Search

A purely inorganic tri-vanadium-capped Keggin phosphomolybdate [Na3PMo12V3O43]·4H2O (compound 1) has been synthesized by hydrothermal means and characterized via powder X-ray diffraction, infrared spectrum, thermogravimetric analysis, single-crystal X-ray diffraction, scanning electron microscope, ultraviolet–visible absorption spectroscopy, ultraviolet–visible diffuse reflection spectra as well as electrochemical cyclic voltammetry tests. The structure analysis displays that compound 1 is a symmetric tri-vanadium-capped cluster through six half occupancy {VO5} units. Compound 1 remains a purely inorganic Keggin phosphomolybdate, which presents electrocatalytic properties for the oxidization of ascorbic acid and reduction of H2O2. At the same time, it possesses high-efficiency degradation capability for typical methylene blue, Rhodamine B and methyl orange dyes under ultraviolet light.

Soil labile inorganic and organic phosphorus (L-Pi and L-Po) extracted by NaHCO3 are potentially important sources of plant-available P. Their availability is strongly affected by soil physiochemical and biological properties. Here we conducted a field study in an arid region of northwestern China to investigate how L-Pi and L-Po dynamics are affected by changes in physiochemical and biological variables caused by agricultural cultivation of calcareous soils. Topsoils were sampled at multiple sites from natural calcareous grasslands and cultivated farmlands of different ages (32–40 vs. 90–100 years) that had been converted from natural grasslands. We measured L-Pi and L-Po concentrations and a set of key physiochemical (soil pH, concentrations of base cations (K+ + Na+ + Ca2+ + Mg2+), acid anions (Cl− + NO3− + SO42−), nitrate and ammonium nitrogen (N), organic carbon, and total P) and biological (soil microbial biomass carbon (Cmic), alkaline phosphatase activity (Aalp), and abundances of soil macroinvertebrates (Amacro) and mesoinvertebrates (Ameso)) variables. The concentration of L-Pi and L-Po was 484% and 128% higher and their proportion in the total P content was 354% and 78% higher in young farmland soils, whereas L-Pi and L-Po concentrations were 583% and 423% higher and their proportions were 353% and 240% higher in old farmland soils compared to grassland soils. Increases in L-Pi and L-Po attributable to soil P release may be driven by crucial processes of soil acidification-induced phosphate dissolution and soil biota-driven Po mineralisation. Path analyses revealed that L-Pi and L-Po dynamics were shaped by the complex interactions among five key controlling factors, soil pH, nitrate-N, Ameso, Cmic, and Aalp, involved in these crucial processes. We conclude that cultivation of calcareous soils significantly increases the availability of L-Pi and L-Po, emphasizing the importance of this land-use change as a regulator of P cycling in calcareous soils.

In view of the problem of how to effectively compare and analyze the influence of angle tracking error of monopulse radar caused by the cooperative aerial bombing of dual stealth aircraft, a dynamic trajectory model of cooperative aerial bombing of dual stealth aircraft in level flight is established for the first time, and the acquisition method of dynamic RCS under the aerial bombing of dual aircraft is proposed. By using the time-varying dynamic signal-to-noise ratio as a parameter variable, a single pulse radar angle tracking error solution model is established, which is suitable for the stealth aircraft dual aircraft formation. This paper analyzes the influence of cooperative aerial dropping of dual stealth aircraft formation on the angle tracking error performance of monopulse radar, and concludes for the first time that the angle tracking error of monopulse radar will be reduced when there is no interference in the air bombing of two planes.

Aiming at the problem of how to effectively compare and analyze the influence of the angle tracking error of monopulse radar caused by the difference of the dual stealth aircraft formation in the formation navigation direction, the dynamic track model of the dual stealth aircraft in different navigation directions is established for the first time, and the acquisition method of the dynamic RCS of the formation under different navigation directions is put forward. Using the time-varying dynamic signal-to-noise ratio of the dual stealth aircraft in different flight directions as parameters, the monopulse radar angle tracking error solving model suitable for the cooperative flight of dual stealth aircraft is established. This paper analyzes the influence of the difference of the dual aircrafts’ heading direction on the angle tracking error performance of monopulse radar. It is the first time to conclude that the angle tracking error of monopulse radar will increase obviously with the increase of the heading angle of dual stealth aircraft when there is no interference.

In irrigation-maintained desert agroecosystems in northwestern China, cereal crop production occurs mainly as maize (Zea mays L.) monoculture (MM), along with wheat (Triticum aestivum L.) monoculture (WM) and maize/wheat intercropping (MWI). However, our understanding of the role of different cropping systems in regulating the abundance and diversity of ground- and soil-dwelling insect herbivores (pests) and arthropod predators (natural enemies of pests), and thus cascading effects on biological pest control services is still poor. To address this important issue, we measured ground- and soil-dwelling insect pests and associated arthropod natural enemies in fields of MM, WM, and MWI using pitfall traps and hand-sorting in spring and summer at six sites in a desert agroecosystem in northwestern China. Each site contained three cropping systems with cultivation for at least five years. We also calculated the abundance- and richness-based ratios of ground- and soil-dwelling arthropod predators to insect herbivores (P: H ratios) as indices for assessing pest biocontrol services. For ground-dwelling communities, we found that MM harbored more abundant and diverse insect herbivores and insect predators than the other systems, whereas MWI harbored more abundant and diverse non-insect predators and had higher P: H ratios compared with the other systems across seasons. For soil-dwelling communities, we found that MM harbored more abundant and diverse insect herbivores than MWI in spring, whereas WM harbored less abundant and diverse insect herbivores than the other systems in summer. However, MWI harbored more abundant and diverse insect predators than the other systems, whereas WM harbored less abundant and diverse non-insect predators than the other systems in either season. Moreover, MM harbored more abundant and diverse non-insect predators than MWI in summer. The P: H ratios were higher in MWI than in MM and WM in spring, but did not differ across cropping systems in summer. Our results demonstrate that the magnitude and direction of the effects of cropping systems are highly season specific and vary across groups of ground- and soil-dwelling herbivores and predators. Furthermore, intercropping delivers greater pest biocontrol services than monoculture systems. These findings provide key insights towards developing more effective intercropping systems for pest suppression.

BACKGROUND AND AIMS: Irrigation-maintained artificial oases (AO) in arid regions of northwestern China provide vital human settlement sites. Recent human population increases has caused rapid AO expansion, mainly through transforming natural grassland to arable and afforested land. Here, we assessed how soil biodiversity is affected by various AO expansion strategies, each representing historical land-use regimes. METHODS: We sampled six dominant functional groups of soil biota, covering multiple trophic levels: macrofauna consumers (predators and insect herbivores), mesofauna decomposers (Oribatida and Collembola), and microbial decomposers (bacteria and fungi). Sampling was carried out in three AO sites of northwestern China, each containing distinct land uses: natural grasslands (NG; non-irrigated), shrub (Haloxylon ammodendron) plantations (SP; non-irrigated), tree (Populus gansuensis) plantations (TP; irrigated), and arable lands (AL; irrigated). RESULTS: The conversion of NG to SP, TP, and AL eliminated or reduced the abundance of some NG-adapted taxa. Their replacements were exotic species better suited for anthropogenic habitats. As a result, community composition shifted in all six functional groups, with greater differences between NG and TP and AL than between NG and SP. Based on taxonomic gains and losses within each group, we determined that NG to SP conversion positively affected diversity among predators, Collembola, and fungi, but negatively affected diversity of insect herbivores and Oribatida. Bacterial diversity remained unaffected. However, converting NG to TP and AL significantly promoted diversity in all six functional groups, although effect sizes differed. CONCLUSIONS: Our results suggest that different AO expansion strategies differentially affected the diversity and structure of belowground communities, which in turn, cascaded down to ecosystem functioning differently. These findings not only contribute to a better understanding of how the diversity and community composition within soil food-webs respond to land-use change but also provide key insights into the development of management strategies for AO ecosystems in drylands to mitigate the negative impact of land-use change on soil biodiversity and ecosystem functioning.

Three novel Keggin arsenomolybdates with transition metal modifying caps, (Hbimb)(H2bimb)[AsMoVI8VV4Co2O40] (1), (Hbimb)2(H2bimb)0.5[AsMoVI8VV4Cu2O40]·1.5H2O (2), and [CuI(imi)2][{CuI(imi)2}4{AsMoV6VVI6O40(VIV2O2)}] (3) (bimb = 1,4-bis(imidazol-l-yl)butane; imi = imidazole), were obtained via altering the solution pH and the organic ligands in the reaction system, and were characterized via routine techniques. Compounds 1 and 2 are tetra-vanadium substituted {AsMoVI8VV4O40} clusters capped by two Co2+ or Cu2+ cations at two symmetrical pit positions of two opposite {Mo4O18} tetramers, and these represent the first tetra-vanadium substituted bi-cobalt(II)/copper(II) capped assemblies. The basic unit of compound 3 is one hexa-electron-reduced Keggin polyoxoanion {AsMoV6MoVI6O40} capped by two {VO5} units at the same positions. The adjacent basic units were bonded together via the square binuclear linker {Cu2(imi)4O2} to yield an infinite 1D cap-to-cap chain, which was further aggregated together in A–B–A–B mode via a pair of {Cu(1)(imi)2} linkers, forming an unique 2D layer. Compounds 1–3 show bifunctional electrocatalytic character and effective photocatalytic performance toward the degradation of typical dyes under UV irradiation.

Given its double functions of selective separation and concentration for ions, the potential of electrodialysis (ED) for the reclamation of waste acid has been widely recognized. In view of some differences from the cases of salt systems, a deep grasp on the effects of operating conditions on ED-based acid recovery is urgently required. Moreover, it is also challenging and desirable to effectively address the modelling issue of the membrane process. In this study, the influences of some typical operational factors, including current density, membrane selection, acid concentration of waste effluent, concentration differences between the dilute and concentrating compartments, on ED performances, such as its concentration evolution, current utilization and energy consumption, are systematically investigated. In particular, a fundamental model is established on the basis of the equations of Nernst-Planck, Navier-Stokes and Continuity to understand the influences of operating conditions and predict the relevant work performances. Therein, the proton diffusion coefficient of the used anion exchange membrane (AEM) can be regressed according to its practical performance and input. It is noticed that the obtained proton diffusion efficient is closely related to the AEM selection, but has almost nothing to do with the specific operational conditions and even the acid systems. A series of ED experiments show that the simulation results are in good agreement with the experimental results, which verifies the validity of the proposed model. Especially, this work confirms that proton leakage across AEMs should be the culprit in the non-ideal behaviors of ED-based acid recovery. Hopefully, the new model can contribute to the stack design, process optimization and scale-up of the ED-based acid recovery.

An extraordinary supramolecular hybrid material based on the Keggin arsenotungstate, (Hbimb) 3 [AsW 12 O 40 ]·H 2 O ( 1 ) (bimb = 1,4-bis(imidazol-l-yl)butane) has been synthesized under hydrothermal condition and characterized by elemental analysis, infrared (IR), thermogravimetry (TG), X-Ray Diffractomer (XRD), and single-crystal XRD. In compound 1 the {AsW 12 O 40 } cluster is linked to 14 organic ligands through their surface oxygen atoms, which are further embraced by 20 polyanions analogs to form a tightly packed 3D supramolecular network with a (4 5 ·6)(4 52 ·6 38 ·8)(4 9 ·6) 2 topology via strong hydrogen bonds and supramolecular interactions. Compound 1 represents the highest connectivity of Keggin supramolecular arsenotungstate, which exhibits electrocatalytic behaviors for reduction of H 2 O 2 and high efficiency degradation capability for two typical dyes methylene blue (MB) and rhodamine B (RhB) under UV light.

Precipitation in arid ecosystems occurs as rain pulses, namely infrequent, discrete and unpredictable events of variable intensity. Rain pulses have impacts on activity patterns of macroarthropods, but their impacts on activity patterns of microarthropods are not fully known. Here, we designed a rainfall manipulative experiment in an arid ecosystem (MAP = 117 mm) in Gansu province, northwestern China to examine short-term activity responses of two dominant microarthropod groups, Collembola and mites, to experimental rain pulses. We added water in one large 15-mm event (large pulse) and in three separate small 5-mm events (small pulses), six days apart. We had control plots without water addition. After watering treatment, we measured microarthropods and soil moisture content (SMC) and temperature (ST) over a period of 15 days. The study period was split into an initial response stage (first 5 days; IRS), a prolonged response stage (next 5 days; PRS) and a final response stage (last 5 days; FRS). Both pulse treatments did not affect the number of microarthropod taxa, but significantly increased the number of microarthropods relative to the control, with a greater increase in large than small pulses in PRS and FRS. Within the Collembola assemblage, both pulse treatments significantly increased the number of Entomobryidae, but did not affect the numbers of Hypogastruridae, Isotomidae and Sminthuridae. Within the assemblage of mites, both pulse treatments significantly decreased the number of Oribatida, but did not affect the numbers of Astigmata, Mesostigmata and Prostigmata. Across three response stages, the number of oribatid mites was negatively correlated with SMC and positively correlated with ST, while the number of entomobryid springtails was positively correlated with SMC and negatively correlated with ST. Our results provide experimental evidence that the microarthropod community was strongly affected by short-term experimental rain pulses, but this effect varied acros taxa, experimental stages and pulse sizes.

Two extended Wells–Dawson arsenomolybdates, (imi)2[{CuI(imi)2}2{Na(imi)2}{AsIIIAs2VMo18O62}]·2H2O (1) and {CuI0.5(trz)}6 [{CuI0.5(trz)}6(As2Mo18O62)] (2), (imi = iminazole; trz = 1,2,3-triazole), are hydrothermally synthesized and extensively characterized. Compounds 1 and 2 contain a fully oxidized Dawson {As2Mo18O62}6− (abbreviated as {As2Mo18}) anion as the parent cluster unit. Compound 1 is a symmetric mono-arsenate capped anion cluster modified by two half occupancy {AsO3} units, which represents a new capping mode for Dawson clusters. The two adjacent mono-arsenate capped structures are linked by two {Na(imi)2} bridges to form a dimeric cluster, which, as a tetra-dentate ligand, further connects with adjacent dimers by four {Cu(imi)2} linkers to form an infinite ladder shaped chain. In compound 2, each classical Dawson cluster links six adjacent analogs by six {Cu0.5(trz)2} fragments forming an unprecedented 3D network via a unique belt-to-belt staggered pattern. This structure can be simplified as a 2,6-connected 3-D framework with {812·123}{8}3 topology. Compounds 1 and 2 represent the first 1-D and 3-D assemblies of Dawson-type arsenomolybdates, respectively. They display unique electrocatalytic behavior for the oxidation of ascorbic acid (AA) and reduction of NO2− as well as good photocatalytic properties for the degradation of the difficult-to-degrade dye AP under UV light.

Objectives Astragaloside-IV (AS-IV) protects the nerve cells of Parkinson's disease (PD) from damage. Long non-coding RNA (lincRNA) has been found to be important for many diseases. Lincnra-p21 is abnormally expressed in PD. The purpose of this study was to investigate whether Astragaloside-IV (AS-IV) affects endoplasmic reticulum stress (ERS)-induced neuronal apoptosis in PD, and its possible mechanisms. Methods The PD mouse model was established via injecting 1-methyl-4-phenyl-1, 2, 3, 6- tetrahydropyridine (MPTP) and the PD cell model was established via inducing the MN9D cell line with 1-methyl-4-pehnyl-pyridine (MPP+). The behavioral testing of PD model mice was tested after AS-IV treatment and PD-related lincRNAs expression were detected by qRT-PCR. After treatment of PD model cells with AS-IV, lincRNA-p21 expression was detected by qRT-PCR, and cell viability and apoptosis were detected by MTT assay and flow cytometry, respectively. The binding of lincRNA-p21 to C/EBP-homologous (CHOP) protein was investigated by RNA immunoprecipitation and RNA pull-down, and the effect of lincRNA-p21 on the ubiquitination of CHOP protein was examined by ubiquitination assay. The role of lincRNA-p21 in PD model was studied by cell transfection. Results In PD mice, AS-IV can improve the behavior of mice and significantly inhibit expression of lincRNA-p21. Similarly, AS-IV can obviously restrain the expression of lincRNA-p21 in PD cells, and obviously elevated cell viability and restrained apoptosis. LincRNA-p21 is able to bind to CHOP protein. Further studies showed that restraint of lincRNA-p21 expression can facilitate ubiquitination of CHOP and accelerate its protein degradation. In AS-IV-treated PD model cells, overexpression of lincRNA-p21 lessened cell viability and facilitated apoptosis, whereas low expression of CHOP reversed this result. Conclusion In this study, we found that AS-IV can lessen the expression of CHOP protein by restraining the expression of lincRNA-p21 in the PD model, thereby inhibiting neuronal apoptosis.

It has been realized the proton leakage behavior of anion-exchange membrane (AEM) seriously influences the practical applications of bipolar membrane electrodialysis (BMED), for example, the reclamation of brine. In this work, a concept of composite AEM, coating a thin acid-blocking layer bearing weak base functional groups onto a strong base AEM substrate, is put forward to alleviate the membrane conductivity deterioration due to the endowment of acid-blocking property. Above all, Poly(vinylidene fluoride)-graft-Poly[2-(N,N-dimethylamino) ethyl methacrylate] (PVDF-g-PDMAEMA which embraces significant hydrophilic differences between the side and main chains is synthesized by atom transfer radical polymerization (ATRP) and used for preparing the acid-blocking layer by solvent evaporation. Subsequently, series of experiments for measuring the water uptake, the acid adsorption, the current-voltage curve and transport number are performed to optimize the ion-exchange capacity of as-synthesized membrane material. Furthermore, as-prepared acid-blocking layer is coated onto the a strong base AEM substrate fabricated from the blend of PVDF and cross-linking PDMAEMA to prepare the supposed composite AEM. SEM observation clearly demonstrates the bilayer structure and good adhesion therein. AFM phase image confirms the formation of microphase separation morphology in which the hydrophilic channel used for ion transport looks uniform, continuous and well-connected. The ED-based acid concentration and BMED-based brine reclamation experiments show as-prepared composite AEM has an excellent acid-blocking performance and acceptable membrane resistance in comparison with the conventional AEM and even the commercial acid-blocking AEM. This indicates that the proposed AEM-preparing strategy may contribute to beating the trade-off effect between acid-blocking performance and membrane conductivity.

The community dynamics of ground beetles as a dominant group in arid ecosystems are strongly affected by land-use change associated alterations in vegetation and soil conditions. However, little is known about the relative effects of altered vegetation and soil, or their interactions, on the composition and diversity of beetle functional groups. To address this question, we collected data on the species richness and activity abundance of ground carabid and tenebrionid beetle functional groups (predators, herbivores, and detritivores), along a gradient of land-use conversion from natural grassland to pure and mixed plantations of two shrub species (Haloxylon ammodendron and Tamarix ramosissima) in an arid region of northwestern China. Additionally, we collected key variables related to the vegetation (shrub cover, height, herbaceous plant biomass, and species richness) and soil (soil pH, texture, and salinity). Variation partitioning showed that vegetation changes had stronger effects on the functional group composition than changes in the soil did. However, vegetation–soil interactions explained more of the composition variation in the beetle functional groups than vegetation or soil alone. Shrub cover and herbaceous species richness were the best predictors of species composition of detritivores and herbivores. For predator species composition, shrub height and cover were the best predictors. Structural equation models showed that changes in vegetation and soil influenced beetle abundance and diversity through both direct and indirect effects, and the strength of this influence varied among the functional groups. Overall, we conclude that vegetation and vegetation–soil interactions are important determinants of beetle community assemblies.

To effectively test the detection performance of the monopulse radar under cooperative jamming of dual stealth aircraft formation, a blinking jamming model based on the interval of time-varying dual-aircraft formation is established for the first time in this study. By geometric modeling of the blinking jamming mode of the dual-aircraft formation, the authors solved the equivalent time-varying dynamic radar cross section of the penetration operation of the dual-aircraft formation; then, by taking the signal-to-interference ratio of the aircraft fuselage target echo in the actual formation as a parametric variable, we derived the equations for instantaneous detection distance, instantaneous detection probability, and cumulative detection probability of the monopulse radar in the formation projectile, and these equations were applicable to calculation under the actual jamming mode of dual-aircraft formation. Through simulation, the authors concluded for the first time that as the supersonic endurance speed increased, releasing jamming could reduce the radar detection probability considerably by more than 60%, while releasing projectiles could increase the formation’s risk of being detected by the radar by 30.37%. Thus, to effectively reduce the stability of the radar’s detection and tracking performance, the jamming power of the dual stealth aircraft formation should be no smaller than 0.5 kW and the signal gain of the formation should be no less than 20 dB.

A mathematical model for simulating soil water and salt transfer under mulched furrow irrigation with saline water was presented. The model performance was evaluated by comparing the simulated values with observed data from the field experiment. The results demonstrated that the model performed reliably in the simulation of water and salt transfer under field conditions. In addition, the model was also used to simulate the process of soil water and salt transfer after saline water irrigation. The simulation demonstrated that the increment of soil water storage below the bottom of the furrow was nearly equal to the value below the top of the ridge immediately after the end of the irrigation (17 h) when the downward movement of irrigation water was restricted by the clay interlayer in soil. However, during the irrigation interval (192 h and 384 h after the irrigation), more water was maintained below the top of the ridge due to a considerable reduction of evaporation under mulched furrow irrigation. Soil salt mainly comes from saline water irrigation and the soil salt below the top of the ridge mainly increased at the redistribution phase (17 h). During the irrigation interval, soil conductivity in surface soil layer below the top of the ridge was smaller than that below the bottom of the furrow, which indicated that the distribution of soil salt below the top of the ridge was more uniform than below the furrow. The model presented here offers an efficient approach to estimate environmental effects of mulched furrow irrigation technology associated to saline water utilization.

Aquaculture wastewater is one of the most important alternative water resources in arid regions where scarcity of fresh water is common. Irrigation with this kind of water may affect soil microbial functional diversity and community structure as changes of soil environment would be significant. Here, we conducted a field sampling to investigate these effects using Biolog and metagenomic methods. The results demonstrated that irrigation with aquaculture wastewater could dramatically reduce soil microbial functional diversity. The values of diversity indices and sole carbon source utilization were all significantly decreased. Increased soil salinity, especially Cl concentration, appeared primarily associated with the decreases. Differently, higher bacterial community diversity was obtained in aquaculture wastewater irrigated soils. More abundant phyla Actinobacteria, Chloroflexi, Acidobacteria, Gemmatimonadetes and fewer members of Proteobacteria, Bacteroidetes and Planctomycetes were found in this kind of soils. Changes in the concentration of soil Cl mainly accounted for the shifts of bacterial community composition. This research can improve our understanding of how aquaculture wastewater irrigation changes soil microbial process and as a result, be useful to manage soil and wastewater resources in arid regions.

Oases are common in desert regions of northwestern China and are major sites for human settlement. The implementation of oasis conservation planning has led to afforestation with appropriate shrubs and trees in the native grasslands surrounding inhabited oases. However, little is known about how this Land use change from native grassland to shrub and tree plantations influences the composition of ground-dwelling arthropod communities and the performance of their different trophic groups. To address this, we measured activity density, taxon richness, and relative abundance of four different ground arthropod trophic groups (spiders, beetle predators, beetle herbivores, and beetle detritivores) and several environmental variables affecting arthropod distributions (vegetation cover, ground temperature, soil moisture, soil properties, and leaf litter) along an experimentally established land use change gradient of a mature shrub (Haloxylon ammodendron) planation, a mature poplar (Populus gansuensis) plantation and a mature pine (Pinus sylvestris) plantation, as well as a native grassland from which all cultivated systems were converted. We found that converted shrub plantation had much lower activity density of predatory, herbivorous, and detritivorous beetles; similar activity density of spiders; and similar taxa richness of all four trophic groups relative to the native grassland. However, converted forest plantations regardless of tree species had much higher activity density of spiders, lower activity density of the three beetle groups, much higher richness of predatory beetles, and lower richness of herbivorous and detritivorous beetles. We also found a change in the composition of the ground arthropod community that was largely driven by changes in ground temperature and leaf litter mass. We conclude that conversion of native grassland to shrub and tree plantations can significantly affect ground-dwelling arthropod communities, reducing the activity of ground-dwelling beetle assemblages while increasing that of ground-dwelling spider assemblages. These findings are important for conserving native arthropod diversity in desert ecosystems.

Here, we present a mathematical model for simulating both soil water flow and salt transport in two directions (perpendicular and parallel to the drip tubing) under mulched drip irrigation with saline water. We evaluated the effectiveness of this model by comparing the simulated values with observed data from the field experiment (one treatment with three replications was imposed with irrigation water electrical conductivity of 4.0 dS m−1 and amounts of 2400 m3 ha−1 under mulched drip irrigation system). The results demonstrated that the model performed reliably in the simulation of water flow and salt transport under field conditions. In addition, the model was also used to simulate the spatial distribution patterns of soil water and salt in the two directions in relation to different treatments of irrigation quantity and quality. The simulation demonstrated that the volume of wetted soil was affected by both the plastic mulching and irrigation amount. The wetted region was expanded to the middle of the plastic mulching when the irrigation amount was high and the uniformity of irrigation increased with increasing irrigation volume. Soil water content in the direction parallel to the drip tubing was higher than that perpendicular to the tubing at the same distance, indicating that the wetting fronts overlapped more rapidly in the direction parallel to the drip tubing. The soil salt concentration was high at the edges of the wetting front, with a fairly large desalinated area immediately underneath and adjacent to the drippers. The model presented here offers an efficient approach to investigating the mechanisms underlying soil water flow and salt transport and for designing mulched drip irrigation systems with saline water.

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.

A vast area of native shrub-dominated steppe at the margins of desert oases in arid regions of China had been reclaimed as farmland in the last century for grain production to feed growing human populations. This study evaluated the consequences of this land-use change on the activity density, taxa richness and composition of functional groups (herbivores, predators and detritivores) of ground-dwelling beetles and spiders, which include some important ecological groups of natural enemies of insect pests (e.g. predatory spiders and beetles), pollinators and decomposers (e.g. detritivorous beetles). Ground-dwelling beetles and spiders were collected using pitfall traps in native steppe habitats and adjacent irrigated farmland of different ages (cultivated either for 27 or at least for 90 years). It was found the conversion of native steppe to farmland, regardless of farmland age, led to a significant increase in activity density of predators, with a greater increase in 90-year-old farmland than in 27-year-old farmland, but did not affect their taxa richness. However, native steppe conversion to farmland, regardless of farmland age, led to significant declines in activity density and taxa richness of both detritivores and herbivores, with a much greater decrease of activity or richness in detritivores than in herbivores in both farmland types. We also observed taxa-specific responses to the land conversion within functional groups. The functional composition of the beetle and spider community shifted from a community dominated by detritivores in the native steppe sites to one dominated by predators in the irrigated farmland sites. Our results suggest that the different functional groups of ground-dwelling beetles and spiders responded in a different way to the land conversion. The remarkable increase in predators and the dramatic decline in detritivores by converting natural vegetation to agricultural land are expected to strongly affect the desert ecosystem services such as biological pest control, pollination and decomposition.

Increased demand for food due to the rapidly growing human population has led to extensive conversion of native steppes at the margins of oases in arid lands of northwest China into intensively managed farmlands. However, the consequences of this land-use change for soil microarthropod biodiversity and ecosystem functioning remain unknown. Here we assessed how conversion of a native steppe to irrigated farmlands of different ages affects the abundance and composition of soil microarthropods and how changes in soil microarthropod biodiversity could scale up to influence soil carbon and nitrogen stocks. We sampled microarthropod communities over two growing seasons from native steppes and cultivated soils of a 27year-old irrigated farmland and a 90-year-old irrigated farmland, both of which were converted from the native steppe. Topsoil properties and bulk and labile pools of carbon and nitrogen, including soil organic carbon, dissolved organic carbon (DOC), microbial biomass carbon (MBC), total nitrogen (TN), inorganic nitrogen (IN), and microbial biomass nitrogen (MBN), were also measured. The conversion of native steppe to either of the two farmlands significantly increased the abundance and taxa richness of three taxonomic groups (mites, collembolans, and others) and four trophic groups (herbivores, predators, detritivores, and fungivores); this effect was greater in the 90-year-old farmland for the abundance of all taxonomic and trophic groups except for herbivores and was similar between the two farmlands for the richness of all taxonomic and trophic groups. Taxonomic and trophic composition of the microarthropod community showed strong shifts in response to conversion of native steppe to either of the two farmlands. Compositional changes were largely mediated by changes in soil environments. Changes

There is little information regarding the sustainability of the high yield agroecosystem with double ridges and furrows mulched with plastic film in semi-arid areas. In this study, we explored the sustainability of this agroecosystem with different mulching time during two growing seasons over 2006 and 2007. Three treatments were designed: (i) plastic film mulching applied at sowing and film removed at harvest (CK); (ii) mulching applied 30 days before sowing and removed at harvest (M1); and (iii) mulching applied at sowing and film left on field after harvest and used continually for mulching in the second season (M2). Microbial biomass C (MBC) and ratio of MBC to soil organic C (SOC) (MBC/SOC) were higher in M1 and M2 than in CK in 2007 growing season. The reduction rates of the ratios of light fraction of organic C (LFOC) to SOC (LFOC/SOC) with sampling dates were 0.0020, 0.0047 and 0.0045 for CK, M1 and M2, respectively. A larger value means a faster reduction rate of LFOC/SOC with sampling dates, and implying farming system would face a higher unsustainable risk. MBC correlated negative significantly with LFOC ( R = −0.939, P = 0.0001) and mineral N ( R = −0.835, P = 0.0007) due to low soil C pool. Accordingly, film mulched ridge and furrow system would threaten the sustainability of soil ecosystem via MBC increase a semi-arid agroecosystem. The practices of mulching applied 30 d before sowing (M1) and use of plastic film once every two years (M2) lead to increased environmental risk for the farming system.

Many studies have reported evidence describing the effects of K2SO4 fertilizer on crop productivity, but there is scant information about the yield-increasing mechanisms when influencing soil properties by K2SO4 application in calcareous and alkaline soils. In this study, one field and incubation experiments were conducted to investigate the effects of K2SO4 fertilizer on crop yields and soil properties in calcareous and alkaline soils on the Loess Plateau of Northwestern China. In field experiments, four K2SO4 treatments were applied to potato (Solanum tuberosum L.) in 2007 and spring wheat (Triticum aestivum L.) in 2008: (1) CK: no K2SO4; (2) T1: K2SO4 @ 100 kg ha−1 in 2007 and 50 kg ha−1 in 2008; (3) T2: K2SO4 @ 200 kg ha−1 in 2007 and 100 kg ha−1 in 2008; and (4) T3: K2SO4 @ 300 kg ha−1 in 2007 and 150 kg ha−1 in 2008. In 2007, potato yield increased by 17.4% in T2 and 21.5% in T3 compared with CK, but did not significantly increase in T1. In 2008, spring wheat yields increased by 10.0%, 15.8% and 18.7% in T1, T2 and T3 treatments, respectively, compared with CK. Stepwise regression (P ≤ 0.05) revealed that soil-available K at tuber formation and starch accumulation stage, and available P at starch accumulation stage correlated well with potato yield. Soil available P before sowing and at anthesis correlated well with spring wheat yield. Soil available P content was mostly higher in T1, T2 and T3 than in CK from June 2007 to August 2008 when the same dose P fertilizer was applied in all plots. Applying K2SO4 decreased soil pH. Soil available P was significantly negatively correlated with soil pH (R = –0.5721, P = 0.0015). In an incubation experiment, the four K2SO4 treatments were designed: (1) CK: no K2SO4; (2) S1: K2SO4 @ 0.44 g kg−1 dry soil; (3) S2: K2SO4 @ 0.88 g kg−1 dry soil; (4) S3: K2SO4 @ 1.32 g kg−1 dry soil. The results also showed that addition of K2SO4 significantly decreased soil pH and increased available P in calcareous and alkaline soils. Our study suggests that K2SO4 is desirable for improving crop productivity by increasing soil P availability via decreasing soil pH in calcareous and alkaline soils besides K effect in a low input dryland agroecosystem.

Reconfiguration of hillside fields into terraces is a key technique for water and soil conservation in mountainous regions. In this study, the effects of adding manure on soil water status and crop yields in newly-built terraces in 7 growing seasons on the semi-arid Loess Plateau of China were evaluated. Experimental treatments including CK (control treatment with no fertilizer), NP (nitrogen and phosphorus), M (manure), and MNP (manure, nitrogen and phosphorus) were employed with a field pea-spring wheat-potato cropping system. Manure groups are better able to conserve soil water, average soil water content in the 0-100 cm soil profile in the 5 years prior to sowing was over 42.2 mm in the MNP group than in the NP group, and 23.2 mm higher in the M group than in the CK group. After 7 years, soil water in the upper 200 cm of soil in the MNP and M groups was kept in balance, while significant soil water depletion reached the 140 cm soil layer in the CK and NP groups when compared to their values before sowing in 2004. Manure management significantly increased soil water stable macro-aggregates (>0.25 mm) compared to groups without manure in the 0-20 and 20-40 cm soil layers. Average yield over the 7 years was higher in the MNP group than in the CK, NP and M groups by 212%, 54% and 82%, respectively, and average water use efficiency (WUE) was higher by 207%, 51% and 77%, respectively. In the long run, treatment with inorganic fertilizer (NP) alone may not be sufficient to maintain high yields due to soil water depletion year after year. Farmers should be encouraged to apply manure to maintain the sustainability of agro-ecosystems in newly-built terraces in semi-arid areas. (c) 2012 Elsevier B.V. All rights reserved.

Soil harbors remarkably stabilise bacterial communities at the phylum level. However, no two soils have exactly the same structure of bacterial phyla. The structure of microbial community is strongly influenced by the type of land-use through changes in soil attributes. Using high-throughput pyrosequencing and quantitative polymerase chain reaction techniques, soil microbial community structures were investigated along a land-use gradient of 100- and 27-year farmlands, a 33-year Pinus forest, a 28-year poplar forest, and a 21-year shrubland, as well as a native desert from which all cultivated systems were converted. The results revealed that the dominant phylotypes in the native soil comprised primarily of Alphaproteobacteria, Actinobacteria, Bacteroidetes, and Firmicutes, accounting for > 71.4% of the total bacterial 16S rRNA sequence reads. Changes in land-use led to a significant; decrease in these dominant phylotypes down to 33.4%. In contrast, the phylotypes with low abundance, such as Acidobacteria, Chloroflexi, Nitrospira, and Gammaproteobacteria, increased sharply from 4.5%-5.9% in the native soil to 20.9%-30.2% of the total 16S rRNA gene sequences in the cultivated soils except for the soil from the shrubland. These contrasting changes in the major taxa appear to be correlated with the changes in soil attributes. For instance, bacterial and archaeal amoA genes were found to be 960- and 3800-fold more abundant in the soil from the 100-year farmland than the native soil. The changes in numerically less dominant nitrifying phylotypes are consistent with soil inorganic nitrogen dynamics. Quantification of the 16S rRNA genes demonstrated that bacteria and archaea were about two to three orders of magnitude more abundant in the cultivated soil than in the native soil. Hence, land-use type affects the soil bacterial community structure, which has profound consequences on ecosystem function.

Disentangling the relationship between shrub vegetation and ground-dwelling arthropods at multiple levels of taxonomic resolution is essential to developing a suitable management strategy for the conservation of shrub-associated arthropod biodiversity in shrubland ecosystems. Using Gobi desert (dominated by shrub species Nitraria sphaerocarpa and Reaumuria soongorica) occurring widely in inland arid areas of northwest China as a model system, we sampled ground-dwelling arthropods by pitfall trapping method under canopies of both shrubs and in intershrub bare areas during spring, summer and autumn. Our aim was to determine whether the presence and species identity of shrubs influence the distribution of ground-dwelling arthropods and whether the influence of shrub presence and species identity differs among trophic and taxonomic groups. At the community level, total arthropod abundance and species richness were significantly greater under shrubs than in intershrub bare habitats, whereas more arthropods were captured under N. sphaerocarpa than under R. soongorica. At the trophic group level, the abundance of predator and decomposer arthropods was significantly greater under shrubs than in intershrub bare habitats, whereas herbivore and decomposer arthropods were more abundant under N. sphaerocarpa than under R. soongorica. At the family level, the abundance of Carabidae, Gnaphosidae, Karschiidae, Tenebrionidae and Thomisidae was consistently much greater under shrubs than in intershrub bare habitats, whereas that of Formicidae, Philodromidae and Tettigoniidae did not differ between the shrub microhabitats and the intershrub bare habitats. However, the abundance of Curculionidae under R. soongorica and the abundance of Geotrupidae under N. sphaerocarpa were significantly lower than that in intershrub bare habitats. N. sphaerocarpa was commonly preferred by arthropods in the families of Curculionidae and Tenebrionidae, whereas R. soongorica was commonly preferred by arthropods in the family Geotrupidae, but shrub species identity did not affect the abundance of the remaining families. Our results suggest that shrubs and species identity play important roles in structuring ground-dwelling arthropod communities, but the response of arthropods differed among trophic or taxonomic groups. This study may have important implications for the conservation of invertebrate biodiversity in Gobi desert ecosystems.

In shrubland ecosystems, shrubs as ecosystem engineers play an important role in structuring ground beetle communities. However, the influence of shrub vegetation on the distribution and diversity of ground beetles remains unknown in Gobi desert, northwest China, where shrubland is a major biome type. Using Gobi shrubland dominated by shrub species Nitraria sphaerocarpa and Reaumuria soongorica as a model system, we sampled ground beetle communities using a pitfall trapping method under canopies of both shrubs and in intershrub bare areas during spring, summer and autumn corresponding to the main period of beetle activity. Simultaneously, physical environment of the three microhabitats and plant characteristics of both shrubs were measured. We determined whether shrubs and species identity influence ground beetle distribution and diversity patterns and whether the response of beetles to the presence and species of shrubs is consistent across species. At the community level, total beetle abundance and species richness were significantly greater under shrubs than in intershrub bare areas, whereas more beetles were captured under N. sphaerocarpa than under R. soongorica. At the population level, eight dominant beetle species responded differently to the presence and species of shrubs. The abundance of Anatolica sp., Carabus sp., Cyphogenia chinensis, Microdera sp. and Sternoplax setosa was consistently much greater under shrubs than in intershrub bare areas, whereas the abundance of Blaps gobiensis, Lethrus apterus and Pterocoma reitteri under shrubs was similar to that in intershrub bare areas. The shrub N. sphaerocarpa was commonly preferred by Anatolica sp., C. chinensis and S. setosa, whereas the shrub R. soongorica was commonly preferred by L. apterus, but the abundance of B. gobiensis, Carabus sp., Microdera sp. and P. reitteri was unaffected by shrub species. Differences in the abundance, species richness and composition of ground beetles among microhabitat types were largely related to among-microhabitat differences in the physical environment and resource availability. Our results suggest that shrubs and species identity play key roles in structuring ground beetle communities, but their influence differed between species. This study emphasizes the importance of protecting shrub habitats for the maintenances of beetle biodiversity in this Gobi desert ecosystem.

Water user association(WUA) was considered as an effective means of solving water shortage problem. Famers’ enthusiasms of participation in WUA were not high in inland arid regions of northwest China. The research sought factors influencing farmers’ behavioural attitudes to WUA. We took the middle basin of Heihe River as study area, by an empirical investigating method with questionnaire, used the analysis of logistic regression model, to explore factors affecting farmers’ behaviours toward WUA. The emperical results showed that following factors were most important for farmers to join a WUA: (1) The farmers personal characteristics such as education, being a village cadre, and health status; (2) The family factor was the decision making of planting structure; (3) The natural endowment factors were area of water right and land patch. Finally, recommendations were put forward to provide possible references for water authorities.

For decades, arid desert ecosystems in northwest China, covering one-fourth the country’s land surface, have experienced a rapid decline in plant species diversity, productivity and soil carbon stock owing to degradation by overgrazing. In this study, plant community composition, diversity and productivity, as well as soil carbon (C) and nitrogen (N) stocks, were monitored over 26 years from 1981 to 2006 in a severely degraded Haloxylon ammodendron-dominated shrubland where livestock densities were reduced from 4–5 to 1–2 dry sheep equivalent ha-1. The objective was to assess long-term grazing effects on vegetation and soil C and N accumulation dynamics. Results showed that the reduction of grazing pressure significantly increased vegetation cover, plant diversity and productivity, resulting primarily from an increase in livestock-preferred species. Controlled grazing also led to marked increases in soil C and N stocks in the top 30 cm of soil. This increase was strongly associated with increased plant species richness, vegetation cover and biomass production. Averaged over 26 years, soil C and N accumulated at rates of 89.9 g C and 8.4 g N m-2 year-1, respectively, but rates of C and N accumulation varied greatly at different time periods. The greatest species regeneration occurred in the first 8 years, but the largest C and N accumulation took place during years 9–18, with a time-lag in response to changes in vegetation. Our results provide insights into the long-term recovery patterns of different ecosystem components from the influence of prolonged overgrazing disturbance that cannot be inferred from a short-term study. The findings are important for assessing the resilience of these livestock-disturbed desert ecosystems and developing a more effective strategy for the management of this important biome from a long-term perspective.

To evaluate the long-term effects of reforestation types on soil erosion on degraded land, vegetation and soil properties under conventional sloping farmland (CSF) and three different reforestation types including a Pinus massoniana secondary forest (PSF), an Eucommia ulmoides artificial economic forest (EEF) and a natural succession type forest (NST), were investigated at runoff plot scale over a six-year period in a red soil region of southern China. One hundred and thirty erosive rainfall events generating runoff in plots were grouped into four rainfall types by means of K-mean clustering method. Erosive rainfall type I is the dominant rainfall type. The amount of runoff and the soil loss under erosive rainfall type III were the most, followed by rain-fall type II, IV and I. Compared with CSF treatment, reforestation treatments decreased the average annual runoff depth and the soil loss by 25.5%-61.8% and 93.9%-96.2% during the study period respectively. Meanwhile, runoff depth at PSF and EEF treatments was significantly lower than that in NST treatment, but no significant difference existed in soil erosion modulus among the three reforestation treatments. This is mainly due to the improved vegetation properties (i.e., vegetation coverage, biomass of above- and below-ground and litter-fall mass) and soil properties (i.e., bulk density, total porosity, infiltration rate and organic carbon content) in the three reforestation treatments compared to CSF treatment. The PSF and EEF are recommended as the preferred reforestation types to control runoff and soil erosion in the red soil region of southern China, with the NST potentially being used as an important supplement.

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.

Question: Understanding the mechanisms underlying how habitat degradation, topography and rainfall variability interactively affect seed distribution and seedling recruitment is crucial for explaining plant community patterns and dynamics. Interactions between these major factors were studied together in a semiarid sand dune grassland. Location: Eastern Inner Mongolia, China. Methods: The study system used four sites of fixed, semifixed, semishifting and shifting sand dune grasslands, representing a gradient of habitat degradation. We investigated the density of germinable seeds deposited in the top 5 cm of soil and in situ seedling emergence (number of seedlings emerging early in the growing season) and establishment (number of plants recruited at the end of the growing season) at three topographic positions (dune top, windward and leeward sides) within each site over 2 years that differed in rainfall. Habitat characteristics (i.e. vegetation cover, plant species composition and diversity, soil moisture and nutrient availability and soil erodibility) of the four sites were also measured. Results: Habitat degradation (i.e. decreased vegetation cover and enhanced wind erosion rate) significantly reduced the size of the germinable soil seed bank. On average, germinable seed number from the high-vegetation cover fixed dune was 36-fold larger than the low-vegetation cover shifting dune, and eight- and two-fold larger, respectively, than the semishifting and semifixed dunes with intermediate vegetation cover. We observed within-habitat variability in seed distribution, but among-topographic position variation differed among habitats. Seedling recruitment showed large between-year, and among- and within-habitat variability, but these variations varied significantly depending on the response variables evaluated (i.e. initial seedling density, final plant density, emergence rate and recruitment rate). Path analysis revealed complex density-dependent positive and negative, direct and indirect effects of germinable seed density and initial seedling density on recruitment, but the relative importance of these density-dependent effects varied depending on habitat type and rainfall availability. Conclusion: Our results suggest that habitat degradation, microtopography and rainfall availability interact in shaping sand dune seed bank and plant community recruitment patterns and dynamics. Their effects were mainly mediated through changes in both the biotic and abiotic environment during the process of habitat deterioration.

In a natural population of the perennial semi-shrub Artemisia halodendron in a shifting sandy habitat in the Horqin Desert of eastern Inner Mongolia, six isolated adult A. halodendron individuals of similar canopy size were chosen as target plants. The density of seeds in the top 5 cm soil depth around shrubs was measured using transects aligned to the four main wind directions and at different distances from the shrub base on both the windward and leeward sides. The effects of shrub presence on seed distribution of four co-occurring grasses were examined by linking seed distribution to seed traits. Of the four species, Setaris viridis and Eragrostis pilosa had small but similar seed mass, while Chloris virgata and Aristida adscensionis had large but similar seed mass. The species were grouped into two cohorts: small-seeded vs. large-seeded cohorts, and shrub presence effects on seed distribution of both cohorts were examined. We found marked difference in the seed distribution pattern among species, especially between the small-seeded and large-seeded cohorts. The small-seeded cohort had significantly higher seed accumulation on the windward than the leeward sides in the most and least prevailing wind directions and much higher seed accumulation on the leeward than the windward sides in the second and third most prevailing wind directions, while opposite patterns occurred in the large-seeded cohort. Four species also showed marked variation in the seed distribution pattern among transects and between windward and leeward sides of each transect. This study provided further evidence that shrubs embedded in a matrix of herbaceous plants is a key cause of spatial heterogeneity in seed availability of herbaceous species. However, seed distribution responses to the presence of shrubs will vary with species as well as with wind direction, sampling position (windward vs. leeward sides of the shrub) and distance from the shrub.

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.

Question: Do shrubs influence the spatial pattern of soil seed banks in herbaceous vegetation and are these effects influenced by wind direction, sampling position (windward vs leeward sides of the shrub) and distance from the shrub? Location: Horqin desert in eastern Inner Mongolia, China. Methods: A pioneer shrub, Artemisia halodendron, occurring in a mobile sandy habitat was used as a case study. Species composition and abundance of the seed bank and established herbaceous vegetation around six target shrubs were sampled along transects aligned to the four main wind directions and at 0.5, 1, 2, 3, 4.5 and 6 m from the shrub base on both windward and leeward sides of a transect. Results: The presence of shrubs significantly modified the spatial pattern of seed deposition, but effects varied with wind direction, sampling position and distance from the shrub. More seeds were deposited on the leeward side than on the windward sides in all four transects, especially on transects with the most preva...

The shrub Artemisia halodendron and the annual herb Agriophyllum squarrosum, which typically co-occur in a mobile sandy habitat in eastern inner Mongolia, China, were used to determine whether the presence of A. halodendron influences seed deposition and seedling recruitment of A. squarrosum under and around the shrub canopy in relation to wind direction, sampling position (windward vs. leeward sides) and distance from the shrub. The numbers of seeds deposited, seedlings emerged, and individuals recruited of A. squarrosum around adult shrubs were sampled along four transects aligned to the four main wind directions at 0.5, 1, 2, 3, 4.5 and 6 m from the shrub base on both windward and leeward sides of each transect. Spatial pattern of seed deposition was strongly altered by the presence of shrubs, but effects varied with wind direction, sampling position and distance from shrubs. Significantly more seeds tended to deposit on the leeward than on the windward sides in all four transects, with the exception of transects along the least prevailing wind direction. The presence of shrubs as nursing plants caused a marked variation in seed deposition across sampling locations, but this effect was detected only in the most, secondary and third most prevailing wind directions, but not in the least prevailing wind direction. In general, the shrub’s influence was within a 2 m radius from the shrub, despite some differences among transects. Although seed bank density had no direct effect on A. squarrosum recruitment patterns, it contributed to the observed variation in recruitment indirectly through density-dependent emergence of seedlings. Our findings provide further evidence of shrubs as a source of spatial heterogeneity in seed availability and thereby a common factor determining population dynamics of understorey herbaceous species.

Pollution caused by traffic activities is increasingly becoming a great threat to urban environmental quality and human health in many municipalities in Northwest China. The Sophora japonica L., a native tree species occurring widely in many regions of Northwest China, was used as a case study to assess the potential effects of traffic pollution on heavy metal accumulation in leaves of S. japonica trees and associated soils. Fifty-four leaf samples and 41 relevant soil samples (0–10 cm) were collected systematically along main trunk roads and at parks distant from main trunk roads in the city of Lanzhou, Northwest China, respectively. Traffic pollution has resulted in significant accumulation of heavy metals in both the roadside leaves and soils, but the pattern and level of accumulation varied remarkably between elements. The nine elements examined can be classified into three groups relating to their responses to traffic pollution. The first group, including Zn, Cd, Hg, Pb and Cr, showed greater accumul...

Overgrazing by increasing numbers of livestock in the Horqin Sandy Land of Inner Mongolia, China, has led to extensive degradation of the region's sandy steppes. Degraded grasslands are generally classified into four main types: fixed (least degradation), semi-fixed (light degradation), semi-shifting (moderate degradation) and shifting (severe degradation) sandy lands, representing four stages of degradation development. An experiment was conducted in the Horqin Sandy Land to investigate changes in intensity of wind erosion at different stages of degradation development in sandy grasslands and determine the extent to which surface wind erosion was affected by surface-related soil and vegetation factors through their effects on surface roughness length and wind regimes. Daily wind erosion rate was monitored at four sites of degraded grassland over an erosive period from 1 April to 10 June in 2001. Soil and vegetation properties for these sites were also measured twice: one in mid-April prior to the establishment of vegetation and again in mid-June after the establishment of vegetation. Relationships between surface roughness length and soil and vegetation variables were examined at each of the two stages of vegetation development. This study shows striking differences in the intensity of surface wind erosion among sites. The daily wind erosion rate in the fixed sandy land was, on average, only about 1/5 of the rate in the semi-fixed sandy land, 1/14 of the rate in the semi-shifting sandy land and 1/47 of the rate in the shifting sandy land suggesting a much higher resistance of the fixed sandy land to wind erosion compared to other sites. Differences in rate of wind erosion between sites were attributed to between-site differences in soil and vegetation properties that exerted significant effects on wind regimes by altering surface roughness length. At the pre-establishment stage of vegetation, surface roughness length was determined by a combination of litter amount on the ground, soil surface hardness and soil moisture content, with litter amount explaining the greatest proportion of the variation. At the post-establishment stage of vegetation, the development of the surface roughness effects was mainly governed by vegetation characteristics (vegetation cover in particular), while the effects of soil surface hardness and soil moisture on surface roughness length are likely to be masked by vegetation effects. The findings suggest that better management practices of restoring vegetation in degraded grasslands are required to reduce soil erosion losses and achieve a sustainable livestock production in the Horqin Sandy Land, an ecologically fragile sandy land ecosystem.

The perennial chenopod sub-shrub Artemisia halodendron Turcz. ex Bess. is endemic to the semi-fixed and mobile sand dunes in Inner Mongolia of northern China and is an important sand-stabilizing plant. A. halodendron can persist through either sexual reproduction (seedling recruitment) or vegetative propagation. However, it is not known if there are differences in patterns of reproductive allocation in A. halodendron inhabiting semi-fixed and mobile habitats. To characterize this, a test of field measurements was conducted on two typical semi-fixed and mobile sand dune habitats. In each habitat, 120 individual A. halodendron plants were randomly sampled at the time of seed production to examine changes in some reproductive characters including the number of flowering shoots, dry weight of flowering shoots, dry weight per flowering shoot, dry weight of seed, and reproductive effort (RE = seed dry weight/total above-ground dry weight) between habitats. Although total above-ground dry weight and dry weight of vegetative biomass were similar between habitats, plants inhabiting the less eroded semi-fixed habitat produced more flowering shoots, greater dry weight of flowering shoots, dry weight of seed and RE than those inhabiting the more eroded mobile habitat. This suggests that sexual reproduction is relatively favored by plants from the semi-fixed habitat, whereas vegetative propagation is favored by plants from the mobile habitat. The allocation of resources to reproduction was size-dependent and specific to habitats sampled. Reproductive biomass and the number of flowering shoots per plant increased with increasing vegetative biomass, with plants in the semi-fixed habitat producing more flowering shoots and greater reproductive biomass than plants in the mobile habitat. Plant size did not influence RE, indicating that allocation of resources to reproduction appeared to be a constant proportion across all plant sizes sampled.

� Background and Aims Artemisia halodendron is a native sub-shrub that occurs mainly in moving and semi-fixed sandy lands in Inner Mongolia, China. Information on the spatial patterns of wind-dispersed seed deposition and seedling recruitment of A. halodendron inhabiting moving sandy lands is very limited. The aim of this study was to examine wind-dispersed seed deposition patterns and post-dispersal recruitment of A. halodendron seedlings. � Methods The spatial patterns of wind-dispersed seed deposition and seedling recruitment of A. halodendron were examined by investigating the numbers of deposited seeds, emerged and surviving seedlings using sampling points at a range of distances from the parent plant in eight compass directions for two consecutive growing seasons. � Key Results Wind-dispersed seed deposition showed considerable variation between directions and years. Wind transported A. halodendron seeds only a few meters away from the parent plant in all eight directions. Seedling emergence and establishment also showed between-direction and between-year variability, but the spatial pattern of seedling distribution differed from that of seed deposition. Only a very small fraction (

An experiment was implemented in 1997 in the Horqin Sandy Land of Inner Mongolia, China to evaluate the effects of different measures of stabilizing sand dune on vegetation restoration. The measures included (1) building corn straw fencing, (2) placing wheat straw checkerboard, and (3) planting Artemisia halodendron on the dunes. The preliminary results from the first 2 years (1998 and 1999) demonstrate that all the three measures could result in significant increases of plant species diversity, vegetation cover, above-ground biomass and below-ground biomass on the moving sand dunes relative to the naturally restored plot (without taking any measures). However, both placing wheat straw checkerboard and planting Artemisia halodendron performed best and thus are considered to be the most promising techniques for the restoration of vegetation on desertified sandy lands in this area.

In the Horqin Sandy Land of eastern Inner Mongolia in northern China, wind erosion in farmland is very common in a period from thawing of frozen surface soil in mid-March to sowing of crops in the end of April, largely because of dry and windy weather. However, little is known about the magnitude of wind erosion and associated nutrient losses due to erosion and the addition of nutrients by airborne dust deposition to farmlands during this period. A field experiment was conducted in an Entisol with sand origin under corn ( Zea mays L.) production to investigate daily changes in wind speed and wind erosion intensity (as measured by soil transport rate) over a period from 20 March to 30 April 2001. We also measured daily rates of airborne dust deposition during the spring seasons with the high frequency of dust storm occurrence. The rates of soil transport by wind varied greatly from 13.2 to 1254.1 kg ha −1 per day, averaging 232.1 kg ha −1 per day, largely attributable to great variation between days in wind speed within the study period. The potential losses of nutrients through wind erosion were 0.26–24.95 kg ha −1 per day (averaging 4.62 kg ha −1 per day) in organic matter, 0.02–1.64 kg ha −1 per day (averaging 0.31 kg ha −1 per day) in nitrogen and 0.01–0.7 kg ha −1 per day (averaging 0.13 kg ha −1 per day) in phosphorus. The mean rates of airborne dust deposition ranged from 4.0 to 48.9 kg ha −1 per day, averaging 19.9 kg ha −1 per day, during the spring seasons. The potential addition of organic matter, nitrogen and phosphorus by dust input to the experimental field was, on average, 0.54, 0.04 and 0.02 kg ha −1 per day, respectively. Although the addition was a fraction of the losses due to erosion, nevertheless, dust input in the spring seasons is one of the major suppliers of soil nutrition. The fact that the addition of nutrients by dust is about 1/10 of the losses of soil nutrients through wind erosion suggests that developing and adopting more effective management practices to reduce soil erosion losses and to improve soil fertility are crucial to achieve a sustainable agricultural system in a fragile, semiarid sandy land environment.