摘要:

AbstractAbundances of honeyeaters, flowers and flying insects, the daily nectar‐energy production per flower and the average size of flying insects were estimated every three weeks for circles of radius 20 m located in three heathland areas near Sydney. Seasonal fluctuations in honeyeater density showed no apparent relationship with seasonal fluctuations in nectar‐energy productivity or in biomass of flying insects. Variation between circles in honeyeater density was also unrelated to spatial variation in energy productivity and insect biomass. The relatively low incidence of nectar‐feeding and high incidence of flying exhibited by birds observed during troughs in nectar‐energy production suggest that many of these birds are transient and that their density may consequently be unrelated to local con

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1983.tb01320.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractBirds are important granivores in the Australian arid zone, and this paper reviews their role by assembling available data on diet and habitat selection of the granivorous species occurring in the region. Paucity of dietary information is alleviated by a study of the food of the zebra finch(Poephila guttata)at two sites in the eastern arid zone. Zebra finches subsisted entirely on grass seeds of a relatively narrow specific range; 17 classes of seeds (at least 19 species) were eaten, but one class dominated the diet at each study site and only five classes (probably six species) were significant overall. Comparative information concerning granivorous species‐ suggested that the seeds of grasses and shrubs are of most importance in diets, that larger species tended to eat larger seeds from a wider variety of plants because of the addition of shrub species to the diet, and that Acacia shrublands contained most species. Characteristics of the arid zone that are of particular importance to granivorous birds appear to be the abundance of grasses and the patchy and erratic nature of the rainfal

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1983.tb01321.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractInvertebrate components of natural pastures which were grazed continuously by sheep at three stocking intensities, were sampled each season for more than two years. Grazing resulted in a significant reduction in abundance of litter and topsoil micro‐arthropods. Two samplings for nematodes and enchytraeids showed similar reductions with grazing. Grazing effects on the vertical distribution of mesofauna were not consistent but all sites had greatest numbers in the 0 – 5 cm topmost soil layer. Fresh biomass of large soil and litter dwelling invertebrates also declined with grazing, with proportionally greater reductions occurring for litter animals. Changes in invertebrate populations were associated with changes in living space, microclimate and food supply. Populations of invertebrates on natural pastures were about one‐third those found on previously studied sown, fertilized pastures at Arm

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1983.tb01322.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractThe effects of artificially reduced amounts of larval food on various life history parameters ofLucilia cuprina, Calliphora stygia, C. vicina, andC. hilliwere measured to assess the likely reaction of these blowflies to competition in carrion. With increasing food shortage the puparia were reduced by up to 12% of the weight attained under conditions in which food was unlimited. The size of eggs laid by adults which had been subject to food deprivation as larvae was unchanged, but all species showed a reduction in the number of ovarioles. An index of mass‐specific reproductive investment varied considerably between the species, and the relationships between this index and the preferred habitats and dispersal strategies of the species are discusse

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1983.tb01323.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractIndigenousSorghumspecies are a prominent feature of the seasonally‐dry tropics of north‐west Australia. Studies of the dormancy characteristics of these species were undertaken, and measurements of seedling emergence, of plant survival, growth and reproductive success, and of seed bank changes were made for oneSorghum intranspopulation and for threeS. stipoideumpopulations over two growing seasons.On wetting, 90% of the non‐dormant, viable seeds of nil species germinated within five days. The temperature range for optimal germination was 25 ‐ 35°C, and germination declined with decreasing water potential. The seeds of all species had high innate dormancy at seedfall, and this was broken down over the ensuing dry season.ForS. intrans and S. stipoideumheight and tiller number increased steadily after emergence up to the time of floral initiation, which occurred simultaneously for primary tillers within each population. Most vegetative tillers died after this leaving a single reproductive culm which rapidly elongated to reach 1 – 4 mat maturity, depending on site and season.Seedfall occurred over a short, c. two‐week period before the rainy season had finished. Seeds were dispersed within 2 m of the parent plant. Seeds were buried to less than 2 cm by the screwing action of their hygroscopically‐active awns.All these annual Sorghum species appear to have transient seedbanks, formed at seedfall near the end of one rainy season and exhausted by germination following the first rains of the next annual rainy season. We suggest thatS. intrans and S. stipoideumpersist despite this feature because they mature at the earliest time that the rainy season has been known to end in their respective localities. Persistence is further aided by adaptations which enable individuals to survive the unpredictable short droughts which occur while they are emerging and growing.S. intrans and S. stipoideumhave low fecundity (mean ≃ 8 viable seeds per individual) and high survivorship. They fit Watkinson's (1981) schema relating fecundity to survival for annuals with tran

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1983.tb01324.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractRates of weight loss and release of N, P, K, S, Ca, Mg, Na, and Cl from litter of several species in jarrah (E. marginataDonn ex Sm.) forest were measured in relation to site fire history and soil type. Weight loss from leaf litter decreased in the order jarrah>marri (E. calophyllaR. Br. ex Lindl.)>Banksia grandisWilld. After 18 months on the forest floor senesced leaves of jarrah, marri andBanksiahad lost 45%, 42% and 19%, respectively, of their original weight. Although greatest rates of decomposition occurred on a site burnt 3 y previously by an intense autumn fire and slowest rates on a site which had not been burnt for 8 y, the differences between burn sites were small in comparison with the total weight loss from decomposing litter. The order of release of nutrients from decomposing eucalypt litter was P

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1983.tb01325.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractThe rate of decomposition of summer leaf‐fall (abscised leaves), winter leaf‐fall (containing some green leaves) and mature green (picked) leaves was assessed in sub‐alpine forests ofE. delegatensis(R. T. Baker),E. pauciflora(Sieb. ex Spreng) and E. dives (Schau.) in the Brindabella Range, Australian Capital Territory, using litter bag and tethered leaf techniques. The relative contribution of leaching, microbial respiration and grazing by invertebrate macrofauna to loss of leaf weight was determined. The effect of leaching and microbial respiration was assessed in terms of weight loss per unit area of leaf (specific leaf weight), while losses due to macro‐faunal grazing were assessed by measuring reductions in leaf area. Litter decomposition constants for litter components (leaf, bark, wood) and total litter were determined from long‐term records of litterfall and accumulated litter.Weight losses of abscised leaves during the initial 12 months ranged from 25% forE. pauciflorato 39% forE. delegatensisand were almost entirely due to reduction in specific leaf weight. Losses in the weight of leaves falling in winter ranged from 38 to 49%, while green leaves lost 45 ‐ 59%. Approximately 50% of the total weight loss of green leaves was due to a loss in leaf area caused by skeletonization by litter macrofauna. Thus abscised leaves rather than green leaves must be used for measuring litter decomposition rates since abscised leaves constitute most of the litterfall in eucalypt forests.Leaves placed in the field in autumn decomposed slowly during the first summer, while the rate increased during the second winter and summer. Low litter moisture content appears to limit decomposition in the initial summer period in all communities, after which litterfall provides a mulch which reduces the rate of desiccation of lower litter layers. A simple linear regression model relating decomposition rate to the number of days (D) when litter moisture content exceeded 60% ODW accounted for 63‐83% of the variation in decomposition of leaves in the field. Inclusion of mean monthly air temperature (T) and the product ofDandT(day degrees when litter was wet) in a multiple linear regression increased the variation in decomposition accounted for to 80 – 90%.The rate of weight loss showed a positive linear relationship with the initial concentration of nitrogen (N) or phosphorus (P) in the leaf. These concentrations are an index of the decomposability of leaf substrates (e.g. degree of sclerophylly or lignification).The rate of loss of specific weight was similar for tethered leaves and for leaves enclosed in mesh bags. Measured loss in specific leaf weight after 70 – 90 weeks was less than that predicted using decomposit

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1983.tb01326.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractThe presence of residues of iceplant(Mesembryanthemum crystallinum)was found to significantly decrease the production of a volunteer annual pasture in subsequent years. Iceplant gathers salt from throughout the root zone of even a slightly saline soil and accumulates it in the aerial parts of the plant. Following senescence, rain leaches the salt onto the soil surface, which becomes so saline as to inhibit the growth of most competing species, and of iceplant itself. It is suggested that as the salt is leached from the top soil, iceplant can dominate by being able to establish at higher levels of soil salinity than potential competitors. The accumulation of salt in iceplant is not primarily a halophytic mechanism but a competitive strategy, allowing it to be a facultative halophyte.

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1983.tb01327.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractBushland sites in the northern suburbs of Sydney were compared to sites in Brisbane Waters National Park, Ku‐ring‐gai Chase National Park and Royal National Park which are relatively unaffected by suburban development. Both shale‐derived and sandstone‐derived soil in four physiographical locations were examined, with three replicates of each of the 16 combinations.Phosphorus levels are higher in the soils of suburban sites compared to soils derived from similar rock bases in non‐suburban sites. Phosphorus levels are also higher on shale‐derived than on sandstone‐derived soils, and lower on hilltops than in other physiographic positions. Suburban sandstone sites have soil phosphorus levels similar to those of non‐suburban shale sites.Three major and three minor clusters of species were distinguished using a hierarchical agglomerative clustering. The major clusters consisted of (1) species commonly associated with wet sclerophyll forests and rainforest margins, (2) species directly or indirectly related to the presence of man, and (3) species associated with dry sclerophyll forests and heaths.Using analyses of variance and covariance, and logit models, the abundance of the first main cluster was related to nutrient‐rich soils and the abundance of the third main cluster to low nutrient soils whereas the presence of the second main cluster was almost entirely restricted to sites surrounded by suburbs.The development of suburbs around vegetation patches has led to an increase in the abundance of native and exotic mesomorphic species and the addition of phosphorus to the soils. The data presented in this paper indicates that high phosphorus levels and presence of mesomorphic sp

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1983.tb01328.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractAn exploratory study was made of the tree species, landform, soils and erosional sequence along altitudinal transects from interfluve to stream channel in a valley incised into Narrabeen Group sandstones and shales to the west of Putty, NSW.Four groups of soils with similar edaphic features were identified. These ranged from duplex soils on the apparently old and stable valley rim, through eroded earths on zones of depletion and sandy regoliths with thick surface horizons on zones of accumulation, to mature duplex soils with thick surface horizons on the colluvial toeslopes.Four communities of tree species were found associated with the four groups of soils. A Eucalyptus punctata –E. piperitaopen‐forest was found on the stable valley rim and a related Eucalyptus punctata –E. piperita – E. oblongaopen‐forest to low woodland was found on zones of depletion. An Angophora costata open‐forest was found associated with the sandy regoliths on zones of accumulation and aEucalyptus viminalis – E. tereticornisopen‐forest to tall open‐forest occurred on thick soils of the colluvial waning slopes.It was found that the landform fitted a hypothetical nine unit land surface model. The soil types and plant communities were found to reflect the dominant contemporary pedogenetic and geomorphic processes which are also used to define the units of this model. Erosion was evident in the catchment, and the sequence of alluvial soils on the valley floor was found to be consistent with previous suggestions of widespread slope instability during the Quaternary period. Speculation is offered about the effects of management of the valley, especially in terms of land su

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1983.tb01329.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY