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.

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.

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.

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.

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.

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.

The original landform along the China-Russia Crude Oil Pipeline (CRCOP, line 2) was disturbed during installation of pavement for the pipeline. Forest and vegetation coverage is dense, and runoff develops along the pipe. Since the operation of the CRCOP (line 2) began in 2018, ponding has appeared on both sides of the pipeline. If there is no drainage, ponding can hardly dissipate, due to the low permeability of the permafrost layer. With the supply of surface flow and the transportation of oil at positive temperatures, ponding promotes an increase in temperature and changes the boundary thermal conditions of the pipeline. Meanwhile, when the ponding freezes and thaws, frost heave threatens operational safety of the pipeline. Furthermore, the ponding can affect the thermal condition of line 1. In this paper, the distribution of ponding along the CRCOP was obtained by field investigation. The type and cause of ponding were summarized, and the catchment and stream order were extracted by the Digital Elevation Model (DEM). According to the statistical results in attributes for topographic factors, it is known that ponding along the pipeline is relative to elevation, slope, aspect, and the Topographic Wetness Index (TWI). Water easily accumulates at altitudes of 300-450 m, slopes within 3°-5°, aspect in the northeast or south, TWI within 13-16, flow direction in north-east-south, and flow length within 90-150 km. This paper proposes a theoretical basis for the cause and characteristics of ponding along the pipeline.

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.

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 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.

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.

The glaciers of the Hengduan Mountains play an important role in the hydrology processes of this region.In this study,the HBV Light model,which relies on a degree-day model to simulate glacier melting,was employed to simulate both glacier runoff and total runoff.The daily temperature and precipitation at the Hailuo Creek No.1 Glacier from 1952 to 2009 were obtained from daily meteorological observed data at the glacier and from six national meteorological stations near the Hailuo Creek Basin.The daily air temperature,precipitation,runoff depth,and monthly potential evaporation in 1995,1996,and 2002 were used to obtain a set of optimal parameters,and the annual total runoff and glacier runoff of the Hailuo Creek Glacier (1952-2009) were calculated using the HBV Light model.Results showed the average annual runoff in the Hailuo Creek Basin was 2,114 mm from 1952 to 2009,of which glacial melting accounted for about 1,078 mm.The river runoff in the Hailuo Creek catchment increased as a result of increased glacier runoff.Glacier runoff accounted for 51.1% of the Hailuo Creek stream flow in 1994 and increased to 72.6% in 2006.About 95% of the increased stream flow derived from the increased glacier runoff.

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.

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.

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.

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.

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.

In semi-arid areas of China, gravel and sand mulch is a farming technique with a long history. In this study, a sample survey was conducted on long term gravel sand mulch observational fields in the Northwest Loess Plateau to determine the effects of long term mulch on soil microbial and soil enzyme activities. We found that after long term gravel-sand mulch, compared with bare ground, soil organic matter, alkali nitrogen, conductivity decreased, while pH and soil moisture increased. Urease, saccharase and catalase decreased with increased mulch thickness, while alkaline phosphatase was reversed. The results of Illumina MiSeq sequencing shows that after gravel-sand mulch, the bacterial and fungal community structure was different from bare land, and the diversity was reduced. Compared with bare land, the bacteria Proteobacteria and Acidobacteria abundance increased with increased thickness, and Actinobacteria was opposite. Also, at the fungal genus level, Fusarium abundance was significantly reduced, and Remersonia was significantly increased, compared with bare land. Redundancy analysis (RDA) revealed that soil environmental factors were important drivers of bacterial community changes. Overall, this study revealed some of the reasons for soil degradation after long term gravel-sand mulch. Therefore, it is recommended that the addition of exogenous soil nutrients after long term gravel-sand can help improve soil quality.

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.

In saline soil areas, there are a large number of ions in soil or water environments, such as Cl^- and SO₄^2-, which have strong corrosive interactions with buildings. To study the deterioration of non-dispersible underwater concrete in sulfate, chloride, and mixed salt environments, the compressive strength and deterioration resistance coefficient of the studied concrete mixed with different amounts of ground granulated blast-furnace slag (GGBS) were analyzed in this paper. At the same time, the micro morphology and corrosion products distribution of the studied concrete were observed by means of SEM, plus XRD diffraction, TG-DTG and FT-IR analyses to explore the influence of corrosive solutions on the hydration products of concrete. We also analyzed the mechanism of improving the deterioration resistance of the studied concrete by adding GGBS in a saline soil environment. The results show that the compressive strength of the studied concrete in a chloride environment was close to that in a fresh water environment, which means that chloride has no adverse effect on compressive strength. The deterioration of the studied concrete was most serious in a sulfate environment, followed by mixed salt environment, and the lowest in a chloride environment. In addition, by adding GGBS, the compressive strength and deterioration resistance of the studied concrete could be effectively improved.

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.

Transport structures built throughout the period from 1960 to 1980 in permafrost regions based on the principle of permafrost preservation are subject to deformations. In many cases, the reason is a gradual change in temperature and their subgrade condition within the active zone due to the structures' technogenic impact. Design solutions for the fifty-year-old structures fail to ensure in all cases their reliable operation at the present time. The greatest danger to the reliable operation of railway lines in cold regions is uneven deformations of bridges, which are barrier places. Therefore, the solution to this problem is urgent especially due to the necessity of increase carrying capacity. The purpose of this study is to increase reliability of bridge operation in cold regions through strengthening the subgrade by reinforcement with injection of solidifying solutions. The problem of uneven deformations due to permafrost degradation is considered using the example of a railway bridge located in the northern line of the Krasnoyarsk railway. Deformations of the bridge abutments began immediately after the construction was completed and the bridge was open for traffic-since 1977. Permafrost degradation was developing more actively straight under the abutments due to higher thermal conductivity of the piles concrete. Notably, thawing intensity of frozen soils under the bridge abutments is uneven due to its orientation to the cardinal points. The analysis of archive materials and results of the geodetic survey made it possible to systematize the features of augmenting deformations of each abutment over time. The engineering-geological survey with drilling wells near the abutments ensured determination of soil characteristics, both in the frozen and thawed states. Thermometric wells were arranged to measure temperatures. The analysis and systematization of the data obtained allowed us to develop geotechnical models for each abutment of the bridge. The peculiarity of these models is allowance for changes in the strength and deformation characteristics of the soil calculated layers depending on changes in temperature and the soil condition. Thus, different calculated geological elements with the corresponding strength and deformation characteristics were identified in the soil layers of the same origin. The analysis of the systematized geodetic data allowed us to confirm adequacy of the developed geotechnical models. Studies carried out using geotechnical models made it possible to predict improvement of physical and mechanical characteristics of the subgrade to prevent further growth deformations of the bridge abutments. The method of reinforcement by injection is proposed. Injecting a solution under pressure leads to strengthening of weakened thawed soils and improving their physical and mechanical properties. This research theoretically substantiates and develops the geotechnical models of the reinforced pier footing of bridge abutments by injection of solidifying solutions. The models take into account the reinforcement parameters and elements for the case in question. The influence of reinforcement on the change in physical and mechanical properties of the soil mass is determined.

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.

Distribution of rainfall event sizes and interval lengths between events are important characteristics of arid and semi-arid climates. Understanding their importance will contribute to our ability to understand ecosystem dynamics in these regions. Rainfall event timing and magnitude are important drivers of ecosystem processes and are instrumental in creating landscape heterogeneity in arid and semi-arid regions. Rainfall event characteristics were analyzed using an automatic tipping-bucket rain-gauge record across the entire summer monsoon season from 2008 to 2015 at the arid desert area of Shapotou in the Tengger Desert, China. Changing the minimum inter-event time (MIT) from 30 min to 24 h alters the number of rainfall events from 64 to 25 for the event depth larger than 0.1 mm. The mean rainfall intensity declined from 0.95 mm/h to 0.53 mm/h, and the geometric mean event duration rose from 0.55 h to 4.4 h. The number of rainfall events, mean rainfall intensity, and geometric mean event duration differed under different criteria of individual rainfall depths, except that for an individual rainfall depth of 0.5, 1.0, and 5.0 mm. The aforementioned features differed only at the lowest range of the mean rainfall intensity and depth for MIT=3 and 6 h. These findings suggest that identification of event-based rainfall in this specific arid region can be better achieved by setting the MIT at six hours. The wide variation in rainfall event properties indicate the need for paying more attention to the proper selection and reporting of event criteria in studies that adopt event-based data analysis. This is especially true in quantifying effective rainfall for soil water replenishment in terms of rainfall depth and intensity with infrequent rainfall events.

Reed is one of the most frequent and dominant species in wetlands all over the world, with common reed (Phragmites australis (Cav.) Trin. ex Steud.) as the most widely distributed species. In many wetlands, P. australis plays a highly ambivalent role. On the one hand, in many wetlands it purifies wastewater, provides habitat for numerous species, and is a potentially valuable raw material, while on the other hand it is an invasive species which expands aggressively, prevents fishing, blocks ditches and waterways, and builds monospecies stands. This paper uses the eutrophic reed-swamp of Wuliangsuhai Lake in Inner Mongolia, northern China, as a case to present the multiple benefits of regular reed cutting. The reed area and aboveground biomass production are calculated based on field data. Combined with data about water and reed nutrient content, the impact of reed cutting on the lake nutrient budget (N and P) is investigated. Currently, at this lake around 100,000 tons of reed are harvested in winter annually, removing 16% and 8% of the total nitrogen and phosphorus influx, respectively. Harvesting all available winter reed could increase the nutrient removal rates to 48% and 24%, respectively. We also consider the effects of summer harvesting, in which reed biomass removal could overcompensate for the nutrient influx but could potentially reduce reed regrowth.

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.

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.

The moisture content of a road subgrade in cold regions will increase after freeze-thaw cycles, resulting in subgrade strength and stiffness losses. Electroosmosis is widely used in treating saturated soft soils to decrease the moisture content. The induced moisture migration during electroosmosis in unsaturated soil is much more complex than that of saturated soil because of a series of nonlinear changes in soil properties. This study first uses an exponential function to characterize the relationship between electroosmotic permeability and saturation degree. Then, a one-dimensional model is developed to simulate the electroosmosis-induced moisture migration in unsaturated soil. Simulation results show that electroosmosis reduces the saturation degree of the unsaturated soil, indicating that it can be applied to subgrade dewatering. Key parameters such as soil pore size distribution coefficient, air entry value, and effective voltage significantly affect moisture migration. Electroosmotic properties of unsaturated soils are extremely important to the efficiency of electroosmosis.

The active-layer soils overlying the permafrost are the most thermodynamically active zone of rock or soil and play important roles in the earth-atmosphere energy system. The processes of thawing and freezing and their associated complex hydrothermal coupling can significantly affect variation in mean annual temperatures and the formation of ground ice in permafrost regions. Using soil-temperature and -moisture data obtained from the active layer between September 2011 and October 2014 in the permafrost region of the Nanweng'he River in the Da Xing'anling Mountains, the freeze-thaw characteristics of the permafrost were studied. Based on analysis of ground-temperature variation and hydrothermal transport characteristics, the thawing and freezing processes of the active layer were divided into three stages: (1) autumn-winter freezing, (2) winter freeze-up, and (3) spring-summer thawing. Variations in the soil temperature and moisture were analyzed during each stage of the freeze-thaw process, and the effects of the soil moisture and ground vegetation on the freeze-thaw are discussed in this paper. The study's results show that thawing in the active layer was unidirectional, while the ground freezing was bidirectional (upward from the bottom of the active layer and downward from the ground surface). During the annual freeze-thaw cycle, the migration of soil moisture had different characteristics at different stages. In general, during a freezing-thawing cycle, the soil-water molecules migrate downward, i.e., soil moisture transports from the entire active layer to the upper limit of the permafrost. In the meantime, freeze-thaw in the active layer can be significantly affected by the soil-moisture content and vegetation.

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.

Based on Landsat MSS/TM/OLI remote sensing images, glaciers vector data in the Qaidam Basin were extracted for 1977, 2002, and 2018, and their spatial-temporal variations were analyzed. Results show that there were 2,050 glaciers covering an area of 1,693.54±40.96 km² and having an ice volume of 108.65±2.43 km³ in the Qaidam Basin in 2018. Glaciers with areas <1.0 km² accounted for the largest number, while glaciers with areas of 1.0-5.0 km² accounted for the most glacierized area. In the past 50 years, the number of glaciers decreased by 177, and the glacier area and volume reduced by 338.08 km² (-8.12 km²/a) and 19.92 km³ (-0.48 km³/a), respectively. Retreat altitudes of glaciers were concentrated at 4,900-5,600 m, 4,700-5,200 m, and 5,000-5,600 m and reduced areas accounted for 95.53%, 77.80%, and 69.19% in the Kunlun, Qilian, and Altun mountains, respectively. The area of north-oriented glaciers decreased the most (-125.43 km²), but the west- and east-oriented glaciers retreated at the fastest rate (i.e., -27.11% and -27.10%). All glaciers showed a decreasing trend in sub-regions of the Qaidam Basin from 1977 to 2018. The decreasing trend was accelerated gradually from northwest to southeast in the northern part of the basin, while glacier change was the smallest in the middle section and gradually accelerated towards both ends of the basin's southern part. The temperature had continued to rise, and the precipitation had increased slowly in the Qaidam Basin during the past 50 years. The continuous rise in air temperature was the main reason for the retreat of glaciers.

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.

Drought is a major production constraint for major fruits and vegetable crops in the tropics.This study was conducted to investigate the effect of limited water supply at three growth stages (vegetative,flowering and fruiting) on the accumulation of proline and soluble sugars in three pepper species.Seeds of the three pepper species,Capsicum chinense Jacq.,C.annuum L.and C.frutescens L.were raised in a nursery and the seedlings were transplanted into seventy two plastic pots arranged in a randomized complete block design with three replicates,25 days after planting.Four water treatments,200 mL of water supplied twice daily (W₁),once in every three days (W₂),once in every five days (W₃),and zero water supplied throughout growing period (W₀) were imposed at three vegetative,flowering,and fruiting growth stages.Data were collected on relative water content,free proline and total soluble sugar.Data collected were subjected to analysis of variance and means were separated using Duncan's multiple range test.Results show that the concentration of proline and soluble sugar in leaves of the three pepper species were found to be remarkable at the different stages of growth in the stressed plants.

Satellite remote sensing is widely used to estimate snow depth and snow water equivalent (SWE) which are two key parameters in global and regional climatic and hydrological systems. Remote sensing techniques for snow depth mainly include passive microwave remote sensing, Synthetic Aperture Radar (SAR), Interferometric SAR (InSAR) and Lidar. Among them, passive microwave remote sensing is the most efficient way to estimate large scale snow depth due to its long time series data and high temporal frequency. Passive microwave remote sensing was utilized to monitor snow depth starting in 1978 when Nimbus-7 satellite with Scanning Multichannel Microwave Radiometer (SMMR) freely provided multi-frequency passive microwave data. SAR was found to have ability to detecting snow depth in 1980s, but was not used for satellite active microwave remote sensing until 2000. Satellite Lidar was utilized to detect snow depth since the later period of 2000s. The estimation of snow depth from space has experienced significant progress during the last 40 years. However, challenges or uncertainties still exist for snow depth estimation from space. In this study, we review the main space remote sensing techniques of snow depth retrieval. Typical algorithms and their principles are described, and problems or disadvantages of these algorithms are discussed. It was found that snow depth retrieval in mountainous area is a big challenge for satellite remote sensing due to complicated topography. With increasing number of freely available SAR data, future new methods combing passive and active microwave remote sensing are needed for improving the retrieval accuracy of snow depth in mountainous areas.

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.

Spatial heterogeneity is an inherent characteristic of natural forest landscapes, therefore estimation of structural variability, including the collection and analyzing of field measurements, is a growing challenge for monitoring wildlife habitat diversity and ecosystem sustainability. In this study, we investigated the combined influence of plot shape and size on the accuracy of assessment of conventional and rare structural features in two young-growth spruce-dominated forests in northwestern China. We used a series of inventory schemes and analytical approaches. Our data showed that options for sampling protocols, especially the selection of plot size considered in structural attributes measurement, dramatically affect the minimum number of plots required to meet a certain accuracy criteria. The degree of influence of plot shape is related to survey objectives; thus, effects of plot shape differ for evaluations of the "mean" or "representative" stand structural conditions from that for the range of habitat (in extreme values). Results of Monte Carlo simulations suggested that plot sizes <0.1 ha could be the most efficient way to sample for conventional characteristics (features with relative constancy within a site, such as stem density). Also, 0.25 ha or even larger plots may have a greater likelihood of capturing rare structural attributes (features possessing high randomness and spatial heterogeneity, such as volume of coarse woody debris) in our forest type. These findings have important implications for advisable sampling protocol (plot size and shape) to adequately capture information on forest habitat structure and diversity; such efforts must be based on a clear definition of which types are structural attributes to measure.

Solar energy is clean and renewable energy that plays an important role in mitigating impacts of environmental problems and climate change. Solar radiation received on the earth's surface determines the efficiency of power generation and the location and layout of photovoltaic arrays. In this paper, the average daily solar radiation of 77 stations in China from 1957 to 2016 was analyzed in terms of spatial and temporal characteristics. The results indicate that Xinjiang, the Qinghai-Tibet Plateau, North, Central and East China show a decreasing trend with an average of 2.54×10^-3 MJ/(m²?10a), while Northwest and Northeast China are basically stabilized, and Southwest China shows a clear increasing trend with an average increase of 1.79×10^-3 MJ/(m²?10a). The average daily solar radiation in summer and winter in China from 1957 to 2016 was 18.74 MJ/m² and 9.09 MJ/m², respectively. Except for spring in Northwest, East and South China, and summer in northeast China, the average daily solar radiation in all other regions show a downward trend. A critical point for the change is 1983 in the average daily solar radiation. Meanwhile, large-scale (25-30 years) oscillation changes are more obvious, while small-scale (5-10 years) changes are stable and have a global scope. The average daily solar radiation shows an increasing-decreasing gradient from west to east, which can be divided into three areas west of 80°E, 80°E-100°E and east of 100°E. The average daily solar radiation was 2.07 MJ/m² in the 1980s, and that in 1990s lower than that in the 1960s and the 1970s. The average daily solar radiation has rebounded in the 21st century, but overall it is still lower than the average daily solar radiation from 1957 to 2016 (13.87 MJ/m²).

Estimation of the influence of snow grain size and black carbon on albedo is essential in obtaining the accurate albedo. In this paper, field measurement data, including snow grain size, snow depth and density was obtained. Black carbon samples were collected from the snow surface. A simultaneous observation using Analytical Spectral Devices was employed in the Qiyi Glacier located in the Qilian Mountain. Analytical Spectral Devices spectrum data were used to analyze spectral reflectance of snow for different grain size and black carbon content. The measurements were compared with the results obtained from the Snow, Ice, and Aerosol Radiation model, and the simulation was found to correlate well with the observed data. However, the simulated albedo was near to 0.98 times of the measured albedo, so the other factors were assumed to be constant using the corrected Snow, Ice, and Aerosol Radiation model to estimate the influence of measured snow grain size and black carbon on albedo. Field measurements were controlled to fit the relationship between the snow grain size and black carbon in order to estimate the influence of these factors on the snow albedo.

In recent years, land use and land cover have under gone tremendous change on the Loess Plateau, leading to temporal and spatial variation over many ecological factors, such as carbon storage. Based on four series of land-use data from remote-sensing imaging, spatiotemporal changes of land-use types and volume changes were analyzed. Combined with carbon-stock-assessment modules of the InVEST (integrated valuation ecosystem services and tradeoffs) model, the carbon-storage change was estimated and analyzed at the subcounty and subbasin scales. The results show that (1) cultivated land and grassland area decreased, while woodland and urban land area increased in northern Shaanxi; (2) the average carbon storage in Huangling County and the Beiluo River Basin is the largest, while that of Yuyang County and the Xinshui River Basin is the minimum, and that of Wuqi County showed the greatest growth; (3) carbon storage in the study area showed a definite decrease in 2000, but in general has increased from 1995 to 2010; (4) carbon-storage figures of subbasins and counties are all restricted by the natural status and land-use landscape of the whole study area. From the results, it can be seen that the effect of ecological policies is remarkable. This study has important implications for the rational planning of land use, adjustment of the ecosystem carbon cycle, and related policies.