摘要:

AbstractThe distribution of freshwater fish in creeks throughout the Brisbane region was determined by a survey carried out in 1977–78. Seventeen native and six exotic species were recorded in 55 creeks. Sixteen native and four exotic species were collected in a more restricted survey of central Brisbane in 1981. Urban development and the establishment of exotic plants have resulted in substantial changes to the aquatic environment in many of the creeks surveyed. Exotic grasses, especially para grass (Brachiaria mutica) have reduced the extent of free water by growing partly into stream channels. Floating exotic plants blanketed some stream reaches. Native aquatic macrophytes have declined, apparently due to dredging, siltation and other disturbances. These changes have affected the distribution and abundance of native and exotic fish. Native species with a preference for open water and beds of aquatic plants have declined in creeks overgrown by para grass and floating plants. Melanotaenia fluviatilis, Retropinna semoni, Pseudomugil signifer, Craterocephalus stercusmuscarum and Ambassis nigripinnis have been affected. Para grass and floating plants have not affected the range or abundance of Hypseleotris galii, H. compressus and Mogurnda adspersa. Gambusia affinis and Xiphophorus helleri have been advantaged by expansion of their preferred habitat type ‐ the edges of pools where exotic grasses have grown partly into the water. The effect of exotic fish on native species is unclear. There was a correlation between large numbers of G. affinis and small numbers of H. galii and M. fluviatilis. Correlations could result from predatory or competitive interactions between species. Alternatively, correlations could be due entirely to the effects of habitat alterations on exotic and native species. However, H. galii was evidently not disadvantaged by the habitat alterations studied. Thus there may be a complex interaction between this species and G. affinis. There was no evidence that X. helleri had affected the range or abundance of native spec

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1983.tb01597.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractIn general, the brown honeyeater, Lichmera indistincta, flies more and expends more energy when visiting flowers in the early morning than at other times. Floral nectar is most abundant early in the day, and nectar energy intake by L. indistincta is greatest at that time. It appears as if birds can only store excess energy during the early part of the day, incurring energy deficits at other times. Unit perching and flight costs are greatest for L. indistincta in winter and spring. As a result, peak total energy expenditures and requirements occur at these times, birds apparently being unable to reduce energy demands by employing nocturnal torpor. Estimates of probable energy uptake by L. indistincta from the plant species studied exceed predicted requirements in all seasons except winter, when it is apparent that birds would need to be especially selective in the plants that they used as major energy sources.

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1983.tb01598.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractA quantitative study of the soil and litter fauna of three South Australian low open forests was made for two years. The soil and vegetation of the sites were similar but the mean annual rainfall of the areas differed; 635, 690 and 1050 mm/y, respectively for the ‘dry’, ‘medium’ and ‘wet’ sites. Monthly samples were taken of litter, and the upper 0–4 cm and lower 4–8 cm soil layers, and the method used to estimate the numbers of active animals is also described.Mean annual population densities of Collembola and Acari were greatest at the medium site (9.5 and 48.6 × 103/m2, respectively) and least at the dry site (4.9 and 35.1 × 103/m2, respectively) and values are discussed in relation to site organic carbon content. Over all the sites, between 11–21, 67–75 and 10–15% of the collembolan populations, and 10–13, 66–72 and 16–21% of the acarine populations inhabited the litter layer and upper and lower soil layers respectively. Isotomidae were the most abundant collembolan family in each level at each site, but the overall proportion of Entomobryidae increased from the dry to wet site. Prostigmata were the most abundant acarine order in each level at two sites. Cryptostigmata were dominant in the litter layer of the wet site, and their overall proportion increased from the dry to wet site. Seasonal density changes were similar on all sites with minima in the summer and maxima in the winter months.The results obtained here combined with those from other published investigations indicate a trend of faunal population change over various ecosystems in Australia. Prostigmatid mites and iso‐tomid Collembola dominate at arid sites. As sites become less arid and the amount of soil organic matter increases, the proportion of cryptostigmatid and mesostigmatid mites increases, and other groups of Collembola, particularly Ento

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1983.tb01599.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractThe ant communities of two adjacent sites bearing markedly different vegetation (heath and mallee) were studied using quadrat counts and pitfall traps in semi‐arid northwestern Victoria. The ants were extremely abundant and rich in species (86 species from 27 genera were recorded from two 50 m × 25 m plots within 25 m of each other) and were dominated by species ofMonomorium and Iridomyrmex. Pronounced site differences in species composition were found, with 73% of the most abundant species showing a strong site preference. The ants exhibited marked seasonality: activity was highest in summer and lowest in winter and this was accompanied by a high turnover of species in time, resulting in pronounced seasonal differences in species composition. Most foraging was nocturnal during summer but was almost exclusively diurnal during winter, and individual species displayed distinctive patterns of diet foraging activity. Although the overall temporal distribution of the communities were apparently controlled by temperature, interspecific competition may also be an important factor influencing the seasonal and diel distributions of individual species, resulting in their high degree of temporal separation. The overall consequence is that although the study area contains many abundant species with similar ecological requirements, few of these are active in the same place at the same ti

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1983.tb01600.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractHigh levels of insect damage on Eucalyptus have been noted but not quantified in previous literature. We present estimates of leaf damage for 44 Eucalyptus species from a variety of habitats. Overall, an average of 15% of expanded leaf area was missing. While some species were generally lightly grazed, others, especially those in more mesic. higher altitude communities, usually sustained much heavier leaf damage. In the age and size classes, communities and years that we sampled, the overall levels of damage to eucalypts were higher than chronic damage levels reported for north temperate communities. We also suggest a simple method for rapidly estimating the proportion of leaf area missing from trees.

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1983.tb01601.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractThe regeneration of rainforest onto land cleared for grazing early this century was studied on several sites in northern Tasmania. Drimys lanceolata, a bird‐dispersed species, was the main invader. The climax forest species. Nothofagus cunninghamii and Atherosperma moschatum were invading slowly from the forest edge with occasional trees established in the field. Woody plants in the old‐field were clumped around logs. This was related to the role of logs in attracting seed and to possible roles as competition‐free sites and sites safe from browsing and climatic stresses. Changes in dominance by particular life forms appeared to be related to dispersal events, environmental modification by the developing vegetation and life history characteristics. The extremely slow invasion by climax species is due to the absence of bare mineral soil as well as to dispersal characteristics, browsing and possibly exposure to climatic str

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1983.tb01602.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractWe present data on vascular plant species richness, at the 0.1 ha scale and below, of sclerophyll vegetation on infertile sandstone, and some neighbouring types, in a non‐mediterranean climate area of temperate, east coast Australia The vegetation of sandstone is richer in species than is that of a permanently wet swamp (18/0.1 ha) or of more fertile soils (36, s.d.‐ 2). On sandstone, woodlands on moderate benched slopes (77, s.d. = 9) are richer in species than are the scrubs found on skeletal (56, s.d.= 7) or impeded drainage (48, s.d.= 8) soils, and this difference appears in the species‐area curve from 100 m2up. Species richness of the sandstone vegetation, like its growth‐form mix, is very similar to species richness of South African fynbos and southwestern Australian heath. which supports the idea that the community properties of this sort of vegetation are not determined by climate but are determined by soils. The strong contrast in species richness, noted by Naveh&Whittaker (1979), between the mediterranean‐climate vegetation of South Africa and southwestern Australia on the one hand, and California and Israel on the other, need not be attributed to different evolutionary histories of the floras. The present environment, in the form of the soil factor, could well be the main de

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1983.tb01603.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractFour problems associated with studying the altitudinal distribution of eucalypt species are examined: the lack of specific physiological relationship between altitude and plant growth, the influence of other environmental factors, the availability of suitable data and the need for statistical analysis. Presence/absence data for eucalypt species were obtained from several sources. Probability of occurrence in 100 m zones is determined for E. maculata, E. muellerana, E. fastigata, E. sieberi, E. dalrympleana and E. pauciflora. The influence of other factors is demonstrated for several species using direct gradient analysis. Aspect is important for E. fastigata and E. rossii in addition to altitude and rainfall.The statisical model used was the logit‐linear model: log (p/I– p) = linear function of environmental variables where p is the expected probability of being present for a given combination of environmental variables. Two examples are presented. E. dalrympleana can be predicted from altitude, rainfall, radiation index (measure of aspect) and an interaction term between altitude and aspect. E. rossii presence is predicted by altitude, rainfall, radiation index and geology. Altitude is transformed into an estimate of mean annual temperature which is shown to clarify some overlaps of species distribution.It is concluded that use of data collected for other purposes can be used in a generalized linear model for presence data to show the complex correlations which exist between the altitudinal distribution of some eucalypts and other environmental fact

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1983.tb01604.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractA method was required for determining the effect of management on extensive populations of trees and shrubs in central Australian rangelands. One useful indicator of change in these populations is the density of individuals, and there are several methods available based on distance measurement for density estimation. This study compared those procedures.Samples were drawn by computer from ground maps of actual plant distributions for Acacia aneura, Cassia nemophila and Atalaya hemiglauca and from a map generated at random. These samples were drawn to examine the properties of the nearest neighbour, point centred quarter, conditioned distance and compound T‐square estimates of density. Samples were drawn by two methods: simple random sampling and semisystematic sampling.In general, there was a tendency for all estimators of density to underestimate the true density of naturally occurring populations with the compound T‐square method (Byth 1982) being most robust. The compound T‐square method was least biased but its variance increased for more aggregated spatial distributions. Estimates of density were not altered by the use of semisystematic sampling, when compared to simple random sampling.The spatial distributions examined in this study have not previously been studied as theoretical models. Acacia aneura and Cassia nemophila showed some aggregation of clusters, while the Atalaya hemiglauca showed a more extreme form of clustering due to its root suckering propag

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1983.tb01605.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractA basic problem in experimental design is to select a sample unit at a scale appropriate to the variables being observed and to the nature of the topic. Where hierarchical classification procedures are used it is important that the scale of the basic units is such that any variation found within the sample is small relative to that between the groups formed. In this paper a method is applied to evaluate the relative homogeneity of sample units. Replicates from each sample are classified hierarchically. The method of Sandland&Young (1979a, b) is used to determine the probability at division of the number of replicates assigned at a division to the same group occurring by chance. A high probability indicates relative heterogeneity of the samples from which replicates are drawn; a low probability suggests relative homogeneity. An example from the area of urban ecology illustrates an application of the method. It is used to evaluate the relative homogeneity of spatial units (Census Collectors Districts) with respect to dwelling characteristics in inner city Brisbane. Possible applications in other areas of ecology are briefly considered.

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1983.tb01606.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY