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Maize/peanut intercropping may improve soil health through reducing nitrogen (N) fertilization. However, the effects of maize/peanut intercropping combined with reduced N fertilization on the soil fungal community structure have not been well reported. Using a long-term localized micro-zone experiment, we investigated the combined effects of intercropping and N fertilizer application on soil fungal community diversity and composition. Three cropping patterns (maize/peanut intercropping, maize monoculture, and peanut monoculture) and three N application levels (0 kg·hm−2, 150 kg·hm−2, and 300 kg·hm−2) were assessed. The results showed that the total numbers of fungal species and unique species (operational taxonomic units, OTUs) in both maize and peanut soils tended to first increase and then decrease with increasing N application. Compared with monoculture, the numbers of total OTUs and unique OTUs in intercropped maize soil decreased by 4.14% and 12.79%, respectively, but the total numbers of OTUs and unique OTUs in peanut soil increased by 1.08% and 3.78%, respectively. With increasing N application, the soil fungal Ace and Chao indices of maize soil first increased and then decreased, while the fungal Shannon, Ace, and Chao indices of peanut soil decreased. Compared with the monoculture system, intercropping significantly reduced the maize soil fungal Ace and Chao indices but increased the peanut soil fungal Shannon, Ace, and Chao indices. Nitrogen application and intercropping significantly altered the fungal community structure of maize soil, while N application had no significant effect on the fungal community structure of peanut soil, though intercropping significantly changed the fungal community structure of peanut soil. At the phylum level, Ascomycota, Basidiomycota, Mortierellomycota, unclassified_k_Fungi, and Chytridiomycota were the dominant taxa. Redundancy analysis (RDA) showed that soil nitrate (NO3−) content was the main environmental factor shaping the soil fungal community. In conclusion, excessive N fertilization (300 kg·hm−2) can reduce soil fungal community diversity; maize/peanut intercropping reversed the negative effect of N application on fungal community of peanut soil, but not that of maize soil. Soil NO3− content is the primary environmental driver of soil fungal communities. [ABSTRACT FROM AUTHOR]

The urban water system theory is an extension of the basin water system science on an urban scale, providing a new systematic solution for the unbalanced human-water relationship and severe water challenges, such as waterlogging, black and odorous water, and ecological degradation caused by urbanization. Most existing studies on urban water systems have focused on individual water cycle processes linked with water supply and sewage treatment plants, but mutual feedback between the water cycle and its associated material circulation and water ecology, as well as human processes, still needs further exploration. In this paper, the concept, theory, and technical methodology of the urban water system were developed based on the water cycle and basin water system science. The Urban Water System 5.0 (UWS 5.0) model was developed by integrating the Time Variant Gain rainfall-runoff Model with Urban water system (TVGM_Urban) in different underlying surface conditions for analyzing the natural-social water cycle processes and their associated water environmental and ecological processes and the influence of multiscale sponge measures. Herein, five major simulation functions were realized: rainfall-runoff-nonpoint source pollutant load, water and pollutant transportations through the drainage network system, terminal regulation and purification, socioeconomic water cycle, and water system assessment and regulation. The location for the case study used in this paper was Wuhan City. The findings showed that the entire urban water system should consider the built-up area and its associated rivers and lakes as the research object and explore the integrations among the urban natural-social water cycle and river regulations inside and outside of the city as well as the effects of socioeconomic development and sponge measures on the water quantity-quality-ecology processes. The UWS 5.0 model efficiently simulated the urban rainfall-runoff process, total nitrogen (TN) and total phosphorus (TP) concentrations in water bodies, and characteristic indicators of socioeconomic development. For the rainfall-runoff simulations, the correlation coefficient and Nash-Sutcliffe efficiency (NSE) fall under the excellent and good classes, respectively. For the TN and TP concentration simulations, results exhibited good bias and the correlation coefficients exceeded 0.90 for 78.1% of the sampled sites. The simulation of 18 socioeconomic indicators provided excellent bias, correlation coefficient, and NSE values of 100%, 83.3%, and 69.4% to total indicators, respectively. Based on the well-calibrated UWS 5.0 model, the source sponge, artificial enhancement, and source reduction-path interception-terminal treatment measures were optimized, which considerably mitigated waterlogging, black and odorous water, and lake eutrophication, respectively. The mitigation performance revealed that the maximum inundated area for a once-in-10-year rainfall event was reduced by 32.6%, the removal ratio of the black and odorous water area was 65%, the comprehensive trophic state index of water bodies was reduced by 37%, and the green development level of Wuhan City in 2020 increased from 0.56 to 0.67. This study is expected to advance the intersection and development of multidisciplinary fields (e.g., urban hydrology, environmental science, and ecology) and offer an important theoretical and technical basis for solving urban complex water issues and promoting green development of cities. [ABSTRACT FROM AUTHOR]

Global warming has severely affected the climate in the Yangtze River Basin (YRB), resulting in complex and varying meteorological and hydrological processes. Therefore, identifying the effects of climate change in the YRB is important for characterizing the affected meteorological and hydrological processes. In this study, the characteristics of climate equilibrium were analyzed and the natural drivers of climate change in the YRB were explored using precipitation and temperature data from 1961 to 2018. The major findings can be summarized as follows. (1) Significant spatial and temporal differences in precipitation and temperature occurred. For example, annual precipitation showed a decreasing trend in the middle reaches but a significant increasing trend in the headwaters area and lower reaches. Between 1981 and 2001, annual precipitation and temperature exhibited overall increasing trends as well as abrupt changes. (2) Temporal changes in precipitation were primarily low in the middle and lower reaches and high in the headwater region of the YRB, although a low precipitation concentration degree (CD) occurred in summer in the upper reaches. High temperature changes over time mainly occurred in the headwater region of the YRB, although a high temperature CD occurred in winter in the northern parts. (3) Different teleconnection indices affected precipitation and temperature in different seasons. In particular, the Niño 3.4, North Atlantic Oscillation, and North Pacific Index had a significant influence on precipitation and temperature. This study provides critical information for revealing the changes in meteorological and hydrological processes and potential influencing factors in the YRB. [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]

• A catchment plastic yield and transport model of multiple sources is proposed. • Model ensemble is adopted to estimate plastic sources and its uncertainty intervals. • The proposed model performs well for both plastic yield and outflow simulations. • Primary plastic sources are solid waste, agricultural film and impermeable surfaces. • Substantial plastic loads are retained in land system due to low loss coefficients. Plastic pollution has emerged as a global environmental concern, impacting both terrestrial and marine ecosystems. However, understanding of plastic sources and transport mechanism at the catchment scale remains limited. This study introduces a multi-source plastic yield and transport model, which integrates catchment economic activities, climate data, and hydrological processes. Model parameters were calibrated using a combination of field observations, existing literature, and statistical random sampling techniques. The model demonstrated robust performance in simulating both plastic yield and transport from 2010 to 2020 in the upper and middle Mulan River Catchment, located in southeast China. The annual average yield coefficients were found to closely align with existing estimations, and the riverine outflow exhibited a high correlation coefficient of 0.97, with biases ranging from -63.0 % to -21.4 % across all monitoring stations. The analysis reveals that, on average, 12.5 ± 2.5 % of the total plastic yield is transported to rivers annually, with solid waste identified as the primary source, accounting for 37.8 ± 20.7 % of the total load to rivers, followed by agricultural film (26.4 ± 9.8 %), impermeable surfaces (21.5 ± 10.3 %), urban and rural sewage (10.4 ± 5.0 % and 3.0 ± 1.5 %, respectively), and industrial wastewater (0.9 ± 0.7 %). The annual average outflow was estimated to between 9.3 and 43.0 ton/year (median: 23.1) at a 95 % confidence level. This study not only provides insights into the primary sources and transport pathways of plastic pollution at the catchment scale, but also offers a valuable tool for informing effective plastic pollution mitigation strategies. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Three NDVI vegetation correction schemes with CRNS were provided. • The ratio of parameter N 0 between different landscapes reached 1.42. • N 0 was negatively correlated with NDVI (y = 373.9 (x + 0.015)−0.136, R2 = 0.77) • Three methods reduced RMSE from 0.093 to 0.063, 0.054, and 0.032 g g−1, respectively. Cosmic-ray neutron sensors (CRNS) are a powerful tool for measuring soil moisture on a hectometer scale, and mobile cosmic-ray neutron technology holds significant importance for upscaling soil moisture. However, vegetation strongly affects with CRNS soil moisture measurements. Variations in vegetation over time change how the CRNS is affected, which is more challenging than a stable vegetation cover, particularly during CRNS roving, where one crosses many vegetation covers. To correct vegetation, we hypothesized that Normalized Difference Vegetation Index (NDVI) can represent vegetation hydrogen pools. From 2020 to 2023, at the 74 plots with varying vegetation cover near the Qilian Mountains, the experiments for soil moisture measurements were conducted in shrubs, forests, deserts, farmlands, and grasslands using a Cosmic-ray Neutron Rover. The measured neutron intensity clearly varied across different landscapes, and the calibrated parameter N 0 differed among 74 plots. The variations in vegetation cover resulted in low measurement accuracy for CRNS. All three NDVI vegetation correction methods (NDVI-θ NDVI method, NDVI-NDVI ave method, and NDVI-N 0 method) offered by the study could improve accuracy of soil moisture measurements. In the optimal NDVI-N 0 method, the relationship between NDVI and N 0 was established using a power function y = 373.9 (x + 0.015)−0.136 (R2 = 0.77), which had the capability to decrease the root mean square error between oven-dried and measured soil moisture from 0.093 to 0.032 g g−1 in our study area. Employing NDVI instead of biomass for CRNS vegetation correction can substantially reduce workload and effectively enhance CRNS soil moisture measurements, showing the potential for upscaling soil moisture. [ABSTRACT FROM AUTHOR]

Background and aims: Fusarium wilt caused by Fusarium oxysporum f. sp. lycopersici (Fol) has severely decreased global tomato production. Organic amendments are widely applied to suppress Fol all over the world. However, the ways in which different amendments alter soil bulk microflora and thereby induce the suppression of Fol remain unclear. Methods: In this study, the effects of three organic amendments on the suppression of Fol in soil and the underlying mechanisms of those effects were studied. The organic amendments included in this study are rice straw, chicken manure compost, and vermicompost. High-throughput HiSeq sequencing and Real-Time PCR were used to determine the effect of the soil microbiota on the abundance of Fol. Results: The abundance of Fol increased significantly with the duration of tomato cultivation. Vermicompost was the most effective organic fertilizer to suppress Fol in long-term continuous tomato cropping soil. Partial Least Squares Path Modeling revealed a strong positive relationship between the relative abundance of bacterial groups (including the genera Nocardioides, Ilumatobacter and Gaiella) and Fol inhibition. Soil chemical properties (pH, NH4+-N, soil organic matter and dissolved organic carbon) were positively associated with the genera Nocardioides, Ilumatobacter and Gaiella. Compared with chemical fertilizer and rice straw, vermicompost addition significantly increased soil pH, NH4+-N, soil organic matter and dissolved organic carbon concentrations in the soil with 20 years of tomato cultivation. Most importantly, the genera Nocardioides, Ilumatobacter and Gaiella were enriched in vermicompost, which may contribute to the propagation of these bacteria in the soil when vermicompost is added. Conclusions: This study provides a mechanistic framework that permits the exploration of specific functions at lower taxonomic levels. This may represent a novel approach in the management of crop pathogens via promotion of beneficial organisms. [ABSTRACT FROM AUTHOR]

Highlights • Anomaly correlation exhibits persistent patterns at the global scale. • Anomaly correlation tends to be similarly high, or low, across initialization times. • Anomaly correlation tends to improve with initialization time. Abstract Global climate models (GCMs) produce informative seasonal forecasts of global precipitation months ahead of the occurrence for hydrological forecasting. Meanwhile, the skill of GCM forecasts varies by location and initialization time. In this paper, we investigate the anomaly correlation, which indicates the correspondence between forecasts and observations, for 10 sets of global precipitation forecasts in the North American Multi-Model Ensemble (NMME) project. We propose to use principal component analysis to characterize the variation of anomaly correlation. We identify the existence of spatial and temporal patterns at the global scale. The spatial pattern reveals that high (low) anomaly correlation at one initialization time coincides with high (low) anomaly correlation at other initialization times. In other words, for a grid cell, the anomaly correlation at different initialization times tends to be similarly high, or low. It is observed that some of the regions where grid cells are with overall high anomaly correlation tend to exhibit tele-connections with global climate drivers. On the other hand, the temporal pattern suggests that the anomaly correlation tends to improve with initialization time. This pattern is attributable to data assimilation that bases forecasts at a later initialization time on more global observations and simulations. Generally, the two patterns are effective and explain 50% to 70% of the variation of anomaly correlation for the 10 sets of NMME forecasts. The projections of anomaly correlation vectors onto the two patterns help illustrate where and when the NMME precipitation forecasts are skillful. [ABSTRACT FROM AUTHOR]

Abstract Phytoplankton is critical to river ecosystems. These organisms are sensitive to streamflow and water quality changes and, therefore, used to determine stability of river ecosystems, especially in regulated rivers. However, exactly how such disturbances alter spatial distribution of phytoplankton remains unclear, particularly during different seasons. A thorough understanding of these mechanisms is required to better analyze impact of environmental factors on regulated rivers. Given this, phytoplankton communities, streamflow, and water quality factors were assessed in areas sampled four times from 2015 to 2016 in upper and middle Huai River Basin. Biodiversity indices, as well as cluster and rank analyses, were used to (1) determine phytoplankton composition and distribution and (2) clarify impacts of key streamflow and water quality factors on such communities. It was found phytoplankton composition deteriorated over time, with phyla number decreasing from six to three. Moreover, proportion of Bacillariophyta increased from 51.83% to 68.13%. Phytoplankton in three regions, upstream region (Shannon-Wiener index 1.39–2.95), midstream region (0.70–4.55), and downstream region (0.22 to 2.97), were spatially clustered. The most impact factors impacting variation in composition and distribution were water quality factors and then hydrological factors. Of these, the most important factors in wet seasons were total nitrogen and maximum runoff, while ammonia nitrogen and low flow discharge were the most important factors during dry seasons. Streamflow and water quality contributed the most in midstream region, which was significantly affected by numbers of high and low flow. Contributions of these factors to downstream region were the strongest during dry seasons, which were significantly affected by numbers of low flow. Collectively, these results reveal significant impact of streamflow and water quality factors on phytoplankton deterioration in upper and middle Huai River Basin. Critically, this study provides scientific and technological support for increased biomonitoring and ecohydrological studies in regulated river basins. Graphical abstract Unlabelled Image Highlights • Phytoplankton deterioration results in high pollution and regulation. • Water quality factors contribute more than flow regimes indices. • High flow indices contribute to the deterioration and low flow indices restrain it. • Nitrogen nutrients take the most important role in phytoplankton communities. [ABSTRACT FROM AUTHOR]

Abstract Phosphate fertilizers are used in horticultural production to increase yields, but overuse can result in inefficient crop uptake and large loss of phosphorus (P). Soil amendments could potentially reduce the risk of P loss while maintaining high crop yield. The objective of this study was to investigate the effect of organic and inorganic amendments on P fractions in soils with different P levels (low, medium and high), and the underlying mechanisms. Five treatments were included: no amendment (CK), chemical fertilizers (CF), rice straw (FS), chicken manure compost (CM), and vermicompost (VM). Counterintuitively, the proportion of organic phosphorus (OP) tended to increase in the CF treatment, especially in soil with low P level. Results indicated that the change in the proportion of OP was mainly controlled by soil acid phosphomonoesterase, alkaline phosphomonoesterase and phosphate-solubilizing microorganisms. The proportion of available P increased in soil with low P level, but decreased in soil with high P level in the VM treatment. Non-labile P was preferentially formed in the VM treatment because of the high calcium content in vermicompost. Phosphates associated with aluminum (Al-P) were significantly higher in the CM treatment than in other treatments. This treatment also had a large presence of Pseudomonas and Streptomyces bacteria, which are capable of promoting the formation of Al-P. Our results indicated that mechanisms causing changes in soil P fractions were distinctly different among various amendments, and that vermicompost had the greatest potential to increase P supply in soil with low P level, and to decrease the risk of P loss in soil with high P level. Graphical abstract Unlabelled Image Highlights • Soil P fractions were investigated under different soil amendments. • Suitable amendments were proposed for soil with different P levels. • Chemical fertilizer addition tended to increase the proportion of soil organic P. • Vermicompost addition was superior in decreasing potential risk of P loss in soil with high P level. [ABSTRACT FROM AUTHOR]

Because drought is a very common and widespread natural disaster, it has attracted a great deal of academic interest. Based on 12-month time scale standardized precipitation indices (SPI12) calculated from precipitation data recorded between 1960 and 2015 at 22 weather stations in the Tarim River Basin (TRB), this study aims to identify the trends of SPI and drought duration, severity, and frequency at various quantiles and to perform cluster analysis of drought events in the TRB. The results indicated that (1) both precipitation and temperature at most stations in the TRB exhibited significant positive trends during 1960-2015; (2) multiple scales of SPIs changed significantly around 1986; (3) based on quantile regression analysis of temporal drought changes, the positive SPI slopes indicated less severe and less frequent droughts at lower quantiles, but clear variation was detected in the drought frequency; and (4) significantly different trends were found in drought frequency probably between severe droughts and drought frequency. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Module uncertainty and its propagation are estimated for integrated model. • Final distributions of both water quantity and quality parameters are skew. • Major simulation uncertainties of runoff and water quality are from model structure. • Hydrological parameter uncertainty propagates to water quality simulation. Abstract Multiple uncertainty sources directly cause inaccurate simulations for water related processes in complicated integrated models, as such models include many interactive modules. A majority of existing studies focus on the uncertainties of parameter and model structure, and their effects on the model performance for a single process (e.g., hydrological cycle or water quality). However, comprehensive uncertainties of different modules and their propagations are poorly understood, particularly for the integrated water system model. This study proposes a framework of uncertainty and its propagation estimation for integrated water system model (HEQM) by coupling the Bootstrap resampling method and SCE-UA auto-calibration technique. Parameter and structure uncertainties of both hydrological cycle and water quality modules are estimated, including final distributions of parameters and simulation uncertainty intervals. Additionally, the effect of uncertainty propagation of hydrological parameters is investigated. Results show that: (1) HEQM simulates daily hydrograph very well with the coefficient of efficiency of 0.81, and also simulates the daily concentrations of ammonia nitrogen satisfactorily with the coefficient of efficiency of 0.50 by auto-calibration in the case study area; (2) The final ranges of all interested hydrological parameters are reduced obviously, and all the parameter distributions are well-defined and show skew. The uncertainty intervals of runoff simulation at the 95% confidence level bracket 18.7% of all the runoff observations due to uncertainties of parameter, and 86.0% due to both parameter and module structure, respectively; (3) The uncertainty propagation of hydrological parameters changes the optimal values of 37.5% of interested water quality parameters, but does not obviously change the water quality simulations which match well with the prior simulations throughout the period and bracket only 1.7% of observations at the 95% confidence level. Due to the further introduction of module structure uncertainties, 94.8% of observations are bracketed, only except the extreme high and low water quality concentrations; (4) The uncertainty of water quality parameters contributes 12.1% of total water quality simulations at the 95% confidence level. The figure increases to 21.0% and 92.0% if the uncertainty propagation of hydrological parameters, structure uncertainties of water quality module are considered, respectively. Therefore, although the parameter uncertainty and its propagation contribute a certain proportion of the whole simulation uncertainties, the module structure itself is the primary uncertainty source for the integrated water system model (HEQM), particular for the water quality modules. [ABSTRACT FROM AUTHOR]

The characteristics of water-soluble inorganic ions (WSIIs) during a winter period in a suburb of Xi'an, China, were investigated. Our results show that the total mass concentration of the dominant WSIIs (8) was 91.27 µg m-3, accounting for 50.1% of the total mass concentration of PM2.5 (particulates with a size of 2.5 µm or less). Secondary inorganic aerosols (SO42−, NO3− and NH4+) were the most abundant ions, accounting for up to 95.12% of the total ions. By using the anion and cation equivalence ratio method, PM2.5 was shown to have weak alkalinity, and the chemical forms of WSIIs were mainly (NH4)2SO4 and NH4NO3. The sulfur oxidation ratio (SOR) and nitrogen oxidation ratio (NOR) suggested that larger proportions of SO42− and NO3− were formed by gas-phase SO2 and NO2 in the sampling site. Ratio analysis also indicated that anthropogenic sources significantly contributed to WSII pollution. Among the anthropogenic sources, fixed pollution sources were found to be dominant over mobile sources. [ABSTRACT FROM AUTHOR]

Urbanization-induced landuse changes alter runoff regimes in complex ways. In this study, a detailed investigation of the urbanization impacts on runoff regimes is provided by using multiple runoff metrics and with consideration of landuse dynamics. A catchment hydrological model is modified by coupling a simplified flow routing module of the urban drainage system and landuse dynamics to improve long-term urban runoff simulations. Moreover, multivariate statistical approach is adopted to mine the spatial variations of runoff metrics so as to further identify critical impact factors of landuse changes. The Qing River catchment as a peri-urban catchment in the Beijing metropolitan area is selected as our study region. Results show that: (1) the dryland agriculture is decreased from 13.9% to 1.5% of the total catchment area in the years 2000–2015, while the percentages of impervious surface, forest and grass are increased from 63.5% to 72.4%, 13.5% to 16.6% and 5.1% to 6.5%, respectively. The most dramatic landuse changes occur in the middle and downstream regions; (2) The combined landuse changes do not alter the average flow metrics obviously at the catchment outlet, but slightly increase the high flow metrics, particularly the extreme high flows; (3) The impacts on runoff metrics in the sub-catchments are more obvious than those at the catchment outlet. For the average flow metrics, the most impacted metric is the runoff depth in the dry season (October ∼ May) with a relative change from −10.9% to 11.6%, and the critical impact factors are the impervious surface and grass. For the high flow metrics, the extreme high flow depth is increased most significantly with a relative change from −0.6% to 10.5%, and the critical impact factors are the impervious surface and dryland agriculture; (4) The runoff depth metrics in the sub-catchments are increased because of the landuse changes from dryland agriculture to impervious surface, but are decreased because of the landuse changes from dryland agriculture or impervious surface to grass or forest. The results of this study provide useful information for urban planning such as Sponge City design. [ABSTRACT FROM AUTHOR]

The characterization of carbonaceous species in PM2.5 during a spring period in a suburb of Xi'an, China was investigated. PM2.5 samples were collected on quartz filters and analyzed for organic carbon (OC) and elemental carbon (EC). The thermal optical reflectance method was used. The minimum OC/EC ratio method was used to estimate the concentration of secondary organic carbon (SOC). The distribution of eight carbon fractions was investigated as well. The average mass concentrations of OC and EC were 15.90 and 8.38 μg/m3, respectively. The average OC/EC ratio ranged from 1.16 to 3.16 with an average value of 2.25. This implies the existence of SOC in PM2.5. The mean SOC concentration was 7.20 μg/m3, accounting for 45.28% of total OC. This result suggests that SOC is a significant component of OC in the suburb of Xi'an. Results from the distribution of eight carbon fractions revealed that emissions from motor vehicle, coal combustion, and road dust were the main source of carbonaceous particles in the sampling period. [ABSTRACT FROM AUTHOR]

By pot experiment method, this study investigated the role of plant hormone abscisic acid (ABA) in the foliar application of 10 μM lanthanum nitrate (La(NO 3 ) 3 )-regulated the biosynthesis, regeneration and degradation of vitamin C (Vc) and the content of Vc in the fruit of strawberry at different periods of growth and development. The results showed that La(NO 3 ) 3 significantly increased the content of Vc by increasingthe activities of recycling enzymes glutathione reductase (GR), dehydroascorbate reductase (DHAR), monodehydroascorbate reductase (MDHAR) and biosynthetic enzyme L-galactono-1,4-lactone dehydrogenase (GalLDH), and decreasing the activities of recycling enzyme APX and degrading enzyme ascorbic acid oxidase (AAO). Compared with La(NO 3 ) 3 alone, applications of different ABA biosynthesis inhibitor sodium tungstate (Tu) all markedly decreased the activities of GR, MDHAR and GalLDH, and increased the activities of DHAR and APX, which resulted in the reduction in the content of Vc. Meanwhile, La(NO 3 ) 3 induced the production of ABA and Tu reversed the effect of La(NO 3 ) 3 on ABA content. Our results suggested that La(NO 3 ) 3 -induced ABA participated in the regulation of Vc content in the fruit of strawberry. [ABSTRACT FROM AUTHOR]

Assessing the impact of human intervention on flow regimes is important in policy making and resource management. Previous impact assessments of dam regulation on flow regimes have focused on long-term average patterns, but interannual variations, which are important characteristics to be considered, have been ignored. In this study, the entire signatures of hydrograph variations of Miyun Reservoir in northern China were described by forty flow regime metrics that incorporate magnitude, variability and frequency, duration, timing, and rate of change for flow events based on a long-term synchronous observation series of inflow and outflow. Principal component analysis and cluster analysis were used to reduce the multidimensionality of the metrics and time and to determine impact patterns and their interannual shifts. Statistically significant driving factors of impact pattern variations were identified. We found that dam regulation resulted in four main impact classes on the flow regimes and that the regulated capacity was interannually attenuated from 1973 to 2010. The impact patterns alternated between the highly regulated class with extremely decreasing flow magnitude, slight variability, and extreme intermittency and the slightly regulated class with extremely increasing flow magnitude, slight variability, and extreme intermittency from 1973 to 1987 and then stabilized in the latter class from 1988 to 2001. After 2001, the pattern gradually changed from the moderately regulated class with moderately decreasing flow magnitude, extreme variability, and extreme intermittency to the slightly regulated class with slightly decreasing flow magnitude, slight variability, and no intermittency. Decreasing precipitation and increasing drought were the primary drivers for the interannual variations of the impact patterns, and inflow variability was the most significant factor affecting the patterns, followed by flow event frequency and duration, magnitude, and timing. This study shows that the use of interannual characteristics can help to gain more insight into the impact of dam regulation on flow regimes and will provide important information to scientifically guide the multi-purpose regulation of dams. [ABSTRACT FROM AUTHOR]

Agricultural nitrogen loss becomes an increasingly important source of water quality deterioration and eutrophication, even threatens water safety for humanity. Nitrogen dynamic mechanism is still too complicated to be well captured at watershed scale due to its multiple existence forms and instability, disturbance of agricultural management practices. Stereoscopic agriculture is a novel agricultural planting pattern to efficiently use local natural resources (e.g., water, land, sunshine, heat and fertilizer). It is widely promoted as a high yield system and can obtain considerable economic benefits, particularly in China. However, its environmental quality implication is not clear. In our study, Qianyanzhou station is famous for its stereoscopic agriculture pattern of Southern China, and an experimental watershed was selected as our study area. Regional characteristics of runoff and nitrogen losses were simulated by an integrated water system model (HEQM) with multi-objective calibration, and multiple agriculture practices were assessed to find the effective approach for the reduction of diffuse nitrogen losses. Results showed that daily variations of runoff and nitrogen forms were well reproduced throughout watershed, i.e., satisfactory performances for ammonium and nitrate nitrogen (NH 4 -N and NO 3 -N) loads, good performances for runoff and organic nitrogen (ON) load, and very good performance for total nitrogen (TN) load. The average loss coefficient was 62.74 kg/ha for NH 4 -N, 0.98 kg/ha for NO 3 -N, 0.0004 kg/ha for ON and 63.80 kg/ha for TN. The dominating form of nitrogen losses was NH 4 -N due to the applied fertilizers, and the most dramatic zones aggregated in the middle and downstream regions covered by paddy and orange orchard. In order to control diffuse nitrogen losses, the most effective practices for Qianyanzhou stereoscopic agriculture pattern were to reduce farmland planting scale in the valley by afforestation, particularly for orchard in the downstream regions, followed by fertilizer application optimization. [ABSTRACT FROM AUTHOR]

Sustainable use of cultivated desert soils is important for agricultural productivity in desert-oasis ecosystems. However, how soil macropore characteristics may change as a result of agricultural exploitation remains unclear. The objective of this study was to quantify and compare soil properties and macropore characteristics in an old oasis field (>50 years of cultivation, OOF), young oasis field (20 years, YOF), and adjacent uncultivated sandy land (0 year, USL) in Northwest China. Three replicated soil samples were collected from each site to investigate soil properties. Meanwhile, twelve (four replicates by three sites) intact soil core columns, 15 cm in diameter and 30 cm in height, were taken to analyze soil structure. Each soil column was scanned with a helical medical X-ray computed tomography (CT) at a voxel resolution of 0.469 mm × 0.469 mm × 0.600 mm. The results indicated that soil properties and macropore features improved after cultivation. Silt and clay content and dry mean weight diameter (DMWD) of aggregates increased with cultivation time, whereas bulk density decreased. Soil organic carbon and total nitrogen were 7.3 times and 6.7 times greater in soils at the OOF site than USL site, respectively. The increase in silt and clay content and aggregates formation likely resulted from irrigation with silt-laden river water, which in turn impacted soil nutrient accumulation. Soils at the OOF and YOF sites had greater macroporosity compared with soil at USL, and macroporosity also increased with cultivation time. X-ray CT revealed that soil macroporosity was 8.7–18.9 times greater in irrigated croplands than native desert. Soil macropores were mainly distributed at soil depths of 0–200 mm at the OOF and YOF sites, while smaller and less continuous macropores were randomly distributed across soil depths at the USL site. The larger number of macropores at the cultivated sites can be attributed to greater soil organic carbon, tillage-induced soil horizons, and alternate wetting and drying processes. Few soil macropores at the USL site may be associated with wind erosion and soil fauna burrows. Conversion of native desert soils to irrigated croplands had a positive effect on soil pore development in the desert-oasis ecotone. [ABSTRACT FROM AUTHOR]

Waterlogging is one of the major water issues in most cities of China and directly restricts their urbanization processes. The construction of Sponge City is an effective approach to solving the urban water issues, particularly for the waterlogging. In this study, both the urban issues emerged at the stage of rapid urbanization in China and the demands as well as problems of Sponge City construction related with the water issues were investigated, and the opportunities and challenges for the Sponge City construction in the future were also proposed. It was found that the current stormwater management focused on the construction of gray infrastructures (e.g., drainage network and water tank) based on the fast discharge idea, which was costly and hard to catch up with the rapid expansion of city and its impervious surface, while green infrastructures (e.g., river, lake and wetland) were ignored. Moreover, the current construction of Sponge City was still limited to low impacted development (LID) approach which was concentrated on source control measures without consideration of the critical functions of surrounding landscapes (i.e., mountain, river, wetland, forest, farmland and lake), while application of the integrated urban water system approach and its supported technologies including municipal engineering, urban hydrology, environmental science, social science and ecoscape were relatively weak and needed to be improved. Besides, the lack of special Sponge City plan and demonstration area was also a considerable problem. In this paper, some perspectives on Good Sponge City Construction were proposed such as the point that idea of urban plan and construction should conform to the integral and systematic view of sustainable urban development. Therefore, both the basic theoretical research and the basic infrastructure construction such as monitoring system, drainage facility and demonstration area should be strengthened, meanwhile, the reformation and innovation in the urban water management system and the education system should also be urgently performed. The study was expected to provide a deeper thinking for the current Sponge City construction in China and to give some of suggestions for the future directions to urban plan and construction, as well as urban hydrology discipline. [ABSTRACT FROM AUTHOR]

This study aims to investigate the relationships of sample, morphology, and mineralogy with indoor and outdoor PM2.5during a heating period and a nonheating period. Indoor (a naturally ventilated office) and outdoor (adjacent courtyard) PM2.5concentrations were continuously monitored in Xi'an, China from June 1, 2015 to January 7, 2016. The average indoor and outdoor PM2.5concentrations during the heating period were 169 and 224 μg/m3respectively, whereas the corresponding PM2.5for the nonheating episode were 59 and 66 μg/m3. The indoor/outdoor ratio and infiltration factor revealed that PM2.5had primarily outdoor sources. Morphology, elemental composition, and mineralogy of PM2.5collected indoors and outdoors were studied using scanning electron microscopy coupled with energy dispersive spectrometry (SEM-EDS) and X-ray diffraction (XRD). The SEM micrograph of PM2.5collected during the heating period was different from that collected during the nonheating period both indoors and outdoors. EDS spectra indicated that C- and O-rich particles dominated over other elements regardless of the sampling period or place and the indoor PM2.5consists mainly of earth crustal materials. Based on the XRD analysis, indoor PM2.5was mostly made up of amorphous compounds while outdoor PM2.5contained some crystalline materials such as quartz, hematite, and calcium carbonate. [ABSTRACT FROM AUTHOR]

A series of reversible triblock poly(amino acid)s hydrogels with tunable pH ‐ responsivity (pH 3.5–10.0) were synthesized by adjusting the ratio of the blocks. Attributing to the good biodegradability and low cytotoxicity of these triblock poly(amino acid)s, it is obvious that these poly(amino acid)s are potential novel materials in drug delivery and injectable hydrogels. [ABSTRACT FROM AUTHOR]

Diffuse nutrient loss mechanism is complicated and shows remarkably regional differences due to spatial heterogeneities of underlying surface conditions, climate and agricultural practices. Moreover, current available observations are still hard to support the identification of impact factors due to different time or space steps. In this study, an integrated water system model (HEQM) was adopted to obtain the simulated loads of diffuse components (carriers: runoff and sediment; nutrient: total nitrogen (TN) and total phosphorous (TP)) with synchronous scales. Multivariable statistical analysis approaches (Analysis of Similarity and redundancy analysis) were used to assess the regional differences, and to identify impact factors as well as their contributions. Four catchments were selected as our study areas, i.e., Xiahui and Zhangjiafen Catchments of Miyun Basin in North China, Yuliang and Tunxi Catchments of Xin’anjiang Basin in South China. Results showed that the model performances of monthly processes were very good for runoff and good for sediment, TN and TP. The annual average coefficients of all the diffuse components in Xin’anjiang Basin were much greater than those in Miyun Basin, and showed significantly regional differences. All the selected impact factors interpreted 72.87–82.16% of the regional differences of carriers, and 62.72–71.62% of those of nutrient coefficients, respectively. For individual impact factor categories, the critical category was geography, followed by land-use/cover, carriers, climate, as well as soil and agricultural practices in Miyun Basin, or agricultural practices and soil in Xin’anjiang Basin. For individual factors, the critical factors were locations for the carrier regional differences, and carriers or chemical fertilizer for the nutrient regional differences. This study is expected to promote further applications of integrated water system model and multivariable statistical analysis in the diffuse nutrient studies, and provide a scientific support for the diffuse pollution control and management in China. [ABSTRACT FROM AUTHOR]

Summary Flow regimes (e.g., magnitude, frequency, variation, duration, timing and rating of change) play a critical role in water supply and flood control, environmental processes, as well as biodiversity and life history patterns in the aquatic ecosystem. The traditional flow magnitude-oriented calibration of hydrological model was usually inadequate to well capture all the characteristics of observed flow regimes. In this study, we simulated multiple flow regime metrics simultaneously by coupling a distributed hydrological model with an equally weighted multi-objective optimization algorithm. Two headwater watersheds in the arid Hexi Corridor were selected for the case study. Sixteen metrics were selected as optimization objectives, which could represent the major characteristics of flow regimes. Model performance was compared with that of the single objective calibration. Results showed that most metrics were better simulated by the multi-objective approach than those of the single objective calibration, especially the low and high flow magnitudes, frequency and variation, duration, maximum flow timing and rating. However, the model performance of middle flow magnitude was not significantly improved because this metric was usually well captured by single objective calibration. The timing of minimum flow was poorly predicted by both the multi-metric and single calibrations due to the uncertainties in model structure and input data. The sensitive parameter values of the hydrological model changed remarkably and the simulated hydrological processes by the multi-metric calibration became more reliable, because more flow characteristics were considered. The study is expected to provide more detailed flow information by hydrological simulation for the integrated water resources management, and to improve the simulation performances of overall flow regimes. [ABSTRACT FROM AUTHOR]

Understanding the water use strategy of crops is important for maintaining the stability of agricultural production and improving water use efficiency (WUE). Affected by a variety of water sources and hyper-arid climate, the characteristics of root water uptake (RWU) in seed maize are extremely complicated but underestimated in oasis farmlands with shallow groundwater. We hypothesized that isotope (δ2H and δ18O) measurements over three years coupled with a MixSIAR model would reveal the characteristics of RWU in maize. Stable water isotopes in oasis farmlands were continuously observed from 2019 to 2021. Over the growing season, the soil matrix potential increased with soil depth. The isotopes in stem water had high similarity to groundwater, irrigation water, and soil water. The contributions of soil water in 0–20 cm, 20–40 cm, 40–60 cm, and 60–100 cm soil layers to RWU in maize were 29.7%, 12.2%, 14.8%, and 43.3%, respectively. From the jointing stage to the dough stage, the depth of RWU in maize was from shallow to deep; but after the dough stage, the depth of RWU in maize was from deep to shallow. Crops might prefer to absorb more groundwater and irrigation water in oasis farmlands with shallow groundwater. This study provides insights into crop water uptake and agricultural water management in hyper-arid regions. • Root uptake patterns in seed maize were investigated using δ2H and δ18O in hyper-arid regions. • The depth of RWU in maize was "shallow-deep-shallow" pattern with the growing periods. • The contributions of soil water in 0–20 cm and 60–100 cm to RWU in maize were 29.7% and 43.3%. • Maize used more groundwater and irrigation water in oasis farmlands. [ABSTRACT FROM AUTHOR]

Summary Due to the high interactions among multiple processes in integrated water system models, it is extremely difficult, if not impossible, to achieve reasonable solutions for all objectives by using the traditional step-by-step calibration. In many cases, water quantity and quality are equally important but their objectives in model calibration usually conflict with each other, so it is not a good practice to calibrate one after another. In this study, a combined auto-calibration multi-process approach was proposed for the integrated water system model (HEQM) using a multi-objective evolutionary algorithm. This ensures that the model performance among inseparable or interactive processes could be balanced by users based on the Pareto front. The Huai River Basin, a highly regulated and heavily polluted region of China, was selected as a case study. The hydrological and water quality parameters of HEQM were calibrated simultaneously based on the observed series of runoff and ammonia-nitrogen (NH 4 -N) concentrations. The results were compared with those of the step-by-step calibration to demonstrate the rationality and feasibility of the multi-objective approach. The results showed that a Pareto optimal front was formed and could be divided into three clear sections based on the elastic coefficient of model performance between NH 4 -N and runoff, i.e., the dominated section for NH 4 -N improvement, the trade-off section between NH 4 -N and runoff, and the dominated section for runoff improvement. The trade-off of model performance between runoff and NH 4 -N concentration was clear. The results of the step-by-step calibration fell in the dominated section for NH 4 -N improvement, where just the optimum of the runoff simulation was achieved with a large potential to improve NH 4 -N simulation without a significant degradation of the runoff simulation. The overall optimal solutions for all the simulations appeared in the trade-off section. Therefore, the Pareto front provided different satisfactory solutions for users to choose according to their specific objectives. This study is expected to promote the application of multi-objective calibration in water system modeling, and provide scientific and technological supports for the implementation of integrated river basin management. [ABSTRACT FROM AUTHOR]

Investigating the dynamics of energy and water vapor exchange in oasis agroecosystems is important to improve scientific understanding of land surface processes in desert-oasis regions. In this study, water vapor and energy fluxes were obtained by using an eddy covariance technique for two similar irrigated seed maize fields at Yingke and Pingchuan, in northwest China. Seasonal variabilities of evapotranspiration (ET) and relevant environmental and biophysical factors were explored. Results showed that the energy balance closures were reasonable, with energy balance ratio of 0.99 and 0.79 for a half-hourly time scale at Yingke and Pingchuan, respectively. The seasonal changes in net radiation (R n ), latent heat flux (LE), and sensible heat flux (H) of Yingke and Pingchuan were similar. Net radiation was 11.27 MJ m −1 day −1 during the growing season. Latent heat flux accounted for 67.5% of net radiation, sensible heat flux was 25.0%, and soil heat flux was 7.5%. A reverse seasonal change was found in partitioning energy flux into LE and H. The seasonal variation in energy flux partitioning was significantly related to the phenology of maize. During the growing season, ET was 467 and 545 mm, and mean daily ET 2.84 and 3.35 mm day −1 at Pingchuan and Yingke, respectively. “Non-growing” season ET was 15% of the annual ET in the bare field (during October–March) and 85% of the annual ET for maize (during April–September). Daily ET was mainly controlled by net radiation and air temperature, and was significantly affected by leaf area index (<3.0 m 2 m −2 ) and canopy conductance (<10 mm s −1 ). Furthermore, irrigation promoted daily ET greatly during the growing season. Accurate estimation of seed maize ET and determination the controlling factors helps to develop exact irrigation scheduling and improve water resource use in desert-oasis agroecosystems. [ABSTRACT FROM AUTHOR]

Overgrazing has caused serious soil degradation, vegetation destruction, and wind erosion in temperate desert areas of northwestern China. To address this, the Livestock Enclosure Scheme was implemented in 2004 to allow for self-recovery of the overgrazed desert. The aim of this study was to investigate the effect of livestock enclosure on the restoration process by examining changes in the ecological environment of a temperate desert recovering from overgrazing. Vegetation parameters and soil properties under grazing site, 5-year fenced site, and 9-year fenced site were examined in the degraded desert in the Hexi Corridor of China. The results showed that vegetation coverage, height, plant density, richness, diversity, and litter biomass all improved after 5 years of fencing, demonstrating that short-time fencing had a positive effect on vegetation restoration in the temperate desert. Furthermore, 9 years of fencing significantly increased soil organic C (SOC), total N (TN), and total P (TP) in the 0–20 cm soil profile, while available N (AN) and available P (AP) showed the reverse trend. The values of soil C and N storage after 9 years of fencing were almost 5.55 Mg ha − 1 and 0.69 Mg ha − 1 , respectively. Enhanced vegetation caused reductions in soil water near the soil surface (0–30 cm) where vegetation uptake mainly occurred. These findings could offer insight into the development of effective strategies for protecting and enhancing the resilience of a livestock-disturbed temperate desert. [ABSTRACT FROM AUTHOR]

Summary The assessment of flow regime alterations is fundamental in understanding the potential impact of reservoirs and other water infrastructures on aquatic ecosystems and biota. Previously used methods to classify flow regimes have not captured temporal changes between unregulated and regulated flow regimes at individual stations. In this study, a combination of hierarchical classification and trend analysis was used to assess spatial and temporal flow regime alterations in the Huai River Basin, China. Two categories of flow regime indices were selected to characterize the impacts of reservoir and sluice regulation, including the basic flow indices for mean variation, and the cumulative variation indices for long-term alteration. The overall impact of reservoirs and sluices on flow regime included the decrease of high flow magnitudes but the increase of low flow magnitudes through time. Moreover, on average, the flow variability, and the high and low flow frequencies were reduced, while their durations were increased. Reservoirs had a greater impact on flow regimes than sluices. The flow regimes at 18 of 30 stations were altered significantly from a pre-regulation condition and were divided into three main types of alteration corresponding to operational rules of reservoirs and sluices. From a management perspective, water projects in China should address the environmental flow requirements of the rivers, particularly in terms of the hydrologic indices affected mostly by reservoirs and sluices. This study will promote the application of flow regime classification and river restoration in highly regulated basins in China. [ABSTRACT FROM AUTHOR]

The regulation and spatial differences of urban runoffs are of great concern in contemporary hydrological research. However, owing to a shortage of basic data sources and restrictions on urban hydrological simulation functions, simulating and investigating the regulation mechanism behind rainfall-runoff processes remain significantly challenging. In this study, the Time Variant Gain Model (TVGM), a hydrological nonlinear system model, was extrapolated to the hydrodynamic model of an urban drainage network system by integrating it with the widely used Stormwater Management Model (SWMM) to adequately simulate urban runoff events while considering various underlying surfaces and runoff routing modes, such as surface, drainage network and river runoff, in urban regions (i.e., TVGM-SWMM). Moreover, runoff events were characterized using the following four runoff regime metrics: runoff coefficient, capture ratio of annual runoff volume, standardized flood timescale, and the ratio of occurrence time differences between flow and rainfall peak to event duration (peak flow delay time). The characteristics and spatial differences of urban runoff regulations were investigated, and the key impact factors and their relative contributions were identified using multivariate statistical analyses. Four communities were selected as our study areas, consisting of communities from Beijing, Shenzhen, Wuhan, and Chongqing. Our results showed that the TVGM-SWMM performed considerably better than SWMM alone. The comprehensive simulation accuracy of 60% of the events (12/20) improved by 486%, with the bias improving the most, followed by the efficiency coefficient. Barring the runoff coefficient, significant spatial differences were identified at the patch scale for the runoff regime metrics, with differences of 0.43, 0.22, and 0.16 (p<0.05). The key impact factors were the pipe length (r=0.51) in the drainage network system and the forest area ratios (r=0.56), sponge measures (r=0.52), grassland (r=0.48), and impervious surface (r=0.46) in the underlying surfaces. The contributions of the drainage network system and the underlying surfaces were 4.27% and 37.83%, respectively. Regulation in the Beijing community, dominated by grassland regulation, delayed and reduced the peak flow and total runoff volume. In the Shenzhen community, sharp and thin runoff events were mainly generated by impervious surfaces and were not adequately regulated. Forest regulation was the dominant regulation type in the Wuhan community, which reduced the total runoff volume and delayed the peak flow. Waterbody regulation was the primary regulation type in the Chongqing community, which reduced the total runoff volume and peak flow. This study aims to introduce a comprehensive theoretical and technical assessment of the hydrological effects of urbanization and the performance of sponge city construction and provide a reference for urban hydrological model improvements in China. [ABSTRACT FROM AUTHOR]

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

Background: Streoptomyces rimosus M527 is a producer of the polyene macrolide rimocidin which shows activity against various plant pathogenic fungi. Notably, the regulatory mechanisms underlying rimocidin biosynthesis are yet to be elucidated. Results: In this study, using domain structure and amino acid alignment and phylogenetic tree construction, rimR2, which located in the rimocidin biosynthetic gene cluster, was first found and identified as a larger ATP-binding regulators of the LuxR family (LAL) subfamily regulator. The rimR2 deletion and complementation assays were conducted to explore its role. Mutant M527-ΔrimR2 lost its ability to produce rimocidin. Complementation of M527-ΔrimR2 restored rimocidin production. The five recombinant strains, M527-ER, M527-KR, M527-21R, M527-57R, and M527-NR, were constructed by overexpressing rimR2 gene using the promoters permE*, kasOp*, SPL21, SPL57, and its native promoter, respectively, to improve rimocidin production. M527-KR, M527-NR, and M527-ER exhibited 81.8%, 68.1%, and 54.5% more rimocidin production, respectively, than the wild-type (WT) strain, while recombinant strains M527-21R and M527-57R exhibited no obvious differences in rimocidin production compared with the WT strain. RT-PCR assays revealed that the transcriptional levels of the rim genes were consistent with the changes in rimocidin production in the recombinant strains. Using electrophoretic mobility shift assays, we confirmed that RimR2 can bind to the promoter regions of rimA and rimC. Conclusion: A LAL regulator RimR2 was identified as a positive specific-pathway regulator of rimocidin biosynthesis in M527. RimR2 regulates the rimocidin biosynthesis by influencing the transcriptional levels of rim genes and binding to the promoter regions of rimA and rimC. [ABSTRACT FROM AUTHOR]

High regulation of dams or sluices disturbs flow regimes and pollutant transformation process significantly in most basins over the world. The water quality and quantity simulation in highly regulated river basins is always a very complicated task. The Huai River Basin is a typical area in China with the highest density of water projects and serious pollution problems simultaneously. In this paper, a procedure based on Soil and Water Assessment Tool (SWAT) was proposed to carry out the water quantity and quality simulation of Huai River Basin by incorporating the operation rules of dams or sluices into the reservoir regulation module. The water quality module in SWAT is extended to suit the actual situation of river basin in China. The results show that: for runoff simulation, 28 of all the 38 stations (73.7%) have the acceptable performance, with the average correlation coefficient and efficiency coefficient of 0.83 and 0.66, respectively in the calibration period. In the validation period, 17 of all the 34 stations (50%) have the acceptable performance, with the average correlation coefficient and efficiency coefficient of 0.77 and 0.54, respectively. The model performs the worst for reservoirs, little better for sluices and the best for unregulated stations. Comparing to the low flow and high flow simulation of original SWAT model, the low flow simulation of reservoirs and the high flow simulation of sluices are much better because of their different main purposes. For water quality simulation, the standard reaching rates of NH-N and COD are 55.9% (19/34) and 67.6% (23/34) respectively for all the stations, and the average relation coefficients are 0.46 and 0.48 respectively. Comparing with the results of original SWAT model, the improved model better reproduces the long-term water quantity and quality processes in the Huai River Basin of China. This study provides a new approach and reference to understand the variation of water quantity and quality in highly regulated river basin, and is expected as technical support for the environment restoration and integrated management in the basins, especially in China. [ABSTRACT FROM AUTHOR]

Unmanned aerial vehicle (UAV) remote sensing technology is gradually playing a role alternative to traditional field survey methods in monitoring plant functional traits of forest ecology. Few studies focused on monitoring functional trait ecology of underground forests of inaccessible negative terrain with UAV. The underground forests of tiankeng were discovered and are known as the inaccessible precious ecological refugia of extreme negative terrain. The aim of this research proposal is to explore the suitability of UAV technology for extracting the stand parameters of underground forests' functional traits in karst tiankeng. Based on the multi-scale segmentation algorithm and object-oriented classification method, the canopy parameters (crown width and densities) of underground forests in degraded karst tiankeng were extracted by UAV remote sensing image data and appropriate features collection. First, a multi-scale segmentation algorithm was applied to attain the optimal segmentation scale to obtain the single wood canopy. Second, feature space optimization was used to construct the optimal feature space set for the image and then the k-nearest neighbor(k-NN) classifier was used to classify the image features. The features were classified into five types: canopy, grassland, road, gap, and bare land. Finally, both the crown densities and average crown width of the trees were calculated, and their accuracy were verified. The results showed that overall accuracy of object-oriented image feature classification was 85.60%, with 0.72 of kappa coefficient. The accuracy of tree canopy density extraction was 82.34%, for which kappa coefficient reached 0.91. The average canopy width of trees in the samples from the tiankeng-inside was 5.38 m, while that of the outside samples was 4.83 m. In conclusion, the canopy parameters in karst tiankeng were higher than those outside the tiankeng. Stand parameters extraction of karst tiankeng underground forests based on UAV remote sensing was relatively satisfactory. Thus, UAV technology provides a new approach to explore forest resources in inaccessible negative terrain such as karst tiankengs. In the future, we need to consider UAVs with more bands of cameras to extract more plant functional traits to promote the application of UAV for underground forest ecology research of more inaccessible negative terrain. [ABSTRACT FROM AUTHOR]

During the past several decades, the carbon budget in the dryland ecosystem has experienced great variation under the joint impact of climate change and anthropogenic interference. How the net ecosystem productivity (NEP) responds to climate change and human interference in the Qilian Mountains (QLM), Northwest China, remains unclear. To fill these gaps, we first estimated the NEP in the QLM and then quantified the independent and interactive influences of natural environment factors, climatic factors, and human activity intensity on the NEP change from 2000 to 2020 by linking the Geodetector and structural equation models. The NEP of the QLM showed a significant increase during the recent 20 years, and 78.93% of the QLM experienced a significant increase in NEP; while only 4.83% of the area in the QLM experienced a decreasing trend, which is dominantly located on the southeast edge, surrounding the Qinghai Lake, and the midland of the QLM. The area percentage of the carbon sink region increased from 47% in 2000 to 62% in 2020. The natural environment factors (e.g., altitude and soil type) and climate factors (e.g., temperature and precipitation) were the dominant factors that determine the spatial distribution of NEP. Compared with a single factor, the interaction of pairs of factors enhanced the influence strength on NEP. The natural environment factors indirectly affected NEP change through influencing human activities intensity and climatic factors. Human activities intensity played a medium indirectly negative effect on NEP, while climatic factors exerted strong direct and indirect positive influences on NEP. The contributions of human activity intensity, climatic factors, and natural environment on NEP change in the QLM were 33.5%, 62.3%, and 38.3%, respectively. Overall, warming and wetting shifts in meteorological conditions offset the negative impact of human activities on NEP in the QLM, and the QLM has acted as a growing carbon sink in the past 20 years. [ABSTRACT FROM AUTHOR]

China frequently suffers from considerable and disastrous flash floods with wide areal coverage and high frequency. Obtaining useful information to support flash flood management and decision-making is challenging for massive flash flood events that vary greatly in spatio-temporal characteristics. In this study, hydrological modelling approach (CNFF) and cluster analysis were integrated to assess simulation reliability of entire flash flood processes including both hydrographs and behavior characteristics in a manner of similarity classification, rather than at event scale. A total of 207 hourly events from 13 mountainous catchments with diverse physiographic and meteorological characteristics across China were selected for study. Representative flash flood types were classified using normalized hydrographs with diverse spatio-temporal patterns by k -means clustering algorithm. For individual flash flood types, simulation reliability of CNFF was assessed in capturing corresponding hydrographs, seven behavior metrics measuring flash flood magnitude, intensity, occurrence time, flood timescale, rates of change and variability, and their uncertainties. Results showed that three (fast, intermediate and slow) flash flood types were identified from all the flash flood events with overall average silhouette index of 0.45. Hourly hydrographs of three flash flood types were well reproduced by CNFF, with absolute average relative error of runoff within 15% and Nash-Sutcliffe Efficiency above 0.55. All the behavior metrics were the most accurately reproduced for slow flash flood type with the least average relative root-mean-square error (0.30), followed by intermediate (0.52) and fast (0.58) types. Moreover, the slow flash flood type had the most reliable but greatest uncertainty interval of both hydrograph and behavior metrics, with average relative interval length being 1.24 and 71.96%, and 93.10% and 100% of observations contained in 95% confidence interval, respectively. This study provided efficient and detailed information for flash flood management, and extended application scope of hydrological models to encompass flash flood types and behavior metrics. Unlabelled Image • Both hydrograph and behavior metrics are simulated for similar flash flood types. • Fast, intermediate and slow flash flood types are grouped using massive hydrographs. • Hourly hydrograph is well simulated for three flash flood types and the most reliable for slow type. • Flood behavior metrics are the best and most reliably simulated for slow flash flood type. [ABSTRACT FROM AUTHOR]

Oasis degradation and terminal lake shrinkage are prevalent consequences of the disputed distribution of water resources in inland river basins, hindering regional sustainable development. The Ecological Water Diversion Project (EWDP) is regarded as an important measure to restore the desert-oasis ecosystem in inland river basins, and thus it is essential to comprehensively evaluate the response of eco-hydrological and socioeconomic systems to the EWDP. Based on multiple indicators, we used trend analysis, linear regression, partial least square regression, and structural equation model to disentangle the quantitative effects of the EWDP on the change of eco-hydrological and socioeconomic conditions in the Ejina Oasis (EO) in the lower reaches of the Heihe River in northwest China. Our results indicate that the ecological deterioration was prevalent before the execution of the EWDP, including the increase of groundwater depth, the disappearance of lakes, the decrease of NDVI. After the EWDP, runoff released to EO increased 69.15%, the mean groundwater depth decreased 0.48 m, 52.28% of the study area showed a significant increase in NDVI, areas of forest and grassland increased 20.17 and 25.65 km2, respectively. The EWDP improved the hydrological regime and prompted the recovery of the oasis. Besides, socioeconomic development was facilitated under the restoration of the eco-hydrological conditions, characterized by the expansion of farmland and the thrive of the tourism industry. The hydrological variables promoted the improvement of the ecological condition with a direct strength of 0.93 and facilitated the development of the socioeconomic conditions in EO with an indirect strength of 0.84. Runoff was the most important positive contributor both to the NDVI and GDP in EO. This comprehensive evaluation framework can offer valuable insight for water resources management and sustainable development in the inland river basin of arid areas. [ABSTRACT FROM AUTHOR]

• Budyko-based framework is improved for attribution of streamflow signature changes. • Streamflow signatures show clearly nonlinear relationships with climate variables. • Human activities play dominant roles in decreasing overall streamflow signatures. Streamflow has been complexly altered by climate change and human activities in major rivers worldwide. The traditional Darwinian approach for impact assessment of climate change and human activities mainly focuses on variations in annual streamflow, but ignores other critical streamflow characteristics (e.g., high- and low-flow signatures). In our study, seven streamflow metrics were adopted to characterize the main streamflow signatures including average, low and high flows, and the Budyko-based method was extended based on the derived differential equation of streamflow signature change to separate individual impacts of climate change and human activities. The Yellow River Basin, China was selected as the study area because of its high intensity of human activities, and daily runoff observation series from 1960 to 2015 at four stations from the source region to the downstream region were used for the assessment. The assessment results were also compared with those estimated by the hydrological modeling method for validation. The results show that all streamflow signatures at the four stations have evidently declined after the 1980s, particularly for high-flow magnitudes. Both climate change and human activities decrease most of streamflow signatures, and human activities play major roles, which are gradually enhanced from the source region to the downstream region. The contributions of human activities are from −66.85% to −56.68% in the Tangnaihai controlled catchment, from −96.93% to −54.59% in the Qingtongxia controlled catchment, from −83.61% to −57.49% in the Longmen controlled catchment, and from −91.02% to −57.29% in the Lijin controlled catchment. The most impacted signature is the average flow in the non-flood season, followed by the annual maximum flow. The estimated contributions of climate change and human activities match well with those estimated by the hydrological modeling method, particularly for the high- and average-flow signatures with contribution deviations less than 10%. However, the estimated contributions to the low-flow signatures are quite different likely due to large uncertainty of low flow estimation. This study is expected to provide insights into the streamflow variations basin wide and provide scientific foundations for ecological protection and high-quality development of the Yellow River Basin, China. [ABSTRACT FROM AUTHOR]

Understanding temporal and spatial changes in precipitation has far-reaching implications for watershed development and risk assessment under global climate change. In our study, temporal and spatial variability in precipitation concentration (PC) in Central Asia (CA) from 1980 to 2017, measured with the precipitation concentration index (PCI) and Gini Coefficient (GC), was analyzed using interpolated precipitation from the Climate Prediction Center (CPC) and National Centers for Environmental Prediction (NCEP). The results showed that: (1) interpolated precipitation increased significantly, with significant mutations (P <.5) mainly concentrated between 2000 and 2010; (2) the spatial distribution of the CPC PCI was opposite to that of the NCEP PCI, and fluctuations in CPC GC were larger than that of the NCEP, which indicated that the precipitation data from NCEP was more uniform over the year; (3) for two of three interpolation methods, CPC PC displayed significant mutations in southern CA between 1985 and 2005, while significant (P <.05) mutations in NCEP PC were relatively concentrated in southern CA between 1987 and 2005; (4) although the El Niño Modoki Index (EMI), Pacific Decadal Oscillation (PDO), Nino 3.4, and Southern Oscillation Index (SOI) displayed resonance relationships with CPC PCI, there were no significant abrupt changes in the resonance correlation. In the NCEP data, EMI, PDO, Nino 3.4, and North Atlantic Oscillation (NAO) led to mutations in the resonance relationship with PCI. Our research proved that the change in PC in CA had closely relationship with some teleconnection indices. • The characteristics from different product were different over Central Asia. • The mutations for different interpolated precipitation were different. • Precipitation concentration had a gradual trend in space over Central Asia. • More than one teleconnection index impacted on the precipitation concentration. [ABSTRACT FROM AUTHOR]

Under climate change, droughts are causing increasingly larger damages around the world, attracting the attention of governments and researchers. In this study, the terrestrial water storage anomalies (TWSA) obtained from a Gravity Recovery and Climate Experiment (GRACE) were coupled with precipitation, creating a Combined Climatological Deviation Index (CCDI). This index was used to analyze the drought events that occurred in the major basins of Central Asia between April 2002–June 2017. The main conclusions are as follows: (1) the certain but not significant (i.e., p >.05) impacts of precipitation were detected on the total water storage anomalies (TWSA) of three basins (i.e., Irtysh River Basin (IRB), Syr Darya Basin (SDB), and Amu Darya Basin (ADB)) that originate from the Tienshan Mountains based on the correlation coefficient between precipitation and terrestrial water storage (TWS); (2) the Drought Severity Index (DSI), the Palmer Drought Severity Index (PDSI), and the Standardized Precipitation Index over a 12-month scale (SPI12) were related to the CCDI in the major basins of Central Asia, suggesting that the CCDI can be applied effectively to assess the drought characteristics of these basins; (3) the most severe drought events detected by the CCDI in the IRB, SDB, and ADB occurred in 2012, 2014, and 2014, respectively. A humidification trend was observed for the IRB, while a drought trend was observed in the SDB and ADB. Therefore, it appears that the CCDI can be effectively applied to determine the severity of droughts, increase water-saving awareness, and avoid the effects of droughts. • Precipitation has little effect on TWS in Central Asia. • CCDI can character the drought events in Central Asia well. • The drought severity from CCDI was more severe than that from other traditional drought indices. • All the drought indices were discovered the obvious drought events in Central Asia during 2008–2009. [ABSTRACT FROM AUTHOR]

Two new iridoid glucosides, named diffusosides A and B, were isolated from the aerial part of Hedyotis diffusa Willd. Their structures were elucidated by 1D-, 2D-NMR spectroscopic analysis and HRESIMS. These two compounds showed no cytotoxic activity against SMMC-7721, SW480, SW620, Bel7402, and HepG2 cells. [Copyright &y& Elsevier]

• Infiltration is directly affected by soil moisture, rather than rainfall duration. • Horton infiltration equation is improved by adopting soil moisture variation. • Improved equation is better in simulation performance and uncertainty intervals. Soil water infiltration simulation is a subject receiving great interest in hydrological cycle modelling. The traditional Horton equation is based on the curve of infiltration capacity-rainfall duration time. However, the infiltration process is directly affected by soil moisture content, rather than rainfall duration. The objective of this study was to determine a relationship between infiltration capacity and soil moisture content in order to improve the Horton infiltration equation. Artificial rainfall-infiltration experiments were used to determine a series of power functions. The improved equation was cross-validated with observations from 32 experiments of multiple rainfall intensities and antecedent soil moisture. The simulation performance and uncertainty of the improved equation were compared with those of the original Horton equation to verify its accuracy. The results showed that infiltration rate decreases nonlinearly as soil moisture increases, and finally approaches a stable infiltration rate when the soil is saturated. Overland flow simulations by the improved Horton equation closely matched the observations from all 32 experiments over a soil moisture range of 0.222–0.349 m3/m3. The simulation performance was rated as good for most of the experiments for both the calibration and validation data sets. Compared with the original Horton equation, the simulation performance of the improved equation clearly improved estimation of infiltration, particularly as quantified by the Nash-Sutcliffe efficiency coefficient (NSE) and the coefficient of determination (R 2). The number of simulations with NSE values greater than 0.65 increased 11.59% and 2.50% for the calibration and validation data sets, respectively. The number of simulations with R2 values greater than 0.90 increased 31.14% and 22.50%, respectively. The uncertainty intervals of the improved Horton equation became a little greater than those of the original Horton equation. For all 32 experimental simulations, the average relative length of the uncertainty interval at the 95% confidence level increased from 40.52% with the original Horton equation to 49.17% with the improved Horton equation. The number of observations falling within the 95% confidence interval increased from 92.13% to 95.94% with the improved Horton equation. Most of the observations were accurately simulated using the improved Horton equation. The greatest improvements in simulating overland flow were seen for the experiments with low flow simulations. The study results provide insights into soil infiltration mechanisms, and also provide references to support improved infiltration simulation by considering soil moisture variation. [ABSTRACT FROM AUTHOR]

• Soil respiration including winter CO 2 efflux was studied in the desert-oasis region. • Annual soil CO 2 emissions varied from 176 to 918 g C m−2 across the study ecosystems. • The ratio of cold season CO 2 emissions to the annual was 6–15% across ecosystems. • Land use conversion influenced soil respiration across the desert-oasis ecoregion. Quantifying annual soil CO 2 emissions and the effects of physical and geochemical factors on soil CO 2 efflux will improve the carbon budget estimates, as well as enhance predictions of how soil CO 2 emission will response to climate change in arid areas. To data, variability in soil respiration rates caused by land use conversion in the desert-oasis ecoregion of Northwest China remains poorly characterized, especially the contribution of cold season (November-February) CO 2 emission. Soil respiration was measured in a Haloxylon ammodendron desert shrubland, a Zea mays cropland, a Populus gansuensis forest, and a Tamarix chinensis Lour wetland using a LI-COR 8100 Soil Respiration Observation System from April 2016 to March 2019. Annual soil CO 2 emissions totaled 176, 778, 918, and 397 g C m−2 in the desert shrubland, cropland, forest, and wetland, respectively. The ratio of cold season CO 2 emissions to the annual varied from 6 to 15% across ecosystems. Therefore, ignoring cold season CO 2 emissions would lead to underestimates of carbon losses in the desert-oasis ecoregion. The soil respiration rate at 10 °C was influenced by soil organic carbon content in all four ecosystems. In the cropland and forest, soil respiration rate was affected by the interaction of soil moisture and soil temperature, while in the wetland and desert shrubland, soil respiration was sensitive to a single factor, soil temperature. Land use conversion induced differences in organic matter accumulation, soil temperature, and soil moisture, and as a consequence, produced variability in soil respiration rates across the desert-oasis ecoregion. [ABSTRACT FROM AUTHOR]

• Straw incorporation changed the N effects on soil bacterial community composition. • Straw incorporation enhanced the cellulolysis function and relevant taxa abundance. • N fertilization stimulated most of the C transformation and N cycling processes. • Reducing N fertilization will not change microbial taxa profiles and functions. • The abundance of copiotrophic taxa decreased at the mid-growing season. Integrating nitrogen (N) fertilization with crop residue amendments is usually used to enhance soil nutrient levels and promote crop growth in regions with intensive agriculture. However, the interactive effects of straw incorporation and N fertilization on the abiotic and biological properties of soil are not fully understood, especially under field conditions at different crop growth stages. In this study, we estimated the dynamic changes in the soil physicochemical properties and bacterial communities in response to N fertilization, straw incorporation, and their combinations during the maize growing season in black soil region in Harbin, China. N fertilization increased the relative abundance of the typical copiotrophic bacterial taxa, Alphaproteobacteria, but reduced that of the oligotrophic group, Acidobacteria. The straw incorporation enhanced the relative abundance of Bacteroidetes and Gammaproteobacteria, within which a variety of cellulolysis-related species phylogenetically fell. Interestingly, the straw amendments changed the effects of N fertilization on the overall soil bacterial community composition, possibly by altering the soil total carbon, C/N ratio, fixed ammonium, and moisture level. N fertilization stimulated most of the carbon (C) transformation and N cycling processes, and the straw incorporation increased the cellulolysis, N fixation, ureolysis, ammonia oxidation and denitrification functions. There were no differences in the soil chemical properties, microbial taxa profiles or predicted functions between the conventional N fertilizer usage (high N level) and the optimized N fertilization management scheme (low N level), irrespective of straw incorporation, implying that moderately reducing the usage of N fertilizer will not change the ecosystem service and function in this organic matter-rich black soil region. The relative abundance of the copiotrophic bacterial taxa decreased at the mid-growing season, which might be caused by the low soil C and N availability. In contrast, the oligotrophic bacterial groups showed predominance at the mid-growing season, which might aim to mineralize soil organic matter to meet the growth needs of both the crops and the microbes. The nitrifiers (Nitrospirae) and nitrification process were sharply activated at the mid-growing season, especially under the straw amendment condition, inferring that the combination of straw application with N fertilizer could serve as an effective measure for improving soil fertility in Northeast China. The present study enhanced our knowledge on the dynamic changes in soil biotic and abiotic parameters in response to straw incorporation and N fertilization during the maize growing season. Still, this study provides a reference for designing an environmentally friendly fertilization strategy that both alleviates environmental stress and maintains a high crop yield in Northeast China. [ABSTRACT FROM AUTHOR]

Propagation from meteorological to hydrological drought events is crucial for understanding drought variation mechanisms and their consequences. Most previous studies were implemented using various standardized drought indices at month scale, which were difficult to reveal the physical processes and insufficient to characterize the comprehensive propagation characteristics (e.g., propagation time, duration, and severity) from meteorological to hydrological drought events. Furthermore, the impact mechanisms of underlying surfaces on drought propagation remained unclear. This study identified the paired relationships between meteorological and hydrological drought events and investigated their comprehensive propagation characteristics at the hydrologic response unit scale using the Soil and Water Assessment Tool (SWAT), run theory and paired analysis. The impact of underlying surfaces (e.g., land use, soil type, and slope) on drought propagation was further assessed using the Student's t -test at the 95% confident level. The upper middle Yuanjiang River Basin in China, which is prone to drought and exhibits diverse underlying surface conditions, was selected as the study area. Results indicate that the SWAT model optimally simulates the monthly streamflow with the Nash-Sutcliffe efficiency being ≥0.75 and the RMSE-observations standard deviation ratio being ≤0.50. Four main propagation types are identified, i.e., one-to-one, many-to-one, one-to-many, and many-to-many, in which the first two types are the dominant ones, accounting for 86.7% and 13.3% of total paired events, respectively. More than 85% of the study area exhibits a propagation time of ≤2 months, especially in the headwater area and the right bank of Lvzhijiang River. Drought duration and severity are amplified during the propagation process in 60.8% and 60.3% of the study area, respectively. Drought propagation time, duration, and severity are mainly controlled by soil and slope, and are slightly affected by land use type. The propagation time is quite short in areas with a high soil infiltration rate and steep slope, and the drought duration and severity are amplified in areas with a low soil infiltration rate and gentle slope. This study aims to provide deep insights on propagation from meteorological to hydrological drought considering various underlying surfaces, and further provides a scientific basis for the drought propagation mechanism and for drought disaster prevention and adaptation. • Drought propagation is analysed on time, duration, and severity by paired events. • Only 55% of meteorological drought events trigger hydrological drought events. • Areas with lower soil infiltration rates and gentler slopes show shorter duration and higher severity. • Drought propagation is impacted evidently by soil, followed by slope and land use. [ABSTRACT FROM AUTHOR]

Flash floods present significant heterogeneity over both space and time due to diverse topographic, geomorphologic, and hydro-meteorological conditions of catchments. Accurate identification and simulation of typical flash flood types are of great significance for the mitigation of flash flood disasters at the national scale. Three flood peak indices and dynamic indices were adopted to characterize the behavioral variability of flash floods. The typical flash flood types and corresponding behavior indices were identified and simulated using statistical analysis (i.e., principal component analysis, dynamic K-means clustering, and analysis of similarity) and hydrological modelling (i.e., HEC and XAJ models). There were 177 flash flood events at the hourly scale being selected for case study from eight catchments with various climatic and geographic characteristics. Results showed that all the flash flood events were clustered into three types (named Types 1, 2, and 3). Type 1 was characterized by low peak flow intensity, early flood peak occurrence time, and thin flood process with short duration. Type 2 was characterized by low peak flow intensity, late flood peak occurrence time, and flat flood process with long duration. Type 3 was characterized by high peak flow intensity and late flood peak occurrence time. Flash flood types showed high consistency with their influencing factors (e.g., catchment forest ratio and drainage area, occurrence time and magnitude of maximum storm intensity, and concentration of a storm event). The simulation performances were basically the same for HEC and XAJ models. As for flash flood event simulations, the average relative error varied from 23.25% to 27.98%, from 11.95% to 18.19%, and from 8.30% to 18.25% for Types 1, 2 and 3, respectively. The average Nash-Sutcliffe efficiency coefficient varied from 0.39 to 0.54, from 0.76 to 0.85, and from 0.86 to 0.91, respectively. As for the six flash flood behavior indices simulations, the average relative root-mean-square error (RMSEr) varied from 0.37 to 0.69, from 0.37 to 0.41, and from 0.18 to 0.25 for Types 1, 2, and 3, respectively. The average correlation coefficient (r) varied from 0.52 to 0.68, from 0.78 to 0.85, and from 0.88 to 0.94, respectively. The flood peak indices were the best simulated for Types 2 and 3 with RMSEr varying from 0.18 to 0.28 and r varying from 0.86 to 0.91. The flood dynamic indices were the best simulated for Type 3 with RMSEr varying from 0.19 to 0.21 and r varying from 0.91 to 0.97. The study provided detailed flood information supports for flood management at catchment scale, and also provided new insights into flash flood simulations in small and medium-sized catchments from perspective of flood behavioral processes. [ABSTRACT FROM AUTHOR]

Epilithic algal community structure and function are important indicators of stream ecosystem health and are sensitive to ambient environmental changes. In this study, we examined the impact of light and nutrients on epilithic algal community structure and function by an in situ nutrient addition and shaded canopy experiment in subtropical streams in China. Epilithic algae structure, dominated by diatoms, was significantly different with nutrient addition and light reduction. Nutrient addition increased the epilithic algae and diatom density, colonial life-forms, planktonic diatoms, and high-profile diatoms but decreased the low-profile diatoms. The shaded canopy increased the low-profile diatoms but decreased the adnate life-forms, planktonic diatoms, and high-profile diatoms. Epilithic metabolism, including gross primary production (GPP), net daily metabolism (NDM), and production/respiration (P/R) increased with nutrient addition, while respiration (R) only increased when the canopy was open with nutrient addition. Epilithic GPP had a significant positive correlation with diatom density (P < 0.01, R2 = 0.9425). Our results indicated that changes in epilithic algae structure due to changes in riparian canopy coverage and nutrients could affect epilithic algal community function. Quantifying the impacts of such drivers on community structure and function is vital to effective river management. [ABSTRACT FROM AUTHOR]

China has begun a rapid move towards Sponge City implementation, which will include widespread installation of various Low Impact Development (LID) stormwater infrastructure. Ambitious goals have been set for all Sponge Cities, including a target capture rate of 80–85% of annual precipitation in Beijing. However, there has so far been limited investigation into whether these goals are obtainable at the catchment scale given the physical restrictions of the existing urban landscape. This paper demonstrates the use of long-term continuous hydrologic modelling to evaluate the potential of meeting rainfall capture goals over a long time period for a case study area in Beijing. Detailed land cover classification derived from satellite imagery aided in the parameterization of a SWMM (Stormwater Management Model) model representing a 133 km2 urban study area. The calibrated and validated model demonstrated satisfactory agreement between computed and observed runoff for a variety of precipitation events ranging from 10 to 207 mm. A synthetic high resolution rainfall time series was generated from historic daily observations then used as input to run the model continuously for a 35 year period. Feasible LID model scenarios based on varying degrees of implementation of rain gardens, permeable pavements and green roofs were compared in terms of their potential volume capture of annual rainfall. Modelling results demonstrated that the conversion of 30% of roof area to green roof, 10% of green areas to rain gardens and 35% of paved areas to permeable pavement could increase the baseline volume capture ratio from 59.9% to 82.2%, indicating that Sponge City goals can be met within the case study area with realistic levels of LID implementation. This study provides a decision-making basis for future planning in the study area. • Satellite imagery based hydrologic model shows good agreement with observed flows. • Continuous modelling approach suggested for evaluation of Volume Capture Ratio. • >80% of annual rainfall captured with moderate catchment wide implementation of LID. [ABSTRACT FROM AUTHOR]

Droughts are extremely widespread natural disasters, which cause the most severe losses among natural disasters. The comprehensive drought risk in Northwest China (NWC) was evaluated based on the self-calibrating (SC) Palmer Drought Severity Index (PDSI) and copula method. The major conclusions are the following: (1) based on the rotated empirical orthogonal function (REOF), a significant consistency in the spatial distribution of the monthly averaged SC-PDSI was observed in NWC, especially in the subregions Inner Mongolia Plateau (IM), Hexi Corridor (HX), and Qiangtang Plateau (QT); (2) the largest frequency was obtained for slight drought and slight wet conditions, while extreme drought and extreme wet showed the lowest values; (3) with respect to the PDSI-th, the Clayton, Arch12, Arch12, Arch12, Arch12, and Frank played the major roles in the copula weight in the subregions IM, HX, Qinghai River Basin (QH), QT, North Xinjiang (NXJ), and South Xinjiang (SXJ), respectively. In terms of PDSI-pm, Arch12, Clayton, Gaussian, Arch12, Clayton, and Clayton dominated the weights of multi-copula functions in the regions IM, HX, QH, QT, NXJ, and SXJ, respectively; and (4) the frequency and probability of droughts in each area differed. The least drought events occurred in the QT and the most emerged in the HX for SC-PDSI. [ABSTRACT FROM AUTHOR]

Reference evapotranspiration ( ET 0 ) is important for agricultural, environmental and other studies, and understanding the attribution of its change is helpful to provide information for irrigation scheduling and water resources management. The present study investigates the attribution of the change of ET 0 at 49 meteorological stations in the middle reaches of Yellow River basin (MRYRB) of China from 1960 to 2012. Results show that annual ET 0 increases from the northwest to the southeast of MRYRB in space. We find that annual ET 0 clearly presents a zigzag change pattern rather than a monotonically change during the whole period. The detected three breakpoints at 1972, 1988 and 1997 divide the whole period into four subperiods. The sensitivity analysis indicates that the ET 0 is the most sensitive to surface solar radiation ( Rs ), followed by relative humidity ( RH ) and mean air temperature ( T ), and the least sensitive to wind speed ( u ) in our study area. Furthermore, we find that ET 0 is becoming less sensitive to RH and more sensitive to T during 1960–2012. The attributions of the change in ET 0 vary largely at different regions and subperiods. The declined wind speed is the dominant factor, followed by Rs to the ET 0 reduction during 1960–2012. Further analysis shows that Rs and u are the two major contributing factors that control the change of ET 0 at most stations and during most subperiods. Our study confirms that the change of ET 0 is influenced by the complex interactions of climatic factors, and the dominant factor to the change of ET 0 is different in various regions and time periods. The results presented here can provide a reference for agricultural production and water resources management in MRYRB as well as other semi-arid and semi-humid regions. [ABSTRACT FROM AUTHOR]