Recent climate trends on the northern slopes of the Tianshan Mountains, Xinjiang, China

In arid regions, mountains fulfill important ecological and economic functions for the surrounding lowlands. In the scenario of global warming, mountain ecosystems change rapidly, especially in the arid region of northwestern China. This paper provides an assessment of the changes in temperature and precipitation in the historical records of climate on the northern slopes of the eastern Tianshan Mountains. A Mann-Kendall nonparametric trend and Sen＇s tests are employed to analyze the interannual changes and innerannual variability in temperature and precipitatiofi in the regions of low to high altitude. The present study finds that the largest increases in annual temperature are observed at stations in the low altitude regions. The significant increasing trends in temperature tend to occur mainly in late winter and early spring at stations from middle to high altitude, but in summer and autumn at stations of low altitudes. The increasing trends in annual precipitation are found from the middle to high altitude areas, but decreasing trends are found in the low altitude areas. The significant increasing trends in precipitation occur mostly in winter and earlier spring at stations from the middle to high altitudes, while the increasing and decreasing trend coexists at stations of low altitude with most of the significant trend changes occurring in March, June and August.     

Avalanche activity and characteristics of its triggering factors in the western Tianshan Mountains,China

Snow avalanche is a serious threat to the safety of roads in alpine mountains. In the western Tianshan Mountains, large scale avalanches occur every year and affect road safety. There is an urgent need to identify the characteristics of triggering factors for avalanche activity in this region to improve road safety and the management of natural hazards. Based on the observation of avalanche activity along the national road G218 in the western Tianshan Mountains, avalanche event data in combination with meteorological, snowpack and earthquake data were collected and analyzed. The snow climate of the mountain range was examined using a recently developed snow climate classification scheme, and triggering conditions of snow avalanche in different snow climate regions were compared. The results show that snowfall is the most common triggering factor for a natural avalanche and there is high probability of avalanche release with snowfall exceeding 20.4 mm during a snowfall period. Consecutive rise in temperature within three days and daily mean temperature reaching 0.5°C in the following day imply a high probability of temperaturerise-triggered avalanche release. Earthquakes have a significant impact on the formation of large size avalanches in the area. For the period 2011-2017, five cases were identified as a consequence of earthquake with magnitudes of 3.3≤M_L≤5.1 and source-to-site distances of 19~139 km. The Tianshan Mountains are characterized by a continental snow climate with lower snow density, lower snow shear strength and high proportion depth hoar, which explains that both the snowfall and temperature for triggering avalanche release in the continental snow climate of the Tianshan Mountains are lower than that in maritime snow climate and transitional snow climate regions. The findings help forecast avalanche release for mitigating avalanche disaster and assessing the risk of avalanche disaster.     

Reference evapotranspiration concentration and its relationship with precipitation concentration at southern and northern slopes of Tianshan Mountains,China

The investigation of concentration characteristics of reference evapotranspiration(ETref) is important for water resources management. The concentration index(CI), concentration degree(CD) and concentration period(CP) are used to investigate the concentration characteristics of ETref and the relationship between ETref concentration and precipitation concentration at sub-monthly timescale based on the daily climatic variables from 1966 to 2015 in 27 meteorological stations at the southern and northern slopes of Tianshan Mountains in China. It was found that the CI of ETref is about 0.40 and less concentrated than precipitation in the study area. At the southern slope, the maximum ETref appears in late June and is earlier than the maximum precipitation(early July), ETref distributes more equally than precipitation, and the CI, CD and CP of these two variables do not show significant change based on the Mann–Kendall test. At the northern slope, both the maximum ETref and precipitation appear in early July, and ETref is more dispersed than precipitation. During the study period, the maximum ETref at the northern slope tends to appear earlier due to the impacts of wind speed, relative humidity, sunshine duration, and air temperature. ETref concentration does not match the precipitation concentration in the study area, particularly at the southern slope. The mismatch between ETref and precipitation concentration within a year reveals the water resources pressure on environmental, social and economic sustainability in the study area.     

Impact factors identification of spatial heterogeneity of herbaceous plant diversity on five southern islands of Miaodao Archipelago in North China

Herbaceous plants are widely distributed on islands and where they exhibit spatial heterogeneity. Accurately identifying the impact factors that drive spatial heterogeneity can reveal typical island biodiversity patterns. Five southern islands in the Miaodao Archipelago, North China were studied herein. The spatial distribution of herbaceous plant diversity on these islands was analyzed, and the impact factors and their degree of impact on spatial heterogeneity were identified using CCA ordination and ANOVA. The results reveal 114 herbaceous plant species, belonging to 94 genera from 34 families in the 50 plots sampled. The total species numbers on different islands were significantly positively correlated with island area, and the average α diversity was correlated with human activities, while the β diversity among islands was more affected by island area than mutual distances. Spatial heterogeneity within islands indicated that the diversities were generally high in areas with higher altitude, slope, total nitrogen, total carbon, and canopy density, and lower moisture content, pH, total phosphorus, total potassium, and aspect. Among the environmental factors, pH, canopy density, total K, total P, moisture content, altitude, and slope had significant gross effects, but only canopy density exhibited a significant net effect. Terrain affected diversity by restricting plantation, plantation in turn influenced soil properties and the two together affected diversity. Therefore, plantation was ultimately the fundamental driving factor for spatial heterogeneity in herbaceous plant diversity on the five islands.     

Variations of snow temperature and their influence on snow cover physical parameters in the Western Tianshan Mountains, China

This article discussed about snow temperature variations and their impact on snow cover parameters. Automatic temperature recorders were used to sample at 10-minute intervals at the Tianshan Station for Snow-cover and Avalanche Research, Chinese Academy of Sciences. 10-layer snow temperature and the snow cover parameters were measured by the snow property analyzer (Snow Fork) in its Stable period, Interim period and Snow melting period. Results indicate that the amplitude of the diurnal fluctuation in the temperature during Snow melting period is 1.62 times greater than that during Stable period. Time up to the peak temperature at the snow surface lags behind the peak solar radiation by more than 2.5 hours, and lags behind the peak atmospheric temperature by more than 0.2 hours during all three periods. The optimal fitted function of snow temperature profile becomes more complicated from Stable period to Snow melting period. 22 h temperature profiles in Stable period are the optimal fitted by cubic polynomial equation. In Interim period and Snow melting period, temperature profiles are optimal fitted by exponential equation between sunset and sunrise, and by Fourier function when solar radiation is strong. The vertical gradient in the snow temperature reaches its maximum value at the snow surface for three periods. The peak of this maximum value occurs during Stable period, and is 4.46 times greater than during Interim period. The absolute value of temperature gradient is lower than 0.1°C cm⁻¹ for 30 cm beneath snow surface. Snow temperature and temperature gradient in Stable period∼Interim period indirectly cause increase (decrease) of snow density mainly by increasing (decreasing) permittivity. While it dramatically increases its water content to change its permittivity and snow density in Snow melting period.     

Oasis System and Its Reasonable Development in Sangong River Watershed in North of the Tianshan Mountains, Xinjiang, China

An oasis is a kind of medium-sized or small-sized non-zonal landscape coming into being in the dry climate and supported by natural rivers in deserts, which is characterized by the comparatively high primary pro- ductivity and has the mesophytic plants or xero-mesophytic plants as the dominant vegetation (Jia, 1996). The oasis system, first of all, is a subsystem within the macro system of “mountain-oasis-desert” in the arid region. It is also a complex system where the natural and artificia…     

The characteristics and vertical zone spectrum of natural disasters in the Tianshan Mountains, Xinjiang

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Characterizing spatial patterns of precipitation based on corrected TRMM 3B43 data over the mid Tianshan Mountains of China

The poor distribution of meteorological stations results in a limited understanding of the precipitation pattern in the Tianshan Mountains. The spatial patterns of precipitation over the mid Tianshan Mountains were characterized based on the TRMM 3B43 monthly precipitation data. By comparing satellite estimates with observed data, it shows that TRMM 3B43 data underestimate the precipitation in mountain region. Regression models were developed to improve the TRMM 3B43 data, using geographic location and topographic variables extracted from DEM using GIS technology. The explained variance in observed precipitation was improved from 64% (from TRMM 3B43 products alone) to over 82% and the bias reduced by over 30% when location and topographic variables were added. We recalculated all the TRMM 3B43 monthly precipitation grids for the period 1998 to 2009 using the best regression models, and then studied the variation patterns of precipitation over the mid Tianshan Mountains. The results are well explained by a general understanding of the patterns of precipitation and orographic effects. This indicated that the Tianshan Mountains strongly influences the amount and distribution of precipitation in the region. This is highlighted by the confinement of the precipitation maxima to the windward (northern slope). And complex vertical changes in the provenance and distribution of precipitation, like that a negative increasing rate of precipitation in the vertical direction exists in the north but does not in south. The results have also revealed large gradients and different patterns in seasonal precipitation that are not simply related to elevation, the distribution of precipitation may also be affected by other seasonal factors such as the sources of moist air, wind direction and temperature.     

Elevational patterns of temperature and humidity in the middle Tianshan Mountain area in Central Asia

The vertical distribution of vegetation types along an elevational gradient in mountain areas largely depends on the elevational changes in air temperature and humidity. In this study, we presented the seasonal and diurnal variations in the elevational gradients of air temperature and humidity on the southern and northern slopes in the middle Tianshan Mountain Range using data collected throughout the year via HOBO data loggers. The measurements were conducted at 12 different elevations from 1548 to 3277 m from September 2004 to August 2005. The results showed that the annual mean air temperature decreased along the elevational gradients with temperature lapse rates of(0.71±0.20)°C/100 m and(0.59±0.05)°C/100 m on the northern and southern slopes, respectively. The annual mean absolute humidity significantly decreased with increasing elevation on the northern slope but showed no significant trend on the southern slope. The annual mean relative humidity did not show a significant trend on the northern slope but increased with increasing elevation on the southern slope. The mean air temperature lapse rate exhibited significant seasonal variation, which is steeper insummer and shallower in winter, and this value varied between 0.37°C/100 m and 0.75°C/100 m on the southern slope and between 0.30°C/100 m and 1.02°C/100 m on the northern slope. The mean absolute and relative humidity also exhibited significant seasonal variations on both slopes, with the maximum occurring in summer and the minimum occurring in winter or spring. The monthly diurnal range of air temperature on both slopes was higher in spring than in winter. The annual range of air temperature on the southern slope was higher than that on the northern slope. Our results suggest that significant spatiotemporal variations in humidity and temperature lapse rate are useful when analyzing the relationships between species range sizes and climate in mountain areas.     

Chemical characteristics and environmental significance of fresh snow deposition on Urumqi Glacier No. 1 of Tianshan Mountains, China

Ice and snow chemistry of alpine glaciers is crucial for the research of regional atmospheric environment change. Fresh snow samples were weekly collected from Urumqi Glacier No.1 in the Tianshan Mountains, Xin- jiang, China, and the chemical characteristics and seasonal variations of major ions, mineral dust, δ18O and trace metals were measured. Results show that the concentrations of major ions in the snow are Ca2+ SO42- NH4+ NO3- Cl- Na+ Mg2+ K+, in which Ca2+ is the dominant cation, and SO42-is the dominant anion. All major ions have close positive correlations with each other except NO3-. δ18O shows positive correlation with air temperature change during the study period. Mineral dust particle and major ionic concentrations in fresh snow have obvious seasonal change, with high concentration in spring but low concentration in summer and autumn, which indicates that the chemical mass input from Asian dust activity to snow is very significant. Temporal changes of trace metals in fresh snow, e.g., Cd, Pb, Zn, Al, Fe, have shown that human-induced pollution of central Asian region also has large contribution to the snow chemistry on alpine glaciers of the Tianshan Mountains.     

Morphological characteristics and environmental implications of phytoliths in topsoils from different vegetation zones on northern slope of Changbai Mountains,China

The Changbai Mountains,located in the temperate monsoon climate zone of East Asia,is an ideal loca-tion for the research on timberline response to global changes.In this study,the topsoils were collected from different vertical vegetation zones on the northern slope of the Changbai Mountains,Northeast China in August 2009,and phytoliths in the soil samples were extracted by using wet oxidation method and identified with Motic 2.0 microscope in laboratory.The results show that phytoliths are abundant in the ...     

Phytoplankton diversity in the East China Sea and Yellow Sea measured by PCR-DGGE and its relationships with environmental factors

Relationships between phytoplankton community composition and environmental variables in the East China Sea (ECS) and Yellow Sea (YS) were investigated using geochemical and molecular microbiology methods. The diversity of phytoplankton was characterized using cultivation-independent PCR-based denaturing gradient gel electrophoresis (DGGE). Groups resulting from unweighted pair-group method with arithmetic averages clustering of the DGGE profiles showed good consistency with the eco-environmental characteristics of the sea area they belonged to. Additionally, the clustering results based on DGGE fingerprinting and those based on morphological compositions were practically identical. The relationship of phytoplankton diversity to environmental factors was statistically analyzed. Temperature, dissolved inorganic nitrogen (DIN), and silicate-Si were found significantly related to the phytoplankton community composition. Canonical correspondence analysis (CCA) was performed to reveal the relationship between community composition and these three environmental factors. Generally, values of the ECS are clearly separated from those of the YS in the CCA biplot, due to mainly the effect of temperature and DIN.     

Phytoplankton diversity in the East China Sea and Yellow Sea measured by PCR-DGGE and its relationships with environmental factors

Relationships between phytoplankton community composition and environmental variables in the East China Sea (ECS) and Yellow Sea (YS) were investigated using geochemical and molecular microbiology methods. The diversity of phytoplankton was characterized using cultivation-independent PCR-based denaturing gradient gel electrophoresis (DGGE). Groups resulting from unweighted pair-group method with arithmetic averages clustering of the DGGE profiles showed good consistency with the eco-environmental characteristics of the sea area they belonged to. Additionally, the clustering results based on DGGE fingerprinting and those based on morphological compositions were practically identical. The relationship of phytoplankton diversity to environmental factors was statistically analyzed. Temperature, dissolved inorganic nitrogen (DIN), and silicate-Si were found significantly related to the phytoplankton community composition. Canonical correspondence analysis (CCA) was performed to reveal the relationship between community composition and these three environmental factors. Generally, values of the ECS are clearly separated from those of the YS in the CCA biplot, due to mainly the effect of temperature and DIN.     

Effects of environmental factors on tree seedling regeneration in a pine-oak mixed forest in the Qinling Mountains, China

Natural seedling regeneration and tree establishment are affected by various environmental factors.In this study,we established eight,eight,six,and four independent forest stands(each stand was further divided into five subplots) respectively based on the altitudinal gradient,stand density,slope location,and slope aspect to investigate the effects of environmental factors on tree seedling regeneration in a pine-oak mixed forest.The results indicated that the seedling density was significantly higher at altitudes of 1,283 m to 1,665 m,whereas the sapling density did not differ with altitudes.The seedling and sapling density decreased significantly at 1,835 m.The seedling densities on the upper slopes were much higher than those on the middle and lower slopes,whereas the sapling density had no difference.The sapling density decreased gradually from the southwest(20°-75°) whereas it increased on the shady slopes to the northeast(40°).The seedling density increased from southwest(20°) to northeast(40°).The seedling and sapling densities increased with the stand density(850 trees ha-1to 1,525 trees ha-1) whereas the sapling density was significantly lower in stands(1,900 trees ha-1).Principal components analysis showed that the slope aspect and stand density had more important roles in tree regeneration in this study region compared with the other two factors.Therefore,our findings suggest that it will be beneficial to keep stands at a moderate density on shady slopes.Appropriate thinning of higher density stands is also expected to promote the natural regeneration of pine-oak mixed forest.     

THE ORIGIN AND CHARACTERISTICS OF THE GLACIAL DEBRIS FLOW IN THE DUKU HIGHWAY OF TIANSHAN MOUNTAINS，

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Characterization of microbial community structure in rhizosphere soils of Cowskin Azalea (Rhododendron aureum Georgi) on northern slope of Changbai Mountains,China

The vegetation and soil are mutual environmental factors, soil characteristics, such as chemical properties and microorganism that affect the vegetation occurrence, development and succession speed. In this study, we evaluated the structure of microbial communities of rhizosphere of Cowskin Azalea(Rhododendron aureum Georgi) populations and compared with non-rhizosphere soils at four sample sites of the Changbai Mountains, China, and analyzed the correlation between chemical properties of soil and microbial communities. The results showed that microbial structure and soil chemical properties are significant superior to non-rhizosphere at all four sample sites. The rhizosphere microorganisms are mainly composed of bacteria, actinomycetes, followed by fungi least. The principal component analysis(PCA) biplot displayed that there are differences between rhizosphere and non-rhizosphere soils for microflora; Through correlation analysis, we found that the bacteria is clearly influenced by p H on the Changbai Mountains, besides p H, other soil features such as NO3–-N. These data highlight that R. aureum as the dominant vegetation living in the alpine tundra is a key factor in the formation of soil microorganism and improving soil fertility, and is of great significance for the maintenance of alpine tundra ecosystem.     

Long-term changes in sedimentary diatom assemblages and their environmental implications in the Changjiang (Yangtze) River estuary,China

Long-term data on diatom assemblages in a sediment core （60 cm） obtained from the Changjiang （Yangtze） River estuary were analyzed in order to assess the environmental changes that took place in the approximately 38 years （as determined by 210pb measurements）, i.e., between 1974 and 2012, of sediment accumulation. From the sediment core, 62 diatom taxa and genera were identified. The diatom biomass in the core generally increased beginning in the mid-1990s （core depth： 35 cm）, accompanied by a shift in the dominant species from Podosira stelliger and two species of Cyclotella （C. stylorum and C. striata） to Paralia sulcata, three species of Thalassiosira （ T. eccentria, I＂. oestrupii, and T. excentrica）, Actinoptychus undulates, and Thalassionema nitzschioides. The changes in both species diversity and abundance suggested that since the 1980s the estuary has undergone extensive eutrophication. This conclusion was supported by the increased proportion of planktonic species, another indicator of high nutrients inputs, in the Changjiang River estuary.     

Birds in rocky habitats of the Tatra Mountains (Carpathians): species diversity and multiple ecological relationships

Rocky habitats are regarded as biodiversity hot-spots.Along with high species diversity,diverse ecological relationships can be observed in these habitats.Large groups of bird species use rocks in various ways:as perching/roosting sites,breeding or foraging habitats,information exchange sites,display arenas or as sources of minerals and water.Because of the inaccessibility of these environments,their role and importance to animals has been underestimated.We evaluated the use of rocky habitats by birds in the Tatra Mountains(49°13'N,19°57'E,Carpathians,central Europe).Rocky habitats were used by 29 bird species,eight of which used cliffs directly(i.e.for nesting,foraging or resting).The number of species recorded as using cliffs was correlated with the surface area of the cliff face.A total of 20 forms of rocky habitat use were recorded,in five behavioural categories:vocalization,foraging,perching,flight and nesting.Prevailing behaviours were flying by a rock face,circling above the face,and vocalization on a tree/shrub growing next to a rock.Rocks provide a nesting habitat for specialized petrophilic species and permit the existence of numerous ecological relations between species and habitats.The results of this study show that rocky habitats support the diversity of ecological relationships.     

Observations and modeling of incoming longwave radiation to snow beneath forest canopies in the west Tianshan Mountains,China

Forest canopy reduces shortwave radiation and increases the incoming longwave radiation to snowpacks beneath forest canopies. Furthermore, the effect of forest canopy may be changed by complex topography. In this paper, we measured and simulated the incoming longwave radiation to snow beneath forest at different canopy openness in the west Tianshan Mountains, China(43°16'N, 84°24'E) during spring 2013. A sensitivity study was conducted to explore the way that terrain influenced the incoming longwave radiation to snow beneath forest canopies. In the simulation model, measurement datasets, including air temperature, incoming shortwave radiation above canopy, and longwave radiation enhanced by adjacent terrain, were applied to calculate the incoming longwave radiation to snow beneath forest canopy. The simulation results were consistent with the measurements on hourly scale and daily scale. The effect of longwave radiation enhanced by terrain was important than that of shortwave radiation above forest canopy with different openness except the 20% canopy openness. The longwave radiation enhanced due to adjacent terrain increases with the slope increase and temperature rise. When air temperature(or slope) is relatively low, thelongwave radiation enhanced by adjacent terrain is not sensitive to slope(or air temperature), but the sensitivity increases with the decrease of snow cover area on sunny slope. The effect of longwave radiation is especially sensitive when the snow cover on sunny slope melts completely. The effect of incoming shortwave radiation reflected by adjacent terrain on incoming longwave radiation to snow beneath forest canopies is more slight than that of the enhanced longwave radiation.