2016. Culture-dependent and -independent methods were taken to acquire airborne fungal concentration and purified strains; by the extraction of genomic DNA, amplification of fungal ITS rRNA gene region, sequencing, and phylogenetic analysis, thereafter the fungal community composition and distribution characteristics of different study sites were clarified. We disclosure the main environmental factors which may be responsible for dynamic changes of airborne fungi at the sampling sites. The concentration of cultural airborne fungi was in a range from 13 to 1,576 CFU/m³, no significant difference between the two sites at the Tiantishan Grottoes, with obvious characteristics of seasonal variation, in winter and spring were higher than in summer and autumn. Also, there was a significant difference in fungal concentration between the inside and outside of the Western Xia Museum, the outside of the museum was far more than the inside of the museum in the four seasons, particularly in the winter. Eight fungal genera were detected, including Cladosporium, Penicillium, Alternaria, and Filobasidium as the dominant groups. The airborne fungal community structures of the Tiantishan Grottoes show a distinct characteristic of seasonal variation and spatial distribution. Relative humidity, temperature and seasonal rainfall influence airborne fungal distribution. Some of the isolated strains have the potential to cause biodeterioration of ancient wall paintings. This study provides supporting information for the pre-warning conservation of cultural relics that are preserved at local sites and inside museums.

This study analyzed soil moisture, soil erosion, and vegetation in the source region of the Yangtze River from 2005 to 2016. We found that soil moisture showed an increasing trend from 2005 to 2009 but decreased from 2009 to 2016. The surface soil moisture was severely affected by seasonal changes in the source region of the Yangtze River, especially in the soil from 0 to 40 cm. However, seasonal variation of soil moisture deeper than 40 cm was different from that in the upper layer. Soil moisture below 40 cm wasn't affected by the seasonal variation. Soil moisture from 0 to 50 cm and the average thickness of wind deposition showed a positive correlation in the study area from 2005 to 2016. For environmental protection in the source region of the Yangtze River, wind deposition played a role in water retention. Similarly, a positive correlation also existed between the average thickness of wind erosion and soil moisture. Deep-soil moisture was the key factor for vegetation structure on the Qinghai-Tibet Plateau. The results are also helpful for further understanding the variation of soil moisture on the Tibetan Plateau and providing a scientific basis for effectively protecting and controlling the ecological environment in the future.

The uneven frost heave of frost-susceptible subgrade soil causes track irregularity, which highly enhances train vibration and affects the comfort and safety of railway transportation. This paper presents a coupled thermo-hydro-mechanical (THM) analysis for the freezing behavior of railway located above a box culvert. The vertical acceleration of the vehicle, an indicator of riding comfort, is predicted through a vehicle dynamic model. The results reveal that the existence of a box culvert changes the subgrade thermal pattern, leading to a deeper frost penetration depth. The frost heave amount above the box culvert is larger than the adjacent section, resulting in uneven track structure upheave and track irregularity. This frost-induced track irregularity highly affects train vibration.

The Haerbin-Dalian Passenger Dedicated Line is the first high-speed railway constructed in the seasonally frozen ground regions of northeastern China. Frost heave diseases occurred in the first winter of its operation (between October 2012 and January 2013), and frost heave was observed mainly in the roadbed fills that were considered not susceptible to frost heave. This paper proposes applying two special pavements—black pavement and insulation-black pavement—to improve the thermal regime of the roadbed. Three numerical models of the roadbed temperature field were built based on the field conditions of the Changchun section (D3K692+840 to D3K692+860).The results show that: (1) Compared with cement pavement, black pavement and insulation-black pavement could reduce the freezing index at the roadbed surface by 37% and 64%, respectively, which could influence the maximum frozen depth; (2) the maximum frozen depths under the black pavement and insulation-black pavement were respectively 1.3-1.4 m and 1 m. Compared with cement pavement, they could reduce the maximum frozen depth by 0.4m and 0.7-0.8m, respectively, which would reduce the permitted amount of frost heave by 4 mm and 7-8 mm, which would meet the deformation limitestablished by the Code for Design on Special Subgrade of Railway; (3) the freezing periods of the black pavement and the insulation-black pavement were, respectively, approximatelyfour months and two months. Compared with cement pavement, they could reduce the freezing period by approximately 19 days and 40 days, respectively, and delay the initial freezing time by 9 days and 18 days; and (4) compared with cement pavement, black pavement and black-insulation pavement could reduce the frozen areas of roadbeds in the cold season, which suggeststhat these two special pavements could provide better thermal stability for roadbeds.

Hydrological circulation, as the most basic material cycle and active natural phenomenon on earth, exerts a significant influence on climate change. The mid-Holocene is an important period to better understand modern environmental change; however, little research has focused on its quantitative simulation of paleo-hydrological process. In this research, we first collected chronological evidence and sediment records from six Holocene sedimentary sections in the Shiyang River Basin to reconstruct the mid-Holocene environment and terminal paleo-lake area. Secondly, we comprehensively analyzed modern pollen combinations and their propagation characteristics in surface soil, air, river and lacustrine sediments in the Shiyang River Basin, and combined the pollen records, as well as quantitatively reconstructed the millennial-scale vegetation zones. Finally, based on the land-cover adjustment results during the mid-Holocene, we successfully used the Soil and Water Assessment Tool (SWAT) model, a modern distributed hydrological watershed model, to simulate mid-Holocene runoff in the basin. Results show that the reconstructed climate in the basin was warmer and moister than that in recent times. Vegetation types in the mid-Holocene mainly consisted of sub-alpine shrub distributed between 2,550 m and 2,750 m, forest at an elevation of 2,550-2,750 m, steppe at an elevation of 1,550-2,150 m and desert steppe below 1,550 m. The upstream, midstream, downstream and average annual runoff of the mid-Holocene in the basin were 16.76×10⁸ m³, 22.86×10⁸ m³, 9.00×10⁸ m³ and 16.20×10⁸ m³ respectively, compared to 15.61×10⁸ m³ of modern annual runoff. Also, the area of terminal paleo-lake in the mid-Holocene was 628 km². Thus, this study provides a new quantitative method for paleo-hydrological simulation.

Understanding the effect of biodiversity on ecosystem function is critical to promoting the sustainability of ecosystems and species conservation in natural ecosystems. We observed species composition, species richness and aboveground biomass, and simulated the competitive assemblages in a natural grassland ecosystem of China, aiming to test some assumptions and predictions about biodiversity–stability relationships. Our results show that aboveground productivity and temporal stability increased significantly with increasing species richness, and via a combination of overyielding, species asynchrony, and portfolio effects. Species interactions resulted in overyielding caused by trait-independent complementarity, and were not offset by a negative dominance effect and trait-dependent complementarity effect. Therefore, the mechanisms underlying the biodiversity effect shifted from the selection effect to the complementarity effect as diversity increased, and both effects were coexisted but the complementarity effect represent a mechanism that facilitates long term species coexistence in a natural grassland ecosystem of China.

Based on ground temperatures and deformations monitored at the Xieshuihe site along the Qinghai-Tibet Highway (QTH) in permafrost regions from 2004 to 2015, variation of artificial permafrost table (APT), maximum frozen depth (MFD), thawed interlayer thickness (TIT) and ground temperature beneath embankment is analyzed, respectively. The results indicate that under the embankment, the change of APT occurred from October to December of that year and presented a deepening trend. The change of MFD occurred from April to June of that year with no obvious change trend, and TIT had an increasing trend year by year, which mainly resulted from the deepening artificial permafrost table. Mean annual ground temperature at 0.5 m depth was 3.91℃ higher beneath the embankment center than that under the natural field. The rising ground temperature at shallow layer of embankment resulted in the development of thawed interlayer beneath the embankment and warming of underlying permafrost. Embankment settlement is closely associated with TIT. Greater settlement easily occurs when permafrost with higher ice content exists under the thawed interlayer, and in turn the settlement is smaller when permafrost with lower ice content exists under the thawed interlayer.

Maqu County is located in the northeast Qinghai-Tibetan Plateau, and it is the main watershed for the Yellow River. The ecosystem there is extremely vulnerable and sensitive to climate change and human activities, which have caused significant deterioration of the eco-environment in this region. In order to restore the ecological environment, a government project to restore the grazing areas to grassland was implemented in Maqu County in early 2004. This study evaluates the effects of that restoration project on land use and land cover change (LUCC), and explores the driving forces of LUCC in Maqu County. In the study we used Landsat images obtained in 1989, 2004, 2009, and 2014 to establish databases of land use and land cover. Then we derived LUCC information by overlaying these layers using GIS software. Finally, we analyzed the main forces responsible for LUCC. The results showed that forests, high-coverage grasslands, and marshes experienced the most significant decreases during 1989-2004, by 882.8 ha, 35,250.4 ha, and 2,753.4 ha, respectively. However, moderate- and low-coverage grasslands and sand lands showed the opposite trend, increasing by 12,529.7 ha, 25,491.0 ha, and 577.5 ha, respectively. LUCC in 2004-2009 showed that ecological degradation slowed compared with 1989-2004. During 2009-2014, high- and moderate-coverage grasslands increased obviously, but low-coverage grasslands, marshes, unused lands, sand lands, and water areas showed the opposite trend. These results suggested that the degradation of the eco-environment was obvious before 2009, showing a decrease in the forests, grasslands, and water areas, and an increase in unused lands. The ecological degradation was reversed after 2009, as was mainly evidenced by increases in high- and moderate-coverage grasslands, and the shrinkage rate of marshes decreased obviously. These results showed that the project of restoring grazing lands to grassland had a positive effect on the LUCC. Other major factors that influence the LUCC include increasing temperature, variation in the seasonal frozen soil environment, seasonal overgrazing, and pest and rodent damage.

This paper aims to determine the optimal fines content of coarse-grained soil required to simultaneously achieve weaker frost susceptibility and better bearing capacity. We studied the frost susceptibility and strength properties of coarse-grained soil by means of frost heaving tests and static triaxial tests, and the results are as follows:(1) the freezing temperature of coarse-grained soil decreased gradually and then leveled off with incremental increases in the percent content of fines; (2) the fines content proved to be an important factor influencing the frost heave susceptibility and strength properties of coarse-grained soil. With incremental increases in the percent content of fines, the frost heave ratio increased gradually and the cohesion function of fines effectively enhanced the shear strength of coarse-grained soil before freeze-thaw, but the frost susceptibility of fines weakened the shear strength of coarse-grained soil after freeze-thaw; (3) with increasing numbers of freeze-thaw cycles,the shear strength of coarse-grained soil decreased and then stabilized after the ninth freeze-thaw cycle, and therefore the mechanical indexes of the ninth freeze-thaw cycle are recommended for the engineering design values; and (4) considering frost susceptibility and strength properties as a whole, the optimal fines content of 5% is recommended for railway subgrade coarse-grained soil fillings in frozen regions.

Freeze-thaw hazard is one of the main problems in cold regions engineering and artificial ground freezing engineering. To mitigate freeze-thaw hazards, it is essential to investigate the effects of freeze-thaw on soils engineering properties. This paper summarizes the effects of freeze-thaw on the physical and mechanical properties of soils reported in recent studies. The differences of freeze-thaw conditions between freezing shaft sinking and cold regions engineering are discussed. Based on the technological characteristics of freezing shaft sinking in deep alluvium, we further attempt to identify key research needs regarding the freeze-thaw effects on the engineering properties of deep soils.

Grasslands and agro-ecosystems occupy one-third of the global terrestrial area. However, great uncertainty still exists about their contributions to the global carbon cycle. This study used various combinations of a simple ecosystem respiration model and a photosynthesis model to simulate the influence of different climate factors, specifically radiation, temperature, and moisture, on the ecosystem carbon exchange at two dissimilar study sites. Using a typical alpine meadow site in a cold region and a typical cropland site in an arid region as cases, we investigated the response characteristics of productivity of grasslands and croplands to different environmental factors, and analyzed the seasonal change patterns of different model parameters. Parameter estimations and uncertainty analyses were performed based on a Bayesian approach. Our results indicated that: (1) the net ecosystem exchange (NEE) of alpine meadow and seeded maize during the growing season presented obvious diurnal and seasonal variation patterns. On the whole, the alpine meadow and seeded maize ecosystems were both apparent sinks for atmospheric CO₂; (2) in the daytime, the mean NEE of the two ecosystems had the largest values in July and the lowest values in October. However, overall carbon uptake in the cropland was greater than in the alpine meadow from June to September; (3) at the alpine meadow site, temperature was the main limiting factor influencing the ecosystem carbon exchange variations during the growing season, while the sensitivity to water limitation was relatively small since there is abundant of rainfall in this region; (4) at the cropland site, both temperature and moisture were the most important limiting factors for the variations of ecosystem carbon exchanges during the growing season; and (5) some parameters had an obvious characteristic of seasonal patterns, while others had only small seasonal variations.

Tamarix ramosissima Ledeb. is a typical hardy desert plant growing in arid regions of Northwest China. Sap flow in stems of T. ramosissima plants were measured continuously to determine the diurnal and seasonal variations of sap flow and to understand the water requirements of this species and the response of sap flow to meteorological factors. This article compared the sap flow rate measured by the heat balance method with the transpiration rate measured by rapid weighing, and validated that heat balance sap flow gauges were reliable for monitoring transpiration. The influence of meteorological factors on stem sap flow during the growing season was: solar radiation > vapor pressure deficit > air temperature > relative humidity > wind speed. Bidirectional sap flows occurred at night, and negative sap flow generally corresponded to high atmospheric humidity. The average error in predicted sap flow rate ranged from -0.78% to 14.00% from June to September and for transpiration the average error was 8.19%. Therefore, based on the functional equations between sap flow and meteorological factors as well as sapwood area, transpiration of an individual plant, and even the stand-level transpiration, can be estimated accurately through extrapolation.

Holocene δ¹⁸O records from various archives (ice cores, cave stalagmites, and peat sediments) from the Xinjiang region of northwestern China, in arid central Asia (ACA), are all derived ultimately from local precipitation δ¹⁸O (δ¹⁸O_p). Nevertheless, they have been proposed as indicators of different climatic parameters, such as wetness and temperature changes. This article summarizes previously reported records of moisture sources for the Xinjiang region and the results of modern observations conducted at an ice core site and a peat site in the Altai Mountains. The findings are used to propose that the overall positive trends in Holocene δ¹⁸O records from the various archives from the Xinjiang region primarily reflect the Holocene's long-term warming trend. It is concluded that more site-specific modern observations are needed to further elucidate the environmental significance of Holocene δ¹⁸O records from this region, especially for the separation of different seasonal temperature signals present within δ¹⁸O records.

In cold regions, the widened subgrade could produce uneven frost heave that is detrimental to the pavement. This study investigates the differential frost heave characteristics in a widened subgrade. The field monitoring system mainly consists of temperature, moisture, and displacement sensors and distributed optical fiber cables for strain measurement. The monitoring results show that the cooling period in the subgrade is longer than the warming period. Water content in the subgrade changes significantly within 0-2 m below the subgrade surface but stabilizes within 2-5 m. The maximum frost heave occurs from February to March. In comparison, the existing subgrade has a longer freezing period and larger heave value, caused by the higher density and water content inside. Water in the existing subgrade migrates into the new one after widening, leading to frost heave reduction in the existing subgrade. Simultaneously, the traffic loads result in the consolidation of the new subgrade, thus reducing the heave value in the second year. In the third year, the water supply from the existing subgrade facilitates the frost heave in the new subgrade. The tensile strain distributions obtained by the distributed optical fiber cables show that the maximum differential frost heave occurs at the joint between the existing and new subgrades. The differential frost heave gradually stabilizes after three years. Finally, an improved frost heave prediction model is developed based on the segregation potential concept and monitoring results.

The sustainability of ecosystem restoration of refuse dumps in open-pit coal mines depends on plant species selection, their configuration, and the optimal usage of water resources. This study is based on field experiments in the northern refuse dump of the Heidaigou open-pit coal mine in Inner Mongolia of China established in 1995. Eight plant configurations, including trees, shrubs, grasses, and their combinations, as well as the adjacent community of natural vegetation, were selected. The succession of the revegetated plants, soil water storage, the spatiotemporal distribution of plant water deficits degree and its compensation degree were also studied. Results indicated that the vegetation cover (shrubs and herbaceous cover), richness, abundance, soil nutrients (soil organic matter, N and P), and biological soil crust coverage on the soil surface are significantly influenced by the vegetation configurations. The average soil water storage values in the shrub+grass and grass communities throughout the growing season are 208.69 mm and 206.55 mm, which are the closest to that of in the natural vegetation community (215.87 mm). Plant water deficits degree in the grass and shrub+grass communities were the lowest, but the degrees of water deficit compensation in these configuration were larger than those of the other vegetation configurations. Differences in plant water deficit degree and water compensation among the different configurations were significant (P<0.05). Plant water deficit degrees were predominantly minimal on the surface, increased with increasing soil depth, and remained stable at 80 cm soil depth. The soil moisture compensation in the natural vegetation, shrub+grass, and grass communities changed at 10%, while that in other vegetation communities changed between 20% and 40%. Overall, we conclude that the shrub+grass and grass configuration modes are the optimal vegetation restoration models in terms of ecohydrology for future ecological engineering projects.

Freeze-thaw damage is the most common disease of semi-rigid bases in cold regions, which may greatly affect the durability of roadways. In this study, the compressive strength and frost resistance of four different types of semi-rigid bases (lime-fly ash-stabilized sand, cement-stabilized sand, lime-fly ash-stabilized gravel, and cement-stabilized gravel) are assessed by varying the materials content. Based on freeze-thaw and compressive strength tests, this paper presents the performance of the different materials, each having different physical properties, and the optimal amounts of materials contents are proposed.

Due to a series of linear projects built along National Highway 214, the second "Permafrost Engineering Corridor" on the Qinghai-Tibet Plateau has formed. In this paper, by overcoming the problems of data decentralization and standard inconsistency, permafrost characteristics and changes along the engineering corridor are systematically summarized based on the survey and monitoring data. The results show that: 1) Being controlled by elevation, the permafrost is distributed in flake discontinuity with mountains as the center along the line. The total length of the road section in permafrost regions is 365 km, of which the total length of the permafrost section of National Highway 214 is 216.7 km, and the total length of the permafrost section of Gong-Yu Expressway is 197.3 km. The mean annual ground temperature (MAGT) is higher than -1.5 °C, and permafrost with MAGT lower than -1.5 °C is only distributed in the sections at Bayan Har Mountain and E'la Mountain. There are obvious differences in the distribution of ground ice in the different sections along the engineering corridor. The sections with high ice content are mainly located in Zuimatan, Duogerong Plain and the top of north and south slope of Bayan Har Mountain. The permafrost thickness is controlled by the ground temperature, and permafrost thickness increases with the decrease of the ground temperature, with the change rate of about 37 m/°C. 2) Local factors (topography, landform, vegetation and lithology) affect the degradation process of permafrost, and then affect the distribution, ground temperature, thickness and ice content of permafrost. Asphalt pavement has greatly changed the heat exchange balance of the original ground, resulting in serious degradation of the permafrost. Due to the influence of roadbed direction trend, the phenomenon of shady-sunny slope is very significant in most sections along the line. The warming range of permafrost under the roadbed is gradually smaller with the increase of depth, so the thawing settlement of the shallow section with high ice-content permafrost is more significant.

This study presents a numerical method based on the surface temperature data and the ground temperature increase in Daqing for predicting temperature field distribution in the Binzhou Railway subgrade and analyzing the temporal and spatial distribution of freeze-thaw status of railway subgrade. The calibrated numerical method is applied to simulate the temperature field distribution and roadbed vibrational response of the railway subgrade with a thermal insulation layer at different seasons. The results show the following: (1) The thermal insulation layer can remarkably increase the soil temperature below it and maximum frost depth in the subgrade. (2) Thermal insulation can effectively reduce the subgrade vibration and protect it from frost damage. (3) Given that the strength requirements are met, the insulation layer should be buried as shallow as possible to effectively reduce the subgrade vibration response. The research findings provide theoretical support for the frost damage prevention of railway subgrades in seasonally frozen regions.

Most previous research on areas with abundant rainfall shows that simulations using rainfall-runoff modes have a very high prediction accuracy and applicability when using a back-propagation (BP), feed-forward, multilayer perceptron artificial neural network (ANN). However, in runoff areas with relatively low rainfall or a dry climate, more studies are needed. In these areas—of which oasis-plain areas are a particularly good example—the existence and development of runoff depends largely on that which is generated from alpine regions. Quantitative analysis of the uncertainty of runoff simulation under climate change is the key to improving the utilization and management of water resources in arid areas. Therefore, in this context, three kinds of BP feed-forward, three-layer ANNs with similar structure were chosen as models in this paper. Taking the oasis–plain region traverse by the Qira River Basin in Xinjiang, China, as the research area, the monthly accumulated runoff of the Qira River in the next month was simulated and predicted. The results showed that the training precision of a compact wavelet neural network is low; but from the forecasting results, it could be concluded that the training algorithm can better reflect the whole law of samples. The traditional artificial neural network (TANN) model and radial basis-function neural network (RBFNN) model showed higher accuracy in the training and prediction stage. However, the TANN model, more sensitive to the selection of input variables, requires a large number of numerical simulations to determine the appropriate input variables and the number of hidden-layer neurons. Hence, The RBFNN model is more suitable for the study of such problems. And it can be extended to other similar research arid-oasis areas on the southern edge of the Kunlun Mountains and provides a reference for sustainable water-resource management of arid-oasis areas.