An understanding of soil microbial communities is crucial in roadside soil environmental assessments. The 16S rRNA sequencing of a stressed microbial community in soil adjacent to the Qinghai-Tibet Highway (QTH) revealed that the accumulation of heavy metals (over about 10 years) has affected the diversity of bacterial abundance and microbial community structure. The proximity of a sampling site to the QTH/Qinghai-Tibet Railway (QTR), which is effectively a measure of the density of human engineering, was the dominant factor influencing bacterial community diversity. The diversity of bacterial communities shows that 16S rRNA gene abundance decreased in relation to proximity to the QTH and QTR in both alpine wetland and meadow areas. The dominant phyla across all samples were Actinobacteria and Proteobacteria. The concentration of Cr and Cd in the soil were positively correlated with proximity to the QTH and QTR (MC/WC sampling sites), and Ni, Co, and V were positively correlated with proximity to the QTH and QTR (MA/WA sampling sites). The results presented in this study provide an insight into the relationships among heavy metals and soil microbial communities, and have important implications for assessing and predicting the impacts of human-induced activities from the QTH and QTR in such an extreme and fragile environment.
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.
A series of directional shear tests on remolded frozen soil was carried out at -10 °C by using a hollow cylinder apparatus to study failure criterion under a directional shear-stress path. Directional shear tests were conducted at five shear rates (10, 20, 30, 40, and 50 kPa/min) and five intermediate principal stress coefficients (b=0, 0.25, 0.5, 0.75, and 1), with the mean principal stress (p=4.5 MPa) kept constant. The results show that the torsional strength and the generalized strength both increase with the increase of the shear rates. According to the failure modes of frozen soil under different shear rates, the specimens present obvious plastic failure and shear band; and the torsional shear component dominates the failure modes of hollow cylindrical specimens. A shear rate of 30 kPa/min is chosen as the loading rate in the directional shear tests of frozen soil. The shape of the failure curve in the π plane is dependent on the directional angles α of the major principal stress. It is reasonable to use the strain-hardening curves to define the deviatoric stress value at γg =15% (generalized shear strain) as the failure criterion of frozen soil under a directional shear-stress path.
Hydrology of the high glacierized region in the Tianshan Mountains is an important water resource for arid and semiarid areas of China, even Central Asia. The hydrological process is complex to understand, due to the high variability in climate and the lack of hydrometeorological data. Based on field observations, the present study analyzes the meteorological and hydrological characteristics of the Koxkar Glacier River Basin during 2008-2011; and the factors influencing climate impact on glacier hydrology are discussed. The results show that precipitation at the terminus of the glacier was 426.2 mm, 471.8 mm, 624.9 mm, and 532 mm in 2008, 2009, 2010, and 2011, respectively. Discharge increases starting in May, reaches its highest value in July and August, and then starts to decrease. The mean annual discharge was 118.23×106 m3 during the four years observed, with 87.0% occurring in the ablation season (May-September). During the study period, the runoff in August accounted for 29% of total streamflow, followed by July (22%) and June (14%). The runoff exhibited obviously high interannual variability from April to September, induced by drastic changes in climate factors. Discharge autocorrelations are very high for all the years. The climate factors show different influences on discharge. The highest correlation R between daily temperature and discharge was for a time lag of 2-3 days on the Koxkar Glacier (0.66-0.76). The daily depth of runoff to daily temperature and daily water vapor pressure had an R 2 value of 0.56 and 0.69, respectively, which could be described by an exponential function. A closer relationship is found between runoff and either temperature or water vapor pressure on a monthly scale; the R 2 values are 0.65 and 0.78, respectively. The study helps us to understand the mechanisms of the hydrological-meteorological system of typical regional glaciers and to provide a reference for glacier-runoff simulations and water-resource management.
Vegetation plays a significant role in global terrestrial ecosystems and in combating desertification. We analyzed vegetation change in Inner Mongolia of northern China using the Normalized Difference Vegetation Index (NDVI) from 1998 to 2013, which is an important composite of Chinese National Ecological Security Shelter. The correlation between vegetation growth and drought quantified using the Standardized Precipitation Evapotranspiration Index (SPEI) was also explored. Results show that vegetation in most of the study area has been rehabilitated to various degrees, especially in regions such as most of the Horqin Sandy Land, eastern Ordos Plateau, Hetao Plain, as well as the middle-northern Da Hinggan Ling Mountains. Vegetation improvement in spring was significant in most of the study area. Vegetation degradation was centrally distributed in Xilingol grassland close to the Sino-Mongolia border and abandoned croplands in Ulanqab Meng. Vegetation change trends and seasonal differences varied among different vegetation types. The biggest vegetation variation in the growing season was the belt-like distribution along those grasslands close to the precipitation isoline of 200 mm and the Sino-Mongolia border, but also variation in summer and autumn exist in obvious spatial differences between grasslands and forests. Drought largely influenced vegetation change of Inner Mongolia at 6-month scale or 12-month scale, except for forests of eastern Hunlun Buir Meng and deserts or gobi deserts of western Alxa Meng. Moreover, drought in the previous winter and early spring seasons had a lag effect on growing-season vegetation. Desert grassland was the most easily affected by drought in the study area. Anthropogenic activities have made great progress in improving local vegetation under the lasting drought background.
In this study, in-situ soil moisture measurements are used to evaluate the accuracy of three AMSR-E soil moisture products from NASA (National Aeronautics and Space Administration), JAXA (Japanese Aerospace Exploration Agency) and VUA (Vrije University Amsterdam and NASA) over Maqu County, Source Area of the Yellow River (SAYR), China. Results show that the VUA soil moisture product performs the best among the three AMSR-E soil moisture products in the study area, with a minimum RMSE (root mean square error) of 0.08 (0.10) m3/m3 and smallest absolute error of 0.07 (0.08) m3/m3 at the grassland area with ascending (descending) data. Therefore, the VUA soil moisture product is used to describe the spatial variation of soil moisture during the 2010 growing season over SAYR. The VUA soil moisture product shows that soil moisture presents a declining trend from east south (0.42 m3/m3) to west north (0.23 m3/m3), with good agreement with a general precipitation distribution. The center of SAYR presents extreme wetness (0.60 m3/m3) during the whole study period, especially in July, while the head of SAYR presents a high level soil moisture (0.23 m3/m3) in July, August and September.
Spatial and temporal variations in moisture conditions across monsoon Asia were investigated using 347 Monsoon Asia Drought Atlas (MADA) grid points and 100 Chinese historical documents sites during the years 1470-2000. We applied Rotated Empirical Orthogonal Function (REOF) analysis to evaluate spatial moisture variability during the past 530 years. The first 13 principal components together explained 61.35% of the total variance, with the First Principal Component (PC1) accounting for 14.1%. After varimax rotation to the first 13 EOFs, we obtained new time series and spatial patterns. These patterns divided monsoon Asia into 13 regions with coherent moisture variability. Drought events were analyzed within these 13 regions. The results indicate that there has been a prominent drying trend in eastern and central Mongolia, Southeast Asia and east China during the last 50 years. Conversely, India and the Tibetan Plateau show a significant increase in moisture around the late 20th century. We found four drought periods, A.D. 1625-1644, A.D. 1710-1729, A.D. 1920s, and A.D. 1975-1999 occurred widely across monsoon Asia during the past 530 years. On inter-annual time scales, moisture variations in the northwest region of monsoon Asia, the Indian subcontinent and Southeast Asia are influenced by the El Ni?o-Southern Oscillation (ENSO). Thirty-year running correlation coefficient diagnostic analysis revealed that moisture variability in monsoon Asia is associated with the Pacific Decadal Oscillation (PDO).
| 2019, Vol.11 | No.5 | No.4 | No.3 | No.2 | No.1 | |
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| 2018, Vol.10 | No.6 | No.5 | No.4 | No.3 | No.2 | No.1 |
| 2017, Vol.9 | No.6 | No.5 | No.4 | No.3 | No.2 | No.1 |
| 2016, Vol.8 | No.6 | No.5 | No.4 | No.3 | No.2 | No.1 |
| 2015, Vol.7 | No.6 | No.5 | No.4 | No.3 | No.2 |
The extensive debris that covers glaciers in the ablation zone of the Himalayan region plays an important part in regulating ablation rates and water availability for the downstream region. The melt rate of ice is determined by the amount of heat conducted through debris material lying over the ice. This study presents the vertical temperature gradients, thermal properties in terms of thermal diffusivity and thermal conductivity, and positive degree-day factors for the debris-covered portion of Lirung Glacier in Langtang Valley, Nepal Himalaya using field-based measurements from three different seasons. Field measurements include debris temperatures at different debris thicknesses, air temperature, and ice melt during the monsoon (2013), winter (2013), and pre-monsoon (2014) seasons. We used a thermal equation to estimate thermal diffusivity and thermal conductivity, and degree-day factors (DDF) were calculated from cumulative positive temperature and ice melt of the measurement period. Our analysis of debris temperature profiles at different depths of debris show the daily linear gradients of ?20.81 °C/m, 4.05 °C/m, and ?7.79 °C/m in the monsoon, winter, and pre-monsoon seasons, respectively. The values of thermal diffusivity and thermal conductivity in the monsoon season were 10 times greater than in the winter season. The large difference in these values is attributed to surface temperature and moisture content within the debris. Similarly, we found higher values of DDFs at thinner debris for the pre-monsoon season than in the monsoon season although we observed less melting during the pre-monsoon season. This is attributed to higher cumulative temperature during the monsoon season than in the pre-monsoon season. Our study advances our understanding of heat conductivity through debris material in different seasons, which supports estimating ice melt and discharge from glacierized river basins with debris-covered glaciers in the Himalayan region.
In this study, in-situ soil moisture measurements are used to evaluate the accuracy of three AMSR-E soil moisture products from NASA (National Aeronautics and Space Administration), JAXA (Japanese Aerospace Exploration Agency) and VUA (Vrije University Amsterdam and NASA) over Maqu County, Source Area of the Yellow River (SAYR), China. Results show that the VUA soil moisture product performs the best among the three AMSR-E soil moisture products in the study area, with a minimum RMSE (root mean square error) of 0.08 (0.10) m3/m3 and smallest absolute error of 0.07 (0.08) m3/m3 at the grassland area with ascending (descending) data. Therefore, the VUA soil moisture product is used to describe the spatial variation of soil moisture during the 2010 growing season over SAYR. The VUA soil moisture product shows that soil moisture presents a declining trend from east south (0.42 m3/m3) to west north (0.23 m3/m3), with good agreement with a general precipitation distribution. The center of SAYR presents extreme wetness (0.60 m3/m3) during the whole study period, especially in July, while the head of SAYR presents a high level soil moisture (0.23 m3/m3) in July, August and September.
This research was undertaken to clarify the characteristics of vegetation change and its main influencing factors on the Qinghai-Tibet Plateau. Using the greenness rate of change (GRC) and correlation factors, we analyzed the trend of vegetation change and its dominant factors from 2000 to 2015. The results indicate that the vegetation tended to improve from 2000 to 2015 on the Qinghai-Tibet Plateau, with the improved area accounting for 39.93% of the total; and the degraded area accounting for 19.32%. The areas of degraded vegetation are mainly concentrated in the low-relief and intermediate-relief mountains of the high-altitude and extremely high-altitude areas on the Qinghai-Tibet Plateau, as the vegetation characteristics are impacted by the terrain. Temperature and precipitation have obvious response mechanisms to vegetation growth, but the effects of precipitation and temperature on vegetation degradation are not significant over a short time frame. Overgrazing and population growth are the dominant factors of vegetation degradation on the Qinghai-Tibet Plateau.
For estimating the altitude-distribution pattern of carbon stocks in desert grasslands and analyzing the possible mechanism for this distribution, a detailed study was performed through a series of field vegetation surveys and soil samplings from 90 vegetation plots and 45 soil profiles at 9 sites of the Hexi Corridor region, Northwestern China. Aboveground, belowground, and litter-fall biomass-carbon stocks ranged from 43 to 109, 23 to 64, and 5 to 20 g/m2, with mean values of 80.82, 44.91, and 12.15 g/m2, respectively. Soil-carbon stocks varied between 2.88 and 3.98 kg/m2, with a mean value of 3.43 kg/m2 in the 0–100-cm soil layer. Both biomass- and soil-carbon stocks had an increasing tendency corresponding to the altitudinal gradient. A significantly negative correlation was found between soil-carbon stock and mean annual temperature, with further better correlations between soil- and biomass-carbon stocks, and mean annual precipitation. Furthermore, soil carbon was found to be positively correlated with soil-silt and -clay content, and negatively correlated with soil bulk density and the volume percent of gravel. It can be concluded that variations in soil texture and climate condition were the key factors influencing the altitudinal pattern of carbon stocks in this desert-grassland ecosystem. Thus, by using the linear-regression functions between altitude and carbon stocks, approximately 4.18 Tg carbon were predicted from the 1,260 km2 of desert grasslands in the study area.
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.
This study investigated the germination behavior and seedling growth of Pycnanthus angolensis seeds. The germination study was carried out in the laboratory and included pretreatment studies and observation of the seed-germination process. For each treatment, three replications of 20 seeds were sown in a transparent plastic germination box (12cm
The article assesses the influence of permafrost weathering on the rate of destruction of technogenic land forms, as exhibited on as illustrated by the railway embankment of the Amur-Yakut mainline in the Sakha Republic (Yakutia). Studies were carried out on a railway section more than 375 km long. The subsidence rate of the embankment slopes and structural excavations was determined using laboratory methods that simulate various mechanisms of temperature (with a transition through 0 °C) impact on rocks. For the first time, a quantitative assessment of the influence of cryogenic weathering on the stability of the railway in the region belonging to the northern building-climatic zone is given. For the territory under consideration, embankment rocks were experimentally determined to undergo more than 100 freezing and thawing cycles during a year. Under the existing climatic conditions, cryogenic weathering actively affects the embankment of the railway to a depth of 30 cm. Most of the embankment deformations detected during field observations are due to defects in the integrity of this particular layer. The size of the disintegrating layer of particular types of rock comprising the railway embankment has been established as reaching 10 cm per year. In 5 years following the formation of embankments comprising the upper structure of the railroad tracks, the physical and mechanical properties of rocks, which initially had a tensile strength for uniaxial compression in the range of 40-70 MPa, were reduced by more than 50%. According to the authors, the establishment of regional cryohypergenesis features is universal in nature and can be applied to solving a wide range of tasks related to the assessment and prediction of the degree of cryogenic transformation of rocks having different structural properties.
This study was conducted to investigate the qualitative and quantitative phytochemical content of the crude extracts of Archidium ohioense, Pelekium gratum, and Hyophila involuta with different alcoholic solvents (ethanol, methanol, Seaman's Schnapps, fresh oil-palm wine, and fresh Raffia-palm wine). The mosses were collected from their natural populations on the central campus of the Obafemi Awolowo University, Ile-Ife, Nigeria. The yield of the extracts was weighed for all the solvents, and the qualitative and quantitative evaluations of the extracts were carried out using standard methods. The results of phytochemical analysis of the crude extracts from the mosses showed the presence of saponins, cardiac glycosides, triterpenes, alkaloids, flavonoids, and steroids. The quantitative phytochemical analysis of the crude extracts showed that ethanolic extracts of Hyophila involuta had the highest flavonoid content (288.37±0.10 mg RE/g), and Raffia-palm-wine extracts of Hyophila involuta had the highest saponin content (224.70±0.02 mg/g), while the methanolic extract of Archidium ohioense had the highest cardiac glycosides content (63.71±0.14 mg/g), and the Raffia-palm wine extract of Hyophila involuta had the highest alkaloids content (102.50±0.12 mg/g). Raffia- and oil-palm wines were observed to be the most effective solvents for all the mosses studied, followed by Seaman's Schnapp, while methanol and ethanol were less effective. The study concluded that the extracts of the mosses studied contain pharmacologically active constituents that can be used for therapeutic purposes.
now cover on the Tibetan Plateau (TP) is closely related to regional and continental biological and hydrological processes. The vast snow cover, special climatic conditions, and sparse vegetative cover over the TP facilitate the occurrence of blowing snow, leading to substantial heterogeneities in the snow cover and great promotion in the moisture supply from the land surface to the overlying atmospheric boundary layer. However, blowing-snow processes are significantly misrepresented or even neglected in current models, which causes considerable uncertainties of numerical model simulations and leads to erroneous estimates of snow-related processes in mountainous terrain. We present in this paper a brief review of our work in the past 5 years to serve as a basis for further development and improvement of the land-surface model. These studies can be divided into three parts: detection of the problems, development of the land-surface model, and application of the coupled model over the TP (the logical framework is presented in Figure 1). The origin and advances in the development of a land-surface model with consideration of blowing-snow effects are described herein; and the importance of blowing-snow processes in the land-surface model, especially over the TP, is highlighted. We expect that the blowing-snow studies over the TP will play a key role in documenting and understanding the land-surface processes (LSPs) and the cryospheric changes over the TP.
Understanding the variation in a plant's water sources is critical to understanding hydrological processes in water-limited environments. Here, we measured the stable-isotope ratios (δ18O) of xylem water of Caragana microphylla, precipitation, soil water from different depths, and groundwater to quantitatively analyze the proportion of water sources for the shrub. We found that the water sources of C. microphylla differed with the plant's ages and the seasons. The main water source for young shrubs was upper-soil water, and it showed significant changes with seasonal precipitation inputs. In summer, the proportion contributed by shallow water was significantly increased with increased precipitation inputs. Then, the contribution from shallow-soil water decreased with the decline in precipitation input in spring and autumn. However, the adult shrubs resorted to deep-soil layers and groundwater as the main water sources during the whole growing season and showed much less seasonal variation. We conclude that the main water source of the young shrubs was upper-soil water and was controlled by precipitation inputs. However, once the shrub gradually grew up and the roots reached sufficient depth, the main water sources change from the upper-soil layer recharged by precipitation to deep-soil water and groundwater, which were relatively stable and abundant in the desert ecosystem. These results also suggest that desert shrubs may be able to switch their main water sources to deep and reliable water sources as their age increases, and this adjustment to water availability carries significant importance for their acclimation to the desert habitat.
Winter maintenance operations are crucial for pedestrian and motorist safety and public mobility on urban streets and highways in cold regions, especially during winter storms. This study provides a comprehensive literature review of existing deicing technologies, with emphasis on electrical resistance-heating deicing technologies for possible applications in areas with concentrated traffic, such as street intersections and crosswalks. A thorough review of existing and emerging deicing technology for snow/ice melting was conducted. The performance of various deicing methods was evaluated and the installation and operation cost of the electrical resistance-heating methods compared. Finally, current state of the practice of intersection/crosswalk winter maintenance was surveyed among state departments of transportation in North America. The intersection/crosswalk winter maintenance procedure adopted by the State of Alaska Department of Transportation and Public Facilities was described, and the annual winter maintenance and operation cost per intersection was estimated. It was found that the annual energy cost of an electrical resistance-heating method such as the carbon-fiber-tape deicing technology is about the same as the average annual maintenance and operation cost of current practice. In addition, an automatic electrical resistance-heating deicing system will bring benefits such as minimized delay time and improved safety for pedestrian and vehicular traffic in an urban application.
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.
Soil calcium carbonate (CaCO3) has a strong solid phosphorus effect, and high content of CaCO3 can significantly reduce the effectiveness of soil phosphorus. To reveal the limiting effect of soil CaCO3 on the growth of plants on sand land and its mechanism of plant physiology, we performed pot experiments with a two-factor randomized block design and a three-factor orthogonal design for different soil CaCO3 content treatments using Artemisia ordosica seedlings. In the experiments, we surveyed plant height, aboveground biomass, root length and root weight and analyzed N, P concentrations and RNA content of the seedlings, and discussed the relationships between relative growth rate (RGR) of the seedlings and N:P ratio as well as RNA. Results show that, the RGRs of plant height and above-ground biomass of the seedlings decreased significantly with the increase of soil CaCO3 content, and those for root length and root weight decreased. The RGRs of plant height and above-ground biomass of the seedlings were significantly negatively correlated with leaf N:P ratios, but significantly positively correlated with leaf RNA content and leaf P concentrations. It can be seen that soil CaCO3 is a stress factor for the growth of A. ordosica seedlings, and the growth response of the seedlings under the influence of soil CaCO3 is in line with the Growth Rate Hypothesis.
aturated hydraulic conductivity and unsaturated hydraulic conductivity which are influenced by soil are two important factors that affect soil water transport. In this paper, data supplied by the Chinese Academy of Sciences are used to determine true unsaturated hydrology values. Furthermore, in combination with observed, model simulation and experimental data, an improved saturated hydraulic conductivity parameterization scheme is carried out in CLM4.5 at a single point in the summer. The main results show that: (1) After improving saturated hydraulic conductivity in CLM4.5 through a parameterization modification, it is found that shallow layer soil moisture increases compared to the initial value; and (2) The numerical values of unsaturated hydraulic conductivities in the model are obviously larger than experimental values. By substituting the Brooks-Corey soil water characteristic curve into the Mualem model, the value of unsaturated hydraulic conductivity is modified; (3) By using the modified value, it is found that the attenuating magnitude of simulated soil moisture caused by each rainfall event is reduced. The soil moisture variation in shallow layers (5, 10 and 20 cm) could be better displayed.
An understanding of soil microbial communities is crucial in roadside soil environmental assessments. The 16S rRNA sequencing of a stressed microbial community in soil adjacent to the Qinghai-Tibet Highway (QTH) revealed that the accumulation of heavy metals (over about 10 years) has affected the diversity of bacterial abundance and microbial community structure. The proximity of a sampling site to the QTH/Qinghai-Tibet Railway (QTR), which is effectively a measure of the density of human engineering, was the dominant factor influencing bacterial community diversity. The diversity of bacterial communities shows that 16S rRNA gene abundance decreased in relation to proximity to the QTH and QTR in both alpine wetland and meadow areas. The dominant phyla across all samples were Actinobacteria and Proteobacteria. The concentration of Cr and Cd in the soil were positively correlated with proximity to the QTH and QTR (MC/WC sampling sites), and Ni, Co, and V were positively correlated with proximity to the QTH and QTR (MA/WA sampling sites). The results presented in this study provide an insight into the relationships among heavy metals and soil microbial communities, and have important implications for assessing and predicting the impacts of human-induced activities from the QTH and QTR in such an extreme and fragile environment.
The source regions of the Yangtze and Yellow Rivers are important in the field of eco-environmental change research in China because of its distinct alpine ecosystem and cryosphere environment. At present, there are three different concepts on the extent of source areas of the Yangtze and Yellow Rivers: hydrological, geographical, and eco-environmental. Over the past decades, annual average air temperature has warmed significantly; moreover, the temperature rise rate increases notably with increase of time of the data series. Annual precipitation has no obvious increase or decrease trend, and the climate has become warm and dry in the source regions. As a result, the cryosphere in the regions has shrunk significantly since 1960s. A warm and dry climate and changing cryosphere together induced a substantial declination of alpine wetlands, marked decrease in river runoff, significant degradation of alpine grassland, and a reduction of engineering stability. The ecological environment, however, has a tendency for restoration in the regions because the climate has become gradually warm and wet since 2000. Thus, studies on eco-environmental change is transforming from a single element to multidisciplinary integration. Climate change-cryopshere change-physical and socioeconomic impacts/risk-adaptation constitute a chain of multidisciplinary integration research.
Lakes regulate the water and heat exchange between the ground and the atmosphere on different temporal and spatial scales. However, studies of the lake effect in the high-altitude Tibetan Plateau (TP) rarely have been performed until recently, and little attention has been paid to modelling of frozen lakes. In this study, the Weather Research and Forecasting Model (WRF v. 3.6.1) is employed to conduct three numerical experiments in the Ngoring Lake Basin (the original experiment, an experiment with a tuned model, and a no-lake experiment) to investigate the influences of parameter optimization on the lake simulation and of the high-altitude lake on the regional climate. After the lake depth, the roughness lengths, and initial surface temperature are corrected in the model, the simulation of the air temperature is distinctly improved. In the experiment using a tuned model, the simulated sensible-heat flux (H) is clearly improved, especially during periods of ice melting (from late spring to early summer) and freezing (late fall). The improvement of latent-heat flux (LE) is mainly manifested by the sharp increase in the correlation coefficient between simulation and observation, whereas the improvement in the average value is small. The optimization of initial surface temperature shows the most prominent effect in the first year and distinctly weakens after a freezing period. After the lakes become grassland in the model, the daytime temperature clearly increases during the freezing and melting periods; but the nocturnal cooling appears in other stages, especially from September to October. The annual mean H increases by 6.4 times in the regions of the Ngoring Lake and the Gyaring Lake, and the LE declines by 56.2%. The sum of H and LE increases from 71.2 W/m2 (with lake) to 84.6 W/m2 (no lake). For the entire simulation region, the sum of H and LE also increases slightly. After the lakes are removed, the air temperature increases significantly from June to September over the area corresponding to the two lakes, and an abnormal convergence field appears; at the same time, the precipitation clearly increases over the two lakes and surrounding areas.
Khaya belongs to the family Meliaceae. In Nigeria the genus is represented by three species viz; K. senegalensis A. Juss., K. grandifoliola C. DC. and K. ivorensis A. Chev. Comparative foliar anatomy of the three Khaya species was carried out to identify and describe distinctive anatomical characters that could possibly be used to delimit the three taxa. Transverse section, epidermal peels and cleared leaves of these three species were made. Characteristic similarity and disparity in the tissues arrangement as well as cell inclusions were noted for description and delimitation. The three Khaya species studied had essentially the same anatomical features, e.g., venation pattern having open polygonal areoles and the veins terminals biforkated. However, there were characters that seem to be species specific, e.g., vien termination number and areole width. The leaf epidermal studies of the three species revealed similarities in stomatal type which are generally staurocytic, epidermal cells and undulating anticlinal cell walls but stomata density varied. Hexacytic stomata is only observed in the abaxial surface of K. grandifoliola which distinguished this species from the others. The leaf petiole shape of the three species are round and difficult to distinguish into adaxial and abaxial surfaces. The cuticle is striated, vascular bundles are heart shape, conjoint, concentric and amphivasal, but are different in epidermal and collenchyma cell layer numbers. The leaf transverse sections of the three Khaya species studied have conjoint, concentric and amphicribral bundles while the leaf cuticle of K. senegalensis and K. grandifoliola are striated but that of Khaya ivorensis is non-striated.
Based on observational data obtained from 1961 to 2011 in the Tarim River Basin, China, we investigated the chaotic dynamics of temperature, precipitation, relative humidity, and evaporation. The main findings are as follow: (1) The four data series have significant chaotic and fractal behaviors, which are the result of the evolution of a nonlinear chaotic dynamic system. The climatic process in the Tarim River Basin also has deterministic and stochastic characteristics. (2) To describe the temperature, precipitation, relative humidity, and evaporation dynamics, at least three independent variables at daily scale are required; in terms of complexity, their order is evaporation > temperature > precipitation > relative humidity. (3) Their respective largest Lyapunov exponent λ 1 shows the order of their degree of complexity is relative humidity > temperature > precipitation ≈ evaporation; the maximum time scales for which the four systems can be predicted are 17 days, 17 days, 16 days, and 16 days, if calculated separately. (4) The Kolmogorov entropy K illustrates that the complexity of the nonlinear precipitation system is much greater than that of the other three systems. Both temperature and evaporation systems exhibit weaker chaotic behavior, their predictability is better, and the degree of complexity is less than that of the other two factors.
Hydrology of the high glacierized region in the Tianshan Mountains is an important water resource for arid and semiarid areas of China, even Central Asia. The hydrological process is complex to understand, due to the high variability in climate and the lack of hydrometeorological data. Based on field observations, the present study analyzes the meteorological and hydrological characteristics of the Koxkar Glacier River Basin during 2008-2011; and the factors influencing climate impact on glacier hydrology are discussed. The results show that precipitation at the terminus of the glacier was 426.2 mm, 471.8 mm, 624.9 mm, and 532 mm in 2008, 2009, 2010, and 2011, respectively. Discharge increases starting in May, reaches its highest value in July and August, and then starts to decrease. The mean annual discharge was 118.23×106 m3 during the four years observed, with 87.0% occurring in the ablation season (May-September). During the study period, the runoff in August accounted for 29% of total streamflow, followed by July (22%) and June (14%). The runoff exhibited obviously high interannual variability from April to September, induced by drastic changes in climate factors. Discharge autocorrelations are very high for all the years. The climate factors show different influences on discharge. The highest correlation R between daily temperature and discharge was for a time lag of 2-3 days on the Koxkar Glacier (0.66-0.76). The daily depth of runoff to daily temperature and daily water vapor pressure had an R 2 value of 0.56 and 0.69, respectively, which could be described by an exponential function. A closer relationship is found between runoff and either temperature or water vapor pressure on a monthly scale; the R 2 values are 0.65 and 0.78, respectively. The study helps us to understand the mechanisms of the hydrological-meteorological system of typical regional glaciers and to provide a reference for glacier-runoff simulations and water-resource management.
The extensive debris that covers glaciers in the ablation zone of the Himalayan region plays an important part in regulating ablation rates and water availability for the downstream region. The melt rate of ice is determined by the amount of heat conducted through debris material lying over the ice. This study presents the vertical temperature gradients, thermal properties in terms of thermal diffusivity and thermal conductivity, and positive degree-day factors for the debris-covered portion of Lirung Glacier in Langtang Valley, Nepal Himalaya using field-based measurements from three different seasons. Field measurements include debris temperatures at different debris thicknesses, air temperature, and ice melt during the monsoon (2013), winter (2013), and pre-monsoon (2014) seasons. We used a thermal equation to estimate thermal diffusivity and thermal conductivity, and degree-day factors (DDF) were calculated from cumulative positive temperature and ice melt of the measurement period. Our analysis of debris temperature profiles at different depths of debris show the daily linear gradients of ?20.81 °C/m, 4.05 °C/m, and ?7.79 °C/m in the monsoon, winter, and pre-monsoon seasons, respectively. The values of thermal diffusivity and thermal conductivity in the monsoon season were 10 times greater than in the winter season. The large difference in these values is attributed to surface temperature and moisture content within the debris. Similarly, we found higher values of DDFs at thinner debris for the pre-monsoon season than in the monsoon season although we observed less melting during the pre-monsoon season. This is attributed to higher cumulative temperature during the monsoon season than in the pre-monsoon season. Our study advances our understanding of heat conductivity through debris material in different seasons, which supports estimating ice melt and discharge from glacierized river basins with debris-covered glaciers in the Himalayan region.
In this study, in-situ soil moisture measurements are used to evaluate the accuracy of three AMSR-E soil moisture products from NASA (National Aeronautics and Space Administration), JAXA (Japanese Aerospace Exploration Agency) and VUA (Vrije University Amsterdam and NASA) over Maqu County, Source Area of the Yellow River (SAYR), China. Results show that the VUA soil moisture product performs the best among the three AMSR-E soil moisture products in the study area, with a minimum RMSE (root mean square error) of 0.08 (0.10) m3/m3 and smallest absolute error of 0.07 (0.08) m3/m3 at the grassland area with ascending (descending) data. Therefore, the VUA soil moisture product is used to describe the spatial variation of soil moisture during the 2010 growing season over SAYR. The VUA soil moisture product shows that soil moisture presents a declining trend from east south (0.42 m3/m3) to west north (0.23 m3/m3), with good agreement with a general precipitation distribution. The center of SAYR presents extreme wetness (0.60 m3/m3) during the whole study period, especially in July, while the head of SAYR presents a high level soil moisture (0.23 m3/m3) in July, August and September.
This research was undertaken to clarify the characteristics of vegetation change and its main influencing factors on the Qinghai-Tibet Plateau. Using the greenness rate of change (GRC) and correlation factors, we analyzed the trend of vegetation change and its dominant factors from 2000 to 2015. The results indicate that the vegetation tended to improve from 2000 to 2015 on the Qinghai-Tibet Plateau, with the improved area accounting for 39.93% of the total; and the degraded area accounting for 19.32%. The areas of degraded vegetation are mainly concentrated in the low-relief and intermediate-relief mountains of the high-altitude and extremely high-altitude areas on the Qinghai-Tibet Plateau, as the vegetation characteristics are impacted by the terrain. Temperature and precipitation have obvious response mechanisms to vegetation growth, but the effects of precipitation and temperature on vegetation degradation are not significant over a short time frame. Overgrazing and population growth are the dominant factors of vegetation degradation on the Qinghai-Tibet Plateau.
For estimating the altitude-distribution pattern of carbon stocks in desert grasslands and analyzing the possible mechanism for this distribution, a detailed study was performed through a series of field vegetation surveys and soil samplings from 90 vegetation plots and 45 soil profiles at 9 sites of the Hexi Corridor region, Northwestern China. Aboveground, belowground, and litter-fall biomass-carbon stocks ranged from 43 to 109, 23 to 64, and 5 to 20 g/m2, with mean values of 80.82, 44.91, and 12.15 g/m2, respectively. Soil-carbon stocks varied between 2.88 and 3.98 kg/m2, with a mean value of 3.43 kg/m2 in the 0–100-cm soil layer. Both biomass- and soil-carbon stocks had an increasing tendency corresponding to the altitudinal gradient. A significantly negative correlation was found between soil-carbon stock and mean annual temperature, with further better correlations between soil- and biomass-carbon stocks, and mean annual precipitation. Furthermore, soil carbon was found to be positively correlated with soil-silt and -clay content, and negatively correlated with soil bulk density and the volume percent of gravel. It can be concluded that variations in soil texture and climate condition were the key factors influencing the altitudinal pattern of carbon stocks in this desert-grassland ecosystem. Thus, by using the linear-regression functions between altitude and carbon stocks, approximately 4.18 Tg carbon were predicted from the 1,260 km2 of desert grasslands in the study area.
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.
This study investigated the germination behavior and seedling growth of Pycnanthus angolensis seeds. The germination study was carried out in the laboratory and included pretreatment studies and observation of the seed-germination process. For each treatment, three replications of 20 seeds were sown in a transparent plastic germination box (12cm
The article assesses the influence of permafrost weathering on the rate of destruction of technogenic land forms, as exhibited on as illustrated by the railway embankment of the Amur-Yakut mainline in the Sakha Republic (Yakutia). Studies were carried out on a railway section more than 375 km long. The subsidence rate of the embankment slopes and structural excavations was determined using laboratory methods that simulate various mechanisms of temperature (with a transition through 0 °C) impact on rocks. For the first time, a quantitative assessment of the influence of cryogenic weathering on the stability of the railway in the region belonging to the northern building-climatic zone is given. For the territory under consideration, embankment rocks were experimentally determined to undergo more than 100 freezing and thawing cycles during a year. Under the existing climatic conditions, cryogenic weathering actively affects the embankment of the railway to a depth of 30 cm. Most of the embankment deformations detected during field observations are due to defects in the integrity of this particular layer. The size of the disintegrating layer of particular types of rock comprising the railway embankment has been established as reaching 10 cm per year. In 5 years following the formation of embankments comprising the upper structure of the railroad tracks, the physical and mechanical properties of rocks, which initially had a tensile strength for uniaxial compression in the range of 40-70 MPa, were reduced by more than 50%. According to the authors, the establishment of regional cryohypergenesis features is universal in nature and can be applied to solving a wide range of tasks related to the assessment and prediction of the degree of cryogenic transformation of rocks having different structural properties.
This study was conducted to investigate the qualitative and quantitative phytochemical content of the crude extracts of Archidium ohioense, Pelekium gratum, and Hyophila involuta with different alcoholic solvents (ethanol, methanol, Seaman's Schnapps, fresh oil-palm wine, and fresh Raffia-palm wine). The mosses were collected from their natural populations on the central campus of the Obafemi Awolowo University, Ile-Ife, Nigeria. The yield of the extracts was weighed for all the solvents, and the qualitative and quantitative evaluations of the extracts were carried out using standard methods. The results of phytochemical analysis of the crude extracts from the mosses showed the presence of saponins, cardiac glycosides, triterpenes, alkaloids, flavonoids, and steroids. The quantitative phytochemical analysis of the crude extracts showed that ethanolic extracts of Hyophila involuta had the highest flavonoid content (288.37±0.10 mg RE/g), and Raffia-palm-wine extracts of Hyophila involuta had the highest saponin content (224.70±0.02 mg/g), while the methanolic extract of Archidium ohioense had the highest cardiac glycosides content (63.71±0.14 mg/g), and the Raffia-palm wine extract of Hyophila involuta had the highest alkaloids content (102.50±0.12 mg/g). Raffia- and oil-palm wines were observed to be the most effective solvents for all the mosses studied, followed by Seaman's Schnapp, while methanol and ethanol were less effective. The study concluded that the extracts of the mosses studied contain pharmacologically active constituents that can be used for therapeutic purposes.
now cover on the Tibetan Plateau (TP) is closely related to regional and continental biological and hydrological processes. The vast snow cover, special climatic conditions, and sparse vegetative cover over the TP facilitate the occurrence of blowing snow, leading to substantial heterogeneities in the snow cover and great promotion in the moisture supply from the land surface to the overlying atmospheric boundary layer. However, blowing-snow processes are significantly misrepresented or even neglected in current models, which causes considerable uncertainties of numerical model simulations and leads to erroneous estimates of snow-related processes in mountainous terrain. We present in this paper a brief review of our work in the past 5 years to serve as a basis for further development and improvement of the land-surface model. These studies can be divided into three parts: detection of the problems, development of the land-surface model, and application of the coupled model over the TP (the logical framework is presented in Figure 1). The origin and advances in the development of a land-surface model with consideration of blowing-snow effects are described herein; and the importance of blowing-snow processes in the land-surface model, especially over the TP, is highlighted. We expect that the blowing-snow studies over the TP will play a key role in documenting and understanding the land-surface processes (LSPs) and the cryospheric changes over the TP.
Understanding the variation in a plant's water sources is critical to understanding hydrological processes in water-limited environments. Here, we measured the stable-isotope ratios (δ18O) of xylem water of Caragana microphylla, precipitation, soil water from different depths, and groundwater to quantitatively analyze the proportion of water sources for the shrub. We found that the water sources of C. microphylla differed with the plant's ages and the seasons. The main water source for young shrubs was upper-soil water, and it showed significant changes with seasonal precipitation inputs. In summer, the proportion contributed by shallow water was significantly increased with increased precipitation inputs. Then, the contribution from shallow-soil water decreased with the decline in precipitation input in spring and autumn. However, the adult shrubs resorted to deep-soil layers and groundwater as the main water sources during the whole growing season and showed much less seasonal variation. We conclude that the main water source of the young shrubs was upper-soil water and was controlled by precipitation inputs. However, once the shrub gradually grew up and the roots reached sufficient depth, the main water sources change from the upper-soil layer recharged by precipitation to deep-soil water and groundwater, which were relatively stable and abundant in the desert ecosystem. These results also suggest that desert shrubs may be able to switch their main water sources to deep and reliable water sources as their age increases, and this adjustment to water availability carries significant importance for their acclimation to the desert habitat.
Winter maintenance operations are crucial for pedestrian and motorist safety and public mobility on urban streets and highways in cold regions, especially during winter storms. This study provides a comprehensive literature review of existing deicing technologies, with emphasis on electrical resistance-heating deicing technologies for possible applications in areas with concentrated traffic, such as street intersections and crosswalks. A thorough review of existing and emerging deicing technology for snow/ice melting was conducted. The performance of various deicing methods was evaluated and the installation and operation cost of the electrical resistance-heating methods compared. Finally, current state of the practice of intersection/crosswalk winter maintenance was surveyed among state departments of transportation in North America. The intersection/crosswalk winter maintenance procedure adopted by the State of Alaska Department of Transportation and Public Facilities was described, and the annual winter maintenance and operation cost per intersection was estimated. It was found that the annual energy cost of an electrical resistance-heating method such as the carbon-fiber-tape deicing technology is about the same as the average annual maintenance and operation cost of current practice. In addition, an automatic electrical resistance-heating deicing system will bring benefits such as minimized delay time and improved safety for pedestrian and vehicular traffic in an urban application.
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.
Soil calcium carbonate (CaCO3) has a strong solid phosphorus effect, and high content of CaCO3 can significantly reduce the effectiveness of soil phosphorus. To reveal the limiting effect of soil CaCO3 on the growth of plants on sand land and its mechanism of plant physiology, we performed pot experiments with a two-factor randomized block design and a three-factor orthogonal design for different soil CaCO3 content treatments using Artemisia ordosica seedlings. In the experiments, we surveyed plant height, aboveground biomass, root length and root weight and analyzed N, P concentrations and RNA content of the seedlings, and discussed the relationships between relative growth rate (RGR) of the seedlings and N:P ratio as well as RNA. Results show that, the RGRs of plant height and above-ground biomass of the seedlings decreased significantly with the increase of soil CaCO3 content, and those for root length and root weight decreased. The RGRs of plant height and above-ground biomass of the seedlings were significantly negatively correlated with leaf N:P ratios, but significantly positively correlated with leaf RNA content and leaf P concentrations. It can be seen that soil CaCO3 is a stress factor for the growth of A. ordosica seedlings, and the growth response of the seedlings under the influence of soil CaCO3 is in line with the Growth Rate Hypothesis.
aturated hydraulic conductivity and unsaturated hydraulic conductivity which are influenced by soil are two important factors that affect soil water transport. In this paper, data supplied by the Chinese Academy of Sciences are used to determine true unsaturated hydrology values. Furthermore, in combination with observed, model simulation and experimental data, an improved saturated hydraulic conductivity parameterization scheme is carried out in CLM4.5 at a single point in the summer. The main results show that: (1) After improving saturated hydraulic conductivity in CLM4.5 through a parameterization modification, it is found that shallow layer soil moisture increases compared to the initial value; and (2) The numerical values of unsaturated hydraulic conductivities in the model are obviously larger than experimental values. By substituting the Brooks-Corey soil water characteristic curve into the Mualem model, the value of unsaturated hydraulic conductivity is modified; (3) By using the modified value, it is found that the attenuating magnitude of simulated soil moisture caused by each rainfall event is reduced. The soil moisture variation in shallow layers (5, 10 and 20 cm) could be better displayed.
An understanding of soil microbial communities is crucial in roadside soil environmental assessments. The 16S rRNA sequencing of a stressed microbial community in soil adjacent to the Qinghai-Tibet Highway (QTH) revealed that the accumulation of heavy metals (over about 10 years) has affected the diversity of bacterial abundance and microbial community structure. The proximity of a sampling site to the QTH/Qinghai-Tibet Railway (QTR), which is effectively a measure of the density of human engineering, was the dominant factor influencing bacterial community diversity. The diversity of bacterial communities shows that 16S rRNA gene abundance decreased in relation to proximity to the QTH and QTR in both alpine wetland and meadow areas. The dominant phyla across all samples were Actinobacteria and Proteobacteria. The concentration of Cr and Cd in the soil were positively correlated with proximity to the QTH and QTR (MC/WC sampling sites), and Ni, Co, and V were positively correlated with proximity to the QTH and QTR (MA/WA sampling sites). The results presented in this study provide an insight into the relationships among heavy metals and soil microbial communities, and have important implications for assessing and predicting the impacts of human-induced activities from the QTH and QTR in such an extreme and fragile environment.
The source regions of the Yangtze and Yellow Rivers are important in the field of eco-environmental change research in China because of its distinct alpine ecosystem and cryosphere environment. At present, there are three different concepts on the extent of source areas of the Yangtze and Yellow Rivers: hydrological, geographical, and eco-environmental. Over the past decades, annual average air temperature has warmed significantly; moreover, the temperature rise rate increases notably with increase of time of the data series. Annual precipitation has no obvious increase or decrease trend, and the climate has become warm and dry in the source regions. As a result, the cryosphere in the regions has shrunk significantly since 1960s. A warm and dry climate and changing cryosphere together induced a substantial declination of alpine wetlands, marked decrease in river runoff, significant degradation of alpine grassland, and a reduction of engineering stability. The ecological environment, however, has a tendency for restoration in the regions because the climate has become gradually warm and wet since 2000. Thus, studies on eco-environmental change is transforming from a single element to multidisciplinary integration. Climate change-cryopshere change-physical and socioeconomic impacts/risk-adaptation constitute a chain of multidisciplinary integration research.
Lakes regulate the water and heat exchange between the ground and the atmosphere on different temporal and spatial scales. However, studies of the lake effect in the high-altitude Tibetan Plateau (TP) rarely have been performed until recently, and little attention has been paid to modelling of frozen lakes. In this study, the Weather Research and Forecasting Model (WRF v. 3.6.1) is employed to conduct three numerical experiments in the Ngoring Lake Basin (the original experiment, an experiment with a tuned model, and a no-lake experiment) to investigate the influences of parameter optimization on the lake simulation and of the high-altitude lake on the regional climate. After the lake depth, the roughness lengths, and initial surface temperature are corrected in the model, the simulation of the air temperature is distinctly improved. In the experiment using a tuned model, the simulated sensible-heat flux (H) is clearly improved, especially during periods of ice melting (from late spring to early summer) and freezing (late fall). The improvement of latent-heat flux (LE) is mainly manifested by the sharp increase in the correlation coefficient between simulation and observation, whereas the improvement in the average value is small. The optimization of initial surface temperature shows the most prominent effect in the first year and distinctly weakens after a freezing period. After the lakes become grassland in the model, the daytime temperature clearly increases during the freezing and melting periods; but the nocturnal cooling appears in other stages, especially from September to October. The annual mean H increases by 6.4 times in the regions of the Ngoring Lake and the Gyaring Lake, and the LE declines by 56.2%. The sum of H and LE increases from 71.2 W/m2 (with lake) to 84.6 W/m2 (no lake). For the entire simulation region, the sum of H and LE also increases slightly. After the lakes are removed, the air temperature increases significantly from June to September over the area corresponding to the two lakes, and an abnormal convergence field appears; at the same time, the precipitation clearly increases over the two lakes and surrounding areas.
Khaya belongs to the family Meliaceae. In Nigeria the genus is represented by three species viz; K. senegalensis A. Juss., K. grandifoliola C. DC. and K. ivorensis A. Chev. Comparative foliar anatomy of the three Khaya species was carried out to identify and describe distinctive anatomical characters that could possibly be used to delimit the three taxa. Transverse section, epidermal peels and cleared leaves of these three species were made. Characteristic similarity and disparity in the tissues arrangement as well as cell inclusions were noted for description and delimitation. The three Khaya species studied had essentially the same anatomical features, e.g., venation pattern having open polygonal areoles and the veins terminals biforkated. However, there were characters that seem to be species specific, e.g., vien termination number and areole width. The leaf epidermal studies of the three species revealed similarities in stomatal type which are generally staurocytic, epidermal cells and undulating anticlinal cell walls but stomata density varied. Hexacytic stomata is only observed in the abaxial surface of K. grandifoliola which distinguished this species from the others. The leaf petiole shape of the three species are round and difficult to distinguish into adaxial and abaxial surfaces. The cuticle is striated, vascular bundles are heart shape, conjoint, concentric and amphivasal, but are different in epidermal and collenchyma cell layer numbers. The leaf transverse sections of the three Khaya species studied have conjoint, concentric and amphicribral bundles while the leaf cuticle of K. senegalensis and K. grandifoliola are striated but that of Khaya ivorensis is non-striated.
Based on observational data obtained from 1961 to 2011 in the Tarim River Basin, China, we investigated the chaotic dynamics of temperature, precipitation, relative humidity, and evaporation. The main findings are as follow: (1) The four data series have significant chaotic and fractal behaviors, which are the result of the evolution of a nonlinear chaotic dynamic system. The climatic process in the Tarim River Basin also has deterministic and stochastic characteristics. (2) To describe the temperature, precipitation, relative humidity, and evaporation dynamics, at least three independent variables at daily scale are required; in terms of complexity, their order is evaporation > temperature > precipitation > relative humidity. (3) Their respective largest Lyapunov exponent λ 1 shows the order of their degree of complexity is relative humidity > temperature > precipitation ≈ evaporation; the maximum time scales for which the four systems can be predicted are 17 days, 17 days, 16 days, and 16 days, if calculated separately. (4) The Kolmogorov entropy K illustrates that the complexity of the nonlinear precipitation system is much greater than that of the other three systems. Both temperature and evaporation systems exhibit weaker chaotic behavior, their predictability is better, and the degree of complexity is less than that of the other two factors.
Hydrology of the high glacierized region in the Tianshan Mountains is an important water resource for arid and semiarid areas of China, even Central Asia. The hydrological process is complex to understand, due to the high variability in climate and the lack of hydrometeorological data. Based on field observations, the present study analyzes the meteorological and hydrological characteristics of the Koxkar Glacier River Basin during 2008-2011; and the factors influencing climate impact on glacier hydrology are discussed. The results show that precipitation at the terminus of the glacier was 426.2 mm, 471.8 mm, 624.9 mm, and 532 mm in 2008, 2009, 2010, and 2011, respectively. Discharge increases starting in May, reaches its highest value in July and August, and then starts to decrease. The mean annual discharge was 118.23×106 m3 during the four years observed, with 87.0% occurring in the ablation season (May-September). During the study period, the runoff in August accounted for 29% of total streamflow, followed by July (22%) and June (14%). The runoff exhibited obviously high interannual variability from April to September, induced by drastic changes in climate factors. Discharge autocorrelations are very high for all the years. The climate factors show different influences on discharge. The highest correlation R between daily temperature and discharge was for a time lag of 2-3 days on the Koxkar Glacier (0.66-0.76). The daily depth of runoff to daily temperature and daily water vapor pressure had an R 2 value of 0.56 and 0.69, respectively, which could be described by an exponential function. A closer relationship is found between runoff and either temperature or water vapor pressure on a monthly scale; the R 2 values are 0.65 and 0.78, respectively. The study helps us to understand the mechanisms of the hydrological-meteorological system of typical regional glaciers and to provide a reference for glacier-runoff simulations and water-resource management.
