			Home About us Contact

Invertebrate Assemblages (invertebrate + assemblage)

Distribution by Scientific Domains

Life Sciences	86%

Distribution within Life Sciences

Ecology & Organismal Biology	75%
Conservation Science	9%
3 Other Subdomains	16%

Selected Abstracts

Differences in leaf-litter invertebrate assemblages between radiata pine plantations and neighbouring native eucalypt woodland

AUSTRAL ECOLOGY, Issue 4 2009
TESSA C. ROBSON
Abstract We investigated the structure, composition and environmental correlates of leaf-litter invertebrate assemblages in Pinus radiata plantations and in neighbouring native eucalypt woodland in the Jenolan Caves Karst Conservation Reserve, south-east Australia. Invertebrate assemblages of plantations were compared with remnant eucalypt woodland located well away from the influence of plantations to determine the direct effects of plantations as a result of habitat-replacement with a non-native plantation species. We also included in our comparisons edge habitat of eucalypt woodland located immediately adjacent to plantations. This unique edge habitat is exposed to the intrusion of large volumes of pine leaf-litter from plantations, which has the potential to affect indirectly invertebrate assemblages of surrounding woodland. We found that species richness of invertebrates was significantly lower in pine plantations compared with remnant eucalypt woodland. There was a complete absence of species from 12 invertebrate orders that were found in surrounding eucalypt woodland. A rich and abundant native plant understorey that provides increased habitat heterogeneity is the most likely explanation for the richer invertebrate assemblage found in remnant eucalypt woodland. The total abundance of all invertebrate taxa in pine plantations in winter was significantly higher than in remnant eucalypt woodland, pine-litter edges and pine-free edges. Plantations were characterized by particularly high abundances of species in two orders, Acari and Collembola. High abundances of acarine and collembolan species in plantations were associated with a decompositional environment represented by comparatively higher moisture contents and higher C : N ratios of both leaf-litter and soil, higher soil conductivity and lower soil pH. We suggest that implementation of The Plantation Biodiversity Benefits Score will be a fruitful way forward to assess the environmental benefits that can be gained from pine plantations in this region of south-eastern Australia. [source]

Grassland invertebrate assemblages in managed landscapes: Effect of host plant and microhabitat architecture

AUSTRAL ECOLOGY, Issue 6 2007
ADELE M. REID
Abstract Grasslands are often considered as two-dimensional habitats rather than complex, multilayered habitats. However, native grasslands are complex habitats, with multiple layers of annual and perennial grasses, sedges, shrubs and mosses. Vegetation complexity, including plant type, quality and three-dimensional structure is important for providing a variety of food and habitat resources for insects. Grazing by domestic livestock can affect these processes through the loss or fragmentation of habitats, as well as altering the vertical and horizontal vegetation structure. This study aimed to investigate the role of host plants and microhabitat architecture for determining foliage invertebrate assemblages. Different plant species supported distinct invertebrate assemblages and less complex host plants supported fewer invertebrate individuals and species. Manipulations of plant architecture changed the species composition of invertebrates, with most species found in more complex vegetation. This study illustrates the importance of host diversity and pasture complexity for invertebrate communities. Management practices that encourage a heterogeneous environment with diverse and structurally complex pastures should also sustain a more diverse and functional invertebrate assemblage. [source]

Spatial autocorrelation of assemblages of benthic invertebrates and its relationship to environmental factors in two upland rivers in southeastern Australia

DIVERSITY AND DISTRIBUTIONS, Issue 5 2005
Natalie J. Lloyd
ABSTRACT The nature of spatial autocorrelation of biota may reveal much about underlying ecological and biological factors responsible for producing those patterns, especially dispersal processes (drift, adult flight, etc.). We report here on assemblage-level autocorrelation in the benthic-invertebrate assemblages (retained in sieves of 300 µm mesh) of riffles in two adjacent, relatively pristine rivers in southeastern Victoria, Australia (40-km reaches of the Wellington and Wonnangatta Rivers). These are related to patterns of autocorrelation in physical and catchment conditions (,environmental variables') in the vicinity of the sampling points. Both the invertebrate assemblages and environmental variables were autocorrelated at small scales (= 8 km) in the Wellington River in one of the sampling years (1996). Dissimilarities of invertebrate assemblages were correlated with dissimilarities of environmental variables in both sampling years (1996 and 1997) in that river. Environmental variables were autocorrelated in the Wonnangatta River, but this was not expressed as autocorrelation in the assemblages of invertebrates, which were not autocorrelated at any scale studied. Individual environmental variables showed different spatial patterns between the two rivers. These results suggest that individual rivers have their own idiosyncratic patterns and one cannot assume that even similar, geographically adjacent rivers will have the same patterns, which is a difficulty for ecological assessment and restoration. [source]

Is structure or function a better measure of the effects of water abstraction on ecosystem integrity?

FRESHWATER BIOLOGY, Issue 10 2009
RUSSELL G. DEATH
Summary 1. Assessments of flow abstractions in streams often focus on changes to biological communities and in-stream physical characteristics, with little consideration for changes in ecosystem functioning. It is unclear whether functional indicators of ecosystem health may be useful for assessing the impacts of reduced discharge on small streams. 2. We used weirs and diversions to reduce stream discharge by over 89% in three small New Zealand streams (11,84 L s,1), ranging in water quality from pristine to moderately impaired. 3. We used both structural (benthic invertebrates) and functional (drifting invertebrates, leaf breakdown, coarse particulate organic matter (CPOM) retention and primary productivity) measures of ecosystem integrity to compare responses to water abstraction in before-after, control-impact designed experiments during summer 2005. 4. At the pristine site, the density of invertebrates, taxon richness, Macroinvertebrate Community Index (MCI), Quantitative MCI, percentage of Ephemeroptera, Plecoptera and Trichoptera individuals and percentage of filter-feeders decreased in response to reduced flows. Only taxon richness decreased at the mildly impaired stream, and reduced discharge had no effect on the invertebrate community at the stream with the lowest water quality. 5. We found that reduced discharge had little influence on the breakdown rate of willow leaves in mesh bags over 1 month. Primary productivity was also relatively insensitive to water abstraction. However, CPOM retention increased with decreased flows. Drift propensity of invertebrates increased at two sites but only within the first few days after flow reduction. 6. Structural measures of ecosystem integrity suggested that the impacts of water abstraction differed among streams of varying water quality, probably because of differences in the sensitivity of invertebrate assemblages in the three streams. In contrast, the three functional measures tested were generally less sensitive to water abstraction impacts, although understanding how stream ecosystems respond to water abstraction clearly requires that both are considered. [source]

Trends in water quality and discharge confound long-term warming effects on river macroinvertebrates

FRESHWATER BIOLOGY, Issue 2 2009
ISABELLE DURANCE
Summary 1.,Climate-change effects on rivers and streams might interact with other pressures, such as pollution, but long-term investigations are scarce. We assessed trends among macroinvertebrates in 50 southern English streams in relation to temperature, discharge and water quality over 18 years (1989,2007). 2.,Long-term records, coupled with estimates from inter-site calibrations of 3,4 years, showed that mean stream temperatures in the study area had increased by 2.1,2.9 °C in winter and 1.1,1.5 °C in summer over the 26 year period from 1980 to 2006, with trends in winter strongest. 3.,While invertebrate assemblages in surface-fed streams were constant, those in chalk-streams changed significantly during 1989,2007. Invertebrate trends correlated significantly with temperature, but effects were spurious because (i) assemblages gained taxa typical of faster flow or well-oxygenated conditions, contrary to expectations from warming; (ii) more invertebrate families increased in abundance than declined and (iii) concomitant changes in water quality (e.g. declining orthophosphate, ammonia and biochemical oxygen demand), or at some sites changes in discharge, explained more variation in invertebrate abundance and composition than did temperature. 4.,These patterns were reconfirmed in both group- and site-specific analyses. 5.,We conclude that recent winter-biased warming in southern English chalk-streams has been insufficient to affect invertebrates negatively over a period of improving water quality. This implies that positive management can minimize some climate-change impacts on stream ecosystems. Chalk-stream invertebrates are sensitive, nevertheless, to variations in discharge, and detectable changes could occur if climate change alters flow pattern. 6.,Because climatic trends now characterize many inter-annual time-series, we caution other investigators to examine whether putative effects on ecological systems are real or linked spuriously to other causes of change. [source]

Food webs in tropical Australian streams: shredders are not scarce

FRESHWATER BIOLOGY, Issue 5 2005
KIM CHESHIRE
Summary 1. Macroinvertebrates were collected in dry and wet seasons from riffles and pools in two streams in tropical north Queensland. Total biomass, abundance and species richness were higher in riffles than in pools but did not differ between streams or seasons. 2. Gut contents of all species were identified. Cluster analysis based on gut contents identified five dietary groups: I, generalist collectors; II, generalist shredders and generalist predators; III, generalist scrapers; IV, specialist shredders; and V, specialist predators. Species were allocated to functional feeding groups (FFGs) based on these dietary groups. 3. Many species were generalist in their diets, but specialist predators and shredders were particularly prominent components of the invertebrate assemblages in terms of biomass and species richness. 4. Community composition (proportions of biomass, abundance and species richness of the different FFGs) varied between habitat types, but not between streams or seasons, although differences between riffles and pools varied with season. 5. Comparison of the fauna of 20 streams showed that our study sites were similar to, or not atypical of, low-order streams in the Queensland wet tropics. [source]

The influence of stream invertebrate composition at neighbouring sites on local assemblage composition

FRESHWATER BIOLOGY, Issue 2 2005
R. A. SANDERSON
Summary 1. The composition of freshwater invertebrate assemblages at a location is determined by a range of physico-chemical and biotic factors in the local environment, as well as larger-scale spatial factors such as sources of recruits. We assessed the relative importance of the species composition of local neighbourhoods and proximal environmental factors on the composition of invertebrate assemblages. 2. Macroinvertebrate assemblages were sampled at 188 running-water sites in the catchment of the River Rede, north-east England. A total of 176 species were recorded. 3. Environmental data, in the form of 13 biotic and abiotic measurements that described stream physical structure, aquatic vegetation and water characteristics, were recorded for each site. Detrended correspondence analysis was then used to simplify nine of these stream environmental variables to create an index of stream structure. 4. The species composition of the invertebrate assemblages was related to the environmental variables, using an information theoretic approach. The impact of the species composition of neighbouring sites on each site was determined using Moran's I and autoregressive modelling techniques. 5. Species composition was primarily associated with water pH and stream structure. The importance of the species composition of neighbouring sites in determining local species assemblages differed markedly between taxa. The autoregressive component was low for Coleoptera, intermediate for Trichoptera and Plecoptera, and high for Ephemeroptera. 6. We hypothesise that the observed differences in the autoregressive component amongst these orders reflects variation in their dispersal abilities from neighbouring sites. [source]

The influence of scale and geography on relationships between stream community composition and landscape variables: description and prediction

FRESHWATER BIOLOGY, Issue 5 2003
Colin R. Townsend
SUMMARY 1.,We analysed an existing database of macroinvertebrates and fish in the context of a newly established geographical information system (GIS) of physical features to determine the relationships between stream community composition and physical factors measured at three landscape scales , catchment, reach and bedform. Both an exploratory (concordance analysis) and a predictive (ausrivas) approach were used. 2.,The environmental variables that most successfully accounted for variation in macroinvertebrate assemblages were mainly ,natural' and at the catchment-scale (relief ratio, basin diameter, etc.) but the human-induced physical setting of percentage of pasture in the riparian zone was also influential. For fish, ,natural' variables were also dominant, but these were mostly at the bedform or reach scales and land use featured strongly. 3.,Geographic location accounted for some of the variation in invertebrate assemblages, partly because geography and influential conditions/resources are correlated but also because different species may have evolved in different places and have not colonised every ,ecologically appropriate' location. Geographic location was not influential in accounting for variation in assemblages of strongly flying invertebrates, supporting the hypothesis that organisms having high dispersal potential can be expected to break down geographic barriers more readily than those with poor dispersal powers. In accord with what is known about the local evolution and restricted distributions of native and exotic species, history (reflected in geography) appeared to account for some variation in fish assemblages. 4.,Given their different mathematical bases, the fact that exploratory and predictive analyses yielded similar results provides added confidence to our conclusions. [source]

Influences of habitat complexity on the diversity and abundance of epiphytic invertebrates on plants

FRESHWATER BIOLOGY, Issue 4 2003
Hiromi Taniguchi
SUMMARY 1. The compound influence of habitat complexity and patch size on stream invertebrate assemblages associated with submerged macrophytes was investigated through field sampling of two natural macrophyte species with contrasting leaf morphologies (complex, Ranunculus yezoensis; simple, Sparganium emersum) and an experiment with two artificial plants with different levels of morphological complexity. 2. The artificial plant experiment was designed to separate the effects of habitat area (patch size) and habitat complexity, thus enabling a more rigorous assessment of complexity per se than in previous studies where only a single patch size was used. Simple and complex artificial plants were established with five different patch sizes corresponding to the range found in natural plants. 3. Invertebrates occurred on both complex and simple forms of natural and artificial plants at similar abundances with dipterans and ephemeropterans being predominant. Taxon richness was higher on structurally complex Ranunculus than on simple Sparganium and was similarly higher on the complex artificial plant than on the simple one, over the entire range of habitat patch sizes. Thus, architectural complexity affected the taxon richness of epiphytic invertebrates, independently of habitat scale. 4. On the natural plants there was no difference in the abundance (both number of individuals and biomass) of invertebrates between simple and complex forms, while on artificial plants more invertebrates occurred on complex than on simple forms. The amount of particulate organic matter, >225 ,m (POM) and chlorophyll a showed mixed patterns on natural and artificial plants, suggesting that the availability of these resources is not an overriding proximate factor controlling invertebrate abundance on plants. The difficulty of extrapolating from experimental results involving use of artificial plants is discussed, especially when considering the relationship between habitat structure and the occurrence of epiphytic invertebrates on natural plants. [source]

Will increased storm disturbance affect the biodiversity of intertidal, nonscleractinian sessile fauna on coral reefs?

GLOBAL CHANGE BIOLOGY, Issue 11 2008
S. J. WALKER
Abstract Relatively little is known about how the future effects of climatic change, including increases in sea level, temperature and storm severity and frequency, will impact on patterns of biodiversity on coral reefs, with the notable exception of recent work on corals and fish in tropical reef ecosystems. Sessile invertebrates such as ascidians, sponges and bryozoans occupying intertidal rubble habitats on coral reefs contribute significantly to the overall biodiversity and ecosystem function, but there is little or no information available on the likely impacts on these species from climate change. The existing strong physical gradients in these intertidal habitats will be exacerbated under predicted climatic change. By examining the distribution and abundance of nonscleractinian, sessile invertebrate assemblages exposed to different levels of wave action and at different heights on the shore around a coral reef, we show that coral reef intertidal biodiversity is particularly sensitive to physical disturbance. As physical disturbance regimes increase due to more intense storms and wave action associated with global warming, we can expect to see a corresponding decrease in the diversity of these cryptic sessile assemblages. This could impact negatively on the future health and productivity of coral reef ecosystems, given the ecosystem services these organisms provide. [source]

Characterization of macrofaunal assemblages associated with sponges and tunicates collected off the southeastern United States

INVERTEBRATE BIOLOGY, Issue 2 2010
Cara L. Fiore
Abstract. Sponges can serve as hosts to invertebrate assemblages that live and reproduce within them. Sponges also constitute a major part of the benthic epifaunal community on the continental shelf of the southeastern United States; however, little is known about these sponges and the assemblages they harbor. In this study, the associated fauna from a variety of sponges and one species of tunicate collected by submersible from the continental shelf and slope of the southeastern United States at depths in the range 18,875 m were examined. Seventeen sponges, comprising eight species (Ircinia campana, Topsentia sp., Geodia sp., Characella sp., Erylus sp., Apylsina archeri, Cliona sp., and Pheronema carpenteri), and three tunicate colonies (Didemnidae) were fully dissected and all associated organisms were identified and counted. Additionally, the sponges Pheronema annae (951 m) and P. carpenteri (770 m) represent new records for the region. The diversity (H,) and density of associates varied considerably among hosts; the densities of associates ranged 0.4,11,684 per 1 L of host volume. Polychaete worms were the most common organisms found, with one species, Haplosyllis spongicola, being especially abundant in I. campana, Topsentia sp., and Cliona sp. The amphipods Ericthonius punctatus and Leucothoe cf. spinicarpa, as well as decapods such as snapping shrimp (Synalpheus sp.) and crabs (e.g., Pilumnus floridana, Micropanope urinator), were also common. The number of symbiont taxa did not significantly increase as the sponge size increased. However, weak positive trends were found between the diversity of associates and increasing canal diameter. Sponges and tunicates were judged to represent legitimate ecological communities harboring a complete food web as well as gravid and juvenile individuals. [source]

Marine biogeographical structure in two highly dispersive gastropods: implications for trans-Tasman dispersal

JOURNAL OF BIOGEOGRAPHY, Issue 4 2007
Jonathan M. Waters
Abstract Aim, Recent genetic and ecological studies of marine invertebrate species with planktotrophic larvae have inferred high rates of gene flow across wide oceanic barriers. We therefore aim to test for the genetic signature of long-distance dispersal in two widespread and abundant marine gastropod taxa. Location, The intertidal and shallow subtidal zones of southern Australia and New Zealand (NZ), which house similar marine invertebrate assemblages despite being separated by the 2000-km-wide Tasman Sea. Methods, We used mtDNA cytochrome oxidase I gene sequence analysis of two gastropod genera exhibiting trans-Tasman distributions, namely Austrolittorina (Littorinidae) (139 specimens; 28 localities) and Scutus (Fissurellidae) (154 specimens; 32 localities). The cool-temperate Australian (A. unifasciata; S. antipodes) and NZ (A. antipodum; S. breviculus) taxa within each genus are morphologically similar but of uncertain taxonomic status. Results, The mtDNA analyses indicate major trans-Tasman genetic discontinuities for both gastropod genera, with no evidence of recent or ongoing intercontinental gene flow. Although both Scutus and Austrolittorina show significant east,west structure within southern Australia , consistent with recent studies of regional marine phylogeography , neither taxon exhibits significant differentiation within NZ. Main conclusions, Morphologically conserved but biogeographically disjunct gastropod populations may exhibit striking phylogeographic discontinuities, even when dispersal abilities appear to be high. On the basis of these data we reject recent calls for the synonymy of NZ and Australian lineages. [source]

Size matters sometimes: wall height and the structure of subtidal benthic invertebrate assemblages in south-eastern Australia and Mediterranean Spain

JOURNAL OF BIOGEOGRAPHY, Issue 12 2003
A. R. Davis
Abstract Aim, Variation in the structure of shallow subtidal invertebrate assemblages was examined over three spatial scales; within reef, between reef and between continents. We sought to provide a context from which to examine and interpret ecological processes between continents. In addition, we predicted that variation in pattern would increase as the scale of examination increased. Location, Reefs near Wollongong and within Jervis Bay in south-eastern Australia and Mediterranean reefs on the Costa Brava (Catalonia), north-eastern Spain. Methods, We compared assemblages on vertical rock walls of two heights , short (< 2 m) and tall (> 3 m) in two temperate regions over the same depth range. Specifically we examined the diversity and cover of invertebrates, the cover and biomass of foliose and crustose algae, the size of invertebrate colonies and the biomass of urchins on short and tall walls (n = 3) at each of two locations in each country. Results, Foliose algae dominated rock walls in Spain and although invertebrate cover was high, colonies were generally very small. Two urchin species were commonly encountered on rock walls in Spain, Arbacia lixula and Paracentrotus lividus; their biomass was relatively low and did not differ significantly between short and tall walls. These findings contrasted strongly with south-eastern Australia, where foliose algae were almost completely absent. A single urchin species, Centrostephanus rodgersii occurred with extremely high biomass on short walls, which were dominated by grazer-resistant crustose calcareous algae. In contrast, the biomass of this urchin was low on tall walls, which were dominated by invertebrates, usually exceeding 95% in cover. Invertebrate colonies were significantly larger on both short and tall walls in south-eastern Australia relative to the Mediterranean. Findings within a country were consistent between the replicate rock walls and between locations. In contrast to our prediction, however, there was significant variation among walls within a location, but not among locations within a continent. Temporal variation in the structure of these assemblages was not examined, but appears limited. Main conclusions, We conclude that submarine topography, i.e. the presence of short or tall rock walls, as a function of rock type and structure, has a marked impact on community structure in south-eastern Australia, but made little difference to the structure of the assemblage in Mediterranean Spain. The differences in structure we observed between walls of different heights in Australia were correlated with differences in the biomass of urchins and they appear to be major determinants of assemblage structure. Interactions among species are often reported from disparate parts of the globe with little or no reference to the structure of the assemblage of which they are a part; we contend that this will hinder interpretation. Our data are consistent with the organisms in these two regions experiencing distinct selection pressures; for example high levels of urchin grazing activity in south-eastern Australia, and shading and whiplash associated with an algal canopy in the Mediterranean. It may not be appropriate to contrast processes operating at very large (intercontinental) scales unless context can be established with a clear understanding of ecological pattern. Objectivos, En el presente trabajo hemos examinado la variación en estructura de comunidades de invertebrados de aguas someras a tres escalas espaciales: dentro de arrecifes rocosos, entre arrecifes y entre continentes. Nuestro objetivo era proveer un contexto para examinar y interpretar procesos ecológicos entre continentes. Además, realizamos la predicción de que el modelo de variación aumentaría conforme aumentaba la escala de observación. Localidad, Arrecifes rocosos cerca de Wollongong y en Jarvis Bay en la zona sudeste de Australia y arrecifes rocosos mediterráneos en la Costa Brava (Cataluña), en el nordeste de España. Metodos, Comparamos comunidades en paredes rocosas verticales de dos alturas , bajas (< 2 m) y altas (> 3 m) en dos regiones templadas y dentro del mismo rango de profundidades. Específicamente, examinamos la diversidad y el recubrimiento de invertebrados, el recubrimiento y la biomasa de algas foliosas e incrustantes, la medida de las colonias de invertebrados y la biomasa de erizos en paredes bajas y altas (n = 3) en dos localidades de cada país. Resultados, Las algas foliosas dominaban las paredes rocosas en España y, aunque el recubrimiento de invertebrados era alto, las colonias eran generalmente muy pequeñas. Dos especies de erizos eran comunes en las paredes rocosas en España: Arbacia lixula y Paracentrotus lividus. Su biomasa total era relativamente pequeña y no mostraba diferencias significativas entre paredes bajas y altas. Estos resultados contrastan con los hallados en el sudeste de Australia, donde las algas foliosas eran prácticamente ausentes. Una única especie de erizo, Centrostephanus rodgersii, se encontraba en las paredes bajas, donde presentaba elevadas biomasas. Estas paredes estaban dominadas por algas incrustantes y carbonatadas resistentes al ramoneo por erizos. En cambio, la biomasa de este erizo era baja en paredes altas, que estaban dominadas por invertebrados, con recubrimientos normalmente por encima del 95%. Las colonias de invertebrados eran significativamente más grandes tanto en las paredes altas como bajas en el sudeste de Australia en comparación con el Mediterráneo. Los resultados dentro de cada país eran consistentes entre las réplicas de paredes estudiadas y entre localidades. Contrariamente a nuestra predicción, sin embargo, había una variación significativa entre paredes dentro de una localidad pero no entre localidades dentro de un continente. La variación temporal en estructura en estas comunidades no fue estudiada, pero parece ser limitada. Conclusiones Principales, Concluimos que la topografía submarina, esto es, la presencia de paredes bajas o altas en función del tipo de roca y estructura, tiene un efecto importante en la estructura de las comunidades en el sudeste de Australia. Este factor, sin embargo, tiene un efecto muy limitado en el Mediterráneo español. Las diferencias en estructura observadas entre paredes de diferentes alturas en Australia se correlacionan con diferencias en la biomasa de erizos, los cuales parecen ser determinantes en la estructura de las comunidades. Frecuentemente se estudian interacciones entre especies en zonas alejadas del globo con escasa o nula referencia a la estructura de la comunidad de la que forman parte. En nuestra opinión este hecho impide una correcta interpretación. Nuestros datos son consistentes con la idea de que los organismos en las dos regiones estudiadas experimentan diversas presiones selectivas, por ejemplo, niveles altos de ramoneo por erizos en el sudeste de Australia, y oscurecimiento y disturbancia mecánica asociadas a la cobertura de algas en el Mediterráneo. No parece apropiado comparar procesos que operan a escalas muy amplias (intercontinentales) sin establecer antes un contexto con una comprensión clara de los parámetros ecológicos. [source]

Does Coastal Foredune Stabilization with Ammophila arenaria Restore Plant and Arthropod Communities in Southeastern Australia?

RESTORATION ECOLOGY, Issue 3 2000
Cameron E. Webb
Abstract In this study we examine whether stabilization of denuded coastal foredunes in southeastern Australia with the exotic grass species Ammophila arenaria (marram grass) restores plant and ground-active arthropod assemblages characteristic of undisturbed foredunes. Vascular plants and arthropods were sampled from foredunes that had been stabilized with marram grass in 1982, and from foredunes with no obvious anthropogenic disturbance (control dunes). All arthropods collected were sorted to Order, and ants (81.5% of all specimens) were further sorted to morphospecies. Abundance within arthropod Orders, as well as richness, composition, and structure of the plant and ant assemblages from control and stabilized dunes, were compared. The abundance of Diptera was significantly greater on stabilized dunes, while the abundance of Isopoda was significantly greater on control dunes. There were no significant differences in morphospecies richness or composition of ant assemblages on the two dunes types, although some differences in the abundances of individual morphospecies were observed. By contrast, stabilized dunes exhibited lower plant species richness and highly significant differences in plant species composition, due mainly to the large projected foliage cover of marram grass. The study revealed that after 12 years, the vegetation composition and structure of stabilized dunes was still dominated by marram grass and, as a result, invertebrate assemblages had not been restored to those characteristic of undisturbed foredunes. [source]

Floodplains of a regulated southern alpine river (Brenno, Switzerland): ecological assessment and conservation options

AQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 6 2002
M. Brunke
Abstract 1.The fifth-order southern alpine Brenno River and its floodplains are severely impaired by embankments, water abstractions and the construction of dams for hydropower generation. The river's annual mean discharge is reduced to 27% of the natural flow and the number of small (50,100 m3 s,1) and medium-sized (101,150 m3 s,1) floods is reduced significantly. 2.Lateral hydrological connectivity has decreased strongly as a result of the flow regulation, whereas the significance of vertical connectivity has increased. The remnants of the middle and lower floodplains still contain springbrooks, ponds, and intermittently connected channels, which are all sustained by emerging groundwater. 3.Aquatic floodplain habitats can be classified partially by faunal composition. The lotic/lentic gradient appears to be a dominant compound factor structuring invertebrate assemblages when considering all aquatic habitats. The exfiltration of groundwater in conjunction with a reduced lateral connectivity enables the occurrence of many stenotopic species. 4.A comparison of present floodplains with those shown on historical maps shows that the fluvial landscape has changed markedly. The proportions of functional floodplain units characterized by autogenic succession and trends to late successional stages (i.e. senescence) have increased. 5.Floodplains of the Brenno river are still considered to represent important ecological areas and they are protected by law. Whilst the legislative protection of floodplains is the basis for conservation, this does not include the restoration of driving hydrological processes. An annual release of small- and medium-sized floods could generate a diversity of disturbances, thereby promoting rejuvenation and counteracting senescence. 6.Alternative conservation options that circumvent ongoing contracts of water use, though generally promising, are limited because of the operation of hydropower schemes. At present the exfiltrations of groundwater mitigate the impacts of flow regulation on the ecological integrity of the floodplains. Copyright © 2002 John Wiley & Sons, Ltd. [source]