Transport Stream Research Articles

Comparative Analysis of Machine Learning Methods and a Physical Model for Shallow Landslide Risk Modeling

Shallow landslides restrict local sustainable socioeconomic development and threaten human lives and property in loess tableland. Therefore, the appropriate creation of risk maps is critical for mitigating shallow landslide disasters. The first task to be done was to evaluate the vulnerability of shallow landslides based on a machine learning model (random forest (RF), a support vector machine (SVM) and logistic regression (Log)), and a physical model (SINMAP) in the loess tableland area. By comparing the differences, the best method for evaluating the vulnerability of shallow landslide was selected. The nonlinear response relationship between shallow landslides and environmental factors was quantified based on the frequency ratio. Multicollinearity analysis was used to identify 10 factors that were applied on ML to construct the spatial distribution model. The SINMAP model used a DEM and soil physical parameters to determine the stability coefficient of the study area. The results showed that (1) shallow landslides in Dongzhiyuan mainly occurred on shady slopes with an elevation of 1068–1249 m, a slope gradient of 36°–60° and a concave shape. The stream power and stream transport indexes increased with increasing rainfall erosion, making shallow landslides likely. The susceptibility of shallow landslides changed parabolically with the change in the NDVI and mainly occurred in grassland and shrubland. (2) The four methods performed similarly in predicting the sensitivity of shallow landslides. The high-incidence areas were on both sides of eroded gully slopes. The tableland and gully bottom areas were not prone to shallow landslides. (3) The highest area under the curve (AUC) values were generated from the RF training and validation datasets of 0.92 and 0.93, respectively, followed by SVM AUC values of 0.91 and 0.92, respectively; Log AUC values of 0.91 and 0.89, respectively, and the SINMAP model AUC values of 0.69 and 0.74, respectively. In conclusion, the RF model best predicted the susceptibility of shallow landslides in the study area. The results provide a scientific basis for disaster mitigation on the Loess Plateau.

Exploring tracer information in a small stream to improve parameter identifiability and enhance the process interpretation in transient storage models

Abstract. The transport of solutes in river networks is controlled by the interplay of processes such as in-stream solute transport and the exchange of water between the stream channel and dead zones, in-stream sediments, and adjacent groundwater bodies. Transient storage models (TSMs) are a powerful tool for testing hypotheses related to solute transport in streams. However, model parameters often do not show a univocal increase in model performances in a certain parameter range (i.e. they are non-identifiable), leading to an unclear understanding of the processes controlling solute transport in streams. In this study, we increased parameter identifiability in a set of tracer breakthrough experiments by combining global identifiability analysis and dynamic identifiability analysis in an iterative approach. We compared our results to inverse modelling approaches (OTIS-P) and the commonly used random sampling approach for TSMs (OTIS-MCAT). Compared to OTIS-P, our results informed about the identifiability of model parameters in the entire feasible parameter range. Our approach clearly improved parameter identifiability compared to the standard OTIS-MCAT application, due to the progressive reduction of the investigated parameter range with model iteration. Non-identifiable results led to solute retention times in the storage zone and the exchange flow with the storage zone with differences of up to 4 and 2 orders of magnitude compared to results with identifiable model parameters respectively. The clear differences in the transport metrics between results obtained from our proposed approach and results from the classic random sampling approach also resulted in contrasting interpretations of the hydrologic processes controlling solute transport in a headwater stream in western Luxembourg. Thus, our outcomes point to the risks of interpreting TSM results when even one of the model parameters is non-identifiable. Our results showed that coupling global identifiability analysis with dynamic identifiability analysis in an iterative approach clearly increased parameter identifiability in random sampling approaches for TSMs. Compared to the commonly used random sampling approach and inverse modelling results, our analysis was effective at obtaining higher accuracy of the evaluated solute transport metrics, which is advancing our understanding of hydrological processes that control in-stream solute transport.

Quantifying Antibiotic Distribution in Solid and Liquid Fractions of Manure Using a Two-Step, Multi-Residue Antibiotic Extraction.

Antibiotic distribution and analysis within liquid and solid fractions of manure are highly variable due to each compound's respective physiochemical properties. This study developed and evaluated a uniform method extracting 10 antibiotics from 4 antibiotic classes (tetracycline, sulfonamides, macrolides, and β-lactam) from unprocessed manure, solid-liquid separated manure, and composted solids. Through systematic manipulation of previously published liquid chromatography tandem mass spectrometry methods; this study developed an extraction protocol with optimized recovery efficiencies for varied manure substrates. The method includes a two-step, liquid-solid extraction using 10 mL of 0.1 M EDTA-McIlviane buffer followed by 10 mL of methanol. Antibiotics recoveries from unprocessed manure, separated liquids, separated solids, and heat-treated solids using the two-step extraction method had relative standard deviations < 30% for all but ceftiofur. Total antibiotic recoveries were 67-131% for tetracyclines, 56% for sulfonamide, 49-53% for macrolides, and 1.3-66% for β-lactams. This is the first study to use one protocol to assess four classes of antibiotics in liquid and solid manure fractions. This study allowed for more precise risk assessment of antibiotic transport in manure waste stream applied to fields as a liquid or solid compost.

Turbulent Reacceleration of Streaming Cosmic Rays

Subsonic, compressive turbulence transfers energy to cosmic rays (CRs), a process known as nonresonant reacceleration. It is often invoked to explain the observed ratios of primary to secondary CRs at ∼GeV energies, assuming wholly diffusive CR transport. However, such estimates ignore the impact of CR self-confinement and streaming. We study these issues in stirring box magnetohydrodynamic (MHD) simulations using Athena++, with field-aligned diffusive and streaming CR transport. For diffusion only, we find CR reacceleration rates in good agreement with analytic predictions. When streaming is included, reacceleration rates depend on plasma β. Due to streaming-modified phase shifts between CR and gas variables, they are slower than canonical reacceleration rates in low-β environments like the interstellar medium but remain unchanged in high-β environments like the intracluster medium. We also quantify the streaming energy-loss rate in our simulations. For sub-Alfvénic turbulence, it is resolution dependent (hence unconverged in large-scale simulations) and heavily suppressed compared to the isotropic loss rate v A · ∇P CR/P CR ∼ v A/L 0, due to misalignment between the mean field and isotropic CR gradients. Unlike acceleration efficiencies, CR losses are almost independent of magnetic field strength over β ∼ 1–100 and are, therefore, not the primary factor behind lower acceleration rates when streaming is included. While this paper is primarily concerned with how turbulence affects CRs, in a follow-up paper we consider how CRs affect turbulence by diverting energy from the MHD cascade, altering the pathway to gas heating and steepening the turbulent spectrum.

Some aspects of flow over a non-isothermal unsteady stretched exterior fixed in porous medium among heat production/amalgamation

The aspire of this article is to examine the consequences of warmth production/amalgamation on border level stream of sticky liquid due to an uneven stretched piece in absorbent medium having a variable exterior hotness. Resemblance answers of the altered leading equations are attained and the numerical answers of those self-alike equations are gained by shooting process. The characteristics of stream and warmth transport for dissimilar data of related parameters are examined and analyzed in detail. Liquid speed and hotness reduce due to rising values of unsteadiness parameter. Liquid speed reduces by means of the rising permeability parameter of the medium ensuing an augmentation in thermal meadow in stable and uneven cases. Flow field is unaltered by the indexes that cause the temperature disparity but it is worth mentioning that the indexes which settle on the disparity of the piece hotness respectively with space and instance, both be liable to boost the hotness disparity and in that way also the Nusselt number. Speed of heat transport augments with growing heat foundation parameter. Thus uneven stretched sheet makes the replica appropriate to a range of manufacturing sectors.

Changes in Large-Scale Fall Extreme Precipitation in the Mid-Atlantic and Northeast United States, 1979–2019

Abstract Global Historical Climate Network (GHCN) data are used to characterize changes in large-scale fall extreme precipitation in the mid-Atlantic and the northeast United States. Days with the highest regional extreme precipitation total [extreme precipitation (EP) days] are sorted into weather types based on tropical cyclone (TC), atmospheric river (AR), and extreme integrated water vapor transport (IVT) influences. Increased cumulative precipitation from EP days is attributed primarily to three sources. First, over the mid-Atlantic states, Pennsylvania, and eastern New England, large increasing trends are found in precipitation occurring on EP days attributed to TC-related weather types. These increases are due to a late-1990s increase in TC frequency, which manifests primarily as increased TC remnants in the mid-Atlantic area. Second, over New York State and central and northern New England, there are increasing trends in EP day precipitation from AR-related weather types. Finally, there is evidence of increasing extreme IVT-related precipitation in the absence of ARs and TCs. However, when taking into account prior TC influences, it is found that a combination of TC-related weather types accounts for much of the increasing EP day precipitation trend. These trends are then compared to EP day synoptic changes relating to atmospheric moisture content and transport. Results indicate that fall EP days have become warmer and moister, but that this does not necessarily translate to higher IVT because wind speeds have stayed the same or slowed. This is consistent with fall climatological changes during the 1979–2019 analysis period, including higher atmospheric water content and slowed westerlies in the vicinity of the mid-Atlantic. Significance Statement This paper sorts days with high extreme precipitation totals in the mid-Atlantic and northeast United States fall into categories based on the presence of factors such as tropical cyclones (TCs), atmospheric rivers (ARs), and other extreme moisture transport. These days have become more frequent between 1979 and 2019, in part due to events with TC influences. However, the synoptic environment on extreme days has also changed, becoming warmer and moister. Many of the most extreme events involve combined AR and TC influences. This is important because it shows that 1) large-scale extreme precipitation has become more common and has changed synoptically and 2) interactions between tropical and non-tropical systems are a key factor for extreme events in this part of the country. Future work might investigate how changes in TC frequency, moisture transport, and jet stream patterns will affect these events in a future climate.

A fuzzing‐based test‐creation approach for evaluating digital TV receivers via transport streams

AbstractDigital TV (DTV) receivers are usually submitted to testing systems for conformity and robustness assessment, and their approval implies correct operation under a given DTV specification protocol. However, many broadcasters inadvertently misconfigure their devices and transmit the wrong information concerning data structures and protocol format. Since most receivers were not designed to operate under such conditions, malfunction and incorrect behaviour may be noticed, often recognized as field problems, thus compromising a given system's operation. Moreover, the way those problems are usually introduced in DTV signals presents some randomness, but with known restrictions given by the underlying transport protocols used in DTV systems, which resembles fuzzing techniques. Indeed, everything may happen since any deviation can incur problems, depending on each specific implementation. This error scenario is addressed here, and a novel receiver robustness evaluation methodology based on non‐compliance tests using grammar‐based guided fuzzing is proposed. In particular, devices are submitted to unforeseen conditions and incorrect configuration. They are created with guided fuzzing based on real problems, protocol structure, and system architecture to provide resources for handling them, thus ensuring correct operation. Experiments using such a fuzzing scheme have shown its efficacy and provided opportunities to improve robustness regarding commercial DTV platforms.

Flood Susceptibility Mapping Using an Analytic Hierarchy Process Model Based on Remote Sensing and GIS Approaches in Akre District, Kurdistan Region, Iraq

In recent decades, floods have been the most common, complex, and destructive natural calamities worldwide. Hence, for inclusive flood risk assessment, creating flood susceptibility mapping to demarcate flood-vulnerable zones is fundamental for decision makers. To assess flood-prone locations in the Akre, Iraqi Kurdistan Region, fundamental for susceptibility mapping was undertaken using geographic information systems, remote sensing, and an analytic hierarchy process model. To assess flood susceptibility, the geographic information systems framework used 15 ideal causative factors for flooding: altitude, slope, distance to streams, flow accumulation, drainage density, rainfall, soil type, lithology, curvature, topographic wetness index (TWI), topographic roughness index stream power index, stream transport index, land use/land cover, and normalized difference vegetation index. The factors contributing to flooding were optimally weighted with respect to the proposed model. The final flood susceptibility map was reclassified into five different classes of susceptibility to flooding: very low (16.64% of the study area); low (19.53%); moderate (38.92%); high (17.83%); and very high (7.08%). The area under curve values for the predicted rate and success rate of the AHP model were 0.956 and 0.971, respectively. Therefore, the results were accurate and reliable. The AHP model is a powerful method for fundamental for susceptibility mapping to mitigate the serious impacts of flooding and assist scholars, local governments and policymakers in future master planning.

Effects of the nanoherbicide made up of atrazine-chitosan on the primary events of photosynthesis

In this research, chitosan and alginate nanocapsules (NCs) have been synthesized and designed to act as carriers (controlled release systems) of atrazine molecules. Atrazine is an herbicide associated with relatively high chronic toxicity, which can also be accumulated as a recalcitrant substance in surface and groundwater. This effect is enhanced by the presence of adjuvants that are part of the commercial formulation. Therefore, the proposal to transport the herbicide in a nontoxic biocompatible nano-encapsulated system is particularly relevant. The nano-capsulated systems with and without the incorporated herbicide (NH, nanoherbicide and empty NCs, respectively) were characterized by scanning electron microscopy images showing an average nanocapsule size of 350 nm and a particle concentration of 4.5 × 1013/ml. The chemical composition of the NCs and NH systems was studied by Fourier Transform Infrared Spectroscopy. The OJIP transient chlorophyll fluorescence was used to evaluate the effects of the NH, commercial atrazine (At) and empty NCs on maize plants as non-target and on chicory as target plants. For the chicory plants treated with the NH and At, a decrease in the activity of the oxygen-generating complex (Fv/F0) and in the maximum quantum yield of PSII (φP0 = TR0/ABS) was observed. In addition, serious alterations in the electronic transport flux (ET0/RC), in the quantum yield for electron transport (φE0 = ET0/ABS) and in the efficiency or probability that an electron moves between plastoquinones QA and QB (ET0/TR0) were obtained for this these plants. The quantum yield of the transport stream electrons to PSI electron acceptors (φR0 = RE0/ABS) and the efficiency with which an exciton will be transferred from PSII to PSI acceptors (ψRE = RE0/TR0) also fell in the plants sprayed with the NH or commercial atrazine with respect to the control plants and those treated with the empty NCs. The photosynthetic parameters obtained for corn plants, treated with both NH and commercial atrazine, showed an inhibition of electron transport in the photosynthetic process at 24 h. These effects were reversed after seven days of treatment, due to the ability of corn plants to detoxify atrazine. Foliar damage was observed in chicory plants treated with atrazine and with NH but not concerning corn plants. Chicory or corn plants treated with the proposed carrier (NCs) showed no foliar effects, which implies that the carrier is harmless to the health of the plants.

In vitro Evaluation of Isoniazid Derivatives as Potential Agents Against Drug-Resistant Tuberculosis.

The upsurge of multidrug-resistant tuberculosis has toughened the challenge to put an end to this epidemic by 2030. In 2020 the number of deaths attributed to tuberculosis increased as compared to 2019 and newly identified multidrug-resistant tuberculosis cases have been stably close to 3%. Such a context stimulated the search for new and more efficient antitubercular compounds, which culminated in the QSAR-oriented design and synthesis of a series of isoniazid derivatives active against Mycobacterium tuberculosis. From these, some prospective isonicotinoyl hydrazones and isonicotinoyl hydrazides are studied in this work. To evaluate if the chemical derivatizations are generating compounds with a good performance concerning several in vitro assays, their cytotoxicity against human liver HepG2 cells was determined and their ability to bind human serum albumin was thoroughly investigated. For the two new derivatives presented in this study, we also determined their lipophilicity and activity against both the wild type and an isoniazid-resistant strain of Mycobacterium tuberculosis carrying the most prevalent mutation on the katG gene, S315T. All compounds were less cytotoxic than many drugs in clinical use with IC50 values after a 72 h challenge always higher than 25 µM. Additionally, all isoniazid derivatives studied exhibited stronger binding to human serum albumin than isoniazid itself, with dissociation constants in the order of 10−4–10−5 M as opposed to 10−3 M, respectively. This suggests that their transport and half-life in the blood stream are likely improved when compared to the parent compound. Furthermore, our results are a strong indication that the N′ = C bond of the hydrazone derivatives of INH tested is essential for their enhanced activity against the mutant strain of M. tuberculosis in comparison to both their reduced counterparts and INH.

Kinetic Landau-fluid closures of non-Maxwellian distributions

New kinetic Landau-fluid closures, based on the cutoff Maxwellian distribution, are derived. A special static case is considered (the frequency ω=0). In the strongly collisional regime, our model reduces to Braginskii's heat flux model, and the transport is local. In the weak collisional regime, our model indicates that the heat flux is non-local and recovers the Hammett–Perkins model while the value of the cutoff velocity approaches to infinity. We compare the thermal transport coefficient χ of Maxwellian, cutoff Maxwellian and super-Gaussian distribution. The results show that the reduction of the high-speed tail particles leads to the corresponding reduction of the thermal transport coefficient χ across the entire range of collisionality, more reduction of the free streaming transport toward the weak collisional regime. In the collisionless limit, χ approaches to zero for the cutoff Maxwellian and the super-Gaussian distribution but remains finite for Maxwellian distribution. χ is complex if the cutoff Maxwellian distribution is asymmetric. The Im(χ) approaches to different convergent values in both collisionless and strongly collisional limit, respectively. It yields an additional streaming heat flux in comparison with the symmetric cutoff Maxwellian distribution. Furthermore, due to the asymmetric distribution, there is a background heat flux q0 though there is no perturbation. The derived Landau-fluid closures are general for fluid moment models, and applicable for the cutoff Maxwellian distribution in an open magnetic field line region, such as the scape-off-layer of Tokamak plasmas, in the thermal quench plasmas during a tokamak disruption, and the super-Gaussian electron distribution function due to inverse bremsstrahlung heating in laser-plasma studies.

Hybrid-based Bayesian algorithm and hydrologic indices for flash flood vulnerability assessment in coastal regions: machine learning, risk prediction, and environmental impact

Natural hazards and severe weather events are a matter of serious threat to humans, economic activities, and the environment. Flash floods are one of the extremely devastating natural events around the world. Consequently, the prediction and precise assessment of flash flood-prone areas are mandatory for any flood mitigation strategy. In this study, a new hybrid approach of machine learning (ML) algorithm and hydrologic indices opted to detect impacted and highly vulnerable areas. The obtained models were trained and validated using a total of 189 locations from Wadi Ghoweiba and surrounding area (case study). Various controlling factors including varied datasets such as stream transport index (STI), stream power index (SPI), lithological units, topographic wetness index (TWI), slope angle, stream density (SD), curvature, and slope aspect (SA) were utilized via hyper-parameter optimization setting to enhance the performance of the proposed model prediction. The hybrid machine learning (HML) model, developed by combining naïve Bayes (NïB) approach and hydrologic indices, was successfully implemented and utilized to investigate flash flood risk, sediment accumulation, and erosion predictions in the studied site. The synthesized new hybrid model demonstrated a model accuracy of 90.8% compared to 87.7% of NïB model, confirming the superior performance of the obtained model. Furthermore, the proposed model can be successfully employed in large-scale prediction applications.

A Comparison Between Machine Learning and Functional Geostatistics Approaches for Data-Driven Analyses of Sediment Transport in a Pre-Alpine Stream

The problem of providing data-driven models for sediment transport in a pre-Alpine stream in Italy is addressed. This study is based on a large set of measurements collected from real pebbles, traced along the stream through radio-frequency identification tags after precipitation events. Two classes of data-driven models based on machine learning and functional geostatistics approaches are proposed and evaluated to predict the probability of movement of single pebbles within the stream. The first class built upon gradient-boosting decision trees allows one to estimate the probability of movement of a pebble based on the pebbles’ geometrical features, river flow rate, location, and subdomain types. The second class is built upon functional kriging, a recent geostatistical technique that allows one to predict a functional profile—that is, the movement probability of a pebble, as a function of the pebbles’ geometrical features or the stream’s flow rate—at unsampled locations in the study area. Although grounded in different perspectives, both models aim to account for two main sources of uncertainty, namely, (1) the complexity of a river’s morphological structure and (2) the highly nonlinear dependence between probability of movement, pebble size and shape, and the stream’s flow rate. The performance of the two methods is extensively compared in terms of classification accuracy. The analyses show that despite the different perspectives, the overall performance is adequate and consistent, which suggests that both approaches can provide modeling frameworks for sediment transport. These data-driven approaches are also compared with physics-based ones that are classically used in the hydrological literature. Finally, the use of the developed models in a bottom-up strategy, which starts with the prediction/classification of a single pebble and then integrates the results into a forecast of the grain-size distribution of mobilized sediments, is discussed.

Field and laboratory investigations on factors affecting the diel variation of arsenic in Huangshui Creek from Shimen Realgar Mine, China: implications for arsenic transport in an alkali stream.

The release of arsenic and related species from mining activities has been investigated widely at both seasonal and diel scales, contributing to the understanding of arsenic cycles, its ultimate fate, and enabling accurate estimates of arsenic flux in specific areas. To enrich the research in this area, a case study was undertaken in Huangshui Creek, Hunan province, China. Here, arsenic is present in the sediment at the Creek entrance to a reservoir and in the widely developed alkali realgar(α-As4S4)-calcite(CaCO3)-dolomite[CaMg(CO3)2] strata (pH 7-11). Water from different levels in the Huangshui Creek, the Creek/reservoir entrance, and the downstream reservoir together with corresponding sediments were collected and analyzed. The local algae were separated and cultured. A diel variation of arsenic (688 ug/L in AM 3:50-1152 ug/L in PM 19:50) was observed in the Creek. The largest difference in arsenic concentration between the upper and lower water body was at the mixed creek/reservoir site (364 ug/L). Laboratory experiments showed that arsenic release from Creek sediment and pristine realgar was 1.3-2.7 times and 2.0-2.3 times at 25 and 37°C, respectively, than low-temperature samples (8°C) over 24h. However, temperature variation is not the only factor controlling arsenic release from Huangshui Creek. Batch experiments show that both sediment and pristine realgar can release arsenic(III). In addition, the presence of bicarbonate promotes arsenic(V) release by 15.2-24.3 times for the sediment and by 1.7-3.4 times for pristine realgar compared to the control, though it restrains arsenic(III) release. High levels of algae have a complex effect on arsenic release; it increases arsenic(V) release by accelerating dissolution of realgar but decreases arsenic(III) release through adsorption. The field observations-variation of bicarbonate (67mg/L in day and 201mg/L in night) and chlorophyll-a (0.06-0.87)-support that both dissolved bicarbonate and algae affect arsenic concentration. These factors establish a circadian rhythm in the Creek, which coupled with arsenic release, ultimately affect the fate of arsenic.

Evaluation of the prediction capability of AHP and F-AHP methods in flood susceptibility mapping of Ernakulam district (India)

Floods are one of the frequent natural hazards occurring in Kerala because of the remarkably high annual rate of rainfall. The objective of this study is to prepare the flood susceptibility maps of Ernakulam district by integrating remote sensing data, GIS, analytical hierarchy process (AHP), and fuzzy-analytical hierarchy process methods. Ernakulam is one of Kerala's most flood-prone districts. The development of this map can help to raise awareness about the risks of flooding. Factors such as slope angle, soil types (texture), land use/land cover, stream density, water ratio index, normalized difference built-up index, topographic wetness index, stream power index, aspect, and sediment transport index have been selected. The area of the final maps is grouped into five flood susceptible zones, ranging from very low to very high. The major reasons for flood occurrence in Ernakulam district are the combined effect of multiple factors such as excess silting, reduction of stream width due to anthropogenic activities, and changes in land cover and land-use pattern, lower slope, higher soil moisture content, lower stream capacity, and poor infiltration capacity of soils. The prepared map was validated using the receiver operating characteristic (ROC) curve method. The area under the ROC curve (AUC) values of 0.75 and 0.81 estimated by the ROC curve method for the AHP and F-AHP methods are considered acceptable and excellent, which confirms the prediction capability of the prepared maps. The very high susceptible zone constitutes around 19% of the district. This map is useful for land-use planners and policymakers to adopt strategies that will reduce the impact of flood hazards and damage in the future.

Effect of exponential heat source on parabolic flow of three different non-Newtonian fluids

This study examined the flow and thermal transfer feature of MHD (magnetohydrodynamic) Casson, Carreau, and Williamson fluid movements over a parabolic extending region with exponential heat generation effect. The mathematical model is transformed into Ordinary Differential Equations (ODEs) by utilizing appropriate similarity variables and resolved using bvp5c Matlab package. The influence of applicable limits on transfer facts is illustrated via plots and tabular values. The current study outcomes reveal the comparisons of flow, thermal profiles, wall friction, and local Nusselt number of these (Casson, Carreau, and Williamson) different non-Newtonian liquids. Casson fluid shows more excellent thermal conductivity when compared to Carreau and Williamson fluids and observed that the drive and thermal gradient of three non-Newtonian fluids are not uniform. Also, the magnetic force tends to condense the stream and thermal transport rate of these three fluids. The rate of thermal transport is amplified by growing the magnitude of Prandtl and exponential parameters.

Influence of land cover, catchment morphometry and rainfall on water quality and material transport of headwaters and low-order streams of a tropical mountainous watershed

Water quality and material transport in small mountainous watersheds respond to diverse factors and may be scale-dependent, when the influence of headwaters and low-order streams on the main channel is considered. Here, the effects of catchment morphometry, rainfall and land cover were evaluated in the physical-chemical parameters of water quality, discharge, suspended sediment and nutrient fluxes of headwaters, low-order streams and the main channel of a tropical mountainous watershed. This watershed is still well-forested with low degree of urbanization, which provided relationships between natural and external drivers of land use changes. The results showed that the water quality of the headwaters generally reacted to urbanization. In contrast, responsive water quality and the transport parameters of the low-order streams were related to the forest cover and the morphological characteristics of the sub-catchments. The downstream transport of water, suspended sediment, and nutrients in the main channel were non-conservative, but presented both retention and intensification depending on the river section, which were not entirely explained by the headwater and low-order stream inflow. The present study highlighted the importance of seasonality of rainfall, catchment morphometry, and land use and land cover changes on the control over the quality of water and material transport of a tropical mountainous watershed.

Nutrient streams in the North Pacific

The nutrient streams in the North Pacific were examined by analyzing the results derived from the inverse calculation of the World Ocean Circulation Experiment (WOCE)-revisit cruise data. The Kuroshio, Alaskan Stream, and Oyashio drive the most intensive nutrient transport within the basin. The upper portion of the nutrient stream (lighter than 26.2 kg/m3) contains mode waters and recirculates within the subtropical gyre, while the intermediate portion (26.2–27.15 kg/m3) relates to North Pacific Intermediate Water (NPIW) and contributes most to nutrient transport in the nutrient stream. The nutrient concentration in the nutrient stream increases in the subtropical gyre along the Kuroshio and Kuroshio Extensions but decreases in the subarctic gyre from the Alaskan Stream to the Oyashio region. This increase or decrease in nutrient concentration from the upstream region to the downstream region mainly results from lateral water exchange, although it also partly depends on biogeochemical processes and vertical diffusion. Specifically, the lateral exchange of the nutrient stream in the subarctic gyre with water from lower latitudes decreases the nitrate concentration of the Alaskan Stream and that with water from the Okhotsk Sea decreases the nitrate concentration of the Oyashio. For vertical nitrate transport, our estimation shows that the ventilation processes of subduction and induction are comparable to the sum of vertical advection and diffusion. This implies that nutrient transport related to the ventilation of the North Pacific is in a dynamic balance on an annual cycle and should be quantified in future work.

Roles of auxin in the inhibition of shoot branching in 'Dugan' fir.

Shoot branching substantially impacts vegetative and reproductive growth as well as wood characteristics in perennial woody species by shaping the shoot system architecture. Although plant hormones have been shown to play a fundamental role in shoot branching in annual species, their corresponding actions in perennial woody plants are largely unknown, in part due to the lack of branching mutants. Here, we demonstrated the role of plant hormones in bud dormancy transition toward activation and outgrowth in woody plants by comparing the physiological and molecular changes in the apical shoot stems of 'Yangkou' 020 fir and 'Dugan' fir, two Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.) clones with normal and completely abolished branching phenotypes, respectively. Our studies showed that the defect in bud outgrowth was the cause of failed shoot branching in 'Dugan' fir whereas apically derived signals acted as triggers of this ectopic bud activity. Further studies indicated that auxin played a key role in inhibiting bud outgrowth in 'Dugan' fir. During bud dormancy release, the differential auxin resistant 1/Like AUX1 (AUX1/LAX) and PIN-formed (PIN) activity resulted in an ectopic auxin/indole-3-acetic acid (IAA) accumulation in the apical shoot stem of 'Dugan' fir, which could inhibit the cell cycle in the axillary meristem by decreasing cytokinin (CK) biosynthesis but increasing abscisic acid (ABA) production and response through the signaling pathway. In contrast, during bud activation and outgrowth, the striking increase in auxin biosynthesis and PIN activity in the shoot tip of 'Dugan' fir may trigger the correlative inhibition of axillary buds by modulating the polar auxin transport stream (PATS) and connective auxin transport (CAT) in shoots, and by influencing the biosynthesis of secondary messengers, including CK, gibberellin (GA) and ABA, thereby inducing the paradormancy of axillary buds in 'Dugan' fir by apical dominance under favorable conditions. The findings of this study provide important insights into the roles of plant hormones in bud outgrowth control in perennial woody plants.

Long-term assessment of floodplain reconnection as a stream restoration approach for managing nitrogen in ground and surface waters

Stream restoration is a popular approach for managing nitrogen (N) in degraded, flashy urban streams. Here, we investigated the long-term effects of stream restoration involving floodplain reconnection on riparian and in-stream N transport and transformation in an urban stream in the Chesapeake Bay watershed. We examined relationships between hydrology, chemistry, and biology using a Before/After-Control/Impact (BACI) study design to determine how hydrologic flashiness, nitrate (NO3−) concentrations (mg/L), and N flux, both NO3− and total N (kg/yr), changed after the restoration and floodplain hydrologic reconnection to its stream channel. We examined two independent surface water and groundwater data sets (EPA and USGS) collected from 2002–2012 at our study sites in the Minebank Run watershed. Restoration was completed during 2004 and 2005. Afterward, the monthly hydrologic flashiness index, based on mean monthly discharge, decreased over time from 2002 and 2008. However, from 2008–2012 hydrologic flashiness returned to pre-restoration levels. Based on the EPA data set, NO3− concentration in groundwater and surface water was significantly less after restoration while the control site showed no change. DOC and NO3− were negatively related before and after restoration suggesting C limitation of N transformations. Long-term trends in surface water NO3− concentrations based on USGS surface water data showed downward trends after restoration at both the restored and control sites, whereas specific conductance showed no trend. Comparisons of NO3− concentrations with Cl− concentrations and specific conductance in both ground and surface waters suggested that NO3− reduction after restoration was not due to dilution or load reductions from the watershed. Modeled NO3− flux decreased post restoration over time but the rate of decrease was reduced likely due to failure of restoration features that facilitated N transformations. Groundwater NO3− concentrations varied among stream features suggesting that some engineered features may be functionally better at creating optimal conditions for N retention. However, some engineered features eroded and failed post restoration thereby reducing efficacy of the stream restoration to reduce flashiness and NO3− flux. N management via stream restoration will be most effective where flashiness can be reduced and DOC made available for denitrifiers. Stream restoration may be an important component of holistic watershed management including stormwater management and nutrient source control if stream restoration and floodplain reconnection can be done in a manner to resist the erosive effects of large storm events that can degrade streams to pre-restoration conditions. Long-term evolution of water quality functions in response to degradation of restored stream channels and floodplains from urban stressors and storms over time warrants further study, however.