Floodplain Landscapes Research Articles

Hemeroby and naturalness differ in spatial patterns: the case of aquatic macrophytes

ABSTRACT Hemeroby and naturalness are indicators of ecosystem health and can be used to assess the state of aquatic macrophyte communities in floodplain landscapes under anthropogenic pressure. This article verifies the hypothesis that hemeroby and naturalness are distinguished by specific spatial patterns. Hemeroby is sensitive to changes in the level of anthropogenic pressure under conditions of a high level of ecosystem transformation. Naturalness is capable of responding to environmental disturbances of both natural and anthropogenic origin and is sensitive to changes in the state of ecosystems as they approach natural conditions. The variability of the naturalness of aquatic macrophyte communities does not depend on the direction of spatial patterns. Accounting for the directionality of spatial patterns provides a better explanation for the small-scale component of community hemeroby variability.

Behavior of <sup>137</sup>Cs in the soil-plant system in the floodplain landscapes of the Sozh River basin

Studies were carried out in the most affected by the Chernobyl accident part of the Bryansk region, in the ecosystems of floodplains of the Iput, Besed and Unecha rivers, in zones with different 137Cs pollution density. The purpose of the work is to study the peculiarities of the vertical distribution of 137Cs in the soil–plant system of the floodplain landscape long after the Chernobyl accident. As a result of studies, it was revealed that the vertical distribution of 137Cs, in the 0–20 cm layer, is determined by the position on the relief and the genesis of the soils of floodplain subsystems. The distribution character can be uniform, decreasing with depth, or with accumulation in certain layers. In the floodplain ecosystem, the concentration of 137Cs in the 0–20 cm layer increases from the river channel to the terrace above floodplain subsystems. Currently, the use of the territory of the west of the Bryansk region with a 137Cs pollution density above 555 kBq/m2 in feed production is strictly limited. The coefficient of 137Cs transition from soil to plants decreases from the central part to the near-channel one and to terrace above floodplain.

Phytodiversity of the Inhulets River floodplain flora (Shyrokivskyi district)

The phytodiversity of the floodplain of the Inhulets River in the Shyrokivsky district was studied and the bioecological characteristics of flora species were compiled based on the results of systematic, biological and ecological analyzes. It was found that the flora of the floodplain landscape is represented by 329 species belonging to 69 families. The spectrum of the studied flora is dominated by perennials among biomorphs, heliomorphs – heliophytes, trophomorphs – mesotrophs, hygromorphs – mesophytes, and cenomorphs – ruderals and pratants. In the studied flora, 20 species from the Red List of Dnipro region were recorded, three of which are included in the Red Book of Ukraine: Crocus reticulatus Stev. ex Adam., Ornithogalum bouscheanum (Kunth) Aschers and Tulipa quercetorum Klokov et Zoz. Rare species included in the Red Data Book of Dnipro region were recorded in the woody and shrubby vegetation of the studied area: Viburnum lantana L., Berberis vulgaris L., Rosa maeotica Dubovik. All of this emphasizes the significant conservation value of the studied floodplain. The adventitious flora is represented by 95 species (29.6% of the total flora of the floodplain), among which five species are invasive. The macrophytic vegetation of the Inhulets floodplain is distributed in the coastal shallow waters, which are on average up to 5 meters wide and are represented by intermittent bands of air-water and submerged vegetation. Higher aquatic vegetation is characterized by intermittent-zonal and border types of overgrowth. The results of the study show a fairly high phytodiversity of the floodplain of the Ingulets River – 22.94% of the total number of flora species of the Right Bank Steppe Dnipro region, and is also important for the creation of a cadastre of plant species of Ukraine and for river restoration and management.

Spatial modeling of air pollution in Kharkiv city


 
 
 One of the most pressing problems facing cities, which negatively affects public health. There is a global practice of online monitoring of the content of pollutants in the air of settlements and informing the population about dangerous periods of increased pollution concentrations for certain categories of diseases and the population as a whole. It is also likely that one of the factors of pollution spread is the landscape differentiation of the city’s territory. The purpose of the study presented in this article is to develop statistical and cartographic models of the spatial distribution of air pollutants within the city of Kharkiv and to establish the relationship between the degree of air pollution and types of urban landscapes. Methods. Based on the analysis of the main methodological approaches and tasks of cartographic modeling of the spatial distribution of air pollution, the study substantiates the choice of the modeling method in this study; the features of a large city as an object of cartographic modeling of air pollution are assessed. Results. Based on the results of long-term monitoring by the Kharkiv Regional Center for Hydrometeorology, a statistical analysis of the results of the maximum and average content of pollutants in the atmosphere of Kharkiv was made and the spatial distribution of air pollution in Kharkiv (including (dust, carbon monoxide, nitrogen dioxide, sulfur dioxide, formaldehyde) was modeled, and patterns of pollution distribution were identified according to landscape types. Conclusions. In general, the spatial analysis of pollutant concentrations in the territories of Kharkiv showed that, in terms of maximum concentrations, the southeastern part of Kharkiv is most affected by carbon monoxide, nitrogen dioxide, and formaldehyde. The reason for this is the large area of industrial facilities. The northwestern part of the city has the highest concentrations of dust and sulfur dioxide. There is a lowering of the relief in the floodplain type of landscape and dense development. Intensive traffic and lowered relief (floodplain landscape) cause high average concentrations of dust, carbon monoxide, and sulfur dioxide in the southern part of the city. Nitrogen dioxide concentrations exceed the TLK in the northwest. The reason is the lowering of the relief on the outskirts of the city (floodplain landscape). The central part of the city has a high average concentration of formaldehyde. In general, a pattern of high concentrations of pollutants was found on the floodplains of the Lopan and Kharkiv rivers, with the lowest concentrations confined to watershed types of terrain between the Kharkiv and Lopan rivers and the Udy and Lopan rivers.
 
 

Landscape structure of the Middle Lena valley

In this article we present the results of landscape structure study in the Middle Lena valley (Erkeni, Ensieli and Tuimaada), made using GIS mapping based on Sentinel 2 satellite images and ASTER GDEM datasets. Alas complexes and croplands were identified using K-means image segmentation with different initial numbers. Three machine learning algorithms were tested for pixel-based land cover classification. The best result was achieved with the Support Vector Machine classifier. The mapping revealed the landscape structure of 20 spatial units, which were organized into groups of upland, alas, slope, valley and floodplain landscapes. The contrasting landscape structure of the Middle Lena valley was revealed. The northern Ensieli valley is characterized by the predominance of forest larch-pine landscapes, alas complexes mostly dry with steppe meadows are widespread in the watershed. The slopes are dominated by larch forests with patches of birch. The central Tuimaada valley is the most anthropogenically transformed, here steppe meadows and anthropogenic steppes dominate. The plateau part is mainly forested with croplands. The southern valley of the Erkeni is characterized by the smallest area of the valley part dominated by steppe meadows, the slopes of the main bank of the southern and south-eastern exposition are covered with xerophytic meadows. The landscape structure of valleys, floodplain and plakor parts largely determines the specifics of agricultural land use of the local population. The results obtained can be used for further research into the response of permafrost landscapes of the Middle Lena valleys to increased anthropogenic pressure in the context of climate change.

Soils of Floodplain Landscapes of the River Selenga Basin

Soils of Floodplain Landscapes of the River Selenga Basin

Reconstructing valley landscapes. GIS-analyses of past land use changes in three Flemish river valleys since the late 18th century

The restoration of riverine ecosystem services and floodplain landscapes has become an important tool in climate mitigation, however, it is often unclear what landscape a restoration is (or should be) referring to. Little is known moreover, about long-term transitions in historic valley land use or how they echo in contemporary perceptions of floodplain landscapes. Also in densely populated Flanders (in the north of Belgium), where floodplains are quickly losing their natural functions, policymakers are actively in pursuit of climate change adaptation strategies and sustainable valley management. We present the results of a GIS-based reconstruction of historical land use in three Flemish river valleys from 1771 to 2002 and compare them to changes in regional land use. We find that while grasslands initially and to a vast extent covered our selected floodplains, the latter were by the mid-19th century cultivated for agricultural production, in line with a global expansion of arable land and regional demographic growth. Also forest cover in the studied river valleys grew exponentially from the late 19th century, unmatched by regional forest cover. After the Second World War, a denser road network, more area that is built-up and forest plantations visually contributed to valley compartmentalisation and the perception of a closed landscape. Varying soil textures and drainage levels or the (in)ability to manage them properly accounted for different(ly) (timed) land use changes between the studied floodplain areas. Regional changes in historic land use were of lesser importance.

Provenance Analysis of Yellow River Terraces Highlights Causes of Siltation and Natural Hazards in the North China Plain

AbstractThe avulsion and overflow of river courses during floods, a result of channel siltation above the alluvial plain, is a cause of major natural disasters, including huge property damage and destruction of farmlands. The most sensitive to such risks is the very densely populated area of the Yellow River lower reaches, one of China's most important grain‐producing regions. Problems caused by excessive siltation are a critical issue that should be addressed with full knowledge of sediment‐generation processes, and provenance studies are essential to provide fundamental information for effective environmental management. The Sanmen Gorge is the key region where the great sediment mass produced upstream is conveyed from the middle reaches of the Yellow River to its lower reaches. This study of the terrace sequence exposed along the Sanmen Gorge combines geomorphological observations and provenance analysis based on U‐Pb zircon geochronology and heavy minerals to provide a history of sediment transport through time. The combination of previous research and the outcome of the present study demonstrate that before the Yellow River was formed as an integrated sediment‐routing system, sediments fed into the North China Plain were largely derived from local sources. Instead, after the formation of the Sanmen Gorge, huge quantities of sediment, also derived from the Qinling mountains and stored in the Fenwei basin, were flushed into the North China lowlands by the Yellow River. Such an event took place at 1.2 Ma and has since then impacted severely on floodplain landscape and eventually profoundly affected human activities in the region.

Comparative analysis of information products of land cover types
 of high spatial resolution in mapping floodplain landscapes

Intrazonal floodplain landscapes in the southern Russia remain relatively unaffected by the direct impact of anthropogenic activity, while zonal steppe landscapes are almost completely plowed, and semi-desert and desert are subject to high pasture loads. At the same time, climatic changes and the regulation of river flow by hydroelectric dams lead to the redistribution of river flow, which leads to the degradation of floodplain ecosystems due to a decrease in the duration and height of the flood. The construction of hydraulic structures, including shafts, dams, and arrays of irrigated lands, contributes to the withdrawal of significant areas from the floodplain regime. Reducing the duration of high water and the areas of flooding during them entails an increase in the mineralization of groundwater and stabilization of their level, which negatively affects natural floodplain ecosystems. Similar trends of hydrological and climatic changes are characteristic of floodplain landscapes of rivers in the zone of insufficient moisture, for example, the Don and its tributaries, the Volga in its lower reaches, the rivers of Central Asia. For these reasons, it is important to monitor the condition of floodplain landscapes, one of the tools of which is mapping based on remote sensing data. The purpose of this work is to map the types of land cover of floodplain landscapes of the Lower Volga on the basis of thematic information products ESA GlobCover, ESRI WorldCover, FROM-GLC10 with a spatial resolution of 10 m and GlobCover30 (GLC30) with a resolution of 30 m. It has been established that the actual area of wetlands regularly flooded during floods is 48% of the area of the entire territory. The most accurate estimates of the areas of wetlands, reservoirs, meadows and forests were obtained from the data of the ESA GlobCover information product, which is associated with the use of not only Sentinel-2 optical satellite images, but also Sentinel-1 radar. ESA data is recommended for analyzing the state of floodplain landscapes in the zone of insufficient moisture.

Bat Functional Diversity along the Chobe River Floodplain, Botswana

Insectivorous bats are vital components of tropical and subtropical ecosystems in Africa. However, they are not only threatened by habitat fragmentation, agriculture and urbanization but are also difficult animals to study. During 2014, we used acoustic monitoring to assess the activity and relative abundance of three functional guilds of insectivorous bats at eight sites along the Chobe River floodplain, Botswana. The activity of clutter and clutter-edge foragers was significantly higher in the dry season than in the wet season. By contrast, open-air foragers, which typically forage above or away from vegetation, were more active in the wet season than in the dry season. We believe that the availability of natural vegetation and the variability in the detection of the three bat functional guilds by our acoustic detectors likely explain our results. Although bats are volant animals, our study points towards the importance of conserving important structural vegetation elements along the Chobe River floodplain landscape. Large river systems in Africa, such as the Chobe River, are vital for insectivorous bat persistence, and the provision of the ecosystem services they provide. As such, conservation of riparian corridors along rivers is crucial for maintaining intact and diverse bat communities.

Degradation of floodplain integrity within the contiguous United States

Despite the numerous hydrological, geological, and ecological benefits produced by floodplain landscapes, floodplains continue to be degraded by human activities at a much higher rate than other landscape types. This large-scale landscape modification has been widely recognized, yet a comprehensive, national dataset quantifying the degree to which human activities are responsible for this degradation has not previously been evaluated. In this research, we analyze floodplain integrity for the contiguous United States by spatially quantifying the impact of anthropogenic stressors on almost 80,000 floodplain units. We demonstrate the prevalence of human modifications through widely available geospatial datasets, which we use to quantify indicators of floodplain integrity for five essential floodplain functions of flood attenuation, groundwater storage, habitat provision, sediment regulation, and organics and solute regulation. Our results show that floodplain degradation is spatially heterogeneous and that the integrity of nearly 70% of floodplains in the United States is poor. We highlight that quantifying the integrity of spatially explicit floodplain elements can allow for restoration efforts to be targeted to the areas in most desperate need of preservation.

Vegetation Dynamic in a Large Floodplain Wetland: The Effects of Hydroclimatic Regime

Floodplain wetlands are among the most dynamic ecosystems on Earth, featuring high biodiversity and productivity. They are also sensitive to anthropogenic disturbances and are globally threatened. Understanding how flow regime drives the spatiotemporal dynamics of wetland habitats is fundamental to effective conservation practices. In this study, using Landsat imagery and the random forest (RF) machine learning algorithm, we mapped the winter distribution of four wetland habitats (i.e., Carex meadow, reedbed, mudflat, and shallow water) in East Dongting Lake, a Ramsar wetland in the middle to lower Yangtze Basin of China, for 34 years (1988–2021). The dynamics of wetland habitats were explored through pixel-by-pixel comparisons. Further, the response of wetland habitats to flow regime variations was investigated using generalized additive mixed models (GAMM). Our results demonstrated the constant expansion of reedbeds and shrinkage of mudflats, and that there were three processes contributing to the reduction in mudflat: (1) permanent replacement by reedbed; (2) irreversible loss to water; and (3) transitional swapping with Carex meadow. These changes in the relative extent of wetland habitats may degrade the conservation function of the Ramsar wetland. Moreover, the duration of the dry season and the date of water level withdrawal were identified as the key flow regime parameters shaping the size of wetland habitats. However, different wetland vegetation showed distinct responses to variations in flow regime: while Carex meadow increased with earlier water withdrawal and a longer dry season, reedbed continuously expanded independent of the flow regime corresponding to the increase in winter rainfall. Our findings suggested that flow regime acts in concert with other factors, such as climate change and sand mining in river channels, driving wetland habitat transition in a floodplain landscape. Therefore, effective conservation can only be achieved through diverse restoration strategies addressing all drivers.

Localized Vegetation, Soil Moisture, and Ice Content Offset Permafrost Degradation under Climate Warming

Rapid Arctic warming is expected to result in widespread permafrost degradation. However, observations show that site-specific conditions (vegetation and soils) may offset the reaction of permafrost to climate change. This paper summarizes 43 years of interannual seasonal thaw observations from tundra landscapes surrounding the Marre-Sale on the west coast of the Yamal Peninsula, northwest Siberia. This robust dataset includes landscape-specific climate, active layer thickness, soil moisture, and vegetation observations at multiple scales. Long-term trends from these hierarchically scaled observations indicate that drained landscapes exhibit the most pronounced responses to changing climatic conditions, while moist and wet tundra landscapes exhibit decreasing active layer thickness, and river floodplain landscapes do not show changes in the active layer. The slow increase in seasonal thaw depth despite significant warming observed over the last four decades on the Yamal Peninsula can be explained by thickening moss covers and ground surface subsidence as the transient layer (ice-rich upper permafrost soil horizon) thaws and compacts. The uneven proliferation of specific vegetation communities, primarily mosses, is significantly contributing to spatial variability observed in active layer dynamics. Based on these findings, we recommend that regional permafrost assessments employ a mean landscape-scale active layer thickness that weights the proportions of different landscape types.

Individual Morphometric Characters and Productivity of <i>Plantago maxima</i> (Plantaginaceae) in the South Siberia (Republic of Khakassia)

Abstract—Phytocoenotic and morphological features, as well as the productivity of the giant plantain (Plantago maxima Juss. ex Jacq.) in typical floodplain landscapes of southern Siberia were studied. The coenopopulations of P. maxima growing in natural and reclaimed areas of the Bely Iyus River valley in the Shirinsky and Ordzhonikidzevsky districts of the Republic of Khakassia were assessed. Under contrasting environmental conditions, in associations with significant share of P. maxima its productivity was 8.2 ± ± 0.58 kg × 102∕ha of air-dry, and 7.7 ± 0.54 kg × 102∕ha of oven dry aboveground phytomass. P. maxima share of the total phytomass varies from 5 to 15% in mesophytic associations with high species diversity on well-drained soils, and from 40 to 80% in xerophytic associations confined to mounds with sandy, sandy-gravelly or pebbly sandy soils. In P. maxima, the size and variability of vegetative organs increase in plants growing in more moist environments, while in drier habitats, the generative structures increase in the size and variability.

Analysis of ecofloristic diversity of the Poaceae family of forest biogeocenoses of the northern steppe Prydniprovya

It is difficult to overestimate the importance of cereals in the functioning of natural ecosystems and their use for human life. They often play the role of dominants and edifiers in the composition of plant cover, primarily herbaceous types of vegetation. But they also take part in the composition of forest phytocenoses of different natural zones. Within Ukraine, the Poaceae family includes 71 genera (of which only 4 are in culture) and 208 species (of which only 15 are in culture) [20]. The cereal flora of forest biogeocenoses of the analyzed area was studied in the end of the 19th century [1]. Since the studied forest complexes are located within the steppe zone with various conditions of watershed-beam and valley-terrace landscapes, they contain species of various ecomorphs: from xerophytes to hygrophytes (or even helophytes); from heliophytes to sciophytes, from oligotrophs to megatrophs. The flora of forest biogeocenoses of the northern steppe Prydniprovya region includes 73 species of vascular plants. The greatest species richness belongs to the flora of floodplain forests, which confirms the statement about the extraordinary biodiversity of floodplain landscapes [35]. Of the entire flora of forest biogeocenoses, hemicryptophytes (42 species) predominate among climamorphs, heliophytes (66 species) predominate among heliomorphs, mesotrophs (39 species) among trophomorphs, and mesophytes (45 species) among hygromorphs. Among the coenomorphs, the majority are forest-meadow (55 species) and ruderal-forest (18 species). The Roaceae family of the forest biogeocenoses of the northern steppe Prydniprovya region includes 6 rare species that are included in the regional red list of rare plants [29]. The ecomorphic analysis of the flora confirms the peculiarities of the physical and geographical conditions of different types of forests. Among the climamorphs, hemicryptophytes predominate in birachous and wall forests. The majority of heliophytes are characteristic of arenaceous forests, and sciophytes are characteristic of floodplain forests. Among trophomorphs, megatrophs predominate in birachous and walled forests, oligotrophs in arena forests. The largest number of hygrophytes is characteristic of floodplain forests, and xerophytes is characteristic of arena forests. The forest biogeocenoses of the northern steppe Prydniprovya are characterized by significant anthropogenic transformation of the vegetation cover. In the composition of the forest flora, there are only 16 purely ruderal (weedy) species, and 23 ruderal species in mixed ecomorphs. Among them, 16 are adventive ruderal species. The assessment of anthropogenic transformation of the plant cover using the hemerobium method shows that the majority of the hemerobium species belong to mesohemerobes – species that grow on the territories of landscapes with a medium degree of transformation. This indicates a moderate transformation of the forest biogeocenoses of the northern steppe Prydniprovya. Among all types of forests, the least transformed are floodplain, ravine and wall forests.

Ecological value of gravel pit ponds for floodplain wetland fish

Abstract Floodplain wetlands support high biodiversity, but they have been degraded and geographically fragmented due to human activities. Some types of human‐created waterbodies have received growing attention as alternative habitats for conserving wetland biodiversity. Gravel pit ponds (GPPs) are human‐created wetlands formed when a gravel pit is excavated at or below the water table and filled with groundwater. Differences in community structure among GPPs and floodplain wetlands with respect to habitat characteristics are scarcely known, resulting in insufficient evaluations of the ecological value of GPPs for floodplain wetland species. In this study, we evaluated the ecological value of GPPs for wetland fishes in floodplain landscapes. We surveyed fish abundance, community composition, and 10 environmental factors in GPPs and two types of floodplain ponds (remnant ponds and river backwaters) to clarify the biotic and abiotic differences among the pond types. Environmental factors were similar among the pond types, with only water temperature and the distance from the main channel to the pond significantly lower in river backwaters. The richness and abundance of native fish species did not differ among the pond types, but species composition did. Rhynchocypris percnura sachalinensis, Carassius sp., and Lethenteron sp. N (one of the two cryptic species of Lethenteron reissneri) were selected as indicator species in GPPs, remnant ponds, and river backwaters, respectively. These results indicate that GPPs provide valuable habitats for wetland fishes in floodplain landscapes and support regional γ diversity. Since many species inhabited the GPPs in this study, including red list species, appropriate management of GPPs is important to conserve wetland fishes.

Land-Use Changes on Ob River Floodplain (Western Siberia, Russia) in Context of Natural and Social Changes over Past 200 Years

Over the past century, substantial changes in land use have taken place in the boreal zone of northern Eurasia. The consequences of these large-scale changes for the ecosystems of Europe have been well studied; however, they have not been addressed for the large expanses of Russia. We conducted a retrospective analysis of the landscape dynamics of the middle reaches of the Ob floodplain (Western Siberia) using multitemporal maps of the vegetation cover and land use for five time points (1830, 1910, 1950, 1976, and 2019). By the 1830s, all the land that was suitable for haymaking and plowing (rarely flooded and not swamped) had been put to agricultural use. The meadows of the Ob floodplain are human-controlled and were mainly formed before the 1830s. From the 1830s to the 1990s, the meadows were used in agriculture and their areas increased. The maximum development of the floodplain occurred in the 1970s and 1980s, when previous wetlands were put into operation through the construction of drainage systems. A massive abandonment of pastures and reclaimed land occurred in the late 20th century. According to the data over the last 30 years, abandoned meadows are resistant to overgrowth with trees and shrubs. The spatial configurations of the floodplain landscapes have also been quite stable. The main spatial changes are confined to the near-channel floodplain, with the formation of new near-channel shallows. The floodplain landscapes of the Ob River demonstrate substantial spatial and temporal stabilities, and long-standing agricultural development.

Natural Radionuclides in Soils of Natural-Technogenic Landscapes in the Impact Zone of Potassium Salt Mining

This study considers the contents of natural radionuclides (226Ra, 232Th, and 40K) in the soils of natural–technogenic landscapes in the Verkhnekamskoe potassium–magnesium salt deposit (Perm Krai, Russia). The purpose of the study is to assess the lateral activity distribution of natural radionuclides (226Ra, 232Th, and 40K) in the soils of natural–technogenic landscapes of the mining areas on the territory of the Berezniki–Solikamsk industrial hub. Seventy-five soil samples from depths of 0–0.4 m are examined. The specific activities of the natural radionuclides 226Ra, 232Th, and 40K in the soil samples are measured using gamma spectrometry. The average values of the activity concentrations of 226Ra, 232Th, and 40K are 11.78 Bq/kg, 8.11 Bq/kg, and 246.9 Bq/kg, respectively. A gamma survey is conducted using the MKS/SRP-08A search dosimeter–radiometer over a control point framework covering 50,000 hectares. The research shows that the migration of the studied natural radionuclides is limited to a radius of 10 km. The results of the gamma-radiation measurements in the study area fall within a range of 0.06–0.25 µSv/h, which does not exceed the permissible limits. According to the findings, there is an increase in the concentration of natural radionuclides in transit supra-floodplain terrace landscapes and accumulative floodplain landscapes in the area affected by potash mining.

Flow resistance in a subtropical canyon river

We conducted several field surveys to measure velocity and channel geometry in 15 cross-sections distributed along three reaches in the Boi River (Southern Brazil), a canyon river that belongs to the most extensive canyon chain in South America. The three reaches present, respectively, canyon, transition, and floodplain landscapes. The resulting data were used to compute the flow resistance. A downstream hydraulic geometry analysis indicates that the exponent describing the velocity increases with the discharge and that these values were between 0.3043 and 0.3507. A downstream hydraulic geometry analysis indicates that changes in velocity with discharge are greater than the rate of change of width or depth. It is typically found in steep mountain streams laterally confined, and it was verified in the canyon reach. However, despite the transition presents a considerable lateral constriction and the floodplain reach presents mountain river characteristics, both reaches did not present such behavior. The findings are coherent with other mountain river datasets, although the Boi River presents distinct geomorphic units such as glide-runs. In contrast, other available datasets are usually characterized by step-pool channels. Flow resistance in the canyon and transition reaches differ in many ways from floodplain reach, indicating larger resistance inside the canyon than outside, probably related to the landform and grain size in the canyon. Regression analysis of the combined field dataset indicated that dimensionless unit discharge is an important independent variable to explain variations in velocity and flow resistance. We also verified that the use of Rickenmann's Equation can be helpful to estimate velocity in canyon rivers. Our findings include: i) canyon landscape presents higher friction factors than floodplain landscape; and ii) canyon and transition landscapes are similar in terms of flow resistance during high-flow conditions, while floodplain present remarkably differences.

Reproductive Strategies and Population Genetic Structure in Two Dryland River Floodplain Plants, Marsilea drummondii and Eleocharis acuta.

Aquatic plants share a range of convergent reproductive strategies, such as the ability to reproduce both sexually and asexually through vegetative growth. In dryland river systems, floodplain inundation is infrequent and irregular, and wetlands consist of discrete and unstable habitat patches. In these systems, life history strategies such as long-distance dispersal, seed longevity, self-fertilisation, and reproduction from vegetative propagules are important strategies that allow plants to persist. Using two aquatic plants, Marsilea drummondii and Eleocharis acuta, we investigated the proportions of sexual and asexual reproduction and self-fertilisation by employing next-generation sequencing approaches, and we used this information to understand the population genetic structure of a large inland floodplain in western New South Wales (NSW), Australia. Asexual vegetative reproduction and self-fertilisation were more common in M. drummondii, but both species used sexual reproduction as the main mode of reproduction. This resulted in a highly differentiated genetic structure between wetlands and a similar genetic structure within wetlands. The similarity in genetic structure was influenced by the wetland in the two species, highlighting the influence of the floodplain landscape and hydrology on structuring population genetic structure. The high levels of genetic variation among wetlands and the low variation within wetlands suggests that dispersal and pollination occur within close proximity and that gene flow is restricted. This suggests a reliance on locally sourced (persistent) seed, rather than asexual (clonal) reproduction or recolonisation via dispersal, for the population maintenance of plants in dryland rivers. This highlights the importance of floodplain inundation to promote seed germination, establishment, and reproduction in dryland regions.