bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mechanisms for locating resources in space and time: Impacts on the abundance of insect herbivores
Authors: Jones Rhondda E. 
Published: March 2003

AbstractHerbivorous insects have the problem both of locating appropriate host plants and ensuring that the plant‐feeding stages of their life cycles are synchronized with the times when those hosts provide a high‐quality food resource. Because the taxonomic range of potential hosts is generally narrow, and the temporal window when those hosts are suitable is often relatively short, developmental (especially diapause) and dispersal mechanisms may be critical factors in determining whether or not a species population is successful in a particular plant community. The present paper considers the impact of diapause and dispersal mechanisms on the ability of insect herbivores to cope with two attributes of their host plants: (i) the diversity of the plant community within which the hosts are located; and (ii) the seasonal predictability of host suitability. Some common dispersal mechanisms used by insect herbivores are much more appropriate to low‐diversity than to high‐diversity plant communities and, similarly, some diapause cues are appropriate only to highly predictable plant phenology. Both agriculture and silviculture characteristically manipulate both these attributes of plant communities, that is, in order to make the human use of plants more efficient, cultivation strategies normally both reduce plant species diversity (often to a condition approaching monoculture) and increase the predictability of plant developmental patterns. Consequently, major pest species in managed systems may not be those that are most common in natural systems, and may be difficult to predict in advance.
Can stable carbon isotopes (δ13C) in soil carbon be used to describe the dynamics of Eucalyptus savanna–rainforest boundaries in the Australian monsoon tropics?
Authors: Bowman D. M. J. S. , Cook G. D. 
Published: March 2003

AbstractThe history of isolated patches of monsoon rainforest within large tracts of Eucalyptus
savanna is poorly understood because of the scarcity of reliable palaeoecological
records in the Australian monsoon tropics. Elsewhere in the world, the ratio of the
stable isotopes 13C to 12C (δ13C) in soil
organic matter has shed light on the dynamics of rainforest–savanna boundaries
because tropical grasses with the C4 photosynthetic pathway have a distinct δ13C
signature (–17 to –9‰) compared with that of woody plants with
the C3 photosynthetic pathway (–32 to –22‰). In order to determine
the magnitude of the variation in δ13C, unreplicated soil profiles
were sampled beneath different vegetation types on three boundaries between Eucalyptus
savanna and rainforest that were both growing on Tertiary age laterite parent material.
Replicated (n = 3) soil profiles, which were also derived from Tertiary age
laterite, were sampled from beneath: (i) dense stands of African grasses within a
frequently burnt Eucalyptus savanna; and within the same long unburnt Eucalyptus
savanna, (ii) patches of African and natives grasses and (iii) clumps of Acacia
trees. The strongly negative δ13C values of soil organic matter
derived from the frequently burnt and long unburnt grassy understoreys in the Eucalyptus
savannas showed that a considerable amount of the soil carbon was derived from C3
(woody) species despite the presence of a ground layer dominated by C4 grasses. However,
a feature of these data was the considerable variability among the three ‘replicate’
profiles. The surface soil samples from beneath three clumps of Acacia trees
in the unburnt Eucalyptus savanna had much less variable δ13C
values and were similar to two of the three monsoon rainforests sampled. The pattern
of δ13C values from unreplicated soil profiles from different vegetation
types across three rainforest boundaries was also very variable and not always obviously
related the known disturbance history of the extant vegetation. Given the considerable
variability within and between vegetation types with contrasting disturbance histories,
it is concluded that the use of carbon stable isotopes to advance understanding of
the dynamics of rainforest and Eucalyptus savanna boundaries will require
further development, such as determination of the 14C age and δ13C values of different soil carbon fractions.
Population dynamics of an endangered heathland shrub,Epacris stuartii(Epacridaceae): Recruitment, establishment and survival
Authors: Keith David A. 
Published: March 2003

AbstractThe only known population of the endangered shrubEpacris stuartiiStapf was studied from 1994 to 2001 using demographic census techniques. The effects of substrate, a fire and a storm on the emergence and survival of seedlings and the survival of established plants of different sizes were examined using failure‐time analyses and logit‐linear models. Ninety‐five per cent of seedling emergence was delayed until the second post‐fire spring, an unusual response among species with persistent soil seed banks. Mortality of seedlings was extreme compared with larger‐seeded species, but diminished significantly with age. Seedling mortality varied significantly between substrates: 40% of seedlings persisted for more than 5 years in mineral soil, whereas less than 10% lived more than a year on rock and intermediate substrates. However, seedling numbers and local densities were lower on soils than other substrates. Background mortality of established plants was lower on soil and intermediate substrates (0.5% per year) than on rock (3% per year). Small plants may be more susceptible than large plants on rock, but not on soil. Both the fire and the storm resulted in elevated mortality of established plants. The population exhibited a variable response to fire, with plants on rock and intermediate substrates behaving as obligate seeders, whereas plants in soil resprouted. This appears to be the first report of microhabitat variation in fire response at sympatric scales. The effects of the storm were apparently independent of substrate and plant size. The essentially independent disturbance regimes comprising recurring fires and storms are likely to have a profound effect on the long‐term population dynamics ofE. stuartii. Over the 7‐year census period, recruitment has failed to compensate for mortality, resulting in a 30% net decline in the population. The demographic census has proved to be crucial in the detection and diagnosis of this decline.
Habitat selection by the small dasyurid Ningaui yvonneae (Marsupialia: Dasyuridae) in South Australia
Authors: Bos D. G. , Carthew S. M. , Lorimer M. F. 
Published: March 2003

AbstractThis study investigated the habitat preferences of Ningaui yvonneae, a small,
nocturnal insectivorous marsupial of the semi‐arid regions of southern Australia.
Habitat composition was assessed at both the local (trapping grid) and trap scale.
Multiple linear regression revealed a significant positive relationship between captures
of N. yvonneae and the abundance of hummock grass (Triodia irritans)
at the local scale. At the trap scale, the interaction between Triodia irritans
and shrubs was found to be significant. This is thought to reflect the importance
of the availability of cover to ningauis. Triodia was an essential component
of that, probably because it affords greater protection from predators. This study
provides quantitative habitat data that supports the contention of other studies
that N. yvonneae has a strong positive association with Triodia spp.
Ecological processes and trophic status of two low‐alpine patterned mires, south‐central South Island, New Zealand
Authors: Dickinson Katharine J. M. , Chagué‐Goff Catherine , Mark Alan F. , Cullen Louise 
Published: March 2003

Abstract  Vegetation and environmental patterns, and associated ecological processes, were quantified from 42 sites on several transects in each of two extensive (5 and 220 ha) low‐alpine patterned mires in the same region of south‐central New Zealand. Plant communities, as derived from multivariate analyses, were correlated with 15 physical and chemical environmental factors. Various measures of water availability and chemistry were consistently the most significant factors in relation to vegetation patterns in both mires. In the smaller mire, plant cover adjacent to pools, which were partly or completely drained through underground tunnels, dominated the overall correlations. The nutrient status of surface water had a consistent negative relationship with water availability. No consistent spatial or temporal patterns were found in the concentrations of Ca, Mg, K or Na, nor pH or conductivity in pool water. Evaporative enrichment of cations on the surface of both mires was noted, with levels consistently higher in surface than in adjacent pool water. The somewhat higher nutrient status in the smaller mire may be a result of the size and/or the amounts of run‐off from the surrounding slopes onto the mire surface or through the underground pipe system. Hydrogen (D) and oxygen (18O) isotopic compositions in water from pools, the mire surface and below ground from the smaller mire, suggested that there was negligible mixing of evaporation‐enriched surface water with groundwater. Differences in overall nutrient levels in the two mires were relatively small and indicative of mesotrophic or marginally ombrotrophic status for these mires. Although of international significance, the wetland complex currently has inadequate formal protection. Possible options are assessed.
Effects of fire intensity on plant species composition of sandstone communities in the Sydney region
Authors: Morrison David A. 
Published: March 2003

Abstract  Fire intensity measures the heat output of a fire, and variation in fire intensity has been shown to have many effects on the demography of plant species, although the consequent effects on the floristic composition of communities have rarely been quantified. The effects of variation in fire intensity on the floristic composition of dry sclerophyll vegetation with different fire histories near Sydney was estimated. In particular, differences in species abundance of woodland and shrubland communities subjected to four fire‐intensity classes: unburnt, low intensity (<500 kW m−1), medium intensity (500–2500 kW m−1) and high intensity (>2500 kW m−1) were examined. The samples had a standardized previous fire frequency and season, thus minimizing the effects of other aspects of the fire regime. There was a clear effect of fire intensity on the relative abundances of the vascular plant species, with increasing intensity of the fire producing vegetation that was increasingly different from the unburnt vegetation. This pattern was repeated in both the woodland and shrubland vegetation types, suggesting that it was not an artefact of the experimental conditions. However, the effects of fire intensity on floristic composition were no greater than were the differences between these two similar vegetation types, with variation in fire intensity accounting for only approximately 10% of the floristic variation. Nevertheless, the effects of fire intensity on the abundance of individual species were consistent across taxonomic groups, with the monocotyledon and Fabaceae species being more abundant at higher than lower intensities, the Proteaceae and Rutaceae more abundant at intermediate intensities, and the Epacridaceae more abundant at lower rather than higher intensities. The number of fire‐tolerant species increased with increasing fire intensity, and those fire‐tolerant species present were most abundant in the areas burnt with medium intensity. The number of fire‐sensitive species did not respond to fire intensity, and those species present were most abundant in the areas burnt with low intensity. This suggests that either fire‐sensitive species respond poorly to higher fire intensities or fire‐tolerant species respond poorly to lower fire intensities, perhaps because of differences in seed germination, seedling survival or competition among adults.
Assessment of the diversity and abundance of terrestrial mangrove arthropods in southern New South Wales, Australia
Authors: Meades Louise , Rodgerson Louise , York Alan , French Kris 
Published: March 2003

Abstract  The diversity and abundance of arboreal and flying arthropods, in three mangrove patches along the south coast of New South Wales, Australia, was investigated to determine the degree of spatial variability in the assemblages among patches. Intercept traps and restricted canopy fogging were used to sample the communities at Minnamurra, Bonnievale and Kurnell. Twelve orders of arthropods were detected, incorporating 252 morphospecies. Abundance, species richness and species composition were very similar across all patches, the variation being much smaller than expected. These findings suggest that the composition of the arboreal and flying fauna associated with mangrove patches are very similar among patches, but preliminary results also showed that species composition could be highly variable within a patch.Variation between the trapping methods was large, as expected. Intercept trapping and restricted canopy fogging techniques were found to sample different suites of species and therefore complement each other well in sampling programs. Cumulative species curves differed between time periods but generally were flatter for intercept traps than for restricted canopy fogging. Results suggested, for a given level of effort, intercept traps caught a more representative sample of the species composition available to them.
Distribution of Phytophthora cinnamomi at different spatial scales: When can a negative result be considered positively?
Authors: Pryce Josephine , Edwards Will , Gadek Paul A. 
Published: March 2003

Abstract  In October 1999, patches of dead and dying trees were identified in rainforest vegetation throughout the Tully Falls area in north Queensland, Australia. Previous incidents of patch death in the region had been attributed to Phytophthora cinnamomi. The distribution of P. cinnamomi was assessed by testing for its presence in seven sites displaying signs of dieback and seven sites that appeared healthy. Each site was a circular quadrat, 20‐m radius (total area = 1256.6 m2). Within each quadrat, two perpendicular line transects were constructed. A single soil sample (250 g) was taken at the centre point and at 1‐m intervals along each transect. All soil samples were tested for the presence of P. cinnamomi using a combination of lupin baiting, subsequent culturing and microscopic identification. Of the 1134 samples, 783 recorded positive responses. The mean number of positive responses was not significantly greater in patch death sites than in control sites, suggesting that at this scale of resolution the distribution of P. cinnamomi was uniform. However, at spatial scales of 1‐m intervals across transects the distribution of P. cinnamomi was random.
Adult aquatic insects: Potential contributors to riparian food webs in Australia's wet–dry tropics
Authors: Lynch Romeny J. , Bunn Stuart E. , Catterall Carla P. 
Published: March 2003

Abstract  Changes in the abundance and biomass of aquatic and terrestrial aerial insects with distance (mid‐stream, 0, 10–15 and 160 m) from lowland streams were examined across the dry season landscape in Kakadu National Park, northern Australia. Malaise traps and sticky intercept traps were used to sample the insects at four streams, spaced over an area of 1650 km2. Malaise and intercept catches were dominated by Diptera (flies and midges), both numerically and by biomass. Chironomid midges were the most abundant taxon, making up 43.4 and 51.0% of the malaise and intercept trap catches, respectively. However, most chironomids were small (less than 3 mm body length), contributing 34.9% to intercept trap biomass, but only 5.2% in malaise traps. Ceratopogonid midges and caddisflies (Trichoptera) accounted for most of the remaining adult aquatic insects. Major terrestrial components were Diptera and Hymenoptera in malaise traps and Coleoptera and Diptera in intercept traps. The total abundance and biomass of insects were much greater over streams and along the water's edge than in riparian (10–15 m) and savanna (160 m) habitats primarily because of the presence of large numbers of adult aquatic insects. The abundance and biomass of terrestrial insects in malaise traps showed no relationship with distance, but intercept trap catches suggested slightly greater abundances over the water and at the water's edge. The great abundance of aquatic insects relative to terrestrial insects close to streams suggests that they have the potential to be an important component of the diets of riparian insectivores, and predation may be an important pathway by which aquatic nutrients and energy are moved into terrestrial food webs.
Trophic trickles rather than cascades: Conditional top‐down and bottom‐up dynamics in an Australian chenopod shrubland
Authors: Dawes‐Gromadzki Tracy Z. 
Published: March 2003

Abstract Despite continued interest in the relative roles of top‐down (predation) and bottom‐up (productivity) factors in structuring ecological communities, there have been few studies of diverse terrestrial arthropod systems. Top‐down theory predicts that decreased predator populations will result in increased herbivore populations and reduced plant populations. Bottom‐up theory predicts that a positive producer level response to nutrients will support greater herbivore and predator populations. Few studies simultaneously examine both theories. In the present study, the roles of predators and nutrients in structuring an Australian chenopod shrubland community were investigated, by using a complete 2 × 2 factorial design with three replicated plots with and without nutrients (fertilizer) and predators (two wolf spiders and two ants). Producer and major arthropod taxa responses, predator densities and soil nutrient levels were monitored from April 1996 to February 1998. In agreement with bottom‐up theory, the abundances of some plants and herbivores increased with the addition of nutrients, but most effects varied temporally and did not increase the abundances of any predator taxa. The effects of predator removal propagated down the food web to influence some herbivore and producer taxa but, in contrast to top‐down theory, effects were temporally dependent and varied in the direction of response within each trophic level. Predators and nutrients only interacted significantly to determine the abundance of one taxon. The findings suggest that true trophic cascades are not a primary determinant of chenopod community structure, with ‘conditional trophic trickles’ a better descriptor for the effects of predators and nutrients on this community. It is suggested that the expression of top‐down and bottom‐up effects is conditional on appropriate timing and extent of rainfall. The results provide further support for the theory that food webs are more complex in terrestrial than in aquatic systems, with abiotic and biotic heterogeneity, intraguild interactions and non‐consumptive interactions between adjacent trophic levels all confounding the classic consumptive interactions that are required for the expression of top‐down and bottom‐up forces.
Spatial ecology of arboreal snakes (Hoplocephalus stephensii, Elapidae) in an eastern Australian forest
Authors: Fitzgerald M. , Shine R. , Lemckert F. 
Published: March 2003

Abstract  Stephens' Banded Snakes (Hoplocephalus stephensii Krefft 1869) are large (to 1 m), highly arboreal elapid snakes, restricted to mesic forested areas along the eastern coast of Australia. Radiotelemetric monitoring of 16 individuals at Whian Whian State Forest in north‐eastern New South Wales over 25 months provided the first data on spatial ecology of this threatened taxon. Two major influences on movements by Stephens' Banded Snakes were identified: the distribution of large hollow‐bearing trees, and the avoidance of conspecifics. Radiotracked snakes were sedentary inside tree hollows for extended periods (mean = 8 days) during their active season, interrupted by occasional long (mean = 124 m) nocturnal movements to another shelter tree. Snakes travelled on the ground rather than within the canopy, and thus were potentially exposed to terrestrial predators. Although the home ranges of the radiotracked snakes overlapped substantially (mean = 27%), simultaneous occupancy of ‘shared’ shelter trees was less common than expected by chance. Hence, we conclude that adult Stephens' Banded Snakes generally avoid the presence of conspecifics. Snakes used from five to 30 shelter trees and home ranges of male snakes were larger than those of females (mean = 20.2 vs 5.4 ha). The large spatial scale of these movements, and limited overlap among individuals, means that a viable population of this taxon requires a large area of contiguous forest. This requirement may explain why the species has not persisted in small forest fragments.
Dispersal for distance? Acacia ligulata seeds and meat ants Iridomyrmex viridiaeneus
Authors: Whitney Kenneth D. 
Published: March 2003

Abstract  Ant seed dispersal distances are typically small, averaging less than 1 m in published studies. Here, a new record (180 m) for ant seed dispersal distance is reported, and preliminary observations are made on the interaction between meat ants Iridomyrmex viridiaeneus Viehmeyer (Hymenoptera: Formicidae) and diaspores of the sandhill wattle, Acacia ligulata A. Cunn. ex Benth. (Fabaceae) in Kinchega National Park, New South Wales (NSW), Australia. Iridomyrmex viridiaeneus moved diaspores over distances of 7–180 m (mean 93.9 m) from the source trees to their nests, removed the arils underground and discarded the seeds over a 3000‐m2 area surrounding the nest. A germination trial determined that the viability of discarded seeds was 40%, with 80% of the viable seeds in a dormant condition. Although the cumulative effects of I. viridiaeneus on A. ligulata recruitment require further investigation, this study and others raise the possibility that myrmecochorous systems in the Australian arid zone may be characterized by longer dispersal distances than those in other parts of the world. Long‐distance seed movement by ants lends credence to the hypothesis that distance dispersal (in contrast to directed dispersal) could be of benefit to myrmecochorous plants.