Typical Floodplain Research Articles

Effect of ground water level on the release of carbon, nitrogen and phosphorus during decomposition of Carex. cinerascens Kükenth in the typical seasonal floodplain in dry season

From November 2016 to April 2017, the decomposition of Carex. cinerascens Kükenth litter along the natural gradients of groundwater level at Poyang Lake wetland beach were simulated using litterbag technique. The depth of the underground water table of the G-L was −25 to −50 cm, while those of G-ML, G-MH and G-H ranged from −15 to −25 cm, −5 to −15 cm, and −5 to 5, respectively. Additionally, the dry weight loss rate increased gradually with increasing days, with that of G-H being highest, followed by G-MH, G-ML and G-L. The decomposition rate of the four gradients increased rapidly to day 30, then decreased slowly until stabilizing. Additionally, the decomposition rate was highest in G-H, followed by G-MH, G-ML and G-L. The Olson negative exponential model could simulate the decomposition good and predicted the time required for 50% decomposition of the G-H, G-MH, G-ML and G-L gradients was about 166, 197, 205 and 247 days, respectively, while required for 95% was about 1.97, 2.23, 2.43 and 2.92 years, respectively. The overall trend in the relative return index of carbon, nitrogen and phosphorus increased with increasing decomposition days, and the order was G-H > G-MH > G-ML > G-L. Differences in soil pH, bulk density, soil total nitrogen, soil organic matter, microbial biomass carbon and soil sand content in the decomposed environment due to groundwater had a significant impact on decomposition and nutrient release. The relative return index of carbon was significantly positively correlated with soil pH, but significantly negatively correlated with soil bulk density, soil nitrogen content, microbial biomass nitrogen and soil organic matter. The above results show that groundwater is the key factor influencing litter decomposition in Poyang Lake wetland during the dry season, with higher groundwater levels promoting the decomposition.

Zooplankton in two small reservoirs of the Tuva Republic

The article provides information on the species composition and quantitative indicators of zooplankton in two small mountain reservoirs of the Tuva Republic: the Eerbek and Turan. They reflect the first and the third years of the ecosystem existence after seasonal drawdown. Regulation shows a typical pattern in the distribution of zooplankton in the reservoirs: an increase in density in the dam section. In general, the reservoir zooplankton has a floodplain type of formation. The existence periods of reservoirs influences the zooplankton structure and its development: regulation in the first year determines the development of crustacean zooplankton (represented mainly by cladocerans), usually with monodominance; over three years, all main groups of zooplankton develop, but drawdowns interrupt the formation on the normal ecosystem in the reservoir.

Zarys przyrodniczych i antropogenicznych uwarunkowań rozwoju systemów dolinnych i korytowych w Polsce

The paper is an attempt to review the state of current knowledge and discussion on the evolution and typology of valley and river channel systems in Poland. Contemporary landscapes of valley systems and river channel systems reflect the overlap of multiple natural and anthropogenic factors. Among them, climate changes and regional morphotectonic and morphogenetic determinants are of crucial importance. Over the last decades, these landscapes have undergone substantial transformations, among others as a result of climate change and as a consequence of changing hydrological conditions, land use, as well as a result of increasing human interference in river channel and valley systems. It thus follows from the circumstances that attempts are made to classify different evolutionary types and subtypes of river valleys and different types of contemporary river channel patterns and floodplains that reflect complex and often overlapping natural and anthropogenic conditions.

Selection of optimal escape routes in a flood-prone area based on 2D hydrodynamic modelling

Abstract Optimizing escape routes during an extreme flood event is an effective way to mitigate casualties. In this study, a model for selecting optimal escape routes in a flood-prone area has been proposed, which includes a module for predicting the two-dimensional (2D) hydrodynamics and modules for assessing the hazard degree for evacuees, calculation of evacuation times and determination of different escape routes. In the module for determining escape routes, two evacuation schemes were used: scheme A to find optimal escape routes based on established road networks and scheme B to design a new optimal evacuation route. Extreme overbank floods occurred in the Lower Yellow River (LYR) in July 1958 (‘58.7’) and August 1982 (‘82.8’) and the proposed model was applied to select the optimal escape routes on a typical floodplain area of the LYR for these two floods. Model predictions indicated that: (i) the optimal escape routes for these two floods were the same for all three starting locations, and the optimized routes provided 3 h more time for evacuees to escape; and (ii) the time of evacuation would need to be earlier for the ‘58.7’ flood because of its larger amount of water volume and higher peak discharge.

Mineral matter composition of drained floodplain soils in north-eastern Poland

Abstract Soils in two river valleys (Rozoga and Omulew) in north-eastern Poland were investigated. The valleys are located on a sandy outwash plain formed during the Vistulian (Weichelian) Glaciation. The soils are drained, used as meadows and classified as Fluvic Umbric Gleysol, Fluvic Mollic Gleysol, and Eutric Fluvic Histic Gleysol (IUSS Working Group WRB 2015). The aim of the study was to identify the composition of mineral matter and to determine the types of clay minerals and intermediate stages of clay minerals by means of the X-ray diffraction (XRD). The studied floodplain soils are rich in organic matter and contain considerable mineral alluvial admixtures. The content of clay fraction (< 2.0 μm) is low (0.02–5.61% of total mineral matter). Higher content of clay fraction was noted in soils with elevated content of organic matter, which can be evidence of simultaneous accumulation of both components. In deeper depressions occurring in river valleys (oxbow lakes), a specific deposit termed silty telmatic mud (16–24% TOC, 50–75% silt, 3.1–5.6% clay fraction content) was accumulated. On the other hand, in shallow depressions, a muddy deposit was accumulated (5.7–7.7% TOC, sandy texture). The main identified clay minerals were smectite, vermiculite, illite and kaolinite as well as variety of mixed-layer clays. Alluvial clay admixture in studied soil formations showed mineralogical similarity to typical floodplain mineral soils (Fluvisols). Mineral fraction of studied soils is mostly of allochthonous origin.

Mesoscale river restoration enhances the diversity of floodplain vegetation

AbstractEffective river restoration aims for the recovery of ecosystem functions by restoring processes and connectivity to the floodplain. At the straightened lowland river Stör in northern Germany, a sequence of 15 new meanders was created in 2008, with wavelengths up to 70 m. The newly created areas within the meander bends range in size from 215 to 1,115 m2 and function as a series of 15 restored floodplain sites, which are subject to succession. After 7 years of restoration measures, we investigated the vegetation dynamics on the (a) restored floodplains and compared them with adjacent floodplain sites that were used as (b) low‐intensity grazed grassland or as (c) abandoned grassland. We analysed the species diversity, functional vegetation parameters, and plant communities of 200 plots within the floodplain area of the three floodplain types and of 246 plots at their river banks.Plant species diversity and composition differed with respect to restoration measure and site management. Restored floodplains revealed a higher coverage in species of wet grasslands and softwood forests and higher species diversity than abandoned grasslands. Grazed grasslands showed the highest species number and coverages of pioneer vegetation. The banks indicated fewer differences in species composition between floodplain types.The construction of restored floodplains revealed greater overall plant diversity due to promoting the development of typical floodplain vegetation. Shallow meanders with increased flooding intensity and the creation of a varying microreliefs are recommended as combined river/floodplain measures in order to foster processes and connectivity between valley components.

Consequences of the river valley bottom transformation after extreme flood (on the example of the Niida River, Japan)

Detailed study of different sections of floodplain was undertaken in the Niida River basin (Fukushima Prefecture) after an extreme flood event which occurred in the middle of September 2015. The upstream part of the basin is located in the area with very high level of radionuclide contamination after the accident at Fukushima Dai-ichi NPP. Field and GIS methods were used, including direct measurement of the depth of fresh sediment and its area, with soil descriptions for the typical floodplain sections, measurement of dose rates, interpretation of space images for a few time intervals (before and after flood event) with the following evaluation of spatial changes in deposition for different floodplain sections. In addition, results of quantitative assessment of sedimentation rates and soil radionuclide contamination were applied for understanding the effect of extreme flood on alluvial soils of the different sections. It was established that the maximum sedimentation rates (20-50 cm/event) occurred in the middle part of the lower reach of the Niida River and in some locations of the upper reaches. Dose rates had reduced considerably for all the areas with high sedimentation because the top soil layers with high radionuclide contamination were buried under fresh sediments produced mostly due to bank erosion and mass movements.

Effects of moisture conditions on the small mammal communities of floodplain forests in south Moravia (Czech Republic)

Changes of the moisture regime and its influence on the dominance of selected species of small mammal communities were studied in floodplain forests in southern Moravia (river Dyje). In period of typical floodplain regime characterized by groundwater table fluctuation (1968–1972, with high groundwater table level or floods in spring) dominance of Apodemus flavicollis (Mel.) was 42%, Myodes glareolus (Schreb.) 33% and Sorex araneus L. 15% of the total small mammal communities. In period 1982–1987 after cessation of floods by river regulation, rapid groundwater drop and changes in the herb layer, the dominance of Apodemus flavicollis and Myodes glareolus increased. Also the dominance of Apodemus sylvaticus (L.) increased, but that of Sorex araneus collapsed. Further revitalization measures were applied by systems of channels supplying the water to root system of forest trees but not to the herb layer. In 2002–2006 decreasing moisture condition further influenced the dominance of Apodemus flavicollis reaching mean dominance 62%, Myodes glareolus dominance decreased to 20% and that of Sorex araneus remain to be low. All estimated changes were correlated with moisture regime changes and were significant. Thus the changes in the forest moisture regime significantly affect the community of small terrestrial mammals.

Seasonal Water Exchanges between China’s Poyang Lake and Its Saucer-Shaped Depressions on River Deltas

The saucer-shaped depressions located at the river deltas of Poyang Lake are typical floodplain shallow sub-lakes subject to river-lake connection or isolation. The hydrological connectivity between these depressions and the main lake has a major influence on the hydrologic function and ecological integrity of the lake-floodplain and associated wetland habitats. This study explored the water level fluctuations and water exchange processes between the Poyang Lake and three typical saucer-shaped depressions, using a 30-min temporal resolution of water level observations during 2015–2016. Our results showed that the water level correlation and hydrological connectivity between the main lake and its depressions displayed a strong seasonal and spatial signal. Temporally, the rainfall significantly influences the seasonality and frequency of water level fluctuations both in the main lake and the depressions. The correlation coefficient of the water level ordered from high to low occurred during the high-water period, the rising-water period, the falling-water period and the low-water period, respectively. Spatially, depressions with a shorter connection duration to the main lake are located at higher local elevation and at larger geographical distance from the main lake. Finally, we also discussed the implications of these findings and possible factors that could have caused these particular water regime characteristics and water exchange processes.

Vegetation development after a large scale restoration of species-rich grasslands in a Central European floodplain

Large scale restoration using local high-diversity seed mixture combined with turf transfer was applied on ex-arable land in the Morava River floodplain in the western Slovakia in the years 1999–2012. The post-restoration vegetation development was recorded during 12 years after the restoration using floristic records per restored polygons with cover estimation in simple 3-degree scale. Temporal changes in species composition were evaluated by gradient analysis and number of characteristic grassland and ruderal species on restored sites was analysed by general linear models. Species composition changed gradually towards the species composition typical for species-rich floodplain grasslands, but the trajectory was not straightforward and several irregularities were observed. They were probably induced by extreme weather events (drought, floods). The decrease in ruderal species and increase in the number of typical floodplain grassland species were observed, when floodplain grassland species permanently outcompeted ruderal species since 8th year after the restoration. However the development in large scale was slower, than expected from previous small-scale experiments, it is evident, that combination of local seed mixture sowing with a turf transfer is a feasible method for the restoration of species-rich floodplain grasslands from arable land.

Effect of the Gabčíkovo Waterworks (Slovakia) on riparian floodplain forest ecosystems in the Danube inland delta: vegetation dynamics and trends

AbstractHuman alteration of watercourses is global phenomenon that has had significant impacts on local ecosystems and the services they provide. Monitoring of abiotic and biotic changes is essential to mitigating long-lasting effects, and the 23-year dataset from the Gabčíkovo Waterworks provided a rare opportunity to assess the impact of groundwater regimes on vegetation. The main aim of this study was to describe the effect of the Gabčíkovo Waterworks on vegetation structure and species composition of the adjacent riparian floodplain forests over the past 23 years. The results are based on studies of three permanent monitoring plots (PMPs) located in the Danube inland delta – two outside (PMP 1 and 3) and one (PMP 2) fully under the influence of the artificial supply system. Our results demonstrate that the Danube inland delta was negatively affected by the Gabčíkovo construction, particularly for sites outside of the artificial supply system. There was a significant decrease in soil moisture and increase in nitrogen at both external PMPs (1 and 3). Alter soil conditions were accompanied by negative changes in plant species composition demonstrated by decreases in the number of typical floodplain forest species that are characteristic for the alliance

Land Cover Changes (1963–2010) and Their Environmental Factors in the Upper Danube Floodplain

To analyze the changes in the Upper Danube Floodplain, we used aerial photos to quantify the change of landscape pattern from 1963 to 2010. We focused on typical floodplain habitats, i.e., riparian forest and floodplain grassland. We used landscape metrics and transformation matrix to explore changes in land cover structure and composition. The active floodplain experienced increasing fragmentation from 1963 to 2010. Despite an increase of aggregation, riparian forest suffered a 2.3% area loss from 1995 to 2010. Arable land in the active floodplain declined by 28.5%, while its patch size significantly increased. Elevation, distance to river and soil quality were the most relevant environmental factors for the land cover change in the floodplain. Higher soil quality or longer distance to river led to an increase of conversion from grassland into arable land; grassland patches with poorer soil quality were likely to change into riparian forest; riparian forest closer to the river and with a lower height above mean water level tended to remain stable. This comprehensive understanding of historical land cover change and environmental factors is needed for the enhancement of landscape functions and sustainable development in the floodplain.

ПРИРОДНИЧО-ГЕОГРАФІЧНА СКЛАДОВА ТУРИСТИЧНИХ МАРШРУТІВ (НА ПРИКЛАДІ МАРШРУТУ ДОЛИНОЮ ЧОРНОЇ ТИСИ)

Using the example of the famous tourist route to the sources of the Chorna Tisa river, the possibility and necessity of use information about geological, geomorphological, hydrological and landscape features of the territory as tourist objects in order for popularize natural knowledge, are presented іn the work. A tourist route is proposed, which represented a combination of historical, cultural and natural information about the region. In the work focus is on natural objects that could interest tourists. As objects containing scientific cognitive natural information is invited to consider exits to the surface flysch complex, illustrating features of formation of the substance of the Carpathian Mountains, features of the transverse and longitudinal structure of valley of the mountain river, anthropogenic and natural-anthropogenic landforms and results their transformation over time, the consequences of exogenous processes. In addition, the document provides information on the features of the formation, distribution and changes of natural-territorial complexes, which can be seen on the route. The article mentions the floodplain, terraces, slopes and vertex natural complexes which are successively change during route. General data about typical plant communities in this region are presented. Attention is drawn to the character of typical economic use of natural systems and the consequences of inefficient use of nature in the region. The scheme of the route, showing points of observation are presented in the work. At these points can more fully to assess the natural features of the area and the changes which occur during typical use of nature in this region. The route is designed so that tourists can observe the typical floodplain geosystems covered hydromorphic plant communities and natural systems of low wetland terraces covered with vegetation typical of this bows, which are mainly used today as hay fields. Geosystems of slopes covered spruce forests, often drawing attention to themselves as a territory which is an example of unsustainable forest management. Some of these areas in the recent past were timber harvesting sites. In areas such apparent substitution of plant communities of Picea Abies prevailing in the area, the secondary shrub communities, forming dense thickets – so-called crimson logging. Polonyna Ripta Apshynetska is an area of felled forest, covered secondary associations of bows, which is using for traditional in the region transhumance grazing-type agriculture. At the end of the route in the upper part of mountain range Svydovets, a location is proposed, which is very successful, to explore the orographic structure of the Ukrainian Carpathians.

Controls on the occurrence and prevalence of floodplain channels in meandering rivers

AbstractThe process of channelization on river floodplains plays an essential role in regulating river sinuosity and creating river avulsions. Most channelization occurs within the channel belt (e.g. chute channels), but growing evidence suggests some channels originate outside of the channel‐belt in the floodplain. To understand the occurrence and prevalence of these floodplain channels we mapped 3064 km2 of floodplain in Indiana, USA using 1.5 m resolution digital elevation models (DEMs) derived from airborne light detection and ranging (LiDAR) data. We find the following range of channelization types on floodplains in Indiana: 6.8% of floodplain area has no evidence of channelization, 55.9% of floodplains show evidence (e.g. oxbow lakes) of chute‐channel activity in the channel belt, and 37.3% of floodplains contain floodplain channels that form long, coherent down‐valley pathways with bifurcations and confluences, and they are active only during overbank discharge. Whereas the first two types of floodplains are relatively well studied, only a few studies have recognized the existence of floodplain channels. To understand why floodplain channels occur, we compared the presence of channelization types with measured floodplain width, floodplain slope, river width, river meander rate, sinuosity, flooding frequency, soil composition, and land cover. Results show floodplain channels occur when the fluvial systems are characterized by large floodplain‐to‐river widths, relatively higher meandering rates, and are dominantly used for agriculture. More detailed reach‐scale mapping reveals that up to 75% of channel reaches within floodplain channels are likely paleo‐meander cutoffs. The meander cutoffs are connected by secondary channels to form floodplain channels. We suggest that secondary channels within floodplains form by differential erosion across the floodplain, linking together pre‐existing topographic lows, such as meander cutoffs. Copyright © 2016 John Wiley & Sons, Ltd.

Vegetation resilience to mega‐drought along a typical floodplain gradient of the southern Murray‐Darling Basin, Australia

AbstractQuestionsHow diverse and resilient is vegetation following a decade of extreme drought along a typical floodplain gradient of semi‐arid south‐eastern Australia? How do mechanisms of resilience (i.e. persistence and soil seed banks) vary between major plant groups and spatially with respect to habitat type and position along a flood frequency gradient?LocationSouthern Murray‐Darling Basin, Australia.MethodsWe surveyed understorey vegetation and conducted germination trials to examine responses to re‐wetting from soil seed banks of seven major habitat types along a typical floodplain gradient of the southern Murray‐Darling Basin. We assessed abundance, species richness, functional diversity and composition, including exotic species, within and between extant and germinating assemblages.ResultsUnderstorey vegetation was surprisingly diverse, although low in cover, following a decade of extreme drought, with considerable numbers of plant species (61) and functional plant groups represented. Historically drier habitats, towards floodplain margins, had higher species richness and cover overall and for exotic species. Plant assemblages exhibited high heterogeneity between habitats. Soil seed banks were very dissimilar from extant vegetation, comprising mainly amphibious and damp taxa as well as some terrestrial herbs, mostly annuals. Seed banks were most abundant and diverse in intermediate floodplain habitats, and their composition was very distinct between habitat types.ConclusionsSemi‐arid floodplain vegetation is likely to be highly resilient to prolonged drought. Plants persisting under dry conditions do not appear to rely on local soil seed banks for regeneration and may either tolerate drying in situ or arrive from neighbouring ecosystems. Soil seed banks allow understorey vegetation to respond to re‐wetting, especially in intermediate floodplain habitats. Lake bed assemblages and aquatic/amphibious species lacking soil seed banks appear most vulnerable to drought. Vegetation resilience is promoted by landscape heterogeneity.

Unionid mussel composition and ditch environments in floodplain and alluvial fan geomorphic types: a case study of a Lake Biwa river basin

To determine the differences in the ditch environments and mussel composition between floodplains and alluvial fans, two geomorphic types in a Lake Biwa river basin were surveyed. An intrinsic Gaussian conditional autoregressive (CAR) model was applied to assess the relationship between the density of Nodularia douglasiae biwae, the dominant species in the floodplain area, and ditch environment. Relative to the alluvial fan area, ditches in the floodplain area had higher percentages of muddy and sandy substrates, a lower percentage of pebble substrates, greater sediment softness, faster flow velocity, and deeper water depth. N. d. biwae and Pronodularia japanensis were collected in both the floodplain and alluvial fan areas. Lanceolaria grayana and Sinanodonta japonica were captured only in the floodplain area, and Sinanodonta lauta was found only in the alluvial fan area. The differences in the ditch environments between the two geomorphic types and the drought tolerance of the mussel species may explain why the mussel composition differs between the two geomorphic types. The CAR model indicated that N. d. biwae was more abundant in ditches with sandy and soft sediment and with deeper water. It also points to the importance of microhabitat-scale sampling to determine the relationship between unionid density and ditch environment.

Assessing the variable ecosystem services relationships in polders over time: a case study in the eastern Chaohu Lake Basin, China

Land use changes can isolate habitat patches, thereby aggravating the fragmentation of these units and altering natural ecological processes. Thus, it is necessary to analyze the responses of ecosystem services to changes in land use over time. Polders, a typical floodplain landscape in the Chaohu Lake Basin, were selected as the study area to evaluate how ecosystem services respond to changes in both land use and patch size over time. Multiple approaches, including remote sensing, geographical information system and correspondence analysis, were used. The results showed that the total ecosystem services were increased from 9.97 × 108 to 1.02 × 109 Yuan for all polders. Based on a correspondence analysis, recreation and culture, water supply and waste treatment are the ecosystem services that depend on water bodies, whereas six other types of ecosystem services (biodiversity protection, climate regulation, food production, raw material, soil formation and protection and gas regulation) depend on soil. Therefore, there are trade-offs between the ecosystem services provided by farmlands and those provided by water bodies, between supporting and provisioning services and cultural services in the polders, and between provisioning services and most regulating services. Furthermore, trade-offs and synergies were detected among regulating services. In this study, the relationships between patch sizes and ecosystem services were significantly changed during the 1985–2007 period, particularly from 2000 to 2007. The area variation of special land use can drive changes in these relationships. Notably, correspondence analysis can be used as a method to analyze synergies and trade-offs among multiple ecosystem services.

Characterization of a Highly Biodiverse Floodplain Meadow Using Hyperspectral Remote Sensing within a Plant Functional Trait Framework

We assessed the potential for using optical functional types as effective markers to monitor changes in vegetation in floodplain meadows associated with changes in their local environment. Floodplain meadows are challenging ecosystems for monitoring and conservation because of their highly biodiverse nature. Our aim was to understand and explain spectral differences among key members of floodplain meadows and also characterize differences with respect to functional traits. The study was conducted on a typical floodplain meadow in UK (MG4-type, mesotrophic grassland type 4, according to British National Vegetation Classification). We compared two approaches to characterize floodplain communities using field spectroscopy. The first approach was sub-community based, in which we collected spectral signatures for species groupings indicating two distinct eco-hydrological conditions (dry and wet soil indicator species). The other approach was “species-specific”, in which we focused on the spectral reflectance of three key species found on the meadow. One herb species is a typical member of the MG4 floodplain meadow community, while the other two species, sedge and rush, represent wetland vegetation. We also monitored vegetation biophysical and functional properties as well as soil nutrients and ground water levels. We found that the vegetation classes representing meadow sub-communities could not be spectrally distinguished from each other, whereas the individual herb species was found to have a distinctly different spectral signature from the sedge and rush species. The spectral differences between these three species could be explained by their observed differences in plant biophysical parameters, as corroborated through radiative transfer model simulations. These parameters, such as leaf area index, leaf dry matter content, leaf water content, and specific leaf area, along with other functional parameters, such as maximum carboxylation capacity and leaf nitrogen content, also helped explain the species’ differences in functional dynamics. Groundwater level and soil nitrogen availability, which are important factors governing plant nutrient status, were also found to be significantly different for the herb/wetland species’ locations. The study concludes that spectrally distinguishable species, typical for a highly biodiverse site such as a floodplain meadow, could potentially be used as target species to monitor vegetation dynamics under changing environmental conditions.

The melliferous potential of apiflora of southwestern Vojvodina (Serbia)

The individual and community-level melliferous potential of apiflora was evaluated in southwestern Vojvodina in order to assess its significance and contribution to the bee pasture. Seven plant communities belonging to ruderal, segetal and floodplain type of vegetation, with a total of 279 plant species were registered. Apifloristic and phytocoenological investigations included the determination and analysis of honey plants using the following parameters: total number, percentage, abundance and frequency of these species in the communities, as well as their intensity of pollen and nectar production. The coenotic coefficient of melliferousness (CCm) indicating the melliferous potential of each community, was calculated based on the above parameters. Although the greatest number of melliferous species was found in the ass. Chenopodio-Ambrosietum artemisiifoliae (132), the highest percentage (80%) of them was registered in the ass. Consolido-Polygonetum avicularis. Considering the coefficients of nectar and pollen production, the most valuable honey plants commonly present in the majority of communities were: Cirsium arvense, Rubus caesius, Lythrum salicaria, Daucus carota, Trifolium pratense, Dipsacus laciniatus, Medicago sativa, Asclepias syriaca, Cichorium intybus and Taraxacum officinale. The low abundance and frequency of melliferous species within the Consolido-Polygonetum avicularis, Polygonetum convolvulo-avicularis and Populetum nigrae-albae communities indicated their poor contribution to the bee pasture. Within ruderal vegetation, the highest CCm was registered in Amorpho-Typhaetum, providing, theoretically, the richest food resource for the honeybees in the investigated area.

Glacial legacy effects on river landforms of the southern Laurentian Great Lakes

Abstract Stream and river drainage networks are fundamental in watershed science, but the low-relief river catchments of the southern Laurentian Great Lakes do not easily conform with traditional ideas in fluvial geomorphology. The effects of Pleistocene glaciation and post-glacial isostatic rebound require an adapted fluvial landscape model in order to understand the organization of river landforms. Advancing our understanding of glacial legacy effects in low-relief river catchments is important for the effective management of aquatic ecosystems and water resources in these environments. Based on a classification framework for alluvial floodplains, the spatial arrangements of river landforms are presented for three catchments in southern Ontario, Canada. The typical Holocene response of southern Ontario rivers is confounded by numerous distinct glacial landform assemblages and dynamic baselevel histories. Mapping of river landforms provides an interpretive framework to explain glacial legacy effects in the context of local sources of glacial sediment and patterns of fluvial sediment flux over the Holocene. A number of general glacial–fluvial landform relationships are identified and can be broadly clustered into three themes: 1) topographic and sedimentological glacial legacy effects; 2) landforms resulting from isostatic and lake baselevel change, and 3) superimposed patterns of Holocene fluvial sediment supply. Geochronological evidence is assessed for floodplain landform ages, but radiocarbon methods are limited in many floodplain types due to slow vertical accretion processes. Laterally active meandering channels with well-developed point-bar deposits tend to rework the alluvium every few centuries in smaller channels and every few millennium in larger channels.