Flood Conditions Research Articles

Abiotic Stress Responses in Woody Plants: Morphological, Physiological, and Anatomical Features

Abiotic stressors may have intricate and varied impacts on the growth and development of forest trees. This article provides a comprehensive summary of the effects of abiotic stressors, such as flood, drought, severe temperature, salt, heavy metal, combination stresses, and microplastics, on the morphological, physiological, and anatomical features of woody plants. The focus is particularly on evaluating these effects from the viewpoint of the xylem. During abiotic stress, the ability of xylem to transport water declines, which is linked to the control of leaf stomata and the suppression of aquaporin (AQP) function. Concurrently, woody plants maintain control over the dimensions and structure of their roots and leaves in order to achieve a harmonious equilibrium between water intake and evaporation. The anatomical characteristics are modified as well, including increased density of leaf stomata, smaller conduits, and thicker cell walls. Furthermore, various types of stressors elicit distinct responses in plants. For instance, flooding leads to the development of adventitious roots and aeration tissues, while forest fires cause irreparable damage to the xylem. Low temperatures result in tissue freezing, salt stress hinders ion absorption, and exposure to heavy metals induces biological toxicity. Woody plants' growth may be periodically enhanced in conditions of drought, floods, and exposure to heavy metals. The impact of combined stress on the physiological, morphological, and anatomical characteristics of woody plants is not only cumulative. The underlying mechanism behind this phenomenon requires additional investigation, particularly in natural or near-natural environments.

ANALISIS PENGETAHUAN MITIGASI BANJIR PADA MASYARAKAT KABUPATEN BANJAR DENGAN PENDEKATAN METODE REGRESI LOGISTIK BINER

The largest flood condition in South Kalimantan Province occurred in 2021. The worst flooded area is Banjar Regency with 27,249 fatalities. Floods also affected the agriculture and fisheries sectors, causing agricultural land productivity to decrease to 87,598 tons from 2021 to 2020. A total of 1,838 aquaculture businesses suffered losses of up to 70 billion rupiah. The causes of flooding do not only come from natural factors but can come from other factors such as a lack of knowledge of flood mitigation, resulting in huge losses for the community. Previous research states that the factors that influence flood disaster mitigation are the level of education and income. This study aims to determine the factors that influence flood mitigation knowledge in Banjar Regency communities using the binary logistic regression method. The results of the study provide differences from previous studies, namely the environmental factor with category 1, the implementation of environmental management by the community affects flood mitigation knowledge with a p value (0.027) < α (0.05) and a value of W (2.2198) > Z_table (1.960). The odds ratio value shows that the probability of the Banjar Regency community having flood mitigation knowledge is 2.79 times greater than other variable categories. The model explains an influence of 31.6% with an AIC value of 125. The respondents flood mitigation knowledge in managing the environment includes all types and stages of flood disaster mitigation related to local wisdom in the respondents location, namely several terms such as "Apar-Apar, Jukung Terpal, Galangan, Kelambu Kolam". There are still some things that need to be maximized for flood mitigation knowledge, namely the formation of disaster resilient villages in Martapura City, East and West Sub-districts. Dissemination of information on climate-smart agriculture training to farmers. Realization of temporary waste bin facilities in Banjar Regency.

Evolutionary model for glacial lake-outburst fans at the ice-sheet front: Development of meltwater outlets and origins of bedforms

Large-scale landforms originated from jökulhlaups or glacial lake-outburst floods (GLOFs), and their small-scale components help in recognising the sedimentary environment of the flood. The GLOF fans that developed along the Pleistocene ice-sheet margin have not been investigated in detail, and north-eastern Poland, with its Megaflood Landform System and Bachanowo and Szeszupka fans, seems ideal for landform and sedimentary studies. This paper provides (1) an important opportunity to recognise the origins of glacier lake-outburst flood outlets and their evolution during two GLOFs and (2) a model of the origin of ice-marginal fans considering changes in sedimentary environment reflecting flood stages. During the first GLOF (GLOF1), the rising stage of meltwater burst triggered the formation of a supraglacial outlet and the development of the Szeszupka outburst fan. During the pulsed peak discharge, subglacial multi-channelised meltwater outburst caused the formation of the Bachanowo Gate, which was finally transformed at the flood waning stage. Such processes were associated with the widening of the floodwater subglacial routeway, when floodwater outlets rapidly spread across the glacier snout. In contrast, GLOF2 was responsible only for the Szeszupka fan erosion and development of outburst terraces. The small-scale bedforms continuum, recognised on the outburst fan surface, is associated with the development of streamlined erosional residuals, scours and their trains during the rising stage and peak discharge, while the waning stage and very end of flood conditions were favourable to the formation of pendant bars, distributive channels with erosional bars and chute bars, regardless of the feeding systems of the outburst fans.The fan deposits were OSL-dated and revealed either, likely, overly old ages or an age of 13.2 ± 0.9 ka. The latter age would imply the ‘normal’ meltwater outflow having a correlation with the events in the region. Nevertheless, this age might be considered a minimum age of the flood.

Spatial assessment of flood vulnerability and waterlogging extent in agricultural lands using RS-GIS and AHP technique-a case study of Patan district Gujarat, India.

Assessing and mapping flood risks are fundamental tools that significantly contribute to the enhancement of flood management strategies. Identifying areas that are susceptible to floods and devising strategies to reduce the risk of waterlogging is of utmost importance. In the present study, an integrated approach, combining advanced remote sensing technologies, Geographic Information Systems (GIS), and analytic hierarchy process (AHP), was adopted in the Patan district of Gujarat, India, with a coastline spanning over 1600km, to evaluate the numerous variables that contribute to the risk of flooding and waterlogging. After evaluating the flood conditioning factors and their respective weights using the analytic hierarchy process (AHP), the results were processed in GIS to accurately delineate areas that are prone to flooding. The results highlighted exceptional precision in identifying vulnerable areas, allowing for a thorough evaluation of the impact severity. The integrated approach yields valuable insights for multi-criteria assessments. The findings indicate that a significant portion of the district's land, precisely 8.94%, was susceptible to very high- risk of flooding, while 27.76% were classified as high-risk areas. Notably, 35.17% of the region was identified as having a moderate level of risk. Additionally, 20.96% and 7.15% were categorized as low-risk and very low-risk areas, respectively. Overall, the study highlights the need for proactive measures to mitigate the impact of floods on vulnerable communities. The research findings were verified by conducting ground truth and visual assessments using microwave satellite imagery (Sentinel-1). The aim of this validation was to test the accuracy of the study in identifying waterlogged agricultural areas and their extent based on AHP analysis. The ground verification and analysis of satellite images confirmed that the model accurately identified approximately 74% of the area categorized under high and very high flood vulnerability to be waterlogged and flooded. This research can provide valuable assistance to policymakers and authorities responsible for flood management by gathering necessary information about floods, including their intensity and the regions that are most susceptible to their impact. Additionally, it is crucial to implement corrective measures to improve soil drainage in vulnerable areas during heavy rainfall events. Prioritizing the adoption of sustainable agricultural practices and improving land use are also crucial for environmental conservation.

Discrete element analysis on impact failure mechanism of “Zhengzhou 7.20” catastrophic flood for coal gangue railway subgrade

Limited research has been conducted on the failure mechanism of coal gangue railway subgrade structures during catastrophic flood disasters, including the impact of varying flood impact heights and load sizes. This study investigates the process and mechanism of coal gangue railway subgrade failure in the coal mining subsidence area, in conjunction with the “7.20” catastrophic flood in Zhengzhou. First, various factors such as impact forms, impact height, flow velocity, water depth, and wave height are considered, and a wave-water flow coupling calculation method is proposed to determine the catastrophic flood load acting on inclined slopes. The maximum impact load calculated is then applied to simulate the impact process of the catastrophic flood using Particle Flow Code 2D. As the flood-related parameters increase, the maximum impact load on the subgrade slope also increases, leading to the breakdown of the subgrade and causing fatal damage. Finally, the failure process of the coal gangue railway subgrade under the impact and scour of a catastrophic flood is divided into three stages: erosion weakening, potential failure surface formation, and overall failure. The main failure mechanisms of each stage are revealed. These research result findings offer valuable insights for the design of railway subgrade reinforcement under catastrophic flood conditions.

General hospital preparedness in facing flood disasters

Hospitals had a very important function in disaster management, especially in providing health services to reduce the suffering of disaster victims in the form of deceases and injuries. Hospital preparedness in facing disasters was contained in the Hospital Disaster Plan which was prepared based on the Safe Hospital Framework [1], and the Hospital Safety Index[2]. The purpose of this study was to analyze the preparedness of Aceh Tamiang General Hospital in facing flood disasters from 4 (four) aspects or evaluation modules namely, Hazard Affecting, Structural Safety, Non-Structural Safety, Emergency and Disaster Management, specifically analyzing the aspect of “Emergency and Disaster Management” according to the research focus namely, hospital policies, human resources preparedness and hospital infrastructure readiness in facing flood disasters. The research methodology was qualitative with a phenomenological design by 7 (seven) informants. The results of the study showed that the policies of the hospital leadership had been good, with the existence of a Leadership Decree concerning the Formation of a Hospital Disaster Management Team, since 2019 ago. However, there were still hospital personnel who did not know about the organizational structures, goals and functions as team members. Many hospital health workers could not go to work because their homes and access to the hospital were flooded. Besides that, hospital infrastructure, especially motorized vehicles such as ambulances and other operational vehicles, could not operate due to flood conditions that reached up to 1 meter. Therefore it was suggested that the socialization of the Disaster Management Team and Disaster Management Simulation should be carried out periodically, for example, twice a year. It should be suggested that the hospital proposed procuring an ambulance with certain specifications and a rescue boat, so that it could break through the floods that occur almost every year.

Flooding Length Mediates Fencing and Grazing Effects on Soil Respiration in Meadow Steppe.

Grassland management affects soil respiration (Rs, consists of heterotrophic respiration and autotrophic respiration) through soil micro-ecological processes, such as hydrothermal, plant root, organic carbon decomposition and microbial activity. Flooding, an irregular phenomenon in grasslands, may strongly regulate the response of soil respiration and its components to grassland management, but the regulatory mechanism remains unclear. We conducted a 3-year experiment by grassland management (fencing and grazing) and flooding conditions (no flooding (NF), short-term flooding (STF) and long-term flooding (LTF)) to study their effects on Rs and its components in a meadow steppe in the Hui River basin of Hulunbuir. We found differences in the patterns of Rs and its components under grassland management and flooding conditions. In 2021-2023, the temporal trends of Rs, heterotrophic respiration (Rh) and autotrophic respiration (Ra) were generally consistent, with peaks occurring on days 190-220, and the peaks of grazing were higher than that of fencing. In NF, Rs of grazed grassland was significantly higher than that of fenced grassland in 2021-2022 (p < 0.05). In STF and LTF, there was no significant difference in Rs between fenced and grazed grassland (p > 0.05). The dependence of Rs on soil temperature (ST) decreased with increasing flooding duration, and the dependence of Rs on ST of grazed grassland was higher than fenced grassland under NF and STF, but there was no difference between fenced grassland and grazed grassland under LTF. In addition, Rh was more sensitive to ST than Ra. This may be due to the different pathways of ST effects on Rs under grazing in different flooding conditions. Our study indicates that the effect of flooding on Rs is the key to the rational use of grassland under future climate change. To reduce regional carbon emissions, we recommend grazing on flooding grassland and fencing on no-flooding grassland.

A novel machine learning tool for current and future flood susceptibility mapping by integrating remote sensing and geographic information systems

Flood mapping is essential for managing and mitigating the risks associated with flood events. This study integrates weighted overlay analysis and analytical network process to create a flood susceptibility map. Twelve factors were selected to assess flood risk in the region, and an analytical network process was used to derive weights of factors. Weighted overlay analysis was then used to apply weights to the flood conditioning factors to prepare the flood susceptibility map. The most prominent historical flood extent was derived by using Landsat 8, Sentinel-2 and Sentinel-1 satellite imageries, spectral indices and decision tree model to generate a flood inventory map. The flood susceptibility map was assessed for accuracy using the flood inventory map, achieving an overall accuracy rate of 88.3 %. The primary factors affecting flood risk were elevation, slope, and distance from the stream, with high-risk areas mainly located downstream. To develop the flood risk assessment model, the essential factors were classified into four main categories: topographical, environmental, hydrological, and anthropological. All possible input combinations were checked using the outlier robust extreme learning machine for one to twelve input variables, and the best model was selected using the outlier robust extreme learning machine with the input combination of five variables (i.e., normalizes difference vegetation index, geology, precipitation, elevation, and slope). Based on the Sixth Intergovernmental Panel on climate change report, the developed outlier robust extreme learning machine was used to project potential flood areas in the next 78 years. Based on the different scenarios, the results indicated that 10.93 %, 8.55 %, 8.09 %, 11.99 %, and 16.28 % of all areas are projected to be highly and very highly flood susceptible. The tools and methods outlined in this study can assist decision-makers in preparing for and responding to floods. Moreover, the method developed in this study can be implemented in watersheds and urban areas and help manage flood risk in urban drainage systems.

Plant Physiological Performances, Plant Growth, Grain Yield and Methane Emission of Rice (Oryza Sativa L.) in Response to Water Management as Adaptation Strategy for Climate Change

Continuously flooded rice systems are a major contributor to the greenhouse gases (GHG) emissions in the agriculture sector in Malaysia. Intermittent irrigation has been recommended to replace conventional rice water management to save water and reduce GHG emissions without compromising rice yields. This study was conducted in two growing seasons at Malaysia’s largest rice granary area to determine the effectiveness of different water management practices on conserving water, mitigating GHG and maintaining rice grain yields. Three water management treatments were continuous flooding (CF), saturated and wet conditions from transplanting to heading and flooding until maturity (S-F) and continuous saturated and wet conditions (CS). The results showed that S-F and CS reduced water inputs between 15.0-16.8% and 32.0-34.0% as compared to CF, respectively. Water-saving treatments mostly did not significantly affect the plant's physiological performance, plant growth parameters, growth rate, grain yield and yield parameters. The results indicated that soil saturated and wet conditions provided adequate soil moisture content for the plant’s requirement similar to flooding conditions. Maintaining soil at saturated and wet conditions during the vegetative stage reduced 24.18-39.76% of methane emissions. However, maintaining soil at saturated and wet conditions throughout the growing season reduced 34.52-55.08% of methane emissions. In conclusion, intermittent irrigation could be an effective adaptation technique for simultaneously saving water and mitigating GHG while maintaining high rice grain yields in rice cultivation systems.

Evaluation of the potentials of rice varieties and water management practices for reducing human health risks associated with polluted river water irrigated rice in Bangladesh

The consumption of arsenic and trace-metal-contaminated rice is a human health concern worldwide, particularly in Bangladesh. In this study, the effects of rice varieties and water management practices on the concentrations of arsenic and trace metals in rice grains were investigated to reduce human health risks related to rice consumption. In addition, the performance of risk reduction using the optimum combination of rice variety and water management practices was quantitatively assessed using Monte Carlo simulation, in which non-carcinogenic and carcinogenic risk distributions under the status quo and the optimum combination were compared. The experimental results revealed that Dular and BRRI dhan45 (rice varieties) cultivated under alternate wetting and drying (AWD) and continuous flooding (CF) conditions showed the lowest hazard quotient (HQ) values for copper, cadmium, and arsenic and the lowest target cancer risk (TR) for arsenic. In Dular and BRRI dhan45 (AWD and CF) varieties, the proportion of the population for which HQs exceeded 1.0 (the reference value) tended to decrease (except for arsenic), compared with populations for which the rice varieties and water management practices were not specified. These results suggest that the use of optimum combinations of rice varieties and water management practices could reduce non-carcinogenic and carcinogenic risks associated with arsenic and trace metals uptake via rice grain consumption by the Bangladeshi people.

Assessment of the Impact of Spatial Variability on Streamflow Predictions Using High-Resolution Modeling and Parameter Estimation: Case Study of Geumho River Catchment, South Korea

In this study, we analyzed the impact of model spatial resolution on streamflow predictions, focusing on high-resolution scenarios (&lt;1 km) and flooding conditions at catchment scale. Simulation experiments were implemented for the Geumho River catchment in South Korea using Weather Research and the Forecasting Hydrological Modeling System (WRF-Hydro) with spatial resolutions of 100 m, 250 m, and 500 m. For the estimation of parameters, an automatic calibration tool based on the Model-Independent Parameter Estimation and Uncertainty Analysis (PEST) method was utilized. We assessed the hydrological predictions across different spatial resolutions considering calibrated parameters, calibration runtime, and accuracy of streamflow before and after calibration. For both Rainfall Events 1 and 2, significant improvements were observed after event-specific calibration in all resolutions. Particularly for 250 m resolution, NSE values of 0.8 or higher were demonstrated at lower gauging locations. Also, at a 250 m resolution, the changes in the calibrated parameter values (REFKDT) were minimized between Rainfall Events 1 and 2, implicating more effective calibration compared to the other resolutions. At resolutions of 100 m and 500 m, the optimal parameter values for the two events were distinctively different while more computational resources were required for calibration in Event 2 with drier antecedent conditions.

Effects of urban drainage inlet layout on surface flood dynamics and discharge

Drainage inlets, the primary conduits for surface floodwater into underground facilities, significantly influence the performance of a drainage system. This study employs a two-dimensional hydrodynamic model to investigate how drainage inlet distribution affects urban flood dynamics and drainage flow discharge. We first validate the model with dataset obtained in a dedicated experiment observing urban surface and drainage flows. We identified two common layouts of drainage inlets, namely straight-line distribution (SLD) and surround type distribution (STD), and based on the two layouts, we simulated detailed surface flood dynamics and drainage discharge under various urban flood conditions and inlet spacing scenarios. The results indicate that SLD exhibits higher drainage capacity in shorter time and greater total drainage volume under urban peripheral flood condition, while STD consistently outperforms in draining urban surface flooding induced by intense rainfall. It is also found that inlet spacing plays a crucial role in affecting drainage efficiency. To be specific, both layouts with medium spacing (l0 = 0.53 for SLD and 0.93 for STD) near flood-prone areas perform better when a sudden-onset peripheral flooding occurred; however, in the case of rainfall-induced flooding, maximizing inlet spacing and strategically distributing them across urban streets proves to be a more effective strategy for draining floodwater. Individual inlets near the ends of SLD and inlets at far-corners of STD shoulder higher drainage loads. This study provides valuable insights for optimizing inlet layout strategies under various urban flood conditions and improving floodwater collection.

Non-perennial rivers and streams in extreme hydrological conditions—comparing the effectiveness of amplicon sequencing and digital microscopy for diatom biodiversity appraisal

IntroductionNon-perennial rivers and streams are increasingly present, in part because of climate change, even in the temperate climate. However, how the loss of connectivity and complete drying affect microphytobenthos in general and diatom communities in particular has gone mostly unstudied. MethodsWith this paper, we aim to close this gap, identifying diatom biodiversity through manual digital microscopy and rbcL amplicon sequencing, to observe a) which method is better suited to it and b) how the ecotone flow-pool-dry affects diatom diversity under duress. Three karstic, non-perennial rivers and streams with a gradient from natural to anthropogenically disturbed were sampled under flooding conditions and after a long and intense drought in 2022.ResultsOur results show that digital microscopy shows a higher diversity and species richness than amplicon sequencing. We posit that this might be due to a reduced pool of subaerophile taxa having been sequenced and being part of the reference database. Furthermore, the effect of drying only resulted in a reduction in diversity after this drought, although the biofilm was still alive under these conditions. DiscussionTo use amplicon sequencing for non-perennial river diatom diversity monitoring, the reference databases will have to be adapted to such systems, as most rivers may be subjected to drying regularly in the future.

Dimensionless argument: a narrow grain size range near 2 mm plays a special role in river sediment transport and morphodynamics

Abstract. The grain size 2 mm is the conventional border between sand and gravel. This size is used extensively, and generally without much physical justification, to discriminate between such features as sedimentary deposit type (clast-supported versus matrix-supported), river type (gravel bed versus sand bed), and sediment transport relation (gravel versus sand). Here we inquire as to whether this 2 mm boundary is simply a social construct upon which the research community has decided to agree or whether there is some underlying physics. We use dimensionless arguments to show the following for typical conditions on Earth, i.e., natural clasts (e.g., granitic or limestone) in 20 ∘C water. As grain size ranges from 1 to 5 mm (a narrow band including 2 mm), sediment suspension becomes vanishingly small at normal flood conditions in alluvial rivers. We refer to this range as pea gravel. We further show that bedload movement of a clast in the pea gravel range with, for example, a size of 4 mm moving over a bed of 0.4 mm particles has an enhanced relative mobility compared to a clast with a size of 40 mm moving over a bed of the same 4 mm particles. With this in mind, we use 2 mm here as shorthand for the narrow pea gravel range of 1–5 mm over which transport behavior is distinct from both coarser and finer material. The use of viscosity allows the delineation of a generalized dimensionless bed grain size discriminator between “sand-like” and “gravel-like” rivers. The discriminator is applicable to sediment transport on Titan (ice clasts in flowing methane/ethane liquid at reduced gravity) and Mars (mafic clasts in flowing water at reduced gravity), as well as Earth.

The peculiarities of cell elongation growth of cereal coleoptiles under normal and flooding conditions

The review examines modern knowledge on the mechanisms of the early stages of plant cell elongation growth. Coleoptiles are used as a model object representing juvenile organs of cereal seedlings. Elongation growth is considered to be a protective morphophysiological stage of seedling development during hypogeal germination. The molecular mechanisms of elongation growth include: changes in the properties of the cell wall, activation of proton pumps, as well as aquaporins of plasma membrane and tonoplast. Particular attention is paid to the hormonal system of regulation, including auxin and ethylene. Coleoptiles of rice, a semi-aquatic plant tolerant to oxygen deficiency, demonstrate that the mechanisms of elongation growth are changing intensively under submergence, but they completely ensure cell growth. There is also a redistribution of importance and abundance between phytohormones. The data presented in the review indicate the necessity to continue investigations on the mechanisms of elongation growth under normal and stress conditions.

Fluvial Response to Environmental Change in Sub-Tropical Australia over the Past 220 Ka

This paper uses a 30 m record of valley alluviation in the Lockyer Creek, a major tributary of the mid-Brisbane River in Southeast Queensland, to document the timing and nature of Quaternary fluvial response. A combination of radiocarbon and optically stimulated luminescence dating reveals a sequence of major cut and fill episodes. The earliest aggradation phase is represented by a basal gravel unit, dating to ~220 ka (marine isotope sub-stage 7d), and although little evidence supports higher fluvial discharges during MIS 5, a MIS 3 fluvial episode characterised by incision and aggradation dates to ~60 ka. A penultimate phase of incision to a depth of 30 m prior to ~14 ka saw the lower Lockyer occupy its current position within the valley floor. The Lockyer Creek shows evidence of only minor fluvial activity during MIS 2, suggesting a drier LGM climate. The appearance of alternating fine- and coarse-grained units at about 2 ka is notable and may represent higher-energy flood conditions associated with a strengthening of El Niño Southern Oscillation activity as observed in the flood of 2011. The aggradation rate for this Holocene floodplain unit is ~11 times higher than the long-term rate.

Microbiome structure variation and soybean's defense responses during flooding stress and elevated CO2.

With current trends in global climate change, both flooding episodes and higher levels of CO2 have been key factors to impact plant growth and stress tolerance. Very little is known about how both factors can influence the microbiome diversity and function, especially in tolerant soybean cultivars. This work aims to (i) elucidate the impact of flooding stress and increased levels of CO2 on the plant defenses and (ii) understand the microbiome diversity during flooding stress and elevated CO2 (eCO2). We used next-generation sequencing and bioinformatic methods to show the impact of natural flooding and eCO2 on the microbiome architecture of soybean plants' below- (soil) and above-ground organs (root and shoot). We used high throughput rhizospheric extra-cellular enzymes and molecular analysis of plant defense-related genes to understand microbial diversity in plant responses during eCO2 and flooding. Results revealed that bacterial and fungal diversity was substantially higher in combined flooding and eCO2 treatments than in non-flooding control. Microbial diversity was soil>root>shoot in response to flooding and eCO2. We found that sole treatment of eCO2 and flooding had significant abundances of Chitinophaga, Clostridium, and Bacillus. Whereas the combination of flooding and eCO2 conditions showed a significant abundance of Trichoderma and Gibberella. Rhizospheric extra-cellular enzyme activities were significantly higher in eCO2 than flooding or its combination with eCO2. Plant defense responses were significantly regulated by the oxidative stress enzyme activities and gene expression of Elongation factor 1 and Alcohol dehydrogenase 2 in floodings and eCO2 treatments in soybean plant root or shoot parts. This work suggests that climatic-induced changes in eCO2 and submergence can reshape microbiome structure and host defenses, essential in plant breeding and developing stress-tolerant crops. This work can help in identifying core-microbiome species that are unique to flooding stress environments and increasing eCO2.

Methane emissions and microbial communities under differing flooding conditions and seasons in littoral wetlands of urban lake

Wetlands are the largest natural sources of methane (CH4) emissions worldwide. Littoral wetlands of urban lakes represent an ecotone between aquatic and terrestrial ecosystems and are strongly influenced by water levels, environmental conditions, and anthropogenic activities. Despite these littoral zones being potential “hotspots” of CH4 emissions, the status of CH4 emissions therein and the role of physicochemical properties and microbial communities regulating these emissions remain unclear. This study compared the CH4 fluxes, physicochemical properties, and CH4-cycling microbial communities (methanogens and methanotrophs) of three zones (a non-flooded supralittoral zone, a semi-flooded eulittoral zone, and a flooded infralittoral zone) in the littoral wetlands of Lake Pipa, Jiangsu Province, China, for two seasons (summer and winter). The eulittoral zone was a CH4 source (median: 11.49 and 0.02 mg m−2 h−1 in summer and winter, respectively), whereas the supralittoral zone acted as a CH4 sink (median: −0.78 and −0.09 mg m−2 h−1 in summer and winter, respectively). The infralittoral zone shifted from CH4 sink to source between the summer (median: −10.65 mg m−2 h−1) and winter (median: 0.11 mg m−2 h−1). The analysis of the functional genes of methanogenesis (mcrA) and methanotrophy (pmoA) and path analysis showed that CH4 fluxes were strongly regulated by biotic factors (abundance of the mcrA gene and alpha diversity of CH4-cycling microbial communities) and abiotic factors (ammonia nitrogen, moisture, and soil organic carbon). In particular, biotic factors had a major influence on the variation in the CH4 flux, whereas abiotic factors had a minor influence. Our findings provide novel insights into the spatial and seasonal variations in CH4-cycling microbial communities and identify the key factors influencing CH4 fluxes in littoral wetlands. These results are important for managing nutrient inputs and regulating the hydrological regimes of urban lakes.

Tolerance to drought and flooding events provides a competitive advantage for an invasive over a native plant species

Abstract Changes in precipitation patterns are one of the most pervasive components of climate change. It has been suggested that the increased frequency of extreme drought and flooding events could affect the outcome of competition between native and invasive plants. However, empirical evidence for this prediction remains scarce. We combined controlled experiments and field observations in a freshwater floodplain to assess how drought and flooding events affect growth and biomass production of a native and an invasive plant species, grown in monoculture and mixed culture. We used the native Panicum dichotomiflorum and the invasive Urochloa mutica, which are two common grasses that frequently grow in natural floodplains of the Neotropics. The experimental and observational data showed that biomass production, growth and relative dominance of the native species were higher under more stable water levels. By contrast, the invasive species had higher biomass production, growth and relative dominance under extreme drought and flooding conditions. Thus, extremes in precipitation can alter the relative dominance of the two species in favour of the invader. Our study provides comprehensive evidence that water‐level oscillations may negatively impact the performance of the native species, whereas they did not alter the biomass production and growth of the invasive species. Under stable conditions, faster growth of the native species may hinder successful establishment of the invasive species. However, under extreme drought and flooding events, the invader could be favoured. Although our findings are based on the outcome of the interaction between only one native and one invasive plant species, our results suggest that biotic resistance might be higher under stable water conditions.

Numerical simulation of the Oncomelania snails transport attached to floating objects under different wind conditions

The long-distance migration of Oncomelania snails mainly occurs by attaching to floating objects during floods. However, the processes, characteristics and effects of migration are not fully understood. Here, a motion equation for floating objects with attached Oncomelania snails was constructed using the Lagrangian method. The equation can be numerically solved to simulate the movement of floating objects after parameter calibration. Then, the calibrated parameters were used to simulate the migration of Oncomelania snails in the lower Jingjiang River, where they had spread over a large area. The effects of flood conditions on the migration and spread of Oncomelania snails have been studied to a certain extent, but the impact of wind conditions on snail migration has rarely been reported. Therefore, based on the distribution of Oncomelania snails in China, the difficulties and key areas for the control of schistosomiasis and Oncomelania snails, and the morphological characteristics of the river reach, the Lower Jingjiang River section was selected as a practical application case. A theoretical model of the migration and spread of Oncomelania snails was established, and the characteristics of the Oncomelania snail migration were simulated and analyzed based on flood and distribution patterns under different wind conditions. The results indicate that wind conditions have little influence on the longitudinal spreading of Oncomelania snails but have a relatively large influence on the lateral spreading of snails. Compared with calm wind conditions, both northeasterly and southerly wind conditions can lead to longer longitudinal migration distances of snails, thereby increasing the risk of snail spreading and schistosomiasis transmission.