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1.
1. We examined the effect of the exotic macrophyte, para grass (Urochloa mutica), on benthic and epiphytic macroinvertebrates of a tropical floodplain in northern Australia. Macroinvertebrates were sampled from four grass communities: (1) para grass, (2) hymenachne (Hymenachne acutigluma), a native perennial; (3) rice (Oryza meridionalis), a native annual, and (4) areas where para grass had been sprayed with herbicide. 2. Macroinvertebrate richness, abundance and community similarity showed very few differences among the grass communities, particularly in the epiphytic habitat. Benthic invertebrates showed some differences among grasses, with lower richness and abundance and different community structure associated with hymenachne. Herbicide control of para grass had no apparent effect on benthic invertebrates but reduced the abundance of epiphytic invertebrates in the short term. 3. The results of this study indicate that para grass has very little impact on macroinvertebrate communities, despite the changes to macrophyte communities. This is probably because para grass has similar physical structure to the native grasses and because none of these grasses contribute directly to aquatic food webs. Control of para grass using herbicide has little impact on aquatic invertebrates. This suggests that predicting the impact of weed invasion in wetlands requires an understanding of both the functional properties of macrophytes and the habitat preferences of the macroinvertebrates. 相似文献
2.
Potamogeton crispus L. (curly pondweed) is a cosmopolitan aquatic macrophyte considered invasive in North America and elsewhere. Its range is
expanding and, on individual water bodies, its coverage can be dynamic both within and among years. In this study, we evaluate
the use of free and low-cost satellite remote sensing data to monitor a problematic emergent macrophyte community dominated
by P. crispus. Between 2000 and 2006, we acquired eight satellite images of 24,000-ha Lake Sharpe, South Dakota (USA). During one of the
dates for which satellite imagery was acquired, we sampled the lake for P. crispus and other emergent macrophytes using GPS and photography for documentation. We used cluster analysis to assist in classification
of the satellite imagery and independently validated results using the field data. Resulting estimates of emergent macrophyte
coverage ranged from less than 20 ha in 2002 to 245 ha in 2004. Accuracy assessment indicated 82% of image pixels were correctly
classified, with errors being primarily due to failure to identify emergent macrophytes. These results emphasize the dynamic
nature of P. crispus-dominated macrophyte communities and show how they can be effectively monitored over large areas using low-cost remote sensing
imagery. While results may vary in other systems depending on water quality and local flora, such an approach could be applied
elsewhere and for a variety of macrophyte communities. 相似文献
3.
Aerial surveys from 1981 to 1984 were used to identify monthly changes in the abundance of magpie geese on Jive floodplains in the Alligator Rivers Region of the monsoonal Northern Territory, and ground surveys were conducted during the same period on one of the plains to provide more detailed distributional information. The aerial surveys showed that the Magela floodplain was inhabited by few geese during the wet season (November-March), but that numbers then increased to an estimated average peak of 80 000 in the late dry season. The Nourlangie floodplain and Boggy Plain (a large backswamp of the South Alligator floodplain) exhibited a similar pattern, except that the peaks occurred 2–3 months before the end of the dry season and comprised many more geese (an estimated average of 350 000 birds). In contrast, geese were uncommon on the East Alligator floodplain except during the wet season, and densities and numbers were lower than on the three previous plains. The Cooper floodplain was occupied intermittently, and numbers and densities were always relatively low. Geese appeared to return from their breeding localities to the floodplains of the Alligator Rivers Region progressively during the dry season, concentrating first on the extensive Eleocharis swamps of the Nourlangie floodplain and then waiting out the remainder of the dry on the substantial permanent waters of the Magela floodplain and other nearby wetlands. Ground surveys on the Magela floodplain suggested that geese were highly mobile, apparently seeking suitable nesting habitat in the late wet season, and then a sequence of feeding areas during the dry season. Aerial surveys underestimated densities; on the basis of ground surveys, average peak numbers on the Magela plain were calculated to be 500 000. We estimate that the Alligator Rivers Region supported an average of about 1.6 million geese in the dry season, but very many fewer during the wet season. 相似文献
4.
Pollen loads in the atmosphere of Darwin, a city located in the wet‐dry tropics of Australia, have been monitored for the period March 2004 to November 2005 as part of a large research program looking at atmospheric particles and human health. Seven pollen types dominate the pollen spectrum, the herbaceous families of Poaceae (grasses) and Cyperaceae (sedges), as well as several native tree and shrub taxa, Acacia, Callitris, Casuarina, Arecaceae and Myrtaceae. The pollen loads were found to have a strong seasonal component associated with the alternating wet (November to March) and dry (April to October) seasons of the region. Seventy percent of the yearly pollen load is captured during the dry season, with the peak pollen period occurring at the onset of the dry season (April–May) when most grasses are in flower. The daily pollen concentration decreases as the dry season progresses, accompanied by a change in composition; fewer herbaceous but increasing woody taxa. Preliminary health outcomes reveal a positive association between hay fever, Poaceae and Acacia pollen, as well as a significant association between total fungal spore concentrations and asthma. The Darwin record contrasts significantly with surveys conducted in the subtropical and temperate cities of Australia where temperature as opposed to rainfall and the prevalence of northern hemisphere exotic tree species have a greater influence over the seasonality and composition of the pollen loads. 相似文献
5.
Changes in phosphorus content of two aquatic macrophytes according to water velocity,trophic status and time period in hardwater streams 总被引:4,自引:0,他引:4
Virginie Baldy Michèle Trémolières Muriel Andrieu Jacques Belliard 《Hydrobiologia》2007,575(1):343-351
We examined the influence of water velocity, trophic status, and time period on the phosphorus content of two aquatic macrophytes.
We sampled Berula erecta (Huds.) and Callitriche obtusangula (Le Gall.) from 17 oligosaprobic hardwater streams in the Alsatian Rhine floodplain of northeastern France. Sampling was
conducted on a monthly basis during a 9-month period from August 1996 to April 1997. For B. erecta, phosphorus content of shoots and roots were correlated to water phosphorus content but not to sediment phosphorus content.
The range of phosphorus shoot content of C. obtusangula was similar to that of B. erecta. Phosphorus shoot content of C. obtusangula was not correlated with water and sediment phosphorus content. In one stream where both species were present on the same
sampling dates, shoot phosphorus content decreased when water velocity was high, particularly for C. obtusangula. Additionally, a significant effect of time period was observed for both species when the water velocities were low. The effect
of water velocity was only significant from spring (April) to autumn (October) when plant phosphorus content was highest.
Handling editor: S. Magela Thomaz 相似文献
6.
N. E. PETTIT P. BAYLISS P. M. DAVIES S. K. HAMILTON D. M. WARFE S. E. BUNN M. M. DOUGLAS 《Freshwater Biology》2011,56(6):1047-1064
1. Globally, tropical floodplains are highly productive ecosystems. This is largely because of predictable seasonal rains providing replenishing floodwaters that stimulate nutrient turnover which, in turn, substantially boosts both primary and secondary productivity. This is associated with concomitant shifts in the types of primary producers and associated food webs. 2. The Magela Creek floodplain on Kakadu National Park in northern Australia is one of the most studied tropical freshwater ecosystems in Australia and provides an opportunity to collate and examine information on organic carbon sources and pathways through food webs to gain a fundamental understanding of how these systems may function. 3. We reviewed biophysical information published since the early 1980s to construct an assessment of the carbon resources for the channel and floodplain. 4. We conclude that macrophytes, largely in the form of grasses and aquatic plants, produce the greatest above‐ground biomass on the Magela Creek floodplain. Although macrophytes provide suitable substrata for the attachment of epiphytes, they do not appear to be an important carbon source for aquatic consumers themselves. Nevertheless, macrophytes do provide critical seasonal food and habitat structure for other producers and consumers on the floodplain, such as the abundant magpie geese. 5. We developed a generalised conceptual food web and carbon budget contrasting the ‘wet’ and ‘dry’ seasons for the Magela Creek system, as a representative of tropical seasonal floodplain systems. 6. Our conceptual model of tropical floodplains indicates that knowledge of the seasonal and spatial links and exchanges between the floodplain and the river is critical in understanding ecosystem function. 相似文献
7.
Robert G. Doupé Jim Mitchell Matthew J. Knott Aaron M. Davis Alan J. Lymbery 《Wetlands Ecology and Management》2010,18(1):69-78
Foraging by feral pigs can strongly affect wetland vegetation assemblages and so too wider ecological processes, although
their effects on freshwater ecosystems have seldom been studied. We assessed the ecological effects of pig foraging in replicate
fenced and unfenced ephemeral floodplain lagoons in tropical north-eastern Australia. Pig foraging activities in unfenced
lagoons caused major changes to aquatic macrophyte communities and as a consequence, to the proportional amounts of open water
and bare ground. The destruction of macrophyte communities and upheaval of wetland sediments significantly affected wetland
turbidity, and caused prolonged anoxia and pH imbalances in the unfenced treatments. Whilst fencing of floodplain lagoons
will protect against feral pig foraging activities, our repeated measures of many biological, physical and chemical parameters
inferred that natural seasonal (i.e. temporal) effects had a greater influence on these variables than did pigs. To validate
this observation requires measuring how these effects are influenced by the seemingly greater annual disturbance regime of
variable flooding and drying in this tropical climate. 相似文献
8.
Determinants of growth of the flammable grass,Triodia scariosa: Consequences for fuel dynamics under climate change in the Mediterranean region of South Eastern Australia
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Rebecca K. Gibson Ross A. Bradstock Trent Penman David A. Keith Don A. Driscoll 《Austral ecology》2016,41(6):594-603
Environmental conditions may influence the presence and strength of competitive interactions between different life forms, thereby shaping community composition and structure, and corresponding fuel dynamics. Woodland and shrubland communities of the Mediterranean climate region of South Eastern Australia contain a varied mixture of herbaceous and woody plants. The ratio of herbaceous to woody plants changes along gradients of temperature, moisture and soil fertility. This study aimed to experimentally examine the relative importance of, and interactions between environmental controls (moisture and soil fertility) on the balance of dominant herbaceous (Triodia scariosa) and woody plants (e.g. Acacia ligulata and Leptospermum coriaceum) and their ultimate effects on fuel and fire regimes. The results suggest that environmental determinants of the growth of T. scariosa are likely to be more important than interactions with shrubs in controlling the distribution of T. scariosa. The growth of T. scariosa was consistently higher under hot temperatures and on the less fertile yellow sands, which dominate the south of the region. The results suggest that there is strong potential for the distribution and abundance of T. scariosa to be altered in the future with changes in temperature associated with climate change. The distribution of soil types across the Mediterranean climate region of South Eastern Australia may be predisposed to favour the southerly expansion of T. scariosa‐dominated communities in the future under a warmer climate. 相似文献
9.
Seed banks were examined in a Taxodium distichum L.-Nyssa aquatica L. (cypress-tupelo) swamp forest and an adjacent bottomland hardwood forest on the floodplain of the Savannah River in South Carolina. Thirty 0.01 m2 soil cores were collected in each community at each of three sampling times: before seed fall, after seed fall, and after an early spring river level rise had inundated both communities. Germination and sieving techniques were used to enumerate seeds in each sample. Woody seed banks of the two communities were dissimilar in species composition with both underrepresenting the species composition of the standing vegetation. In contrast, herbaceous seed banks of both communities were similar in species composition with greater species diversity in the seed banks than in the standing vegetation. Both the herbaceous and woody seed banks of the hardwood community changed significantly in seed densities across the three collection dates. Densities increased from September to December, after seed fall for many species, but decreased in April after the early spring water level rise. Seed densities did not change significantly in the cypress-tupelo community across the three collections. Hydrologic regime appears to have a major influence on seed bank composition and dynamics in southeastern riverine swamps. 相似文献
10.
Biomass and primary-production of herbaceous plant communities in the Amazon floodplain 总被引:3,自引:3,他引:0
The increase in biomass of different aquatic and terrestrial herbaceous plant communities was measured during various growth periods in the Amazon floodplain near Manaus. Maximum biomass varied from 4–11.2 t ha–1 dry weight in mixed annual terrestrial communities to 6–23 t ha–1 in aquatic annual species (Paspalum repens, Oryza perennis, Luziola spruceana and Hymenachne amplexicaulis) and 15.6–57.6 t ha–1 in communities of the perennial species Paspalum fasciculatum. Cumulative biomass of 3 successively growing annual species reached 30 t ha–1 a–1. Net primary production is considerably higher than maximum biomass. Paspalum fasciculatum reached 70 t during a growth period of 8 months. If one considers for annual species a monthly loss of 10–25% of the biomass, then net primary production in areas with three successive macrophyte communities and a cumulative maximum biomass of 30 t ha–1 is estimated to reach up to 50 t ha–1 a–1. Annual P/B ratio may reach about 3. 相似文献
11.
Zati Sharip Shon S. Schooler Matthew R. Hipsey Richard J. Hobbs 《Biological invasions》2012,14(5):1029-1044
In this study we: (1) present a quantitative spatial analysis of the macrophyte communities in Lake Chini with a focus on
the biogeographical distributions of the native Nelumbo nucifera and the invasive Cabomba furcata; (2) examine the environmental changes that affect plant community composition; and (3) outline a conceptual model of the
variation of ecological processes that shape the macrophyte communities. Plant species cover, biomass of C. furcata and N. nucifera, and water quality and environmental variables were measured before and after monsoonal floods in September 2009 and April
2010. Permutational multivariate analysis was used to examine the significance of the invasion of C. furcata at different spatial scales. Relationships between plant species cover and environmental variables before and after flooding
were examined using principal coordinates analysis and non-parametric multivariate multiple regressions. Our findings suggest
that (1) Variation in plant communities was significant at the lake scale and the distribution of plant species changed after
annual floods. (2) Invasion by C. furcata significantly affected the overall plant community composition. (3) C. furcata biomass increased after the monsoonal season, which indicates that C. furcata is adapted to flooding events and that it is becoming increasingly abundant. (4) In addition to the strong monsoonal effect,
total depth, nutrient concentration, and sediment type were important environmental variables that significantly affected
plant community composition. The macrophyte community in Lake Chini is highly dynamic. The spatial and temporal plant community
dynamics are associated with flood regime, water quality, and substrate. Human-induced changes in these parameters are likely
shifting the macrophyte dominance from floating-leaved to submerged species. 相似文献
12.
ALEXANDER R. WILLIAMS 《Austral ecology》1984,9(3):199-202
The stability of the Magela floodplain prior to the development of uranium mining at Ranger, in the Magela catchment, was estimated by comparing aerial photographs taken in 1950 and 1975, using the density of Melaleuca swamp forest as an index of change. The 1975 photographs were interpreted in the light of a ground survey carried out in the dry season of 1976. There was no increase in the area occupied by Melaleuca trees, indicating that infilling of perennial swamp and plant succession were not significant agents of change in this period. Thirty-eight per cent of the forested area suffered a significant decrease in tree density: fire, wind and buffalo are among the probable causes, and these hazards should be taken into account in monitoring the effects of the uranium mining. 相似文献
13.
The presence of algae can greatly reduce the amount of light that reaches submerged macrophytes, but few experimental studies have been conducted to examine the effects of algae on biomass and structure of submerged macrophyte communities. We constructed communities with four submerged macrophytes (Hydrilla verticillata, Egeria densa, Ceratophyllum demersum, and Chara vulgaris) in three environments in which 0 (control), 50 and 100% of the water surface was covered by Spirogyra arcta. Compared to the control treatment, the 100% spirogyra treatment decreased biomass of the submerged macrophyte communities and of all the four macrophytes except C. demersum. Compared to the control and 50% treatments, the 100% treatment significantly increased relative abundance of C. demersum and decreased that of E. densa. Therefore, the presence of S. arcta can greatly affect the productivity and alter the structure of submerged macrophyte communities. To restore submerged macrophyte communities in conditions with abundant algae, assembling communities consisting of C. demersum or similar species may be a good practice. 相似文献
14.
A. R. WILLIAMS 《Austral ecology》1979,4(2):239-247
Magela Creek is a hydrologically complex waterway which drains Australia's two largest uranium deposits, carries a pastoral and tourist industry and has been proposed for inclusion in a national park. In this study, the vegetation and stream patterns of the floodplain are described and are used as indicators of surface water movement through the system. The Magela floodplain was found to be a freshwater lagoon, enclosed at its outlet by, the floodplain of the East Alligator River; the vegetation types are direct indicators of water depth within the lagoon. The capacity of the lagoon is approximately 60 × 106 m3, the average daily input during the wet season is approximately 3% of the lagoon volume and during the dry season the lagoon dries out to approximately 5 × 106 m3 of perennial swamp. The lagoon is maintained by the East Alligator River and so its hydrology must not be studied in isolation but in relation to the larger system to which it belongs. 相似文献
15.
Tracking a century of change in trophic structure and dynamics in a floodplain wetland: integrating palaeoecological and palaeoisotopic evidence 总被引:1,自引:0,他引:1
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Giri Kattel Peter Gell Marie‐Elodie Perga Erik Jeppesen Rosie Grundell Sandra Weller Atun Zawadzki Linda Barry 《Freshwater Biology》2015,60(4):711-723
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16.
The influence of different macrophyte taxa or growth forms on biological and environmental variables is often analysed in
one-lake studies. However, the unique combination of non-vegetational characteristics of a waterbody, i.e. its site identity,
can be an influential factor in itself, shaping the measured parameters irrespective of the presence or absence of certain
macrophyte species. In this situation, the relative strengths of all factors can be determined best in a study that explicitly
accounts for differences in the identity of the waterbodies. Several functional macrophyte groups are known to provide a potent
microinvertebrate refuge or permanent habitat. The objective of this study was to detect patterns in the zooplankton assemblages
associated with different extensive habitats of macrophyte species and to relate these patterns to three major factors: the
microhabitat, the pond identity and the seasonality in the warmer months of the year. Five ponds located in the Woluwe catchment
of the Brussels-Capital Region (Belgium) were studied monthly for macrophyte and zooplankton characteristics from July until
October 2005. The vegetation in the clear ponds was characterized by extensive monospecific stands (Ceratophyllum, Chara, Nitella, Potamogeton, Nuphar and filamentous algae). Zooplankton could be analysed in seven different vegetation types and in the open water zones and
contained a total of 17 cladoceran and 27 rotifer genera. Principal components analysis (PCA) ordination of zooplankton communities
showed a seasonal gradient and a tendency to group within-pond habitats, although they differed in macrophyte species and
habitat structure. Despite the absence of clustering of similar microhabitats across ponds, percent volume infested (PVI),
vegetation biomass density and Daphnia length (used as a proxy for fish predation pressure) contributed significantly positive to the Shannon zooplankton biodiversity
indices. Moreover, densities of most zooplankton subgroups and of total zooplankton were significantly and positively related
to PVI. It is assumed that in eutrophic ponds, extensive, often monospecific macrophyte vegetations provide an ecological
environment suitable for both macrophyte-associated species and migrating pelagic zooplankton, thereby maintaining a high
microinvertebrate biodiversity. 相似文献
17.
The benthic macroinvertebrate community (BMI) in a freshwater coastal dune lake without a surface outlet was investigated in May and October, 1986. Fifty-three invertebrate taxa were identified from Carter Lake, including three euryhaline crustacean species (Corophium spinicorne, Gnorimosphaeroma oregonensis lutea, and Acanthomysis awatchensis). Corophium spinicorne dominated the BMI communities of the littoral zones and sphaeriid clams dominated the deepwater community.The lake level dropped about 2.5 m between April and October. Based upon this decline, the lake bottom was divided into four major habitats: a sandy temporarily submerged littoral zone (A); a sandy submerged littoral zone (B); and mid-depth zone of mixed mud and sand and the macrophyte, Nitella (C); and a deep zone (D) with soft mud. The average density of BMI was highest in the littoral zones (A and B) in May and in zone B in October (zone A was dry). The lowest density occurred in zone D. In May, BMI biomass was highest in the littoral zones, but the biomass was highest in the mid-depth zone in October. The mid-depth zone in October. The mid-depth zone had the most diverse community.The two most abundant species in the temporarily submerged area, Corophium spinicorne and Juga plicifera, were found in greater numbers deeper in the lake after the water level dropped, suggesting migration by these species in response to changing water levels. 相似文献
18.
In the past decade, extreme hydrological events were expressed with extreme droughts and floods in temperate regions. The
aim of this paper is to explain how such changes in hydrology can influence cyanobacterial populations in floodplain ecosystems.
We therefore analyzed a 6-year (2003–2008) study of the phytoplankton in the Kopački Rit floodplain, one of the largest natural
floodplains in the middle section of the Danube River (Europe). During the studied period, the shallow floodplain lake shifted
between a state of turbid water, characterized by high phytoplankton biomass and regular appearance of cyanobacteria blooms,
to a state of clear water with very low phytoplankton biomass and absence of cyanobacteria, and back to the turbid state.
Apparently, the major forces driving the cyclic shift were closely related to extremely high and long-lasting flood events.
Significant increase in water level, low hydraulic residence time of water, decrease in transparency and low-light climate,
together with mass developed aquatic macrophyte vegetation in the whole inundated floodplain were unfavorable conditions for
growth and proliferation of cyanobacteria. With the establishment of the flood regime characterized by long-lasting periods
without flooding, in-lake processes prevailed leading to cyanobacterial bloom. The most successful were filamentous non-N-fixing
cyanobacteria tolerant to mixed and low-light conditions (Planktothrix and Limnothrix) and invasive species Cylindrospermopsis raciborskii. Their massive development led to the establishment of a phytoplankton steady state. All our results demonstrate that the
altered intensity and frequency of flood events will have pronounced effects on the appearance of cyanobacterial blooms and
generally on alternative stable states in the floodplain. Relating to this, management objectives should be focused on qualifications
of changes in hydrology and projecting those effects for potential floodplain restoration. 相似文献
19.
Werther Pereira Ramalho Iberê Farina Machado Lisandro Juno Soares Vieira 《Biotropica》2018,50(2):338-345
Beta diversity can provide insights into the processes that regulate communities subjected to frequent disturbances, such as flood pulses, which control biodiversity in floodplains. However, little is known about which processes structure beta diversity of amphibians in floodplains. Here, we tested the influence of flood pulses on the richness, composition, and beta diversity of amphibians in Amazonian floodplain environments. We also evaluated indicator species for each environment. We established linear transects in three environments: low várzea, high várzea, and macrophyte rafts. Species richness decreased and beta diversity increased according to the susceptibility of habitats to flood pulses. Indicator species differed among environments according to forest succession promoted by the flood pulse. The decrease in species richness between high and low várzea is due to non‐random extinctions. The higher rates of species turnover between várzeas and macrophyte rafts are driven by the colonization of species adapted to open areas. Our results highlight that the maintenance of complex environments is needed to protect biodiversity in floodplains. 相似文献
20.
Biomass changes across an annual cycle were followed at two sampling sites in the floodplain marsh of the Lower Paraná River: close to the river-shore and 800 m inside the floodplain marsh, both dominated by Scirpus californicus and Cyperus giganteus. Tidal influence determines a daily exchange of water between the river and the floodplain marsh.Estimated net primary production was higher in the river (2820 against 1770 g m–2). Contents of nitrogen and phosphorus in plant tissue decreased from the river to the floodplain (0.62 to 0.45% N and 0.18 to 0.14% P). In spite of the important water exchange between the river and the floodplain, a decrease in nitrate, oxygen and suspended matter, and an increase in soluble reactive phosphorus in the water were observed from the river towards the floodplain marsh.A primary production gradient exists from the river to the inner floodplain marsh, where production is nitrogen-limited, sustained mainly on nutrients supplied by the river. Floodplain marshes are nitrate sinks, probably through denitrification losses and macrophyte uptake. 相似文献