The successional characteristics of vegetation on old-field in Bashang region of Hebei Province were analysed by means of cluster and ordination methods and inferred their temporal sequence from spatial sequence.The results showed that there are 6 associations and 3 sub-associations on the old-field;many factors rather than the single time factor affected the vegetation development;the variation in the number of plant species has a markedly fluctuation;the principle Initial Floristic Composition is not suuitable to the succession of the vegetation in the region;the transformation and utilization of vegetation on old-field should be proceeded after the farmland has been abandoned from 2-6 years.

Sand dike plays an important role in the sand-control system. In this paper, wind tunnel experiments were conducted to simulate the protective effect of a series of sand dike models with different shapes, dip angles and heights. Results showed that:①Sand dikes affected the flow characteristics significantly. Five typical sub-areas in flow field around sand dike could be identified based on their flow characteristics: low-speed area before windward slope toe, resistance-confronting lifting area on the windward flank, mass flow accelerating area above the top of the dike, flow-sinking decelerating area of leeward slope and dissipating recovering area. The low-speed area before the dike and the mass flow accelerating area above the top of the dike could reduce wind speed and prevent sand transport. ②Considering the size of low-speed area before the dike body, the trapezoidal sand dike was better than the triangular one, but from the aspect of the effective shelter distance, the conclusion was just the opposite. ③The protective effect of the triangular sand dike reduced with the growth of the wind speed. The effective shelter distance of the triangular dike increased with the growth of the dip angle, while the low-speed area before the dike body decreased with the growth of the dip angle. ④The effective shelter distance of the triangular sand dike with a 40° dip angle was always the largest under four different wind velocities. ⑤The effective shelter distance on the lee flank of the sand dike was correlated with the height of the sand dike.

Through investigating and analyzing the effects of overgrazing on the community type, coverage, biomass of pasture vegetation and characteristics of soil, it is showed that overgrazing leads to some very serious environmental problems, which in return exerts adverse effects on animal husbandry. Overgrazing causes grassland deterioration and soil erosion, especially in spring, the damage of overgrazing is the most serious. The changeability and easy to deterioration of pasture ecosystem determine that grazing leads to a series of problems, even causes some serious problems such as salinization or alkalinization, hungriness and drying in deep soil. This paper points out that content of saline-alkaline in soil, vegetation coverage, moisture in deep soil, humidity of subaerial air and its content of atomy should be monitored, which are the bases to establish some rational developmental plans and supervisory measures, it is very necessary for ecological and environmental improvement and long-range development of animal husbandry.

With the desertification monitoring data in 1999, 2004 and 2009 in Ningxia, we analyzed the evolution of the desertification and its influencing factors in Ningxia. The area of desertification land decreased from 3.2074×106 hm2 in 1999 to 2.8988×106 hm2 in 2009 and reversed obviously during 1999-2009. The area of wind-erosion desertification land decreased from 1.5191×106 hm2 in 1999 to 1.3458×106 hm2 in 2009, and the area of water-erosion desertification land reduced from 1.6572×106 hm2 in 1999 to 1.4897×106 hm2 in 2009, while the area of saline desertification land increased from 3.11×104 hm2 in 1999 to 6.33×104 hm2 in 2009. The area of severe and moderate desertification land decreased obviously from 1.0098×106 hm2 and 1.4270×106 hm2 respectively in 1999 to 2.757×105 hm2 and 1.3838×106 hm2 respectively in 2009, while the area of slight desertification land increased obviously from 7.10×105 hm2 in 1999 to 1.1708×106 hm2 in 2009, so desertification degree weakened obviously. In desertification regions, vegetation cover was improved further and vegetation coverage increased. Among the climate and human factors affecting the evolution trend of desertification, the reversion of desertification was influenced decisively by national policy, comprehensive development and utilization project, establishing and perfecting of various ecological protection measurement and mechanism, public participating in combating desertification, and so on. The negative effect produced by climate change was offset by the positive effect of these human factors. However, the reversion of desertification was slowed down to some extent by the population pressure, the human unreasonable activities in historical period, the inefficient utilization of water resources, and so on. These human factors are the unfavorable factors in combating desertification, which needed to be overcome in the prevention and control of desertification in Ningxia in the future.

Bryophytes usually are thought to be valueless and neglected by the public due to the small size.It has been overviewed in the paper that the ecological functions of bryophytes to ecosystems,including CO ₂ fixation,water and nutrients cycling and reserve,and forest renewal.The significant role of bryophytes in restoration and revegetation of degraded ecosystems is focused on.Some preliminary suggestions are given for further study on bryophyte biodiversity and ecology in desertification-prone areas.

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.

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 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 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.

As a very serious problem to China, desertification distributes widely, occupies a very large area, and earns a high, serious level of hazard. During the past decades, a certain amount of achievements had been obtained in desertification control, but the desertified land was still restored in some local regions, and meanwhile, desertification has been expanding rapidly as a whole and the trend seems worsening. Now desertification control is facing severe situations in China. Drought is the basic background condition for development of desertification, while unreasonable human activities resulting from fast increasing of population and backward mode of production and management, such as over-reclamation, over-grazing, unrestricted cutting, squandered water resources and indiscriminate mining, are the main causes of rapid wide-spreading of present desertification in China. Desertified land should be tackled in a comprehensive way that combines prevention, amelioration and exploitation. And what's more, in order to speed up desertification control, the government should formulate a preferential policy for desertification areas.

Desert pavement is a surface layer with closely packed gravel that insets in a thin fine-grained vesicular soil horizon， and is important for the stability of the desert ecosystem. Based on the data of the field investigation and situ soil water infiltration in the northern desert of Linze Oasis in the Hexi Corridor， the characteristics of desert pavement and its influence on water infiltration are analyzed in this study. The results show that： （1） desert pavement is 0.50 cm thick with 4.61 mm size gravel， and its surface gravel coverage average 52.7%. （2） Compared to the soil profile below the desert clast， the mass water content of pavement is lower and 0.3%， but the gravel content of pavement is higher and 41.64%， with the declining trend from hill to oasis. Except for Sample 2， the bulk density in upper soil profile （0-5 cm） with pavement clast is higher than it in lower soil profile （5-50 cm）. （3） desert pavement can constrain the water infiltration， the steady-state infiltration increases from 2.35 mm·min^-1 to 3.69 mm·min^-1 when the pavement clast removed. （4） Steady-state infiltration of desert pavement has a significantly negative correlation with thickness and gravel content of pavement clast， a significantly positive correlation with gravel coverage and mass water content of pavement clast， and a positive correlation with grave size of pavement clast. This study is helpful to understand the hydrologic effect of desert pavement.

Soil seed bank is a potential vegetation, which has an important impact on the stability of regional ecosystems and the structure and function of future vegetation. In this study, four ecological regions, Naiman, Shapotou, Minqin and Dunhuang, were selected to study the effects of sand dune location, sand type, vegetation, and soil depth on Agriophyllum. squarrosum soil seed bank. The results of this study indicated that the soil seed bank density of mobile sand dune in Minqin is the highest, with an average density of 51 grain /m², which are 2 times, 4 times, and 3 times that of Naiman, Shapotou, and Dunhuang; There are significant differences in the A. squarrosum seed bank in different parts of the mobile sand dunes; The seed bank of A. squarrosum mainly distributed in the middle of the windward slope and the foot of the leeward slope of the sand dunes, and scattered at the top of the dune and the leeward slope. The seed bank at the top of the dune only accounts for 28% of the middle windward slope, and the middle leeward slope only accounts for 30% of the leeward slope foot. The soil seed bank of A. squarrosum was mainly exists in the soil layer above 60 cm, the seed of 0-20 cm near the surface accounts for above 50% of the total seed quantity. With the dune fixation process, the density of soil seed bank is decreasing. The density of soil seed in mobile sand can reach 401 grain·m^-2, and it will decrease or even disappear completely in fixed sand; The total density of the soil seed bank of 0-15 cm in the community formed by A. squarrosum and C. arborescens was 800 grain·m^-2, which was twice that of A. squarrosum, 2 times of N. tangutorum + A. squarrosum, 6 times of H. ammodendron + A. squarrosum community; There was a significant linear relationship between A. squarrosum soil seed bank and the above-ground population. The soil seed density increased with the increase of the above-ground population density. Obviously, the soil seed bank and its distribution are important guarantees for A. squarrosum to adapt to severe wind and sand environment, and an important guarantee for self-reproduction，it was affected by various factors such as regional environment, above-ground changes, land type, soil depth, etc. In order to protect the desertified land, it is necessary to prohibit the harvesting of the resources on the sand land to supplement the soil seed bank of sand land.

The spatial and temporal distribution of TSP and its inorganic ion concentration in the Tarim Basin were analyzed based on observation data of total suspended particle (TSP)  in four typical observation stations in 2009, and analysis of water-soluble inorganic ions in TSP. Some results are obtained as follows: (1) The variation trends of monthly average TSP concentration in the four regions are almost the same, with peak values in April and May and with valley values in November and December. Its seasonal variation shows the highest value in spring, followed by summer, autumn, and winter in order. (2) The annual average concentration of total water-soluble inorganic ions in TSP in these four regions follows an order of that in Tazhong>in Tikanlik>in Minfeng>in Kashgar. In detail, the SO2-4 concentrations are 58%, 50%, 54% and 51%; the Ca2+ concentrations are 13%, 16%, 16% and 11%; the Na+ concentrations are 12%, 13%, 10% and 12%; and the Cl- concentrations are 12%, 16%, 11% and 22% of total ion concentration, respectively. Therefore, sulfate, calcium, sodium and chloride ions are the main inorganic components of TSP in the Tarim Basin; (3) The correlation coefficients between anions and cations in Tikanlik, Minfeng, Kashgar and Tazhong are 0.99, 0.99, 0.25 and 0.91, respectively; the average concentrations of anions are 2.57, 2.12, 2.15 and 3.02 times of cations, indicating that anions and cations are unbalanced in the observation stations. (4) The SO2-4/NO-3 ratios in the observation stations are much larger than the SO2-4/NO-3 ratio of coal-fired emission, so the impact of fixed emission sources is far severe than the mobile emission sources in the study regions.

In order to analyze the spatial change of species in different positions of dunes and the stability of Haloxyon persicum population, χ2 interspecific association test, association coefficient, and Spearman rank correlation coefficient were used to determine the interspecific associations in the Gurbantunggut Desert based on the 2×2 contingency table. The results are obtained as follows: 1) Among the 435 species pairs from both shrub and herb layers, few show significant χ2 association（P<0.05）: 12 pairs show highly significant association (P<0.01), 15 pairs show significant（P<0.05）, and the other 398 pairs show non-significant associations. 2) According to interspecific association and species correlation, the 30 dominant species were clustered into five ecological groups: 3 are from shrub layer, they are Group Ⅰ—Haloxyon persicum+Calligonum leucocladum, Group Ⅱ—Ephedra diotachya, and Group Ⅲ—Seriphidium terraealbae; 2 from herb layer, Group Ⅰ—Carex physodes+Erodium oxyrrhynchm+Alyssum linifolium+Ceratocarpus arenarius. Group Ⅱ—Horaninowia ulicina+Senecio subdentatus+Eremopyrum orientale. The species distribution characters of these ecological groups were also analyzed in this paper.

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.

Surface roughness length is an important parameter of atmospheric boundary layer.There have been major advances in the understanding of this length recently.In this review,attention is directed towards three important aspects of surface roughness:the classification of surface roughness,estimates of roughness length,and the trend of roughness study.

Based field investigation on soil,plant and growing rate of trees,the afforesting land in Datan demonstrative district of Bashang in Hebei Province was divided into 12 site types:namely middle-lower site of hilly shady slope with thick-layer soil,upper site of hilly shady slope with thin-layer soil,middle-lower site of hilly sunny slope with thick-layer soil:rocky site of hilly top,shady bank site:wet bank site:low and shady hillside site:low and sunny hillside site,gentle gravel land or sandy cultivated land;gentle loam cultivated land,gentle undulate fixed sandy land and semifixed sandy land.

In this paper,the humidity indexes are calculated and the time sequences and periods of precipitation are analyzed according to the temporal and spatial changes of precipitation and humidity in north Xinjiang.The changing laws and features of the climate in north Xinjiang are discussed.Furthermore,by using satellite images and according to the field investigation,the paper discusses the normal and inverse developing processes of Gurbantonggut Desert under the peculiar climate and environment based on the interdependent relations of the desert environment and climate changes.The analyzed results show that the climate change is in a warm-dry period since 1950s although the humidity rises and precipitation increases slightly.Moreover,the area of moving dunes enlarges and desertification becomes serious increasingly in Gurbantonggut Desert.It is considered that climate change is the main cause of enlargement of the area of moving dunes in the desert,and artificial factors play the triggering and accelerating roles.In short,desertification caused by whatever factors will bring about a tremendous harmfulness to human's living environment if the control measures are not positively taken.

The Tkalimakan Desert, situated in the inland basin where there are plenty of alluvial and lacustrine deposit, was gradually formed in Mid - Pleistocene and Holocene under the extreme dry and windy climate. It is a huge and moving sandy desert with complex landforms, However, there are also desertification problems for the deserts mainly formed by natural factors, The desertified land in the Taklimakan Desert Region covers an area of 28,266 km ²,or 9.2% of the total area, of which 6.5% was formed in historical period and 34.9% in contemporary age. The desertification process of historical period in this region mainly occurred in the oases of lower reaches of rivers in the southern and eastern parts of the desert. Owing to the ancient rivers changed their courses (caused by natural or anthopogenic factors) and the reduction of phreatic surface, farmland and settlement were abandoned, thus forming the desertified land. In the northern part, both sides of the Trim River and frontal margin of diluvial and alluvial fans south of the Tianshan Mountain, dry sandy riverbed or abandoned farmlands turned into desertified land due to the river changed its course or long period of irrational irrigation caused the rise of water table and severe secondary salinization of soils. For nearly one hundred years, the desertification process in the Taklimakan Desert Region was aggravated thanks to the interferences of man-made factors and misuse of natural resource destroyed the fragile system, of course, local places resulted from sand dune encroachment. Based on the formation causes, the desertified lands can be divided into three types: l.Sand dune encroachment type 2.Sand dune activation type 3.Gobi sand drift type According to the developmental processes and present status of desertification in the Taklimakan Desert Region, the developmental tendency of desertification was predicted and its controlling measures were suggested. 1. "Green Corridor" area in lower reaches of the river at fringe of the Taklimakan Desert: In the past 25 years, desertification developed rapidly, belonging to severe desertification. It's necessary to work out an overall plan so as to rationally allot water resource in upper, middle and lower reaches: use land resource with establishing grassland as the main aspect; establishing wind breaks to protect farmland, settlement and roads. 2.Shrub sand mound area at fringe of newly reclaimed region: Shifting sand is rapidly explanding, measures must be taken to protect the existing vegetation, in addition to, it needs to establish artificial protective forest at fringe and within the reclaimed area by using trees and shrubs. 3. River banks situated deep in the desert: wind erosion is serious. It's not suitable for the farming here due to high water table and soil secondary salinization. However, there is vast area of natural populus diversifolia forest, therefore, it suits to establish natural preserve.

Study of variations of leaf traits in severely desertified habitats is important not only to understand regional biotic and abiotic features, but also to provide basis for community classification. In this study, patterns of leaf traits of 52 plants are investigated to detect their difference among functional groups and relationships between each trait. The results show that specific leaf area of 52 plants is varied between 6.9~34.4 m2·kg-1, which was relatively lower compared with the results from other regions. This implies that the plants adapt well in poor soil environment in Horqin Sand Land. The N∶P ratio of most plant in this study is less than 14, which means that the plant is constrained by nitrogen in Horqin Sand Land. One way ANVOA analysis shows that leaf traits are different significantly among functional groups. Leaf nitrogen content of N fixers and leaf dry matter content are the highest compared with other functional groups, respectively. However, no significant difference in leaf P concentration and specific leaf area is observed among different functional groups. Specific leaf area in annuals is significantly higher than that in perennials, but leaf dry matter content is relatively low in annuals. Leaf dry matter content of 52 plants is negatively correlated with specific leaf area and leaf nitrogen content, respectively. However, leaf nitrogen content is positively correlated with leaf phosphorus content.

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.

Plant diversity is the basis for ecosystem structure and function， and climate change has had a profound impact on it， even a serious threat. The decrease or loss of plant diversity necessarily affects the stability of ecosystem structure and function， lead to serious ecological， economic and social consequences. Studies have shown that the response of plant diversity to climate change is controlled by the dynamic balance of temperature and water. This research systematically introduced the effects of climate warming and precipitation pattern change on plant diversity. In this report， the impacts of climate change on plant diversity in different ecosystems， community types and scales （global， regional and local scale） are analyzed and the main factors that influence the difference were summarized. We also propose research hotspots and directions for future plant diversity research in different environmental conditions.

The National Key Basic Project (973) “Process and Controlling of Aeolian Desertification in North China”(2000048700) has got the following research results: has reestablished the development, succession, situation and driving mechanism of aeolian desertification in North China during late 2000 years; has disclosed the physical mechanism of soil wind erosion and sand-dust moving; has determined the wind erosion tolerance capacity of soil; has found the formation mechanism, distribution rule and impact of wind blown electrify field; has set up the quantity evaluating system; has confirmed the source area, moving route and formation mechanism of sand-dust, and has established the monitoring, forecasting and for-alarming method and system of sand-dust storm; has studied the attenuation law of C, N in soil and its influence on desert vegetation; has showed the harmed process, adapted countermeasure and recover mechanism of vegetation during aeolian desertification process; has clarified the process, cause, status and development and trend of aeolian desertification in North China during late 50 years; quantificationally showed the spatial distribution and change of aeolian desertification, and has put forward the model and countermeasures of controlling aeolian desertification and coordinating the social economy and environment in typical areas. These results from the project provide the scientific theory for government to control aeolian desertification and make the strategy of sustainable development of arid regions economy and eco-environment, and also has enriched and developed the theory system of Desert Science.

Grain size analysis is one of the main methods to study the process of aeolian sand landform. The analysis of sand dune grain size characteristics can not only reflect the source and power of sand dunes， but also reflect the changes of the terrain to the movement of the sand flow. This paper analyzes the grain size characteristics of the surface sediments of the mobile dunes in different geomorphological positions in the Pengqu Basin of Tibet. The results show that： （1） Surface sediments on mobile dunes in Pengqu basin are mainly divided into medium sand （46.51%） and fine sand （40.52%）， followed by coarse sand （5.87%） and very fine sand （5.87%）， and the content of clay （0.37%） and silt sand is the least （0.85%） . The average grain of surface sediments on mobile dunes is in the range of 1.41-2.32 Φ， and the skewness is in the range of 0.01-0.24 . In general， the kurtosis range is 0.98-1.80， and the sorting coefficient is in the range of 0.45-0.79 Φ. （2） The grain size composition of different geomorphic units （river floodplain-river terrace-hillside） gradually becomes finer； the frequency distribution curve gradually becomes higher and steeper， and the probability accumulation curves from southwest to northeast along the dominant wind direction change from two-stage to one-stage， the slope gradually increases， and the sortability gradually becomes better. （3） The surface sediments of the flowing sand dunes from the floodplain to the high-level terraces of the river become finer with increasing altitude， and the particle size from the slope to the top of the slope becomes coarser with the increase in altitude， but the sorting becomes better， indicating the sand materials of the sand dunes on the hillside and the sand dunes on the terrace come from different river sections of riverbed or floodplain. The research results can provide a scientific basis for the prevention and control of desertification in different areas in the study area.

In order to understand the spatial distribution of P. euphratica fine roots(D≤2 mm)and its relation with soil factors under the extremely arid environment, a middle aged P. euphratica tree which grown at the lower reaches of Tarim River, Xinjiang, China, was selected as a sample tree. By trench profile method, 168 root and soil samples were collected. Results showed that: (1)P. euphratica fine root length density (FRLD), fine root surface area density ( FRSAD) increased from the soil surface to 100-cm soil layer, and decreased from 100-cm to 140-cm layer; P. euphraticaFRLD, FRSAD was mainly concentrated on 60~120 cm soil depth, which accounted for over 74% of whole 0~140 cm soil profiles FRLD, FRSAD. In the horizontal direction, FRLD and FRSAD showed a decreasing trend with a distance between 75~250 cm from the tree trunk, and increased with fluctuation at distance between 350~550 cm. (2)There were negative significant correlations between P. euphratica FRLD and soil total salt, soil available nutrient, and power model can best fit their relations; there was positive correlations between P. euphratica FRLD and soil water, but the correlation was not significant at P=0.05 level, and Cubic model can best fit their relations.

Desert Science of China has developed from nonexistence to pass into existence, and from filling a vacancy to getting rapid progress in the past 50 years under the unremitting efforts of several generation researchers. Meantime, Desertification Research has greatly enriched China Desert Science due to its theory progresses on innovation and systematicness, and practical achievements on economic, social and environmental effects, which has made considerable contribution to the national economy construction and eco-environmental protection of northern China; a great group of research achievements were rewarded with awards including National Scientific Progress Special Grade Award etc. and have made hundred millions of direct economic benefit. In the past 20 years, there were 10% percent of desertified lands were reversed, 12% of them were improved, and part of them came forth new phase of "human advances and desert recedes". Up to now, the desert and desertification research institutions on national level that take The Chinese Academy of Sciences and The State Forestry Bureau as the principal parts have come into being, where assembled with many excellent desert and desertification scientists. The relatively complete desert/desertification science system and research system have been established, which have obtained great progress in studies on blown-sand physics and desert environment, desert formation and evolution, global climate change, desertification process and its control, resource environment and sustainable development of desert area, remote sensing and information about desertification; as one result, abundant research original data have been accumulated. Nowadays, a field long-term observation station net has been set up in China desert and desertification areas, they have been providing scientific research achievement and theory bases. The great successes on desert science and practice of China are popularly recognized by local people, government and international science field.

Soil organic carbon is a significant component of the earth's carbon reservoir, and its storage and fluxes play a major role in the globe budget of carbon. This paper reviewed the advances of domestic and overseas studies on the estimation of soil organic carbon pool, the influence of natural factors and anthropomorphic disturbances including land use/cover changes, over-grazing, agricultural practices and rises of CO ₂ on soil organic carbon storages. In addition, the effects of soil organic carbon on soil quality and environment regulation, some strategies of sequestering C in soil were presented. The significance of studies on soil organic carbon changes and its ecological effects were discussed.

Based on daily precipitation data from 55 meteorological stations in Xinjiang, China during 1961—2004 and the daily precipitation data simulated by PRECIS (Providing Regional Climates for Impacts Studies), the series of precipitation extremes, which contain annual maximum precipitation and annual maximum consecutive dry days, were constructed, and the distribution features of precipitation extremes were analyzed on the base of the two data series. Results show that: 1) the intensity and probability of annual maximum precipitation are the highest in Aheqi, Barkul, Zhaosu and Urumqi, and the intensity and probability of annual maximum consecutive dry days are the highest in Qiemo, Ruoqiang and Turpan; 2) compared with observational data, inter-annual average maximum precipitations simulated by PRECIS are higher, and the discrete coefficients of annual maximum precipitation simulated by PRECIS are higher too; 3) in spite of certain differences of the spatial distributions between observed and simulated precipitation extremes, the PRECIS simulation data have reference value. Fitting of precipitation extremes observation data shows that general extreme value distribution can fit the probability distribution of precipitation extremes quite well.

We calculated monthly water vapor content using measurement data in 1976-2009 from Yining radiosonde station, and established W-e model suitable for the Ili River basin with ground vapor pressure, calculated the water vapor content in the Ili River basin in 1961-2009 combining with the DEM data, analyzed the temporal and spatial distribution characteristics of water vapor and precipitation with EOF and cross spectrum method, and researched water vapor transport characteristics during typical strong precipitation process in summer in dry and wet years. In the Ili River basin, the water vapor content at the west is more than at the east, the plain is more than the mountain, the windward slope is more than leeward slope, and downstream plain and upstream valley areas are high value areas with water vapor content of 13-15 mm. It is related to the terrain and distribution of the oasis towns. At 850 hPa and 700 hPa height, there is a maximum water vapor area, corresponding to an altitude around 2 000 m. Water vapor increased at inter-decadal scale and increased obviously in summer(0.48 mm/10a). Precipitation and water vapor EOF decomposition standardization fields show that their temporal and spatial distributions are extremely similar, and there are distribution types of climate vibration consistency and north-south opposite distribution type for the river valley. The fountainheads of water vapor give priority to Tropical Marine in rainy season, and water vapor content also is influenced by water vapor transmission from the Arctic Ocean.

A time series of SPOT-VEGETATION Normalized Difference Vegetation Index (NDVI) data with 1 km×1 km spatial resolution were used to monitor the vegetation cover change during the period of 1998 to 2004 in Northwest China. The MVC (Maximum Value Composites) method and the linear regression were used to characterize the trends in vegetation cover change. And the landuse map of Northwest China was used to analysis the NDVI variety of different landuse types. During the last 7 years, the vegetation degradation was popular in most regions of Northwest China. However, there were some regions where vegetation cover was increasing, but the increasing range was smaller than the decreasing range on the whole. The results indicated that the improved regions of vegetation cover mainly appeared in the major part of Shaanxi and Ningxia province and in the northwest and southeast parts of Xinjiang. But in the most part of Northwest China, the NDVI was reducing. However in the same particular year, the patterns of NDVI variety of different vegetations were in the similar tendency.

Variation of wind profile and sand flow structure are the most visualized manifest in sand blown geomorphology under coupling of saltatory sand and wind field. Based on observation of wind profile and sand flow structure above a barchan dune in the Taklimakan Desert and comparison with those over a reference point (the flat ground between the longitudinal dunes), we found some variations of the wind profile and the wind-sand flow structure. Affected by perturbation of dune landform, the wind profiles above dune slip face and two horns' nose are all manifested as non-logarithmic function form. Except for the foot of stoss slope, the sand flow structure above all other positions of the barchan dune are different to that over the reference point. Curve functions are fitted for the sand flow structures, and the segmental fitting is especialy used to fit those sand flow structure having segmental phenomenon.

Soil microbiotic crust is developed broadly and has an ecological significance in arid and semiarid regions. This paper reviewed the advances of domestic and overseas studies, which on characteristics of the formation and development of microbiotic crust, its effects on microhabitat, including physical and chemical properties of soil, endurance to wind and water erosion, the distribution of precipitation in spatial and time, nutrient and chemical elements variance in soil process and geo-bio-chemical cycling process, and influence on vegetation dynamics. In addition, the several contradictory research conclusions were synthetical analyzed. The role and function of microbiotic crust in ecological restoration of arid and semiarid regions of China were discussed.

China desertification research has experinced several decades of hard struggle along with the establishment and development of China desert sciences. The research has made great contribution to national economic construction and China desert scientific system's formation. In the past 40 years, considerable achivements have been made in desertification research fields such as basic research, dynamic monitoring and evaluation, vegetation evolution, landscape ecology, plant stress physiology, ecosystem, highly efficient use and sustainable development of water and land resources, treatment model and technology, etc. The key fields of China desertification research in the future are blown sand physics and desert environment, rehabiliatation ecology, water and land resources utilization and agricultural sustainable development, desertification reversion and treatment model, etc.

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.

Based on hourly precipitation data from May to September during 1991—2010 from Urumqi meteorological station, the features of rainfall change during recent 20 years were analyzed. Results showed that the diurnal variations of hourly precipitation and rainfall frequency were consistent. The peaks of hourly rainfall and rainfall frequency both occurred from 20:00 to 11:00, and the minimum value occurred at 16:00. The frequency of rainfall less than or equal to 1.0 mm·h-1 was the most, which was followed by the frequency of rainfall great than or equal to 1.1 mm·h-1 but less than or equal to 3.0 mm·h-1. Nevertheless, the contribution of the latter was the biggest to precipitation. Different magnitudes of precipitation intensity had some different yearly change. The frequency of light rain was the most, the second were moderate rain and heavy rain, and the least was torrential rain. In a day, light rain, moderate rain and heavy rain occurred with the most frequency at the first half of the night, torrential rain at afternoon. During a year, light rain occurred with the most frequency in the middle of July, moderate rain in the middle of May, heavy rain in mid-to-late May, and torrential rain in early and middle of May, middle of July, and late August. The peaks of rainfall events with duration of 1-3 hours occurred at the first half of the night, that with duration of 4-6 hours and 7-9 hours often appeared at night, and that with 10-12 hours duration often appeared in the afternoon and after midnight. The inter-annual change of total rain days is these 20 years in Urumqi was not significant. Compare to during 1991-2000, the torrential rain days increased during 2001-2010, while the days of the other magnitudes decreased.

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.

Experiments on sorts and densities of seeds in different biological soil crusts were conducted in natural illumination. The experiment was arranged in four treatments: moss crust in dry and moist condition, algae crust in dry and moist condition. The result indicates that: (1)there are nine kinds of seeds germinated in the two sorts of crusts, they are Artemisia ordosica Krasch Chenopodium glaucum L, Allium polyirhizum Turcz.ex Rgl., Rragrostis poaeoides Beauv, Amaranthus.retroflexus L., Potulaca oleracea L, Setaria viridis (L.), Bassia dasyphylla （Fisch.et Mey）respectively, among them, seven kind of plants are the annual; (2) the differences of seeds number in different crusts are significant: in moist crusts, there is an extremely significant difference(P<0.001), in dry crust, there is a significant difference(P<0.05); (3)from the different water content in crusts, and the difference of germinated seeds(P<0.001), we can conclude that water content in crusts is the main restriction to numbers of germinated seeds.

Soil spatial heterogeneity is very huge in Hunshandake Sandy Land. Soil grain size on shifting dunes and soil nutrient content on non-desertified lands exist very obvious difference. With the development of land desertification, a coarse sands accumulation layer often formed in the surface of soil, and the content of soil organic carbon (SOC) and the total Nitrogen (TN) both decrease obviously. Moreover, the content of SOC has bigger spatial difference than the content of TN. With the increase of desertification severity, the content of SOC decreases much faster than the content of TN, causing the ratio of C and N decrease obviously. There are close correlation between the content of SOC, the content of TN and the clay particles content in top soil layers of desertified lands. Soil wind erosion is the main driving factor of soil developing process in land desertification, and it seriously affect the soil stability, the transfer of soil fine material composition and nutrient.

Most of the arid and semiarid regions in China have experienced multiple arid phases throughout the Quaternary, and they are highly sensitive to climate change. However, the response of desertification to climate change is poorly understood. In the present study, we selected multiple climatic proxies and desertification evidences to estimate the responses of desertification to climate changes in arid and semiarid regions of China over the past millennium. Desertification generally decreased in western China during the Little Ice Age (LIA), but increased during the Medieval Warm Period (MWP) and the Current Warm Period (CWP), which suggested the environment in western China was inclined to meliorate in cold period and deteriorate in warm period. The central and eastern regions of China tended to experience desertification in LIA, but desertification reversed in MWP and CWP, which indicated the central and eastern regions of China were prone to undergo desertification in cold period but desertification reversed in warm period. However, the desertification cycles in the Qinghai-Tibetan Plateau region showed fluctuation responding to climate change.

Since the middle of the 20th century， desert tourism has risen and been loved by the public， and the improvement of the ecological environment has also prompted many sightseeing-type desert-themed scenic spots to vacation-type. The number of desert scenic spots in China has increased year by year towards high quality and diversification. However， desert scenic spots also face many difficulties in the development process， such as the financing difficulties caused by high construction cost， short stay for the tourists， single tourism products， insufficient publicity and other problems. Based on the analysis of relevant website data and the comparison of excellent cases at home and abroad， this article makes a forward-looking reflection on the problems existing in desert tourism， and puts forward five solutions， which are to broaden financing channels， strengthen product innovation， reasonably allocate activities and accommodation facilities， create scenic roads and promote with the help of new media.