bluuebunny/crossref_metadata_2025 huggingface dataset:
Episodic seedling growth inAllosyncarpia ternata, a lignotuberous, monsoon rainforest tree in northern Australia
Authors: Fordyce I. R. , Eamus D. , Duff G. A.
Published: March 2003

On the western Arnhem Land Plateau, Northern Territory, Australia, seedlings of the canopy treeAllosyncarpia ternataS.T. Blake typically spend many years (perhaps decades) as small (<1 m), multistemmed plants on the forest floor. In this establishment phase, long periods of apparent inactivity are interrupted by episodes of rapid growth. This paper describes a 5‐year field‐monitoring program to examine the pattern of seedling growth and survival in allosyncarpia forest, and field and shadehouse measurements of lignotuber size. Individual seedlings may produce, each wet season, a number of fast‐growing stems, which then die back in the following dry season. As a result, mean annual above‐ground growth during this life stage is negligible. With each wet season, however, the seedling extends its below ground parts – a large lignotuber and a deep root system. After a number of years, when the lignotuber has grown large enough to sustain massive shoot growth, when a suitable light gap becomes available, and presumably when roots reach reliable dry‐season water supplies, the seedling grows rapidly. Thus, the shortage of saplings in allosyncarpia forest is due to the short time that individual plants spend at that particular growth‐stage, rather than to any dysfunction in recruitment.
Grazing effects on plant cover, soil and microclimate in fragmented woodlands in south‐western Australia: implications for restoration
Authors: Yates Colin J. , Norton David A. , Hobbs Richard J.
Published: March 2003

This study investigated the impacts of livestock grazing on native plant species cover, litter cover, soil surface condition, surface soil physical and chemical properties, surface soil hydrology, and near ground and soil microclimate in remnant Eucalyptus salmonophloia F. Muell woodlands. Vegetation and soil surveys were undertaken in three woodlands with a history of regular grazing and in three woodlands with a history of little or no grazing. Livestock grazing was associated with a decline in native perennial cover and an increase in exotic annual cover, reduced litter cover, reduced soil cryptogam cover, loss of surface soil microtopography, increased erosion, changes in the concentrations of soil nutrients, degradation of surface soil structure, reduced soil water infiltration rates and changes in near ground and soil microclimate. The results suggest that livestock grazing changes woodland conditions and disrupts the resource regulatory processes that maintain the natural biological array in E. salmonophloia woodlands. Consequently the conditions and resources in many remnant woodlands may be above or below critical thresholds for many species. The implications of these findings for restoration of plant species diversity and community structure are discussed. Simply removing livestock from degraded woodlands is unlikely to result in the restoration of plant species diversity and community structure. Restoration will require strategies that capture resources, increase their retention and improve microclimate.
Smoke and heat effects on soil seed bank germination for the re‐establishment of a native forest community in New South Wales
Authors: Read T. R. , Bellairs S. M. , Mulligan D. R. , Lamb D.
Published: March 2003

The effects of plant‐derived smoke and of heat on the emergence of seedlings from seeds were assessed. Seeds had been stored in forest topsoil used for mine site rehabilitation. The study was carried out in a dry sclerophyll, spotted gum (Corymbia maculata), forest community at the Mount Owen open‐cut coal mine in the Hunter Valley region of New South Wales. Samples of the surface 2.5 cm of topsoil were either exposed to cool smoke from eucalypt foliage for 60 min, heated to 80°C, or left untreated. Seedling emergence from the seed bank in this soil was then monitored in a glasshouse. Within the first month, smoke alone promoted a 4.3‐fold increase in the density of seedlings relative to control. There were 540 emergents per m2 in the control and 2309 per m2 in the smoke treated topsoil. Many annual and perennial herbs emerged but grasses responded most strongly to smoke. Germination in seven of the 20 grass species was promoted by smoke. Smoke promoted the germination of some introduced species as well as native species, and accelerated the rate at which seedlings emerged, although these differences sometimes declined with time. Heat also stimulated germination but smoke and heat stimuli appeared to be complementary in their promotion of seedling emergence from the topsoil seed bank. Each treatment increased the density of different species, enhanced the species richness of different components of the seed bank, and had different effects on the rate of emergence. The results suggest that increased seed germination in the field immediately following a moderate intensity fire may sometimes be the result of smoke stimulation and sometimes the result of heat stimulation of the soil seed bank. These findings may have important implications for minesite revegetation programs where topsoils are replaced after mining and rapid germination of seeds stored in these soils is required during short periods when conditions are favourable for germination.
Invasions: the perspective of diverse plant communities
Authors: Prieur‐Richard Anne‐Helene , Lavorel Sandra
Published: March 2003

Exotic plant invasions represent a threat to natural and managed ecosystems. Understanding of the mechanisms that determine why a given species may invade a given ecosystem, or why some biomes and regions seem more prone to invasions, is limited. One potential reason for this lack of progress may lie in how few studies have addressed invasion mechanisms from the point of view of the invaded community. On the other hand, the renewed debate about the relationship between ecological diversity and ecosystem stability offers the opportunity to revisit existing theory and empirical evidence, and to attempt to investigate which characteristics of plant communities, including their diversity, contribute to their invasibility. Empirical studies have shown both positive and negative relationships between species diversity of resident plant communities and their invasibility by external species. Rather than attempting to build a larger collection of case studies, research now needs to address the mechanisms underlying these relationships. Previous knowledge about the mechanisms favouring invasion needs to be coupled with community theory to form the basis of these new investigations. Modern community theory offers hypotheses and techniques to analyse the invasibility of communities depending on their diversity and other factors, such as species’ life histories and environmental variability. The body of knowledge accumulated in invasion ecology suggests that the role of disturbances, in interaction with fertility, and the importance of interactions with other trophic levels, are specific factors for consideration. In addition, it is essential for future studies to explicitly tease apart the effects of species richness per se from the effects of other components of ecological diversity, such as functional diversity (the number of functional groups) and trophic diversity (the number of interactions among trophic levels).
Arthropod responses to experimental fire regimes in an Australian tropical savannah: ordinal‐level analysis
Authors: Andersen Alan N. , MÜller Warren J.
Published: March 2003

Fire is widely used for conservation management in the savannah landscapes of northern Australia, yet there is considerable uncertainty over the ecological effects of different fire regimes. The responses of insects and other arthropods to fire are especially poorly known, despite their dominant roles in the functioning of savannah ecosystems. Fire often appears to have little long‐term effect on ordinal‐level abundance of arthropods in temperate woodlands and open forests of southern Australia, and this paper addresses the extent to which such ordinal‐level resilience also occurs in Australia’s tropical savannahs. The data are from a multidisciplinary, landscape‐scale fire experiment at Kapalga in Kakadu National Park. Arthropods were sampled in the two major savannah habitats (woodland and open forest) using pitfall traps and sweep nets, in 15–20 km2 compartments subjected to one of three fire regimes, each with three replicates: ‘early’ (annual fires lit early in the dry season), ‘late’ (annual fires lit late in the dry season), and ‘unburnt’ (fires absent during the five‐year experimental period 1990–94). Floristic cover, richness and composition were also measured in each sampling plot, using point quadrats. There were substantial habitat differences in floristic composition, but fire had no measured effect on plant richness, overall composition, or cover of three of the four dominant species. Of the 11 ordinal arthropod taxa considered from pitfall traps, only four were significantly affected by fire according to repeated‐measures
ANOVA. There was a marked reduction in ant abundance in the absence of fire, and declines in spiders, homopterans and silverfish under late fires. Similarly, the abundances of only four of the 10 ordinal taxa from sweep catches were affected by fire, with crickets and beetles declining in the absence of fire, and caterpillars declining under late fires. Therefore, most of the ordinal taxa from the ground and grass‐layer were unaffected by the fire treatments, despite the treatments representing the most extreme fire regimes possible in the region. This indicates that the considerable ordinal‐level resilience to fire of arthropod assemblages that has previously been demonstrated in temperate woodlands and open forests of southern Australia, also occurs in tropical savannah woodlands and open forests of northern Australia.
Predation by red foxes limits recruitment in populations of eastern grey kangaroos
Authors: Banks Peter B. , Newsome Alan E. , Dickman Chris R.
Published: March 2003

We investigated the impact of red fox (Vulpes vulpes Linnaeus 1758) predation on juvenile eastern grey kangaroos (Macropus giganteus Shaw 1790) using a replicated predator removal experiment. In two sites in Namadgi National Park, south‐eastern Australia, a persistent 1080 poisoning campaign over 18 months reduced fox density by more than 85%, and to less than 10% of the fox density in two other sites with no fox baiting. Changes in the mother : young ratios and densities of kangaroo populations were monitored twice monthly along 2‐km transects in each site from July 1993 to February 1995. Compared to nonremoval sites, where foxes were controlled, 25–40% more females retained juveniles over the period when these young became emergent from the pouch. This higher survival of emergent pouch young resulted in a significantly higher proportion of juveniles in kangaroo populations at fox control sites, which resulted in a significantly higher annual growth rate. We conclude that predation upon juveniles is an important limiting factor for kangaroo populations in Namadgi NP.
Diversity of insect‐induced galls along a temperature– rainfall gradient in the tropical savannah region of the Northern Territory, Australia
Authors: Blanche K. R.
Published: March 2003

Evidence regarding the effect of temperature and rainfall on gall‐inducing insects is contradictory: some studies indicate that species richness of gall‐inducing insects increases as environments become hotter and drier, while others suggest that these factors have no effect. The role of plant species richness in determining species richness of gall‐inducing insects is also controversial. These apparent inconsistencies may prove to be due to the influence of soil fertility and the uneven distribution of gall‐inducing insect species among plant taxa. The current study tested hypotheses about determinants of gall‐inducing insect species richness in a way different to previous studies. The number of gall‐inducing insect species, and the proportion of species with completely enclosed galls (more likely to give protection against heat stress and desiccation), were measured in replicate plots at five locations along a 500‐km N‐S transect in the seasonal tropics of the Northern Territory, Australia. There is a strong temperature–rainfall gradient along this transect during the wet season. Plant species lists had already been compiled for each collection plot. All plots were at low elevation in eucalypt savannah growing on infertile soils. There was no evidence to suggest that hot, dry environments in Australia have more gall‐inducing insect species than cooler, wetter environments, or that degree of enclosure of galls is related to protecting insects from heat stress and desiccation. The variable number of gall‐inducing insect species on galled plant species meant that plant species richness did not influence gall species richness. Confirmation is still required that low soil fertility does not mask temperature–rainfall effects and that galls in the study region are occupied predominantly in the wet season, when the temperature–rainfall gradient is most marked.
Palaeo‐ecology of the Gap and Coturaundee Ranges, western New South Wales, using stick‐nest rat (Leporillus spp.) (Muridae) middens
Authors: Allen V. , Head L. , Medlin G. , Witter D.
Published: March 2003

Pollen, plant and animal macrofossils recovered from nine Leporillus spp. (Muridae) middens found in the Gap and Coturaundee Ranges, western New South Wales were examined. By comparing current vegetation, pollen from modern surface samples and pollen from midden samples, general vegetation characteristics over the last 6500 years
BP were reconstructed. Evidence shows that a greater shrub cover was apparent between 6500 and 5200
BP, while other aspects of the vegetation cover were similar to present. An increase in tree pollen, possibly indicating greater tree cover, occurred around 3400–2600
BP, while vegetation in the last 1300 years was similar to present. These interpretations, particularly from the older samples, are tentative due to spatial and temporal limitations. Animal macrofossils from the middens indicate that several mammal species now extinct or uncommon in western New South Wales have occurred in the area in the past 3000 years. This study also confirms that reconstruction of vegetation from Leporillus spp. midden evidence should be seen as separate ‘snapshots’, rather than continuous records over a stratigraphically defined timescale.
Swapping space for time and unfair tests of ecological models
Authors: Tyre Andrew J. , Tenhumberg Brigitte , Mccarthy Michael A.
Published: March 2003

Testing ecological models for management is an increasingly important part of the maturation of ecology as an applied science. Consequently, we need to work at applying fair tests of models with adequate data. We demonstrate that a recent test of a discrete time, stochastic model was biased towards falsifying the predictions. If the model was a perfect description of reality, the test falsified the predictions 84% of the time. We introduce an alternative testing procedure for stochastic models, and show that it falsifies the predictions only 5% of the time when the model is a perfect description of reality. The example is used as a point of departure to discuss some of the philosophical aspects of model testing.
Roost preferences and foraging ranges of the eastern forest bat Vespadelus pumilus under two disturbance histories in northern New South Wales, Australia
Authors: Law Bradley S. , Anderson Jason
Published: March 2003

Little is known about the habitat requirements of Australian bats; however, this information is needed to make better‐informed decisions when systems are disturbed. This study contrasts the roosting and foraging ecology of the eastern forest bat Vespadelus pumilus (Vespertilionidae), one of Australia’s smallest bats, between two sites of differing disturbance history on the mid‐north coast of New South Wales. Lorne Flora Reserve (182 ha) is primarily old‐growth forest surrounded by regrowth forest and eucalypt plantations, while Swans Crossing is dominated by regrowth and eucalypt plantations established on part of an old dairy farm. A total of 38 bats were tracked during the maternity and mating seasons at the two sites. Roost preferences were determined by comparing trees used as roosts with those randomly available, while foraging bats were triangulated from fixed stations at night. Bats tracked at Lorne Flora Reserve typically roosted in hollows within large, mature trees and showed a strong preference for roosting and foraging (females only) within the Reserve. Lactating females at Swans Crossing roosted in hollows of remnant rainforest trees within a gully and dead eucalypts, while males often roosted in understorey trees (such as Acacia). Dead trees were frequently used as roosts at both sites. Under both disturbance histories, the mean distance of female maternity roosts from creeks was 20 m, indicating that riparian zones provide important roosting habitat for V. pumilus. However, roosts shifted to the mid‐slope prior to winter when bats mate. Retention of mature trees in a variety of topographic locations may allow behavioural adjustments with the seasons. Bats caught in the regrowth forest also foraged there, with foraging ranges averaging just 5.3 ha (n = 10), indicating that regrowth is used by this bat for both foraging and roosting.
Responses of forest eucalypts to moderate and high intensity fire in the Tingle Mosaic, south‐western Australia: comparisons between locally endemic and regionally distributed species
Authors: Wardell‐Johnson G. W.
Published: March 2003

Responses of three locally endemic (Eucalyptus brevistylis, Eucalyptus jacksonii and Eucalyptus guilfoylei) and three co‐occurring regional eucalypts (Eucalyptus marginata, Eucalyptus diversicolor and Corymbia calophylla) to moderate‐ and high‐intensity fires were examined in granitic terrain of the Tingle Mosaic, south‐western Australia. Significant associations between diameter distributions and community type (CT) for each species (P < 0.001) suggest that fire response will also vary according to the habitat/fire interaction. None of the species were fire sensitive, although responses differed both within and between species, and with CT. All species examined predominately consisted of several cohorts of regeneration within a forest stand. Each species had thick bark and re‐sprouted from crown epicormics following 100% scorch of the mature tree. The quantity and type of regeneration in relation to gaps created by individual dead trees following fire differed between species; for example, E. guilfoylei regeneration was strongly associated with gaps, and C. calophylla with non‐gaps. However, regeneration of the two tall open‐forest species, E. jacksonii and E. diversicolor were not most associated with either gaps or non‐gaps. The very low levels of regeneration of E. brevistylis following fire and the high proportion of stems of E. jacksonii that were hollow butted (40% of stems > 1 m DBHOB) may be factors associated with narrow endemism of these species and may affect the vulnerability of these eucalypts to fire. The interaction of seed availability, intense fires and subsequent rainfall may be critical in the long term survival of these species. Eucalyptus guilfoylei, by contrast, appears well adapted to the increasing levels of disturbance likely in the region where these species occur. The vulnerability of a locally endemic species in a fire‐prone environment is likely to reflect differences to the prevailing adaptations of the dominant species rather than an inherent ability of the species to survive or respond. Management regimes must account for variations in species responses to fire in different CTs if the long‐term survival chances of local endemics are to be enhanced.
Success and safety in the biological control of environmental weeds in New Zealand
Authors: Fowler Simon V. , Syrett Pauline , Hill Richard L.
Published: March 2003

Biological control, using specialist insect herbivores and plant pathogens, can be a self‐sustaining, cost‐effective and low‐risk tool for the management of environmental weeds. Agents have been recorded attacking non‐target plants in New Zealand and elsewhere, but the effects are usually minor and/or transitory. It seems probable that only two cases, worldwide, will result in significant damage to non‐target plants (representing 0.5% of the nearly 400 insect, mite, or fungal species used in classical weed biocontrol). Both of these cases were predictable from host range testing. Negative indirect, or ‘downstream’, ecological effects from specific weed biocontrol agents are difficult to predict and measure. They are probably insignificant compared to the impacts of the invasive plants that the agents are introduced to control. However, it is necessary to balance the risks associated with any introduction against the environmental benefits from controlling a weed to a predicted level. Recent analyses suggest that success rates are better than generally perceived. For New Zealand programmes, where enough time has lapsed to allow assessment, we calculate a full/partial success rate of 83%. Many of the costs associated with environmental weeds are difficult to quantify. Detailed risk assessment will make biological control programmes more expensive and time‐consuming, so that reliance on non‐biological management methods for environmental weeds may actually increase. The costs of biocontrol programmes against some New Zealand weeds can be kept down by using research already carried out in Australia and other countries, and the process is reciprocal. Developing international consortia of sponsors is also a potential way to fund programmes against weeds shared by several countries.
Variation in the impact of exotic grasses on native plant composition in relation to fire across an elevation gradient in Hawaii
Authors: D’Antonio Carla M. , Tunison J. Timothy , Loh Rhonda K.
Published: March 2003

The impact that an exotic species can have on the composition of the community it enters is a function of its abundance, its particular species traits and characteristics of the recipient community. In this study we examined species composition in 14 sites burned in fires fuelled by non‐indigenous C4 grasses in Hawaii Volcanoes National Park, Hawaii. We considered fire intensity, time since fire, climatic zone of site, unburned grass cover, unburned native cover and identity of the most abundant exotic grass in the adjacent unburned site as potential predictor variables of the impact of fire upon native species. We found that climatic zone was the single best variable for explaining variation in native cover among burned sites and between burned and unburned pairs. Fire in the eastern coastal lowlands had a very small effect on native plant cover and often stimulated native species regeneration, whereas fire in the seasonal submontane zone consistently caused a decline in native species cover and almost no species were fire tolerant. The dominant shrub, Styphelia tameiameia, in particular was fire intolerant. The number of years since fire, fire intensity and native cover in reference sites were not significantly correlated with native species cover in burned sites. The particular species of grass that carried the fire did however, have a significant effect on native species recovery. Where the African grass Melinis minutiflora was a dominant or codominant species, fire impacts were more severe than where it was absent regardless of climate zone. Overall, the impacts of exotic grass‐fuelled fires on native species composition and cover in seasonally dry Hawaiian ecosystems was context specific. This specificity is best explained by differences between the climatic zones in which fire occurred. Elevation was the main physical variable that differed among the climatic zones and it alone could explain a large percentage of the variation in native cover among sites. Rainfall, by contrast, did not vary systematically with elevation. Elevation is associated with differences in composition of the native species assemblages. In the coastal lowlands, the native grass Heteropogon contortus, was largely responsible for positive changes in native cover after fire although other native species also increased. Like the exotic grasses, this species is a perennial C4 grass. It is lacking in the submontane zone and there are no comparable native species there and almost all native species in the submontane zone were reduced by fire. The lack of fire tolerant species in the submontane zone thus clearly contributes to the devastating impact of fire upon native cover there.
Environmental weeds in Australia and New Zealand: issues and approaches to management
Authors: Williams Jann A. , West Carol J.
Published: March 2003

Environmental weeds are plants that invade natural ecosystems and are considered to be a serious threat to nature conservation. Australia and New Zealand, where biota with a high degree of endemism have evolved, are particularly susceptible to environmental weeds. Environmental weeds have been implicated in the extinction of several indigenous plant species, and they also threaten ecosystem stability and functional complexity. Historically, emphasis has been placed on the chemical or manual ‘control’ of weed infestations, often with little consideration of the long‐term effectiveness or the ecological consequences of such an approach. As the threat from environmental weeds is becoming more fully recognized, an integrated, strategic and ecological approach to weed management is being recommended. In both countries, systems for screening new plants before allowing entry for cultivation have been developed. For already established plants, management is conducted within a legislative and policy framework such as the Regional Pest Management Strategies that operate through the Biosecurity Act 1993 in New Zealand. Noxious weed legislation in Australia has historically focused on agricultural weeds, but some Acts are (or have recently been) undergoing revision to give greater emphasis to environmental weeds and the involvement of the community in weed management. Quarantine, legislation, research and on‐ground management are complemented by education programmes about the impact and control of environmental weeds. This paper provides an overview of the ‘tool‐kit’ needed to manage environmental weeds in Australia and New Zealand, comparing and contrasting the approaches taken in the two countries. It also provides a broad framework for the case studies that make up this special issue on the ecology and management of environmental weeds in both countries.
Demography of the invasive shrub Scotch broom (Cytisus scoparius) at Barrington Tops, New South Wales: insights for management.
Authors: Downey P. O. , Smith J. M. B.
Published: March 2003

The exotic shrub Scotch Broom (Cytisus scoparius) has invaded large areas of eucalypt woodland at Barrington Tops, New South Wales, where it forms dense stands that have significant impacts on vegetation structure, flora and fauna. Data are presented from four 25 m2 plots, which have been studied since 1985. Two plots were located in uniform broom thickets of different ages, and two were located across the margins of broom stands, which have since expanded to cover the entire plots. All broom plants in the plots (other than young seedlings, which were counted) were mapped, tagged and monitored annually. New seedlings appeared annually, but there was no relationship between their numbers (varying between years) and subsequent recruitment of older plants. The probability of seedlings reaching first flowering was less than 2%, and of surviving to mature size (>10 cm2 basal area) was negligible. Seedlings mainly died through suppression (shade). Individuals less than 50 cm high were also browsed. Recruitment occurred only where light levels were high, either before closure of the broom canopy or after senescence had led to canopy opening. From approximately 12–30 years after initial invasion, broom stands underwent self‐thinning of mature plants, accelerated by collapse of plants on to each other. Recruitment of new, maturing plants, after this period produced a stand that was less dense than that found after initial invasion. Broom is creating more disturbance‐prone environments due to its impacts on other biota, likely alterations to the fire regime, and by harbouring feral pigs. Further disturbance favours broom, and elsewhere it has resulted in massive seedling regeneration. While fire or other disturbance can be used to stimulate germination, and thereby reduce a large part of the soil seed bank, denser broom infestations are likely to result unless follow‐up treatments can be applied over long time periods. A wiser management option, at least in the short term, may be avoidance of all disturbance, especially for stands of mature broom.
Predicting potential impacts of environmental flows on weedy riparian vegetation of the Hawkesbury–Nepean River, south‐eastern Australia
Authors: Howell Jocelyn , Benson Doug
Published: March 2003

Remnants of native riparian vegetation on the floodplain of the Hawkesbury–Nepean River near Sydney, have significant conservation value, but contain a large component of weeds (i.e. exotic species that have become naturalized). A proposal for the introduction of environmental flows required an assessment of potential impacts on 242 native and 128 exotic species recorded along 215 km of the river. The likely effects of frequency, season, depth and duration of inundation were considered in relation to habitat, dispersal season and tolerance to waterlogging. Overseas studies provided only limited information applicable to the study area; however, comparisons with similarly highly modified riparian habitats in New Zealand were instructive. Depth and season of inundation appear to be the variables with the greatest potential for differential effects on weeds and native plants. Because of likely spread of propagules and enhancement of growth under the present nutrient‐enriched conditions, environmental flows that would cause more frequent flooding to higher levels of the riparian zone were judged to be of more benefit to weed species than native species, unless supported by bushland management including weeding. Predictions were limited by incomplete data on Hawkesbury–Nepean species, but two types of environmental flow were judged to be potentially beneficial for native water‐edge plants, and worth testing and monitoring: first, flows that maintain continuous low‐level flow in the river, and second, higher level environmental flows restricted to the river‐edge habitat in autumn (the season in which a greater proportion of native species than weed species are known to disperse propagules). In summary, the presence of environmental weeds in riparian vegetation constrain the potential for environmental flows to improve river health. However, with ongoing monitoring, careful choice of water level and season of flow may lead to environmental flows that add to our knowledge, and benefit riparian vegetation along with other river system components.
Inhibition of Ageratina riparia (Asteraceae) by native Australian flora and fauna
Authors: Zancola Brian J. , Hero Clyde Wild and Jean‐Marc
Published: March 2003

We investigated the influence of native flora and fauna on the establishment and persistence of the exotic weed Ageratina riparia (Asteraceae) in disturbed and regenerating rainforests on the Springbrook plateau of south‐eastern Queensland. The height and ground cover of A. riparia was positively associated with light availability beneath the rainforest canopy and negatively associated with forest leaf litter biomass. Regenerating rainforest with the associated increases in litter and decrease in light availability could therefore inhibit the establishment and density of A. riparia. The red‐necked pademelon, Thylogale thetis, browsed extensively on A. riparia, but the pattern of browsing was not associated with light availability, forest leaf litter biomass or density of A. riparia. Browsing and incidental damage by T. thetis breaks up the broad stands of A. riparia. The physical damage caused by T. thetis, and the inhibition to establishment and density of A. riparia by native plant species, combine to reduce the environmental threat associated with A. riparia.
Effects of smoke, heat and charred wood on the germination of dormant soil‐stored seeds from a Eucalyptus baxteri heathy‐woodland in Victoria, SE Australia
Authors: Enright N. J. , Kintrup A.
Published: March 2003

The effects of dry heat, wet heat, charred wood and smoke on the germination of dormant soil‐stored seeds from a Eucalyptus woodland in western Victoria were tested by using a glasshouse seed‐bank germination experiment. Seedling density, species richness and species composition were compared between replicated treated and control samples. A total of 5922 seedlings, comprising 59 plant species, was recorded from the soil samples over a period of 150 days. While a few species dominated (including Centrolepis strigosa, Wahlenbergia gracilenta and Ixodia achillaeoides), 26 species were represented by fewer than five seedlings and 18 species were restricted to single treatment types. With the exception of charred wood, all treatments led to a significant increase in seed germination relative to the control. The highest number of germinants was obtained for the smoke treatment, with a mean (± SE) of 12 547 ± 449 seedlings m–2. Heat treatments yielded intermediate densities, with means (± SE) varying between 7445 ± 234 and 9133 ± 445 seedlings m–2. In comparison with the estimates of seed‐bank sizes from other fire‐prone ecosystems, these densities are high. Species richness differed significantly among treatments. Highest mean richness was recorded in the smoke treatment and lowest for the control and charred wood treatments. There were significant differences in seed‐bank species composition between treatment types based on analysis of similarity (Anosim) using Bray–Curtis similarity. While heat was a specific requirement for triggering germination in hard‐seeded species (e.g. Fabaceae), smoke was the most effective trigger for species from a broad range of other families. The potentially confounding effect of physical and chemical mechanisms of germination stimulation in heated bulk soil samples is raised as an issue requiring further investigation in relation to the role of smoke as a germination trigger.
Fish assemblage stability in an intermittently flowing stream from the Brazilian semiarid region
Authors: Medeiros Elvio S. F. , Maltchik Leonardo
Published: March 2003

Flooding and drought are important hydrological disturbances occurring in intermittent streams located in semiarid regions. The present study aims to analyse the effects of flood and drought on the diversity and stability of an intermittent stream fish community from the Brazilian semiarid region over the 1996 hydrological cycle. Fourteen fish collections were conducted during the rewetting, wet and drying phases, and 808 individuals were collected. Diversity was measured by using Simpson’s Index (S) and community stability was analysed by using the variation in the abundance, then tested by applying Kendall’s (W) test of concordance over the relative abundance rankings. This test supplies information about the stability of communities by means of the concordance of rankings. A community that is stable or near equilibrium has more constant rankings of its constituent species compared with a fluctuating one. The diversity increased progressively during the rewetting phase (S = 0.480–0.693; coefficient of variation = 0.131), reached its highest values during the wet phase (S = 0.745–0.861; coefficient of variation = 0.072), and remained high during the drying phase, with a lower oscillation than in the other phases (S = 0.699–0.801; coefficient of variation = 0.050). The abundance per collection varied significantly (Kruskal– Wallis 6.94, P = 0.031) throughout the hydrological phases. The stability of the community was higher during the rewetting (W = 0.58, P < 0.001) and drying (W = 0.86, P < 0.001) phases than during the wet phase (W = 0.45, P = 0.1818). In the Brazilian semiarid region, flooding disrupted the stability of the fish community studied and increased the diversity, whereas the absence of floods (expressed by the drying phase) caused a higher stability of the fish community and led to less variation in diversity.
Processes involved in species saturation of ground‐dwelling ant communities (Hymenoptera, Formicidae)
Authors: Soares Sandra M. , Schoereder José H. , DeSouza Og
Published: March 2003

The species saturation hypothesis in ground‐dwelling ant communities was tested, the relationship between local and regional species richness was studied and the possible processes involved in this relationship were evaluated in the present paper. To describe the relationship between local and regional species richness, the ground‐dwelling ant fauna of 10 forest remnants was sampled, using 10 1 m2quadrats in each remnant. The ants were extracted from the litter by using Winkler sacs. Using regression analyses, an asymptotic pattern between local and regional species richness was detected. This saturated pattern may be related to three processes: (i) high interspecific competition; (ii) habitat species specialization; or (iii) stochastic equilibrium. It is concluded that non‐interactive processes, such as stochastic equilibrium and habitat specialization may act as factors regulating species richness in this community. The predominance of locally restricted species, in all sampled remnants, seems to indicate the occurrence of a high degree of habitat specialization by the ant species. This result is evidence for the hypothesis that community saturation has been generated by non‐interactive processes. Although ants are frequently described as highly interactive, it is possible that interspecific competition is not important in the structuring of ground‐dwelling ant communities.
Biophysical and human influences on plant species richness in grasslands: Comparing variegated landscapes in subtropical and temperate regions
Authors: Mcintyre S. , Martin T. G.
Published: March 2003

A survey of grassy woodlands in the Queensland subtropics was conducted, recording herbaceous species richness at 212 sites on three properties (2756 ha). A range of habitats typical of cattle grazing enterprises was sampled and site variables included lithology, slope position, tree density, soil disturbance, soil enrichment and grazing. Results were compared with a previously published survey of temperate grasslands. Lithology, slope position and tree density had relatively minor effects on plant species richness, although in both surveys there was some evidence of lower species richness on the more fertile substrates. Soil disturbance and soil enrichment significantly reduced the richness of native species in both surveys, while exotic species were insensitive (subtropics) or increased (temperate) with disturbance. Rare native species were highly sensitive to disturbances, including grazing, in the temperate study. Although some trends were similar for rare species in the subtropics, the results were not significant and there were complex interactions between grazing, lithology and slope position. Grazing did not have a negative effect on native species richness, except in the closely grazed patches within pastures, and then only on the most intensively developed property. At the scale recorded (30 m2), the native pastures, roadsides and stock routes sampled in the subtropics appear to be among the most species‐rich grasslands ever reported, both nationally and globally. Native species richness was approximately 50% higher than the temperate survey figures across all the comparable habitats. While there are no clear reasons for this result, potential explanations are proposed.
Idiosyncratic phenomenon of regeneration from cotyledons in the idiot fruit tree, Idiospermum australiense
Authors: Edwards Will , Gadek Paul , Weber Ellen , Worboys Stuart
Published: March 2003

Idiospermum australiense (Diels) S. T. Blake, is a rare species that produces very large diaspores (up to 225 g) comprising 2–6 cotyledons. Anecdotal evidence suggested that each cotyledon within the diaspore could develop an independent root/shoot axis in natural populations and under glasshouse conditions. To investigate this potential, 13 diaspores were collected. Six diaspores were kept intact and cotyledons in the remaining seven were separated, planted into soil and scored for germination. All shoots were allowed to grow for 12 weeks. To test for differences in growth response from seedlings emerging from intact diaspores and single cotyledons, plant height, shoot mass, stem mass, leaf mass and total leaf area were compared between groups using both absolute values and values standardized to initial reserve mass. To examine the effects of reserve mass in more detail, height to stem mass, leaf mass to stem mass and specific leaf area was also compared between groups. All intact cotyledons and 24 of the 27 single cotyledons produced a functional root/shoot system. Time to germination was not different between groups. Shoot mass, stem mass and leaf mass were significantly greater in intact diaspores than in single cotyledons, although no difference was found in any parameter when standardized to initial reserve mass. Shoots arising from individual cotyledons were significantly taller per gram initial weight, because of a significantly greater relationship between height and stem mass. Shoots arising from single cotyledons also had a significantly greater investment in leaf mass per unit stem mass, even though there was no difference in specific leaf area between groups. Thus, seedlings arising from individual cotyledons grew relatively taller and produced a greater area of leaf tissue relative to stem than those arising from intact diaspores.
Effect of an exotic Acacia (Fabaceae) on ant assemblages in South African fynbos
Authors: French Kristine , Major Richard E.
Published: March 2003

Ant assemblages in South African fynbos invaded by Acacia saligna were compared with ant assemblages in undisturbed fynbos to determine whether ant assemblages change under exotic plants that produce ant‐dispersed seeds. Overall, no differences in the species richness of ants were found between weed‐infested and native sites but there were differences in both ant abundance and the composition of the ant assemblage. Ants were much less abundant in weed‐infested sites. To investigate whether changes in ant assemblages in weed‐infested areas could be due to a preference for native seeds over exotic seeds, seeds of a range of species were offered to ants and ants that handled seeds were identified. Thirteen species of ants handled A. saligna seeds and there was no evidence to suggest that the ant assemblage as a whole preferred native seeds to A. saligna seeds. Hypotheses that may account for this pattern are discussed.
Modelling life history strategies with capture–recapture data: Evolutionary demography of the water skinkEulamprus tympanum
Authors: Blomberg Simon P. , Shine Richard
Published: March 2003

Matrix population models, elasticity analysis and loop analysis can potentially provide powerful techniques for the analysis of life histories. Data from a capture–recapture study on a population of southern highland water skinks (Eulamprus tympanum) were used to construct a matrix population model. Errors in elasticities were calculated by using the parametric bootstrap technique. Elasticity and loop analyses were then conducted to identify the life history stages most important to fitness. The same techniques were used to investigate the relative importance of fast versus slow growth, and rapid versus delayed reproduction. Mature water skinks were long‐lived, but there was high immature mortality. The most sensitive life history stage was the subadult stage. It is suggested that life history evolution inE.tympanummay be strongly affected by predation, particularly by birds. Because our population declined over the study, slow growth and delayed reproduction were the optimal life history strategies over this period. Although the techniques of evolutionary demography provide a powerful approach for the analysis of life histories, there are formidable logistical obstacles in gathering enough high‐quality data for robust estimates of the critical parameters.
Changes in mammal populations in relatively intact landscapes of Kakadu National Park, Northern Territory, Australia
Authors: Woinarski J. C. Z. , Milne D. J. , Wanganeen G.
Published: March 2003

A previous study (Braithwaite & Muller 1997) reported substantial declines in mammal abundance over the period 1986–1993 for a large study area (300 km2) within Kakadu National Park in the tropical savannas of northern Australia. This decline was reported as being a ‘natural’ response to fluctuating groundwater levels, driven by runs of poor wet seasons. We resampled mammals in this area in 1999, following a series of unusually good wet seasons, and examined the prediction that mammal numbers should have recovered. Increases in abundance were evident for four species: the smallest dasyurid (red‐cheeked dunnart Sminthopsis virginiae) and the three smallest rodents (delicate mouse Pseudomys delicatulus, western chestnut mouse Pseudomys nanus and grassland melomys Melomys burtoni). In contrast, the abundance of all mammals combined and that for seven individual mammal species (northern quoll Dasyurus hallucatus, fawn antechinus Antechinus bellus, common brushtail possum Trichosurus vulpecula, northern brown bandicoot Isoodon macrourus, dusky rat Rattus colletti, black‐footed tree‐rat Mesembriomys gouldii and pale field rat Rattus tunneyi) continued to decline. The decline in abundance of these mammal species is consistent with limited observations elsewhere in northern Australia. Although far from conclusive, these observations suggest that the biota of the vast relatively undisturbed tropical savannas can no longer be assumed to be intact nor safe. Further research is needed to test this possible pattern of decline and, if confirmed, to identify and ameliorate the processes contributing to it.