In order to understand the carbon pools in permafrost under the changing climate, the organic carbon storage in the active layers and its geomorphologic features at different elevations were investigated in the Eboling Mountain in the upper reaches of the Heihe River by both field exploration and laboratory experiment. The results indicated that there were significant periglacial phenomena and active seasonal freeze-thaw processes in the Eboling Mountain. The content of organic carbon in the active layer was high. The average depth of the active layer in the study region was 1.1 m. The content of organic matter of the soils in the active layer was about 72.1% on average for the study region. Consequently, carbon storage was estimated to be about 1.57 Mt C in the studied region of 2.5 km2 in area. Organic content varied with depths in the active layer. The organic content decreased with depth, but reached a high value in the vicinity of the permafrost table. While the elevation and soil moisture content control the organic carbon content of soil, micro-topography and lithology (soil types) have great effect on the organic content of soil in the active layer.
Nalati Mountain is located in the western Tianshan Mountains in Xinjiang Region, China. The permafrost changing process in this region influences the natural environment and engineering activities. Owing to many factors, such as transportation difficulties and scarcity of previous human activities, there are few researches about the permafrost and environment in this area. The permafrost distribution characteristics in Nalati Mountain and their main impact factors are studied systematically, combining with permafrost investigation of a transmission line which will be built from Yining to Kuche. It is found that permafrost in this region is typical mountain permafrost, of which the development area, types, ground ice characteristics and thermal regime all depend on altitude, topography and swamp condition. Any change in altitude, topography and swamp condition will result in change in permafrost distribution, permafrost type and ground ice. Meanwhile, there are many periglacial phenomena developing, such as solifluction terraces, solifluction lobes, stone rings and block streams. Depending on slope aspect, vegetation, water and other factors, the active layer depth varies from 0.7 m to 4.5 m, and the thickness of permafrost on south slopes increases from about 20~22 m at the lower limit (3 000 m) of continuous permafrost to 70~100 m at the altitude of 3 300 m. According to temperature data, it is found that regional annual mean air temperature has rapidly increased since 1985, with a rate of about 0.088℃·5a-1. Therefore, some features of permafrost degradation can be seen, such as ground temperature rising, degradation of marsh wetland and vegetation and detachment of frozen ground.
Permafrost and seasonally frozen ground have a dramatic influence on surface hydrological processes, ecosystems, carbon cycle, and infrastructures in cold regions. The upper reaches of the Heihe River are located in the eastern part of the Qilian Mountains, where climate is cold and semi-arid. The study of permafrost distribution in Heihe River basin is of great importance for systematically understanding the regional eco-hydrological process, climate and environmental changes, water resources assessment and construction, etc. Field investigation on distribution of permafrost had been conducted over the upper reaches of the river during the summer of 2011. Seven boreholes ranging from 20 to 100 m in depths were drilled in early August, 2011. Based on borehole drilling information and temperature profiles measured at least two months after the drilling, it is found that the lower bound of permafrost is at between 3 650 m and 3 700 m a. s. l. Depending on altitude, the active layer depth varies from 1.6 m at 4 132 m a. s. l. to about 4.0 m near the lower bound of permafrost at a little above 3 650 m a. s. l. Mean annual ground temperatures at the depth of zero annual amplitude increases from -1.7℃ at 4 132 m a. s. l. to near 0.0℃ at the lower bound of permafrost. Permafrost depth decreases from more than 100 m at 4 132 m a. s. l. to 0.0 m as moving down to 3 650 m a. s. l. At the same time, the other local factors, such as slope, aspect, soil type, soil water(ice)content, vegetation and river channel, may also have significant effect on permafrost conditions.
According to the precipitation observed by Thies disdrometer, T-200B and TE525 rain gauges from November 2011 to September 2012 in Beiluhe, Tibetan Plateau. It is found that during the monitoring period precipitation in the study area was approximately 466.56 mm, much higher than that in the previous years. It means that precipitation in 2012 was a maximum. Comparing three records observed by the three instruments, one can see that: For observing solid precipitation, the observation of TE525 rain gauge is the worst. The precipitation observed by T-200B is slightly smaller than that by Thies disdrometer. Solid precipitation observed by T-200B was corrected with Smith's and Jimmy's correction formulas, respectively. After correcting, it is found that precipitation observed by Thies disdrometer has a good consistency with that from the Jimmy corrected T-200B. For measuring sleet, Thies disdrometer obtains higher precipitation owing to misreading the type of precipitation and the diameter of particles. Anyway, the liquid precipitations observed by the three instruments are in good agreement. However, when the hourly rainfall is higher than 2 mm, precipitation obtained from the disdrometer is about 20% smaller than that from the rain gauge. The impact of blowing snow on the observation of Thies disdrometer was analyzed also. The preliminary view is that the particle diameter of the blowing snow is mainly less than 0.5 mm.
Combining brightness temperature data at 19 GHz and 37 GHz vertical and horizontal polarization channel of AMSR-E data and measured snow depth data from 45 meteorological stations in Northern Xinjiang Region in 2007-2009 snow season (December-February), a snow depth retrieval model was established based on AMSR-E brightness temperature data. The accuracy of the model was evaluated. The result shows the negative average error of retrieval snow depth is -5.1 cm and RMSE is only 6.1 cm for snow depth ranging from 3 to 10 cm. When snow depth is between 11 and 30 cm, the average error of retrieval snow depth is 2.6 cm only, and its RMSE, positive average error and absolute average error are all less. When snow depth is larger than 30 cm, the errors of retrieval snow depth are larger. Comparing the retrieval snow depth with the observed data, it is found that the simulations show a great agreement with the observations at meteorological stations in Northern Xinjiang Region. This basically reflects the snow depth distribution in Northern Xinjiang Region. Comparing Chang algorithm with the retrieval model in this study reveals that the latter is superior to the former and can describe snow depth variation characteristics well in Northern Xinjiang Region. Meanwhile, an average snow depth distribution map and a most heavy snow depth map are drawn by using synthetic method from five snow seasons (2006-2010). The maps show that snow cover is mainly distributed in the Altay Mountains in the north and the Tianshan Mountains in the south, with a maximum in the Altay Mountains. The snow cover is thin in the hinterland of Junggar basin and Karamay area.
Ordos is one of the regions that seriously suffered from desertification in China. Carrying out the research on the desertification dynamics monitoring and its relationship with driving forces in Ordos has significance for understanding the process of desertification, making and evaluating the policies for desertification rehabilitation. In this paper, based on using the MODIS data to monitor the desertification dynamics in Ordos from 2000 to 2010, the changing trends of net primary productivity due to climate change and human activities for the lands experienced desertification reversion and expansion is analyzed, and the desertification dynamics in Ordos from 2000 to 2010 and their relationship with climate change and human activities are quantitatively assessed. It is found that the area of desertification land in Ordos did not changed obviously from 2000 to 2010, but the degree of desertification reversed significantly, and area of lands experienced desertification reversion reached 47 057 km2 (accounting for 54.2% of the total area of Ordos), which was almost three times higher than that of desertification expansion. Climate change was the dominated factor that induced the desertification reversion from 2000 to 2010, which almost could be attributed to the increasing precipitation and the decreasing of wind speed in spring from 2000 to 2010. Also the implement of ecological protection policies, such as rangeland enclosure and grain for green and its' coupling with good climate condition, accelerated the desertification reversion. Human activities was the dominant factor that induced the desertification expansion from 2000 to 2010, which mainly attributed to the implementation of those ecological protection policies ineffective and the environment damage due to development of energy and mining industries, and the lands with desertification expansion totally induced by human activities mainly distributed in the north of Ordos.
In this paper, the calculations of some parameters such as brightness temperature, atmospheric transmittance, surface emissivity and vegetation index are discussed. Then the land surface temperatures are calculated by using MODIS split windows algorithm of NASA on the base of cloudless MODIS thermal infrared data which were collected seasonally in 2010. It is found that the distribution of land surface temperatures is very different in different seasons and different regions. In spring, the land surface temperature varies between -13.45℃ and 29.27℃. In summer, it varies between -3.75℃ and 56.29℃. In autumn, it varies between -10.15℃ and 32.67℃. In winter, it varies between -17.15℃ and 12.75℃. There are three land surface temperature zones from south to north. The temperature is very high in Wuwei, Minqin and Gulang oasis, where heat is rich and the domino effect among water, soil and vegetation are obvious. In the downstream Tengger Desert and Badain Jaran Desert, land surface temperature is extremely high in summer. Comparatively, in Qilian Mountains the temperature is very low because of perennial snow, high elevation and special land surface vegetation. In addition, MODIS data are able to supply a new way for monitoring thermal environmental change in a small basin. Especially, the derived results will be improved a lot if combine the MODIS data and surface observation.
Snow cover is an important factor affecting climate. Using the HJ satellite with higher spatial and temporal resolution for snow cover mapping has a great significance to promoting China's own remote sensing satellites in the field of snow monitoring. In this paper, the normalized difference snow index (NDSI) method based on HJ-1B satellite data is used to study the snow cover mapping algorithm in Darlag County, Qinghai Province. The accuracies of MODIS daily snow cover map and the HJ-1B snow cover map are compared. It is found that: 1) the suitable NDSI threshold of HJ-1B snow cover mapping algorithm is 0.37 and the total classification accuracy is 97.97%. 2) Compared with the MODIS daily snow cover map, the HJ-1B snow cover map has higher coherence with "true value" snow cover image with Khat coefficient of 0.911, more than that of MODIS daily snow cover map, 0.817. The accuracy of snow cover mapping algorithm based on HJ-1B is established in this study, which is reliable for snow cover dynamic monitoring in the study area. The HJ-1B with higher spatial and temporal resolution can improve the accuracy of snow cover area monitoring. However, the terrain is an important factor for snow cover monitoring accuracy when using HJ-1B data. The snow classification error increases with slope, especially the commission error.
0-cm soil temperature is the upper boundary condition of many permafrost models. Continuous, high-quality 0-cm soil temperature data are necessary inputs to simulate permafrost distribution. However, owing to the influence of complex underlying surface, remote sensing approaches cannot provide reliable 0-cm soil temperature. In this study, in order to estimate 0-cm soil temperature, adaptive network-fuzzy inference system (ANFIS) combining with the data measured in the Tibetan Plateau is used to establish the relations between remote sensing land surface temperature (LST) and 0-cm soil temperature. In this paper, different parameter combinations of ANFIS are examined, and a Wavelet-ANFIS model established by optimized wavelet functions, wavelet windows and wavelet layers is found able to estimate the 0-cm soil temperature more accurately. A comparison analysis of the estimated results and the 0-cm soil temperatures measured at the meteorological sites shows that the approach can achieve desirable estimation with an absolute error less than 2 K and a correlation coefficient greater than 0.98. In view of the original MODIS LST error range from 0 to 2 K, the proposed method may provide more accurate 0-m soil temperature inputs to permafrost models.
In order to study the process of soil with vertical zonation in the Zhagana in Diebu mountain area, Gansu Province, the vertical sampling for the different altitude and horizontal sampling for different vegetation and geographical were taken. On the basis of GIS, topographic and forest form map of study area were digitized, and the terrain factor such as altitude, slope aspect and gradient were extracted, and the land use map of study area was get by clipping the Chinese land use type map. Then the influence factors of the process of soil with vertical zonation were analyzed and discussed by superimposing the sampling point on the different terrain and land use map. The results show that: the content of organic carbon and total nitrogen showed excellent linear positive correlation (r=0.95), and increased with the elevating of altitude. In addition, in the same altitude range, the content of organic carbon changes regularly based on the change of land use type and slope aspects. The soil organic carbon content in different land use types were in the order of: forest land>alpine meadow>High grass coverage>rural dweller dot>plain farmland>mountain farmland. The soil organic carbon content in different aspects was in the order of: shady slope>half shady slope>half sunny slope>sunny slope.
Permafrost is well developed in the Northern Da Hinggan Mountains, Northeast China. However, its development and distribution are significantly affected by local factors such as vegetation, snow cover and so on. It is also known as Xing'an-Baikal type permafrost consequently. In recent years, permafrost monitoring systems have been gradually established in the northern Da Hinggan Mountains, including ground temperature monitoring system, automatic meteorological stations, snow properties observation system, temperatures and moisture of active layer observation system and thaw settlement monitoring system. Up to now, a series of data have been collected for analysis, and meaningful results have been obtained too.
Surface ablation has great impact on the Greenland Ice Sheet (GrIS) mass balance and becomes the focus of GrIS research in recent years. The production, transportation and release of meltwater are the keys to understand the potential impact of the GrIS surface ablation. These hydrological processes could illustrate the following problems: How much meltwater is produced atop the GrIS? What are the characteristics of meltwater-formed supraglacial hydrological system? How does the meltwater influence the GrIS motion? Ablation modeling is an important approach to acquire surface ablation information. Areas, depths, and volumes of supraglacial lakes extracted from remotely sensed imageries provide direct meltwater information. The spatial distribution of supraglacial lakes, supraglacial streams, moulins and crevasses demonstrates the characteristics of supraglacial hydrological system, which is in charge of meltwater transportation. The release of meltwater into englacial and subglacial ice sheet has important but undetermined impact on the GrIS motion. The relationship between surface meltwater volume and GrIS motion velocity is employed to understand the impact.
In this paper, remote sensing satellites, sensors used in monitoring glacier change and methods of extracting glacier information are summarized. Various approaches are evaluated synthetically. It is considered that the method of band ratio is the best among the conventional methods. The new methods of object-oriented classification and SAR interferometry have improved the accuracy of extracting glacier information to a certain extent. However, superglacial debris is still a difficulty in automatic recognition of glacier information. Automatic and semi-automatic methods have been developed for debris-covered glaciers. However, the methods are immature and out of universality. Obstacles of snow cover and superglacial debris and hard ground verification of glacier information derived from satellite images still need to overcome. Therefore, to develop more advanced and more sophisticated methods will be an important issue in glacier research. It is expected that rough set theory and waveform of ICESAT satellite will improve the accuracy of extracting glacier information.
Glaciers serve as very active geomorphic agents in shaping the landforms of glaciated regions, and are responsible for producing some of the most spectacular landscapes on Earth. During the glacial-interglacial cycles of the Quaternary, Glaciers advanced and retreated dramatically. As a consequence, abundant glacial landforms and sediments were presented in the glaciated regions. Studies of them can define the time, extent, properties and type of ancient glaciers. The relevant information could be used to reconstruct the spatial and temporal variations of the palaeo-glaciations. In tectonically active regions, these studies also can provide potential information on the history of uplift. In August, 2012, Chinese scholars, whose studies focus on the glacial geomorphology and environmental variation, gathered in Lanzhou to review the achievements have been made during the past several years and to discuss the research emphases of present and in the future. Participants considered that research on Quaternary glaciations has entered a new stage, when accurate dating of glacial landforms and sediments become an emphasis. The dating techniques, including cosmogenic radionuclides (CRN), optically stimulated luminescence (OSL), and electron spin resonance (ESR), have been developed, refined and widely applied. These dating techniques can potentially provide constraints on the ages of glacial sediments and landforms, which have promoted significant advances in research on Quaternary glaciations in China. Several works should be done at present and in the future. Firstly, to establish an accurate chronology framework for Quaternary glaciations is the critical work for Chinese scholars at present. Secondly, the timing of the oldest glaciations in the Tibetan Plateau and the bordering mountains is a fundamental requirement in understanding the glacier development coupling the uplift of the plateau, which will provide insight into understanding the glacier development in China. Thirdly, more work should be done to make clear that there were no palaeo-glaciers developed in the middle-low mountainous areas in the Eastern China beyond (105°E), except for the Changbai Mountain, Helan Mountain, Taibai Mountain and Taiwan Mountains. Chinese scholars should do more work to popularize the knowledge of Quaternary Glaciations and their related environments.
The Noah land surface model (LSM) is widely used to simulate water-heat processes in global or regional land surface studies. However, there are few studies on its applicability in cold alpine area characterized by high elevation and cold climate condition. So far, no study has been conducted using Noah LSM in the upper reaches of the Heihe River, a typical cold alpine area. In this paper, based on the observation from 2008 to 2009, Noah LSM was applied to simulate water-heat processes in two typical sites, e.g., Dadongshu Pass Site and Arou Site, located in the upper reaches of the Heihe River. A comparison between simulated and observed soil temperatures and soil liquid contents shows that Noah LSM is able to describe the actual water and heat processes in such alpine cold regions. Soil temperature is simulated generally well, with a few biases in winter. Simulated soil liquid content is generally lower than observed one. Large biases in soil liquid simulation in the upper layers can be seen obviously in spring, when frozen soil begins to thaw. Abovementioned simulation problems are largely related with the insufficient considerations of Noah LSM in soil profile heterogeneity, resulting in incorrect estimating ice content in spring, as well as with the inaccurate precipitation observation, especially in winter. Apart from the applicability of Noah LSM, observation quality is also discussed in this paper.
The water storage change data from 2003 to 2008 in the source regions of the Yellow River is retrieved from GRACE satellite data. Furthermore, the monthly real evaporation in the source regions is estimated according to water balance equation by using runoff and precipitation data. It is found that they are consistent better and correlative with not only the observation with evaporation pan (20 cm), but also with the simulated result of SiB2 model. The annual average evaporation in Tangnag basin is nearly 506.4 mm, of which 130.9 mm in spring (Mar., Apr. and May), 275.2 mm in summer (June, July and Aug.), 74.3 mm in autumn (Sep., Oct. and Nov.) and 26.1mm in winter (Dec., Jan. and Feb.). From 2003 to 2008, precipitation had increased slightly and real evaporation had decreased obviously; precipitation had increased with a rate of 0.019 mm·month-1, water storage had changed with a rate of 0.51 mm/month, while evaporation had decreased with a rate of 0.52 mm/month. During the study period, the water storage in the source regions of the Yellow River had increased about 496.6×104 m3, equivalent to 82.6×104 m3·a-1. Precipitation had changed not so much. However, decline of evaporation and degradation of permafrost had led storage capacity increasing significantly and then surface runoff increasing.
Stable hydrogen and oxygen isotopes (δD and δ18O) of plant stem water and potential water sources were analyzed to investigate the water sources of different plant species in three typical habitats (oasis, oasis-desert transitional zone and desert) in the Heihe River basin. It is found that plants in the desert habitat absorb water mostly from deeper soil (>160 cm). In the oasis-desert transitional zone, Artemisia arenaria and Calligonum mongolicum are likely absorb water mainly from the soil about 20~40 cm in depth, Haloxylon ammodendron absorbs water primarily from 60~80 cm in depth, Hedysarum scoparium may absorb water from soil about 100 cm in depth and Tamarix ramosissima obtain water from deeper soil (>120 cm). Plants in the oasis habitat absorb soil water mainly from 0 to 100 cm deep. Calamagrostis pseudophragmites absorbs water about 20 cm in depth, Zea mays extracts soil water from the depth of 20~40 cm, Tamarix ramosissima and Populus simonii absorb soil water about 60 cm deep and Gossypium hirsutum absorbs water from soil about 80 cm in depth. Plant water sources in the three studied habitats are coincidence with soil water content. It is believed that water competition may exist among plant species which absorb water from similar soil depth. The depth of plant water sources of different habitats is gradually changed in the order from deep to shallow: desert, oasis-desert transitional zone and oasis. This order also exists in different habitats for the same plant species. It is illustrated that plant stable hydrogen and oxygen isotope composition can be used to indicate the processes of oasisization and desertification in arid regions.
Water consumption in agriculture is the most part of water resources consumption in both global and regional scales. Valuation of agricultural water productivity is of importance for improving the local agricultural water resources utilization, especially in the arid areas. In this paper, first, the basic concept of crop water productivity (CWP) is introduced, and the core of its affecting factors is analyzed. Then, the evaluation methods of CWP are summarized and divided into the harvest method, the model method and the integrated RS (or GIS) method. The advantages and disadvantages of these three methods are discussed. Finally, the development trend of research on CWP is prospected, and it is considered that the method of RS (or GIS) combined with model method to estimate the CWP will be better in the future.
Remote sensing technology has become an important tool to dynamically monitor the processes of thermokarst lakes in the Tibetan Plateau, from which macroscopical spatial data can be obtained rapidly. In this work, the data processing methods including data correcting, data fusion and information extraction were proposed and discussed based on the characteristics of the high spatial resolution remote sensing data from QuickBird and SPOT-5, combining with character factors of the thermokarst lakes in the Qinghai-Tibet Plateau. Furthermore, a most suitable procedure was applied to investigate the change of the thermokarst lakes in a limited range, 63 km2 in area, located in the north of the Beiluhe River basin from 2006 to 2009. The area is from Honglianghe to Xiushuihe along the Qinghai-Tibet Highway. The results show that the amount and total area of the thermokarst lakes have slightly increased.
The triaxial creep tests on laboratory-prepared frozen clay specimens are carried out with MTS-810 hydraulic servo material test machine, and then creep curves of frozen clay under complex stress state are obtained. The results show that the creep deformation of frozen soil has strong temperature sensitivity; the higher the temperature is, the stronger the temperature sensitivity is; at a same temperature, the larger the load is, the bigger the deformation is. Using relevant theory, the nonlinear mathematical model of triaxial creep of frozen clay under complex stress state is derived. Then equation's parameters of the model are obtained through fitting function of MATLAB software. There is a tight relationship between the model parameters and temperature. Thus a mathematical expression between the two is established. The fitting accuracies between the simulated curves and the experimental curves are high. The established mathematical model can accurately describe the creep law of frozen soil, and will provide effective theory for predicting the deformation in actual frozen soil engineering.
There are abundant mineral resources in permafrost region of China and the mineral resources exploitation has become one of mainly economic developmental types. As a main resource of energy and raw materials, the mineral resources exploitation promotes economic growth of the western China. However, since the ecosystem of the Qinghai-Tibetan Plateau are very fragile and sensitive to changes in climate and ground surface conditions, a series of environmental geological problems caused by mining resources exploitation, such as the destruction of the ecosystem environment, the destroy of resources and geological hazard. With a large of energy quantity demanded and gradually decreasing of yield of open-pit mining, researches on underground mining are even more badly needed in permafrost region. Based on the relevant research achievements in unfrozen earth area and the meteorological data of Jiangcang coalfield in permafrost area, using calculation program of airflow temperature in an intake shaft, varying law of airflow temperature in an intake shaft was studied by the use of critical temperature. The factors of influencing the airflow temperature were determined and the fitted equation of convection heat transfer boundary conditions between mining ventilation and the surrounding rock of the shaft in permafrost regions was found. The calculation methods and results are given as references for the next study on thermal influence of the surrounding rock of shaft in permafrost regions under the action of mining ventilation.
Mining in permafrost regions with ventilation will change the heat balance of the surrounding rock of shaft, the upper limit of permafrost and the seasonal-thawing depth of permafrost around the shaft. The stability of shaft lining structure will be affected by the heat balance change. So it is necessary to study the permafrost temperature field changing with mining ventilation. Based on finite element analysis software ANSYS, a two-dimensional calculation model has been established in terms of mining conditions, position of test stope as well as mining ventilation effect range of a coalfield located in permafrost region. The temperature characteristics of the surrounding rock of shaft in permafrost have been numerically analyzed using the enthalpy-based finite element method, The thermal effect of mining ventilation on the surrounding rock is analyzed. The calculation methods and results are valuable for the following shaft support design of underground mining in permafrost regions.
In this paper, the characteristics of CT technology are introduced, and the history and current situation of using CT technology on frozen soil study are reviewed, including auxiliary equipment specially designed for frozen soil testing, using CT number to analyze frozen soil internal structure change, using CT number to define and explore damage evolution, and using CT images to observe soil mesostructure. In addition, representative achievements in frozen soil study in relation to CT technology are also summarized in this paper. Finally, problems, possible solutions and challenges in frozen soil study by using CT are pointed out. It is emphatically introduced how to obtain higher quality CT images and how to process digital CT images of frozen soil. The relations between CT number and each component of frozen soil specimens are also discussed. It is found that CT technology is one of the most ideal and effective technologies for studying frozen soil mesostructure as a non-destructive manner. CT technology will play more significant role in the study of frozen soil by means of auxiliary equipment and digital images processing.
International practices of transmission projects in permafrost regions have significance to similar projects or relative research in China.Take the transmission projects in Yukon Territory of Canada and Alaska as examples, relative practice and successful experiences are systematically analyzed and summarized covering the whole process from pre-project program, project design and construction to maintenance during operation.Then, the important lessons which can be learned from international practices are discussed from the following respects: improvement of project evaluation system, establishment of construction criterions and technical standards, environmental risk control and maintaining safety of project operation and management.
The physicochemical characteristics, the number of culturable nitrogen-fixing bacteria and the community structure of nitrogen-fixing (nifH) genes in the alkali soils of alpine steppe in the Qilian Mountains are investigated in the present study. It is found that the number of culturable nitrogen-fixing bacteria is between 3.6×105~0.21×105 CFUs5g-1 within the depth of 0-40 cm. The number of nitrogen-fixing bacteria decreases with soil depth in three soil samples, except one sample (AQ4) at the altitude of 3 001 m.The number of nitrogen-fixing bacteria has a significant positive correlation with the underground biomass, and positive correlations with organic carbon, soluble organic nitrogen, rapidly available phosphorus and rapidly available potassium. However, it has negative correlations with soil pH value and total salt. Gene sequencing shows that in a community structure of 37 nitrogen-fixing (nifH) genes there are Cyanobacteria genes (41%), Proteobacteria genes (8%), Firmicutes genes (14%) and unknown bacterium genes (37%). Cyanobacteria genes exist in all soil samples, except for the sample AQ4, and are dominate nitrogen-fixing (nifH) genes in the sample AQ1. It is also found four new nitrogen-fixing (nifH) genes. They are AQ1-12(KC412109), Q4-3(KC412133), AQ4-4(KC412133) and AQ4-5(KC412133), among which AQ4-3(KC412133), AQ4-4(KC412133) and AQ4-5(KC412133) are the dominate genes in sample AQ4.
Microorganisms in the glacier foreland can promote the soil formation, participate in biogeochemical cycles and play an important role in the subsequent biological settlement and growth process. Over the past 100 years, the global average temperature has increased by 0.74℃. One consequence of this temperature increase is that glaciers have retreated in many mountainous areas all over the world. The studies of the primary succession of microflora in the glacier foreland have become the research focus in recent years. In this paper, the microbial community and quantity variation in the glacier foreland, the role of microbial in the soil formation are reviewed. The change and function of N cycle relating microbial in the glacier foreland primary succession are also reviewed. The aim is to understand the rule and function of microbial succession in the glacier foreland and to provide some theoretical basis to ascertain microbial ecological functions in this special ecosystem.
Matching manager's management style with environment is the key of effective management. The optimal water resources management style in Zhangye Municipality located in the middle reaches of the Heihe River is evaluated by using fuzzy network analysis and culture theory. Based on cultural theories, an evaluation index system of water resources management style is established by using theoretical analysis and frequency analysis. The weight of each index is determined by using analytic network process. Based on the results of analytic network process, four management styles, namely, individualist, fatalist, hierarchist and egalitarian, are analyzed by using fuzzy comprehensive evaluation method, and then ranked them according to their scores. The results show that hierarchist gains the highest score, becoming the best management style. Therefore, in the process of water resources management in the middle reaches of the Heihe River, hierarchist management style would be accepted, which may provide the theoretical basis for personnel assignation, talent hiring and training direction in the water resources management department and also may improve the efficiency of water resources management.
Based on the analysis of the definition and characteristics of city compactness includes the economy compactness, the land use compactness and the population compactness, in this paper, urban compactness evaluation indicators of China's cities are built to evaluate the urban compactness of 287 prefecture-level cities or above in China by using principal component analysis. Also their spatial spillover effects are studied. According to the principle of eigenvalue greater than 1, three main components, i.e., economic development component, urban land use component and population density component are selected, of which the cumulative variance contribution rate is up to 80.2%. General statistical characteristics of the three main components show that the frequency distribution of component values are skewed, with data deviated from the center and asymmetric morphology. After calculating the comprehensive scores of every city, ESDA-GIS framework may use to analyze spatial difference of the urban compactness for prefecture-level cities or above in China in 2009. The Exploratory Spatial Data Analysis, which is based on the computing spatial autocorrelation and spatial heterogeneity, is also used to detect the geographical dynamics of regional disparity patterns. Moran' s I scatter plots and LISA(Local Indicators of Spatial Association) cluster are applied to test the local pattern of urban compactness. The results indicate that there are two spatial differentiation zones of urban compactness divided by Tahe-Pingxiang Line. Urban agglomeration synthetic compactness appears a discrepancy tendency, gradually decreasing from east to west and from south to north. There are high values of Moran's I contiguously aggregated in the Pearl River Delta and Yangtze River Delta. Urban compactness shows zonal distribution with obvious hot spots-sub-hotspots-sub-cold spots-cold spots from east to west. Economic development level, land use structure and population density are important factors that determine the urban compactness of prefecture-level cities or above in China, of which the land use structure seems relatively balanced.
Image space is people's subjective understanding about the objective world and the organic unity of the external image and the inherent implication, which often provides a reference for the destination construction and development by image groups' perception of their surrounding environment mostly. Taking the perspective of image space, implementing questionnaire and interview survey and adopting the methods of photo selection and image mental maps, a study of image space in Langmusi Town was made in the paper, in order to achieve healthy and sustained development of the Tibetan national tourist town. The research indicates that the spatial structure of image space is characterized by "Three Space" (Buddhist temple space, traditional residential space and the folk commercial space) and a Mandala image schema. In this article, some development ideas are proposed for the three spaces, and the way of coordination and organization of different spaces are also proposed, in order to achieve healthy and sustained development in the national tourist town through optimizing and managing the structure of image spaces.
Spatial and temporal distributions of both physical and socioeconomic phenomena can be approximated by functions depended on location in a multi-dimensional space as multivariate scalar, vector or tensor fields. Collection of spatial GDP data is problematic, because of various shortcomings in the data collection process. A model is developed for creating a disaggregated map of estimated GDP for towns and then a distribution map of GDP is got.
Firstly, a regression model is developed to calibrate the official GDP at township level in the study area with the sum of light emissions, and subsequently unique coefficients are derived.The spatial population grid and nighttime light satellite imagery are used to represent primary industry and other industries. Multiplying the unique coefficients with the sum of light emissions provides an estimate of total economic activity, from which a spatially disaggregated GDP map of total economic activity may generate based on the grid of 500 m×500 m. The average GDP value of a township is 3.72 million Yuan, with a Standard Deviation of 0.34 million Yuan.
