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.

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.

Studying the climatic and environmental changes on different time scales in inland arid regions of Asia can greatly improve our understanding of climatic influences for the Qinghai-Tibet Plateau in the context of global change. Pollen, as a remnant of seed plants, is sensitive to environmental factors including precipitation, temperature and altitude, and is a classic proxy in environmental reconstruction. In the last two decades, great progress in the application of palynology to inland areas of Asia has highlighted the role of palynology in paleoclimatic and paleoenvironmental research. The main progress is as follows. (1) On the tectonic time scale of the late Cenozoic, the palaeoclimatological sequence has been established on the basis of pollen percentage, concentration and taxon. Pollen data have revealed a continuous enhancement of drought in the inland arid region of Asia, in contrast to evidence acquired based on other proxies. (2) In the late Quaternary, an increase in herbaceous plants further supports the intensification of drought associated with global cooling. In more detail, the palynological record shows a glacial-interglacial pattern consistent with changes in global ice volume. (3) The Holocene pollen record has been established at a high resolution and across a wide range of inland areas. In general, it presents an arid grassland environment in the early Holocene, followed by the development of woody plants in the mid- to late-Holocene climate optimum. This pattern is related to moisture changes in areas dominated by the westerlies. There are also significant regional differences in the pattern and amplitude of vegetation response to the Holocene environment. (4) Modern pollen studies based on vegetation surveys, meteorological data and statistics show that topsoil palynology can better reflect regional vegetation types (e.g., grassland, meadow, desert). Drier climates yield higher pollen contents of drought-tolerant plants such as Chenopodioideae, Ephedra, and Nitriaria, while contents of Artemisia and Poaceae are greater under humid climates. Besides these achievements, problems remain in palynological research: for example, pollen extraction, identification, interpretation, and quantitative reconstruction. In the future, we encourage strengthened interdisciplinary cooperation to improve experimental methods and innovation. Firstly, we should strengthen palynological classification and improve the skill of identification; secondly, laboratory experiments are needed to better constrain pollen transport dynamics in water and air; thirdly, more rigorous mathematical principles will improve the reliability of reconstructions and deepen the knowledge of plant geography; and finally, new areas and methods in palynology should be explored, for example DNA, UV-B and isotopic analysis. It is expected that palynology will continue to develop, and we hope it will continue to play an important role in the study of past climatic and environmental changes.

Fossil Taiwania was discovered from the Lower Cretaceous Yixian Formation of Lingyuan City, western Liaoning Province, Northeast China. It is identified as a new species, Taiwania lingyuanensis sp. nov.. The present specimen is preserved as impressions with well defined leaf shoots system and reproductive structures. Leaves are dimorphic, spirally and imbricately arranged. They are scale-like on the main and cone-bearing branchlets, and subulate to falcate-subulate on the juvenile or sterile shoots. The seed cones are singly elliptic, ovate or elongate-ovate and terminally borne on ultimate shoots, bearing 22–24 scale-bracts complexes imbricately and helically arranged around the cone axis, the bracts are broad-ovate, rhomboidal or hexagonal with entire margins. Both the leafy shoots morphology and reproductive structures are similar to extant Taiwania. Furthermore, geological distribution and molecular biological evidences support that Taiwania is probably originated from the eastern Asia at least in the Early Cretaceous and widely distributed in the North Hemisphere thereafter.

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.

The interaction between the cryosphere and atmosphere is an essential and extremely sensitive mutual action process on the earth. Due to global warming and the cryospheric melting, more and more attention has been paid to the interaction process between the cryosphere and atmosphere, especially the feedback of the cryosphere change to the atmosphere. A comprehensive review of the studies on the interaction between the cryosphere and atmosphere is conducted from two aspects: (1) effects of climate change on the cryosphere or responses of the cryosphere to climate change; and (2) feedback of the cryosphere change to the climate. The response of the cryosphere to climate change is lagging. Such a lagging and cumulative effect of temperature rise within the cryosphere have resulted in a rapid change in the cryosphere in the 21st century, and its impacts have become more significant. The feedback from cryosphere change on the climate are omnifarious. Among them, the effects of sea ice loss and snow cover change, especially the Arctic sea ice loss and the Northern Hemisphere snow cover change, are the most prominent. The Arctic amplification (AA) associated with sea ice feedback is disturbing , and the feedback generated by the effect of temperature rise on snow properties in the Northern Hemisphere is also of great concern. There are growing evidence of the impact of the Arctic cryosphere melting on mid-latitude weather and climate. Weakened storm troughs, steered jet stream and amplified planetary waves associated with energy propagation become the key to explaining the links between Arctic cryosphere change and atmospheric circulation. There is still a great deal of uncertainty about how cryosphere change affects the weather and climate through different atmospheric circulation processes at different spatial and temporal scales due to observation and simulation problems.

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.

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 soil-freezing characteristic curve (SFCC), which represents the relationship between unfrozen water content and sub-freezing temperature (or suction at ice-water interface) in a freezing soil, can be used for understanding the transportation of heat, water, and solute in frozen soils. In this paper, the soil freezing process and the similarity between the SFCC of saturated frozen soil and soil-water characteristic curve (SWCC) of unfrozen unsaturated soil are reviewed. Based on similar characteristics between SWCC and SFCC, a conceptual SFCC is drawn for illustrating the main features of soil freezing and thawing processes. Various SFCC expressions from the literature are summarized. Four widely used expressions (i.e., power relationship, exponential relationship, van Genuchten 1980 equation and Fredlund and Xing 1994 equation) are evaluated using published experimental data on four different soils (i.e., sandy loam, silt, clay, and saline silt). Results show that the exponential relationship and van Genuchten (1980) equation are more suitable for sandy soils. The simple power relationship can be used to reasonably best-fit the SFCC for soils with different particle sizes; however, it exhibits limitations when fitting the saline silt data. The Fredlund and Xing (1994) equation is suitable for fitting the SFCCs for all soils studied in this paper.

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.

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.

A series of saline soil-related problems, including salt expansion and collapse, frost heave and thaw settlement, threaten the safety of the road traffic and the built infrastructure in cold regions. This article presents a comprehensive review of the physical and mechanical properties, salt migration mechanisms of saline soil in cold environment, and the countermeasures in practice. It is organized as follows: (1) The basic physical characteristics; (2) The strength criteria and constitutive models; (3) Water and salt migration characteristics and mechanisms; and (4) Countermeasures of frost heave and salt expansion. The review provides a holistic perspective for recent progress in the strength characteristics, mechanisms of frost heave and salt expansion, engineering countermeasures of saline soil in cold regions. Future research is proposed on issues such as the effects of salt erosion on concrete and salt corrosion of metal under the joint action of evaporation and freeze-thaw cycles.

The measurement of pile axial load is of great significance to determining pile foundation design parameters such as skin friction and end bearing capacity and analyzing load transfer mechanisms. Affected by the temperature and ice content of frozen ground, the interface contact relationship between pile foundation and frozen soil is complicated, making pile axial load measurements more uncertain than that in non-frozen ground. Therefore, it is necessary to gain an in-depth understanding of the current pile axial load test methods. Four methods are systematically reviewed: vibrating wire sensors, strain gauges, sliding micrometers, and optical fiber strain sensors. At the same time, the applicability of the four test methods in frozen soil regions is discussed in detail. The first two methods are mature and commonly used. The sliding micrometer is only suitable for short-term measurement. While the Fiber Bragg grating (FBG) strain gauge meets the monitoring requirements, the Brillouin optical time-domain reflectometer (BOTDR) needs further verification. This paper aims to provide a technical reference for selecting and applying different methods in the pile axial load test for the stability study and bearing capacity assessment of pile foundations in cold regions.

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.

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.

Natural disasters inflict severe damage on almost the entire spectrum of social and natural habitats. This ranges from housing and shelter, water, food, health, sanitation to information and communication networks, supply of power and energy, transportation infrastructure, and others. Nepal is a risk prone country for Glacial Lake Outburst Flood (GLOF). GLOFs exist as major challenges as they repeatedly cause a heavy toll of life and property. During such a disaster, major challenges are indeed the protection of life, property and vital life-supporting infrastructure. Any delay or laxity in disaster relief can escalate the magnitude of distress for the victims. Thus, rather than trying to take curative measures, it is better to minimize the impacts of GLOF. These measures subsequently help in reducing the magnitude of death and casualties due to a GLOF event. This reduction of impact is often achieved by optimizing preventive measures. For applying necessary deterrent measures, it is essential to disseminate information about the danger beforehand. Early Warning System (EWS) is an important step for such information dissemination for GLOF disaster management and helps to anticipate the risk of disaster and disseminate information to lives at risk. It is impossible and impractical to reduce all GLOF risks, but it is possible to reduce several impacts of a GLOF through the implementation of the EWS. This paper presents the design and implementation of an EWS for monitoring potential outbursts of a glacier lake in the Dudh-Koshi Basin, Nepal.

Ice documentation and response to prominent warming, especially after the 1990s, is further investigated because it is concerned whether ice records have absence. A δ¹⁸O series of a Laohugou (LHG) shallow ice core (20.12 m) in the northeastern Tibetan Plateau was reconstructed covering the period of 1960-2006. The ice core δ¹⁸O record had significant positive correlations with the warm season (May-September) air temperatures at adjacent meteorological stations and the 500 hPa temperatures in boreal China, indicating that the δ¹⁸O record could be considered a credible proxy of regional temperature. A clear, cold temperature event in 1967 and rapid warming after the 1990s were captured in the LHG δ¹⁸O series, revealing that it could record extreme air-temperature events on both regional and global scales. The LHG δ¹⁸O variations had evident positive correlations with both the summer surface outgoing longwave radiation (OLR) in the Mongolia region and the summer meridional wind at 500 hPa in the LHG region during 1960-2006, suggesting that the increased OLR in the Mongolia region might have intensified the Mongolia Low and expanded the pressure gradient to the LHG region (the Shulehe High), which would have pushed the westerlies further north and suppressed southward incursions of cold air into the LHG region, and thus augmented the temperature rise. The regional atmospheric circulation difference (1985-2006 minus 1960-1984) suggested that the anticyclone in the Mongolia region might have developed the easterly wind, which transported warmer air from the east toward the LHG region and weakened the cold penetration of the westerlies, resulting in the temperature rise since the middle 1980s.

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.

As a linkage between plants and soil, litter decomposition and its effect on nutrient recirculation have an important ecological significance as they contribute to soil structure improvement and the restoration of degraded ecosystems. Fragile ecosystems in arid regions (both hot and cold) are depleted in soil organic matter, and as a result of various factors their circulation of material and energy is slower. Here we discuss how litter decomposition is necessary to maintain the stability of fragile ecosystems. We reviewed research on litter decomposition carried out in arid regions. Our objective in this review is to outline how litter decomposition, and the subsequent buildup of organic matter in soil, is a key process determining the stability of fragile ecosystems. Our review shows that existing studies have focused on the influence of single ecological factors on litter decomposition and nutrient cycling, and highlights how the exploration of interactions among factors determining litter decomposition is still lacking. This interaction is a key aspect, since in the real world, decomposition and nutrient return to soil of litter products is affected by multiple factors. We propose a network setup on a cross-regional scale using standardized methods (e.g., the tea bag method) to understand litter decomposition and nutrient return in fragile ecosystems. Such a unique network could contribute to establish predictive models suitable for litter decomposition and nutrient return in these areas, and thus could provide theoretical and practical support for regional ecological protection and high-quality development.

As one of the five components of Earth's climatic system, the cryosphere has been undergoing rapid shrinking due to global warming. Studies on the formation, evolution, distribution and dynamics of cryospheric components and their interactions with the human system are of increasing importance to society. In recent decades, the mass loss of glaciers, including the Greenland and Antarctic ice sheets, has accelerated. The extent of sea ice and snow cover has been shrinking, and permafrost has been degrading. The main sustainable development goals in cryospheric regions have been impacted. The shrinking of the cryosphere results in sea-level rise, which is currently affecting, or is soon expected to affect, 17 coastal megacities and some small island countries. In East Asia, South Asia and North America, climate anomalies are closely related to the extent of Arctic sea ice and snow cover in the Northern Hemisphere. Increasing freshwater melting from the ice sheets and sea ice may be one reason for the slowdown in Atlantic meridional overturning circulation in the Arctic and Southern Oceans. The foundations of ports and infrastructure in the circum-Arctic permafrost regions suffer from the consequences of permafrost degradation. In high plateaus and mountainous regions, the cryosphere's shrinking has led to fluctuations in river runoff, caused water shortages and increased flooding risks in certain areas. These changes in cryospheric components have shown significant heterogeneity at different temporal and spatial scales. Our results suggest that the quantitative evaluation of future changes in the cryosphere still needs to be improved by enhancing existing observations and model simulations. Theoretical and methodological innovations are required to strengthen social economies' resilience to the impact of cryospheric change.

The Tibetan Plateau (TP) has powerful dynamics and thermal effects, which makes the interaction between its land and atmosphere significantly affect climate and environment in the regional or global area. By retrospecting the latest research progress in the simulation of land-surface processes (LSPs) over the past 20 years, this study discusses both the simulation ability of land-surface models (LSMs) and the modification of parameterization schemes from two perspectives, the models' applicability and improved parameterization schemes. Our review suggests that different LSMs can well capture the spatiotemporal variations of the physical quantities of LSPs; but none of them can be fully applied to the plateau, meaning that all need to be revised according to the characteristics specific to the TP. Avoiding the unstable iterative computation and determining the freeze?thaw critical temperature according to the thermodynamic equilibrium equation, the unreasonable freeze?thaw parameterization scheme can be improved. Due to the complex underlying surface of the TP, no parameterization scheme of roughness length can well simulate the various characteristics of the turbulent flux over the TP at different temporal scales. The uniform soil thermodynamic and hydraulic parameterization scheme is unreasonable when it is applied to the plateau, as a result of the strong soil heterogeneity. There is little research on the snow-cover process so far, and the improved scheme has no advantage over the original one due to the lack of some related physical processes. The constant interaction among subprocesses of LSPs makes the improvement of a multiparameterization scheme yield better simulation results. According to the review of existing research, adding high-quality observation stations, developing a parameterization scheme suitable for the special LSPs of the TP, and adjusting the model structures can be helpful to the simulation of LSPs on the TP.

Numerical simulation is known as an effective method for mechanical properties during frozen soil excavation. In order to reveal the development of cutting force, effective stress and cutting fragments in frozen silt during the cutting process, we introduce an explicit finite element program LS-DYNA to establish a two-dimensional numerical model of the frozen soil cut. We also use the Holmquist-Johnson-Cook (HJC) damage constitutive model for simulating the variation of soil mechanical properties according to the strong dependence between the cutting tool and frozen silt during the process with different cutting depths, angles and velocities. Meanwhile, a series of experimental results are acquired of frozen silt cutting to prove the application of the HJC model during simulation of cutting force variations. The result shows that the cutting force and fragment size are strongly influenced by cutting depths and cutting velocities increased, and the maximum effective stress at points where the tool contacts frozen soil during the cutting process. In addition, when the cutting angle is 52°, the cutting force is the smallest, and the cutting angle is optimum. Thus, the prediction of frozen soil mechanical properties on the cutting process by this model is conducive to selecting machinery equipment in the field.

Ecophysiological responses to drought stress of Populus euphratica in Alashan Desert Eco-hydrology Experimental Research Station were investigated. Results show that under mild and moderate drought stress, stomatal length, aperture, area and density is likely to decrease in the early days, but afterwards this is likely to recovery with treatment over the passage of treatment time. Under severe drought stress, these properties appear to decline continuously. However, after 45 days of drought-stress treatment, the decline is not as noticeable as before, indicating that Populus euphratica could possibly reduce water evaporation by shutting down the stoma, leading to an improvement in its water use efficiency with better survival under drought stress conditions. The leaf area first decreases, and then increases under mild and moderate drought stress conditions, with the average values under different degree of stress found to be approximately 129.52, 120.08, 116.63 and 107.28 cm², respectively. Under moderate stress conditions, the leaf water potential appears to show a continuous decline where the average values under different degree of stress are found to be -1.27, -1.85, -4.29 and -4.80 MPa, respectively. In terms of proline content, the results demonstrate that this factor appears to increase significantly under moderate and severe drought stress conditions. Especially under severe drought stress condition, the content is found to be more than 700 μg/g. Ranging over average values of 14.64 and 15.90 nmol/g under moderate and severe drought stress, respectively, Malondialdehyde content is found to increase quite rapidly under moderate and severe drought stress conditions at first, which then appears to decrease gradually with the treatment over time.

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).

It is feasible to study the mechanical characteristics of coarse-grained soil by simulated granular materials such as glass beads. In this paper, 3 mm diameter glass beads are used to conduct drained and undrained triaxial tests under the condition of different confining pressures to explore their strength, deformation and critical state characteristics. Specifically, the influence of drainage and confining pressure on the stick-slip phenomenon of glass beads is reported. The experimental findings from triaxial tests show that the stress-strain relationship of glass beads softens when the confining pressure is high. Under the undrained condition, the initial modulus increases with the increase in the confining pressure. In contrast, it is not significantly affected by the confining pressure under the drained condition. It is quite evident that the glass beads hardly contract during the shearing process, and their stress path is approximately a segmented straight line. The slope of the critical state line under the undrained condition is greater than that under the drained condition, and the friction angle of the glass beads under the undrained and drained conditions is calculated to be 28.1° and 29.5°, respectively. The phenomenon of stick-slip has been depicted for the different test conditions, and the stick-slip amplitude linearly increases with the confining pressure, especially in the undrained condition. It is also found that the maximum energy released from the phenomenon of stick-slip increases linearly with the confining pressure.

Microbes inhabiting the desert respond sensitively to environmental changes and may be an indicator for changes in the desert ecosystem. Hypolithic microbial communities in the desert play a vital role in ecosystem processes such as soil formation and organic matter accumulation. This study investigated and compared the culturable bacterial community structure and diversity in hypolithic and peripheral soils, and the interaction between bacteria and environmental factors. The bacteria were isolated using four different kinds of media and identified by 16S rRNA gene-sequence analysis. The numbers of culturable bacteria in the hypolithic and peripheral soils ranged from 3.0×10⁴ to 3.6×10⁵ CFU/g and from 6.5×10⁴ to 5.3×10⁵ CFU/g, respectively, indicating that the bacteria number in peripheral soil was higher than that in hypolithic soil. A total of 98 species belonging to 34 genera were identified, among which Arthrobacter, Bacillus,and Streptomyces were found dominantly and widely distributed. The community of culturable bacteria had obvious sample specificity, and the diversity in hypolithic soil was higher than that in peripheral soil. On the regional scale, the distribution of culturable bacteria and the environmental factors showed regular changes. On the local scale, the high heterogeneity of the hypolithic environment determined the specificity of the number and species of culturable bacteria.

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.

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%.

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.

Recent years have seen a large number of high-speed railways built and will be built in seasonal frozen soil regions of China. Although high-speed railways are characterized by being fast, comfortable and safe, higher standards for deformation of the railways' frozen subgrade are required. Meanwhile, changes in subgrade soil temperatures are the main factors affecting the deformation of frozen subgrade. Therefore, this paper selected typical test subgrade sections of the Harbin-Qiqihar Line, a special line for passenger transport built in the deep seasonal frozen soil regions of China, to monitor field temperatures. Also, the temperature changing laws of railways' subgrade in this region was analyzed by using testing data, the aim of which is to provide a technical support for future design and construction of buildings and structures in a deep seasonal frozen soil region.

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.

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.

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.

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.

Timely removal of the flower is a key agricultural measure to ensure the concentrated supply of nutrients for the growth of underground bulbs and to increase the yield of lilies. Removing flowers and returning them to the field is one of the traditional ways of treatment, and field litter is formed at this time. Previous study showed that the decomposition of litter changes the soil properties. In order to study the effects of lily litter decomposition on soil physical and chemical properties and microbial structure, three treatments were set up in reference to the Decomposition Bag Method: control (CK), Lanzhou lily flower treatment (LZF), and Zhongbai No.1 flower treatment (ZBF). The effects of lily decomposition on soil physical and chemical properties and microbial community composition were studied in order to provide a scientific basis and theoretical guidance for the planting process of Lanzhou lily. The results show that the decomposition of lily flowers significantly increased the contents of soil organic matter, soil total nitrogen, soil total phosphorus and soil available potassium, and decreased soil pH. RDA shows that soil available nutrients and pH were the driving factors for the change of the soil microbial community. A short-term change of soil microenvironment caused by the decomposed lily flower is beneficial to growing the Lanzhou lily. However, under the correlation analysis of environmental factors, the long-term effects of returning the Lanzhou lily flower to the field, such as the trend of soil acidification, need to be further studied.

A total of 71,177 glaciers exist on the Qinghai-Tibet Plateau, according to the Randolph Glacier Inventory (RGI 6.0). Despite their large number, glacier ice thickness data are relatively scarce. This study utilizes digital elevation model data and ground-penetrating radar thickness measurements to estimate the distribution and variation of ice thickness of the Longbasaba Glacier using Glacier bed Topography (GlabTop), a full-width expansion model, and the Huss and Farinotti (HF) model. Results show that the average absolute deviations of GlabTop, the full-width expansion model, and the HF model are 9.8, 15.5, and 10.9 m, respectively, indicating that GlabTop performs the best in simulating glacier thickness distribution. During 1980-2015, the Longbasaba Glacier thinned by an average of 7.9±1.3 m or 0.23±0.04 m/a, and its ice volume shrunk by 0.28±0.04 km³ with an average reduction rate of 0.0081±0.0001 km³/a. In the investigation period, the area and volume of Longbasaba Lake expanded at rates of 0.12±0.01 km²/a and 0.0132±0.0018 km³/a, respectively. This proglacial lake could potentially extend up to 5,000 m from the lake dam.

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.

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.

In this study, in-situ testing results are given, and the analytical relationship of the vibrations' amplitudes inside an embankment by the thawing of the subgrade surface of seasonably deep frozen soils is provided. The peculiarities of the vibration waves' propagation during the springtime thawing of soils compared to those during the summertime period and the correlation of the vibrations with the under-rail basement modulus of elasticity are defined.

Despite the enormous applications of photosynthesis in global carbon budget and food security, photosynthesis research has not been adequately explored as a research focus in Nigeria. Previous works on C₃ and C₄ plants in Nigeria were mainly on the use of anatomical characteristics to delimit plant species into their respective pathways, with no attention being paid to its applications. In this review, past and present knowledge gaps in this area of study are elucidated. Information used in this review were sourced from referred research articles and books in reputable journals. The results revealed that C₃ and C₄ plants are distributed among 21 genera and 11 families in Nigeria. In addition there is dearth of informatio such that only three genera have been classified based on diverse photosynthetic pathways with no information found on the physiological and biochemical characterization of these genera. Moreover, further research is also suggested for tackling new challenges in the area of food productivity and climate change.