bluuebunny/crossref_metadata_2025 huggingface dataset:
Mineralization of soil nitrogen in three forest communities from the New England region of New South Wales
Authors: RICHARDS B. N. , SMITH J. E. N. , WHITE G. J. , CHARLEY J. L.
Published: July 2006

Nitrogen (N) mineralization rates and the temperature response patterns of mineral N production in surface (0–7.6 cm) soils were compared in laboratory incubation studies based on disturbed, composite samples. Seasonal variation in the field levels of mineral N, and mineralization potential of intact (7.6 × 5.6 cm diameter) soil cores, were also investigated.

Ammonification proceeded rapidly in each soil. Nitrification did not occur in grassy forest (GF) soil but was active in both layered forest (LF) and mossy forest (MF) soils, especially the former. Total mineral N production was greatest in MF and least in LF.

Ammonification in disturbed samples was maximal at 50°C in all three soils with a secondary peak at 10°C in LF soil. Nitrification in LF and MF soils was most rapid at 25°C. Several species of ammonifying bacteria with different temperature optima were isolated, indicating that the process of ammonification is a composite of the activities of a variety of decomposer microbes.

Mean field levels of mineral N and NH4–N throughout the year were greatest in MF and least in LF. Seasonal fluctuations in NH4–N were evident, concentrations being universally low in mid‐winter (about 1.5 μgg‐1), increasing to a maximum in late summer (about 5 μg g‐1 in LF: 16–18 μg g‐1 in GF and MF). Field levels of NO3–N were more constant and never more than 5 μg g‐1 in any community. Both total mineralization and ammonification in intact cores were greatest in MF and least in LF while nitrification was greatest in LF and almost negligible in GF, thus confirming the results obtained with disturbed samples. The potential for mineralization was large in mid‐winter when the amount of mineral N was very low, and small in late summer when field levels were higher: this is interpreted as indicating that seasonal climatic factors regulate the availability of substrates for decomposers.

Spatial variability in field levels of mineral N and mineral N production in the laboratory was evidenced by significant ‘sampling site’ effects in each community: however, at the sampling intensity used, the presence of bark mounds around Eucalyptus saligna trees could not be shown to affect these attributes.

The inability of GF soil to nitrify when incubated in the laboratory could not be ascribed to a high C/N ratio, low pH, lack of substrate ammonium, or a low population of autotrophic nitrifying bacteria. No attempt was made to investigate the presence of allelopathic nitrification inhibitors. No evidence was obtained to support the view that nitrification is atypical of climax communities in situ. The most productive forest (LF) had the greatest capacity to nitrify and the least productive community (GF) the smallest capacity to do so.
Population dynamics of the tropical annual grass Sorghum intrans in relation to local patchiness in its abundance
Authors: ANDREW M. H.
Published: July 2006

Communities of Sorghum intrans, a tropical annual grass of north‐west Australia, contain sparse patches several metres in diameter within otherwise dense swards. These patches are persistent for at least ca. 4 years, despite the fact that these species are annuals which lack a persistent seed‐bank.

Three possible causes of the sparse patches were investigated at a site near Darwin: loss of viable seeds through granivory or death; high plant mortality; or poor fecundity. This was done by augmenting the seed‐banks of S. intrans in the sparse patches, and thinning stands of seedlings in the surrounding, naturally dense areas, and comparing the results of these perturbations with controls.

Granivory did not appear to be a cause of the sparse patches. Furthermore, the seeds in the sparse patches did not become inviable over the dry season. Compared with the plants of S. intrans in the naturally high‐density areas, survival of the plants in the augmented patches was not reduced, but vigour and seed production were. Conversely, plants in the thinned stands had a higher survival rate and very much greater vigour and seed production than plants in either the undisturbed patches or the undisturbed surrounding areas. Biotic constraints to plant growth such as grazing and disease appeared to be unimportant.

These sparse patches result from poor site potential for S. intrans which limits its growth and reproductive output.
The invasion of Kangaroo Island by alien plants
Authors: KLOOT P. M.
Published: July 2006

The numbers of alien plant species naturalized on Kangaroo Is., South Australia, at different times were examined and compared with those from an adjacent part of the mainland, the Encounter Bay area. The establishment of new species appears to have been accelerating and the rate of acquisition is around 50% faster on the mainland than on the island. Flinders’ Chase, a National Park at the western end of Kangaroo Is., has been acquiring alien species more slowly than the rest of the island. Land use patterns are a more effective barrier to the invasion of alien plants than a 15 km stretch of sea.
Soil chemical properties as related to forest succession in a highland area in north‐east Tasmania
Authors: ELLIS R. C. , GRALEY A. M.
Published: July 2006

The relationship between vegetational type and a number of soil chemical factors was examined in secondary successions from fire‐maintained eucalypt/grass to climax rainforest communities growing on uniform granitic soil parent material. Canonical variates analysis, which utilized the following variables: pH; loss on ignition; total N, P, K, Ca, and Mg; cation exchange capacity and exchangeable Ca, K, and Mg; and potentially mineralizable N, revealed close overall similarity between surface soils of adjacent types, and significant differences among those of types distant from each other in the successional sequences. Exchangeable Ca, mineralizable N, total N. P, and Mg, and pH all differed significantly among soils of the vegetational types. However, the only identifiable gradients in soil properties that were detected within a successional sequence were in total and mineralizable N, which tended to increase, and pH, which generally tended to decrease with progression towards the climax vegetation. Nitrification was promoted by the presence of Acacia dealbata and apparently inhibited by the presence of Leptospermum lanigerum; it was more rapid in soils beneath late successional vegetation than in those from climax vegetation or early stages of succession, and was inhibited in soil from old (> 200 years) grassland. It was concluded that differences among soils in chemical composition and rates of mineralization of N were due to differences in species composition of the vegetational types that they carried for the time being.
Response of Callitris intratropica R.T. Baker & H.G. Smith to fire protection, Murgenella, Northern Australia
Authors: BOWMAN D. M. J. S. , WILSON B. A. , DAVIS G. W.
Published: July 2006

Pattern analysis of stems > 10 cm d.b.h. on 514 one‐tenth ha quadrats showed that Callitris intratropica has a clumped distribution throughout the more uniformly distributed Eucalyptus forests at Murgenella in Northwest Arnhem Land. Callitris clumps are typically located on sites with sandy soils. Eucalypts occur within Callitris clumps.

Fire suppression over the past 18 years has allowed some C. intratropica to establish on Eucalyptus forest sites with fine textured soils It is argued that distribution of Callitris preceding fire management was controlled by the interactive effects of fire, soils and understorey vegetation. High grass fuel loads (and thus intense fires), and competition are thought to have previously limited establishment of C intratropica on fine textured soils. Early dry season burning by Aboriginals may also have been important in limiting fire intensities and accumulation of fuel in Callitris stands. Dry electrical storms commonly cause fires prior to the summer rains. Such wildfires did not completely kill stands of Callitris saplings or trees at Murgenella. Survivors were found to be significantly bigger and to have thicker bark than the dead stems. Sapling size is related to age and density, thus fire may be an important mechanism in thinning heavily stocked stands.

The continuous regeneration of Callitris and Eucalyptus is in marked contrast to the inhibition of Pinus caribaea recruitment following fire protection in the monsoonal neotropics. The lack of seral tree species in northern Australia suggests an equilibrium between forest distribution and the physical environment.
Modelling development of larvae and pupae of Pterohelaeus darlingensis Carter with Podolsky phenocurves
Authors: ALLSOPP P. G.
Published: July 2006

Podolsky phenocurves were constructed to model the development of larvae and pupae of Pterohelaeus darlingensis under fluctuating temperatures. The models lny =9.90 — 1.78lnx and lny = 8.71 — 1.93lnx give the best estimates for larval and pupal development, respectively. These models are shown to be inferior to those derived with the DEVAR program for modelling development in fluctuating temperatures.
Soil of the nest‐mound of the seed‐dispersing ant, Aphaenogaster longiceps, enhances seedling growth
Authors: ANDERSEN ALAN N.
Published: July 2006

Although a major benefit of myrmecochory in the Australian environment is believed to be the targeting of seeds to nutrient‐enriched ant nests, there is very little direct evidence for this. Here I report that, compared to control soil, soil from nest mounds of Aphaenogaster longiceps enhances the growth of seedling roots and shoots by about 50% in glasshouse trials. This benefit of nutrient‐enrichment, however, probably only occurs when seeds are dispersed by ants that construct large, long‐lived, nest mounds. This is very often not the case, and there is now increasing evidence that distance dispersal is often the major benefit of myrmecochory in Australia.
Rattus colletti (Rodentia: Muridae) in the Australian wet‐dry tropics: Seasonal habitat preferences, population dynamics and the effects of buffalo (Bubalus bubalis)
Authors: FRIEND G. R. , DUDZINSKI M. L. , CELLIER K. M.
Published: July 2006

Population dynamics and habitat preferences of the dusky rat, Rattus colletti, were examined in the seasonal wetlands of the South Alligator River. Northern Territory, between late 1979 and 1982. Demographically, the species is characterized by short‐term seasonal shifts between habitats superimposed on a longer‐term irregular pattern of prolonged breeding and population irruption, followed by periods of relative rarity. These patterns are determined by the train of climatic events. The flexible life history strategy and movement patterns of R. colletti reflect fine‐scale adaptation to a climatic regimen which is markedly seasonal, but also highly variable between years in the amount and temporal patterning of rainfall.

The distribution of R. colletti amongst vegetation types is influenced by two sets of environmental factors, both reflecting a gradient in elevation, soil type and vegetation. The primary factors are vegetative cover and height, and the extent and duration of flooding; the secondary set comprises buffalo‐induced features such as the degree of pugging and grazing. These factors are interrelated, and their relative importance to R. colletti varies greatly between seasons.

Feral buffalo appear to exacerbate the harsh effects of the wet and dry seasons. The removal of these animals may ameliorate environmental conditions considerably, both temporally and spatially, resulting m generally higher, more stable and spatially less variable populations of R. colletti.
Size distribution and coning behaviour of the Australian cycad Lepidozamia peroffskyana
Authors: ORNDUFF ROBERT
Published: July 2006

Leaf numbers as an estimate of sexual maturity and presence of current and previous season's cones were determined for individuals sampled in two populations of Lepidozamia peroffskyana near Dorrigo and Sealy Lookout, New South Wales, Australia. Average leaf numbers of known males and females were not significantly different. Average leaf numbers of plants showing no evidence of coning were lower than for coning individuals, suggesting that both populations contain substantial numbers of immature plants. About half the plants in both populations were putatively mature, but only 12% of such individuals in the Dorrigo population bore current season's cones compared with 51% in the Lookout population; 28% of the Dorrigo plants and 5% of the Lookout plants showed evidence of prior coning. Thus, in each population, not all mature plants produce cones during a given reproductive episode. The proportion that does so appears to vary from year to year. Cone production by individuals of each sex appears to be separated by several‐year intervals. The few plants with current season's cones in the Dorrigo population prevented determining a phenotypic sex ratio there, but for the Lookout population it was not statistically different from 1:1 male:female. The weevil Tranes lyterioides was abundant on two male cones that were entering the pollination phase in the Lookout population, suggesting that it may be involved in the pollination of this cycad.
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

Plant 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

This 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

Plants 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

A 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

An 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

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.
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

This 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

This 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

Recent 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

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

The 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

The 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

Mean 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

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.
Effects of fire regimen on two species of epiphytic orchids in tropical savannas of the Northern Territory
Authors: COOK G. D.
Published: July 2006

The effect of four fire regimens (early dry season annual, late dry season annual, early dry season biennial, unburnt) on the numbers of epiphytic orchids in a savanna community in Kakadu National Park was investigated. These fire regimens had been maintained on I ha plots for 16 years. Two species of epiphytic orchid were present — Cymbidium canaliculatum and Dendrobium affine. The numbers of Cymbidium plants were insufficient to enable statistical analysis, but plants were present in the unburnt, early annual and early biennial fire treatments. Dendrobium occurred in substantial numbers irrespective of fire treatment, but the extent of colonization of all available host trees was greater in the unburnt than the burnt treatments.

The lower numbers of Dendrobium plants in burnt treatments was due to a lower proportion of potential host trees being colonized and a lower number of orchids on each colonized tree. The proportion of small trees colonized was markedly lower in burnt treatments. Frequent fires late in the dry season may prevent recruitment of the main host species. Eucalyptus tectifica. The survival of orchids despite frequent fires depended on the availability of relatively protected sites for colonization and the ability of the orchids to withstand some fire damage.
The grazing effect of limpets on the macroalgal community of a rocky intertidal shore
Authors: Beovich E. K. , Quinn G. P.
Published: July 2006

Abstract
Abundance of macro‐algae in the mid‐littoral zone on a Victorian intertidal rocky shore varied seasonally, algae being rare in Summer and common in Winter and Spring. Field experiments demonstrated that, of two species of grazing limpets (Cellana tramoserica and Siphonana diemenensis), only Siphonaria had a major effect on the abundance of foliose algae (e.g. Scytopsiphon lomeniarid) and neither species had a great effect on the encrusting algae (Ralfsia spp.). There was no evidence of competition for food between the two species of limpets, in contrast with results found for similar species in New South Wales.
The life history and abundance of the introduced earthwormsAporrectodea trapezoidesandA. caliginosa(Annelida: Lumbricidae) in pasture soils in the Mount Lofty Ranges, South Australia
Authors: BAKER G. H. , BARRETT V. J. , GREY‐GARDNER R. , BUCKERFIELD J. C.
Published: July 2006

AbstractThe introduced earthworms,Aporrectodea trapezoidesandAporrectodea caliginosa, are common in agricultural soils in southern Australia. The seasonal abundances of these species were monitored in five pastures in the Mount Lofty Ranges, South Australia. Highest numbers occurred from winter to early spring: densities of up to 407 and 446 m−2were recorded forA. trapezoidesandA. caliginosa, respectively. Adults were restricted to winter and spring, when breeding occurred. Subadults and juveniles survived summer.Aporrectodea trapezoidesandA. caliginosawere abundant in the surface layers of the soil (0–10 cm depth) for between 3 and 7 months (autumn to spring), when soils were moistest. During summer, most individuals were found > 20 cm below the surface where they were inactive, coiled tightly within sperical chambers. The abundance ofA. trapezoidesandA. caliginosavaried within and between pastures. Numbers were lowest where the clay content of the soil was low. A dipteran parasite attacked a small proportion ofA. trapezoidesat one site in spring.
Soil temperatures during bushfires in semi‐arid, mallee shrublands
Authors: BRADSTOCK R. A. , Auld T. D. , ELLIS M. E. , Cohn J. S.
Published: July 2006

Abstract
Soil temperatures were measured during 11 experimental fires in semi‐arid mallee shrublands in central NSW. Sensors were placed at depths from 1–10 cm beneath the soil surface in three fuel types; litter beneath Eucalyptus shrubs, live hummocks of the grass Triodia irritans and litter beneath shrubs of Acacia species. Weights of these fuels per unit area were determined.

Maximum soil temperature and its duration were related to fuel type and depth. Mean weights of Eucalyptus and Triodia fuels were similar (0.35 kg m−2), while there was less Acacia fuel (0.1 kg m−2). Highest maximum temperatures were registered under Eucalyptus litter (e.g. 140°C at 2 cm). Maximum temperatures under Triodia and Acacia litter were similar (e.g. 60–70°C at 2 cm). Durations were examined in two temperature classes (60–120 and > 120°C) chosen to represent threshold for stimulation of germination and mortality, respectively, of soil‐stored seeds. Temperatures between 60 and 120°C were recorded only between 0–2 cm soil depth for Acacia and Triodia (one exception at 4 cm). No temperatures >120°C were recorded for these fuel types. Temperatures between 60 and 120°C were recorded to 5 cm depth under Eucalyptus fuels while putative lethal temperatures for seeds occurred occasionally at 0–2 cm depth.

The results indicated greatest potential for stimulation of germination and death of buried seeds under Eucalyptus fuels, although the level of variability of temperature was highest under Eucalyptus fuels. Despite similar fuel loads, differences between temperatures under Eucalyptus and Triodia fuels reflected the influence of the depth of the fuel bed, with Triodia hummocks constituting a deep fuel bed and Eucalyptus litter a shallow fuel bed.
Environmental relations and ecological responses of some higher plant species on rock cliffs in northern Tasmania
Authors: COATES F. , Kirkpatrick J. B.
Published: July 2006

Abstract
Gravity, moisture availability and shade exert a major control over the distributions of vascular plant species on sandstone cliffs in the Great Western Tiers, northern Tasmania. The vegetation is dominated by ferns, some of which are almost always restricted to cliffs, with invasion of shrub and tree species where soil has been able to accumulate. Although it might be expected that species commonly found over a wide range of vegetation types could displace obligate cliff dwellers, this potential is rarely fulfilled. The vertical nature of the environment precludes the loss of cliff obligates, as soil‐vegetation mats peel off in part of a truncated and cyclic successional process. Experimental work and field monitoring of growth and mortality in single species and mixed stands showed that the cliff obligate fern Blechnum vulcanicum (Blume) Kuhn is slower growing, more drought resistant and less responsive to fertilizer than its non‐obligate associate, B. wattsii Tind.
Links between ecology and ecophilosophy, ethics and the requirements of environmental management
Authors: FAIRWEATHER P. G.
Published: July 2006

Abstract
This paper concerns the ways that our philosophical attitudes to the environment can influence the appropriateness of methodologies for solving environmental problems. Sometimes a public perception is expressed that science takes scant regard of the concerns of the people affected. Is it possible for scientists and managers to respond to such concerns and still fulfil the logical and methodological rigour that their discipline demands? I believe we have to address fundamental issues of definitions and meaning before useful debate can occur among parties interested in environmental decision‐making. Delving into the ideas behind our everyday practices of environmental management should promote re‐evaluation of our beliefs, attitudes and concerns about nature.

I examine environmental science from both ethical and managerial perspectives. I explore how our assumptions and attitudes might influence ecology, in particular issues raised by environmental impacts and conservation. The major points argued here are:

 Any legal requirements of environmental investigations must be met, but perhaps we should act more in line with the spirit of legislation.

 The managerial imperatives of environmental investigations need to be examined closely because of widely perceived problems with the use of science in impact assessment. We must change either our methods of assessment or the regulations and administration of environmental impact assessment (EIA).

 Science is not paramount in the processes of environmental decision‐making. We need to be aware of how psychosocial factors affect the ultimately political decisions about environmental problems.

 Philosophy and ethics offer a range of perspectives that may benefit ecology. Scientists need to be aware of these just as they should be of their own leanings about how we treat nature.

 Scientists need to translate social concerns or demands about the environment into properly defined scientific questions, and then study them as a matter of urgency.

 Ecology needs to guide ecophilosophers and environmental ethicists as to how nature works, why we expect variability in ecosystems, what is naturalness, and other issues where a scientific understanding of nature has progressed beyond the point where these observers of ecology have so far taken inspiration.
Regeneration and growth of coolibah, Eucalyptus coolabah subsp. arida, a riparian tree, in the Cooper Creek region of South Australia
Authors: ROBERTS JANE
Published: July 2006

Abstract
Regeneration patterns of Eucalyptus coolabah Blakely & Jacobs subsp. arida (Blakely) L. Johnson & K. Hill (coolibah), a riparian tree of inland Australia, were inferred from size classes at two locations in South Australia; part of the floodplain of Cooper Creek and a swale in the Strzelecki Desert. These had contrasting water regimes; Cooper Creek floods on average once every 5–6 years whereas the swale has a continual water supply from a bore. A peak in size class distribution showed a regeneration event at each location but at different times. The one in the swale was more recent and was dated to the mid‐1970s using aerial photography. Young (< 5 m tall) trees, interpreted as recent regeneration, were concentrated on specific topographic features, the top of a steep riverbank and a sand mound separate from the main dune system. Access to these features would have been difficult after flooding suggesting regeneration is dependent on protection from introduced herbivores. Field observations of reproductive status and canopy die‐back showed coolibah condition was better in the swale. The relatively poorer condition of floodplain coolibahs was attributed to saline soils compounded by drier conditions rather than age.
Size‐dependent reproduction in Australian alpine Ranunculus
Authors: PICKERING CATHERINE M.
Published: July 2006

Abstract
The effect of plant size on reproduction in four species of alpine Ranunculus (R. muelleri, R. dissectifolius, R. graniticola and R. niphophilus) was investigated in two sites over two seasons in the field on a total of 190 plants. The effects of plant size (number of leaves) and number of flowers on the number of anthers, ovules and seed per flower and per plant were determined. There was a positive relationship between several measures of reproduction and plant size in all four species, indicating that reproduction is size‐dependent. All the results indicate that the main factor controlling the amount of seed produced by alpine Ranunculus is the size of the plant. Specifically, bigger plants produced more seed by producing more flowers, not by producing more ovules per flower, or higher seed set per flower. Correspondingly, bigger plants produced more anthers by producing more flowers, rather than by producing flowers with more anthers. The total number of seeds produced by a plant was directly proportional to plant size in the four species. Therefore, reproductive effort should not vary with plant size in the four species.