摘要:

AbstractThe geographical limits ofNothofagus cunninghamiiare highly correlated with climate and appear to be more or less in equilibrium with the climate of the present century in all but one of the areas of its present range. It is suggested that suitable climates for the species occur in the highlands of northeastern Victoria and southern New South Wales, beyond its present range, and it is possible that it occurred within the predicted area prior to the last ice age. It is suggested that populations ofN. cunninghamiialong the northeastern edge of its present range in the Central Highlands of Victoria may be migrating northeast along a narrow corridor of apparently suitable climate to re‐occupy the postulated former range. The rate of migration would be expected to be extremely slow because of the poor dispersal ability of the species and the adverse impact of recurrent fire

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1986.tb00912.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractAccession, decomposition and accumulation of litter were studied in three sub‐alpine eucalypt forest communities (dominated by overstoreys ofEucalyptus delegatensis, E. paucifloraorE. dives) located in the Brindabella Range. Australian Capital Territory, at an elevation of 1100–1250 m. The sites had either been protected from fire for more than 20 years or been burnt by low‐intensity prescribed fires. After a prescribed burn, the rate of decomposition of abscised leaves was reduced by 22% inE. delegatensisforest and by 34% inE. paucifloraforest, but was little affected in the drierE. divescommunity. Lowered decomposition was apparently due to greater aridity after fire, a consequence of removal of the shading understorey and reduction in the depth and hence mulching effect of the titter layer. Litter accumulates rapidly after prescribed burning, reaching a mass of 10–12 t ha−1within 4–5 years in all communities. Such quantities are dangerous from a fire control viewpoint. The quasi steady‐state mass of accumulated litter ranges from about 17 t ha−1in E. divesandE. pauciflora forests to about 25 t ha−1in old‐growthE. delegatensisforests. The rapid re‐accumulation of litter after fire is not the result of any significant change in litterfall rate, but is due to a marked reduction in the total amount of litter decomposing—and this reduction is more a consequence of a decrease in the weight of the forest floor than to any fire‐induced lowering of the rate of litter decomposition. The rapid build‐up of litter is a consequence of the relatively high rates of litterfall (3.4–5.0 t ha−1year−1) and low rates of litter decomposition (k = 0.19–0.32 year−1) in these forests. In most cases the pattern of litter accumulation was well described by an exponential equation of the form Xt= Xss(1—e‐kt), where Xtis the weight (t ha−1) of litter accumulated at time t (year). Xssis the weight of litter accumulated under steady‐state conditions, and k is a decomposition rate constant (year−1). Marked temporal variations in annual litterfall and mass of accumulated litter were found at specific forest sites which had been unburnt for more than 4.5 years. Variation from the long‐term mean was greater for litterfall (31–37%) than for accumulated litter (14–26%). The maximum error when calculating decomposition rate (k) as the ratio of annual litterfall: accumulated titter, when based on single measurements of these parameters, ranged from 43 to 69% of that based on long‐term measurements. Decomposition rates of the entire titter layer, calculated for periods of 22–79 months, and based on measurements of litter input and change in mass of accumulated titter, were positively correlated with the average number of days per month during each period that the litter layer remained moist (>approx. 60% ODW). The implications of these findings for fire management planning in su

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1986.tb00913.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractNui Atoll, an isolated atoll in Tuvalu, has a total vascular flora of 86 species, including a large number of introduced species. If only the 44 species considered indigenous are examined, there exists a strong linear relationship (r2= 0.94) between the total number of species and the logarithm of island area, over the entire wide range of island sizes from 0.01 ha to 138 ha. This relationship is strong for both three species and herb species, but weak for shrub species for which there is a limited pool of potential colonists. This relationship is stronger than on other Pacific atolls and does not support the existence of a ‘small island effect’. The strong linear relationship on Nui is attributed to uniformity of reef island substrate, distribution and isodimensionality of reef islands, stability of islands and infrequency of catastrophic events and the absence of large monospecific stands, especially of shrub species, characteristic of drier ato

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1986.tb00914.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractAn assessment of the performance of a wetland dominated by opportunistic weeds in removing nutrients from a secondary sewage effluent was carried out at Thredbo in Kosciusko National Park. Water quality sampling of the inflow and outflow showed a reduction in turbidity, pH and conductivity with passage through the wetland. Dissolved oxygen levels also decreased. In summer 1982, the phosphorus toad of 1.8 kg P day‐1was reduced by 44% as wastewater moved through the wetland, and the nitrogen load of 6.4 kg N day‐1by 65%. Winter retentions were 10% and 14% of inflowing loads, respectively. In 1983 there was a net release of phosphorus and reduced retention of nitrogen. This was regarded as being a result of physical disturbance of the wetland. Vegetation downstream of the effluent inflow was dominated by the opportunistic weedsEpilobium sarmantaceumandRumex crispus. Upstream,Carex gaudichaudianaandBaeckea gunnianadominated. Marked seasonal changes in vigour and biomass were recorded. Plants, but not sediments, downstream of the inflow contained more nutrients than those upstream. Seed bank analysis showed more seeds downstream than upstream. A moist treatment promoted more seed germination than a flooded treatment.E. sarmantaceumand to a lesser extentR. crispusdominated in each treatment. In an effort to promote greater water retention and replacement of the weed species, channels in the wetland have been blocked with gravel and planted withPhragmites australisandSchoenoplectus vali

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1986.tb00915.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractA sample of 261Ctenotus taeniolatusrevealed that this species of skink is principally insectivorous, the most common foods being lepidopteran and coleopteran larvae, orthopterans and formicids. The occurrence of these foods in the diet followed seasonal patterns. The prey of adults and juveniles did not differ qualitatively, although adults were capable of eating a greater diversity of prey sizes than juveniles. Lizards used both sit‐and‐wait and active foraging strategies, with adults and juveniles exhibiting these behaviours in different rat

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1986.tb00916.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractThe oviposition patterns of adults and the movement and feeding patterns of larvae ofEpilachna cucurbitaeon two species of cucurbits, Cucurbita maximacv Queensland BlueandC. pepo cv Blackjack, were studied in the field and laboratory. The physical and nutritional characteristics of host plant leaves of different ages were described. Younger leaves had higher nitrogen contents but were less abundant, smaller and had higher trichome densities than older leaves. The development of first instar larvae was delayed by the leaf hairs on young and mature pumpkin leaves which prevented larvae from reaching the leaf surface to feed First instal larvae developed more quickly on leaves rich in nitrogen. Neither the total developmental time of larvae nor the size of pupae was affected by leafage because larvae on poor quality leaves compensated by eating more. Female beetles oviposited on all but the youngest and oldest leaves of the host plant. The trichomes on young leaves prevented females from attaching eggs to the leaf surface. First instar larvae remained where they hatched, but older larvae were more mobile, Changing feeding sites frequently and moving progressively to younger, more nutritious leaves. Final instar larvae moved onto adjacent vegetation to pupate. The adaptive significance of these patterns is discussed in relation to the nutritional value, hairiness and abundance of host plant leaves of different ages and the physical limitations of different larval instars.

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1986.tb00917.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractThe numbers of honeyeaters present at particular sites in the Jarrah forest varied significantly from month to month, with peak abundance occurring between May and September. Numbers also varied from site to site, depending upon the major plant species present. Honeyeater abundance was not limited by arthropod availability, but in many instances was closely correlated with the availability of nectar, particularly that produced byDryandra sessilis.Large honeyeaters, such asAnthochaera chrysopteraandPhylidonyris novaehollandiae, were generally most abundant at times and sites of greatest nectar production. Small honeyeaters, such asAcanthorhynchus superciliosis, were never abundant but were present for most of the year. The production of nectar between October and December was such that more honeyeaters could have been supported than were actually present. Low numbers at these times can be explained in terms of reduced foraging efficiency that would have resulted from more widely dispersed flowers, and the possible availability of more rewarding nectar resources at other sites.

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1986.tb00918.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractA long term study site which had not burnt since 1968 was partly burnt in August 1974 and the entire area burnt again in August 1980. The two wildfires, in the same season and with similar intensity, allowed a study of the effect of the frequency component of the fire regime on the floristic composition and structure of a shrubby woodland understorey. In 1982, 2 years after the last fire, that part of the site burnt twice in 12 years had significantly more plant species, higher shrub density and greater cover than that which burnt once only. Of the species found only on the single‐fire part of the site, all were obligate seedling regenerators, while the larger number of species found only on the twice‐burnt part were predominantly vegetative regenerators. The results have implications for vegetation managers: areas burnt too frequently may lose obligate seedling regenerators, while an area remaining unburnt for too long may lose some vegetatively regenerating species, as well as short‐lived obligate seedling regenerators. This highlights the necessity for research in different vegetation types to assess adequately these limits to their ‘natural’ frequencies. Such research would form the basis for informed management

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1986.tb00919.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

Abstractstudy of the ants of 11 sites at Wilson's Promontory, Victoria, found that patterns of ant community organization varied markedly between habitats, being controlled by climate and vegetation structure. Community organization showed continuous change from drier sites (especially woodlands) where broadly‐adapted species ofRhytidoponerawere particularly abundant, but many other taxa were also well‐represented, to wet forests where cool‐climate specialists(Prolasiusand certainChelaner)and cryptic species (mostlySolenopsis)cotnprised almost all ants. These patterns appear to be typical of those in mesic regions of Australia, and contrast with those in the arid zone where ant faunas are dominated by highly active and aggressive species ofIridomyrmexwhich apparently play a pivotal role in community organization. The results suggest that ant communities in mesic regions are less tightly structured than those in the arid zone, and that interspecific competition is a less important factor influencing community organization. The findings of this study are briefly discussed in relation to the potential use of ants as bio‐ind

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1986.tb00920.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY