摘要:

AbstractPalaeontological evidence raises several questions that relate to current explanations of ecological communities, to the classification of communities and to interpretations of species richness. The first question relates to the stability of species detected in the fossil record. Coupled with that is the issue of incidental association of species on the same trophic level through differential effects of climatic change on the different species. Such observations are seen to support the ‘individualistic’ concept of communities. Recent statements about this concept leave unresolved questions about the acquisition of adaptation, and about the place of adaptation theory in theories of ecological communities and interpretations of ‘regional species richness’. At issue is whether there is justification for continuing to classify communities as a basis for understanding them. There is good reason to reject this approach for one in which questions about communities and ‘local’ and ‘regional’ species richness are replaced by more specific and basic questions about the relationship between adaptation, distribution and abundance, and ecological interactions. Some recent efforts to incorporate species theory into community theory fail because their basis remains the flawed concept of

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1994.tb00488.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractThis review provides a synthesis, from published and unpublished sources, of records of mycophagy (fungus‐feeding) by Australian mammals. Mycophagy is shown to be widespread among Australian mammals, paralleling the previously well‐documented situation in North America. Mycophagy appears to be most prevalent within the Potoroidae (rat‐kangaroo family) but has also been recorded for a variety of other mammals. Information is presented on the classification, morphology and ecology of the fungi consumed, on the nutritional benefits (or otherwise) of mycophagy, and on the role of mammals in spore dispersal. Fungi whose sporocarps are hypogeal (truffles, false‐truffles and sporocarpic Endogonaceae) and which enter into mycorrhizal relationships with plants predominate among the species recorded in mamma

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1994.tb00489.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractThe study assessed the survival, during bushfires, of seedbanks of six serotinous Hakea species found in the Sydney region of southeastern Australia. The survival of seeds was examined when fruits were heated in a muffle furnace at ambient temperatures ranging from 200–800°C for 1 min. For each species, fruit weight and dimensions of fruit walls were measured to characterize insulation. A field experiment was performed to examine the survival of the serotinous seedbank ofHakea dactyloidesin a bushfire. Ambient and internal fruit temperatures were recorded during the fire. The viability of seeds from fruits exposed to the fire was tested and compared with an unburnt sample.Viability of seeds within fruits exposed in the furnace varied according to species. Seeds of large fruited species such asHakea constableiandHakea propinquasurvived, whereas those of the small fruited speciesHakea teretifoliaandH. dactyloidessuffered significant mortality. The threshold temperature for death in four species was linearly related to the thickness of lower and lateral fruit walls, and to dry weight of fruits.Internal and external temperatures of fruits decreased with increasing height on experimentalH. dactyloidesplants in the field. High levels of mortality (relative to the unburnt control) corresponded with fire temperature maxima greater than 400°C (external) and greater than 60°C (internal). In general, these temperatures occur when shrub crowns burn. A high risk of death forH. dactyloides, H. teretifoliaandH. sericeaseeds will result because fruits of these species have thin w

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1994.tb00490.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractMany molluscs in tidal wetlands climb trees as the tide rises, a behaviour usually assumed to be a means of avoiding subtidal predators. Some species are more active during neap tides, when the access of subtidal predators to the forest is limited, but rest on trees during spring tides.Cerithidea anticipata, which inhabits the mangrove forests around Darwin Harbour (Northern Territory, Australia), displayed almost exactly the opposite pattern. This species climbed higher, and was less active, during neap tides that did not flood the forest than during spring tides. In experiments with tethered snails, individuals prevented from climbing died during neap tides, apparently from physiological stress. Further, individuals resting on trees around clearings, usually selected shaded sites. These results suggest that the major reasonC. anticipataclimbed was to avoid physiological stress during neap tides, not subtidal predators during spring tides. There was some evidence of predation under the canopy, but the rate was relatively low and the species responsible appeared to be resident in the forest.

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1994.tb00491.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractAcacia salignaandAcacia cyclopsare the dominant invasive alien plants of phosphorus‐poor, sand‐plain, lowland fynbos and the relatively phosphorus‐rich strandveld vegetation of the southwestern Cape of South Africa, respectively, but their ranges overlap. Seedlings of the two species were grown in pots, in isolation and mixed, in up to seven treatments supplying a broad gradient in phosphorus (P) availability.Acacia salignaseedlings grew taller and had greater dry mass than those ofA. cyclopsat each level of P, but both peaked in response to the same relatively high soil P level and then tended to decline. Root : shoot ratios did not differ in response to P, but were greater inA. saligna. In mixture,A. salignahad a higher dry mass thanA. cyclopsat each level of P, but the relative differences between species were no greater than in isolation. Depth penetration of the soil by the tap root ofA. salignaseedlings was over three times as rapid as that ofA. cyclopsover a 30 day period. The higher absolute growth rates ofA. salignawere not related to seed size or seed nitrogen and P contents, as these were greater inA. cyclops. The contrasting distributions of the acacias do not appear to be a response to P availabilityper se, but possibly to the interaction of P with other factors such as moisture availab

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1994.tb00492.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractSeventy‐three per cent of dry rainforest in Forty Mile Scrub National Park and large areas in adjacent savanna woodland have more than 5000 individuals per ha of lantana (Lantana camaraL.). Transect studies in dry rainforest and savanna woodland across varying intensities of lantana infestation show a negative correlation between the density of lantana and tree cover in rainforest. The density of pig rooting is very high in areas of the dry rainforest on deep soil that was not heavily infested with lantana. It is suggested that the digging activities of these animals may cause tree death and subsequent increased light penetration, which favours lantana. The species richness of the dry rainforest declines as the density of lantana increases. However, the saplings and seedlings and the soil seed bank of dry rainforest and savanna woodland tree species have comparable densities in heavy and light lantana infestations. The proliferation of lantana results in the build up of heavy fuel loads across the boundary of dry rainforest and savanna woodland. Recent fires have killed the canopy trees in a large area of dry rainforest within the Park. Active management of Forty Mile Scrub National Park is urgent and some initiatives are suggeste

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1994.tb00493.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractA computer‐based model is presented that brings together the existing knowledge about the dynamics of bracken in eucalypt forests in south‐eastern Australia. The average length of the growing season, the timing and extent of logging, and the timing and severity of fire are major inputs to the model. The model is predominantly deterministic, but has a stochastic environmental component. The model is validated with four independent sets of data. The model successfully predicts the trends in the data. The interactions between bracken, other understorey species and eucalypt regeneration are explored with the model. The likely effect of different silvicultural and fire management practices on the cover of bracken are investigated using the model. Year to year variation can mask the effects of disturbance if bracken cover is viewed in any one year in isolation. Bracken cover trends can only be seen over a period of 10 years or more. The model reinforces the importance of site productivity as measured by length of growing season and the degree of tree removal on bracken co

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1994.tb00494.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractAlpine sand dunes are a rare phenomenon. On the Central Plateau of Tasmania parabolic dunes occur on the leeward of glaciofluvial lakes. The largest such complex is at Lake Augusta where seven sand dune communities and two slack communities were recognized from a sorted table produced by a polythetic divisive classification of floristic data. Fen was found on the rocky parts of the lake shore, while short alpine herbfield (‘marsupial lawn’) occurred in seasonally inundated slacks. Freshly mobilized sand had distinct shrubland communities, two of which exclusively occupied the fresh sand of the foredunes, while one occurred on remobilized older soils. Three communities formed a toposequence on the older soils of the well‐drained dunes. Zonation was not strong beyond the foredune. Species richness and height generally increased inland. The older soils were more nutrient rich than the younger sands, a phenomenon probably attributable to the ultimate igneous origin of the material. The dunes have considerable conservation significance. Activities that could cause further mobilization need to be restr

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1994.tb00495.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractThirteen lichen species were studied on trunk segments ofPinus radiataD.Don between 1.0 and 1.5m above‐ground from five plantings of known, different ages near Linton, Victoria. Significant frequency and size‐class differences were found for most species between sites. These parameters generally increased up to 32 years, and then either declined or showed evidence of recolonization by small thallus size‐classes in some species. Nevertheless, only relict populations for any species were present at 52 years. Most species had no aspect preferences; only three species had a significant majority of their thalli on the western trunk face. Site‐species association frequency analyses clustered, as pairs, the 11 and 52, and 16 and 39 year old sites. These site patterns were correlated with a number of environmental factors as well as species abundance at the sites, but there is also a possible response by the community to bark shedding, seen after 32 years, with a return to earlier colonization states in the system. This cyclic pattern is similar to a competitive hierarchy succession, although due to accelerating chronic disturbance (bark shedding) the system may be subject to secondary succession and, ultimately, to severe degr

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1994.tb00496.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractThe effect of plant size on reproduction in four species of alpineRanunculus (R. muelleri, R. dissectifolius, R. graniticolaandR. niphophilus) was investigated in two sites over two seasons in the field on a total of 190 plants. The effects of plant size (number of leaves) and number of flowers on the number of anthers, ovules and seed per flower and per plant were determined. There was a positive relationship between several measures of reproduction and plant size in all four species, indicating that reproduction is size‐dependent. All the results indicate that the main factor controlling the amount of seed produced by alpineRanunculusis the size of the plant. Specifically, bigger plants produced more seed by producing more flowers, not by producing more ovules per flower, or higher seed set per flower. Correspondingly, bigger plants produced more anthers by producing more flowers, rather than by producing flowers with more anthers. The total number of seeds produced by a plant was directly proportional to plant size in the four species. Therefore, reproductive effort should not vary with plant size in the four specie

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1994.tb00497.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY