摘要:

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 spec

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1989.tb01436.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractNectar‐feeding birds are prominent in many parts of the world, and vary with respect to body size. Despite the availability of considerable morphometric data, few concerted efforts have been made to assess the influence of attributes such as mass, wing length and leg morphology upon the speed, acceleration, mode and energetic cost of movement by birds between flowers when foraging for nectar. This review attempts to consolidate and interpret available data and highlight areas where further investigations appear warranted. Australian honeyeaters are generally larger, and American hummingbirds smaller, than Hawaiian honeycreepers and sunbirds of Africa or Asia. Sunbirds, honeyeaters and honeycreepers generally perch while extracting nectar from flowers. Hummingbirds usually hover, apparently because suitable perches close to flowers are lacking, and not because hovering increases the speed at which flowers can be visited. Honeyeaters move from one flower to another at speeds that are at least as great as those for hummingbirds. Most passerine nectarivores need to ingest more nectar per day than hummingbirds in order to maintain energy balance, some species devoting more than 60% of the day to foraging. The major consequence of reduced foraging activity by hummingbirds, which spend only 5–30% of the day in this manner, appears to be male emancipation from nest construction and care of offspring. Large nectarivores have a greater capacity to store surplus food and to fast than smaller birds, and so can take advantage of short‐lived peaks in nectar abundance. Nectarivores such as honeyeaters should therefore be favoured by the rapid diurnal changes in nectar availability which are characteristic of many Australian and African habitats. Body mass also determines the likely access to rich sources of nectar through size‐related interspecific dominance hierarchies. In all families, larger species tend to monopolize the most rewarding nectar supplies, forcing smaller subordinate species to use poorer, more scattered sources. Within particular species, males usually have longer wings and greater masses than females. These variations imply that the two sexes differ with regard to their foraging ecology, although few supporting data are currently av

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1989.tb01437.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

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 speciesLudwigia peploides(Kunth) Raven ssp.montevidensis(Spreng.) Raven andMarsilea muticaMett., 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 ofMyriophyllumwere most abundant in sheltered conditions, floating leaves ofMarsileamost abundant in relatively exposed conditions and emergent shoots ofLudwigiamost 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 ofMarsilea, and to a lesser extent in that ofMyriophyllum, 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 nic

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1989.tb01438.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractPlant responses inLudwigia peploides(Kunth) Raven ssp.montevidensis(Spreng.) Raven andMarsilea muticaMett., and the introducedMyriophyllum aquaticum(Vellozo) Verdc. were observed and related to co‐existence of the species in a freshwater lagoon in the Sydney basin.Water levels vary in the lagoon, and plants of all three species grow readily from stem fragments on freely draining, waterlogged and submerged soils. InMarsilea, sporelings develop rapidly from ruptured sporocarps when wet. In Ludwigia, the seeds germinate in white and in red light, but not in darkness or far‐red light. They germinate readily on soil and in water, floating or when held submerged. At 30°C, germination is rapid, at 40°C slower and less, and at 10°C nil, but seeds imbibed at 10°C and then exposed at 15°C have greater and more rapid germination than seeds maintained at 15°C.In relation to seasonal variation, plants of all three species grew at 10, 20, 30 and 40°C on freely draining, waterlogged and submerged soils, with the optimum temperature for growth apparently lower in Myriophyllum than in the other two species.In relation to water depth, plants of all three species grew when submerged to I m; the stems of Ludwigia andMyriophyllumelongating and reaching the water surface, and the petioles in Marsilea elongating bringing the leaf blades on to the surface, each within a week during summer. The floating leaf blades inMarsileaincrease in size with depth of submergence of the subtending shoots.Mean relative growth rates (R̄) under the most favourable experimental conditions were least in plants ofMarsilea, the species occurring along more exposed parts of the shoreline in the lagoon.It was concluded that, while water levels in the lagoon were stable, differences in growth form between the species were probably more critical in their co‐existence than quantitative differences in their growth: the floating leaves of Marsilea, being more resistant to wind and wave action than the floating shoots of Ludwigia and Myriophyllum, occupy the more exposed parts of the lagoon 'S edge. The most sheltered parts are occupied by the shoots of Myriophyllum which ride high on the water and overtop shoots ofLudwigia. Shoots ofLudwigiaappear to be more resistant than those ofMyriophyllumto removal and damage by wind and wave action, and achieve their greatest abundance on the water surface in situations of intermediate exposure to wind and wave action.Using Grubb's (1977) classification of niches, in Bushells Lagoon the three species appear to be primarily differentiated in habitat niche, less in regeneration niche and even less in phenological niche. In the lagoon, their habitat niches apparently overlap in water depth but are differentiated along a gradien

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1989.tb01439.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractDiet composition and prey intake rates of Australian magpies in a New Zealand population were investigated to determine whether flocking, non‐territorial birds were less successful predators of pasture invertebrates than territorial birds. Time‐activity budgets showed that flock magpies foraged throughout the day during February and March, indicative of a prey shortage at that time. Prey abundance was therefore measured in the autumn months but there was no evidence of a large quantitative difference in the food supply of flock and territorial magpies. Significantly fewer invertebrates were collected from pitfall traps in the flock foraging area, but these were counterbalanced by significantly more scarab beetle larvae and more flying insects, obtained by sweep‐netting. When compared with territorial magpies, flock birds exhibited similar peck rates, prey intake rates, and earthworm intake rates. While there were qualitative differences in the diets of flock and territorial magpies, determined by faecal analysis, five of seven prey items analysed were captured in the same relative proportions by the flock and territorial birds. Earthworms exceeded their relative availability in the diets of flock birds, and more scarab larvae were found in the diets of territorial magpies. Non‐territorial magpies were therefore no less successful than territorial birds during the autumn, and it is suggested that the function of flocking behaviour may eventually be discovered through consideration of why non‐territorial birds never occur as solitary individuals, rather than emphasizing comparisons with territoria

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1989.tb01440.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

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 × 10−2mm2mm−2week−1, a high value for a lichen. The relative growth rate of Strigula subtilissima, however, was 6.86 × 10−2mm2mm−2week−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 amo

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1989.tb01441.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

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 ofSminthopsisleucopus 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

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1989.tb01442.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractThis study examined the floristic variation at 20 sites of sclerophyllous shrubland (kwongan) occurring on lateritic soils in the central wheatbelt of south‐western Australia. The results show that this kwongan is as floristically rich and varied as the kwongan in the northern and southern sandplain areas of the south‐west. Six sequential groups of sites can be identified along the rainfall gradient present over the study area; 29 species are selected as indicators of the floristic groups. The distribution of many of the remaining 426 species suggests a continuum of floristic change along the rainfall gradient. One hundred and forty‐five species were only recorded once and thus contributed to the high species richness of the sites and the low level of floristic uniformity between the stands. There were significant trends in the proportions of lifeforms with respect to the rainfall gradient. Evidence of the response of the plants to an obvious environmental gradient and the increased understanding of this complex vegetation type will provide conservation managers with some rationale for setting priorities for reserve acquisition and manag

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1989.tb01443.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractPrevious studies have demonstrated a species replacement sequence in disturbed forest and heathland, with the native New Holland mouse (Pseudomys novaehollandiae) replacing the introduced house mouse (Mus musculus) in the earliest part of the succession. The replacement appeared to be competitive displacement and this has been confirmed by controlled experimental removal of P. novaehollandiae from field sites, which produced significant increases in the abundance and habitat use of Mus musculus. This paper reports the results of the controlled reciprocal manipulation experiment in the field. A pulsed addition of M. musculus to three treatment plots produced significant reductions in the abundance and habitat use of P. novaehollandiae, when compared with control plots with no addition of M. musculus. This effect was observed only at high M. musculus densities, and the return to the control conditions within 3 months of the pulsed addition is consistent with asymmetric interspecific competition from competitively superior P. novaehollandiae. The importance of considering the regional abundance of M. musculus in relation to its competitive ability is stressed, as at high densities M. musculus is able to create its own ecological space contrary to its more usual competitively submissive status.

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1989.tb01444.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractPlants which have seeds adapted for dispersal by ants (myrmecochores) are more common in some vegetation types than others. In Australia, myrmecochores are common in sclerophyll shrublands which are associated with infertile soils but not in forests on fertile soils. One hypothesis to explain this difference is that ants are less abundant or less active in seed removal on fertile soils. A test of this hypothesis was carried out on four sites in the Royal National Park, south of Sydney, by measuring the number of myrmecochorous seeds removed by ants in a 24 h period. It was found that the removal rates of seeds were slightly higher on fertile sites although this difference was not significant. The hypothesis that a lower removal rate on fertile soils could account for the lower percentage myrmecochory was therefore rejected. Apart from the gross removal rate of seeds by ants, other differences in ant behaviour might be important. It is possible that a greater proportion of ant species unfertile soils are seed predators or ineffective seed dispersers, and evidence obtained indicates that this is worthy of further research.

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1989.tb01445.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY