Understanding the relationship between the changes in lake water volume and climate change can provide valuable information to the recharge sources of lake water. This is particularly true in arid areas such as the Badain Jaran Sand Sea, an ecologically sensitive area, where the recharge sources of lakes are heatedly debated. In this study, we determined the areas of 50 lakes (representing 70% of the total permanent lakes in this sand sea) in 1967, 1975, 1990, 2000 and 2010 by analyzing remote-sensing images using image processing and ArGIS software. In general, the total lake area decreased from 1967 to 1990, remained almost unchanged from 1990 to 2000, and increased from 2000 to 2010. Analysis of the relationship between these changes and the contemporaneous changes in annual mean temperature and annual precipitation in the surrounding areas suggests that temperature has significantly affected the lake area, but that the influence of precipitation was minor. These results tend to support the palaeo-water recharge hypothesis for lakes of the Badain Jaran Sand Sea, considering the fact that the distribution and area of lakes are closely related to precipitation and the size of megadunes, but the contemporaneous precipitation can hardly balance the lake water.

The formation and development of dunes depend on wind-blown sand movement which is affected by the characteristics of sand material, topography, wind regimes and other factors. In this paper, we investigated two sand shadow dune groups in Shigatse and Za’gya Zangbo of Tibet and an individual dune in Da Qaidam of Qinghai, and analyzed their topographies and morphologies, and the physical characteristics of the sand, wind regime and sand transport. Formed under harsh conditions behind hills, these mature sand shadow dunes are hundreds of meters long, have significant ridges and crescent dunes downwind, and have a hill pass on one or both sides. Wind tunnel experiments revealed that the hill gap and wind velocity are important factors in the formation of these dunes. Sand shadow dunes formed only when the gap spacing is two-thirds of the hill height. When wind velocities are 20 m/s, the sand body is divided into two parts. The hill pass allows the transport of sand by wind, creating a “narrow-pipe effect”, which causes the transported material to gradually accumulate in the center of the shadow zone. We observed that the following are needed for sand shadow dunes to form: (1) strong winds, sufficient sand, suitable obstacles and a dry climate; (2) one or both sides of the obstacle forming the shadow zone must have a hill pass; and (3) the windward side of the obstacle must have a wide, flat area, providing adequate spacing for wind flow and transport of material and the leeward side must have a sufficiently broad, flat area to allow the release of the transported material. Research results on these newly discovered dunes on the Qinghai-Tibet Plateau could contribute to the understanding of dune geomorphology.

The assessment of the water losses by actual evapotranspiration plays a very important role in water resources management, especially in particular environments suffering soil water stresses and water shortages. The rationales of this study are the scarcity of experimental data, the difficulties in the measurement of direct and continuous evapotranspiration fluxes, and the switching between controls by climate and soil water availability. The temporal patterns of observed soil moisture and air temperature of over three years at an experimental site in southern Italy have been analysed to investigate the relation between them and the actual evapotranspiration volume, estimated using the soil water budget method. To this end, an event-based empirical analysis has been performed, exploring the relation between the mentioned variables. One of the major findings of the explorative phase is the qualitative and quantitative identification of the switching between climate and soil water balance as the controls over actual evapotranspiration at the experimental site. This threshold process has then been modelled at the event and sub-event scale, establishing simple empirical equations to predict actual evapotranspiration losses as a function of soil water content. Multilevel-recorded data also allowed the investigation of the importance of soil depth.

The Dunhuang Mogao Grottoes in China was designated as a world heritage site by UNESCO in 1987 and is famous for its cultural relics. Water is the most active factor that harms the relics in the caves as it damages the grotto murals and painted sculptures. Thus, determining the water sources and driving forces of water movement is a key issue for protecting these cultural relics. These issues have troubled relics protectors for a long time. In this study, the authors chose a representative cave in the Mogao Grottoes and, by completely sealing the cave to make a closed system, measured the water vapor from the surrounding rock. This was accomplished by installing a condensation–dehumidification temperature–humidity control system for the collection of water vapor. The results show that there is continuous evaporation from the deep surrounding rock into the cave. The daily evaporation capacity is determined to be 1.02 g/(d•m2). The water sources and driving forces of water movement were further analyzed according to the character of the water evaporation and by monitoring the temperature and humidity of the surrounding rock. It was found that the water vapor in the cave derives from phreatic water. Moreover, the yearly fluctuation of temperature in the surrounding rock and geothermal forces are the basic powers responsible for driving phreatic evaporation. Under the action of the yearly temperature fluctuations, decomposition and combination of bound water acts as a “pump” that drives phreatic water migration and evaporation. When the temperature rises, bound water decomposes and evaporates; and when it falls, the rock absorbs moisture. This causes the phreatic water to move from deep regions to shallow ones. Determining the source and dynamic foundation of the water provides a firm scientific basis for protecting the valuable cultural relics in the caves.

Gravel–sand mulch has been used for centuries to conserve water in the Loess Plateau of north-western China. In this study, we assessed the influence of long-term (1996–2012) gravel–sand mulching of cultivated soils on total organic carbon (TOC), light fraction organic carbon (LFOC), microbial biomass carbon (MBC), total organic nitrogen (TON), particulate organic carbon (POC), mineral-associated organic carbon (MOC), permanganate-oxidizable carbon (KMnO₄-C), and non-KMnO₄-C at 0–60 cm depths. Mulching durations were 7, 11 and 16 years, with a non-mulched control. Compared to the control, there was no significant and consistently positive effect of the mulch on TOC, POC, MOC, KMnO₄-C and non-KMnO₄-C before 11 years of mulching, and these organic C fractions generally decreased significantly by 16 years. LFOC, TON and MBC to at a 0–20 cm depth increased with increasing mulching duration until 11 years, and then these fractions decreased significantly between 11 and 16 years, reaching values comparable to or lower than those in the control. KMnO₄-C was most strongly correlated with the labile soil C fractions. Our findings suggest that although gravel–sand mulch may conserve soil moisture, it may also lead to long-term decreases in labile soil organic C fractions and total organic N in the study area. The addition of manure or composted manure would be a good choice to reverse the soil deterioration that occurs after 11 years by increasing the inputs of organic matter.

Phenological events for desert plants were recorded and rainfall and temperature data were gathered over a three-year time scale at a gravel plain in the eastern region of the United Arab Emirates. Variations of phenological periods were analyzed and correlations between phenological periods and climate factors were discussed. The study showed that the growth and flowering of therophytes were significantly correlated with air temperature. The timing and abundance of rainfall came to be another factor significantly correlated with the onset and duration of chamaephyte flowering as well as the duration of therophyte growth and flowering. The variation in rainfall did not affect the onset of flowering in phanerophytes. Peak growing seasons were from November to March and flowering from November to December (also February to March depending on the availability of rainfall). Flowering in phanerophytes and chamaephytes occurs 4–6 weeks and in therophytes 4–8 weeks after rain. The results showed that variations in growth and phenology between species were correlated with environmental factors, such as temperature and rainfall or, maybe, differences in life form and photosynthetic pathways, each being adapted for utilizing a particular phase of the seasonally and yearly variable rainfall. The sequence of flowering for the species under study was more or less constant despite the difference in the amount of rainfall. The fruiting patterns of most of the species were also found parallel to their flowering patterns. Our results emphasized the need to study multiple species at many sites for the understanding and forecast of regional changes in phenology.

The mountainous forests in arid regions, being sensitive to climate change, are one of the key research topics related to the mechanism of interaction between climate and the terrestrial ecosystem. In this study, the spatial distribution of a mid-mountain forest and its environmental factors were investigated by using a combination of remote sensing technology, field survey, climate indices and soil nutrient analysis in the Sangong River watershed of the northern Tianshan Mountains. The forest (Picea schrenkiana) was distributed between 1,510 and 2,720 m asl. Tree height and diameter at breast height (DBH) exhibited a bi-modal pattern with increasing elevation, and rested at 2,450 and 2,250 m asl, respectively. The two maxima of DBH appeared at 2,000 and 2,550 m asl, and the taller trees were observed at 2,100 and 2,600 m asl. For the annual mean temperature, the difference was approximately 5.8°C between the lowest and the highest limits of the forest, and the average decreasing rates per hundred meters were 0.49°C and 0.55°C with increasing altitude between 1,500 and 2,000 m asl and above 2,000 m asl, respectively. The annual precipitation in the forest zone first increased and then decreased with the increase of altitude, and the maximum value was at 2,000 m asl. For per hundred meters, the annual precipitation increased with the rate of 31 mm between 1,500 and 2,000 m asl and decreased by 7.8 mm above 2,000 m asl. The SOM, TN and TP were high between 2,000 and 2,700 m asl and low at the lower and upper forest limits. The minimum CaCO3 concentration, pH value and EC coincided with the maximum precipitation belt at 2,000 m asl. The SOM, TN and TP were high in the topsoil (0–10 cm) and differed significantly from the values observed in the deep soil layers (>10 cm). The soil nutrients exhibited spatial heterogeneity and higher aggregation in the topsoil. In conclusion, soil and climate are closely related to each other, working synergistically to determine the development and spatial distribution of the mid-mountain forest in the study area. The order of the importance of environmental factors to forest development in this study is as follows: soil nutrients>precipitation>elevation>temperature.

Water is a restrictive factor for plant growth and ecosystem stability in arid and semiarid areas. The dynamics of water availability in soils and water use by plants are consequently critical to ecosystem functions, e.g. maintaining a high resistance to the changing climate. Plant water use strategies, including water-use efficiency (WUE) and the main water source that a plant species utilizes, play an important role in the evaluation of stability and sustainability of a plantation. The water use strategies of desert plants (Tamarix chinensis, Alhagi sparsifolia, Elaeagnus angustifolia, Sophora alopecuroides, Bassia dasyphylla and Nitraria sphaerocarpa) in three different habitats (saline land, sandy land and Gobi) in Dunhuang (located in the typical arid area of northwestern China) were studied. The stable isotope of oxygen was used to determine the main water source and leaf carbon isotope discrimination was used to estimate the long-term WUE of plant species in the summer of 2010. The results suggest that: 1) the studied desert plants took up soil water below the depth of 80 cm; 2) T. chinensis in the three habitats used deeper soil water and T. chinensis in the Gobi site had higher WUE than those in the saline land and the sandy land. The results indicated that desert plants in Dunhuang depended on stable water source and maintained high WUE to survive in water limited environments.

In this study, we determined carbon allocation and carbon stocks in the plant-soil system of different dune ecosystems in northeastern China. We quantified the species composition, above- and below-ground biomasses, and carbon stocks of three dune types (i.e. active dunes, semi-stabilized dunes and stabilized dunes) and their corresponding inter-dune lowlands (i.e. interdune lowlands of active dunes, interdune lowlands of semi-stabilized dunes and interdune lowlands of stabilized dunes) in the Horqin Sandy Land. The results showed that the succession series on interdune lowlands of the Horqin Sandy Land confirmed differences in species composition of the various dune types. Aboveground carbon (AGC) on the interdune lowlands of semi-stabilized dunes (33.04 g C/m²) was greater (P<0.05) than that on the interdune lowlands of active dunes (10.73 g C/m²). At the same time, the different dune types did not show any significant differences (P>0.05) in belowground plant carbon (BGC). However, the percentage of plant BGC in interdune lowlands of active dunes (81.5%) was significantly higher (P<0.05) than that in the interdune lowlands of semi-stabilized dunes (58.9%). The predominant carbon pool in the study dune ecosystem was in the soil. It accounted for 95% to 99% of total carbon storage. Soil organic carbon (SOC) was at least 55% greater (P<0.05) in the interdunes than in the dunes. Stabilized dunes showed at least a 37% greater (P<0.05) SOC content than active dunes up to a 1-m soil depth. Meanwhile, SOC content of interdune lowlands of semi-stabilized dunes was greater (P<0.05) than that of interdune lowlands of active dunes only up to a 20-cm soil depth. The dune ecosystem showed a great potential to store carbon when interdune lowlands of active dunes were conversed to interdune lowlands of semi-stabilized dunes, which stored up to twice as much carbon per unit volume as interdune lowlands of active dunes.

Agriophyllum squarrosum is an annual desert plant widely distributed on mobile and semi-mobile dunes in all the sandy deserts of China. We studied the growth and physiological properties of A. squarrosum seedlings under different sand burial depths in 2010 and 2011 at Horqin Sandy Land, Inner Mongolia to understand the ability and mechanism that A. squarrosum withstands sand burial. The results showed that A. squarrosum had a strong ability to withstand sand burial. Its survival rate, plant height and biomass increased significantly at a burial depth 25% of seedling height and decreased significantly only when the burial depth exceeded the height of the seedlings; some plants still survived even if the burial depth reached 266% of a seedling height. The malondialdehyde (MDA) content and membrane permeability of the plant did not change significantly as long as the burial depth was not greater than the seedling height; lipid peroxidation increased and cell membranes were damaged if the burial depth was increased further. When subjected to sand burial stress, superoxide dismutase (SOD) and peroxidase (POD) activities and free proline content increased in the seedlings, while the catalase (CAT) activity and soluble sugar content decreased. Sand burial did not lead to water stress. Reductions in photosynthetic area and cell membrane damage caused by sand burial may be the major mechanisms increasing mortality and inhibiting growth of the seedling. But the increases in SOD and POD activities and proline content must play a certain role in reducing sand burial damage.

Biological soil crusts (BSCs) are capable of modifying nutrient availability to favor the estab-lishment of biogeochemical cycles. Microbial activities serve as critical roles for both carbon and nutrient transformation in BSCs. However, little is known about microbial activities and physical-chemical properties of BSCs in the Gurbantunggut Desert, Xinjiang, China. In the present research, a sampling line with 1-m wide and 20-m long was set up in each of five typical interdune areas selected randomly in the Gurbantunggut Desert. Within each sampling line, samples of bare sand sheet, algal crusts, lichen crusts and moss crusts were randomly collected at the depth of 0–2 cm. Variations of microalgal biomass, microbial biomass, enzyme activities and soil physical-chemical properties in different succession of BSCs were analyzed. The relationships between microalgal biomass, microbial biomass, enzymatic activities and soil physical-chemical properties were explored by stepwise regression. Our results indicate that microalgal biomass, microbial biomass and most of enzyme activities increased as the BSCs developed and their highest values occurred in lichen or moss crusts. Except for total K, the contents of most soil nutrients (organic C, total N, total P, available N, available P and available K) were the lowest in the bare sand sheet and significantly increased with the BSCs development, reaching their highest values in moss crusts. However, pH values significantly de-creased as the BSCs developed. Significant and positive correlations were observed between chlorophyll a and microbial biomass C. Total P and N were positively associated with chlorophyll a and microbial biomass C, whereas there was a significant and negative correlation between microbial biomass and available P. The growth of cyanobacteria and microorganism contributed C and N in the soil, which offered substrates for enzyme activities thus increasing enzyme activities. Probably, improvement in enzyme activities increased soil fertility and promoted the growth of cyanobacteria, eukaryotic algae and heterotrophic microorganism, with the accelerating succession of BSCs. The present research found that microalgal-microbial biomass and enzyme activities played important roles on the contents of nutrients in the successional stages of BSCs and helped us to understand developmental mechanism in the succession of BSCs.

Shrub presence has an important effect on the structuring of ground beetles in desert ecosystems. In this study, in order to determine how shrubs and different species influence ground beetle assemblages in a sandy desert scrubland dominated by two different shrub species, namely Calligonum mongolicum and Nitraria sphaerocarpa, we sampled the ground beetles using pitfall traps during spring, summer and autumn in 2012. At the community level, the activity density of the ground beetles was shown to be significantly higher under shrubs than in intershrub bare habitats in spring; but an opposite pattern occurred in autumn, suggesting the presence of season-specific shrub effects on the activity density of the ground beetles. Meanwhile, at the trophic group level, the activity density and species richness of predators were significantly greater under shrubs than in intershrub bare habitats in spring, whereas an opposite trend occurred on the activity density in autumn. N. sphaerocarpa shrubs had a positive effect on the activity density of herbivores in the three seasons, and C. mongolicum shrubs had a positive effect on the activity density of detritivores in spring and autumn. At the species level, more Microdera sp. was captured under shrubs than in intershrub bare habitats in spring. During the same time, we also found that C. mongolicum shrubs had a positive effect on Blaps gobiensis in spring, Carabus sp. in autumn, and Tentyria sp. in spring and autumn, and N. sphaerocarpa shrubs had a positive effect on Cyphogenia chinensis, Sternoplax setosa in spring and summer, and Curculionidae sp. 1 in summer and autumn. The study results suggest that shrub presence, shrub species and season variation are important factors for ground beetle assemblages in this desert ecosystem, but the responses of beetles differed among trophic and taxonomic levels.

With the development of large-scale hydrologic modeling, computational efficiency is becoming more and more important. Rapid modeling and analysis are needed to deal with emergency environmental disasters. The Soil and Water Assessment Tool (SWAT) is a popular hydrologic model, which is less applied in large-scale watershed simulation because of its sequential characteristics. For improving the computational efficiency of the SWAT model, we present a new parallel processing solution for hydrologic cycle and calibration based on MPI (Message Passing Interface). We partitioned sub-basins during the processes based on a load balancing method. Then the calibration was parallelized using a master-slave scheme, in which different input parameters were allocated to different processes to run the hydrologic cycle and compute the function value. Because of the slow convergence and local optimization of the SCE-UA (Shuffled Complex Evolution-developed by University of Arizona) algorithm in SWAT calibration, a genetic algorithm (GA) is developed to optimize the calibration step. Then by dividing the default communicator into several sub-communicators, all the hydrologic cycles were parallelized in their own sub-communicators to achieve further acceleration. In this paper the results show speedups for the hydrologic cycle calculations, as well as in the optimized calibration step. In the case study, we tested the parallel hydrologic cycle by four processes, and got a speedup of 3.06. In the calibration section, after applying the GA optimization, with 10 cores, we got a speed increase of 8.0 in our GA parallel framework compared with the GA sequential calibration, which is much better than the original SWAT calibration. After the sub-communicators added, this process was speeded up even further. The study demonstrated that the GA parallel framework with multi-sub-communicators is an effective and efficient solution for the hydrologists in large scale hydrology simulations.