bluuebunny/crossref_metadata_2025_split huggingface dataset:
Co‐existence of three species of amphibious plants in relation to spatial and temporal variation: Investigation of plant responses
Authors: YEN S. , MYERSCOUGH P. J. 
Published: July 2006

AbstractPlant responses in Ludwigia peploides (Kunth) Raven ssp. montevidensis (Spreng.) Raven and Marsilea mutica Mett., and the introduced Myriophyllum aquaticum (Vellozo) Verdc. were observed and related to co‐existence of the species in a freshwater lagoon in the Sydney basin.Water levels vary in the lagoon, and plants of all three species grow readily from stem fragments on freely draining, waterlogged and submerged soils. In Marsilea, sporelings develop rapidly from ruptured sporocarps when wet. In Ludwigia, the seeds germinate in white and in red light, but not in darkness or far‐red light. They germinate readily on soil and in water, floating or when held submerged. At 30°C, germination is rapid, at 40°C slower and less, and at 10°C nil, but seeds imbibed at 10°C and then exposed at 15°C have greater and more rapid germination than seeds maintained at 15°C.In relation to seasonal variation, plants of all three species grew at 10, 20, 30 and 40°C on freely draining, waterlogged and submerged soils, with the optimum temperature for growth apparently lower in Myriophyllum than in the other two species.In relation to water depth, plants of all three species grew when submerged to I m; the stems of Ludwigia and Myriophyllum elongating and reaching the water surface, and the petioles in Marsilea elongating bringing the leaf blades on to the surface, each within a week during summer. The floating leaf blades in Marsilea increase in size with depth of submergence of the subtending shoots.Mean relative growth rates (R̄) under the most favourable experimental conditions were least in plants of Marsilea, the species occurring along more exposed parts of the shoreline in the lagoon.It was concluded that, while water levels in the lagoon were stable, differences in growth form between the species were probably more critical in their co‐existence than quantitative differences in their growth: the floating leaves of Marsilea, being more resistant to wind and wave action than the floating shoots of Ludwigia and Myriophyllum, occupy the more exposed parts of the lagoon 'S edge. The most sheltered parts are occupied by the shoots of Myriophyllum which ride high on the water and overtop shoots of Ludwigia. Shoots of Ludwigia appear to be more resistant than those of Myriophyllum to removal and damage by wind and wave action, and achieve their greatest abundance on the water surface in situations of intermediate exposure to wind and wave action.Using Grubb's (1977) classification of niches, in Bushells Lagoon the three species appear to be primarily differentiated in habitat niche, less in regeneration niche and even less in phenological niche. In the lagoon, their habitat niches apparently overlap in water depth but are differentiated along a gradient of exposure.
Regional variation in kwongan in the central wheatbelt of south‐western Australia
Authors: BROWN J. M. 
Published: July 2006

AbstractThis study examined the floristic variation at 20 sites of sclerophyllous shrubland (kwongan) occurring on lateritic soils in the central wheatbelt of south‐western Australia. The results show that this kwongan is as floristically rich and varied as the kwongan in the northern and southern sandplain areas of the south‐west. Six sequential groups of sites can be identified along the rainfall gradient present over the study area; 29 species are selected as indicators of the floristic groups. The distribution of many of the remaining 426 species suggests a continuum of floristic change along the rainfall gradient. One hundred and forty‐five species were only recorded once and thus contributed to the high species richness of the sites and the low level of floristic uniformity between the stands. There were significant trends in the proportions of lifeforms with respect to the rainfall gradient. Evidence of the response of the plants to an obvious environmental gradient and the increased understanding of this complex vegetation type will provide conservation managers with some rationale for setting priorities for reserve acquisition and management.
Comparison of seed removal by ants in vegetation on fertile and infertile soils
Authors: MOSSOP M. K. 
Published: July 2006

AbstractPlants which have seeds adapted for dispersal by ants (myrmecochores) are more common in some vegetation types than others. In Australia, myrmecochores are common in sclerophyll shrublands which are associated with infertile soils but not in forests on fertile soils. One hypothesis to explain this difference is that ants are less abundant or less active in seed removal on fertile soils. A test of this hypothesis was carried out on four sites in the Royal National Park, south of Sydney, by measuring the number of myrmecochorous seeds removed by ants in a 24 h period. It was found that the removal rates of seeds were slightly higher on fertile sites although this difference was not significant. The hypothesis that a lower removal rate on fertile soils could account for the lower percentage myrmecochory was therefore rejected. Apart from the gross removal rate of seeds by ants, other differences in ant behaviour might be important. It is possible that a greater proportion of ant species unfertile soils are seed predators or ineffective seed dispersers, and evidence obtained indicates that this is worthy of further research.
The vegetation of seacliffs and headlands in New South Wales, Australia
Authors: ADAM P. , STRICKER P. , WIECEK B. M. , ANDERSON D. J. 
Published: July 2006

AbstractA phytosociological survey of seacliff and headland vegetation on the central and south coast of New South Wales was carried out. Analysis of the quadrat data led to the recognition of 15 communities; the occurrence of a number of other vegetation types is briefly discussed.The vegetation types fall into three major groupings: grasslands, scrub and heathland, although the coincidence between structural and floristic boundaries is poor. Ordination of the communities indicates that the major factors varying between communities are exposure and soil fertility, the grasslands and scrubs occurring on more fertile soils than the heathlands.Amongst the woody communities it is suggested that the two major groups recognized fall into different phytosociological alliances, although lack of studies of Australian vegetation limits the applicability of a conventional hierarchical classification. The true heathlands correspond closely with the alliance Leptospermion, previously recognized in Victoria. The scrub communities are assigned to a new alliance, the Westringio‐Banksion integrifoliae.
Interactive effects of fire frequency and site factors in tropical Eucalyptus forest
Authors: FENSHAM R. J. 
Published: July 2006

AbstractAn area of eucalypt forest on a rocky ridge, at the Solar Village near Darwin, protected from fire for 10 years, was compared with surrounding irregularly and regularly burnt vegetation. Vegetation patterns were influenced by fire history and aspect. Species richness was highest where the fire regime was moderate, and lowest in the fire‐protected bush. The vegetation response at the Solar Village contrasted with another experiment, conducted at Munmalary in northern Australia, where fire was excluded from eucalypt forest and woodland. Very low numbers of facultative monsoon forest species seem favoured with fire protection at the Solar Village. Almost all common tree and shrub species moved into the mid canopy with fire protection, compared to Munmalary where most tree species did not leave the ground layer. The difference in the response of these two places is attributed to the interaction between site and fire influences and it is suggested that structural mutability of these forests increases on stressful sites, although the actual mechanics of the site/fire interactions remains unclear. There is no evidence to support an interactive model which predicts that relief from fire and favourable soil moisture conditions allows the accession of broadleaved shrubs into the mid storey.
Distribution and abundance of magpie geese, Anseranas semipalmata, in the Alligator Rivers Region, Northern Territory
Authors: MORTON S. R. , BRENNAN K. G. , ARMSTRONG M. D. 
Published: July 2006

AbstractAerial 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.
Prolonged exposure to sheep grazing reduces the palatability of Australian saltbush populations
Authors: PEARSON J. T. , SPARROW A. D. , LANGE R. T. 
Published: July 2006

AbstractThis study examined the variability in palatability of populations of Atriplex vesicaria and the influence of past grazing history on mean palatability to sheep. Twenty saltbush plants (10 male, 10 female) were collected from each of six locations across chenopod shrubland of South Australia; three populations came from areas with long records of intensive sheep pastoralism and three from areas with negligible stock grazing in the past. The plants were transplanted into an experimental paddock at Middleback Station, near Whyalla, South Australia and the paddock was grazed by three sheep for nine days. Relative palatability of the populations was assessed by their rates of decline in bush biomass, as indexed by loss of tagged terminal shoots.Overall accumulated tag loss after 9 days was significantly different between populations. These differences were enhanced when dung drop in paddock subdivisions, flowering status of bushes, and leaf sodium and potassium concentrations were included as covariates in tag loss models. Although there was no clear separation of grazed versus ungrazed populations by tag loss alone, the covariate models demonstrated a significant difference between grazing history types, with grazed populations being less palatable. Examination of model residuals showed heterogeneity of palatability to be higher in the grazed populations. This study indicates that the piosphere is a gradient of variability in palatability as well as a gradient of floristic composition.
Population subdivision in Australian temperate marine invertebrates: Larval connections versus historical factors*
Authors: AYRE DAVID J. 
Published: July 2006

AbstractThis paper reviews the use of genetic data, in combination with manipulative experimentation, to infer the mode of reproduction and the extent and directionality of dispersal for a range of Australian temperate marine invertebrates. Local populations of obligately sexually reproducing species have been inferred to be strongly interconnected by larval dispersal, over distances of thousands of kilometres. Their larvae may be subject to strong post‐settlement selection, but this selection is independent of obvious geographic or intertidal gradients. Within local populations selection may therefore result in apparently chaotic genetic patchiness which is eliminated by the effects of sexual reproduction and the widespread dispersal and mixing of the colonizing larvae of each generation. In partial contrast, local populations of species which rely on asexual reproduction for the maintenance of populations show evidence of similar larval connections, but no recent settlement of their sexually generated larvae has been demonstrated. The apparent connectedness of these populations may reflect either historical events or a more episodic pattern of settlement by sexually generated larvae. Local populations of these species are more highly differentiated as a result of the continued asexual replication of a limited number of genotypes. In one of these species, reciprocal transplantation of the clones within and among populations has revealed that resident clones can be highly locally adapted (as reflected by much higher asexual fecundity), which implies that selection is an important determinant of the composition of local populations. Nevertheless, the failure to detect continuing sexual recruitment into these populations obscures the evolutionary significance of this finding.
Is predation capable of interacting with other community processes on rocky reefs?*
Authors: FAIRWEATHER PETER G. 
Published: July 2006

AbstractRecent ecological studies have postulated some indirect effects of predation, which are thought to arise by a variety of interactions propagating through the many vertical and horizontal links in food webs. Such theoretical explanations have been invoked by some empirical studies that demonstrated surprising or unexpected results in field experiments. Studies of intertidal and subtidal portions of temperate rocky reefs provide some of the best examples of such indirect effects of predation. Rarely, however, have the actual mechanisms involved been elucidated. To do this requires independent evidence of how processes that are only indirectly linked to predation are affected by a variety of predation regimes. This paper speculates on how factors such as competition, mutualism, desiccation, wave action and variation in recruitment on seashores might interact with predation, both during and subsequent to predatory events. I present evidence from experiments with predatory whelks in New South Wales, Australia, to emphasize the plausibility of these speculations. Predation on local seashores indirectly benefited algae by removing small grazers, providing bare space for larger grazers and living space for cryptic animals, and interacted synergistically with barnacle recruitment to increase turnover of the prey population. These studies indicate the value of elucidating experimentally the mechanisms by which indirect effects are proposed to occur. Only by demonstrating that the effects work as hypothesized can they be pronounced unambiguously as particular indirect effects. Without such evidence, other possibilities (either more simple or more complex) need to he investigated.
Podocarpus lawrencei (Hook. f.): Population structure and fire history at Goonmirk Rocks, Victoria
Authors: BARKER PHILIP C. J. 
Published: July 2006

Abstract Podocarpus lawrencei is a native conifer which normally occurs as a shrub in alpine, and less often in sub‐alpine, communities in New South Wales, Victoria and Tasmania. A disjunct and unusual distribution occurs at Goonmirk Rocks, in north‐east Victoria, in a montane, wet forest environment in which P. lawrencei grows as a procumbent and sometimes vertical tree up to 13 m tall. The communities in which P. lawrencei occurs at Goonmirk Rocks are described, and the population structure of P. lawrencei is determined using an age class model. Measurement of light regimes and of the nutrient status of these communities indicate differences between areas of active regeneration and those with none, and between forest types that do support P. lawrencei and those that do not. P. lawrencei is determined to be a stable component of the vegetation of Goonmirk Rocks, where it attains its best development on the margins of cool temperate rainforest where a broken canopy and the long‐term absence of fire allow it to develop into a low scrub with simple floristics. A community fire history is reconstructed using the age class model, fire scars and the age of Acacia dealbata.
The relocation of ant nest entrances: Potential consequences for ant‐dispersed seeds
Authors: HUGHES LESLEY 
Published: July 2006

AbstractThe rate at which ant nests relocate may affect the fate of ant‐dispersed seeds by influencing nutrient and seed accumulation in localized areas. In this study, the movement of ant nest entrances was monitored in fixed quadrats in dry sclerophyll woodland in Kuringai Chase National Park, NSW. Changes in entrance location were rapid for most species, with few entrances remaining in use for more than 6 months. Approximately 30% of entrances that closed were subsequently re‐opened. There was no obvious seasonal pattern in entrance relocation. After 1 year, between 5 and 40% of the ground surface of the quadrats had been within 10 cm of a nest entrance. New nest entrances did not cluster near old entrances, indicating that nest entrance relocation may be accompanied by changes in underlying nest structure. Nutrient levels in soil samples from active nests of Rhytidoponera metallica, Aphaenogaster longiceps, Pheidole sp. 1 and Iridomyrmex sp. 8 did not differ significantly from random locations.The rapid changes in entrance location and the lack of nutrient enrichment may be the result of continual and progressive underground shifts in nest location. Such shifts have three potential consequences for seeds that remain buried within the nests. First, seeds will not benefit following germination by being in a nutrient‐rich microsite. Second, a proportion of seeds collected by harvester ant species may escape predation if left in an abandoned section of the nest. Third, concentrations of seeds in localized areas may be reduced, leading to a reduction in competition between establishing seedlings.
Oviposition and larval dispersal of the common armyworm, Mythimna convecta (Walker) (Lepidoptera: Noctuidae)
Authors: McDONALD GARRICK 
Published: July 2006

AbstractThe common armyworm, Mythimna convecta (Walker), is a pest of cereal crops and pasture grasses in Australia. During autumn, egglaying in grasslands commonly occurs before plant growth commences. The possible association between oviposition and dried grasses was investigated in field studies of larval distribution in a pasture and a crop habitat, and in laboratory studies of oviposition site preferences and the mode of dispersal of newly hatched first instar larvae. A comparison of a green grass pasture with and without a component of dried grass showed that highest densities of M. convecta larvea. were found in the former. In the laboratory, egg batches were laid between plant parts in close contact, such as between the stem and leaf axil and between seeds in the seed head. The crevices in dried plant material and seed‐heads were significantly more acceptable for oviposition than in green foliage. Oviposition in dried plant material enables M. convecta to rapidly colonize ephemeral grasslands immediately after rains when the neonate larvae can disperse and feed on new vegetative growth. Shortly after hatching, 93% of first instar larvae used fine silken threads for aerial dispersal in 0.5 m s‐1 air currents and 43% were blown a distance of more than 1.0 m. In the field, sticky traps caught larvae dispersing in all directions from a central source, and indicated that approximately 30% were transported 2 m after 7 days of light to medium breezes. Terminal velocities of newly hatched larvae were 20–130 cm s‐1, depending on the length of the trailing thread.
The Southern Oscillation and variations in waterfowl abundance in southeastern Australia
Authors: NORMAN F. I. , NICHOLLS N. 
Published: July 2006

AbstractMean sizes of duck hunters’ bags on the opening days of annual waterfowl seasons at selected wetlands in southeastern Australia, between 1972 and 1990, are correlated with an index of the Southern Oscillation (SOI). Simple correlations exist between bag sizes at the various sites, and the mean bag size in Victoria shows a positive relationship with that obtained at Barrenbox Swamp, New South Wales. Bag sizes are most significantly correlated with monthly SOI some 25–28 months before the eventual start of an open season. Interannual variations in rainfall in eastern Australia are generated by the El Niño–Southern Oscillation, which is monitored by the SOI, and the waterfowl populations respond to changing water and wetland availability. Accepting that annual bag sizes represent an index of waterfowl abundance, the regional population size may be related to climatic events associated with changes in SOI values. Further consideration of the SOI and indices of waterfowl abundance may allow variations in legislative or management options well in advance of individual open seasons.
Effects of sodium chloride and melibiose on the in vitro growth and sporulation of Frankia strain HFPCcI3 isolated from Casuarina cunninghamiana
Authors: BURLEIGH STEPHEN H. , DAWSON JEFFREY O. 
Published: July 2006

Abstract The in vitro growth and sporulation of Frankia isolate HFPCcI3, a nitrogen‐fixing symbiont of Casuarina, was inhibited by both the toxic and osmotic effects of sodium chloride. This was demonstrated by comparing HFPCcI3 halotolerance with its tolerance to metabolically neutral melibiose osmoticum at sodium chloride and melibiose concentrations from 0 to 500 mmol L‐1. The osmotolerance of this strain is similar to that of other Frankia strains, whereas the halotolerance of this strain is greater than that reported for Frankia strains isolated from actinorhizal plants from moist, temperate regions lacking sodic soils. This finding suggests that differential strain‐specific mechanisms are involved in Frankia's ability to tolerate dry versus sodic soil conditions and has important implications for the microbial ecology of soils supporting Casuarina spp.