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Vegetation restoration in dryland regions may be a powerful way to control desertification and promote local habitat recovery. In these artificial revegetation systems, ecosystem processes and functioning are strongly determined by nitrogen (N) availability, while soil inorganic N (SIN) is the major available N form and is absorbed as a main N source for plants. However, SIN dynamics, their influencing factors, and their relative importance to the ecosystem of these N‐limited systems are not well understood. A field investigation was conducted to examine the monthly variations in SIN and its response to planting age and vegetation type in a typical artificial sand‐fixing system in northwestern China. The SIN content in topsoil (0–20 cm) during the growing season ranged from 7.10 to 95.65 mg kg−1, with a mean value of 27.14 mg kg−1. Soil nitrate N had a dominant role in determining SIN monthly dynamics, which showed a fluctuating trend with two peak values in early July and late August. SIN showed a significant increasing trend with the planting age of sand‐fixing vegetation, and it was highest for Nitraria sphaerocarpa (55.66 ± 5.76 mg kg−1), followed by Haloxylon ammodendron (29.81 ± 3.47 mg kg−1) and interspace (11.39 ± 1.13 mg kg−1). SIN displayed a hump‐shaped relationship with air temperature (R2 = 0.96, p < 0.01) and had a maximum at 19.88°C. The change rate of SIN was positively correlated with accumulated precipitation (R2 = 0.99, p < 0.05). SIN was correlated significantly with soil organic carbon (SOC), total nitrogen (TN), and soil clay content. Our results revealed that climatic (air temperature and precipitation), abiotic (soil texture), plant (planting age and vegetation type), and nutrient‐related (SOC and TN) factors regulate SIN dynamics in artificial sand‐fixing vegetation systems. Climate was the predominant factor affecting soil ammonium N, and soil nutrients (SOC and TN) were the predominant factor affecting soil nitrate N. Therefore, these factors should be integrated into optimizing regional vegetation establishment and improving ecosystem management practices in sand‐fixing lands. [ABSTRACT FROM AUTHOR]

Summary: Background: The relationship between sugar‐free beverage (SFB) intake and childhood obesity among Chinese children is unknown. Objectives: To describe the status of SFB consumption among children and adolescents in China and assess the association between SFB intake and different types of obesity. Methods: The study was based on the baseline data of an ongoing cohort project named Evaluation and Monitoring on School‐based Nutrition and Growth in Shenzhen (EMSNGS). Food frequency questionnaires were used to collect information on SFB consumption in 3227 students aged 9–17. Physical and clinical examinations were conducted by trained investigators and clinicians. Multivariable binary logistic regression models were performed to assess the association between SFB intake and general obesity, overweight/obesity, abdominal obesity, metabolically unhealthy overweight (MUOW)/metabolically unhealthy obesity (MUO). Results: The median age of the participants was 13.28 years. Among the participants, 55.2% were boys, and 66.1% were adolescents. The median SFB consumption was 16.67 mL/d. After adjusting for potential confounding factors, each 100 mL increase in daily SFB intake was associated with an increased risk of overweight/obesity (OR = 1.14; 95%CI: 1.06–1.23), abdominal obesity (OR = 1.12; 95%CI: 1.03–1.23), and MUOW/MUO (OR = 1.12; 95%CI: 1.02–1.21), respectively. Stratified analyses showed that family income may have an impact on the association between SFB intake and overweight/obesity (P for interaction = 0.021) and abdominal obesity (P for interaction = 0.031). Conclusion: SFB intake was positively associated with childhood obesity in Chinese children, particularly among individuals with high‐income families. [ABSTRACT FROM AUTHOR]

Hydrological connectivity (HC) is a useful framework for understanding hydrological responses to landscape changes. We present herein a novel model (SOFAR) for utility‐scale solar farms (USFs), combining modules of soil moisture dynamics, roof effects of photovoltaic panels (PVs), vegetation growth and landform evolution. By augmenting the model with a DEM‐based HC index, we investigate hydrological behaviors following the construction of a USF in China's Loess Hilly Region. Nine scenarios are designed, to explore the effects of co‐evolving ecohydrology and landscape on soil erosion and HC in USFs deployed in different climates and terrains, by altering the annual precipitation, rainfall frequency, and ground slope. Our results show that the USF considerably increased runoff (99.18%–154.26%) during its operational period, and soil erosion rate (21.4%–74.84% and 25.35%–76.18%) and HC (0.08%–0.26% and 0.47%–0.91%) throughout construction and operational periods, respectively. The highest erosion rates were detected in the PV installation zones and in the areas close to the river channel. We prove the hypothesis that HC is a critical indicator for sediment yield in a USF, and thus the long‐term responses of soil erosion to USF installation and development can be explained in terms of HC. We conclude that USFs may increase soil erosion, mainly by increasing local HC and runoff, and higher background HC may in turn further aggravate the effects of USFs on soil erosion. Our results underscore the importance of including landscape ecohydrologic and geomorphic feedbacks, to improve the environmental impact assessment of USFs. Key Points: Precipitation and relief amplitude are major controlling factors for soil erosion in utility‐scale solar farms in hilly areasUtility‐scale solar farms may increase soil erosion, mainly by increasing runoff and local hydrological connectivityHigher background hydrological connectivity could aggravate the effects of utility‐scale solar farms on soil erosion [ABSTRACT FROM AUTHOR]

Current and previous studies have extensively studied the physiological and ecological consequences of genome size (GS) on plants because of the limiting effect of GS on cell size. However, it is still obscure whether such limiting effect could be shifted by environmental pressures, or not. Here, we compiled a global dataset comprised of GS, xylem vessel diameter (Vdia), xylem hydraulic conductivity (KS), P50 (xylem water potential at the loss of 50% maximum KS), and climate factors of 251 phylogeny and habitat divergent species from 59 families. The results showed that GS could limit the Vdia of the species from the same family sampled in the similar climate conditions. But the expected positive relationship between GS and Vdia became uncertain and even negative across different environmental conditions. Vdia was strongly positively coordinated with mean annual temperature (MAT), mean annual precipitation (MAP), and potential evapotranspiration (PET). Furthermore, Vdia as the anatomic foundation of plant hydraulic performance was strongly positively coordinated with KS and negatively coordinated with −P50. The strong environmental selection on KS and P50 explained the concerted regulation of Vdia by environmental factors. The findings revealed the combined regulation of GS and environmental pressures on xylem cell size and thus affected plant eco‐physiological performance. The shifted cell size limiting effect of GS by environmental factors manifests plants great plasticity under changed environmental conditions. [ABSTRACT FROM AUTHOR]

The dynamics of soil organic carbon (SOC) play a critical role in modulating global warming. However, the long‐term spatiotemporal changes of SOC at large scale, and the impacts of driving forces remain unclear. In this study, we investigated the dynamics of SOC in different soil layers across China through the1980s to 2010s using a machine learning approach and quantified the impacts of the key factors based on factorial simulation experiments.Our results showed that the latest (2000–2014) SOC stock in the first meter soil (SOC100) was 80.68 ± 3.49 Pg C, of which 42.6% was stored in the top 20 cm, sequestrating carbon with a rate of 30.80 ± 12.37 g C m−2 yr−1since the 1980s. Our experiments focusing on the recent two periods (2000s and 2010s) revealed that climate change exerted the largest relative contributions to SOC dynamics in both layers and warming or drying can result in SOC loss. However, the influence of climate change weakened with soil depth, while the opposite for vegetation growth. Relationships between SOC and forest canopy height further confirmed this strengthened impact of vegetation with soil depth and highlighted the carbon sink function of deep soil in mature forest. Moreover, our estimates suggested that SOC dynamics in 71% of topsoil were controlled by climate change and its coupled influence with environmental variation (CE). Meanwhile, CE and the combined influence of climate change and vegetation growth dominated the SOC dynamics in 82.05% of the first meter soil. Additionally, the national cropland topsoil organic carbon increased with a rate of 23.6 ± 7.6 g C m−2 yr−1since the 1980s, and the widely applied nitrogenous fertilizer was a key stimulus. Overall, our study extended the knowledge about the dynamics of SOC and deepened our understanding about the impacts of the primary factors. [ABSTRACT FROM AUTHOR]

Despite the recognition of positive interactions as an important driver of species coexistence and community structure, the underlying mechanism of how facilitation affects assembly processes along stress gradients is poorly explored. Understanding the responses of functional diversity to benefactor species at the extreme end of the stress gradient could provide valuable insight about facilitation‐involved assembly mechanisms and contribute to the predictions of species coexistence under climate change.In the drought‐stressed community in the Badain‐Jaran Desert, the responses of the local community to the nurse shrub species Calligonum mongolicum Turcz. were evaluated using hierarchical Bayesian models. For the 3‐year experiment, summer rainfall in each year formed a natural gradient of drought stress. To evaluate the shrub's effects on the assembly process along that gradient, individual samples were collected in pairwise under‐shrub and open habitats, and four traits related to stress tolerance and resource acquisition were measured simultaneously.Under moderate drought stress, we observed shifting community‐weighted means, broadening ranges and reducing overlaps of functional traits under shrubs. These effects were partly driven by a distinct microenvironment created by shrub plants, in particular the improvement and heterogeneity of soil moisture conditions. However, this influence on trait distributions was strongly dependent on the environmental context, and generally disappeared as drought stress shifted towards its driest end, almost in line with the decreased positive interaction assessed by plant density and species diversity.This study focused on water‐limited community that lies at the driest end of drought gradient and confirmed that facilitation can drive the assembly process through both environmental filtering and niche differentiation. More importantly, these assembly mechanisms are proven to become less efficient under extreme drought stress, which may suggest the occasionally disappearing role of benefactor plants on community assembly and an increasing risk of biodiversity loss in the context of climate change. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

The characteristics of soil macropores and water infiltration are closely connected to the growth of plant roots and their root zone environment. However, it is unclear how the root zone environment of oasis farmlands regulates the development of soil macropores and water flow in hyper‐arid regions. The objective of this study was to investigate soil macropores and their effect on water flow under irrigated oasis farmlands using a combination of X‐ray computed tomography (CT) and dye tracer. It was hypothesized that the integration of CT and dye tracer could clearly reveal preferential flow through biopores and large pores of oasis soils. A helical medical CT scanner was used to quantify more information about soil macropores in the root zone, along with an in situ single‐ring dye infiltration experiment to reveal water flow in three different oasis farmlands (piedmont oasis farmland, marginal oasis farmland, and old oasis farmland). Soil macroporosity was 0.44% under crop rows, while soil macroporosity in the interrows was only 0.30% across the oasis farmlands. Biopores contributed 73% of the volume of the total macropores under crop rows. The stable infiltration rate in the interrows was 0.3 mm min−1, which was significantly (p < 0.05) less than that under crop rows (0.7 mm min−1). Water flow under crop rows were mainly transported in biopores and large pores. The contribution of macropores to preferential flow under crop rows was 4.8 times larger than interrows. The integration of CT and dye tracer was a more holistic technique, which adequately revealed that oases had preferential flow affected by biopores and large pores, resulting in higher solute and contaminant transport. Key Points: Soil macropores and preferential flow affected by crop roots were investigated in hyper‐arid regions.The integration of CT and dye tracer adequately identified preferential flowpaths of oasis soils.Biopores were larger under crop rows than interrows.Preferential flow transported in biopores and large soil pores under crop rows. [ABSTRACT FROM AUTHOR]

Knowledge of exchanges of energy and water over terrestrial surfaces is the first step towards understand the ecohydrological mechanisms, particularly in water‐limited ecosystems in dryland environments. However, patterns of energy exchange and evapotranspiration (ET) are not well understood in the oasis‐desert ecotone, which plays an important role in protecting oases against the threat of desertification in arid regions of northwestern China. Here, the continuous measurements of surface energy fluxes were made using eddy covariance in conjunction with auxiliary measurements for 2 years (2014–2015) in an oasis‐desert ecotone mainly covered by phreatophyte shrubs Haloxylon ammodendron, Nitraria tangutorum/sphaerocarpa, and Calligonum mongolicum in arid northwestern China. Based on the collated data for 2 years, statistical analysis on a 30‐min time scale indicated that approximately 50% of daytime net radiation (Rn) in the ecotone was dissipated as H on average, and one‐third of Rn was consumed by soil heat flux (G). Only 9% of Rn was consumed for latent heat flux (λE), which peaked in summer (21% in 2014 and 16% in 2015), corresponding to the highest rainfall season. Daily mean ET was approximately 1 mm days−1 during the growing season of the shrub species. Accumulated annual ET was 195 and 181 mm in 2014 and 2015, respectively, exceeding the corresponding precipitation (P) by approximately 87 and 77 mm, indicating that groundwater may be another important source of water for ET in the ecotone aside from rainfall. Results within provide valuable insights into the mechanisms responsible for sustaining energy and water balance in the ecotone, a potentially groundwater‐dependent ecosystem. These results also offer a foremost ecohydrological implication for water and land resources management and ecotone conservation, such as avoiding heavy groundwater pumping for extensive agricultural irrigation use to sustain groundwater availability for these shrub species in the ecotone. [ABSTRACT FROM AUTHOR]

Desert pavements (DPs) are critical for maintaining ecological stability and promoting near‐surface hydrological cycling in arid regions. However, few studies have focused on eco‐hydrological processes of DPs in the ecological systems of fluvial fans. Although DP surfaces appear to be barren and flat, we found that the surfaces are characterized by surface mosaic patterns of desert pavement (mosaic DP) and bare ground (mosaic BG). We investigated the effects of mosaic DP on water infiltration and vegetation distribution at six sites in fluvial fans (one on a hillside and five within the sectors of fans) along a southwest belt transect in northern Linze County, in the central Hexi Corridor (China). We found significant differences in mosaic DP between the hillside and sector sites in terms of pavement thickness and vesicular horizon thickness (Av thickness), particle composition, and bulk density, although significant differences were absent for mass soil water content, gravel coverage, and surface gravel size. The mosaic DP inhibited water infiltration by the pavement layer, where the sorptivity (S), initial infiltration rate (iint), steady‐state infiltration rate (isat) and infiltration time (T) averaged 1.19 cm/min‐0.5, 0.64 cm/min, 0.13 cm/min and 12.76 min, respectively. Where the pavement layer was scalped, the S, iint, and isat increased by 0.27 cm/min‐0.5, 0.52 cm/min, and 0.40 cm/min, respectively, and the T reduced by 7.42 min. Water infiltration was mainly controlled by the pavement layer thickness (+), Av thickness (−), surface gravel coverage (−), fine earth (+) and fine gravel (−) in the pavement layer. The DP surfaces only had a sparse covering of shrubs, but an abundance of herbs. Few shrubs were present on the mosaic DP, but a greater number of shrubs and herbs grew on the mosaic BG. It can be concluded that DPs can maintain vegetation stability for different surface mosaic patterns. This study deepens our understanding of the eco‐hydrological cycle of DP landscapes in arid regions. [ABSTRACT FROM AUTHOR]

Scutellarin, an active flavone extracted from Erigeron breviscapus, is known to exhibit antitumour activity in many cancers. However, the effects of Scutellarin on osteosarcoma remain unclear. In this study, we found that Scutellarin suppressed osteosarcoma cell growth, induced cell apoptosis and inhibited tumorigenesis. Mechanistically, our data revealed that EGR1 was significantly increased under Scutellarin treatment. Increased EGR1 enhanced tumour‐suppressive effects of Scutellarin on osteosarcoma cells via transcriptionally downregulating LINC00857 expression. Additionally, we found that LINC00857 acted as a competitive endogenous RNA of miR‐150‐5p and inhibited the activity of miR‐150‐5p, which resulted in c‐Myc increase. Scutellarin could suppress c‐Myc protein levels through decreasing LINC00857 expression in osteosarcoma. Thus, these findings demonstrate that EGR1/ LINC00857/miR‐150‐5p/c‐Myc axis plays a key role in promoting anticancer effects of Scutellarin and Scutellarin might have potential clinical implication in osteosarcoma clinical treatment. [ABSTRACT FROM AUTHOR]

Surface soil hydraulic properties play critical roles in controlling water infiltration, evaporation, and soil water storage, in‐turn affecting the evolution of soil pore structure in cultivated desert soils of arid areas. The variability in soil pores and hydraulic properties caused by conversion of native semidesert soils to agroforestry use alters soil water storage and water budget in the desert–oasis ecotone. The objective of this study was to investigate that land use conversion alters surface soil hydraulic properties and enhances the contribution of soil macropores to water flow in the Linze desert–oasis ecoregion. Water infiltration and soil pores characteristics with nine replicates were measured using a disc tension infiltrometer across four habitat types (Haloxylon ammodendron shrublands, Populus gansuensis forests, Medicago sativa Linn grasslands, and Zea mays croplands) during the growing season. Soil properties and hydraulic conductivity characteristics clearly varied across the four habitat types. Saturated hydraulic conductivity was 0.177, 0.126, 0.118, and 0.031cm min−1 in the forest, grassland, shrubland, and cropland, respectively, with the corresponding average soil moisture being 7.6, 6.7, 0.9, and 19.2%. Clay content, bulk density, and initial soil moisture were the key soil physicochemical properties affecting saturated hydraulic conductivity (Ks). The macropores (> 0.5 mm in radius) accounted for 15–60% of total water flow, while 0.25–0.5 mm pores contributed to 12–24% across the four habitat types. The contribution of >0.5 mm pores to water flow in the forest was 3.3–4.0‐times greater than in shrubland and cropland, due to greater soil macroporosity (58 cm−3 cm3) and undisturbed soil pore structure. Land use conversion has a positive impact on soil properties, structure features, and soil hydraulic properties, and as a consequence, enhance the complexity of water exchange in the arid areas. [ABSTRACT FROM AUTHOR]

Preferential flow (PF)‐dominated soil structure is often considered a unique system consisting of micropores and macropores and thus supposed to provide dual‐pore filtering effects on hydrological signals, through which smoothing effects are likely to be stronger for matrix flow and weaker for PF via macropores. By using time series of hydrological signals (precipitation, canopy interception, throughfall, soil moisture, evapotranspiration, water storage in soil and groundwater, and catchment discharge) propagating through the Shale Hills Catchments and representative soil series, the filtering effects of the catchment and soil profiles were tested through the wavelet analysis. Typical filtering effects, that is, the characteristic of the role of soil and the groundwater table as a buffer, were observed from the wavelet spectrum, gradually smoothing off the precipitation signal. The hypothesized dual‐pore style filtering effects of the soil profile were also confirmed through the coherence spectra and phase differences, rendering them applicable for possible use as "fingerprints" of PF to infer subsurface flow features. We found that PF dominates the catchment's discharge response at the scales from 3 to 12 days, which contributes to the catchment discharge mainly as subsurface lateral flow at upper or middle soil horizons. Through subsurface PF pathways, even the hilltop is likely hydrologically connected to the valley floor, building connections with or making contributions to the catchment discharge. This study highlights the potential of wavelet analysis for retrieving and characterizing subsurface flow processes based on the revealed dual‐pore filtering effects of the soil system. Although some limitations and uncertainties still exist, we believe that wavelet methods provide a highly potential but underexplored approach to studying subsurface hydrology. Key Points: The dual‐pore filtering effects were confirmed in a small forested catchmentLateral preferential flow dominated the discharge response at scales of 3–12 daysWavelet analysis complements current methods of studying subsurface flow features [ABSTRACT FROM AUTHOR]

Succulent xerophytes (SX) and less succulent xerophytes (LSX) are able to accumulate inorganic ions and synthesize organic solutes (OS) to adapt to drought stress. Silicon (Si) is one of the five beneficial elements for plants and its importance to SX has been confirmed. In the study, the features of main osmolytes and Si were studied in SX and LSX species, and the coupling effects of inorganic ions were investigated in the SX H. ammodendron and LSX C. korshinskii. Results showed that SX and LSX had the common adaptive characteristic of preferentially accumulating inorganic ions rather than OS for drought resistance, and the total amount of osmotica in SX was 2.36‐times higher than that in the LSX. The greatest contribution to drought resistance was K+ (29.7%), the lowest was Na+ (2.4%) in LSX, while the greatest contribution was Na+ (41.7%), the total OS was the lowest (2.4%) in SX. The coupling effects of inorganic ions played vital important roles in drought resistance of the SX and LSX. The better coupling ratios of NaCl, NH4NO3, CaCl2, MgCl2 and Na2SiO3 in H. ammodendron were 20:5:20:40:10 and 40:10:60:10:7.5 (g kg−1 dry soil), and the better coupling ratios of KNO3, CaCl2, MgCl2 and K2SiO3 in C. korshinskii were 20:10:20:10 and 40:20:60:5 (g kg−1 dry soil). Findings suggested that the rational coupling of inorganic ions can be utilized as mineral compound fertilizers to restore and reconstruct degraded vegetations in semiarid areas. [ABSTRACT FROM AUTHOR]

The dynamics of the power electronic transformers (PETs) have brought great challenges to stability analysis of the AC/DC hybrid distribution network with PETs. In this study, a large disturbance stability analysis method is proposed for the AC/DC hybrid distribution network with PETs, based on the mixed potential function (MPF) theory. Firstly, the simple average models of the converters based on the controlled sources with the control links are presented to describe the dynamic characteristics of the AC/DC system, which are suitable for the MPF theory. Subsequently, the method of constructing the MPF for the non-linear links in PET is proposed to derive a stability criterion for the AC/DC hybrid distribution network. The effects of the AC and DC dynamic characteristics and the non-linear control links are both included in the criterion. Multiple scenarios of the faults or the large disturbances are used to investigate the effect of the stability criterion, and the results show that the stability state of the multi-PET distribution network could be reflected by the stability criterion under various large disturbances. Finally, the parameter-influence analysis method is proposed to improve the stability of the system. [ABSTRACT FROM AUTHOR]

Salt accumulation gradually changes the cycling of carbon (C), nitrogen (N), and phosphorus (P) and may even transform sinks into sources in arid wetlands. However, it's not clear how hydrochemical characteristics affect the wetland's source or sink function or how they affect C, N, and P cycling in arid regions. To clarify these relationships, we conducted field measurement in arid northern China. We simulated the variations of hydrochemical characteristics and the storage and stoichiometry of C, N, and P using the process‐based DeNitrification‐DeComposition (DNDC) and Hydrus‐1D models. The meteorological and hydrological processes had obvious characteristics of seasonal and interannual changes. The measured evapotranspiration averaged 660.23 and 587.94 mm year−1 in the saltmarsh and riparian wetlands, respectively. The soil showed a clear trend with higher SO42−, Na+, Ca2+, and Cl− fractions in comparison with lower Mg2+, K+, and HCO3− fractions, with the major ion and nutrient concentrations gradually decreasing with increasing depth in the soil. The major ion types had characteristics of Na+‐Ca2+‐SO42−‐Cl− in the saltmarsh wetland and riparian wetland. The storage of total C, N, and P were 372.72 ± 66.52 t C/hm2, 10.92 ± 2.59 t N/hm2, and 17.55 ± 1.54 t P/hm2 in the saltmarsh wetland versus 119.72 ± 27.88 t C/hm2, 4.38 ± 1.24 t N/hm2, and 13.17 ± 1.46 t P/hm2 in the riparian wetland. Therefore, wetland salinization in our study led to increased soil C, N, and P contents and storage and thereby enhanced the sink function of the wetlands. Key Points: We simulated the variations of hydrochemical characteristics and the storage and stoichiometry of C, N, and PThe model coupled the Hydrus‐1D and DNDC models to solve a drawback of hydrochemical simulationWe identified the mechanisms by which hydrochemical characteristics determine the transport and cycling of soil nutrient [ABSTRACT FROM AUTHOR]

Core Ideas: Deep drainage rates under young cropland in the desert‐oasis region were investigated.Deep drainage rates were estimated by a simulation approach based on deep soil moisture data.Annual deep drainage averaged 468 mm; the annual deep drainage coefficient averaged 43%. Deep drainage reduces agricultural water productivity under cropland recently converted from native desert soils (i.e., young cropland) and increases the risks of nutrient and pesticide leaching into groundwater in the desert‐oasis ecotone. However, the deep drainage rates under young cropland in these oasis environments remain unclear, especially for winter irrigation, a common practice in Northwest China. The objective of this study was to estimate the deep drainage rate using the HYDRUS‐1D model based on soil moisture data in the deep vadose zone. Soil moisture at depths ranging from 0 to 200 cm was measured using HydraProbe II soil sensors in maize (Zea mays L.) and wheat (Triticum aestivum L.) fields in 2015 and 2017, respectively. Using a novel simulation approach based on soil moisture data in the deep vadose zone, the HYDRUS‐1D model provided reliable estimates of deep drainage as confirmed by comparison with estimates from the soil water balance method and prior studies in the region. The annual deep drainage averaged 468 mm, and the annual deep drainage coefficient averaged 43% in the young croplands. The winter irrigation amount averaged 265 mm, and the deep drainage coefficient during winter averaged 21% in the young croplands. The sandy soil of the young cropland and inefficient irrigation scheduling are detrimental to water conservation, causing relatively large deep drainage losses and enhancing the risks of groundwater pollution. [ABSTRACT FROM AUTHOR]

The stress gradient hypothesis (SGH) predicts that the importance or intensity of competition and facilitation will change inversely along abiotic stress gradients. It was originally postulated that increasing environmental stress can induce a monotonic increase in facilitation. However, more recent models predicted that the relationship between severity and interaction exhibits a hump‐shaped pattern, in which positive interactions prevail under moderate stress but decline at the extreme ends of stress gradients. In the present study, we conducted a field experiment along a temporal rainfall gradient for five consecutive years, in order to investigate interactions in a shrub‐herbaceous plant community at the southern edge of the Badain Jaran Desert, and, more specifically, investigated the effects of Calligonum mongolicum, a dominant shrub species, on both abiotic environmental variables and the performance of sub‐canopy plant species. We found that shrubs can improve sub‐canopy water regimes, soil properties, plant biomass, density, cover, and richness and, more importantly, that the positive effect of shrubs on sub‐canopy soil moisture during the summer diminishes as rainfall decreases, a pattern that partly explains the collapse of the positive interaction between shrubs and their understory plants. These results provide empirical evidence that the positive effect of shrubs on understory plant communities in extreme arid environments may decline and become neutral with increasing drought stress. [ABSTRACT FROM AUTHOR]

Abstract: Macropore flow not only provides a fast pathway for water and solute transport and increases the risks of water and nutrient loss but also enhances soil aeration and groundwater recharge. However, macropore flow characteristics in irrigated oasis soils subject to continuous crop cultivation are poorly understood. This study was to investigate the effect of continuous cultivation on soil properties and macropore flow and to quantify the changes in macropore flow characteristics in an old oasis field (>50 years of cultivation, OOF), young oasis field (20 years, YOF), and adjacent uncultivated sandy area (0 year, USL) in Northwest China. Triplicate soil samples were collected from each site to investigate soil properties. Dye tracer experiments with also three replicates were conducted at each site. The degree of macropore flow (i.e., parameters of macropore flow) was highest at the OOF, intermediate at the YOF, and minimal at the USL. The macropore flow fraction (i.e., fraction of total infiltration flows through macropore flow pathways) at the OOF was 3.4 times greater than at the USL. The heterogeneous infiltration pattern at the OOF was dominated by macropore flow, while funnel flow was predominant at the USL. Long‐term irrigation with silt‐laden river water has increased silt + clay contents of the oasis soils. Irrigation and high‐input crop cultivation also increased organic matter. These changes in soil properties contributed to the interaggregate voids formation. The conversion of native desert soils to irrigated croplands increases the degree of macropore flow, which might enhance groundwater recharge in the desert‐oasis ecotone. [ABSTRACT FROM AUTHOR]

Premastication is thought to be an adaptive behavior in the introduction of complementary plant-bassed food to infants. It arouses controversy, however, because of the potential for transmitting saliva-born infectious diseases. The aim of this study was to explore whether premastication by healthy caregivers was associated with children's health and behavior. The data were collected as part of the Maternal and Infant Nutrition and Growth study. From 8 cities in China, 1341 pairs of infants/toddlers and their caregivers were recruited. An interviewer-administrated questionnaire collected data on sociodemographic characteristics, feeding behaviors, and self-reported health status. Anthropometric measurements were taken and blood samples were collected for analysis of hemoglobin levels. The overall prevalence of premastication was 26.9% and varies from 14-43% among the 8 cities. Premastication was not associated with occurrences of illness or with the nutritional indicators of height-for-age Z score, weight-for-age Z score, weight-for-height Z score, head circumference Z score and hemoglobin ( P all >.05). Premastication occurred more often among infants who were raised by their parents ( P = .005), whose mothers' education was lower ( P < .001), who were subject to more concern from their parents ( P = .022), and whose parents thought their children had an obesity problem ( P = .001). Presmastication was not associated with food picky behaviors. Premastication is still a common feeding practice in China. More studies are needed to determine the biological, economic, and cultural benefits or harm from premastication. [ABSTRACT FROM AUTHOR]

Haloxylon ammodendron is a desert shrub used extensively in China for restoring degraded dry lands. An understanding of the water source used by H. ammodendron plantations is critical achieving sustainable vegetation restoration. We measured mortality, shoot size, and rooting depth in 5-, 10-, 20-, and 40-year-old H. ammodendron plantations. We examined stable isotopic ratios of oxygen (δ18O) in precipitation, groundwater, and soil water in different soil layers and seasons, and in plant stem water to determine water sources at different shrub ages. We found that water acquisition patterns in H. ammodendron plantations differed with plantation age and season. Thus, the main water source for 5-year-old shrubs was shallow soil water. Water sources of 10-year-old shrubs shifted depending on the soil water conditions during the season. Although their tap roots could absorb deep soil water, the plantation main water sources were from soil water, and about 50% of water originated from shallow and mid soil. This pattern might occur because main water sources in these plantations were changeable over time. The 20- and 40-year-old shrubs acquired water mainly from permanent groundwater. We conclude that the main water source of a young H. ammodendron plantation was soil water recharged by precipitation. However, when roots reached sufficient depth, water originated mainly from the deep soil water, especially in the dry season. The deeply rooted 20- and 40-year-old shrubs have the ability to exploit a deep and reliable water source. To achieve sustainability in these plantations, we recommend a reduction in the initial density of H. ammodendron in the desert-oasis ecotone to decelerate the consumption of shallow soil water during plantation establishment. [ABSTRACT FROM AUTHOR]

Conservation management for the water dependent desert-oasis ecotone in arid northwest China requires information on the water use of the dominant species. However, no studies have quantified their combined water use or linked species composition to ecotone transpiration. Here, the water use of three dominant shelterbelt shrubs ( Haloxylon ammodendron, Nitraria tangutorum, and Calligonum mongolicum) within an ecotone was measured throughout the full leaf-out period for three shrub species from 30 May to 16 October 2014, with sap flow gauges using the stem heat balance approach. Species-specific transpiration was estimated by scaling up sap flow velocities measured in individual stems, to stand area level, using the frequency distribution of stem diameter and assuming a constant proportionality between sap flow velocity and basal cross-sectional area for all stems. The mean peak sap flux densities ( Jsn) for H. ammodendron, N. tangutorum, and C. mongolicum, were 40.12 g cm−2 h−1, 71.33 g cm−2 h−1, and 60.34 g cm−2 h−1, respectively, and the mean estimated daily area-averaged transpiration rates ( Tdaily) for the same species were 0.56 mm day−1, 0.34 mm day−1, and 0.11 mm day−1. The accumulative stand transpiration was approximately 140.8 mm throughout the measurement period, exceeding precipitation by as much as 42.1 mm. Furthermore, Tdaily of these shrubs appeared to be much less sensitive to soil moisture as compared to atmospheric drivers, and the relationship between Jsn and atmospheric drivers was likely uninfluenced by soil moisture regimes in the whole profile (to 1-m depth), especially for H. ammodendron and C. mongolicum. Results indicate that these shrubs may use deep soil water recharged by capillary rise, or may directly access shallow groundwater. This study provides quantitative data offering important implications for ecotone conservation and water and land resource management. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Duplex soils, consisting of a sandy surface soil (A-horizon) and silty-clay subsoil (B-horizon), occur in a boundary area between oasis and desert in northwestern China and create a challenging habitat for restoration of plant growth. We conducted an experiment in a 10-year-old H. ammodendron plantation forest to determine the influence of physical properties of duplex soil on water infiltration and plant root growth. We used a trenching method to assess root biomass, and classified roots into two diameter classes: fine (<2 mm) and coarse (>2 mm). Following a 26.7 mm rain event, water infiltrated to the B- horizon; further deep percolation was hindered by low hydraulic conductivity, so that B horizon remained at high available soil moisture for an extended period of time. Root biomass increased rapidly in, or very close to the B horizon, especially for coarse roots. The subsoil formed a barrier to root penetration, but may also reflect the accumulation of water resources at the boundary between the A- and B-horizon. Shoot growth and root distribution, shrub height and canopy area, and total root biomass were negatively correlation with depth to the B horizon, and that was reflected by quadratic functions. We conclude that the texture and structure of duplex soils influenced the soil environment for water infiltration and storage, indicating that the B-horizon underlying sand in duplex soils is advantageous for the growth, and development of planted sand-stabilizing vegetation. These results have important implications for sustainable development of sand-fixing plantations in desert ecosystems. [ABSTRACT FROM AUTHOR]

A combination of field measurements, continuous monitoring and numerical modelling was used to evaluate soil moisture regimes at four sites across a landscape gradient of the Heihe River Basin. Recorded data of precipitation, irrigation and floods were used to build the model, and an optimization technique was employed to calibrate the parameters. Based on the optimized parameters and estimates of future scenarios, the modelling structure was employed to predict the changes in the growing season soil moisture regimes due to climate change and intensive management. The results suggest that the upper-reach Yeniugou and Xishui sites will become wetter because of alterations in the precipitation regime, and this trend could be strengthened by the expected amplified interannual variability. Precipitation features at middle-reach Linze and lower-reach Ejina, however, are not expected to change in the future. We assumed that a more water-saving irrigation system will replace the current traditional one, and hence, the soil moisture probability density function at the Linze site would tend to be narrowed to ranges around either the wilting point or the point of incipient water stress, depending on how the intervention point and target level are settled. Ejina is expected to experience the most extreme ecological conversion effects in the future, and soil moisture would be more frequently recharged by water delivery. However, the soil moisture regime would not change much because of the poor water-holding capacity and intensive evaporation. The revealed patterns and predicted shifts in soil moisture dynamics could provide a useful reference for identifying robust long-term water resource management strategies for the Heihe River Basin. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Revegetation of indigenous plants in a desert-oasis ecotone is an effective way of maintaining the stability of oases. Understanding the changes in vegetation and soil is crucial for restoration management. The properties of soil and vegetation at stabilized sites of different ages were investigated in a typical desert-oasis ecotone, located in the Hexi Corridor region in arid northwestern China, over a period of 40 years. The results indicated that after 40 years the organic matter, total-N and available-P at 0-2 cm soil depth increased from 0.1, 0.1 g kg, 7 mg kg to 2.0, 0.9 g kg, and 75 mg kg, respectively. At 2-5 cm the organic matter, total-N and available-P increased from 0.4, 0.1 g kg, and 7 mg kg to 2.3, 0.4 g kg, and 38 mg kg, respectively. The number of herbaceous species increased from 4 to 9 and the herbaceous cover increased from 6 to 28 % after 40 years. The height and cover of the sand-binding vegetation Haloxylon ammodendron ( H. ammodendron) reached the highest levels of 446 cm and 68 % after 25 years. After 35 years H. ammodendron dwindled and its belowground and aboveground biomass both decreased significantly. With effective natural regeneration, after 40 years the population of H. ammodendron remained stable and its cover and density remained at 38 % and 1870 ha respectively. The positive mutual feedback between vegetation and soil permitted the sand-binding vegetation community to become stable over time. [ABSTRACT FROM AUTHOR]

With a maize seed planting area of about 67 000 hm2, Zhangye city supplies the seeds for more than 40% of the maize planting area in China. Irrigation water is often overused to ensure the quality of the maize seeds, leading to serious water shortage problems in recent years. An accurate and convenient estimate of canopy transpiration is of particular importance to ease the problem. In this paper, leaf transpiration and sap flow in a maize field were measured in 2012 using a portable photosynthesis system and a heat balance sap flow system. Based on a large amount of meteorological data and relevant maize plant-growing parameters, canopy transpiration was up-scaled from both leaf transpiration ( Tl) and sap flow ( Tf), and also calculated by the FAO-56 dual crop coefficient method ( T). Comparing these three types of transpiration, Tf was proved to be more reliable than Tl. Taking Tf as a benchmark, the basal crop coefficient ( Kcb, the key parameter of FAO-56 dual crop coefficient method) was further adjusted and verified for the maize plants in this region. In addition, the errors when using up-scaling methods and FAO-56 dual crop coefficient method are summarized. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

A case study on a desert-oasis wetland ecosystem in the arid region of Northwest China measured the seasonal and interannual variation in energy partitioning and evapotranspiration to analyse the response of water and energy exchange on soil moisture, groundwater, and environmental variables. Energy partitioning showed a clear seasonal and interannual variability, and the process of water and energy exchange differed significantly in the monthly and interannual scales. The net radiation was 7.31 MJ m−2· day−1, and sensible heat flux accounted for 50.42% of net radiation in energy fluxes, 40.56% for latent heat flux, and 9.02% for ground heat flux. The parameters in energy fluxes were best described by a unimodal curve, whereas sensible heat flux followed a bimodal curve. Variations in the daily evapotranspiration and crop evapotranspiration also exhibited a single peak curve with annual values of 569.84 and 644.47 mm, respectively. Canopy conductance averaged 20.77 ± 13.75 mm s−1 and varied from 0.16 to 83.96 mm s−1 during the two hydrological years. The variation in water and energy exchange reflected environmental conditions and depended primarily on vapour pressure deficit, net radiation, soil moisture, and water depth. Although the effects of precipitation on evapotranspiration showed that the response of this ecosystem to climate changes was not obvious, the variation of air temperatures had a strong influence on evapotranspiration, resulting in a significant increase in evapotranspiration ( R = 0.730; P < 0.01). Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Dew, as a supplementary water source, may have an important ecological role in arid and semi-arid regions. During August and September of 2007 and 2008, measurements were taken to investigate the dew accumulation and evaporation patterns in the very early morning hours, in three different habitats (dunetop, footslope, and interdune lowland) of a fixed sand dune in Northwest China. Dew quantities were measured using the cloth-plate method. The results indicated that there was a positive correlation between dew amounts and relative humidity, but a negative correlation between dew amounts and mean temperature. Clear mornings were characterized by higher dew amounts and longer dew duration, whereas less dew was recorded during cloudy and especially windy mornings. Dew continued to condense even after sunrise, although a shorter warming time after dawn is also of vital importance in dew formation. The higher average maximum dew quantities (0.06 mm) and longer average dew duration (2.3 h) occurred in the interdune lowland; the lower and shorter average dew amounts (0.048 mm) and duration (1.9 h) were obtained at the dune top. The footslope habitat exhibited intermediate values. Clearly, the differences in dew deposition can be partially attributed to the distinguishing characteristics of the microhabitats. The present study highlighted the impacts of these characteristics on near-ground dew condensation accumulation and evaporation in a fixed sand dune and may facilitate evaluation of the role of dew in arid and semi-arid environments. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

For many practical reasons, the empirical black-box models have become an increasingly popular modelling tool for river flow forecasting, especially in mountainous areas where very few meteorological observatories exist. In this article, precipitation data are used as the only input to estimate river flow. Using five empirical black-box models-the simple linear model, the linear perturbation model, the linearly varying gain factor model, the constrained nonlinear system model and the nonlinear perturbation model-antecedent precipitation index-modelling results are compared with actual results in three catchments within the Heihe River Basin. The linearly varying gain factor model and the nonlinear perturbation model yielded excellent predictions. For better simulation accuracy, a commonly used multilayer feed-forward neural network model (NNM) was applied to incorporate the outputs of the individual models. Comparing the performance of these models, it was found that the best results were obtained from the NNM model. The results also suggest that more reliable and precise predictions of river flow can be obtained by using the NNM model while also incorporating the combined outputs of different empirical black-box models. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The surface energy balance algorithm for land method was used in this study to calculate the evapotranspiration (ET) rate for the middle reaches of the Heihe River Basin, Gansu Province, China, to analyse ET distribution within the oasis and the surrounding desert and, especially, on the edge zone of the oasis. Five profile graphs were created vertical to the river. Because of the inverse humidity phenomenon, the least amount of evapotranspiration occurred on the desert close to the oasis. The average evapotranspiration rate was roughly proportioned from the edge of the oasis to inside and outside its boundary. Two meteorological ground stations located close to the oasis edge showed a notable difference in net radiation flux that led to the difference found in ET. The primary reason for the significant differences observed in net radiation may be largely the result of differences in flux reflectivity and surface temperature. Meteorological data show that water supply also played an important role. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Herein, we report a facile surfactant-assisted solvothermal synthetic method to prepare nearly monodisperse spherical CeO2 nanocrystals. A good control of the size of CeO2 nanocrystals in the range of 100-500 nm was achieved by simply varying the synthetic parameters such as reaction time, volume ratio of ethanol to water ( R), molar ratio of PVP, and concentration of Ce(NO3)3⋅6 H2O in solution. A possible mechanism for the growth of spherical CeO2 nanocrystals is proposed. The obtained CeO2 nanocrystals with a surface area of up to 47 m2g−1 were then employed as a catalyst support. By loading Au-Pd nanoparticles (about 3 wt. %) onto the CeO2 support, an Au-Pd/CeO2 catalyst was prepared that exhibited high catalytic activity for HCHO oxidation. At the low temperature of 50 °C, the percentage of HCHO conversion was 100 %, suggesting potential applications in preferential oxidation and other catalytic reactions. These Au-Pd/CeO2 catalysts may also find applications in indoor formaldehyde decontamination and industrial catalysis. The facile solvothermal method can be extended to the preparation of other metal oxide nanocrystals and provides guidance for size- and morphology-controlled synthesis. [ABSTRACT FROM AUTHOR]

The effect of forests on annual water yield is an unresolved central issue in forest hydrology despite years of study. There has been a particular shortage of research in the mountains of arid inland river basins. In the present study, we examined the effects of forests on hydrology using data on precipitation, evaporation, canopy interception, transpiration, and runoff from 1994 to 2008 for the Pailugou catchment of northwestern China's Qilian Mountains. We modelled the water balance to assess the contribution of different vegetation types to annual water yield. In our study area, Picea crassifolia forest covered 38·5% of the catchment area, but contributed little to annual water yield. For an annual average precipitation of 407·1 mm (from 2003 to 2008) at an elevation of 2700 m, the runoff depth from the forest was 11·6 mm, accounting for only 3·5% of total annual water yield of the catchment. For an annual average precipitation of 374·1 mm (from 1994 to 2002), the runoff depth from the forest was − 14·3 mm (i.e. 5·9% of total annual water yield of the catchment was consumed to sustain tree growth). This has significant implications, because forests are increasingly being planted in the Qilian Mountains, and this may decrease the downstream water supply. Thus, the relationship between the forest and water yield must be better understood to permit the establishment of an appropriate regional level of forest cover. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]