Sparganium Erectum Research Articles

Twenty years of change in riverside vegetation: what role have invasive alien plants played?

AbstractQuestionWhich environmental factors influence the occurrence of invasive alien plants (IAPs) in riparian habitats, and how much can IAPs account for change in native vegetation compared with other environmental variables?LocationRivers distributed throughout mainland Britain.MethodsWe quantified change in river bank vegetation using survey data collected approximately 20 yr apart and assessed the contribution of major IAPs (Impatiens glandulifera, Heracleum mantegazzianum and Fallopia japonica) to these changes. We also determined the importance of abiotic factors such as flow regime and land use in driving these changes.ResultsComparing data from pre‐ and post‐1990 surveys revealed that IAPs occurred mainly on lowland rivers (<200 m a.s.l.), regardless of time period, and their probability of occurrence increased over time and with rising frequency of high flows. Native plant species diversity declined over time with increasing IAP cover, along lowland rivers and along all rivers that experienced extended low flows during the growing season. These conditions particularly favoured native dominant species, whereas native subordinate species responded both positively and negatively to increased flood frequency depending on survey period. Over time, Salix spp. and larger native hydrophilic species, such as Sparganium erectum, increased along lowland rivers, replacing smaller‐statured ruderal species and driving a shift towards increased shade tolerance of subcanopy and groundcover species. Smaller compositional changes occurred in the uplands and these changes lacked a clear environmental signature.ConclusionsNational‐scale changes in native riparian vegetation are likely driven primarily by environmental changes and land‐use effects, rather than invasion by IAPs. However, IAPs, and indeed native species that benefit from abiotic changes, in turn, likely exert secondary effects on native riparian vegetation. The trend towards reduced diversity, increased shade tolerance and increased dominance of some native species and IAPs is likely linked to a set of interacting factors, including drier summers, wetter winters, increased riparian tree cover, reduced livestock access to river banks and increased fine sediment input. Determining combined effects of land use, IAPs and climate‐related changes in flow regime over decadal time scales (i.e. ~20 yr) is important for predicting ecological responses of vulnerable habitats under future disturbance scenarios.

Assessment of the Efficiency of a Pilot Constructed Wetland on the Remediation of Water Quality; Case Study of Litani River, Lebanon

The potential use of constructed wetlands to remediate polluted rivers is promising and has recently received a great deal of interest. This study aims at evaluatingthe efficiency of a constructed wetland of the Litani River in Lebanon using two types of aquatic plants, Phragmites australis and Sparganium erectum. Comparative analysis of the mean values of water quality parameters of the inflow and outflow water of the wetland system was conducted during the period of April 2014 and July 2015. Findings show statistically significant improvement in water quality parameters. Hence, results clearly show the efficiency of the constructed wetland in the remediation of the polluted river water and the important role of the aquatic macrophytes in remediation. In conclusion, the studied wetland provides an efficient sustainable approach towards the integrated river basin management of Litani River. Further comprehensive studies to better illustrate the role of aquatic plants in the remediation process are needed.

Why do reed beds decline and fail to re‐establish? A case study of Dutch peat lakes

Summary The decline in emergent reed beds in eutrophic shallow lakes in Europe has been linked to multiple factors, such as adverse water and sediment quality, shoreline development and fixed water level preventing recolonisation, recreational disturbances and herbivory by geese and muskrat. This study analyses the relative importance of these factors in a historical context and tests experimentally what currently may prevent the re‐establishment of emergent reed beds. We examined the historical extent of emergent reed stands (1925–2013) in relation to long‐term time series of lakeside housing development (1920–2013), abundance of greylag geese (Anser anser) and muskrat (Ondatra zibethicus) as well as water quality (1977–2013) for the shallow lowland peat lake district of Reeuwijk in The Netherlands. In addition, we carried out a comparative survey to generalise our results and an exclosure experiment to test whether current muskrat grazing pressure may hamper restoration efforts. A steady, linear decline in the extent of emergent reed beds over time corresponded significantly with a similar increase in lakeside house density. We found no correlation with herbivore stocks or water quality parameters. In the exclosures, rapid expansion of common reed (Phragmites australis), branched bur‐reed (Sparganium erectum) and submerged pondweeds (Potamogeton spp.) occurred, suggesting muskrat herbivory as a factor‐limiting emergent reed re‐establishment in the foreshore. A combined understanding of the different roles of slow, long‐term pressures (such as housing development) and present constraints (the continuous grazing pressure by muskrat despite a culling program) is crucial to the successful restoration of reed beds in shallow lakes.

Macrophytes as bioindicators of the physicochemical characteristics of wetlands in lowland and mountain regions of the central Balkan Peninsula

The simultaneous monitoring of vegetation, water and sediments was conducted in wetlands of the central Balkan Peninsula due to the lack of available knowledge on the univariate response of macrophytes along environmental gradients. The environmental preferences and bioindicator potential of macrophytes were assessed using Huisman-Olff-Fresco (HOF) models. Bolboschoenus maritimus and Scirpus lacustris subsp. tabernaemontani are valuable bioindicators of slightly saline (electroconductivity of 2000–4000μScm−1 in the sediment) and alkaline habitats that are rich in SO42−. Their ecological niches are partially overlapped. Bolboschoenus maritimus prefers saltier and more alkaline habitats for optimal development. The salinity and alkalinity of habitats are decisive factors in the ecological diversification of the Boloboschoenus species. Bolboschoenus glaucus is adapted to non-saline (400–900μScm−1) and slightly alkaline habitats, unlike Bolboschoenus maritimus. Relatively deep, slightly acid waters which are poor in SO42− (0.30mg/l), and sediments with low values of electroconductivity and K2O (6.8mg/100g sediment) are preferred by Typha angustifolia, Sparganium erectum and Typha latifolia. The abundance of Phalaris arundinacea, Scirpus lacustris, Carex riparia and Eleocharis palustris increases when there is a decrease in the amount of nutrients (NH4+, PO43− and SO42−) in the water. Phragmites australis has low indicative value and regional bioindicator potential. The data obtained in the study may serve as a basis for adjusting the existing indicator values of these species and extending indicator systems by defining the indicator values of species with respect to environmental variables which have not yet been considered.

ACCUMULATION OF CHEMICAL ELEMENTS BY ORGANS OF SPARGANIUM ERECTUM L. AND THEIR POTENTIAL USE IN PHYTOREMEDIATION PROCESS

The study of bottom sediments and organs of Sparganium erectum carried out in the summer of 2014 in the city of Lebork, located in Northern Poland. The aim of this study was to evaluate the content of macroelements and heavy metals in the leaves, rhizomes and roots S. erectum and in bottom sediments of the Łeba River as well as comparison of accumulation and translocation factors of N, P, K, Mg, Ca, Zn, Ni, Cu, Mn, Fe, Cd and Cr in researched organs of aquatic plant. The use of S. erectum for biomonitoring and phytoremediation has also been considered. The results of Mann Whitney U test showed a number of statistically significant differences in the content of chemical elements in the leaves, rhizomes, roots and in bottom sediments. The macroelements are mainly accumulated in leaves and heavy metals are accumulated in roots and rhizomes of S. erectum. Increased Mn and Fe content in roots and rhizomes of S. erectum, in relation this physiological needs, refers to the beneficial effects of this species in the water treatment and sludge from the bottom sediment of manganese and iron compounds. The obtained bioconcentration and translocation factors values allowed to state that S. erectum can be used for phytoremediation of contaminated bottom sediments because retains metals in their roots and limit Mn and Fe mobility from roots and rhizomes to leaves once absorbed by roots of plant.

Modular and structural–functional organization of G. sparganium L. species in different ecological conditions

The structure of monocarpic shoots of some representatives of the Sparganiaceae family (Sparganium emersum Rehm., Sparganium natans L. (subgenus Xanthosparganium), Sparganium erectum L. and Sparganium microcarpum (Neum.) Domin (subgenus Melanosparganium)) has been analyzed with the help of the modular approach. The structure of all three module categories—elementary (EM), universal (UM), and basic (BM)—is described. With a decrease in EM value, all investigated species line up in the following descending order: S. emersum (23) > S. erectum (20) > S. natans (19) > S. microcarpum (18). It is determined that the level of EM similarity between two bur-reed subgenera reaches 30%. The rest of the EM part is specific for certain subgenera, as well as for certain species. It is shown that dissimilarities between different ecological forms of Sparganium are due not to a quantitative EM increase, but to their transformation ability, which improves species adaptation to varying water-level conditions of reservoirs. The UM value in the representatives of both subgenera equals 4; BM values are represented by two similar variants. This was caused by the similarity of habitats of the model species. The special features of the plants on the level of structural–functional organization of different types of monocarpic shoots are shown. Differences in the set of structural–functional zones for particular shoot types were also revealed.

Trace metal concentrations and their transfer from sediment to leaves of four common aquatic macrophytes.

In the present study, the concentrations of trace and alkali metals in leaves of four common helophytes, Sparganium erectum, Glyceria maxima, Phalaris arundinacea, and Phragmites australis, as well as in corresponding water and bottom sediments were investigated to ascertain plant bioaccumulation ability. Results showed that Mn and Fe were the most abundant trace metals in all plant species, while Co and Pb contents were the lowest. Leaves of species studied differed significantly in respect of element concentrations. The highest concentrations of Mg, Na, Fe, Mn, Cu, Pb, and Ni were noted in S. erectum while the highest contents of Co, Ca, Zn, and Cr in Phalaris arundinacea. Phragmites australis contained the lowest amounts of most elements. Concentrations of Co, Cr, Fe, and Mn in all species studied and Ni in all except for Phragmites australis were higher than natural for hydrophytes. The leaves/sediment ratio was more than unity for all alkali metals as well as for Cu and Mn in Phragmites australis; Cr, Co, and Zn in Phalaris arundinacea; Cr and Mn in S. erectum; and Cr in G. maxima. High enrichment factors and high levels of toxic metals in the species studied indicated a special ability of these plants to absorb and store certain non-essential metals and, consequently, their potential for phytoremediation of contaminated aquatic ecosystems.

Macrophyte biometric features as an indicator of the trophic status of small water bodies

Abstract The aim of the study was to determine whether biometric features of plants collected from single-species phytocoenoses developing in ponds can be used to describe habitat conditions of these water bodies. The biometric measurements were carried out in 148 field small water bodies at a total of 198 sites. The length of plants, their dry biomass, and volume of plant shoots were analyzed, converted to 1000 dm3 of water. The biometric measurements showed very large differences in individual parameters of different macrophyte species. The biggest differences were found in the length of elodeids and helophytes (from 1 cm to > 900 cm), regardless of trophic conditions. Although the Polish flora is dominated by plants having a wide ecological range, there are species whose parameters correspond to specific habitat fertility. The highest biometric parameters were found for Ceratophyllum submersum, Sparganium erectum, Typha latifolia and Schoenoplectus lacustris in ponds characterized by increased trophic conditions. In contrast, Myriophyllum spp. alone showed a negative correlation with trophic state indices. The trophic effect on the studied parameters becomes more apparent for species with optima in fertile water bodies. The parameters of Ceratophyllum submersum can be considered as the trophic state index (TSI).

Fruit germination of some representatives of the family Sparganiaceae Rudolphi under laboratory conditions

This paper considers fruit germination patterns in representatives of the family Sparganiaceae, which are most widespread in the European part of Russia: Sparganium emersum Rehm. (subgenus Xanthosparganium), Sparganium erectum L., and Sparganium microcarum (Neum.) Raunk. (subgenus Melanosparganium). It is shown that, after dissemination, fruits of all studied species do not germinate immediately, either intact or after different presowing treatment (scarification). It is found that under laboratory conditions a long period of moist cold stratification positively affects the germination ability of S. emersum and S. microcarpum fruits, as opposed to fruits of S. erectum. In all other experiments, fruits of S. microscarpum do not germinate or germinate sporadically. Fruits of S. erectum do not germinate, regardless of the different conditions of storage and presowing treatment. Long-term dry storage of S. emersum fruits under room conditions leads to a decrease in laboratory germination ability, and only the subsequent stratification of the fruit makes it possible to significantly increase this characteristic.

Nutrient Retention Associated with Phenological Features in Sparganium Erectum Stands in a Lowland Stream

AbstractIn a previous study, we found that Sparganium erectum, an emergent macrophyte, accumulates sediment inside the stand because of its phenological features. Because this species usually grows in a nutrient‐rich environment, we hypothesize that a high trophic level is maintained in the accumulated sediment. To test this hypothesis, we intensively studied flow velocity, nutrient budget and nutrient flux in and outside of S. erectum stands along the Moto‐Arakawa River, Saitama, Japan and found that the growth stages of S. erectum substantially affected the flow conditions inside the stand. The growth stages of this plant also controlled the depositional rate of sediment and organic particles. After the collapse of each cohort, a substantial amount of organic matter accumulated on the stand bed. Because the accumulated organic matter mineralized very fast, the concentration of total carbon (TC), total nitrogen (TN) and total phosphorus (TP) increased substantially after the collapse of the shoots. While the concentrations of TC, TN and TP within the stand's sediment varied seasonally, the concentrations of these elements were always higher inside than outside of the stand. More than five times the amount of carbon and twice the amount of nitrogen and phosphorus were physically retained in the stand for 1 year compared with the amounts assimilated by the plants. The ratio of carbon to nitrogen in the stand's sediment also remained constant throughout the growing period. Conversely, the nitrogen to phosphorus ratio of the accumulated sediment was much lower than that of other plant tissues. The main flow contains suspended organic solids that constantly supply the stand and partially occupy the channel where they eventually settle. Copyright © 2014 John Wiley & Sons, Ltd.

The geomorphological context and impact of the linear emergent macrophyte, Sparganium erectum L.: a statistical analysis of observations from British rivers

ABSTRACTThis paper explores the geomorphological context and impact of the widely‐occurring, linear emergent macrophyte, Sparganium erectum.Forty‐seven sites across Britain were selected for field investigation, spanning the range of environmental conditions within which Sparganium erectum had been found to be present in previous analyses of national data sets. A combination of descriptive graphs and statistics, principal components analysis, and Kruskal–Wallis tests were used to explore the large multivariate data set collected at the 47 sites.The analyses showed that Sparganium erectum is present in significant quantities in relatively narrow and shallow (< 18 m wide and < 0.9 m deep to the limit of terrestrial vegetation), low gradient (maximum 0.004) channels of varying bed sediment calibre (cobble to silt). Within these environments, S. erectum stands (features) were associated with fine sediment retention, aggradation and submerged landform construction, leading to bench development and so, potentially, to adjustments in channel form and position. Sediment retention and landform construction within S. erectum features was most strongly apparent within reaches with a relatively high S. erectum cover and the presence of large area S. erectum features. It was also associated more weakly with S. erectum features that were comprised of relatively higher densities of plants with relatively smaller inter‐plant spacing and fewer leaves. The sediment retained in S. erectum features and associated bench and bank toe deposits showed larger numbers and species of viable seeds, indicating the potential for colonization and growth of other species on S. erectum features once they aggrade above the low flow water level and are no longer a suitable habitat for S. erectum. Copyright © 2013 John Wiley & Sons, Ltd.

남한강 일대의 관속식물상

This study was carried out to investigate the vascular plants of Namhan River. The period of survey was from March to November on 2012. Vascular plants based on voucher specimen were summarized as 430 taxa including 86 families, 250 genera, 383 species, 2 subspecies, 39 varieties and 6 forms. The rare plant species designated by Korea Forest Service were 13 taxa including Penthorum chinense Pursh, Polygonatum stenophyllum Maxim, and Sparganium erectum L., etc. And the endemic plant species were 8 taxa including Salix koriyanagi Kimura, Clematis trichotoma Nakai, and Carex gifuensis Franch., etc. Furthermore, 56 taxa were listed as specific plant species based on phytogeographical and based on the list of plants which have been approved for overseas delivery, 27 taxa were recorded in the investigated area. The naturalized plants were recorded as 58 taxa, and their Naturalization Ratio and Urbanization Index were recorded as 13.5%, and 18.1%, respectively. 430 taxa listed consists of 174 taxa(40.5%) of pasturing plant, 141 taxa(32.8%) of edible plants, 112 taxa(26.0%) of medicinal plants, 48 taxa(11.2%) of ornamental plants, 11 taxa(2.6%) of stain plants, 7 taxa(1.6%) of fiber plants, 4 taxa(0.9%) of timber plants, 2 taxa(0.5%) of industrial plants and 109 taxa(25.4%) of unknown plants.

Profiling the below ground biomass of an emergent macrophyte using an adapted ingrowth core method

In the context of our work exploring the role of Sparganium erectum as a physical ecosystem engineer, we aimed to test our hypothesis that the root and rhizome biomass of this species would be largely confined to the uppermost sediment layers, thereby having the effect of reinforcing newly deposited material and facilitating the growth of in-channel macrophyte stands and sediment accumulations. Detailed measurements of the below ground structures of linear emergent macrophytes, in terms of their biomass and architecture, are complicated by difficulties associated with sampling in the highly saturated sediments that these morphotypes typically occupy. In this paper, we describe the development of an adapted ingrowth core method, which allows the extrusion of an undisturbed root-soil matrix from highly saturated environments. The approach combines an ingrowth core, which is commonly used to measure fine-root production in forest topsoil, with an outer casing that facilitates the retention of a sample representative of field conditions, and a laboratory protocol that enables extrusion and measurement of biomass at different depth increments. The new approach enabled detailed depth profiling of S. erectum, and confirmed our hypothesis by demonstrating that root and rhizome biomass was predominantly located in the 10cm of sediment closest to the sediment–water interface throughout our study.

Associations between the morphology and biomechanical properties of Sparganium erectum: Implications for survival and ecosystem engineering

Aquatic plants are able to alter their morphology under stressful hydrodynamic conditions to improve survival and growth; adjustments can include increases in below ground ‘anchoring’ biomass, or escape strategies such as extending the internodal length of rhizomes. Whilst research has demonstrated how macrophytes respond morphologically to stressful hydraulic conditions, there is little evidence of how these changes, particularly in below ground size and structure, influence the forces required to damage and dislodge aquatic plants. The aim of our study was to further establish the links between mechanical force (i.e. the forces required to uproot plants or cause stem breakage) and plant morphology in the common and widely distributed emergent species Sparganium erectum. Mechanical force was applied using a pulling device that consisted of a winch mounted on a metal frame that sat on the river bank, and from which a cable, with attached load cell, was connected to the stem of a S. erectum plant. We found strong associations between the below ground structures of the plant and the force at which it experiences failure. Below ground plant organs were important in determining the overall resilience of this species, with root length showing the strongest association with its ability to resist uprooting, whilst rhizomes had the longest seasonal influence on the force required to uproot the plant. Biomass measurements of below ground organs revealed rapid increases in root biomass early in the season, in contrast to the rhizome and corm biomass, which peaked at the end of the growth season. We argue that these results are demonstrative of a number of biomechanical and morphological traits that contribute to the pervasiveness of the species, its management challenges, and its function as an ecosystem engineer, whereby it alters the physical structure of river channels by deflecting flow and building large sediment accumulations. These traits include the presence of a mechanical fuse, rapid growth of roots early in the season and reproductive structures at the end of the season, which probably have a reinforcing effect on the surrounding sediment, and the high resistance of the species to uprooting, stem and rhizome breakage.

A new species of Bipolaris from Iran

Bipolaris salkadehensis sp. nov., isolated from the leaves of Sparganium erectum (Thyphaceae) and Cladium mariscus (Cyperaceae) collected in Iran, is described and illustrated. The new species is characterized by straight to slightly curved subcylindrical to fusoid conidia with end cells demarcated by thick dark septa and with monopolar and bipolar germination. Morphological data and ITS+5.8SrDNA sequence analyses support B. salkadehensis as a distinct species of Bipolaris.

Effects of environmental factors on <i>Sparganium emersum</i> and <i>Sparganium erectum</i> colonization in two drainage ditches with different maintenance

In the Niheishimizu and Ooshimizu sections of the town of Misato in the Akita Prefecture, Northern Japan, there are many abundant spring water areas. Sparganium (Sparganium emersum and Sparganium erectum) species are widely distributed in the irrigation water that fed by spring water. The irrigation waters were divided the natural type ditch and the maintained ditch that connect with nearby natural ditch to promote environmentally friendly agriculture. This study was conducted in both sections to support the maintenance of the irrigation water fed by the abundant spring water. A vegetation survey was conducted in September of 2005. The survey collected data on the amount of vegetation cover and the stem lengths of the plant species found in selected locations of the study area. The water depths and the flow velocities were also measured in these locations. As for the growth situation of S. emersum and S. erectum, the submerged form of S. emersum was found in water approximately 15 cm deep with a surface flow velocity of approximately 7 cm/s. This species was characterised by a relatively fast flow and relatively shallow water. The emergent and submerged growth forms of S. emersum were found in waters having flow velocities faster than those associated with S. erectum. The emergent form of S. emersum grew in relatively deep water. S. emersum is more capable of adjusting to the conditions of stream habitats than S. erectum.

Influence of an ecosystem engineer, the emergent macrophyte Sparganium erectum, on seed trapping in lowland rivers and consequences for landform colonisation

Summary1. Plant physical ecosystem engineers can influence vegetation population and community dynamics by modifying, maintaining or creating habitats. They may also have the potential to act upon biotic processes, such as seed dispersal.2. Examples exist of reduction in seed dispersal distances in vegetated compared to unvegetated terrestrial environments, and concentration of seed deposits associated with plant patches. Such effects in aquatic environments have been little studied, but the engineering effect of plant patches on patterns of flow velocity and sediment deposition in streams suggests that they may play a similar role.3. In this study, we assess the potential of an emergent aquatic species, Sparganium erectum, to play a role in physically modifying river habitats and trapping seeds by examining patterns of seed deposition and substrate type in 47 river reaches across England and southern Scotland, U.K.4. Areas of the river channel within or adjacent to S. erectum patches harboured more plant seeds and more species than unvegetated areas and had finer, sandier substrates with higher organic matter, total nitrogen and total phosphorus content. Most seed species were competitive, indicating that they were well suited to colonise the competitive environment of an S. erectum patch, and could potentially further stabilise accumulated sediments and contribute to landform development.5. We demonstrate that S. erectum patches influence both the physical environment and the retention of seeds, in consistent patterns across the channel bed, for a range of lowland rivers that vary in stream power and geology and which can be expected to vary in levels of supply of fine sediment and seeds.6. Our findings support the hypothesis that the fundamental influence of a riverine ecosystem‐engineering species on slowing fluid flow links the habitat creation process of sediment sorting and retention to seed trapping. We suggest the process is applicable to a wide range of aquatic and riparian vegetation. We also suggest that the mono‐specific and competitive growth, which is typical of these engineering species, will strongly influence the recruitment of trapped seeds.

Quantifying the potential for flow to remove the emergent aquatic macrophyte Sparganium erectum from the margins of low-energy rivers

The emergent macrophyte species Sparganium erectum occurs commonly at the margins of low- to medium- energy river systems across the northern temperate zone. It is considered as an invasive species along low-energy water courses in many parts of the US and Australia. The life-cycle and biomechanical properties of this species make it very well adapted to such environments, allowing rapid growth and sediment trapping, such that encroachment into the channel occurs as the growing season progresses. The widespread growth of species such as S. erectum is therefore of particular concern, when considering the flood risk potential of many rivers. As such, the conditions required for survival or uprooting and scouring of this plant are of interest, as are the times of the year and processes by which these plants spread to increase the size of current stands, and to form new stands. It is known that S. erectum reproduces by several vegetative methods including rhizome growth, dispersal of detached rhizomes, and relocation of entire plants. However, the mechanisms and flow conditions necessary for uprooting or scouring of entire plants, and the separation of fragments of this species, at different times of the year, are largely unknown. The aim of this paper is to model the uprooting resistance of S. erectum plants as reported by Liffen et al. (in press), and to investigate the manner by which this species is adapted to proliferate in low-energy, low-gradient streams. The results presented here show that Monte Carlo simulations using the RipRoot root-reinforcement model can be used to accurately model plant pullout forces, rhizome interconnectivity and length changes for S. erectum plants throughout the growing season. Analysis presented here also suggests that plant uprooting forces are several orders of magnitude larger than potential drag forces that could act on the S. erectum plants at the River Blackwater site modeled, and even at sites with much higher channel slopes. This result suggests that the ability of these plants to thrive in low-energy rivers, but not in higher-energy river environments, is less related to driving forces causing drag on the plants, and more related to the energy conditions controlling erosion and deposition of the fine substrate materials these plants thrive in. The critical shear stress of the fine within-vegetation material was shown here to only be exceeded by the average boundary shear stress within the vegetation, during winter months when above-ground biomass and thus Manning's n values were at their lowest. For example, during March and April average boundary shear stress was predicted to exceed critical boundary shear stress for 6% of the time. Erodibility measurements from jet-tests conducted at the River Blackwater fieldsite suggested that this excess in boundary shear stress could result in potential vertical scour of up to 0.09 m in both March and April. During the majority of the growing season sediment trapping rather than erosion dominated, with enough deposition occurring over the summer to protect all but the shallowest, weakest and least interconnected rhizomes and plants from being scoured in the winter months. The balance between erosion and deposition within stands of S. erectum in these low-energy environments therefore allows for the maintenance of established stands of vegetation, whilst still allowing for scouring of weaker S. erectum plants that can establish previously un-colonized channel margins further downstream.

Biomechanical properties of the emergent aquatic macrophyte Sparganium erectum: Implications for fine sediment retention in low energy rivers

This paper is concerned with the biomechanical properties of the emergent aquatic macrophyte, Sparganium erectum. We present observations of adjustments in the physical characteristics and biomechanical properties of S. erectum during the growing season (April–November) from the River Blackwater, UK. When a pulling device is attached to plant stems to measure their resistance to uprooting, individual plants show remarkable strength in their above- and below-ground biomass (median stem strength when stems break away from the underground biomass, 78 N, median rhizome strength, 39 N) and high resistance to uprooting (median uprooting resistance when entire plants uproot, 114 N). This provides the potential for the species to protect and reinforce the generally soft, silty sediments that it often retains and within which its rhizomes and roots develop in lower energy river environments. There is a propensity for plant stems to break before the plant is uprooted at the beginning and end of the growth season, but for the stems to have sufficient strength in mid season for plant uprooting to dominate. This ensures that rhizome and root systems remain relatively undisturbed at times when the silty sediments in which they grow are poorly protected by above-ground biomass. In contrast, rhizome strength remains comparatively invariant through the growing season, supporting the plant's potential to have a protective/reinforcing effect on fine sediments through the winter when above ground biomass is absent.

Suitability of Monocots for Rearing Alien Coconut Pest Brontispa longissima (Coleoptera: Chrysomelidae)

Abstract The suitability for larval development of the alien coconut pest Brontispa longissima (Gestro) (Coleoptera: Chrysomelidae) on the following 15 monocots was investigated. Arecaceae: Cocos nucifera, Trachycarpus wagnerianus; Typhaceae: Sparganium erectum, Typha latifolia; Poaceae: Avena sativa, Echinochloa esculenta, Hordeum vulgare, Oryza sativa, Sorghum bicolor, Zea mays; and Cyperaceae: Carex morrowii, Cyperus alternifolius, Cyperus esculentus, Cyperus serotinus, and Rhynchospora colorata. The larval survival rate to the adult stage was significantly higher when reared on C. esculentus and C. serotinus (95%); however, it was not significantly different compared with C. nucifera (75%). Sixty, 45, 45, and 10% were observed when reared on T. wagnerianus, S. erectum, T. latifolia, and C. alternifolius, respectively. The larval developmental period reared on C. serotinus was as short as on C. esculentus and on C. nucifera up to adult emergence. The fecundity of adults was examined using C. nucifera, T. wagnerianus, T. latifolia, C. esculentus, and C. serotinus as food plants. In these five plants, the females reared on T. wagnerianus started to lay eggs earliest. However, the preoviposition periods on C. esculentus and C. serotinus were not significantly different from those on C. nucifera and T. latifolia. Numbers of eggs laid per female did not differ significantly among these five plants. Our present results suggest that T. wagnerianus, C. esculentus, and C. serotinus can be used as new food plants in addition to C. nucifera and T. latifolia for rearing B. longissima.