The leaf thickness, cuticle thickness, palisade tissue thickness, palisade tissue cell length, palisade tissue cell wide, palisade tissue cell density and tissue structure tense ratio(CTR ) of six desert shrubs (Atripldex canescens, Caragana microphylla, Hedysarum leave, Tamarix chinensis, Buddleja alternifolia and Caryopteris mongolica) in Hobq Desert are observed under microscopy. Comparison of the characteristics of leaf anatomical structure shows that the leaf thickness of Tamarix chinensis is greater than that of the other 5 species, and leaf thickness of Buddleja alternifolia is the smallest; the cuticle thickness of Buddleja alternifolia is the biggest; the sequence of the ratio of cuticle thickness to leaf thickness is Buddleja alternifolia>Atripldex canescens>Tamarix chinensis>Caragana microphylla>Caryopteris mongolica>Hedysarum leave; the sequence of CTR is Caryopteris mongolica>Hedysarum laeve>Caragana microphylla>Buddleja alternifolia>Atripldex canescens>Tamarix chinensis. The comprehensive evaluation result of drought resistance capacity of these six desert shrubs is Hedysarum laeve>Atripldex canescens>Tamarix chinensis>Caryopteris mongolica>Caragana microphylla>Buddleja alternifolia based the calculation of Membership Function.

Soil carbon plays an important role in global carbon cycle. Soil respiration is hot topic in the area of carbon cycle research. It has become the largest source that terrestrial ecosystems releases CO2 to atmosphere, and is also an index for many functional processes of ecosystems. Based on the research on soil respiration of other scholars, factors having an effect on soil respiration are temperature, humidity, the types of community, physical and chemical property of soil, etc, respectively. Some methods of measuring soil respiration and its characteristic were introduced. Finally, the paper made a summary of achievements on soil respiration in the world and suggested emphases of further study in this field.

Over the past 50 years the desert riparian vegetation in the lower reaches of the Tarim River in western China degraded due to irrational management regimes. Little is known about the effect of vegetation degradation level on the structure and performance of soil seed bank in desert riparian vegetation. A field experiment was established to test this effect. The results showed that the density (892.6 seeds\5m-2) and species number(11 species) of soil seed banks in the moderate-desertification transects are relatively high. With the increase of desertification level the species abundance, density and biodiversity index of soil seed bank decrease. There is no significant effect of desertification intensity on the vertical density distribution of soil seed bank. However, over 70% of seeds were concentrated in the upper oil layer (0~2 cm). Plots at extreme desertification level showed a greater proportion of annual herbs compared to plots at heavy or moderate desertification levels, whereas perennial herbs and shrubs followed the inverse trend. These results indicate that the potential of the natural vegetation to restore naturally decreases with the increase of desertification level.

The authors reviewed the development of concept of water use efficiency (WUE) and the research progress on water use efficiency of plant, and analyzed the significance of studying WUE. The factors influencing water use efficiency were analyzed from both botanic and environmental aspects. The botanic factors include physiological ones, the period of growth and development, approaches of photosynthesis, life forms, and characters for fixing nitrogen and invading, and breeds of plants. The environmental ones involve moisture, radiation, atmospheric CO2 concentration, air temperature, leaf temperature, planting regime, irrigation regime, fertilization, soil nutrient content and intensity of disturbance. In addition, the authors have summarized the methods to measure water use efficiency: field measurement, leaf gas change technology and stable carbon isotope technology; have further discussed their advantages and shortcomings respectively; finally, emphasized the difficulty in the study on scale extending and the necessity in arid and semi-arid zone, and brang forth a prospect of research trends on water use efficiency in the near future, especially on vegetation restoration in arid and semi-arid zone.

Annual net primary productivity (NPP) of terrestrial vegetation is the net amount of carbon fixed by plant photosynthesis. NPP is an important index in global change ecology. This paper summarized the advance in research on net primary productivity of terrestrial vegetation over globe or regions in home and abroad for the recent years. It also analyzed the application of remote sensing and geographic information system in NPP research. At the same time, the feature and the trend of researching NPP are discussed.

In this paper, based on meteorological data from the Zhurihe meteorological station and normalized difference vegetation index (NDVI), leaf area index (LAI), net primary productivity (NPP) in Zhurihe from 2002 to 2010, the characteristics of sand-dust weather and the relationships between land surface conditions and sand-dust weather in zhurihe were analyzed. The threshold wind speed is 9.4 m·s-1 in Zhurihe. The frequency of sand-dust weather and strong wind is fluctuant from 2002 to 2010. Sand-dust weather frequency is positively correlated with strong wind. Wind of more than 18 m·s-1 can easily lead to sand-dust weather. The normalized dust outbreak frequency (NfDO) is defined as the ratio of sand-dust weather frequency to strong wind frequency. NfDO in spring was always low in Zhurihe, when the accumulated precipitation amount from June to August, maximum NDVI, maximum LAI and maximum NPP from June to August during the previous year exceeded their thresholds (100 mm,0.24,0.3 and 0.6 g C·m-2·d-1, respectively). It suggests that the precipitation amount during the vegetation growing season predominantly controls plant production in summer and the land erodibility in spring of the next year and suppress sand-dust outbreak.

On the basis of published papers about sandstorms in China, we summarized the characteristics of the space-time distribution, sand sources and migration path of sand dust in China and the research methods. The review indicated that the distribution area of sandstorm was identical with distribution of the desert, sandy land and Gobi in northern China, and there were 4 main sand dust source areas. In particular, we pointed out that the dry up lakes, abandoned lands and gravel pastures all may turn to be main sand source areas for the sandstorms in northeast China. There were three main paths of sand storm migration and their characteristics were concluded respectively in the paper. According to the characteristics and application examples of the sand dust source area tracer method, we also pointed out their application conditions and scope. This will provided academic bases and references for further research and sandstorm prevention.

Oasification and desertification are the two contrarily developing but correlated processes of arid regions. The area of osification of China has increased to 10.4×104 km2 from 2.5×104 km2 of the late 1950s in the past 60 years, simultaneously, the area of desertification has expanded from 5.3×104 km2 to 11.4×104 km2 and the arable land area suffered from salinization has reached up to 1.5×104 km2, accounting for 30% of the total arable land area. The process of oasification has improved the local eco\|environment and extended the living space of human being, but the planless and low\|level development of oases has lowered the oasis stability and triggered a series of eco\|environmental problems, in which desertification involved. This paper reviewed the research progresses on oasification and desertification, and has put forward a general thinking and some important subjects waiting for performing in the near future against several key problems. The prospect of researches in this field lies in disclosing the forming of oasification and desertification as well as their evolution mechanism on the premise of completely cognizing the processes of Water\|Soil\|Atmosphere\|Biology and their interaction under functioning of anthropogenic activities and climatic changes, providing scientific bases for synthetically evaluating environment changing trend and environmental effect, formulating controlling strategies and management models.

Plant leaf traits are associated with fundamental behavior and function of plant individual, community, and ecosystem. It can reflect plant survival strategy response to different environmental factors. We synthesize the research advance on leaf traits at different ecology scale, such as individual scale, functional group scale, community scale and global scale. Individual scale focuses on the leaf traits response to environment factor or muti-factors, such as temperature, soil moisture and soil nutrient. The differences of leaf traits occur among different functional groups, it probably is an outcome of environment selection, and the selective pressure is relatively weak within each group. As the community structure changes, the leaf traits average value of the community and the leaf traits of the dominate species also changes. Studies at large-scale reveal that high level of trait disparity is observed within community, compared with the variation among sites that may reflect large-scale climatic factors. Although ecologist quantitatively compares some variations on different scales, but these differences are implicit, and they are rarely explicitly stated. Further studies should focus on how plant leaf traits response to muti-enviroment factors? What's the plant leaf traits functional behavior in the community assembly processes? Are there biogeographically patterns of global leaf traits? Ecological relationships also differ among scales. Plant trait correlations could also be scale-dependent, in other words, how scaling leaf traits data from individual to community or global scale should be explicitly stated.

The paper reviewed the research and exploitation about plant endophtic bacteria, including its classification method, biodiversity, distribution, biological function, exploitation and application. The future of exploitation and application of plant endophtic bacteria resources was prospected, so as to providing theory basis for further research and utilization.

The effect on climate and environment of aerosol is a hot issue in field of atmospheric science. The article briefly introduced the international research dynamic and main results and the development status in China during the past 20 years; and discussed the main research field in future; the research method and result on atmospheric aerosol in northwest China as well as the aerosol's climatic and environmental effect were highlighted in this paper.

Soil organic carbon pool has a direct effect on global carbon balance, so research of soil organic carbon pool is the key of researches on the global carbon cycling. Understanding of soil organic carbon dynamics and its mechanisms under impact of human activities will not only reduce the uncertainty of predicting climate change in the future, but also provide theoretical references for technology selection and incentive policy making for soil carbon sequestration. This paper reviewed the domestic and overseas study advances on effects of human activities on soil organic carbon pool, especially the effects of land use changes, tillage methods and management practices on soil organic carbon pool. Lastly, some suggestions were presented to mitigate anthropogenic emissions of greenhouse gases, promote carbon sequestration, and maintain sustainable development of agriculture.

The responses of net photosynthetic rate(Pn), chlorophyII fluorescence parameters and trehalose content of Reaumuria soongorica Maxim, Salsola passerina Bge, Caragana korshinskii Kom and Artemisia ordosica Krasch, to drought stress were studied. The results were as follows: Relative water content of leaves, net photosynthetic rate, maximal photochemical efficiency of PSⅡ in the dark(Fv/Fm), apparent quantum transport rate(ETR), photochemical quenching(qP) decreased, trehalose content and non photochemical quenching(qN) increased under drought stress. The effects of drought stress on those variables among the four desert plants were obviously different, and Caragana korshinskii Kom was the highest tolerance and resistant to drought stress among the four plants studied. Correlation between soil water content, trehalose content, net photosynthetic rate and chlorophyII fluorescence parameters was analyzed. The results indicated that soil water content remarkably affected photosynthesis and trehalose content of four desert plants.

This article takes the Danxia landform and color hill that situate at Qilian piedmont in Zhangye city of Gansu province as study object and analyzes their strata, configuration, landscape, ancient geographical environment and external forming factors. The Danxia landform in this region can be classified into three types of landscape: Window and palace pattern, Pillar pattern and Laneway pattern. Viewed from aspects of representativeness, aesthetics, scientific research and admiration, their values on research, teaching and touring have been evaluated. The Danxia landforms in Zhangye City not only have grace as southern landscape, but also have majesty as northern landscape; the color hills are florid and grand. These two peculiar landscapes bring out the best in each other and become the unique geologic relic in our country, which possess high admiring and scientific research value. This place is a best place fort tourism, drawing, education and research.

The significance of the N∶P stoichiometry in terrestrial and aquatic ecosystems was determined on the basis of the literatures in domestic and abroad. In the terrestrial ecosystems, there is an inverse relationship between soil N∶P ratio and the nitrogen-fixing amount of symbiotic associations and non-symbiotic associations; soil N∶P ratio can affect vegetation dynamics as well as the biodiversity and productivity of the ecosystems. Especially, the phosphorus amount would restrict the productivity and richness of threatened species. Plant N∶P ratio can reflect the nutrient conditions and the relative availability of nitrogen and phosphorus, so it is an important index for vegetation restoration and threaten species protection. In the aquatic ecosystems, there is also an inverse relationship between water N∶P ratio and the nitrogen-fixing amount of aquatic organisms, also the water N∶P ratio can influence the growth of aquatic organisms and the composition of aquatic community.

Based on data of monthly temperature and precipitation from 5 representative meteorological stations in northwestern Shanxi province during the period of 1957—2006, the series of average temperature and precipitation of the whole year, winter half year and summer half year were established, and the changing features of temperature and precipitation and their impact on land desertification were analyzed. Results showed that climate tends to become warmer and arider in the area. The linear trend rates of average temperature for the whole year, winter half year and summer half year were 0.202 ℃/(10a), 0.2 ℃/(10a) and 0.132 ℃/(10a), respectively; It had gradual and periodical features for average temperature in the summer half year. The linear trend rates of precipitation for the whole year, winter half year and summer half year were -16.68 mm/(10a), 0.404 mm/(10a) and -14.95 mm/(10a), respectively. The reduction of annual precipitation resulted mainly from reduction of precipitation in summer; precipitation in winter increased in comparison with that in summer. The condition of precipitation reduces in summer and increases in winter can certainly slow the process of land desertification.

Shenfu-Dongsheng coal mining area is located on northern Loess Plateau,and is in the centre area of rainstorm of the middle reaches of the Yellow River.Soil erosion is very serious.Soil erosion intensity is mainly affected by rainstorm type,lasting time and intensity.In the region,there are not meteorological and hydrologic observation stations in some middle and small drainages,so to design and budget the rainstorm process is very important for us to calculate runoff process and erosion value of these drainages.For above-mentioned purpose,in this paper,according to the principle of hydrology and calculation formula( H _tp= I× t= A+ Bln N/ t ⁿ× t),and on the base of characteristics of torrential rain in Shenfu-Dongsheng coal mining area,as well as on hydrologic count handbooks of Dongsheng city and Yuling prefecture( n=0.67~0.83, A=20~30, B=20~35;Average value: n=0.75, A=25, B=28),torrential values were calculated with various rainfall intensity and different reappear cycle of torrential rain.On the basis of the biggest torrential rain records of lasting 1,6,12,24 hours,the types of torrential rain process occurring once time yearly were conceptualized in various lasting rain,adopting the ways of average arithmetic,slide choose and correspondence main peak.According to about 10 years rainfall automation record digital data of ecological experiment base of Luidaoguo drainage in Shenmu county the designed rainstorm process curve were tested and verified.The results showed that lasting 1 and 6 hours rainstorm is the best fit with rate of above 90%,12 hours rainstorm is better fit with rate of about 85%,24 hours rainstorm is poor fit due to various rainfall intensity on curve of rainfall automation record.But the general trend is good fit.In this calculation way,the torrential rain process in the small drainage without observation station of meteorology and hydrology can be inferred.The inferred torrential rain process curve will be the foundation to calculate runoff formation and convergence.

Reaumuria trigyna Maxim, a rare remnant derived from the Mediterranean Sea, is peculiarly endemic to Alax-Erdos Desert of China. The structure of salt gland and secretion characteristics of salt excretion from Reaumuria trigyna, and their relationship with salt distribution in the soil of field environment were studied. The halophyte Reaumuria trigyna, with salt-gland-ferous multi-cells, can secrete salt. The ion composition in Reaumuria trigyna plant and its secretion is consistent to that in habitat soil, all have ions of Na⁺, K+, Ca²⁺, Mg²⁺, SO^2-₄ and Cl , but different in ion content. Cations as Na+ or Na+ and Ca²⁺, and anions as Cl or SO^2-₄ are dominant in soil solutions; K⁺ is dominant in the roots, stems and leaves of plant, the contents of the six ions follow the order: roots<stems<leaves. In the secretion of Reaumuria trigyna the content of Na+ and Cl^- is the highest, followed by SO^2-₄. The excreting rate of salt gland was higher in the morning than that in the afternoon and higher in daytime than that at night. Such high selectivity of salt gland secreting salt is the self-adjustment mechanism of Reaumuria trigyna to adapt to the wild habitat, maintaining the proper salt and nutrient contents.

The karst areas of south China are vulnerable ecological regions, where rocky desertification is widely developed. The article proposed a new concept of rocky desertification, realized that rocky desertification is the processes of land degradation with similar rocky desertification landscape which formed by degeneration of vegetation, erosion of soil, loss of surface water and the outcropping of bedrock under moist and semi-moist climatic environment and under the factors of human activity and(or) changes of climate etc. There are two causes of rocky desertification in karst areas of south China, the natural and the human driving factors. From geologic time to historical periods there experienced natural processes of rocky desertification. From historical periods to modern age there added human driving processes and human beings activity fasten the development of rocky desertification. The initial and middle periods of Qing dynasty are important transition time, and from then on the human driving factors become the main influential factor. Rocky desertification process is the surface ecological processes including the processes of vegetation degeneration, soil erosion, water loss, bedrock dissolution and erosion and land biological productivity degeneration; its essence is the processes of land degradation forming similar rocky desertification landscape.

Aeolian desertification and climate change are two hotspots people are facing today. Much attention is paid on the feedback loops between them two. Deterioration of climate conditions, continuous desiccation for instance, can lead to aeolian desertification, and aeolian desertification can give a negative reaction to climate change through biogeophysical feedback, releasing more dust aerosol and increasing greenhouse gases concentration. In local areas, this kind of interaction may come into being positive loops, allowing the disturbance to be amplified. Based on the analysis of a large amount of literatures, the authors reviewed the existing research systematically through analyzing the feedback loops between climate change and biogeophysical feedback mechanism, dust aerosol and greenhouse gases. There are four bottlenecks in the research: ①the scale that biogeophysical feedback mechanism takes effect; ②causality between dust aerosol and precipitation; ③disagreement of the data used and the differences of their characters; ④methods to distinguish the human-induced and natural factors that lead to aeolian desertification. The authors claim that scientists should study the interactions between aeolian desertification and climate change systematically in earth system science terms, and pay more attention on both model research and field observation.

Using the data collected at the Sand Drift Observation Station of Chinese Academy of Sciences in 2005, the monthly and seasonal change of rose diagram of wind speed and direction, wind velocity,temperature and humidity profiles near the surface layer are analyzed in detail. These characteristics in the Tengger Desert are made public accordingly. The monthly change of temperature and humidity profiles is also very obvious: the value of temperature in July is greatest, and least in Jan., and the humidity in Oct. is greatest, and least in April, the humidity in the Spring is least in one year.

The remote sensing images in 1980s, 1990s and 2000s were interpreted to disclose the desertification process of Mu Us Sandland, and to discuss its driving mechanism. The degree of desertification in Mu Us Sandland decreased in the past 20 years, and the cover of vegetation increased correspondingly. Meteorology factor and anthropogenic factor account for these change in Mu Us Sandland. Increased temperature is the key factor in the increase of vegetation cover, and the effect of anthropogenic factor is manifested by the great increase of farmland and woodland.

The land use and land coverage change(LUCC) of middle reaches in Heihe river basin was studied based on the Landsat ETM images taken in 2000 and Landsat TM images taken in 2005. In combination with the socio-economic statistics and the meteorological observation data, the LUCC pattern, the land use change trend and its driving forces of the study region in the five years were analyzed. In general, the eco-environment of the middle reaches in Heihe river basin had trend of deterioration. In details, from 2000 to 2005, the arable land and the dwelled land had been respectively enlarged by 6.95％ and 9.78％, whereas grassland and forest relatively decreased, especially the water area and the wilderness area had been respectively decreased by 1.70% and 0.88%. Both the human activities and the natural changes had result in the LUCC of this region. But on the premise of the human factor playing the important role, the eco-environment of this region has the latent crisis of further deterioration.

expalnt; Reaumuria soongorica; callus

Based on a review of the last 30 years' research results on the forming mechanism of coastal dunes at home and abroad, this paper made a preliminary conclusion as follows: The coastal dunes developed at coastal zones of all latitudes, but the coastal zones with abundant sand, suitable wind and adequate sand gathering were the most appropriate, and the coastal dunes were mainly distributed at the upper reaches of storm waves and the maximum position of astronomical tide. The coastal dunes formed and developed during the exchange process of energy and material between land surface and beach-dune dynamic system. The development of coastal dunes was mainly affected by sand source, wave energy, wind speed and wind-driven length, and it was also influenced by other factors, such as beach slope, grain size of the sediments, adhesive force, vegetation coverage and atmosphere density, etc. Under the influence of various dynamic-geomorphology system and natural environment, the shape and size of coastal dunes presented different developing patterns. According to the review of research status, this paper put forward some suggestions to improve the research on the coastal dunes in China.

Based on the hour-to-hour surface observational data and day-to-day dust storm data in midwestern Inner Mongolia from Mar. to May in 2005 and 2006, the surface sensitive heating flux and surface potential temperature were calculated and the relationship between them and dust storm was analyzed. The results show that a net surface heating appears at the midwestern part of Inner Mongolia in Spring; The surface sensitive heating flux is smaller in dust storm occurring years. Before dust storm occurrence the surface sensitive heating flux in high plain areas and desert areas reached the maximum while that in hill and plain areas began to decrease. The accumulative surface sensitive heating flux in high plain areas and hill areas is larger than that in desert areas. But the influence of surface sensitive heating flux on the dust storm in desert areas and high plain areas is more efficient than that in hill areas.

The spatial and temporal distribution characteristics of MPM in semiarid area of China are analyzed based on observations of mass concentration of PM10(MPM) and relevant meteorological elements at six national climate observation stations in Inner Mongolia of China in 2005. The results show that the maximum MPM of each observation stations all occurred in spring(April). The diurnal variation of MPM show an unimodal curve during the non-dusty days, and the appearing time of the maximum value is postponed from spring to winter. The maximum value of MPM is a main factor reflecting the intensity of dust weather, and the correlation coefficient between the climate condition index (IPM) and MPM is greater than 0.5.

The architecture parameters of Reaumuria soongorica root system at different habitats in Gansu Province, China were analyzed to examine its ecological adaptability to arid environment. Results show that: (1) Topological indices of R. soongorica root system are small at all the habitats, and root branching pattern tends to be dichotomous. The topological indices of R. soongorica root system gradually increase in the Minqin windblown sand region and the Zhangye gobi region in Hexi Corridor, which indicates that drought makes root branching pattern tend to be herringbone-like. (2) Fractal dimension values of R. soongorica root system all are small in the Minqin windblown sand region and the Zhangye gobi region in Hexi Corridor, and the values are 1.1778 and 1.1169, respectively, which indicates that the fractal characteristics are not obvious in these areas. While the fractal dimension values are relative large in Jiuzhoutai semi-arid hilly and gully region of the Loess Plateau, which indicates that the R. soongorica root system has better fractal characteristics in this region than in the other regions. (3) Total branching ratios of the R. soongorica root system in arid region of Hexi Corridor are smaller than that in the Jiuzhoutai semi-arid hilly and gully region of the Loess Plateau. It shows that the root branching ability in the semi-arid region is stronger, and it decreases at some degree with drought increase. (4) The root link lengths of R. soongorica root system are long at all the habitats, but there are significant differences between the different habitats. The root link length at the Minqin windblown sand region is the longest. It is concluded that R. soongorica adapts to arid environment by decreasing  root branching, decreasing root overlap and increasing the root link length, which makes its root branching pattern tend to be herringbone-like to reduce compete degree in root internal environment for nutrients and to enhance root absorption rate to nutrients, and ensure the effective nutrition space, thus it can absorb enough water and nutrients in resource-poor settings to ensure its normal physiological requirements.

At present, the source region in Qinghai of the three big rivers of China, with the most seriously ecological environment of desertification, is the most important one in ecological environment construction of our country. Therefore, researches on the sandy desertification in this region are of great significance. In present years, a lot of achievements on desertification and its control have been got. This paper reviewed the research progress on desertification of Qinghai plateau from the end of 1950s to the early 21 century, including scientific surveying, desert distribution, basic desertification characteristics, sand dune types and their formation and evolvement, law of blown sand movement, filed observation and desertification monitoring, and experiment of sand prevention and control, etc. Researches related to the five desertified land distributing areas: Qaidam basin, Gonghe basin, Qinghai lake basin, source region of Huanghe river and source region of Changjiang river. Accordingly, the problems existed in the above research fields and the contents need further study were put forward in the paper.

Dry valleys are noticeable and unique geological-ecological phenomena in the Qinghai-Tibet Plateau periphery as well as in the \!Three Parallel Rivers\" region, which were formed by a series of synthetic impacts, including tectonics-geomorphology-palaeoecology effect, air circulation-monsoon-narrow pipe effect, topographical wave-precipitation-local circulation-fohn effect and vegetation-human activity-land use-disturbing effect. In the early Tertiary, the \!Three Parallel Rivers\" region was a component of the broad dry climate zone in China. With the uplifting of the Qinghai-Tibet Plateau and the evolution of the southwest monsoon, the climate and vegetation in the region gradually changed into the subtropical climate. Since the end of Pliocene, the longitudinal Range-Gorge landforms formed. Great rivers eroded back to the source, and valleys incised deeply. At the foot of the deep-incised valleys, the arid or semi-arid ecological landscapes that are equal to their latitude formed, which in the sense of palaeoecology has realized the reversion. In winter, influenced by the south branch of the Westerly the climate in the region is dry. In summer, the region is controlled by the southwest monsoon; in spite of much vapor the region still has formed four areas with less precipitation due to the special landforms structure. Part of airstreams flow northward quickly without any obstruction along the narrow and straight valley. With the increasing of altitude topographical precipitation formed. The wavy distribution curve of precipitation formed on the longitudinal-arranged underlying range-gorge landforms. At leeside of range, dry valley formed due to fohn effect. On the original background of fragile ecosystem, the social economy development strengthened the intensity of the land use, reduced the vegetation and aggravated the loss of water and soil erosion, which made the dry valley develop to further dry. These proved that the dry valley was the result of coupling effect among land, air, water, biome and human.

In this paper, a study on land surface temperature(LST) and land surface emissivity estimation over the desert and oasis area in Heihe river basin in the summer of 2003 is conducted by using Advanced Spaceborne Thermal Emission Reflectance Radiometer(ASTER) data, based on Temperature/Emissivity Separation method(TES), Alpha Derived Emissivity method(ADE) and Emissivity Parameterization method from vegetation coverage (Pv). The analysis suggests that the estimations of the three methods are relatively close and their retrieval results are consistent with the ground observations. According to the retrieved results, the water body surface temperature mainly ranges from 19.0℃ to 21.0℃ and the cropland surface temperature mainly ranges from 27.0℃ to 29.0℃, and the desert and Gobi surface temperatures range from 40.0℃ to 60.0℃. It is found that the Pv parameterization method provides lower LST over oasis region and the ADE method provides higher LST, whereas the result is inverse over desert and Gobi region. In these two cases, the result provided by the TES method is between the one estimated by the Pv parameterization method and the ADE method. It is also found that LST appears relatively high spatial variation both over the oasis and the desert regions. A fitted formula based on emissivity spectra library is established in order to get the broad channel LSE. Using this formula, a maximal 8.0 W·m-2 error was caused in calculating long-wave radiation at a large environmental LST range.

Based on the definition of desertification from the United Nations Convention to Combat Desertification, the potential extent of desertification in China was revised by employing Thornthweites and Penmans formulae to calculate humidity index using the records of 671 meteorological stations from 1950 to 1990, and the biogeographical features of the climate types were clarified. The calculated result was adjusted according to the climate division and vegetation division of China and the characteristics of desertification development of China. The results show that: ①The potential extent of desertification and the criteria for climate division defined by the United Nations Convention to Combat Desertification are not applicable to all cases in China. ②Desertification occurs in extremely arid, arid, semi-arid and sub-humid areas in China. The extremely arid area corresponds to extremely arid desert, the arid area corresponds to desert, steppe desert and desert steppe, the semi-arid area corresponds to steppe and the sub-humid area corresponds to the drier part of meadow steppe. ③The revised potential extent of desertification in China is about 4524089.1 km2, accounts for about 47.1% of the total terrestrial area of China, in which, sub-humid, semi-arid, arid and extremely arid areas account for 12.6%, 28.8%, 34.4% and 24.2% respectively. The potential extent of desertification increased 1207056.9 km2 compared to the former results after revision, sub-humid area decreased, semi-arid, arid and extremely arid areas increased.

C. ewersmanniana is a kind of high-quality herbage in arid region, and the construction species of wind-sheltering and sand-fixing vegetation. In this paper, two representative samples of 200m 200m were set in south of Gurbantunggut desert. Ripley's K(d) function was used to determine the spatial pattern of population regeneration of C. ewersmanniana and its relationship with the three main shrub populations（H. ammodendron, R. soongorica, S. kaschgaricum）. In both samples, the spatial pattern of population recruitment was influenced greatly by the distribution of adult C. ewersmanniana. Adult and middle-aged C. ewersmanniana exhibited positive correlation with young C. ewersmanniana. C. ewersmanniana had positive correlation with S. kaschgaricum, but had negative correlation with H. ammodendron. Its correlation with R. soongorica was opposite in the two samples. We concluded that the population recruitment of C. ewersmanniana depended severely on adult plants. The spatial autocorrelation of its population recruitment was obvious within 30 m.This spatial autocorrelation was affected greatly by the environment and had weak ability to expand. In addition, the growth of four shrubs was determined by niche of each species, and was influenced greatly by water and other environmental factors. In the end, suggestion for ecological restoration of shrubs including C. ewersmanniana was raised.

Synthesis dominance rate (SDR), Richness index (R), Shannon-Wiener index (H), Simpson index (D), Pielou index (JSW), Whittaker index (βwc), Cody index (βc), Dispersion index (C), Negative binomial parameter (K), Mean crowding intensity (m*), Clumping index (I), Patchiness index (PI), Cassie index (GI) and Green index (CA) are used to analyze the species diversity and dominance population distribution pattern based on field surveying data from 30 plots along 10 sections at oasis-desert ecotone in the lower reaches of the Tarim River. The results showed that the structure and composition of these communities were simple, the dominance populations were Populus euphratica, Tamarix chinensis Lour., Lycium ruthenicum, Halostachys caspic, Karelinia caspica, Phragmites communis, Alhagi sparsifolia, Glycyrrhiza inflate, Poacynum hendersonii, and they distributed in aggregative state in responding to groundwater depth. The α-diversity indices of these communities were low, and species diversity showed gradient change. The richness index followed the order: oasis>ecotone>desert due to water resource difference in microenvironment. From ecotone to desert, the community structure changed from tree-shrub-herbage to shrub-herbage to single shrub to shrub-herbage, and to tree-shrub-herbage due to change of groundwater depth. Suggested by Whittaker index and Cody index, the β-diversity indices of these communities changed with groundwater depth gradient, showing the ecotone was the boundary between oasis species and desert species distribution. Therefore, the groundwater depth was the decision factor for species diversity and distribution pattern of dominance population at oasis-desert ecotone in the lower reaches of the Tarim River.

Soil is an important part of desert ecosystem. The management and restoration of desertified lands is a focus for all along time. The soil in Shapotou desert region has developed remarkably gone with the evolution of the artificial sand-binding vegetation for fifty years. The longer the period of dune stabilization, the greater the thickness of microbiotic crusts and subsoil, and the proportion of silt and clay increased significantly, and soil bulk density reduced, meanwhile the content of soil organic matter and N, P, K increased similarly, so the soil has developed from aeolian sand soil to Calcic-Orthic aridisols. The paper discussed the effect of dust and microbiotic soil crust and microbes on soil-forming process and analyzed the relation between soil-forming and evolution of artificial sand-binding vegetation and in the end advanced important future study fields.

The data of aeolian desertification lands status in different periods have been extracted through visual interpretation method based on Landsat MSS, TM/ETM images in 1975, 1990, 2000, 2005 and 2010 over the northern China areas. Hence, we analyzed the changing trend of aeolian desertification in northern China during the last 35 years, and have got some results as follows: (1) The area of aeolian desertification lands in northern China in 2010 are 37.59×104 km2, among which the slight grade accounts for 33.80%, the moderate grade for 22.84%, the severe grade for 22.16%, and the extremely severe grade for 21.21%. (2) From 1975 to 1990, the net increase area of land desertification area of northern China was 33 838.32 km2 with an increasing rate of 2 255.89 km2·a-1; the net area of land desertification lands being intensified was 33 279.28 km2; thus the net developing rate was 4 474.51 km2·a-1. From 1990 to 2000, the net increasing rate of land desertification area was 3 441.49 km2·a-1 and net developing rate was 5 370.06 km2·a-1. Since 2000, there was a recovering trend of land desertification lands in northern China. From 2000 to 2005, the net area decreasing rate was 1 635.28 km2·a-1, and the net reversion rate was 10 071.02 km2·a-1. From 2005 to 2010, the net area decreasing rate was 1 114.35 km2·a-1, and the net reversion rate was 7 552.21 km2·a-1. Changes of land desertification mainly occurred in the agro-pasture ecotone of semi-arid area.

C4 plants of Alxa desert are principally manifested by Chenopodiaceae, Gramineae, and the life forms are most biennial and annual grasses, accounting for more than 70%; xerophytic and mesophytic C4 plants make up 48.89%, and whose floristic area-types are mainly from Cosmopolitan, Asia media and Tethys. Distribution of C4 plants presents different laws in Alxa region: distribution of C4 plants positively relates to temperature and negatively relates to precipitation along altitudinal zonality; it positively relates to precipitation and less relates to temperature along horizontal zone, especially, presence of C4 plants are limited in extremely high temperature and arid conditions (mainly in gobi desert area of Ejin Banner). The results can some explain the status of the water utilization efficiency of C4 plants in Alxa and its relationship with spatial precipitation distribution.

Sand-dust storm is an intense wind erosion process and it simultaneously exacerbates the land desertification process. The ecological environmental effect and climatic effect of dust aerosol in sand-dust storm have become the focus of attention of the international community of science. In this paper, the dust aerosol number concentration and its transmission characters during spring sand-dust storms were analyzed based on the observation data in Hunshandake sand-land. It was calculated that the dust-emitting wind speed on the sand-land is 5.9 m·s^-1 at 10 m high, and the transmission distance of dust particles in sand-dust storm weather condition is about 7.6 10⁴~7.6×10⁵ km.

Water replenishment, vegetation growth and wind-sand movement are the main factors that contribute to the change of vegetation coverage on sandy grassland in arid and semi-arid region. The conceptual and mathematical models of vegetation coverage are set up based on the researches on these three factors. The main models are grid water flow model, runoff model, ground water supply model, potential land productivity model. The model, combined with GIS technology, can show the spatial distribution characters of soil water supply, sand area and vegetation coverage change on sandy grassland in arid region.

Monitoring dune migration and morphologic change plays an important part of aeolian research. However, traditional measurement methods have great difficulties in the monitoring of a wide range of aeolian geometrodynamic processes because of the technical limiting and harsh environment, which had restricted the regional aeolian geomorphology research progress in a long run. The emergence of Co-registration of Optically Sensed Images and Correlation provides a good solution for the study of monitoring regional dune migration. In this paper, we discussed the advantages and some key issues of COSI-Corr technology during the dune migration monitoring. Its measurement precision and accuracy were assessed using the drone field ground-control measurement results. It revealed that: The higher measurement accuracy of the COSI-Corr occurred at the bottom edge of the leeward slope of the dune, reaching the 1/30 pix of the image pixel. There is a liner function between the measurement accuracy of COSI-Corr and the basal area of dune, the larger the basal area of dune, the higher the measuring error of COSI-Corr. The abnormal values at the ridge of sand dunes may be caused by the light reflecting which enhanced the noise during the data processing. Even though, COSI-Corr is still in its preliminary usage in aeolian geomorphology, it really improved the efficiency of the regional dune morphodynamic monitoring, and especially provides a possibility for the studying of dune migration and evolution process in those rural area where ground control measurement cannot carry out. Some specific issues also require us to constantly test and improve its measuring precision in future practice using.