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Background Escaping from ER stress-induced apoptosis plays an important role in the progression of many tumours. However, its molecular mechanism in osteosarcoma remains incompletely understood. Methods The molecular mechanism was investigated using RNA sequencing, qRT–PCR and Western blot assays. The relationship between LINC00629 and KLF4 was investigated using RNA pulldown and ubiquitylation assays. The transcriptional regulation of laminin subunit alpha 4 (LAMA4) by KLF4 was identified using bioinformatic analysis, a luciferase assay, and a chromatin immunoprecipitation assay. Results Here, we demonstrated that LINC00629 was increased under ER stress treatment. Elevated LINC00629 inhibited ER stress-induced osteosarcoma cell apoptosis and promoted clonogenicity and migration in vitro and in vivo. Further mechanistic studies indicated that LINC00629 interacted with KLF4 and suppressed its degradation, which led to a KLF4 increase in osteosarcoma. In addition, we also found that KLF4 upregulated LAMA4 expression by directly binding to its promoter and that LINC00629 inhibited ER stress-induced apoptosis and facilitated osteosarcoma cell clonogenicity and metastasis by activating the KLF4-LAMA4 pathway. Conclusion Collectively, our data indicate that LINC00629 is a critical long noncoding RNA (lncRNA) induced by ER stress and plays an oncogenic role in osteosarcoma cell by activating the KLF4-LAMA4 axis.

Natural gas has become a transitional bridge from fossil to green and clean energy worldwide. The importance of natural gas utilization in energy structure optimization and green development is no exception for China. However, the supply of China’s natural gas limits the country’s demand with three factors. (1) China’s natural gas resource is relatively rich, but its quality is poor with deep burial depth. Therefore, the annual plateau yield of natural gas cannot be high, with an estimated value of approximately 260–270 × 109 m3. (2) The demand for natural gas in China’s economic development is growing rapidly. The peak demand is estimated to be approximately 550–650 × 109 m3 per year or even higher. The import volume of natural gas will soon exceed that of domestic self-produced gas. (3) Natural gas is a necessity closely related to livelihood. Particularly, a shortage in natural gas supply affects social stability. Therefore, its external dependency should be under 50% and not exceed 60%. In this study, the future situation of China’s natural gas is forecasted, and relevant countermeasures and suggestions are proposed in accordance with research on China’s natural gas resource potential, production trend, supply-demand link, and gas supply safety factors.

Nebkhas, discrete sand mounds formed with a plant, are a common landscape feature critical to the stability of desert ecosystems. However, adaptations which allow plants to thrive in nebkhas in extremely arid regions are still unclear. The objectives of this study were to test the role of adventitious roots (AR) in the growth and development of Nitraria sphaerocarpa-vegetated nebkhas. We determined biomass distribution patterns and nutrient levels in small, medium, and large nebkhas representing different stages of nebkha development from young to mature, respectively. Our results showed that biomass allocation patterns and nutrient levels were very different among the different nebkha sizes. The proportions of leaves and stems increased with the increase in nebkha size, while those of AR and initial roots (IR) decreased. This indicated that, with an increase in nebkha size, N. sphaerocarpa allocated a higher proportion of biomass to leaves and stems mainly at the expense of roots, and that allowed plants to withstand increased burial depth. The proportion of AR, especially fine AR, varied among nebkha sizes. The proportion of AR in large nebkhas was significantly higher than in small nebkhas. For small and medium nebkhas, the proportion of fine AR was smaller than that of fine IR; for large nebkhas, the proportion of fine AR was higher. This indicated that AR, produced higher on the buried stems in the late stages of nebkha development, may provide increased access to water and nutrients to ensure nebkha survival. Nutrient levels were different in AR and IR of different nebkha growth stages. N and P contents of coarse AR and IR increased with nebkha size. For small nebkhas, N and K levels in fine AR were significantly lower than those in IR; however, for large nebkhas, N and K levels in AR were significantly higher than those in IR. This indicated that AR in the late stages of nebkha development may have stronger absorptive capacity for resources than IR. We conclude that AR are key factor which ensured both the survival and development of N. sphaerocarpa nebkha in extremely arid environment.

A large number of primary oil and gas reservoirs have been discovered in Proterozoic strata all over the globe. Proterozoic sequences are widely distributed in China, and the discovery of large Sinian-aged gas reservoirs in the Sichuan Basin and Mesoproterozoic liquid oil seepages in North China shows that attention should be paid to the exploration potential of Proterozoic strata. In this paper, the main controlling factors of Proterozoic source rocks are discussed. Principally, active atmospheric circulation and astronomical cycles may have driven intense upwelling and runoff to provide nutrients; oxygenated oceanic surface waters could have provided suitable environments for the organisms to thrive; volcanic activity and terrestrial weathering caused by continental break-up would have injected large amounts of nutrients into the ocean, leading to persistent blooms of marine organisms; and extensive anoxic deep waters may have created ideal conditions for the preservation of organic matter. Additionally, the appearance of eukaryotes resulted in diversified hydrocarbon parent material, which effectively improved the generation potential for oil and gas. Through the comparison of Formations across different cratons, seven sets of Proterozoic organic-rich source rocks have been recognized in China, which mainly developed during interglacial periods and are also comparable worldwide. The Hongshuizhuang and Xiamaling Formations in North China have already been identified previously as Mesoproterozoic source rocks. The early Proterozoic Changchengian System is highly promising as a potential source rock in the Ordos Basin. In the Upper Yangtze area, the Neoproterozoic Datangpo and Doushantuo Formations are extensively distributed, and represent the major source rocks for Sinian gas reservoirs in the Sichuan Basin. Moreover, the Nanhuan System may contain abundant shales with high organic matter contents in the Tarim Basin, although this possibility still needs to be verified. Indeed, all three cratons may contain source rocks of Proterozoic strata; thus, these strata represent major exploration targets worthy of great attention.

Clonal propagation is the main strategy for clonal plants to adapt to wind-sand habitat, and underground bud bank could reflect the potential ability of clonal propagation. However, the effects of population density on belowground bud bank are unknown, hindering efforts in the process of dune stabilization. We investigated the horizontal density and vertical distribution of belowground bud bank of a typical rhizomatous grass Leymus secalinus, and soil water content in four dune types with different population density (dune type I: 11.2 ± 1.7 no. m−2, type II: 24.2 ± 2.6 no. m−2, type III: 40.0 ± 4.0 no. m−2, and type IV: 53.5 ± 7.2 no. m−2) in Mu Us sandy land. Our results showed that (1) total bud density of population increased markedly with increasing population density, but it did not exhibit significant difference between dune types III and IV, where density was about 130 buds m−2; and tiller bud density of population first increased, then decreased, and reached a maximum in dune type III. (2) Total bud density per individual in dune type III was significantly larger than that in other dune types (P 0.05). (3) Buds tended to be concentrated at 10–30 cm soil layer in all dune types, and be buried deeper in dune types III and IV than that in dune types I and II. (4) No pronounced relationship was shown between bud density and soil water content in 10–30 cm soil layer with increasing population density. Our results suggest that moderate population density (40.0 ± 4.0 no. m−2) significantly increase the bud bank density of L. secalinus population and individual. Soil water content was not the main factor responsible for the density of L. secalinus bud bank. These results can provide important information for implementation of effective sand fixation measures and species selection for desertification control in semiarid sandy land ecosystems.

Desert lakes are unique ecosystems found in oases within desert landscapes. Despite the numerous studies on oases, there are no reports regarding the spatiotemporal distribution and causes of eutrophication in the desert lakes that are located at the edge of the Linze Oasis in northwestern China. In this study, the seasonal shoreline and eutrophication of a desert lake were monitored using an unmanned aerial vehicle (UAV) and water sampling during three crop growth stages. The spatial extents of the shoreline and algal blooms and the chromophoric dissolved organic matter (CDOM) absorption coefficient were derived through UAV images. The desert lake shoreline declined during the crop growing stage, which exhibited the largest water demand and began to expand after this stage. The estimated CDOM absorption coefficient measurements and classified algal bloom area showed seasonal variations that increased from spring to late summer and then decreased in autumn. The first two crop growth stages accounted for most of the water and fertilizer requirements of the entire growth period, which may have contributed to large amounts of groundwater consumption and pollution and resulted in peak eutrophication of the lake in the second growth stage. However, the CDOM absorption coefficient of the third stage was not well correlated with that of the first two stages, suggesting that the lake may be affected by the dual effects of groundwater and precipitation recharge in the third stage. These results indicate that the water quality of desert lakes may be affected by agricultural cultivation. The agricultural demands for water and fertilizer may change the spatiotemporal changes in water quality in the lake, especially in the middle and early stages of crop growth.

The simulations from climate models require bias correction prior to use in impact assessments or when used as predictors in statistical or dynamic downscaling models. Recent works have sought to address each of these limitations and the results are the Multivariate Recursive Nesting Bias Correction (MRNBC) and Multivariate recursive Quantile-matching Nested Bias Correction (MRQNBC) methods. The model was applied to a mountain region of Heihe River. A comparison of the historical and generated statistics shows that the model preserves all the important characteristics of meteorological variables at daily, monthly, seasonally and annual time scales. This study has documented the performance of Multivariate Recursive Nesting Bias Correction to remove the discrepancy between the predictors in the simulated GCM and the reanalysis NCEP data and assess the projected future precipitation accuracy in the headwater region of Heihe River. A relatively high spatial resolution GCM outputs—ACCESS1-3—from the CMIP5 Earth System Models (ESMs) was employed to downscale for the historical 1960–2005 and the future period 2010–2100 under the scenarios of Representative Concentration Pathways RCP4.5 and RCP8.5. The MRNBC method can dramatically increase the performance of the simulated precipitation data. Verified by statistical score metrics applied for evaluation of the results, the developed method appears to be an important statistical tool in the correction of the bias between the GCM output and the reanalysis data, leading to significant improvements in the predictive performance accuracy of the precipitation projections. The projected precipitation under RCP8.5 appeared to exhibit the significant increasing trend relative to the RCP4.5 scenario in the headwater region of Heihe River. Future precipitation will increasing by 8% and 20% for near and long term period under RCP4.5 and increasing 14% and 37% for near and long term period, under RCP8.5, respectively.

Climate change is shifting the amount and frequency of precipitation in many regions, which is expected to affect seedling recruitment across ecosystems. However, the combined effects of precipitation amount and frequency on seedling recruitment remain largely unknown. An understanding of the effects of precipitation amount and frequency and their interaction on seedling emergence and growth of typical desert plants is vital for managing populations of desert plants. We conducted two experiments to study the effects of variation in precipitation on Reaumuria soongarica (Pall.) Maxim. First, greenhouse experiments were conducted to examine the effects of three precipitation amount treatments (ambient, +30%, and –30%) and two precipitation frequency treatments (ambient and –50%) on seedling emergence. Second, the morphological responses of R. soongarica to changes in precipitation amount and frequency were tested in a controlled field experiment. Stage-specific changes in growth were monitored by sampling in different growth seasons. Our results showed that precipitation amount significantly affected germination, seedling emergence, and growth of R. soongarica, and there was a larger effect with decreased precipitation frequency compared with ambient. Germination and seedling emergence increased as precipitation increased under the same frequency of precipitation. The highest emergence percentage was obtained with a 30% increase in precipitation amount and a 50% reduction in precipitation frequency. Compared with ambient precipitation, a 30% increase in precipitation amount increased above- and below-ground biomass accumulation of R. soongarica during the growth season. A decrease of 30% in precipitation amount also resulted in an increase in below-ground biomass and root/shoot ratio in the early stages of the growth season, however, above- and below-ground biomass showed the opposite results at the end of the growth season, with larger effects on above-ground than below-ground biomass under decreased precipitation frequency. When precipitation frequency decreased by 50%, values of all growth traits increased for a given amount of precipitation. We concluded that precipitation frequency may be as important as precipitation amount to seedling emergence and growth of R. soongarica, and that understanding the effects of precipitation variability on seedling recruitment requires the integration of both precipitation amount and frequency. In particular, the combination of a 30% increase in precipitation amount and 50% reduction in precipitation frequency increased the emergence and growth of seedlings, suggesting that alteration of amount and frequency of precipitation caused by climate change may have significant effects on seedling recruitment of R. soongarica.

Thermal infrared remote sensing technology based on unmanned aerial vehicle (UAV) was applied to estimate the spatial distribution of ground surface temperatures on permafrost slopes and evaluate the thermal influence of nearby engineering infrastructure. This paper presents a method that uses a miniature UAV with a thermal infrared sensor to collect thermal images with high temporal–spatial resolution. Moreover, spatial analysis is used to effectively evaluate the relationship between engineering infrastructure and permafrost slopes in the Qinghai–Tibet Engineering Corridor (QTEC), China. To test the method, aerial measurements were collected from 11:00 to 17:00 in July and August of 2017 at two permafrost slopes along the QTEC, where the Qinghai–Tibet Highway (QTH), Qinghai–Tibet Railway (QTR), and electric towers were built on permafrost slopes. The differences of ground surface temperature between the highway and the surrounding soil were largest at 11:00 and 17:00; the differences were smaller at noon to approximately 15:00 when the difference was minimal, and the differences began to increase after 15:00. The distances of the thermal influence of the highway, railway, and electric towers on the surrounding permafrost slopes are approximately 12–14, 8–10, and 2–4 m, respectively. The results indicate that the degree of influence of engineering structures on permafrost slopes is as follows: QTH > QTR > electric towers. This study is the first to use UAV-based thermal infrared remote sensing to evaluate the thermal dynamics of permafrost slopes along the QTEC. These results may provide new insights into the future design, construction, and maintenance of engineering structures on permafrost slopes.

Ultraviolet (UV) radiation has significant effects on ecosystems, environments, and human health, as well as atmospheric processes and climate change. Two ultraviolet radiation datasets are described in this paper. One contains hourly observations of UV radiation measured at 40 Chinese Ecosystem Research Network stations from 2005 to 2015. CUV3 broadband radiometers were used to observe the UV radiation, with an accuracy of 5%, which meets the World Meteorology Organization's measurement standards. The extremum method was used to control the quality of the measured datasets. The other dataset contains daily cumulative UV radiation estimates that were calculated using an all-sky estimation model combined with a hybrid model. The reconstructed daily UV radiation data span from 1961 to 2014. The mean absolute bias error and root-mean-square error are smaller than 30% at most stations, and most of the mean bias error values are negative, which indicates underestimation of the UV radiation intensity. These datasets can improve our basic knowledge of the spatial and temporal variations in UV radiation. Additionally, these datasets can be used in studies of potential ozone formation and atmospheric oxidation, as well as simulations of ecological processes.

Our results showed that in addition to sodium (Na+), succulent xerophyte Haloxylon ammodendron was more inclined to absorb and accumulate large amount of calcium (Ca2+) than potassium (K+) as an important osmotica for osmotic adjustment (OA) under arid environments. To further reveal the possible physiological mechanisms of Ca2+ accumulation involved in drought resistance of H. ammodendron, 8-week-old plants were treated with a series concentration of external Ca2+ (calcium chloride, 1 × 10−4 to 8 × 10−4 g CaCl2 g−1 dry soil) by potted sandy soil culture experiments in field. Plants were also subjected to water deficit (30% of field water capacity) in the presence or absence of Ca2+ (4 × 10−4 g CaCl2 g−1dry soil) by potted sand culture experiments in greenhouse. The results showed that 4 × 10−4 g CaCl2 g−1 soil resulted in optimal plant growth and effectively mitigated harmful impacts of water deficit on the growth of H. ammodendron, by inducing a significant drop in PB water potential and, concomitantly, increasing PB turgor pressure and chlorophyll concentration resulting in an enhancement of overall plant photosynthetic activity. Furthermore, 4 × 10−4 g CaCl2 g−1 soil had no effects on the photosystem II photochemistry, but mitigated the inhibitory effect of water deficit on the activity of photosystem II in H. ammodendron. The contribution of Ca2+ to the total osmotic potential varied from 6.2% in the control to 11.4% in plants subjected to water deficit and, surprisingly, to 21.6% in plants grown in the presence of 4 × 10−4 g CaCl2 g−1 soil under water deficit; however, the contribution of K+ significantly decreased from 12.1 to 7.0%. These findings suggest that, under arid environments, H. ammodendron is able to accumulate high concentration of Ca2+ in its PB and use it directly for OA, which was coupled with an improvement in PB hydration and photosynthetic activity.

In arid and semiarid ecosystems, shrubs usually play an important role in determining vegetation pattern and landscape diversity. By exerting multiple effects on microhabitat, shrubs can modulate the performances, species assemblages, and spatial patterns of their understory plants. Both positive and negative interactions act simultaneously, and the balance between them shifts at different spatial locations. To better understand shrub–herb interaction and its possible mechanisms, we chose three common shrub species in a dry-land of Hexi desert region and examine their effects on microhabitat and understory vegetation among different locations. Results showed that the understory vegetation can benefit from the presence of Calligonum mongolicum, as a result of modified drought stresses, increased soil nutrients and more available seeds. However, understory vegetation exhibited better performances at the peripheral location of Nitraria sphaerocarpa patches, which can be explained by the balance between resources improvement and seeds limitation. It has been also found that the higher salt contents (e.g., Na+, K+, Cl−, and SO4 2−) on vegetation patches beneath Haloxylon ammodendron may interfere with herbaceous performances and thus modified their spatial pattern. Our study revealed that the multiple effects of shrubs on microhabitat are species specific and at a fine scale, which may result in various fine-scale spatial patterns of vegetation in response to different shrub species.

A better understanding of the sap flow characteristics of maize plants is critical for improving irrigation water-use efficiency, especially for regions facing water resource shortages. In this study, sap flow rates, related soil-physics and plant-growth parameters, and meteorological factors, were simultaneously monitored in a maize field in two consecutive years, 2011 and 2012, and the sap flow rates of the maize plants were extensively analyzed based on the monitored data. Seasonal and daily variational characteristics were identified at different growth stages and under different weather conditions, respectively. The analyses on the relationships between sap flow rate and reference evapotranspiration (ET0), as well as several plant-growth parameters, indicate that the irrigation schedule can exert an influence on sap flow, and can consequently affect crop yield. The ranking of the main meteorological factors affecting the sap flow rate was: net radiation > air temperature > vapor pressure deficit > wind speed. For a quick estimation of sap flow rates, an empirical formula based on the two top influencing factors was put forward and verified to be reliable. The sap flow rate appeared to show little response to irrigation when the water content was relatively high, implying that some of the irrigation in recent years may have been wasted. These results may help to reveal the bio-physical processes of maize plants related to plant transpiration, which could be beneficial for establishing an efficient irrigation management system in this region and also for providing a reference for other maize-planting regions.

The transpiration rate of plant is physically controlled by the magnitude of the vapor pressure deficit (VPD) and stomatal conductance. A limited-transpiration trait has been reported for many crop species in different environments, including Maize (Zea mays L.). This trait results in restricted transpiration rate under high VPD, and can potentially conserve soil water and thus decrease soil water deficit. However, such a restriction on transpiration rate has never been explored in maize under arid climatic conditions in northwestern China. The objective of this study was to examine the transpiration rate of field-grown maize under well-watered conditions in an arid area at both leaf and whole plant levels, and therefore to investigate how transpiration rate responding to the ambient VPD at different spatial and temporal scales. The transpiration rates of maize at leaf and plant scales were measured independently using a gas exchange system and sapflow instrument, respectively. Results showed significant variations in transpiration responses of maize to VPD among different spatio-temporal scales. A two-phase transpiration response was observed at leaf level with a threshold of 3.5 kPa while at the whole plant level, the daytime transpiration rate was positively associated with VPD across all measurement data, as was nighttime transpiration response to VPD at both leaf and whole plant level, which showed no definable threshold vapor pressure deficit, above which transpiration rate was restricted. With regard to temporal scale, transpiration was most responsive to VPD at a daily scale, moderately responsive at a half-hourly scale, and least responsive at an instantaneous scale. A similar breakpoint (about 3.0 kPa) in response of the instantaneous leaf stomatal conductance and hourly canopy bulk conductance to VPD were also observed. At a daily scale, the maximum canopy bulk conductance occurred at a VPD about 1.7 kPa. Generally, the responsiveness of stomatal conductance to VPD at the canopy scale was lower than that at leaf scale. These results indicate a temporal and spatial heterogeneity in how maize transpiration responses to VPD under arid climatic conditions. This could allow a better assessment of the possible benefits of using the maximum transpiration trait to improve maize drought tolerance in arid environment, and allow a better prediction of plant transpiration which underpin empirical models for stomatal conductance at different spatio-temporal scales in the arid climatic conditions.

It is important to understand the effects of dew events on non-mucilaginous seed germination of annual desert plant species during dry seasons, which is critical to maintaining long-term soil seed banks in a harsh desert environment. We hypothesize that dew deposition also assists in the non-mucilaginous seed germination of annual desert species. A common field dew treatment experiment was conducted in the Linze Inland River Basin Research Station to investigate the effects of dew deposition on the seed germination of four annual species, including Agriophyllum squarrosum, Corispermum mongolicum, Bassia dasyphylla and Halogeton arachnoideus. The results showed that the presence of dew significantly increased seed germination percentages and decreased the nonviable seed percentages of B. dasyphylla and H. arachnoideus, whereas there was no such trend for the seeds of C. mongolicum and A. squarrosum. The ecological effects of dew on the seed germination and viability of the annual desert plants were species specific. Although dew wetting is insufficient to cause seed germination, it may help in priming the seeds.

Picea crassifolia Kom, a perennial arbor species is recognized as one of the most adaptable plants found to date in Qilian Mountains. To explore the cutting reproduction technology of P. crassifolia and reveal its rooting mechanism, cuttings of P. crassifolia with different cutting types (softwood, hardwood and root), positions (top, upper, middle and bottom) and ages (7, 10, 15, 20, 25 year-old) were cultivated in a field experiment. One-year old softwood and hardwood cuttings were collected from 7-, 10-, 15-, 20-, and 25 year-old healthy ortets to analyze the changes from endogenous hormones and organic nutrients. Results indicate that the softwood cuttings (0.5–1.0 cm in diameter) from upper branches of 15 year-old ortets shows better growth performance by improving rooting indexes, including a significant increase in rooting rate and a decrease in basal rot rate. Concomitantly, increasing rooting quantity and root length also increased. It is noteworthy that the high rooting rate of P. crassifolia cuttings due to its ability to accumulate high concentrations of indole-3-acetic acid (IAA) and total carbon (TC) rather than abscisic acid (ABA) and total nitrogen (TN). The rooting rate was mainly regulated by the IAA/ABA and TC/TN ratio. In summary, our results suggest that the softwood cuttings (0.5–1.0 cm in diameter) from upper branches of 15 year-old P. crassifolia can be considered as an effective strategy to improve cutting rooting rate, and the IAA/ABA and TC/TN ratio was one of the main factors limiting the cutting rooting rate of P. crassifolia.

Eight groundwater observation wells were installed along the river plain, where the landscapes varied from floodplain, to oasis farmland, to desert-oasis ecotone to desert, in a typical desert-oasis ecotone in northwestern China. Ten years of data were used to analyze temporal and spatial changes in the groundwater depth. The results indicated that in the last decade: (1) the groundwater depths in the floodplain (GW1) and the desert (GW8) were basically stable; (2) the groundwater depths in the oasis farmland (GW2, GW3, GW4) increased dramatically: the annual fluctuations were 1.43, 1.01 and 0.79 m respectively, with the groundwater depths increasing by 0.13–0.18 m every year; (3) the groundwater depths in the desert-oasis ecotone (GW5, GW6, GW7) also increased dramatically: the annual fluctuations were 1.10, 1.06 and 1.05 m respectively, and the depths increased by 0.10–0.15 m every year; (4) the influence distance between the river and both the farmland and the desert-oasis ecotone was about 1000–2000 m in the study area. These results show that the natural seasonal fluctuation influence on groundwater depths was not significant, but the human-induced fluctuations such as intensive irrigation caused a significant increase in groundwater depth in both the farmland and the desert-oasis ecotone, seriously affecting sustainable agriculture development and the environment, in the oasis.

A pot trial was conducted to investigate the effect of Na (as sodium chloride, NaCl), and Na and Si (as sodium metasilicate nonahydrate, Na2SiO3·9H2O) coexistence (NaCl + Na2SiO3) on the growth of the succulent xerophyte Nitraria tangutorum under drought (30 % of field water capacity) in pot culture experiment. The results indicate that 1.2 g kg−1 NaCl, and the coexistence of 0.3 g kg−1 NaCl + 0.72 g kg−1 Na2SiO3 can effectively promote the growth, and the coexistence can more effectively strengthen the growth of N. tangutorum than the 1.2 g kg−1 NaCl. The coexistence encourages plant height, root/shoot, biomass and main root length and, concomitantly, accumulating a higher concentration of Na+ (shoots) and Si (SiO2) (roots) than K+ to adapt to arid environment. In comparison with the 1.2 g kg−1 NaCl, a significant increase of Na+ in shoots by 11.9 % and Si in shoots and roots by 173.1 and 191.8 %, respectively were observed in the coexistence of 0.3 g kg−1 NaCl + 0.72 g kg−1 Na2SiO3. These findings suggest that the positive roles of Na and Si coexistence on the growth of N. tangutorum under drought might be due to the ability to accumulate a high concentration of Na+ as an important physiological osmoregulator, while still absorbing and accumulating a large amount of Si (SiO2) to stimulate growth under drought.

The influences of previous-year precipitation and episodic rainfall events on dryland plants and communities are poorly quantified in the temperate desert region of Northwest China. To evaluate the thresholds and lags in the response of aboveground net primary productivity (ANPP) to variability in rainfall pulses and seasonal precipitation along the precipitation-productivity gradient in three desert ecosystems with different precipitation regimes, we collected precipitation data from 2000 to 2012 in Shandan (SD), Linze (LZ) and Jiuquan (JQ) in northwestern China. Further, we extracted the corresponding MODIS Normalized Difference Vegetation Index (NDVI, a proxy for ANPP) datasets at 250 m spatial resolution. We then evaluated different desert ecosystems responses using statistical analysis, and a threshold-delay model (TDM). TDM is an integrative framework for analysis of plant growth, precipitation thresholds, and plant functional type strategies that capture the nonlinear nature of plant responses to rainfall pulses. Our results showed that: (1) the growing season NDVIINT (INT stands for time-integrated) was largely correlated with the warm season (spring/summer) at our mildly-arid desert ecosystem (SD). The arid ecosystem (LZ) exhibited a different response, and the growing season NDVIINT depended highly on the previous year's fall/winter precipitation and ANPP. At the extremely arid site (JQ), the variability of growing season NDVIINT was equally correlated with the cool- and warm-season precipitation; (2) some parameters of threshold-delay differed among the three sites: while the response of NDVI to rainfall pulses began at about 5 mm for all the sites, the maximum thresholds in SD, LZ, and JQ were about 55, 35 and 30 mm respectively, increasing with an increase in mean annual precipitation. By and large, more previous year's fall/winter precipitation, and large rainfall events, significantly enhanced the growth of desert vegetation, and desert ecosystems should be much more adaptive under likely future scenarios of increasing fall/winter precipitation and large rainfall events. These results highlight the inherent complexity in predicting how desert ecosystems will respond to future fluctuations in precipitation.

The authors describe a novel method for the determination of glutathione (GSH). Detection is based on target induced release of glucose from MnO2 nanosheet-gated aminated mesoporous silica nanoparticles (MSNs). In detail, glucose is loaded into the pores of MSNs. Negatively charged MnO2 nanosheets are assembled on the MSNs through electrostatic interactions. The nanosheets are reduced by GSH, and this results in the release of glucose which is quantified by using a commercial electrochemical glucose meter. GSH can be quantified by this method in the 100 nM to 10 μM concentration range, with a 34 nM limit of detection.

Clonal integration in rhizomatous and stoloniferous clonal plants has been studied for many years, but the mechanisms of clonal integration of root-derived plants remain largely unknown. Alhagi sparsifolia is a typical root-derived clonal plant in the extremely dry land of the Taklamakan desert, and it usually cannot reproduce sexually in natural and non-irrigated environments; clonal reproduction is the primary way for this plant to maintain and extend its populations. After determining that A. sparsifolia clonally integrates its ramets, we tested whether that capability could enhance the species’ survival in dry conditions, using both a spacer-severed group and a control spacer-connected group, by applying both supplementary water and 13C labeling to mother ramets and old daughter ramets. Our results showed that the midday water potential of both mother and daughter ramets increased significantly after spacer severance. The water potential of the mothers significantly increased after water supplementation, under both the spacer-severed and spacer-connected treatments. The water potential of daughter ramets in the spacer-connected treatment group also increased significantly, but that of the spacer-severed treatment group did not. Leaf relative water content and increases in height, crown width, number of branches, and basal diameter of the daughter ramets in the spacer-connected group were significantly higher than those in the spacer-severed group. δ13C values of mother (and of old daughter) ramets significantly increased after 13C labeling, but δ13C values of neither mother, old daughter nor young daughter ramets changed. We concluded that clonal integration of water takes place between mother and daughter ramets of A. sparsifolia and that the mother can transfer water to daughter ramets through the spacers, but that no clonal integration of photosynthates occurs among the ramets of A. sparsifolia. These results have important implications for vegetation restoration and the utilization of water resources in this area.

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.

Stress gradient hypothesis predicted that facilitative interactions usually increase in intensity and are importance with abiotic stress. By contrast, facilitation may be lost in time, when it involves the growth of benefactors or beneficiaries. Less is known about which response pattern is more common in arid desert. We present an empirical study to explore shrub-annual interactions at the community and individual level along the course of a single growing season in a desert steppe in northwest China. Here the severity of drought stress may increase in time due to uneven precipitation during plant growing season. We assessed growth responses of annuals in understory where two dominant shrubs were removed. Annuals responses showed a switch from weakly positive to more strongly positive beneath Calligonum mongolicum, whereas from positive to negative beneath Nitraria sphaerocarpa during the growing season. Additionally, annual species with contrasting functional traits showed distinct growth responses to canopies removal. There was evidence of an increase in soil moisture below the canopy of shrubs, but a decrease in potential evaporation rate and photosynthetically active radiation, which can partly explain these species-specific responses. We conclude that the balance between competitive and facilitative effects in shrub-annual interactions is not only governed by the severity of stress but also determined by plant traits, such as canopy structure of shrubs and functional traits of their understory annuals.

In the arid inland river basins of northwestern China, human activities control almost all the surface hydrologic processes. The potential effects of these altered hydrologic processes are gradually becoming clear, especially since the 2000 implementation of the integrated water resources management projects in the Shiyang River, the Heihe River, the Tarim River, and the Shuler River. While the appearance of these eco-hydrology changes and consequent environmental effects in the oasis has attracted broad attention, related research is still lacking. Eco-hydrological process changes in the desert-oasis ecotone were investigated in the Pingchuan irrigation district in the middle reaches of the Heihe River. The results showed that the annual average amount of surface water irrigation during the past 20 years has decreased by 1.498×107 m3, while the annual average amount of well irrigation has increased by 1.457×107 m3, since 2000, when the State Council of China approved the water diversion scheme for the Heihe River Basin. The groundwater depth before the water diversion scheme generally varied between 2.44–3.19 m (average 2.73±0.24 m), while that after the water diversion scheme has varied between 3.08–4.01 m (average 3.79±0.62 m). The distribution area of 3 m groundwater depth increased from 853 to 3843 hm2. However, although the hydrologic processes changed dramatically, no significant effects on vegetation productivity in the desert-oasis ecotone were detected during the study period.

Water balance and migration characteristics are vital to the establishment of an efficient irrigation management system. Based on the observed data including microclimate and growing parameters of maize from 2009 to 2012, actual evapotranspiration during the growth period was estimated by a combination of the FAO-56 crop coefficient approach and the Penman–Monteith model; the changes in soil water storage were estimated through the monitored water content at different depths from 0 to 3 m; the water content monitoring zone was divided into three sub-zones according to the water-balance characteristics of different soil layers and water monitoring data. On these bases, in combination of water-balance model, three aspects were analyzed: water-balance characteristics at different growth stages; water-balance characteristics in the three different sub-zones; and water-migration characteristics of ten sunny days following irrigation. These analyses revealed severe deep leakage under present irrigation management, which could be remedied by limiting one-time irrigation practices and increasing irrigation frequency. Additionally, some practical suggestions are provided for different growing stages.

The oasis area in the middle reaches of the Heihe River has changed since a water diversion scheme was implemented in 2000. The resultant variation land surface characteristics affects radiation budget during the oasisification process. The aim of this study was to investigate the variation in radiation budget within land surfaces during the oasisification process, through spatial instead of time-successional sequence method. Radiant data in the oasis fringe (maize field) and the desert-oasis ecotone was observed during the summer of 2009. The results showed that solar radiation (SR) in the oasis fringe was identical to that of the desert-oasis ecotone on selected clear, cloudy, and rainy days. Surface reflective radiation (SRR) and surface effective radiation (SER) both decreased from clear day to cloudy day and were lowest on the rainy day. The diurnal variation in radiation budget for cloudy and rainy days did not follow the same cycle as on clear day. The albedo values in the oasis fringe and the desert-oasis ecotone were 0.18 and 0.26, respectively. The diurnal variation in albedo tended toward a “U-shaped” curve on clear day. When the solar elevation angle was greater than 40°; the albedo was symmetrical in the a.m. and p.m. time frames. The radiation budget changed within land surfaces during the oasisification process. In summer, the albedo decreased, as did SER, with the transition from desert to oasis interior; whereas the surface-absorbed radiation (SAR) and net radiation (NR) both increased. More than half of the absorbed net energy in the desert was released in longwave form. The absorbed energy in the oasis was conserved to ensure stable light and heat resources utilization for agricultural production.

As a main component in water balance, evapotranspiration is of great importance for water saving and irrigation-measure making, especially in arid or semiarid regions. Although studies of evapotranspiration have been conducted for a long time, studies concentrated on oasis-desert transition zone are very limited. On the basis of the meteorological data and other parameters (e.g. leaf area index (LAI)) of an oasis-desert transition zone in the mid- dle stream of Heihe River from 2005 to 2011, this paper calculated both reference (ET0) and actual evapotranspira- tion (ETc) using FAO56 Penman-Monteith and Penman-Monteith models, respectively. In combination with pan evaporation (Ep) measured by E601 pan evaporator, four aspects were analyzed: (1) ET0 was firstly verified by Ep; (2) Characteristics of ET0 and ETc were compared, while the influencing factors were also analyzed; (3) Since me- teorological data are often unavailable for estimating ET0 through FAO56 Penman-Monteith model in this region, pan evaporation coefficient (Kp) is very important when using observed Ep to predict ET0. Under this circumstance, an empirical formula of Kp was put forward for this region; (4) Crop coefficient (Kc), an important index to reflect evapotranspiration, was also analyzed. Results show that mean annual values of ET0 and ETc were 840 and 221 mm, respectively. On the daily bases, ET0 and ETc were 2.3 and 0.6 mm/d, respectively. The annual tendency of ET0 and ETc was very similar, but their amplitude was obviously different. The differences among ET0 and ETc were mainly attributed to the different meteorological variables and leaf area index. The calculated Kc was about 0.25 and showed little variation during the growing season, indicating that available water (e.g. precipitation and irrigation) of about 221 mm/a was required to keep the water balance in this region. The results provide an comprehensive analysis of evapotranspiration for an oasis-desert transition zone in the middle stream of Heihe River, which was seldom reported before.

Soil moisture and its variations are key factors for understanding hydrological processes, which are characterized by a high temporal variability at different scales. The study was conducted at three field stations in the desert regions of northwestern China, where soil moisture measurements with gravimetric method were used to characterize the temporal stability of soil moisture using various statistical parameters and an index of temporal stability (ITS). The soils are a gray–brown desert soil at the Linze station, an aeolian sandy soil at the Fukang station, and a brown desert soil at the Cele station. Soil textures are accordingly sandy loam at Linze and Cele, and loamy sand at Fukang. The dynamic variation in soil moisture depends strongly on the rainfall pattern (amount and frequency) in these desert ecosystems. Soil moisture content is low and significantly different among the three desert ecosystems, with the maximum at the Linze station (6.61 ± 2.08 %), followed by the Cele (4.83 ± 0.81 %) and Fukang (3.46 ± 0.47 %) stations. The temporal pattern exhibits high variability because soil moisture is characterized by low temporal stability and a high coefficient of variation (CV). The standard deviation, CV, and ITS increase significantly with increasing soil moisture. Soil moisture displays a skewed frequency distribution that follows a logarithmic function at lower soil moisture but a log-normal distribution at higher values.

Well Lundong-1 is located in the periclinal area on the eastern flank of the Tahe-Lunnan paleo-uplift in the Tarim Basin. A 25-m-high cave fill sequence was observed in the Upper Ordovician interval of the well at 6800–6825 m. A third cut of cores was obtained from the top of the cave. The following conclusions were obtained by studying the cave sediments and depositional sequence, and by undertaking paleontological and elemental geochemistry analyses. 1. The cave sediments contain abundant brachiopod, gastropod, echinoderm, ostracod, and acritach fossils, which can be classified into two groups: cave autochthonous and cave allochthonous fossils (from collapse breccia dissolution or transportation by underflow). The fossils indicate that the cave was formed before the Carboniferous and partly-filled and buried during Carboniferous resubsidence. 2. Elemental geochemistry shows that the mud that filled the cave is sourced from calcareous paleo-soil and weathered crust that came from a salty environment with poor water circulation. 3. The formation and evolution of the cave occurred in three stages. The first stage occurred after the deposition of the Late Ordovician Lianglitage Formation, the second stage took place after the deposition of the Late Ordovician Sangtamu Formation, and the last stage happened after Silurian deposition. Major dissolution occurred in the latter two stages as a result of bedding-confined deep underflow karstification. Based on the reconstruction of the cave formation history, favorable paleokarst targets can be predicted and estimated to aid paleogeography and paleokarstology studies.

Little is known about preferential flow and its effects on vegetation under natural conditions in an arid oasis ecotone. In this study, we performed dye-tracer experiments using 5, 15, 35, and 55 mm water-sprinkling treatments at three sites: Grass (G), Haloxylon (H), and Populus (P). At each site, we determined soil texture and saturated hydraulic conductivity of the soil (K s) and water flow parameters; we also defined characteristics of soil fracturing and measured plant biomass at site P. The tracer experiments revealed that the three sites displayed significant differences in the degree of preferential flow. Soil structure and surface characteristics were the primary controlling factors, however, they played a different role in different rainfall events. For small rainfall events, soil surface characteristics controlled the preferential flow pattern; for large or extreme rainfall events, soil structure was the critical factor. The effects of different rainfall events were complex and strongly varied among sites. Our results further indicated that preferential flow could impact the growth of annual plants. We conclude that preferential flow in an arid oasis ecotone is a common phenomenon affected by complex factors, and it may be important in soil water distribution and plant growth.

Fluxes of carbon dioxide, water vapor, and heat were measured above crop canopy using the eddy covariance method during the 2008 maize growing season, over an agricultural field within an oasis located in the middle reaches of Heihe River basin, northwest China. The values for friction velocity, the Monin–Obukhov stability parameter, and energy balance closure indicated that the eddy covariance system at this study site provided reliable flux estimates. Results from measurements showed that the mean sensible heat flux was 70 W m−2 with a maximum value of 164 W m−2 (May) and a minimum value of 45 W m−2 (July) during the maize growing season. In contrast, the mean latent heat was 278 W m−2 with a maximum value of 383 W m−2 (July) and minimum of 101 W m−2 (May). The mean downward soil heat flux was 55 W m−2 with a maximum value of 127 W m−2 (May) and minimum of 49 W m−2 (July). The magnitude of mean daytime net CO2 uptake was −11.50 μmol m−2 s−1 with a maximum value of −28.32 μmol m−2 s−1 (18 and 19 July) and a minimum values of −0.32 μmol m−2 s−1 (18 and 19 May). Correlation was observed between daytime half-hourly carbon dioxide flux and canopy conductance. In addition, the relationship between carbon dioxide flux and photosynthetically active radiation for selected days during different stages of maize growing season indicated the carbon dioxide flux uptake by the canopy was controlled by actual photosynthetic activity related to the variation of green leaf area index for the different growing stages.

Monitoring of drinking water has shown an increase in nitrate-nitrogen (NO 3 − -N) concentration in groundwater in some areas of the Heihe River Basin, Northwest China. A combination of careful irrigation and nitrogen (N) management is needed to improve N uptake efficiency and to minimize fertilizer N loss. A 2-year experiment investigated the effects of different irrigation and N application rates on soil NO 3 − -N distribution and fertilizer N loss, wheat grain yield and N uptake on recently reclaimed sandy farmland. The experiment followed a completely randomized split-plot design, taking flood irrigation (0.6, 0.8 and 1.0 of the estimated evapotranspiration) as main plot treatment and N-supply as split-plot treatment (with five levels of 0, 79, 140, 221, 300 kg N ha−1). Fertilizer N loss was calculated according to N balance equation. Our results showed that, under deficit irrigation conditions, N fertilizer application at a rate of 300 kg ha−1 promoted NO 3 − -N concentration in 0–200 cm depth soil profiles, and treatments with 221 kg N ha−1 also increased soil NO 3 − -N concentrations only in the surface layers. Fertilizer N rates of 70 and 140 kg ha−1 did not increase NO 3 − -N concentration in the 0–200 cm soil profile remaining after the spring wheat growing season. The amount of residual NO 3 − -N in soil profiles decreased with the amount of irrigation. Compared with N0, the increases of fertilizer N loss, in N79, N140, N221 and N300 respectively, were 59.9, 104.6, 143.5 and 210.6 kg ha−1 over 2 years. Under these experimental conditions, a N rate of 221 kg ha−1 obtained the highest values of grain yield (2775 kg ha−1), above-ground dry matter (5310 kg ha−1) and plant N uptake (103.8 kg ha−1) over 2 years. The results clearly showed that the relative high grain yield and irrigation water productivity, and relative low N loss were achieved with application of 221 kg N ha−1 and low irrigation, the recommendation should be for those farmers who use the upper range of the recommended 150–400 kg N ha−1, that they can save about 45% of their N and 40% of their irrigation water application.

Some large-scale oil-gas fields have recently been discovered in marine carbonate in China, especially the significant discoveries in deep reservoir that reveals a favorable exploration prospect. Tazhong area is the first-order tectonic unit in Tarim Basin, where there are nearly trillion cubic meters of natural gas resources in the Ordovician limestone reef flat complex in Lianglitage Formation. The reservoir is shelf edge reef flat complex, characterized by ultra-low porosity, low permeability and strong heterogeneous, with a current burial depth of 4500–6500 m. Studies find that the formation and distribution of deep reservoir of the Lianglitage Formation were controlled not only by the early high-energy sedimentary facies and corrosion, but the fracture network formed by the strong gas-charging process since the Himalayan epoch, which played an important role in optimizing and improving reservoir properties. This paper discusses the relationship between the strong later gas-charging and the improvement of the reservoir capacity in deep Ordovician carbonate reservoir, and also builts the corresponding mechanisms and modes, which is favorable for the prediction and evaluation of the advantageous exploration targets.

This research was conducted to determine the water requirements of oasis ecosystem with crop evapotranspiration method, and to analyse the water balance between the supply and requirement using water balance model, and then assess the stability of oasis ecosystem in the middle of Heihe River basin, China. The results indicated that the summations of the water supply and requirement approximated to 82.54 and 110.13 Mm3 years−1 in 2007, and the water deficit was 27.59 Mm3 years−1. The farmland was the largest water consumer with a consumption of 57.07 Mm3 years−1 and accounted for 51.82% of the total water requirements. It was followed by the water area 38.83 Mm3 years−1, forestland 12.13 Mm3 years−1 and domestic and industrial 2.10 Mm3 years−1, and accounted for 35.26, 11.01 and 1.92%, respectively. The stability index was 0.74, which implies that the oasis ecosystem have already started degenerating in sub-stability state. However, the water requirement of unit area was 1243.70 mm years−1 and larger than other oases in arid region of China, which implies that the water resource scarcity do not exist in the middle basin where the excessive waste of the flood irrigation method has broken the balance between the water supply and requirement in the basin scale.

A field study was conducted in a semi-arid sand land ecosystem in eastern Inner Mongolia, China, to explore the mechanisms underlying how human-induced environmental degradation in sandy grasslands influences ecosystem plant diversity, productivity, soil erodibility, and soil carbon (C), nitrogen (N) and phosphorus (P) accumulation and storage. We investigated (1) C, N and P accumulation to 20cm soil depth; (2) C, N and P storage in plant litter, above- and below-ground biomass; and (3) the rate of surface wind erosion measured as the amount of aeolian soil accumulating in the traps and C, N and P output from the topsoil removal due to wind erosion during the erosive season in four habitats of differently degraded sandy grasslands. Environmental degradation has resulted in significant and differential reductions in soil C, N and P accumulation within the top 20cm soil layer across habitats. On average, the most severely degraded sandy grassland stored 474%, 198% and 56% less soil C, N and P, while the severely degraded sandy grassland stored 215%, 121% and 27% less soil C, N and P and the moderately degraded sandy grassland stored 111%, 60% and 17% less soil C, N and P than did the lightly degraded sandy grassland. Two key variables associated with reduced soil C, N and P accumulation in sandy grasslands as a result of environmental degradation are reduced plant litter and above- and below-ground biomass production (i.e. less plant C, N and P inputs in the soil) and increased C, N and P output from the removal of nutrient-rich topsoil layers resulted from increased rates of wind erosion. This study suggests a complex mechanism by which environmental degradation influences soil C, N and P accumulation and dynamics via its significant effects on ecosystem plant diversity, productivity and soil erodibility.

There are mainly 3 kinds of existing states of oil generating from source rocks, that is, dispersive liquid hydrocarbon inside of source rock, dispersive liquid hydrocarbon outside of source rock and concentrated liquid hydrocarbon outside of source rock. Because of the differences in thermal history and medium conditions around, and the interaction of organic and inorganic matter, the liquid hydrocarbon with 3 kinds of existing state has different cracking conditions. The gas generation dynamics experiments of crude oil matching different mediums indicate that the distribution of activation energy of methane changes a lot according to medium difference. The carbonate has a main influence on oil cracking conditions and can largely reduce its activation energy, which reflects the lower cracking temperature of crude oil. The mudstone takes a second place and the sandstone is the smallest. The catalytic cracking function to the oil of the carbonate, of the mudstone and of the sandstone changes weaken in turn. The corresponding Ro values of main gas generation period in different mediums are as follows: 1.5%–3.8% with pure crude oil, 1.2%–3.2% with dispersive crude oil in carbonate, 1.3%∼3.4% with dispersive crude oil in mudstone and 1.4%–3.6% with dispersive crude oil in sandstone. The influence of pressure to crude oil cracking is relatively complicated. In the low heating speed condition, pressure restrains the oil cracking and gas generation, but in the high heating speed condition, pressure has an indistinctive influence to the oil cracking and gas generation. Pressure also makes a different effort in different evolvement stage. Taking the middle and lower Cambrian source rocks in the Tarim Basin as an example, primary oil generating quantity is 2232.24×108t, residual oil and oil cracking gas quantity is 806.21×108t and 106.95×1012m3 respectively.

Shallow gas reservoirs are distributed widely in Chinese heavy oil-bearing basins. At present, shallow gas resources have opened up giant potentials. The previous researches indicate the intimate genetic relationship between shallow gas and heavy oil. Shallow gas resources are generated from crude oil degraded by anaerobic microscopic organism, it belongs to biogenic gas family of secondary genesis, namely heavy oil degraded gas. Shallow gas resources are usually distributed in the upward position or the vicinity of heavy oil reservoirs. They are mainly of dry gas, which are composed of methane and only tiny C2+ heavy hydrocarbon and relatively higher contents of nitrogen gas. Generally, methane isotopes are light, whose values are between biogenic gas and thermal cracking gas. Ethane isotopes are heavy, which mixed possibly with thermogenic gas. Carbon dioxide bear the characteristics of very heavy carbon isotope, so carbon isotopic fractionation effects are very obvious on the process of microscopic organism degradation crude oil. The heavy oil degraded gas formation, a very complex geological, geochemical and microbiological geochemical process, is the result of a series of reactions of organic matter-microbes and water-hydrocarbon, which is controlled by many factors.

Stochastic modeling of soil moisture dynamics is crucial to the quantitative understanding of plant responses to water stresses, hydrological control of nutrient cycling processes, water competition among plants, and some other ecological dynamics, and thus has become a hotspot in ecohydrology at present. In this paper, we based on the continuously monitored data of soil moisture during 2002–2005 and daily precipitation date of 1992–2006, and tried to make a probabilistic analysis of soil moisture dynamics at point scale in a grassland of Qilian Mountain by integrating the stochastic model improved by Laio and the Monte Carlo method. The results show that the inter-annual variations for the soil moisture patterns at different depths are very significant, and that the coefficient of variance (CV) of surface soil moisture (20 cm) is almost continually kept at about 0.23 whether in the rich or poor rainy years. Interestingly, it has been found that the maximal CV of soil moisture has not always appeared at the surface layer. Comparison of the analytically derived soil moisture probability density function (PDF) with the statistical distribution of the observed soil moisture data suggests that the stochastic model can reasonably describe and predict the soil moisture dynamics of the grassland in Qilian Mountain at point scale. By extracting the statistical information of the historical precipitation data in 1994–2006, and inputting them into the stochastic model, we analytically derived the long-term soil moisture PDF without considering the inter-annual climate fluctuations, and then numerically derived the one when considering the inter-annual fluctuation effects in combination with a Monte-Carlo procedure. It was found that, though the peak position of the probability density distribution significantly moved towards drought when considering the disturbance forces, and its width was narrowed, accordingly its peak value was increased, no significant bimodality was observed in the soil moisture dynamics under the given intensity of random fluctuation disturbance.

Hetianhe gas field, Lungudong gas field and Tazhong gas field are marine marine-origin natural gas reservoirs in the craton area in the Tarim Basin. The natural gas is generated from Cambrian source rocks. The simulation experiment indicated that the cracking of the dispersedly dissoluble organic matter remaining in the source rocks is the main origin of marine natural gas. There are two modes to form gas reservoirs, one is the dry gas reservoir such as Hetianhe gas field, in which gas accumulated on the fault belt with violent tectonic movement, the other is condensate gas reservoir formed on the inheriting uplift such as Lunnan and Tazhong gas fields. The hybrid simulation experiment of cracking gas and crude oil indicated that crude oil accumulated on a large scale in those uplift belts at the early stage, and natural gas filled the ancient oil reservoir at the late stage, and the gas reservoirs were formed after the gas mixed with the crude oil.

By taking the Tarim Basin, Sichuan Basin and Ordos Basin as examples, the conditions for deep marine reservoir formation were illustrated in three aspects listed below: late-stage superimposition style, burial history and structural deformation of the marine stratigraphic system. The burial history of marine source rocks can be divided into three types, i.e., type I, type II and type III, which are obviously different from the case with present hydrocarbon phases in terms of hydrocarbon generation and petroleum-reservoir formation. Based on evolution history, the structural belts in the marine stratigraphic sequence can also be divided into four types, i.e. earlier normal fault-later fault-fold type, earlier uplift-later fault-fold type, earlier uplift-later flattened slope type, and earlier depression-later thrust type. In this paper, a successive gas generation model was proposed, and it was particularly pointed out that coupling of geothermal field annealing evolution and tectonic subsidence and late gas generation from dispersed liquid hydrocarbon in highly matured to over-matured source rocks are key factors for formation of marine petroleum reservoirs. The geological conditions for formation of high-grade reservoirs in deep marine system, covering early hydrocarbon injection, deep denudation and buried dolomitization, were summarized. It was finally concluded that three major structural belts, i.e. paleo-uplift belt characterized by composite hydrocarbon accumulation, paleo-fault belt and high-energy sedimentary facies belt, were involved in marine hydrocarbon accumulation.

The experimental data yielded by Rock-Eval pyrolysis, kerogen atomic H/C, Py-GC and gold-tube sealing thermal simulation on the marine Cambrian-Ordovician source rock from the Tarim Basin revealed that the upper limit of maturity for natural gas generation or the “deadline of gas generation” for marine types I and II kerogens is equal to 3.0% of vitrinite reflectance (R o); while the “deadline of gas generation” for type III kerogens typically like coals is as high as 10% R o. Thus, different organic matter has obviously different utmost maturities for gas generation. The mass-balance calculation by kerogen elements showed that when R o>1.5%, the utmost amount of gas generation for the marine type II kerogen is less than 185 m3/t TOC, accounting for less than 30% of its total hydrocarbon generative potential; when R o>2.0%, it becomes 110 m3/t TOC, less than 20% of the total hydrocarbon generative potential. The amount of the gas generative potential obtained by Rock-Eval is only around one tenth of the calculated value by the mass balance of kerogen elements at the same thermal evolutionary stage, while those by Py-GC and gold-tube sealing simulation are intervenient between the above two. The utmost of gas generative potential at the over 1.3% R o stage is around 60–90 m3/t TOC, therefore, the amount of gas generation obtained by Rock-Eval is the minimum of gas generative potential, while that by the mass-balance calculation of kerogen elements is the maximum that the actual amount of gas generation should not exceed.

Through a case study of the high-efficiency gas reservoir in Feixianguan Formation in the northeast Sichuan Basin, quantitative and semi-quantitative analyses of key elements such as hydrocarbon generation, migration and accumulation, and reservoir evolution as well as their interplay in the critical moment of reservoir formation controlled by the energy field were carried out, by means of numerical modeling of the energy field. It was found that the climax time for Permian hydrocarbon generation was Late Triassic-Early Jurassic and accumulation of oil and gas has resulted in large-scale paleoreservoirs in paleostructural traps in Feixianguan Formation, a process facilitated by fractures connecting the sources. The paleoreservoirs have been turned into high-efficiency gas kitchens due to pyrolysis, which resulted from deep burial at a temperature of 170–210°C as induced by tremendously thick sedimentation in the foreland basin of Daba Mountain in Late Jurassic-Cretaceous period. Meanwhile, abundant acid gas like H2S produced from thermo-chemical sulfate reduction (TSR) at high temperatures leads to extensive dissolution of dolostone in the paleoreservoirs, which may in turn result in modification of the reservoirs and preservation of the reservoir rock porosity. The present distribution of gas reservoirs was ultimately determined in the processes of adjustment, cooling and decompression of the paleoreservoirs resulting from intense deformation in the front of Daba Mountain during the Himalayan orogeny.

There are abundant natural gas resources in Chinese marine sedimentary basin. The exploration hot shots of natural gas are the Palaeozoic marine strata here in recent years, and several large scale gas fields have been discovered. Chinese Palaeozoic high-post matured and coal measure hydrocarbon source rocks are mainly prone to gas generation in the present. This research considered that gas source rocks and TSR are the key cause of gas enrichment of marine strata. High-quality argillaceous and coal measure hydrocarbon rocks are distributed widely in the Palaeozoic marine strata, which have been in highly matured phase in the present. The argillaceous source rock generally contains various sulfates that could accelerate crude oil cracking to gas for TSR occurrence, and coal measure source rock mainly generates gas, so Chinese marine basin gives priority to accumulating gas. Marine strata have not founded oil reservoirs in the Sichuan Basin and Ordos Basin, and they consist mainly of dry gas. Marine natural gases are the mixed gases of oil cracking gas and coal-formed gas in a general way, oil cracking gases contain usually some H2S and CO2. Hydrocarbon carbon isotopes are very complicated, and methane and ethane isotopic values bear apparent reversal caused by thermal evolution and mixing among different genetic types of natural gas. Coal-formed gases are the main component of Chinese marine natural gas. The Upper Permian of the Sichuan Basin and the Carboniferous-Permian of the Ordos Basin coal measure hydrocarbon source rock present large hydrocarbon generation potential, which are the prospecting highlight of marine natural gas hereafter. Oil cracking gas exploration will be paid much attention to in the Tarim Basin because of the lack of coal measure hydrocarbon source rock.

The paper systematically analyzes the hydrocarbon migration characteristics of the Lower Cretaceous in the Erlian Basin, based on the geochemical data of mudstone and sandstone in the main hydrocarbon-generating sags. (1) The source rocks in K1ba and K1bt1 are estimated to be the mature ones, their hydrocarbon expulsion ratio can reach 32%–72%. The Type-I sags in oil windows possess good hydrocarbon generation and expulsion conditions, where commercial reservoirs can be formed. (2) According to the curves of the mudstone compaction and evolution of clay minerals, the rapid compaction stage of mudstones is the right time of hydrocarbon expulsion, i.e., primary migration. (3) The timing between hydrocarbon generation and expulsion is mainly related to the accordance of the oil window and the rapid compaction stage of mudstones in the hydrocarbon generation sags of Type-I. That forms the most matching relation between hydrocarbon generation and migration. (4) The faults and unconformities are the important paths for the secondary hydrocarbon migration. Especially, the unconformity between K1ba and K1bt1 has a favorable condition for oil accumulation, where the traps of all types are the main exploration targets. (5) Hydrocarbon migration effect, in the Uliastai sag, is most significant; that in the Saihan Tal and Anan sags comes next, and that in the Bayandanan and Jargalangt sags is worst.

Sophora moorcroftiana, an endemic leguminous shrub in Tibet, is found in valleys, slopes, terraces from 3,000 to 3,900 m above sea level along the middle reaches of the Yarlung Zangbo River. S. moorcroftiana is more tolerant of sand burial than other species in the valleys and is regarded as an ideal species for studying acclimatization to climatic factors. Stem basal diameter showed decline as altitude increased from 3,039 to 3,928 m in the Yarlung Zangbo River valley. Population density increased with the rise of altitude. However, seed bank density, seed germination and seed weight of S. moorcroftiana did not change with changing elevation. Plants responded to altitude variances with remarkable sensitivities. Stem basal diameter size declined along the vertical gradient between plateau and mountainside. Both in alpine and plateau areas, plants similarly adapted growth to altitude, but displayed different responses with respect to reproductive parameters, such as seed bank density, dry weight of seed, seed germination, seedling density and sapling density. Sand accretion remarkably reduced seed bank density and seedling density of the total population of S. moorcroftiana, but could promote shoot sprouting and shoot growing on the individual scale that stimulated the overall development of the population. The results suggested that this particular foredune species did not merely tolerate sand burial, but actually responded positively to sand accumulation.

In arid northwestern China, water shortages have triggered recent regulations affecting irrigation water use in desert-oasis agricultural systems. In order to determine the actual water demand of various crops and to develop standards for the rational use of water resources, we analyzed meteorological data from the Fukang desert ecosystem observation and experiment station (FKD), the Cele desert-grassland ecosystem observation and research station (CLD), and the Linze Inland River Basin Comprehensive Research Station (LZD), which all belong to the Chinese Ecosystem Research Network. We researched crop evapotranspiration (ETc) using the water balance method, the FAO-56 Penman-Monteith method, the Priestley-Taylor method, and the Hargreaves method, during the growing seasons of 2005 through 2009. Results indicate substantial differences in ETc, depending on the method used. At the CLD, the ETc from the soil water balance, FAO-56 Penman-Monteith, Priestley-Taylor, and Hargreaves methods were 1150.3±380.8, 783.7±33.6, 1018.3±22.1, and 611.2±23.3 mm, respectively; at the FKD, the corresponding results were 861.0±67.0, 834.2±83.9, 1453.5±47.1, and 1061.0±38.2 mm, respectively; and at the LZD, 823.4±110.4, 726.0±0.4, 722.3±29.4, and 1208.6±79.1 mm, respectively. The FAO-56 Penman-Monteith method provided a fairly good estimation of E Tc compared with the Priestley-Taylor and Hargreaves methods.

The relationship between the number of species and the area sampled is one of the oldest and best-documented patterns in community ecology. An equation of the form S = cA z describing more precisely the species–area relation for plant species in smaller area is proposed as a result of intensive examination of species presence. Several study and field data from a wild range of plant and animal taxa suggest that the slope, z, of a graph of the logarithm of species richness against the logarithm of area is not a constant to the grassland or woodland community. We collected replicated and randomized plant data at 6 spatial scales from 1 m2 to 1 km2 in the desert region of northwest China to identify the scale dependence in desert plant biodiversity. The results showed that the slope of the log–log plot varied systematically with spatial scale. The value of z was high (0.37) at small scales from 1 to 10 m2 and it decreased with increased spatial scale subsequently. When spatial scales varied from 1 m2 to 1 km2, the value of z varied from 0.37 to 0.035, suggesting that desert plant diversity has strongly scale-dependence at the small scales (less than 100 m2). The result is different from the research of grassland and woodland communities.

The modifiable areal unit problem has significant implications for ecological research that involve investigating and analyzing the spatial heterogeneity of plant community. In this paper, semivariance analysis was used to evaluate the spatial characteristics of plant community in the␣transitional zone between oasis and desert. The spatial structures of the plant community were characterized using exponent model variogram parameters, including nugget (C0) range (A0) and sill (C0+C). Two methods were employed to determine the scale effect of spatial heterogeneity. (1) A constant grain size (10×10 m2) and variational plot areas have been used to analyze spatial heterogeneity of the plant community. (2) The grain size was only changed to analyze spatial heterogeneity. In addition, the plot of 500×500 m2 was clustered into nested units of different shapes and different directions to analyze zoning effect. Finally, using semivariance analysis, we obtained a suitable plot area and zoning approach to weaken the scale and zoning effects. The results showed that the effects of scale on different variogram parameters had significant difference. For example, C0 and C0+C were very sensitive at small scales, A0 was influenced significantly by plot area at larger scales, and C0 and A0 were relatively sensitive to different zoning approaches. In order to get more representative characteristic of spatial heterogeneity of the plant community, the sampling area should be more than 200×200 m2 for Nitraria sphaerocarpa populations, 100×100 m2 for Reaumuria soongorica populations, and a grain size from 20×20 m2 to 30×30 m2 for both populations.