摘要:

AbstractCommunities ofSorghum intrans, a tropical annual grass of north‐west Australia, contain sparse patches several metres in diameter within otherwise dense swards. These patches are persistent for at least ca. 4 years, despite the fact that these species are annuals which lack a persistent seed‐bank.Three possible causes of the sparse patches were investigated at a site near Darwin: loss of viable seeds through granivory or death; high plant mortality; or poor fecundity. This was done by augmenting the seed‐banks ofS. intransin the sparse patches, and thinning stands of seedlings in the surrounding, naturally dense areas, and comparing the results of these perturbations with controls.Granivory did not appear to be a cause of the sparse patches. Furthermore, the seeds in the sparse patches did not become inviable over the dry season. Compared with the plants ofS. intransin the naturally high‐density areas, survival of the plants in the augmented patches was not reduced, but vigour and seed production were. Conversely, plants in the thinned stands had a higher survival rate and very much greater vigour and seed production than plants in either the undisturbed patches or the undisturbed surrounding areas. Biotic constraints to plant growth such as grazing and disease appeared to be unimportant.These sparse patches result from poor site potential forS. intranswhich limits its growth and reproductive

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1986.tb01393.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractSeed production and predispersal seed predation in the shrubAcacia suaveolenswere examined over 3 consecutive years in eight populations in south‐eastern Australia. Seed‐crop sizes varied both between and within populations of different ages. Seed production was maximal in the first one to four flowering seasons after establishment, and then declined with plant age. The size of the annual seed‐crop was also influenced by rainfall for that year.Predispersal seed predation varies between populations over fruiting seasons with the initial large seed‐crops resulting in predator satiation. Within one fruiting season, no significant variation in the extent of predispersal seed predation was found in any of three populations studied. There were two major forms of predispersal seed loss: toss of whole fruits toMelanterius corosus(Coleoptera: Curculionidae) and external insect seed grazers, and loss of individual seeds within fruits toM. corosus.Exclusion experiments showed that seeds lost to these predispersal seed predators would otherwise have been matured by the parent plant. The effects of predispersal seed predation cannot be directly related to seedling recruitment. Indirectly, such predation may influence the dispersion of seeds in the soil profile and hence, subsequent recr

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1986.tb01394.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractGenet survival in seeds ofAcacia suaveolenswas examined through both dispersal and dormancy in the soil in populations near Sydney.Following initial passive seed‐fall, the majority of seeds lie within a 1 m radius of the stem of the parent. Further dispersal is predominately mediated by ants.A. suaveolensseeds possess an elaiosome which attracts ants. When elaiosomes are removed, the potential for further dispersal of seeds is greatly reduced. Three species of ant disperse seeds ofA. suaveolensand the fate of seeds following ant dispersal was observed to depend on the particular species of ant involved. Ants of bothIridomyrmexsp. andPheidolesp. B are too small to drag seeds and, instead, ants of these species usually remove the elaiosomein situ, with little dispersal of the‐seed resulting. Ants ofPheidolesp. A are larger and disperse seeds further, frequently taking them into their nests where the elaisosome is removed. Seeds are retained inside the nests and incorporated into the floors and walls of passageways and chambers. Several supposed ‘advantages’ of myrmecochory were examined but none were verified. Instead, two distinct ‘disadvantages’ were identified. These were: burial of seeds by ants ofPheidolesp. A into ‘unsafe sites’; and too deep a burial of seeds in nests for seeds to receive a stimulus to germinate during fires, and for seedlings to emerge successfully. Outside nests ofPheidolesp. A. seeds are concentrated in the top 5 cm of the soil, whilst within nests of these ants, seeds are found up to 15 cm deep.The dynamics of various components of the soil seed‐bank were examined using seeds buried in nylon mesh containers. The seed‐bank is persistent without annual recruitment to seedlings, enabling a population to persist as seeds after all above‐ground

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1986.tb01395.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractAll three species of specialized bark‐climbing birds in eucalypt forests of north‐eastern New South Wales exhibited sexual differences in their foraging behaviour. The degree of these differences was weakest in the least social species and strongest in the most social species, suggesting that intersexual niche segregation is an adaptation to reduce intraspecific competition for food. In the least social White‐throated Treecreeper, the slightly longer‐billed males foraged on dead branches more than females only during the breeding season when pair members were forced to share the same area. In the group‐living Red‐browed Treecreeper and Varied Sittella, males foraged lower and used rough‐barked trunks and limbs more than females throughout the year. Sexual differences in the foraging substrates of Sittellas may have been related to sexual dimorphism of the bill, but in the monomorphic Red‐browed Tree‐creeper, male dominance was probably important. Some evidence suggests that further subdivision of the niche may occur in the highly social Sittella along the vertical dimension according to age and/or reproductive status. This report argues that intersexual niche segregation is just as likely to develop under conditions of increased interspecific competition as under re

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1986.tb01396.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractThe distribution of eggs and larvae of Aedes vigilax was studied on part of a coastal salt‐marsh in south‐east Queensland. At the macro‐scale (8 ha area), the largest numbers of larvae hatched were from samples taken in areas with relatively low open vegetation adjacent to drainage channels. Such areas are likely to be suitable for egg conditioning and hatching and are also accessible to adult mosquitoes. At the micro‐scale (the environs of two small pools), most hatching occurred in narrow bands at specific elevations from the pool bottom but the relationship with vegetation was variable. Failure to hatch larvae from samples taken at the start of, or during, the cooler months was thought to be associated with egg diapause. At the macro‐scale whilst the marsh was flooded, most larvae were found in two habitat types: the tall denseSporobolus virginicusin relatively elevated locations and in depressions dominated bySarcocornia quinqueflora.At the meso‐scale (on a 1.4 ha grid) the distribution of larvae was found to be further related to water movement. Most larvae were in areas of slower water movement and appeared also to be redistribut

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1986.tb01397.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractMorphological and behavioural patterns were examined in a guild of nine species of eastern Australian cicadas. Co‐occurrence in, and structure of, 44 study plots were determined to relate morphological and behavioural patterns to habitat overlap and habitat structure. Multi‐variate analyses were employed to generate relationships between the species. Guild substructure shown by the habitat analyses cannot be predicted from the group substructure indicated by the morphology/behaviour analyses. Therefore, extant combinations appear to be random collections from the nine‐species pool insofar as morphology and behaviour are concerned. In particular, the most generalized species (in terms of habitat) are relatively extreme in morphology and behaviour, and vice versa. Despite these results, there are weak indications that at least two suites of characters exist, and that one of them is associated with each of the most extreme types of habitat. The reasons for these apparently contradictory results are discussed. There is no evidence to suggest that systematic morphological divergence has occurred in this

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1986.tb01398.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractThe long‐term movement of the abaloneHaliotis laevigatawas measured at three sites in Waterloo Bay, South Australia, characterized by differing amounts of available crevice space. Movement was negligible at a site where crevices were abundant, but extensive at a site without crevice space. At a site of limited available crevice space, the amount of movement increased as available crevice space decreased. In addition, the extent of movement was size dependent and movement was oriented in the direction of the approaching swell.Current experimental designs for measuring natural mortality of abalone depend heavily on assumptions about their movement. An understanding of this behaviour is thus a prerequisite for designing experiments to measure the mortality rates of abalone or other sedentary animals.The natural mortality rate at one site was estimated to be 0.59 (s.e.m. = 0.02, i.e. survival = 56% per year) and the disappearance rate (natural mortality and emigration) was independent of se

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1986.tb01399.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractThe effects of an intense fire on the nutrient status of jarrah(Eucalyptus marginata Donn ex Sm.) forest soils were investigated. At seven experimental sites, representing a range of soil and vegetation types, surface soils were sampled to a maximum depth of 20 cm before, immediately after, and 1 year after the fire.Immediately after the fire, concentrations of total and extracted nutrients in surface (0–3 cm) soils increased markedly. One year later, concentrations of extracted nutrients in surface soils had returned to levels close to pre‐burn concentrations. During this period, some properties of sub‐surface (3–20 cm) soils also changed: Bray‐extractable phosphorus and electrolytic conductivity decreased, whereas ex‐tractable potassium and pH increased relative to pre‐burn concentrations. Initial increases in concentrations of extractable forms of nutrients were determined largely by the amounts of nutrients deposited in fine ash, whereas the changes after 1 year depended more on the leaching of ions and their reactions with the mineral soil.Increases in total amounts of major nutrients in surface soils arising from additions of fine ash were generally well correlated with amounts in pre‐burn litter and with amounts in the components of organic matter likely to be consumed in the fire. Significant quantities of all nutrients are redistributed from aboveground sources to the soil surface during intense fires, including nutrients which are most susceptible to losses through volatilization. This redistribution of nutrients is discussed in relation to short‐term and long‐term effects on plant growth and functioning of t

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1986.tb01400.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1986.tb01401.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

Book Reviewed in this articleSeashore Ecology By T. Carefoot and R. D. SimpsonBiogeography. A Study of Plants in the Ecosphere By Joy TivyCanonical Analysis: A Review with Applications in Ecology‐Biomathematics. Volume 12 By R. GittensEcological Systems of the Geobiosphere. 1. Ecological Principles in Global Perspective By H. Walter and S‐W BreckleRiches of the Rain Forest By W. Veevers‐CarterCypress Swamps Edited by K. C. Ewel and H. T

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1986.tb01402.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY