摘要:

AbstractDuring a field experiment to test effects of changes to leaf height and density ofZostera capricornion associated fish and decapods, more than one‐third of the substratum at some sites was covered by the epiphytic brown algaGiffordia 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 ofGiffordiawere 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 hig

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1987.tb00954.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractTabletop Mountain in the Northern Territory is a sandstone plateau topped in part by a residual laterite soil. The vegetation of the plateau was mapped and transects placed to cover the mapping units in which eucalypts were dominant or shared dominance. A polythetic divisive classification of the transect floristic data was largely congruent with the mapping units, which also differentiated the dominants. Topography and soils have an apparently strong influence on the nature of the vegetation through their influence on the periodicity and intensity of drought and Waterlogging. However, differences in soil fertility and understorey flammability are postulated to be important in discriminating several of the mapped vegetation types. The flora of Tabletop more closely resembles that of the Alligator Rivers region than that of the Mitchell Plateau or Weipa. Some of the communities differentiated at Tabletop are related floristically to some of the communities differentiated in the Alligator Rivers region and at Gove.

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1987.tb00955.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractTwo 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 discusse

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1987.tb00956.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractThe effect of fire frequency on the relative abundance of obligate‐seeders and vegetative‐regenerators was studied in 15 pairs of sites on the West Head, NSW. Each site pair consisted of a site which had been burnt frequently over the past 20 years and a nearby site which had been burnt less frequently. The data were collected in two phases. First, the relative abundance of the two overall groups of vegetative‐regenerators and obligate‐seeders was recorded by measuring the projective cover of live foliage. The presence or absence of particular species was then measured. For all the site pairs the projective cover of live foliage of obligate‐seeders was dramatically less in the frequently burnt sites. Some obligate‐seeder shrub species were absent from frequently burnt sites and the vegetation structure was simplified. In 11 of the 15 site pairs there was an increase in the projective cover of live foliage of vegetative‐regenerators in the frequently burnt sites, while in the remaining four site pairs there were no significant differences between the infrequently and frequently burnt sites. Overall, the increases in the relative abundance of vegetative‐regenerators made by high fire frequencies were not as large as the decreases in the relative abundance of o

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1987.tb00957.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractProteaceae are most diverse in southern Africa and Australia, especially in the south‐western portions of these regions. Most genera have some species in flower at all times of the year, although generally there is a preponderance of species that flower between late winter and early summer. The one genus that is an exception to this generalization isBanksia,which either has approximately the same percentage of species in flower at various times of the year (southwestern Australia) or peaks in autumn (southeastern Australia). Within particular communities, opportunities for hybridization among congeneric species are minimized by staggered flowering times, different pollen vectors and/or various incompatibility mechanisms. Birds, mammals and arthropods have been identified as visitors to the inflorescences of many Proteaceae. The most common avian visitors to the majority of genera in Australia are honeyeaters, although lorikeets, silvereyes and approximately 40 other species sometimes may be important. Sugarbirds and sunbirds are seen most frequently at inflorescences ofProtea, LeucospermumandMimetesin southern Africa, although they rarely visit other genera. In most cases, avian visitors forage in a manner that permits the acquisition and transfer of pollen. Limited evidence supports the hypothesis that birds are selective in their choice of inflorescences, responding to morphological and/or colour changes and usually visiting those inflorescences that offer the greatest nectar rewards. Arthropods may be equally selective, although it is possible that only the larger moths, bees and beetles are important pollinators, even for those plant species that rely entirely on arthropods for pollen transfer. Mammals are pollen vectors for some Proteaceae, especially those that have geoflorous and/or cryptic inflorescences. In Australia, small marsupials may be the most important mammalian pollinators, although rodents fill this niche in at least some southern African habitats. All but two genera of Proteaceae are hermaphroditic and protandrous, the exceptions being the dioecious southern African generaAulaxandLeucadendron.For hermaphroditic species, the timing of visits by animals to inflorescences is such that they not only acquire pollen from freshly opened flowers but also brush against pollen presenters and stigmas of others that have lost self‐pollen and become receptive. Birds and insects (and probably mammals) generally forage in such a way as to facilitate both outcrossing and selfing. Some species are self‐compatible, although many require outcrossing if viable seed is to be formed. Regardless of which animals are the major pollen vectors, fruit set is low relative to the number of flowers available, especially in Australian habitats. Functional andromonoecy of the majority of flowers is advanced as the major cause of poor fruit set. The pollination biology and breeding systems of Australian and southern African Proteaceae resemble one another in many ways, partly because of their common ancestry, but also due to convergence. Divergence is less obvious, apart from the dichotomy between dioecious and hermaphroditic genera, and differences in the levels of seed set for Australian and African species. Future studies should concentrate on identifying the most important pollinators for various Proteaceae, the manner in which their visits are integrated with floral development and factors responsible for limiting frui

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1987.tb00958.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractThe development and decline of all the past major plagues ofChortoicetes terminiferain 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.

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1987.tb00959.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Reproductive biology and habitat use of the Maned DuckChenonetta jubata(Latham) R. T. KingsfordSome aspects of phytogeography and vegetation dynamics of islands of the Great Barrier Reef H. Heatwole

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1987.tb00960.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Book review in this articlestudies on Plant Demography. A Festschrift for John L. Harper Edited by J. WhiteEcology of Marine Parasites Klaus RohdeTidal Flat Ecology. An Experimental Approach to Species Interactions Karsten ReiseEcology and Natural History of Desert Lizards. Analyses of the Ecological Niche and Community Structure E. R. PiankaEcophysiology of Desert Reptiles S, D. BradshawNatural Selection and its Constraints Oliver MayoManagement of Australia's Rangelands G. N. Harrington, A. D. Wilson and M. D.Management of Large Mammals in African Conservation Areas. Proceedings of a symposium held in Pretoria, South Africa, 29–30 April 1982 Edited by R. Norman Owen‐Smith,

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1987.tb00961.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY