bluuebunny/crossref_metadata_2025 huggingface dataset:
Towards an explanation of the causes of the rarity of two Tasmanian Spyridium species
Authors: COATES FIONA , KIRKPATRICK J. B. , MINCHIN P. R.
Published: March 2003

Spyridium microphyllum (F. Muell. ex Reissek) Druce and Spyridium obcordatum (Hook. f) W. M. Curtis are narrow endemic shrubs which are confined to small parts of Tasmania, Australia, and are rare within their present ranges. Analysis of quadrat data from transects through populations of both species showed that at most individual sites the rare taxa occur in floristically and environmentally distinct situations. However, sites supporting the same species differ floristically and environmentally, with the only communality being a lack of dense tall shrub or tree cover. Both species are absent from many areas with closely similar physical environments and vascular plant species composition to those in which they occur. Thus, their current distributions cannot be explained by limitation to a rare habitat. Spyridium microphyllum appears to be susceptible to local extinction because it is an obligate seeder, is killed by fire, does not survive in taller, dense vegetation, and is not adapted for dispersal over the distances between its potential habitats. While S. obcordatum recovers vegetatively after fire, it also does not survive in dense taller vegetation, has limited dispersal ability and highly disjunct potential habitat. Both species may have been more widespread and competitive during cooler and drier times.
Fire regime, fire intensity and tree survival in a tropical savanna in northern Australia
Authors: WILLIAMS R. J. , COOK G. D. , GILL A. M. , MOORE P. H. R.
Published: March 2003

Dry season fires are a feature of the tropical savannas of northern Australia. As part of a landscape‐scale fire experiment, we examined the effects of fire regimes on tree survival in a tropical savanna in Kakadu National Park, northern Australia. The fire regimes were annual early dry season (June) fires, annual late dry season (September) fires, and, no fire (control). Prescriptive, experimental fires were lit annually, between 1990 and 1994, in replicate compartments, each 15–20 km2. In addition to the prescribed fires, however, one of the control compartments, which had been unburnt for seven years, was burnt by an unplanned, high intensity fire (~ 20 000 kW m−1) in September 1994. This provided an opportunity to compare the impacts on the tree stratum of frequent, prescribed burning at various intensities, and a single unplanned fire. In all fire regimes, stem survival was substantially lower than whole‐plant survival, and decreased linearly with increasing fire intensity. Significantly, stem death following the single, high intensity 20 000 kWm−1 fire (75%) was comparable to that of a regime of annual late dry season burning for five years, at an average intensity of c. 8000 kWm−1. In the high intensity unplanned fire, stem survival showed a non‐linear response to stem size, being least in the small (< 10 cm DBH) and large (> 40 cm DBH) size classes, and highest in the intermediate size classes. Stem survival was also species‐dependent, being higher in the dominant Eucalyptus miniata than in the subdominant, broad‐leaf deciduous trees. In the absence of fire for 5–10 years, the structure and composition of the tree stratum of these savannas tends to become more complex than in sites burnt more frequently, especially by high intensity fire. Such a long‐term absence of fire may be a conservation objective for some areas of savanna. However, build‐up of fuel to near maximal levels can occur in 2–4 years without fire. This may predispose the savannas to high‐intensity, late dry season fires. Whatever the fire‐management goal within a given patch of savanna, whether it be the prescribed use of fire on a biennial basis, or the exclusion of fire at a semidecadal scale, careful attention still needs to be given to the consequences of fuel build‐up in fire‐excluded sites.
Distributional patterning of terrestrial herpetofauna on the Wessel and English Company Island groups, northeastern Arnhem Land, Northern Territory, Australia
Authors: WOINARSKI J. C. Z. , HORNER P. , FISHER A. , BRENNAN K. , LINDNER D. , GAMBOLD N. , CHATTO R. , MORRIS I.
Published: March 2003

Forty‐four species of terrestrial reptiles and eight species of frogs were recorded from 60 continental islands of the Wessel and English Company groups off northeastern Arnhem Land, Northern Territory. Two gecko species,Oedura rhombiferandHeteronotia binoei, were present on the most islands (34 and 31, respectively), and occurred on islands < 5 ha. In contrast, agamids, pygopodids and varanids were absent from islands < 18 ha, and snakes and frogs were not reported from islands < 240 ha. Island size explained 82% of the variation in species richness for terrestrial reptiles, and 84% of that for lizards. The relationship was less good for (i) groups with generally uncommon species (notably snakes), for which sampling effort explained more variation, and (ii) groups with species which had relatively specific habitat requirements (notably frogs), for which island size and isolation factors were not especially relevant. For most taxonomic groups considered, isolation factors added little to the relationship between species richness and island size. Across all reptiles, larger species were found on fewer islands, and had larger island size thresholds. This relationship broke down with analysis restricted to the single most species‐rich family, Scincidae. Only 6 of the 20 most frequently recorded species showed significant variation in abundance among 8 vegetation types sampled by 226 quadrats across 40 islands. The number of species (alpha‐diversity) and total abundance of herpetofauna within quadrats was generally unrelated to island size; however, (with analysis restricted to islands on which they occurred) six individual species were significantly more abundant on smaller islands than on larger islands, with no species showing the opposite pattern. The islands’ herpetofauna is largely a relatively depauperate subset of that of the far more complex sandstone massif and escarpment of western Arnhem Land, especially missing species associated with rugged sandstone gorges, riparian areas, open forests, swamps and clay soils. Patterns in species richness and composition are explained by greater range of environments on larger islands allowing better retention of species since isolation and/or richer tallies at the time of isolation. The evidence suggests that there has been relatively little colonization, although at least two gecko species and one varanid may have moved reasonably frequently.
Rainfall and rats: Climatically‐driven dynamics of a tropical rodent population
Authors: MADSEN THOMAS , SHINE RICHARD
Published: March 2003

A five‐year mark–recapture study of dusky rats (Rattus colletti) on the Adelaide River floodplain, within the Australian wet–dry tropics, revealed substantial spatial and temporal variation in demographic characteristics (abundance, condition, and rates of survival, growth, and reproduction) of the rats. Our data suggest that annual variation in the intensity and timing of monsoonal rainfall during the ‘wet‐season’ is the main factor driving the demography of the rats. When total rainfall figures are modified to reflect the magnitude and duration of inundation of the floodplain each year, a link is evident between rainfall patterns and the rat population dynamics. Minor spatial variations in elevation (and hence, in the duration of inundation) across the floodplain engender large differences in rat growth rates, condition factors, survival rates, and the duration of reproductive activity each year. Because these rats have very high reproductive rates, small rain‐induced differences in the duration of their reproductive season (i.e. number of litters per year) can cause massive differences in subsequent rat abundances. Hence, rat numbers can be predicted from rainfall patterns during the preceding wet‐season. Similar links between rainfall, the duration of breeding, and fluctuations in abundance may typify many rodent populations in tropical and arid regions of the world.
Red crabs in rainforest on Christmas Island, Indian Ocean: No effect on the soil seed bank
Authors: GREEN PETER T. , HART ROGER , JANTAN JAMIL BIN , METCALFE DANIEL J. , O’DOWD DENNIS J. , LAKE P. S.
Published: March 2003

Red land crabs (Gecarcoidea natalis) are both abundant and widespread in intact rainforest on Christmas Island, Indian Ocean, occurring at densities of ~ 1 crab m–2. We used an on‐going exclusion experiment to test the hypothesis that through their activities as seed predators and soil disturbers, these omnivores are important determinants of the density and relative species abundance of seeds in the soil seed bank of undisturbed primary rainforest. After 6.5 y of continuous crab exclusion, there was no significant difference in the density of seeds in the top 3 cm of soil between the control (3671 ± 517 seeds/0.19 m2) and exclusion plots (3285 ± 801 seeds/0.19 m2), nor was there any significant treatment difference in relative species composition. There were also no significant treatment differences when Muntingia calabura, which accounted for 91.9% of all seeds in the seed bank, was excluded from the analyses. We attribute the lack of a significant impact of red crabs to their probable inability to handle the very small seeds which occurred in the seed bank, and the low level of soil disturbance at the study site. We conclude that the observed impact of red crabs on the abundance and diversity of successional species in natural light gaps on Christmas Island is due to their impact on germinating seedlings alone, rather than any additional impact on the soil seed bank.
Why might roadside mulgas be better mistletoe hosts?
Authors: Norton David A. , Smith Mark Stafford
Published: March 2003

We tested the hypothesis that roads in arid central Australia modify roadside hydrology and nutrient patterns creating better habitat for mistletoes (Loranthaceae). In two areas of mulga woodland near Alice Springs where mulgas (Acacia aneura) are the principal mistletoe host, we compared mistletoe abundance, and host foliar water and nutrient content between roadside and interior (100 m from the road) sites. Mistletoes were significantly more abundant close to roadsides than at interior sites and mulgas had significantly higher foliar water contents at roadside compared to interior sites. Mulga foliar P and N levels were not, however, significantly different between roadside and interior sites. We conclude that roads exert a strong influence on the adjacent biota in arid central Australia primarily through facilitating water infiltration at roadside sites.
Effects of stock grazing on the ground invertebrate fauna of woodland remnants
Authors: Bromham Lindell , Cardillo Marcel , Bennett Andrew F. , Elgar Mark A.
Published: March 2003

Habitat fragmentation can leave formerly widespread habitat types represented by only small habitat ‘islands’, and the conservation of these remnants is frequently compromised by ongoing disturbance. In northern Victoria, grazing of woodland remnants by sheep and cattle has profound effects on the vegetation structure of the woodland by removing understorey and ground vegetation. To investigate the effects of grazing pressure on remnant grey box Eucalyptus microcarpa woodland in northern Victoria, we surveyed the ground invertebrate fauna in ungrazed woodland remnants, grazed woodland remnants, and grazed pasture. The number of invertebrates caught increased from ungrazed woodland to grazed woodland to pasture, but this increase was due primarily to the most abundant orders (Hymenoptera, Coleoptera and Aranaea), and two abundant taxa characteristic of pasture (Orthoptera and Dermaptera). In contrast, most of the less abundant orders followed the opposite pattern, and were caught in higher numbers (and as a higher proportion of the total catch) in ungrazed woodland. Ungrazed woodland had a more diverse ground invertebrate fauna, most likely due to the greater diversity of food and habitat resources provided by the less disturbed vegetation. The differences in invertebrate communities corresponded to differences in vegetation and litter layers. The reduction in biodiversity of remnants due to grazing has implications for conservation management of remnant woodland in agricultural landscapes.
Recruitment and survival of Argyrodendron actinophyllum seedlings in an Australian rainforest
Authors: Nadolny Christopher
Published: March 2003

The capacity of seedlings to survive for extended periods beneath intact forest increases the likelihood of regeneration of many species of canopy trees in rainforests. I studied the demographics of Argyrodendron actinophyllum (F.M.Bail.) H.L.Edlin seedlings in a subtropical rainforest in northern New South Wales. A mast seeding of A. actinophyllum was observed and subsequent survival of seedlings monitored over a four year period. Densities of seedlings that emerged correlated with seedfall, while seedfall depended on the size and distance to the surrounding trees. Mortality of seedlings showed density‐dependence at higher seedling densities (above about 100 seedlings m−2), apparently in response to browsing pressure that varied with the density of seedlings. Seedlings that were protected from vertebrates by exclosure cages had lower mortality rates than unprotected seedlings and showed no density response. Glasshouse experiments showed seedling growth was reduced by defoliation, light intensity and initial seed weight, and that seedlings could not persist at light intensities below about 1% ambient, which occur in darker patches on the forest floor. Possible mechanisms whereby the observed spatial and temporal patterns of seedling recruitment could reduce the likelihood of the species becoming more common relative to other tree species in the forest are discussed.
River flows and estuarine ecosystems: Implications for coastal fisheries from a review and a case study of the Logan River, southeast Queensland
Authors: Loneragan Neil R.
Published: March 2003

River discharge has long been recognized as one of the factors that contributes to the high productivity of estuaries. Although there is little evidence that river inputs of terrestrial carbon make a direct contribution to coastal food webs, such exported nutrients may stimulate in situ production in estuaries and thus enhance the survivorship and growth of fish and crustaceans in these systems. Furthermore, fluctuations in salinity and turbidity may influence the extent of available habitat for fish and crustaceans and therefore their distribution and/or catchability. Despite these potential links between flow and the secondary production of estuaries and coastal waters, there is still a common perception that ‘water going to sea is wasted’ and a continuing trend to regulate the flow of rivers. We review the evidence for links between river flow and the productivity of estuarine/coastal fisheries, drawing on a case study of the Logan River in southeast Queensland, and explore the potential mechanisms for these linkages. Our research, and that of others, confirms that high river discharge can have a strong positive effect on the production of commercial and recreational coastal fisheries. It also shows that the seasonal pattern of flow is equally, if not more important, than the magnitude of flow. River regulation is likely to have a dramatic effect on the production of coastal fisheries and, given the current pressures for water resource development, this is an important avenue for future research and evaluation.
Ecology of benthic macro‐invertebrates in soft‐sediment environments: A review of progress towards quantitative models and predictions
Authors: Constable Andrew J.
Published: March 2003

This paper reviews the ecology of soft‐sediment macro‐invertebrates and, in particular, evaluates how much progress has been made in the recent literature towards elaborating statistical models of the ecology of these biota and in using quantitative predictions derived from these models. Steps to formulating statistical models on the dynamics of populations and assemblages are discussed. Current models are mostly conceptual (~70% of studies surveyed), falling into 2 main classes: population dynamics (including recruitment, mortality, dispersal and availability of patches) and process‐orientated studies (including the response of individuals to the physical environment, biogenic habitat modification, biological interactions and physical perturbations). Most recent studies were descriptive or on the population dynamics of species and were undertaken mostly at spatial scales of up to 1 km and temporal scales of months. The development of statistical models appears to be impeded by the limited scope of studies, an over‐emphasis on conceptual models (but recognizing an important role for a rigorous experiment framework) and a difficulty in using outcomes from small‐scale processes at the level of individual organisms to predict larger scale outcomes where many interactions contribute to variation in abundances. Currently, few studies undertake field assessments of the defining characteristics of habitats, the dynamics of those habitats and the relative importance of different habitats to individual populations. Much urgent work is required to develop large scale (space: > 1 km; time: > 1 years) statistical models. This is because attention needs to be given to those interactions and processes in the ecological systems that will provide for the greatest reduction in uncertainty in the quantitative predictions derived from these models.
Complex role of predators in structuring soft‐sediment macrobenthic communities: Implications of changes in spatial scale for experimental studies
Authors: Thrush Simon F.
Published: March 2003

In estuarine and coastal soft‐sediment systems, the role that predators play in structuring communities appears to be variable. Attributes of a particular predator that influence its role in structuring the community include: the rate of prey consumption; the behaviour, morphology and mobility of the predator; and, in soft‐ sediment communities, sediment disturbances associated with feeding. Reviews of field experiments designed to assess the role of predators in influencing the structure and function of soft‐sediment communities have concluded that many of the predators are generalists and there is usually a lack of competitive exclusion. Thus predation structures communities by many complex and indirect interactions that are often difficult to predict and generalize. Variations in the apparent strength and role of predation in structuring benthic communities may depend on a variety of ecosystem characteristics and/or aspects of study design. In this paper, I consider whether we have been conducting our experiments at the appropriate scales. Five case studies from Manukau Harbour (New Zealand) illustrate how small changes in the spatial scale can affect results, due to predator perceptions and prey mobility. The results of these studies demonstrate the need to identify scales at which predator effects are likely to be important and to fit experiments within the dynamics and heterogeneity of the system being studied. To do this, we need basic information on the natural history, behaviour and spatial and temporal variability of both predators and prey communities. We also need to be specific about scales of measurement when matching theoretical predictions to field observations/experiments. Finally, to enhance our ability to generalize from specific studies, we need to gather data that will enable us to both predict and test the importance of predation over a range of spatial and temporal scales.
What influences the structure of frog assemblages at forest streams?
Authors: Parris Kirsten M. , McCarthy Michael A.
Published: March 2003

We investigated habitat variables influencing the species richness and composition of frog assemblages at forest streams in southeast Queensland, Australia, to (i) determine whether these assemblage attributes can be predicted from the nature of the local habitat, and (ii) assess the value of species richness as a measure of the structure of frog assemblages. Stream size (as measured by the annual volume of precipitation in the upstream catchment) was found to be a significant predictor of the species richness of an assemblage, while stream size, understorey floristics in the riparian zone, the presence of palms and elevation were significantly correlated with the composition of assemblages. No relationship was found between broad forest type and the species richness or composition of frog assemblages. Species richness was not an informative description of the composition of frog assemblages, as assemblages with identical species richness had a low average compositional similarity. Results of this study indicate that frogs are responding to local, ground‐level stream and vegetation variables, a finding of both ecological interest and practical significance for the conservation management of forest‐dwelling frogs.
The effect of flooding and flood timing on leaf litter breakdown rates and nutrient dynamics in a river red gum (Eucalyptus camaldulensis) forest
Authors: Glazebrook Helen S. , Robertson Alistar I.
Published: March 2003

Comparisons of litter standing‐stocks in low‐lying and higher areas of the floodplain and the effects of controlled flooding events on leaf litter decomposition and leaf litter nutrients were examined during autumn and winter in a southeastern Australian river red gum (Eucalyptus camaldulensis) floodplain forest. The mean mass of total litter and some litter components was significantly greater in autumn than in winter but there were few differences in litter mass between low‐lying flood runners and higher sites (1.5 m) on the floodplain, regardless of season. Leaf decomposition was more rapid in flooded areas than in non‐flooded areas and was significantly faster in autumn than in winter. In flooded leaves, concentrations of phosphorus and nitrogen dropped rapidly during the first 3 days of each experiment, increased to near original after 7–10 weeks and then decreased again. After 112 days of decomposition the C:N:P ratios of leaf litter increased, but this effect was most marked for flooded leaves. Simple models of leaf litter dynamics indicated that leaf litter standing‐stocks in low‐lying flood runners would be reduced by flooding, particularly during autumn. In contrast, models predicted a net gain in standing‐stocks of leaf litter to be higher on the floodplain, particularly in autumn. Alteration to the seasonal timing of floods by river regulation has probably decreased litter standing‐stocks and nutrients available in low‐lying areas of the floodplain to support the production of macrophytes and biofilms during winter and spring floods.
Competition between the larvae of the introduced cane toad Bufo marinus (Anura: Bufonidae) and native anurans from the Darling Downs area of southern Queensland
Authors: Williamson Ian
Published: March 2003

Bufo marinus (L) has been present in the northern edge of the Darling River catchment for more than 25 years and the species currently occupies an area north of Chinchilla on the northern Darling Downs. This paper reports on preliminary findings of competition trials between larvae of B. marinus and native anurans in the Darling Downs area. Trials conducted in artificial ponds (1.4 × 1.2 × 0.2 m) indicated that Bufo reduced the growth of three native species (Limnodynastes tasmaniensis (Gunther), Limnodynastes terraereginae (Fry) and Notaden bennetti (Gunther)), and in some trials reduced the survival of two species (L. tasmaniensis and L. terraereginae). A fourth species (Limnodynastes ornatus (Grey)) showed higher growth rates with Bufo resulting from a non‐significant reduction in survival in those treatments. One of two trials conducted in enclosures (1.0 × 0.5 × 0.4 m) placed in a permanent water body indicated that B. marinus had a negative effect on growth of L. tasmaniensis. A survey of 30 breeding sites in the area found that Bufo used only a small number of water bodies in one breeding season and showed little overlap of pool use with most native species. Therefore, although B. marinus may negatively affect growth and survival of native anurans under some circumstances, the potential impact of B. marinus may be minimal if there are always many breeding sites where native anurans can breed in the absence of B. marinus. A more extensive assessment of temporal and spatial overlap of water body use by B. marinus and native anurans is needed to understand the exact impact of B. marinus in this region.
Taxonomic sufficiency in ecological studies of terrestrial invertebrates
Authors: Pik Anthony J. , Oliver Ian , Beattie Andrew J.
Published: March 2003

The concept of taxonomic sufficiency (identifying organisms only to a level of taxonomic resolution sufficient to satisfy the objectives of a study) has received little attention in ecological studies of terrestrial invertebrate assemblages. Here we critically evaluate three approaches to taxonomic sufficiency: the use of morphospecies, genera and functional groups. The objective was to compare estimates of richness (α diversity) and turnover (β diversity) of ant assemblages generated by these data with estimates produced using data for ant species. Ground‐active ants were sampled using pitfall trapping within three habitat types: a eucalypt plantation, woodland regrowth patches and the surrounding grassland at a study site in the upper Hunter Valley, New South Wales. Comparisons of assemblage richness and turnover among taxonomic data sets and habitats and after different data transformations used univariate (simple correlation and ANOVA) and multivariate (Mantel tests,
ANOSIM and
SSHMDS) techniques. Our study found: (i) morphospecies and genus richness was highly correlated with species richness over the study area; (ii) ordination scatterplots using species, morphospecies and genus data revealed similar patterns of site separation for the three habitats; (iii) the results were very similar using untransformed, log transformed and binary data; (iv) functional group ordinations separated all three habitat types for untransformed abundance data; and (v) estimates of species turnover were highly correlated with estimates of morphospecies and genus turnover. These results are discussed in relation to future monitoring of ant community structure.
Selective herbivory by red‐necked pademelon Thylogale thetis at rainforest margins: factors affecting predation rates
Authors: Wahungu Geoffrey M. , Catterall Carla P. , Olsen Mike F.
Published: March 2003

We examined browsing by red‐necked pademelons (Thylogale thetis) on shoots of rainforest plants at areas of rainforest–grassland interface in the Lamington Plateau of southeast Queensland. Terminal shoots from nine species (three each of vines, trees and shrubs) were compared. The effects of five factors (plant species, site, distance from forest edge, habitat (grassland or forest) and time (trip) at two levels of exposure (caged or uncaged)) were also compared. Among the uncaged shoots, 98% showed signs of damage compared with 18% of the caged shoots. In general, shoot predation was higher in the grassland than in the forest and decreased with increasing distance away from the forest edge in both habitats. The three vine species were more heavily browsed than all other species. Browsing by red‐necked pademelons is likely to influence regeneration near forest edges through direct death of seedlings as a result of predation and through altered competitive interactions resulting from selective herbivory. This effect, however, would be lower on seedlings within the forest habitat and would also reduce as seedlings establish themselves further from the forest edge into grassland habitat.
Body condition of the red kangaroo (Macropus rufus) in arid Australia: The effect of environmental condition, sex and reproduction
Authors: MOSS G. L. , CROFT D. B.
Published: March 2003

The body condition of live‐caught male and female red kangaroos (Macropus rufus Desmarest 1842) was assessed in environmental conditions described by a period of high (two years) followed by low (one year) rainfall. Changes in pasture biomass and quality closely followed rainfall fluctuations in these years. Fluctuations in standardized body mass, in turn, lagged behind changes in pasture biomass with a delay of three months. Male and female body condition was best predicted by green grass biomass. Kangaroos caught during the high rainfall period reached an above average plane of condition. In the low rainfall period that followed, the condition of kangaroos declined, and was greater for small males (14–41 kg), large males (45–89 kg), and females (18–36 kg) with small or no pouch young than for female subadults (< 22 kg) and females with large pouch young (20–34 kg). Female subadults were also significantly older and the ratio of females:females with young‐at‐foot was higher in the low rainfall period. This suggests a mechanism for age/sex class differences in survivorship. The lagged synchrony of body condition with pasture biomass can be explained by body‐size related digestive constraints, reflecting sex differences in adaptation to a stochastic environment.
Towards an explanation of the altitudinal distributions of three species of Eucalyptus in central Tasmania
Authors: KIRKPATRICK J. B. , GIBSON N.
Published: March 2003

Eucalyptus gunnii, E. rodwayi and E. ovata are parapatrically distributed in grassy woodlands at high, medium and low altitude, respectively, in central Tasmania. Seedlings from provenances from the middle of the altitudinal ranges of all species were capable of survival for 18 months on sites dominated by the other two species. However, 9 years after planting E. ovata had died out in open vegetation on all sites. In contrast, E. rodwayi had survived in open vegetation on all sites and was the sole or major survivor in the two lower altitude areas. E. gunnii had performed marginally better than E. rodwayi in the open vegetation at the highest altitude site, had survived in the E. rodwayi site and had died out in the E. ovata site. The results of field trials, and experiments in the glasshouse and laboratory, suggested that E. ovata is absent from open vegetation at the higher altitudes because of its susceptibility to frost, that E. rodwayi dominates the middle altitudes because of its superior frost resistance, that E. gunnii dominates the highest altitudes because of superior growth rates to E. rodwayi in misty and cool conditions, and that E. ovata is dominant at low altitudes because of its superior growth rates in warm conditions. Recent climatic changes are posited to have had some effect on the results of the field experiment.
Historical incidence of Perthida leafminer species (Lepidoptera) in southwest Western Australia based on herbarium specimens
Authors: WILLS IAN ABBOTT, ALLAN , BURBIDGE TOM
Published: March 2003

Examination of more than 500 herbarium specimens of Eucalyptus marginata and E. rudis for the presence of two species of leafminers, Perthida spp., indicated that these native insect species were very rare in southwest Western Australia until first recorded in metropolitan Perth in 1878 and 1897, respectively, when west coast populations of both leafminer species evidently increased dramatically. The first record from the south coast dates from 1901 near Albany. Evidence of leafminer populations on E. marginata remote from coastal settlements was not recorded until 1917, near Cranbrook. The first record in jarrah forest was in 1967, some 10 years after outbreaks of the pest insect are known to have occurred in the forest. The Perthida leafminer species on E. rudis was first recorded from inland areas in 1904 and appears to have increased more rapidly in abundance than the species found on E. marginata. These early geographical and species differences in incidence are discussed in terms of changing disturbance patterns, which have not been simultaneous across southwest Western Australia.
Flowering phenology of myrtaceous trees and their relation to climatic, environmental and disturbance variables in northern New South Wales
Authors: Law B. , Mackowski C. , Schoer L. , Tweedie T.
Published: March 2003

Patterns of flowering phenology, which represent a partial description of food availability for nectarivores, are described for 20 species of myrtaceous trees on the mid‐north coast of New South Wales (NSW), Australia. Data were recorded monthly between 1982 and 1992 across 23 sites that comprise a variety of local environmental conditions and disturbance histories. Flowering periodicity and intensity were highly variable between species and sites, ranging from annual flowering to no flowering over the 10‐year period. Cool temperatures prior to floral budding was a strong predictor of flowering for nine species. Extraordinary climatic events also influenced flowering. The period of greatest flowering for all species combined occurred 9 months after the highest monthly rainfall recorded in the survey (March 1985). An 18‐month extreme drought led to poor flowering in Corymbia variegata, Eucalyptus acmenoides, Eucalyptus grandis and Eucalyptus resinifera, but recovery after the drought broke was rapid. In contrast to climate, few site‐based environmental variables explained the intersite variation in flowering performance of the tree species. Site disturbance from logging at two sites during the survey did not influence flowering in the remaining canopy over following years. No species showed a negative correlation with a history of recent logging, and direct comparisons, between large‐ and medium‐sized trees, of the percentage of foliage in flower showed no differences for any species. At the scale of a timber production forest, the negligible effect of tree size (if >10 cm diameter at breast height over bark), and high stem density resulting from selective logging, leave about half of the net harvestable area producing flowers at a similar density to unlogged forest. However, larger trees flowered more frequently than medium‐sized trees in C. variegata (medium: every 5.9 years; large: every 2.3 years) and there was a trend in this direction for 13 of 17 species. Low‐intensity burns and wildfires caused differing amounts of crown scorch, sometimes resulting in bud loss, but most species flowered at prefire levels 1–3 years after the disturbance. Eucalyptus microcorys and Angophora costata flowered poorly at sites that experienced frequent low‐intensity burns. Regionally, blossom shortages occur through a combination of spatial and temporal patchiness in flowering and the clearing of those species that occurred on soils preferred for agriculture. On the north coast of NSW, these shortages commonly occur from late winter to spring. Species that flower reliably in this period include Eucalyptus robusta, Eucalyptus tereticornis and Eucalyptus siderophloia in late winter and E. siderophloia and E. acmenoides in spring.
Coexistence of a locally undifferentiated foraging guild: avian snatchers in a southeastern Australian forest
Authors: MacNally Ralph
Published: March 2003

Three species of sexually dichromatic, insectivorous birds (Golden Whistler,Pachycephala pectoralis;Rufous Whistler,Pa. rufiventris;Rose Robin,Petroica rosea) employ a characteristic foraging manoeuvre (snatching or sally‐striking) disproportionately often, leading several studies to group them together in one foraging guild. The three species synchronously co‐occupy an extensive eucalypt forest east of Melbourne, Australia (Olinda State Forest). All assemble in relatively high densities in late winter and through spring and early summer to breed. Log‐linear modelling of use of foraging techniques, substrate, plant species and heights within the forest indicate that all six species–gender groups virtually do not differ from one another: a situation in which very similar species coexist at high densities. The results are considered in the context of interspecific competition among ecologically similar species and it is suggested how such a situation might arise and be sustained. The absence of gender‐specific differentiation within species is also addressed.
Long‐term effects of frequent low‐intensity burning on ant communities in coastal blackbutt forests of southeastern Australia
Authors: York Alan
Published: March 2003

Periodic low‐intensity fire (hazard‐reduction burning) is a conspicuous management strategy in virtually all of Australia’s dry forest communities where it is primarily used to reduce fuel levels with the intention of minimising the extent and severity of wildfires. Little is known, however, about the effects of its repeated use on natural ecosystems over long periods of time. This study investigated the long‐term effects of frequent low‐intensity fire on forest ant communities by comparing frequently burnt sites with long‐unburnt control sites. While the richness of ant communities remained largely unchanged, the composition of assemblages differed substantially between treatments. Although frequent burning apparently resulted in the loss of a substantial number of species, the overall richness of frequently burnt areas was maintained by the addition of species not present on unburnt sites. These changes in species composition were accompanied by major changes in community organisation (structure) and were considered to be a response to altered habitat conditions, particularly litter biomass, vegetation structure and patterns of insolation at ground level. Appropriate fire prescriptions could therefore be applied to manipulate these habitat elements at a landscape scale to meet both management and conservation goals. A comparison of pitfall trapping and litter extraction techniques revealed the importance of a composite sampling strategy, with 22% of ant species detected only by litter extraction.
Evidence for effects of Spartina anglica invasion on benthic macrofauna in Little Swanport estuary, Tasmania
Authors: Hedge Paul , Kriwoken Lorne K.
Published: March 2003

Spartina anglica is an exotic perennial grass that can rapidly colonise the intertidal zone of temperate estuaries and lagoons. Consequently, there is considerable concern about its impact on estuarine flora and fauna. This study provides the first investigation of ecological impacts by S. anglica in Australia. The objective was to investigate the impacts of S. anglica on benthic macroinvertebrate communities inhabiting mudflat and native saltmarsh habitats at Little Swanport estuary, Tasmania. The null hypothesis that species richness and species abundance of benthic macroinvertebrates in exotic S. anglica marsh does not differ from adjacent native saltmarsh and mudflat habitats was tested. Eighteen species and 3716 macroinvertebrates were collected from 60 intertidal core samples in three habitats. Species richness, total abundance of invertebrates, crustacean abundance and mollusc abundance of mudflat communities were significantly (P < 0.05) lower when compared to those inhabiting adjacent S. anglica marsh and native saltmarsh. However, species richness and total abundance of invertebrates of native saltmarsh and S. anglica marsh did not differ significantly. Ordination of macroinvertebrate data clearly separated mudflat sites from vegetated sites but showed remarkable similarity between exotic and native vegetated sites.
Distinguishing area and habitat heterogeneity effects: a simulation test of the MacNally and Watson (1997) protocol
Authors: Mcguinness Keith A.
Published: March 2003

Distinguishing the roles that different factors, such as sampling effects and habitat heterogeneity, play in generating species‐area curves continues to be difficult in many communities. A recent response to this challenge is the proposal of a ‘zoom’ protocol in which species richness and habitat heterogeneity are sampled in successively larger units (transects or quadrats). The utility of this approach requires that there be justifiable, predictable and unambiguous relationships between richness and heterogeneity. Results of computer simulations that I have done to test the predicted relationships demonstrate, however, that the predicted patterns were not always observed and, on occasion, more complex relationships were observed in their place. While the development of such protocols may increase our understanding of species‐area curves, they are unlikely ever to pronounce unambiguously on their causes.
Foraging ecology of the South Australian glossy black‐cockatoo (Calyptorhynchus lathami halmaturinus)
Authors: Pepper J. W. , Male T. D. , Roberts G. E.
Published: March 2003

The endangered South Australian glossy black‐cockatoo (Calyptorhynchus lathami halmaturinus Mathews 1912) feeds almost exclusively on the seeds of the drooping sheoak (Allocasuarina verticillata), and shows marked preferences for individual trees. This field study investigated foraging ecology and tree selection through observations of foraging birds and measurements of trees and seed cones. The cockatoos spent the vast majority of their foraging time (94%) handling seed cones, and handling behaviour was highly stereotyped. Handling time per cone was correlated primarily with cone size, while seed intake rate was correlated primarily with seed mass per cone. The cockatoos fed mostly in trees with signs of previous feeding. They tended initially to sample trees with large seeds, and to stay for long feeding bouts in trees with high ratios of seed‐to‐cone mass. As a result of these biases, feeding was concentrated in trees with high seed mass per cone. Preferred trees were also larger, with higher ratios of seed‐to‐cone mass and larger seeds containing more lipid and protein. By feeding from selected trees the cockatoos increased both their seed intake rate and the nutritional quality of the seeds ingested, thereby increasing their energy intake rate by an estimated 28%. They did not discriminate against trees that had re‐grown from basal shoots after fires. Insect larvae were present in some seed cones but the cockatoos did not appear to actively seek them. Males foraged 19% more efficiently than females, resulting in greater daily food intake. The characteristics of individual A. verticillata trees that determined the cockatoos’ feeding rates were also correlated with their distribution on a regional scale. This suggests that the distribution of this endangered cockatoo depends not only on the presence of food trees, but also on their regionally varying feeding profitability.
Effect of soil salinity on plant distribution and production at Loburu delta, Lake Bogoria National Reserve, Kenya
Authors: Onkware Augustino Osoro
Published: March 2003

A study was carried out at Loburu delta, Lake Bogoria National Reserve, Kenya, on the effect of different levels of soil salinity and moisture on plant species distribution, production, reproductive strategy and litter decomposition. The soils are coarse and vary significantly in levels of salinity and moisture. The highest salinity was greater than 3.0 S/m, ECe. Soil moisture was significantly higher in the more saline than non‐saline or low salinity soils because of ground seepage. Sixteen plant species were collected but only Sporobolus spicatus and Cyperus laevigatus were determined to be true halophytes. Biomass and above‐ground production were significantly higher in the high and medium saline soils than the non‐saline or hyper‐saline soils (>3.0 S/m, Ece). Precipitation promoted various aspects of production in both halophytes at various levels of salinity. Soil salinity did not influence biomass allocation to reproductive structures but precipitation enhanced allocation to stolons in Sporobolus spicatus. The dead plant mass was significantly higher than biomass at all salinities, which indicated low grazing pressure at the site. Litter decomposition was only marginally reduced by high soil salinity. It was concluded that low moisture limits biomass and production on the non‐saline soils and salinity is responsible for low production in the hyper‐saline soils.
Pseudoreplication in experimental designs for the manipulation of seed germination treatments
Authors: Morrison David A. , Morris E. Charles
Published: March 2003

In the published reports concerning the design of laboratory experiments examining signals that might trigger seed germination, there is currently a misunderstanding of what might constitute correct replication of the experimental treatment. This is particularly true for the study of dry heat, smoke and charcoal, where either an individual seed or a batch of seeds in a Petri dish or tray is being treated as the unit of replication of the experimental treatment, irrespective of whether or not those seeds were all subjected to the experimental manipulation simultaneously. Under these circumstances, the application of the treatment is unreplicated, while samples nested within that single application have been replicated, and the Petri dishes/trays are functioning solely as independent replicates of the variability in germination response within the seed batch used and variation within the pretreatment and post‐treatment environments. Thus any observed difference in germination may be due to the germination treatment but, potentially, it could also be due to any chance event affecting the treated sample. There are a number of alternative experimental designs that avoid this problem. The essential point with these designs is that the application of the experimental manipulation to each replicate should be separated in space by the use of separate experimental equipment and/or in time by the repeated use of the same experimental apparatus.
Retrospective monitoring of rangeland vegetation change: ecohistory from deposits of sheep dung associated with shearing sheds
Authors: Witt G. Bradd , Berghammer Lindi J. , Moll Robert J. S. Beeton and Eugene J.
Published: March 2003

This paper explores the potential of a new method of reconstructing historical vegetation change in the Australian rangelands. Historical monitoring of rangeland vegetation has been so deficient that it is not possible to determine whether a long‐term trend toward degradation has occurred (as is often assumed) or, indeed, if it is continuing to occur. Because long‐term records are unavailable any attempt to monitor vegetation retrospectively must be based on proxy measures rather than direct observation. Where historical data are lacking an integration of palaeoecological, archaeological and ecological methods is required to reconstruct the past. Our research is based on a detailed analysis of sheep faeces deposited near a shearing shed in the semiarid rangelands of south‐west Queensland between the late 1930s and the mid‐1990s. The faeces in these deposits represent the diet of sheep in the days leading up to the property’s annual shearing and as such are a potentially useful index to changes in vegetation. Results indicate significant changes in the diet of sheep since the late 1940s. The potential of this method, and its limitations, are discussed. Long‐term records are critical in understanding issues of sustainability in land management and it is intended that this paper will stimulate further research into historical vegetation change in rangelands.