bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

Abstract 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

AbstractAnt 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

AbstractMatrix 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

AbstractA 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.
Distribution and persistence of temporary wetland habitats in arid Australia in relation to climate
Authors: Roshier D. A. , Whetton P. H. , Allan R. J. , Robertson A. I. 
Published: March 2003

AbstractThe distribution and area of temporary wetlands across the arid zone of Australia are highly variable. Any change in their distribution or extent due to climate change and/or extraction of water has the potential to adversely impact dependent biota. Satellite imagery was used to determine the spatial and temporal distribution of wetlands across arid Australia over an 11‐year period. Synoptic climate data were examined to identify the weather systems that caused wetland filling events. Simple threshold models relating rainfall to wetland filling for seven large regions of Australia were developed to examine patterns of wetland filling over the last 100 years. These data were used to examine the climatic processes that drive wetland filling and the likely impacts of climate change on wetland distribution. The strongest climatic influence on wetland filling in the arid zone was tropical weather systems. Their influence extended into southern regions and their effects were often widespread. Variation in wetland area in all regions of the arid zone was high. The Lake Eyre Basin experienced more large flood events than other regions and had the most large, persistent wetlands that remain unregulated by humans. Hindcasting of past filling events indicated that there was a general pattern of frequent wetland filling across inland Australia in the 1910s, 1950s and 1970s, and less frequent wetland filling in the late 1920s, 1930s and 1960s. Furthermore, there appeared to be no period greater than 12 months over the previous 95 years when there was no predicted wetland filling in the arid zone. Wetland ecosystems dependent on a few infrequent heavy rainfalls are clearly vulnerable to any change in frequency or magnitude of these events. Climate change that results in a drying or reduced frequency of large flood events, exacerbated by extraction of water for agriculture, could be catastrophic for some biota, particularly waterbirds, which use a mosaic of wetland habitat at broad spatial scales.
Variation in the guild composition of herbivorous insect assemblages among co‐occurring plant species
Authors: Peeters Paula J. , Read Jennifer , Sanson Gordon D. 
Published: March 2003

AbstractVariation in plant traits among plant species may promote the development of a characteristic functional assemblage of insect herbivores associated with each plant species. However, only a small number of studies have detailed the representation of several herbivore guilds among co‐occurring plant species to determine whether the functional structure of herbivorous insect assemblages varies widely and consistently among plant species. The present study provides one of the few published data sets reporting on the density of several guilds of insect herbivores among numerous plant species. Variation in guild associations with plant phenology and season are also described. Insect herbivores were divided into 10 guilds, and the representation of these guilds was examined for 18 co‐occurring plant species. Guild densities and assemblage composition varied significantly among plant species, even when variation over time was taken into account. Variation in guild densities and assemblage composition were not strongly related to the taxonomic relationships of the plants. The highest densities of several guilds occurred in spring and summer, although other guilds were not strongly seasonal. Certain guilds were strongly associated with the presence of new leaves, whereas other guilds appeared to prefer mature leaves. This resulted in assemblage differences between samples containing new and mature leaves and samples containing mature leaves only. Even though the timing and duration of leaf and flower production varied among plant species, this did not explain all variation in guild densities among plant species. It is suggested that additional factors, including plant traits, are contributing to the wide and consistent variation in herbivore assemblage composition among plant species.
Experiments on the mechanism of tree and shrub establishment in temperate grassy woodlands: Seedling emergence
Authors: Clarke Peter J. , Davison Elizabeth A. 
Published: March 2003

AbstractField experiments were designed to examine tree and shrub seedling emergence in temperate grassy woodlands on the New England Tablelands. The effects of study sites, intensity of previous grazing, removal of ground cover by fire or clearing, burial of seeds and ant seed theft on seedling emergence were tested in two field experiments. Six tree and seven shrub species were used in the experiments and their cumulative emergence was compared with laboratory germination studies. All species used in field experiments had lower cumulative emergence than those in laboratory germination studies despite prolonged periods of above average rainfall before and after seeds were sown. Eucalypt species emerged faster in the field than the shrub species and generally attained higher cumulative emergence than the shrubs. Spatial effects of sites and patches within sites, and of previous grazing history did not strongly influence patterns of seedling emergence in most species. Ground and litter cover generally did not enhance or suppress the emergence of seedlings, although the removal of cover in recently grazed areas enhanced the emergence of some species. Burning enhanced the emergence of some tree and shrub species where plots had more fuel and intense fires, but this effect was not strong. Compared with other treatments, seedbed manipulations produced the strongest effects. In the absence of both invertebrate and vertebrate predators, seedling emergence was lower for surface‐sown seed, compared with seed sown on scarified soil surfaces. Higher seedling emergence of buried seeds in the presence of invertebrate predators probably resulted from the combined effects of predator escape and enhanced moisture status of the germination environment. Some promotion of emergence was achieved for all species in most sown treatments probably as a result of a prolonged above average rainfall. In contrast, the natural recruitment of trees and shrubs was negligible in experimental plots, highlighting the importance of seed supply and dispersal as ultimate determinants of recruitment.
Vegetation patterns, plant distribution and life forms across the alpine zone in southern Tierra del Fuego, Argentina
Authors: Mark Alan F. , Dickinson Katharine J. M. , Allen Jan , Smith Rob , West Carol J. 
Published: March 2003

AbstractThe alpine zone is examined at meso‐ and microscales in southern Tierra del Fuego (54°49′S), where the full zone is expressed. Mesoscale patterns were studied on opposing aspects, and microscale patterns were studied on a series of solifluction terraces, in a hanging valley overlooking the Beagle Channel. Plant cover and life form data were collected within 50‐m altitudinal bands on north and south aspects and comprehensive plant lists were compiled for each band. Topography and associated surface cover were recorded on the terraces. Six alpine plant communities, in lower and upper floristic zones, were differentiated with multivariate analyses and significantly related to five ecological factors. Equivalent communities were separated by approximately 185 m altitude on opposing aspects, which related to a soil temperature difference of approximately 3.0°C. The richness (and range) of 80 local vascular taxa (18.6% of the regional flora), decreased with increasing altitude (6.6 per 100 m); however, richness differed significantly with aspect (north: 5.6, south: 7.5). Upper altitudinal limits (approximately 1250 m a.s.l.), were associated with a midsummer isotherm of approximately 1.7°C. Chamaephytes and hemicryptophytes dominated throughout but the tall tussock form was conspicuously absent. Reasons for this are discussed in the context of the Nothofagus treeline, which conformed to a midsummer isotherm of only approximately 6.0°C. Such patterns are at variance with those found in the oceanic subantarctic islands, other oceanic perhumid temperate mountain regions and tropical high mountains. However, the microscale pattern of fines, pebbles, stones and rock across the active solifluction terraces, with dense vegetation on their steep risers, had a clear affinity with that of other subantarctic regions. Inferences that alpine systems of the Southern Hemisphere are necessarily equivalent to those at similar northern latitudes are cautioned against. Likewise, such comparisons within the Southern Hemisphere may also be invalid.
Benefits and risks of biotic exchange between Eucalyptus plantations and native Australian forests
Authors: Strauss Sharon Y. 
Published: March 2003

AbstractAustralia is unique in having two highly diverse plant genera, Eucalyptus and Acacia, that dominate the vegetation on a continent‐wide scale. The recent shift in plantation forestry away from exotic Pinus radiata to native Eucalyptus species has resulted in much more extensive exchange of biota between native forest and plantation ecosystems than exchange in the past with plantations of exotic species. Growing numbers of hectares are being planted to Eucalyptus globulus across Australia, and plantations are providing resources and corridors for native biota. The present paper focuses on both the benefits and risks of having large‐scale forestry plantations of native species that are closely related to dominant native taxa in local forests. At least 85 species of insects have been recorded as pests of Eucalyptus plantations around Australia; the vast majority of these have been insects using the same host species, or closely related taxa, in native forests. Plantations of native species may also benefit from closely related local forests through the presence of: (i) the diverse array of ectomycorrhizal fungi favourable for tree growth; (ii) natural enemies harboured in native habitats; and (iii) recruitment of other important mutualists, such as pollinators. Exchanges work in two directions: plantations are also likely to influence native forests through the large amount of insect biomass production that occurs in outbreak situations, or through the introduction or facilitation of movements for insects that are not native to all parts of Australia. Finally, older plantations in which trees flower may exchange genes with surrounding forest species, given the high degree of hybridization exhibited by many Eucalyptus species. This is an aspect of exchange for which few data have been recorded. In summary, because of Australia’s unique biogeography, plantation forestry using eucalypt species entails exchanges with natural habitats that are unparalleled in scale and diversity in any other part of the world. More exchanges are likely as plantations occupy greater area, and as the time under cultivation increases.
Sensitivity of tropical forests to climate change in the humid tropics of north Queensland
Authors: Hilbert David W. , Ostendorf Bertram , Hopkins Mike S. 
Published: March 2003

AbstractAn analysis using an artificial neural network model suggests that the tropical forests of north Queensland are highly sensitive to climate change within the range that is likely to occur in the next 50–100 years. The distribution and extent of environments suitable for 15 structural forest types were estimated, using the model, in 10 climate scenarios that include warming up to 1°C and altered precipitation from –10% to +20%. Large changes in the distribution of forest environments are predicted with even minor climate change. Increased precipitation favours some rainforest types, whereas decreased rainfall increases the area suitable for forests dominated by sclerophyllous genera such as Eucalyptus and Allocasuarina. Rainforest environments respond differentially to increased temperature. The area of lowland mesophyll vine forest environments increases with warming, whereas upland complex notophyll vine forest environments respond either positively or negatively to temperature, depending on precipitation. Highland rainforest environments (simple notophyll and simple microphyll vine fern forests and thickets), the habitat for many of the region’s endemic vertebrates, decrease by 50% with only a 1°C warming. Estimates of the stress to present forests resulting from spatial shifts of forest environments (assuming no change in the present forest distributions) indicate that several forest types would be highly stressed by a 1°C warming and most are sensitive to any change in rainfall. Most forests will experience climates in the near future that are more appropriate to some other structural forest type. Thus, the propensity for ecological change in the region is high and, in the long term, significant shifts in the extent and spatial distribution of forests are likely. A detailed spatial analysis of the sensitivity to climate change indicates that the strongest effects of climate change will be experienced at boundaries between forest classes and in ecotonal communities between rainforest and open woodland.
Long‐term population dynamics of a coral reef gastropod and responses to disturbance
Authors: Catterall Carla P. , Poiner Ian R. , O'Brien Christopher J. 
Published: March 2003

AbstractThe age‐specific density of the red‐lipped stromb Strombus luhuanus (Mollusca: Gastropoda) was monitored over 13 years (1981–1993) at four locations on the intertidal reef flat at Heron Island, Great Barrier Reef. Densities were highly variable, but there were persistent, location‐specific differences in population density, age structure and adult body size, the latter indicating that the populations were not extensively linked by adult movement. There was relatively high recruitment at most locations in 1984, 1989 and 1993, each occurring approximately 2 years after El Niño/Southern Oscillation events, although recruit density during these years varied in both space and time. The studied strombs experienced three disturbance events: (i) experimental harvesting at two locations (1984–1985); (ii) siltation from a harbour dredging operation (1987–1988); and (iii) a severe cyclone (1992). Resilience to harvesting at a local scale (0.5–2 ha) was high: density had recovered within a year, due to immigration of adults and older juveniles. Strombus luhuanus responded much more strongly to broad‐scale changes to its environment than to localized harvesting. After dredging, there was a progressive density decline coupled with low recruitment at two locations, and a later decline at a third location, followed by a recruitment‐driven rebound after the cyclone. Generalized environmental effects of siltation and the cyclone were also reflected in substantial changes in algal cover. Long‐term variations in environmental conditions probably cause high temporal variation over large spatial scales through effects on the survival of larvae or recruits. Localized short‐term field monitoring of such species would give a misleading picture of key factors affecting population dynamics.
Reducing the impact of insect herbivory in eucalypt plantations through management of extrinsic influences on tree vigour
Authors: Stone Christine 
Published: March 2003

AbstractIn this paper it is argued that concepts developed in ecologically derived insect–plant interaction models can contribute directly to the management of insect herbivory in eucalypt plantations. Common to most species of commercially planted eucalypt is their genetic potential for early rapid growth. Several plant defence theories predict that intrinsically fast growing plants are able to tolerate relatively high levels of herbivory. The risk of this strategy failing increases when plants are exposed to external stressful factors that reduce canopy growth and vigour. Results from a young Eucalyptus camaldulensis plantation stressed by moisture deficit and two young Eucalyptus dunnii plantations, stressed by flooding and weed competition, respectively, are summarized. In all three cases, the stress‐inducing agents reduced canopy growth rates and architecture so that the proportion of leaf tissue damaged by insects increased and the tree’s ability to tolerate this damage decreased. Therefore, alleviating tree stress through improved silvicultural practices or improved site selection techniques may indirectly reduce the impact of insect herbivory. In resource‐limiting environments, an alternative approach may be to plant eucalypt species that although slower growing, are predicted to have better defended foliage. Manipulation of these natural antiherbivore plant strategies are not exclusive of other management approaches, such as the need for routine surveillance of key pest insects or the genetic selection of natural insect resistance and selective chemical control techniques, but should be viewed as an overarching concept for plantation health.