摘要:

AbstractIf heterotroph grazers act as rate regulators of autotroph processes, the general intensity of grazing probably reflects the necessity for more or less intense rate‐regulation. The high rates of insect grazing in eucalypt forests imply that considerably more regulation of eucalypts is necessary than in other forests. After examining the biological adaptations of eucalypts and reviewing nutrient cycling in eucalypt forests, the hypothesis is proposed that the impoverished soils and erratic Australian climate have led to the development of very efficient autotrophic exploitation of the resource base, with associated sensitive and rapid growth responses to favourable conditions and a correspondingly sensitive and intense level of insect grazing. The rate‐regulatory activity of the insects ensures that the resource base is not depleted, and it maintains a proportion of the available nutrients in rapid circulation.In addition to the observed pattern of intense insect grazing in eucalypt forests, it is suggested that a two‐pathway nutrient cycling system has been developed, with pathways more clearly defined than the anastomosing nutrient‐cycling systems in forests elsewhere. A slow nutrient cycle is maintained by the trees while a smaller pool of nutrients is rapidly recycled in the litter and understorey. Insects skim off nutrients from the slow cycle and pass them into the faster cycling pool. This idea is important in relation to the frequency of fire in eucalypt forests and the large inputs into the system of nitrogen from the leguminous shrubs which regenerate aft

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1978.tb01165.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractNitraria billardierioccurs in all mainland states of Australia and on several adjacent islands south of the Tropic of Capricorn between Lat. 25° and 38°S and Long. 113° and 147°E. Other species of Nitraria are found in North Africa, the Middle East and Eurasia.The probability thatNitrariais a very old genus, having its origins in central Asia, is discussed. The wide disjunction betweenN. billardieriin Australia and the closely relatedN. schoberiin eastern Europe and Asia is difficult to explain.Observations on various populations grown under nursery conditions at Deniliquin, combined with those undertaken during field traverses across Australia, clearly indicate that considerable inter‐population variability occurs. Whether these different forms are ecotypes in which particular characters have become genetically fixed in specific habitats, is uncertain; but the form growing along the Indian Ocean coast of Western Australia shows marked contrasts to the other forms and may ultimately be described as a distinct species.Possible uses forN. billardieriin arid and semi‐arid zones of Australia are discussed. Particular reference is made to the abundance ofN. billardieriin low shrubland communities which were dominated by chenopods prior to the introduction of domestic livestock. The marked increase inN. billardierion overgrazed saltbush(Atriplex vesicaria)communities of the Riverine Plain suggests that it may serve as an indicator species in range condition assessment of these comm

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1978.tb01166.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractDetailed investigations were undertaken to determine the requirements for optimal germination and establishment ofNitraria billardieri.Germination ofN. billardierion the Riverine Plain is aided considerably by prior ingestion of the fruit by the emu(Dromaius novaehollandiae).Experiments suggested that the increase in germination of emu‐ingested seed is largely a response to the removal of the saline outer pericarp during digestion. In one experiment, 62% of emu‐ingested seed germinated after 24 days compared with 6% of the hand‐picked seed.Studies of field populations ofN. billardieriseedlings indicated that they are susceptible to competition from cool season annual species. A competition experiment in sand boxes between seedlings ofN. billardieriandAtriplex vesicariashowedN. billardierito have a slower growth rate and to be susceptible to competition by the seedlings of the perennialA. vesicaria.Studies of the root extension ofN. billardieriandAtriplex nummulariain root observation boxes demonstrated the poor performance by theNitrariaroots which grew only 53 cm in 7 weeks whereas theAtriplexroots grew 160 cm in 4 weeks. These data suggest thatN. billardieriestablishes and successfully competes in the field only with severely weakened saltbush stands. Other important factors are the availability of 'safe sites’ and the degree of competition from annual species.Glasshouse experiments using sand culture indicated that bothNitrariaandAtriplex vesicariacould survive in salinities of 0.9 M NaCl and both responded in terms of dry matter production to low salt inputs (e.g. 0.3M NaCl) although growth ofNitrariadecreased more rapidly as salinity in

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1978.tb01167.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractThe germination characteristics ofBanksia integrifoliaL.f., B. serrataL.f. andB. aemulaR.Br. were investigated. No significant response was found to light exposure, seed coat and substrate treatments. The three species showed marked and differing sensitivities to the temperature regime of germination.Germination character curves allowing the interpretation of temperature maxima, minima, the span between them, and optimal conditions for minimal incubation periods are presented. These were for B. integrifolia cool day temperatures<21°C but in excess of 14°C coupled with night temperatures between 5°C and 21°C; forB. serrataa narrow range of temperatures between 18°C and 24°C; forB. aemulawarm day temperatures 25–37°C coupled with night temperatures in the range 18–28°C.The geographical distribution of these species is related to germination requirements and some aspects of the seasonality of establishment environments ar

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1978.tb01168.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractRabbit burrows in three different habitats in an arid area showed characteristic variations and differences. Burrows in stony soil were generally cooler and more humid than burrows in sand and gravel soil. The temperature of the burrows in sand and gravel showed similar characteristics but the humidity in the gravel burrows was almost always significantly less than that of the sand burrows. Air and ground temperatures were significantly correlated but air and ground humidities showed a less significant correlation. Seasonal differences in microclimate within and between the three types of burrows were pronounced and are thought to cause differences in the survival of rabbits in arid areas.

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1978.tb01169.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractThis paper presents an analysis of the foraging ecologies and hence means of partitioning resources amongst the twenty‐eight most conspicuous species of birds in lowland tropical rainforest at Lacey's Creek, North Queensland. The height and site of foraging and the type of behaviour used by the species were compared. The height at which species foraged appeared to be more important for separating species than the site of foraging or the behaviour used. There appeared to be a greater proportion of species with generalized foraging behaviour at Lacey's Creek than in bird communities in the neotropics. Frugivorous species had very similar foraging ecologies but there were differences in the species of fruit eaten by some species. There were seasonal shifts in foraging by some species. It is postulated that the relative shortage of terrestrial species at Lacey's Creek compared with highland forest in North Queensland is due to the harsh dry season in the lowlands. The structure of this bird community appeared to be strongly affected by seasonality of climat

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1978.tb01170.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractA trapping study of four species of Rattus and three ofMelomysin rainforest and grassland habitats revealed differences in altitudinal distribution and in both gross and subtle habitat selection between species. The species are ranked on a scale of increasing opportunism on the basis of various demographic characteristics (e.g. reproductive rate, life span and population density). Species judged to be more opportunistic occur in habitats subject to more intense disturbance from pigs and humans. It is argued that changes in the pattern of species coexistence have followed overt human impact in the New Guinea highlands.

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1978.tb01171.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractProblems of display and interpretation often associated with ordination techniques are briefly discussed. Minimum spanning ordination (MSO) is put forward as offering a meaningful compromise between the limitations of two‐dimensional representation and three‐dimensional complexity. The method incorporates the use of a minimum spanning tree together with a graphic spherical perspective of points in the third dimension. It is suggested that where this approach is used with reduction analysis, i.e. with centroids of representative clusters, interpretation is much improved and inherent distortions likely to result from techniques such as principal component analysis are more readily expo

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1978.tb01172.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

A study of the litter and soil fauna of two Australian subtropical forests with particular reference to the Cryptostigmata and the Mesostigmata (Acarina) Kristine P. PlowmanFeeding and breeding biology of six sympatric species of tern (Laridae) at One Tree Island, Great Barrier Reef C. HulsmanThe environmental biology of the koala Robert Degabriele

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1978.tb01173.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY