bluuebunny/crossref_metadata_2025_split huggingface dataset:
Population dynamics of the shrub Acacia suaveolens (Sm.) Willd.: Fire and the transition to seedlings
Authors: AULD TONY D. 
Published: July 2006

AbstractFire, through soil heating effects, causes flushes of seed germination in Acacia suaveolens. Optimal temperatures for germination are between 60 and 80°C for any duration, or up to 100°C for durations less than 1 h. Exposure to temperatures less than 60°C leaves seeds dormant and viable, whilst seed death occurs in increasing proportions with increasing exposure to temperatures greater than 80°C.A field study of temperatures in the soil under simulated burns showed that the innate seed dormancy in A. suaveolens would only be broken for seeds up to a depth of 1 cm in ‘cool’ or 4 cm in ‘hot’ burns. In the hot burns some of the seeds in the top 1 cm of the soil were killed by excessive heating. These simulated burns most resemble cool and moderate/high intensity wildfires, respectively. Seeds can emerge from depths up to 8 cm and, for any seeds buried deeper than this, the probability of emergence is progressively reduced down to nil at 14 cm. Seeds buried between 5 and 10 cm will be heated sufficiently to break their dormancy only in a very high intensity wildfire. Seeds buried between 5 and 10 cm deep mostly occur in nests of an ant, Pheidole sp.Field observations of emergent seedlings confirm that post‐fire emergence is concentrated over a small range of soil depths directly related to the intensity and duration of heating that occurs, whilst occasional seedlings may appear from greater or lesser depths largely dependent upon the spatial heterogeneity of soil heating in natural fires.
Stemflow as a nutrient source for nikau palm (Rhopalostylis sapida) in a New Zealand forest
Authors: ENRIGHT N. J. 
Published: July 2006

Abstract The hypothesis that stemflow is important in contributing to the nutrient requirements of nikau palm Rhopalostylis sapida individuals is examined. Stemflow directs many times more sodium, potassium, calcium and magnesium to the base of the palm than is required for annual net production. There are three sources for nutrients found in stemflow: (1) atmospheric inputs (wet and dry deposition); (2) foliar leaching; and (3) alien litter leaching and decomposition. Sources I and 3 together, representing nutrient input, contribute substantially more nutrients than are required for net annual production in mature individuals.
Densities of Collembola and Acarina in the soil and litter of three indigenous South Australian forests related to layer, site and seasonal differences
Authors: HUTSON BARRY R. , VEITCH L. G. 
Published: July 2006

AbstractA quantitative study was made of the micro‐arthropod fauna in the litter and two soil layers at three South Australian forest sites (designated ‘dry’ medium’ and ‘wet’) using data taken at monthly intervals over 2 years. This study examined variations in density estimates of the major taxonomic groups of Acarina and Collembola that were associated with sample depth, site and season.There were substantial differences in the proportions of variation attributed to layer, site and seasonal effects. Most variation was associated with layer differences, being greatest in the acarine Prostigmata and in the collembolan Onychiuridae. Only the acarine Astigmata had slightly more variation between sites than between layers.Seasonal variation exceeded site variation in all collembolan groups except the Entomobryidae. In the acarine groups estimated ratios of seasonal to site variation were 6.1, 1.6, 1.0 and 0.4 for the Mesostigmata, Prostigmata, Cryptostigmata and Astigmata, respectively.Some variations due to inconsistencies in the above patterns were significant statistically but were small compared with variations associated with the seasonal, layer and site effects.Densities of all animals had marked seasonal variation which was broadly similar to that of rainfall in the warm temperate, mediterranean type climate of the region. Minimum density and activity occurred in about the last week in January, a period of maximum temperature and low soil moisture content; maxima were usually about 7 months later. This contrasts with warm and cool temperate areas of Australia with summer rainfall, where peak densities have been recorded in summer.The Mesostigmata, Astigmata, Podundae and Onychiuridae patterns of seasonal variation did not differ significantly with layer or site differences. The remaining groups had significant differences with layers and sites, the former being larger. Density minima and maxima were generally later going from litter to lower soil, about 2.5–8 weeks for density maxima and 0–4 weeks for minima. Groups with significant lags showed reduced amplitude in their seasonal variation with increased depth.There was little seasonal variation in the relative proportions of all animal groups.
Effects of an epiphytic alga on abundances of fish and decapods associated with the seagrass Zostera capricorni
Authors: BELL JOHANN D. , WESTOBY MARK 
Published: July 2006

Abstract During a field experiment to test effects of changes to leaf height and density of Zostera capricorni on associated fish and decapods, more than one‐third of the substratum at some sites was covered by the epiphytic brown alga Giffordia mitchelliae. This paper reports apparent effects of the alga on the 13 most abundant species of fish and decapods, and interactions between effects of the alga and those due to height and density of the seagrass leaves. Abundances of three species were significantly lower, and those of two species were significantly greater where the alga occurred. There were interactions between effects of the alga and those of leaf height and/or density for another four species. In all four cases, when the alga had an effect, it was to decrease abundance. The effects of Giffordia were generally opposite to those reported for drift algae in seagrass habitats elsewhere. The lower abundances of seven species where algal cover was great are best explained by an existing model for seagrass habitats that predicts reductions in abundance of individuals when the ratio of plant material to substratum is very high.
The biomass of New England peppermint (Eucalyptus nova‐anglica) in relation to insect damage associated with rural dieback
Authors: LOWMAN M. D. , BURGESS A. D. , HIGGINS W. D. 
Published: July 2006

Abstract Two adjacent mature trees of New England peppermint (Eucalyptus nova‐anglica) were harvested with the aid of a cherry picker to determine their biomass distribution and insect damage. One suffered from obvious symptoms of rural dieback and the other was healthy. Weights of foliage and wood were measured, and insect damage for all leaves and branches was quantified. For each tree 25% of the roots were extracted from the soil using a bulldozer and manual methods; they were then weighed and damage by insects estimated. The healthy tree lost more leaf surface area to insects (11% or 1.1 kg vs 9.2% or 0.3 kg); but the dieback tree had four times more wood affected by boring insects (19% cf. 5%); and only 20% root biomass remaining (92 kg cf. 488 kg). The accuracy of sampling techniques needed to measure defoliation and the consequences of insect damage to dieback of rural eucalypts are discussed.
Analysis of the development of major plagues of the Australian plague locust Chortoicetes terminifera (Walker) using a simulation model
Authors: WRIGHT D. E. 
Published: July 2006

Abstract The development and decline of all the past major plagues of Chortoicetes terminifera in Australia has been analysed using all available locust data and a simulation model to estimate the course of events for periods when few locusts were reported. The model is based on the developmental biology of the locust and includes methods of estimating the duration of egg, nymphal and adult development and uses a pasture growth index and potential night displacement index to assess likely survival and migration.The analysis shows that five of the six plagues originated in the arid interior, where good spring and summer rain allowed two or three consecutive generations of successful breeding, before emigration to the agricultural country occurred in the late summer or early autumn. This is contrary to the idea held previously that most plagues developed from local breeding in established outbreak areas in the agricultural belt. The applications of these results, to improve population monitoring and control strategy by suggesting the best timing for surveys and when control would have most effect, are discussed.
Effect of disturbance and nutrient addition on native and introduced annuals in plant communities in the Western Australian wheatbelt
Authors: HOBBS R. J. , ATKINS L. 
Published: July 2006

AbstractTo investigate factors affecting the ability of introduced species to invade natural communities in the Western Australian wheatbelt, five communities were examined within a nature reserve near Kellerberrin. Transect studies indicated that introduced annuals were more abundant in woodland than in shrub communities, despite an input of introduced seed into all communities. The response of native and introduced annuals to soil disturbance and fertilizer addition was examined. Small areas were disturbed and/or provided with fertilizer prior to addition of seed of introduced annuals. In most communities, the introduced species used (Avena fatua and Ursinia anthemoides) established well only where the soil had been disturbed, but their growth was increased greatly when fertilizer was also added. Establishment and growth of other introduced species also increased where nutrient addition and soil disturbance were combined. Growth of several native annuals increased greatly with fertilizer addition, but showed little response to disturbance. Fertilizer addition also significantly increased the number of native species present in most communities. This indicates that growth of both native and introduced species is limited by nutrient availability in these communities, but also that introduced species respond more to a combination of nutrient addition and soil disturbance.
Predation creates haloes of bare space among prey on rocky seashores in New South Wales
Authors: FAIRWEATHER PETER G. 
Published: July 2006

AbstractField observations on rocky shores in New South Wales suggested a link between pools or wet crevices, predatory whelks foraging from them, and areas around the crevices that were mostly bare of prey (‘haloes’). Whelks were most common in and around crevices but ventured out to feed. Previous work had shown that foraging excursions were cyclical over time. The community of prey also changed with distance from crevices, most types of prey being more abundant further away. A field experiment showed this pattern to be at least partly due to the crevice‐bound foraging of the whelks. Experimental removal of whelks over 2 years at several sites caused the gradients in the abundance of prey with distance from crevices to disappear, whilst these patterns persisted and even grew more intense in adjacent control areas. This combination of biotic and physical processes (predation, desiccation, foraging behaviour) is discussed as an important influence on spatial patterning in this and other communities.
The effects of rabbit grazing on regeneration of sheoaks, Allocasuarina verticilliata and saltwater ti‐trees, Melaleuca halmaturorum, in the Coorong National Park, South Australia
Authors: COOKE B. D. 
Published: July 2006

AbstractSheoaks and saltwater ti‐trees regenerate poorly within the Coorong National Park unless they are protected from grazing mammals. The age structure of these tree populations suggests that both species regenerated vigorously in the 1950s when myxomatosis kept rabbit numbers low. Experiments demonstrated that unprotected seedlings are quickly found and eaten by rabbits, particularly if alternative foods are scarce.Sufficient numbers of ti‐trees are presently recruited to ensure the persistence of that species, but a programme of rabbit control would be necessary to enable natural regeneration to perpetuate the sheoak population in the Coorong National Park.
Pollination ecology of Christmas Bells (Blandfordia nobilis): Effects of pollen quantity and source on seed set
Authors: ZIMMERMAN MICHAEL , PYKE GRAHAM H. 
Published: July 2006

AbstractThe effect of a number of experimental handpollination regimens on the numbers of seeds set by Blandfordia nobilis flowers was assessed. Individuals were found to be self‐incompatible and to require pollinator visits to set fruit. Pollen limited the female component of reproduction in the two populations studied while pollen source did not have a significant effect on the numbers of seeds set. Experiments using a stuffed honeyeater indicated that maximal seed set could be achieved after just one probe by the pollinator. Appreciable heterogeneity in flowering phenology, the number of seeds naturally setting and the number of seeds setting as a result of hand‐pollinations existed within a small area across a single flowering season.
The crown‐gap ratio (C) and crown cover: The field study
Authors: WALKER J. , CRAPPER P. F. , PENRIDGE L. K. 
Published: July 2006

AbstractCrown cover can be used to describe or classify woody vegetation. However, current methods for the estimation of crown cover are difficult to apply and are time‐consuming. The objective of this work was to present a much easier method of field estimation and to define the limitations of the method.The method uses the crown‐gap ratio (C), which is defined as the mean gap between crowns divided by the mean crown diameter. The relationship between values for the crown‐gap ratio and crown cover is of the form crown cover = k/(1 + C)2, where k is a constant.The overall tasks are first, to develop a methodology to obtain estimates of C and crown openness in the field, and second, to estimate k.In Part 1 we demonstrate that crown cover can be related to C when applied to woody vegetation. In Part 2 we consider a derivation of C, determine a value for k given a set of constraints, and outline some of the sampling implications of applying the method of crown cover estimation using C and k to field situations.The field study provided data from which to plot crown cover against the crown‐gap ratio (C). The shape of the curve approximated a rectangular hyperbola. The regression of crown cover against 1/(1 + C)2 showed a strong linear relationship (R2= 0.995) and gave an estimate for k of 0.79 for the range of plant communities sampled.The field study suggests that to investigate the effect of different spatial distributions of crowns and mixtures of crown sizes on C, a rigorous derivation of the relationship between crown cover and C is required.
Species‐richness and soil phosphorus in plant communities in coastal New South Wales
Authors: ADAM P. , STRICKER P. , ANDERSON D. J. 
Published: July 2006

AbstractSpecies‐richness (recorded as number of species in 16 m2 quadrats), in more than 60 coastal sites developed over various substrata, exhibited a significant non‐linear relationship with soil total phosphorus extracted from associated soil samples. Although the general form of this relationship is not incompatible with a resource competition model, the significant proportion of the total variance accounted for by the species‐richness/phosphorus relationship suggests that a more detailed examination of phosphorus use at a community level will be profitable.
Mulga log mounds: Fertile patches in the semi‐arid woodlands of eastern Australia
Authors: TONGWAY D. J. , LUDWIG J. A. , WHITFORD W. G. 
Published: July 2006

AbstractIn the semi‐arid woodland of eastern Australia, soil mounds are often associated with fallen mulga (Acacia aneura) trees. Measurements of the physical and chemical properties of the soils in these mounds compared with surrounding soils, together with differences in herbage growth responses, indicate that these mounds are fertile patches, with possible importance as habitats for soil fauna and as refugia for a range of organisms during drought. The mound soil material may accumulate by fluvial, aeolian or rain‐splash deposition about the fallen log, however, some of the mound material was derived from termite feeding gallery structures. The surface feeding gallery material may be comprised of soil particles from within the mound or from tunnels and storage galleries below the mound, and probably depends on the termite species.
Co‐existence of three species of amphibious plants in relation to spatial and temporal variation: Field evidence
Authors: YEN S. , MYERSCOUGH P. J. 
Published: July 2006

AbstractChanges in vegetation of Bushells Lagoon, a freshwater body fed intermittently by the Hawkesbury River in the Sydney basin, were studied over three scales of time: broad fluctuations in areas occupied by emergent plants over 28 years; fluctuations in their percentage cover over 21 months; and, over 6 months, seasonal variation in biomass of emergent plants of two native species Ludwigia peploides (Kunth) Raven ssp. montevidensis (Spreng.) Raven and Marsilea mutica Mett., and the introduced Myriophyllum aquaticum (Vellozo) Verde. Differences in distribution and abundance of plants observed between the three species were related to environmental variation in time and space. Wind and wave action varied along the shoreline, and emergent shoots of Myriophyllum were most abundant in sheltered conditions, floating leaves of Marsilea most abundant in relatively exposed conditions and emergent shoots of Ludwigia most abundant in somewhat intermediate conditions in the shallows. Chemical characteristics of the water varied in time but, unlike water temperature, had no obvious seasonal pattern. Seasonal change occurred in the biomass of Marsilea, and to a lesser extent in that of Myriophyllum, with smaller proportions of leaf material present in winter than in summer. Though water levels were apparently stable over a period of some years (1965–74), at other times they varied greatly through flooding and drought with related major change in cover of the three species. Co‐existence of the three species in the lagoon may be related to differences between their plants in establishment and growth following disturbance (regeneration niche), tolerance of wind and wave action (habitat niche), or seasonal growth (phenological niche).
Colonization, growth, and survival strategies of lichens on leaves in a subtropical rainforest
Authors: ROGERS R. W. 
Published: July 2006

AbstractRainforest leaves are a relatively short‐lived habitat which is well defined in both time and space, and which is occupied by a range of specialized lichens which might be expected to show survival strategies contrasting with those of other lichens. Changes in the lichen populations of individual leaves in subtropical rainforest at Ml Glorious, Queensland, Australia were observed for 1662 days. Over 1100 days elapsed before 50% of surviving leaves showed visible lichen thalli and the probability of colonization estimated from life tables did not exceed 0.42 ± 0.20 at any time. Porina epiphylla had a relative growth rate of 3.01 × 10−2 mm2 mm−2 week−1, a high value for a lichen. The relative growth rate of Strigula subtilissima, however, was 6.86 × 10−2 mm2 mm−2 week−1, the highest rate known for any lichen. Small size and high relative growth rates indicate that lichens on leaves have the most extreme ruderal strategy yet demonstrated amongst the lichens.
Habitat of the white‐footed dunnart Sminthopsis leucopus (Gray) (Dasyuridae: Marsupialia) in a logged, burnt forest near Bega, New South Wales
Authors: LUNNEY DANIEL , O'CONNELL MICHAEL , SANDERS JONATHAN , FORBES STEPHEN 
Published: July 2006

AbstractIn the winter of 1981, 9 months after an intense fire in November 1980 in the recently logged Mumbulla State Forest, the numbers of a small population of Sminthopsis leucopus had slightly increased, while the common species of small mammals had declined sharply from the previous winter. The study reported in this paper aimed to identify the habitat of S. leucopus. Ninety study plots were divided equally among three classes of forest (unlogged forest, and forest logged in 1979 and 1980), between two aspects (north‐ and south‐facing slopes), and among three topographic positions (ridge, midslope and gully). Plots were assessed on the basis of both floristic data and the structural components of ground, shrub and tree cover. The primary finding was that the habitat of S. leucopus was the treeless ridges and mid‐slopes with less than 51% ground cover in the logged areas of burnt forest. The floristic analysis showed that the vegetation subcommunities restricted to gullies, or carrying a ferny ground layer of vegetation, were not selected by S. leucopus. An analysis of movements of male S. leucopus identified two classes. ‘Resident’ males occurred on logged ridges and midslopes characterized by a floristic subcommunity of open forest with a grassy understorey.‘Explorer’ males moved through a variety of ridge habitats, including unlogged forest, and were spread more widely through the floristic communities. The pattern of habitat selection identified in this study shows S. leucopus to be ecologically distinct from the other species of small mammals in the forest and thus in need of special consideration in management programmes if it is to be conserved. Under the current regime, the uniform treatment of the forest leads to widespread stands of dense regrowth to the exclusion of the species and is inimical to its survival.
Demographic responses of Antechinus stuartii (Marsupialia) to supplementary food
Authors: DICKMAN C. R. 
Published: July 2006

AbstractThis study investigates the effects of supplementary feeding on populations of Antechinus stuartii, an insectivorous, semi‐arboreal species of dasyurid marsupial. Animals were live‐trapped, marked and released in three study areas in forest near Canberra, from September 1980 to November 1981. Supplementary food was supplied above ground in trees in one study area from January to November 1981, and in the second study area from January to May 1981, while the third study area was left unmanipulated as a control. The supplemented populations increased in numbers, mean body weights and survival, and showed decreased movements between traps and smaller overlaps in home ranges. Discontinuation of food in the second study area in May 1981 produced reciprocal shifts in these parameters. Reproduction, home‐range area, mean head‐body length, use of the terrestrial and arboreal parts of the habitat were largely unaffected by provision of supplementary food. In contrast to rodents, where fed populations usually increase rapidly due to immigration or increased reproduction, the supplemented populations of A. stuartii responded relatively slowly via increased survival of young. Population responses were probably retarded at the beginning of the experiments in summer due to the abundance of natural invertebrate prey, but became more obvious in winter when natural food was scarce. The added food probably contributed directly to increased numbers, survival and body weights, but may also have enhanced these parameters indirectly by allowing foraging animals to space out and avoid intraspecific intolerant contacts. These responses in A. stuartii suggest strongly that populations are limited by the food supply.