摘要:

AbstractDespite a consistent seasonal pattern of daily production of nectar‐energy per unit area with peak production around the end of May, the seasonal pattern of honeyeater abundance is not consistent between years and does not correspond to the pattern of nectar‐energy product

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1988.tb01413.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractSheoaks and saltwater ti‐trees regenerate poorly within the Coorong National Park unless they are protected from grazing mammals. The age structure of these tree populations suggests that both species regenerated vigorously in the 1950s when myxomatosis kept rabbit numbers low. Experiments demonstrated that unprotected seedlings are quickly found and eaten by rabbits, particularly if alternative foods are scarce.Sufficient numbers of ti‐trees are presently recruited to ensure the persistence of that species, but a programme of rabbit control would be necessary to enable natural regeneration to perpetuate the sheoak population in the Coorong National P

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1988.tb01414.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractThe results of pollen, sedimentary and charcoal analyses of four cores and three peat profiles are presented.Casuarinawoodland dominated the dryland vegetation over at least the past 6000 years, with aMelaleucalanceolata‐composite scrub association on the dunes. There is no evidence of higher sea levels in the area in the past 6000 years, with the present freshwater backdune swamp and lake systems being maintained or expanded. After a period of regional dune building between about 6000 and 4000 years BP, dune mobilization and advance in the last 4000 years or so overrode seaward brackish and fresh swamp systems. This dune advance severed Long Swamp from the Glenelg River estuary and precipitated the development of freshwater swamp conditions there. Burning of the swamp surface, often associated with the presence ofTypha, is evident in a number of peat samples and is probably primarily anthropogenic. Continuous low‐level burning occurred throughout the dryland vegetation of the region but is not associated with any long‐term or widespread vegetation change. None of the environmental changes identified require a purely climatic explanation, and all have relevance for discussions of the regional prehi

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1988.tb01415.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractPopulation dynamics and habitat preferences of the dusky rat,Rattus colletti, were examined in the seasonal wetlands of the South Alligator River. Northern Territory, between late 1979 and 1982. Demographically, the species is characterized by short‐term seasonal shifts between habitats superimposed on a longer‐term irregular pattern of prolonged breeding and population irruption, followed by periods of relative rarity. These patterns are determined by the train of climatic events. The flexible life history strategy and movement patterns ofR. collettireflect fine‐scale adaptation to a climatic regimen which is markedly seasonal, but also highly variable between years in the amount and temporal patterning of rainfall.The distribution ofR. collettiamongst vegetation types is influenced by two sets of environmental factors, both reflecting a gradient in elevation, soil type and vegetation. The primary factors are vegetative cover and height, and the extent and duration of flooding; the secondary set comprises buffalo‐induced features such as the degree of pugging and grazing. These factors are interrelated, and their relative importance toR. collettivaries greatly between seasons.Feral buffalo appear to exacerbate the harsh effects of the wet and dry seasons. The removal of these animals may ameliorate environmental conditions considerably, both temporally and spatially, resulting m generally higher, more stable and spatially less variable populations ofR. c

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1988.tb01416.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractHistorical records for the Bega district were examined to chart the environmental changes wrought by Europeans through habitat alteration and the introduction of exotic species, and to interpret the impact of these on native mammals. Early recorded increases in native mammal populations, particularly koalas, may have been attributable to a decline in Aboriginal hunting pressure. After settlement in 1830, the valley forest was cleared progressively, ecosystems were altered by grazing and improved pastures, and many introduced plants became weeds in the disturbed environment. The timber industry exploited the forests of the valley and then the slopes of the surrounding mountains. Three exotic mammal species had a major impact on the district — hares, rabbits and foxes. Of the native fauna, the large and medium sized mammal species were those recorded most frequently. Dramatic fluctuations in numbers occurred in most of these species, and many reached plague proportions between 1880 and 1910, after which their numbers fell sharply. The peaks of exotic mammals and the decline of native mammals coincided with the clearing of the remaining forests in the Bega Valley. Many native mammal species are now rare, four are in danger of extinction, and at least six species have become locally extinct since settlement. As most of the native mammal populations in the district now occur in the State Forests surrounding the Bega Valley, the importance of preserving or managing these forests for wildlife must be weighed against proposals to manage the forests for pulpwood (woodchip) productio

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1988.tb01417.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractThe effect of a number of experimental handpollination regimens on the numbers of seeds set byBlandfordia nobilisflowers was assessed. Individuals were found to be self‐incompatible and to require pollinator visits to set fruit. Pollen limited the female component of reproduction in the two populations studied while pollen source did not have a significant effect on the numbers of seeds set. Experiments using a stuffed honeyeater indicated that maximal seed set could be achieved after just one probe by the pollinator. Appreciable heterogeneity in flowering phenology, the number of seeds naturally setting and the number of seeds setting as a result of hand‐pollinations existed within a small area across a single flowering sea

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1988.tb01418.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractCrown cover can be used to describe or classify woody vegetation. However, current methods for the estimation of crown cover are difficult to apply and are time‐consuming. The objective of this work was to present a much easier method of field estimation and to define the limitations of the method.The method uses the crown‐gap ratio (C), which is defined as the mean gap between crowns divided by the mean crown diameter. The relationship between values for the crown‐gap ratio and crown cover is of the form crown cover = k/(1 + C)2, where k is a constant.The overall tasks are first, to develop a methodology to obtain estimates of C and crown openness in the field, and second, to estimate k.In Part 1 we demonstrate that crown cover can be related to C when applied to woody vegetation. In Part 2 we consider a derivation of C, determine a value for k given a set of constraints, and outline some of the sampling implications of applying the method of crown cover estimation using C and k to field situations.The field study provided data from which to plot crown cover against the crown‐gap ratio (C). The shape of the curve approximated a rectangular hyperbola. The regression of crown cover against 1/(1 + C)2showed a strong linear relationship (R2= 0.995) and gave an estimate for k of 0.79 for the range of plant communities sampled.The field study suggests that to investigate the effect of different spatial distributions of crowns and mixtures of crown sizes on C, a rigorous derivation of the relationship between crown cover and C is r

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1988.tb01419.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractThe crown‐gap ratio C is defined as the mean distance between adjacent crowns divided by the mean crown diameter. Previous field studies have established that for a limited range of vegetation stands crown cover is related to C by a general function, viz. crown cover = k/(1 + C)2, where k is a constant. In the present study we investigated the general derivation of the function which relates crown cover to C. The function was then used to determine values for k, a range of point distributions being simulated from semi‐regular to clumped, with mixtures of crown sizes.The relationship between crown cover and 1/(1 + C)2was linear in all cases tested (R2= 1.0). The value of k was shown to depend on the sampling technique used, the degree of clumping, and the range in crown sizes permitted.The variation in k was reduced by using a specific sampling method and limiting the range of spatial distributions and crown sizes considered.The constraints imposed were:1Sampling followed a zig‐zag transect (Delaunay two‐sided model).2Point distributions were not overly clumped.3The range of crown diameters approximated a Gaussian distribution with a relative range of 1–4.Given these constraints the value of k was determined to be 0.806 with a variance of less than 2%. A table is given to convert values for C into crown cover percentages and, if required, to calculate foliage cover per cent.The constraints imposed are considered to be within conditions normally encountered in the field, making the use of C an accurate and simple method by which to estimate crown or foliage cover

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1988.tb01420.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Book Reviewed in this article:The Botany of MangrovesP. B. Tomlinson.Ecology of MangrovesP. Hutchings, P. SaengerEcology: Individuals, Populations and CommunitiesM. Begon, J. L. Harper, C. R. Townsend.Population Ecology: a Unified Study of Animals and PlantsM. Begon, M. Mortimer.The Physiological Ecology of LichensK. A. Kershaw.Kangaroos: their Ecology and Management in the Sheep Rangelands of AustraliaEdited by G. Caughley, N. Shepherd, J. Short.Evolutionary Ecology of MarsupialsA. K. Lee, A. Cockburn.Biogeography: An Ecological and Evolutionary ApproachC. B. Cox, P. D. Moore.

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1988.tb01421.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1988.tb01422.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY