ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1979.tb01194.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractThis paper describes the application of theLesliematrix model to single species populations, and a similar transition matrix model to communities of more than one species. Examples are drawn from populations ofAraucariaspp. in tropical rainforest in Papua New Guinea, and fromNothofagus fuscastands in temperate montane forest in New Zealand. Both species generally had λ values close to 1.0 (r, the intrinsic rate of natural increase ≃ 0) and in both cases predicted trends were consistent with other ecological information from the stands or elsewhere. Various possible sources of error and empirical tests of the sensitivity of the single species model and the accuracy of its predictions are described. It is concluded that, despite certain limitations, with careful interpretation these models constitute an important tool for the investigation of forest dynamics.The basic model may be modified in various ways, for example, to include vegetative reproduction, or put to use in practical problems such as defining a harvesting strategy for a forest tree species. In studies of succession involving long‐lived species these models are particularly valuable, not only for predicting the magnitude and direction of future changes, but also because they suggest a time scale for the trends, and this can then be evaluated in the light of other knowledge about the communities in question. Moreover, the variability of λ values obtained for differen species relates to their life cycle strategies, so that by the use of Leslie matrices it may be possible objectively to rank the species of a community along the continuum of r to k strat

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1979.tb01195.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractField responses to various burning and grazing treatments in three sites on the Southern Tablelands were measured. Grazing by native mammals was unrestricted and continuous. Burning occurred once from fires of low intensity. Records of mortality, height growth and in some cases, seed production showed biologically significant effects of the treatments imposed on small plots.Dillwynia retortaplants were susceptible to a single fire but the species persisted through seedling germination. Other species showed vegetative survival to various extents from the fire. The burning–grazing combination was particularly potent in affecting survival, regeneration and growth of all species. Supplementary evidence of species’ responses were gathered from the treatment of selected individuals in the field and laboratory.Some of the implications of these results and in particular the practice of controlled burning are discussed in relation to the management of reserves set aside for flora and fauna conservat

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1979.tb01196.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractOn Macquarie Island (54° 30′S, 158° 57′E), herbfields dominated byPleurophyllum hookeriBuchan. typically occur on waterlogged peat soils from near sea‐level to approximately 340 m. They are also found on drained slopes; at higher altitudes on sheltered sites, and at lower altitudes as seral communities on screes and landslips.Pleurophyllum (Compositae), a relatively large‐leaved rosette plant, has features of both a geophyte and a hemi‐cryptophyte, and regenerates by both seedlings and axillary rhizomes.The herbfields are usually strongly patterned; the distribution ofPleurophyllummay be regular, random or clumped. The types of pattern are largely determined by the influence of environmental factors on the morphology and performance of both the dominant and other species. Drainage, exposure to wind, and temperature, as determined by altitude, are clearly important. The pattern is also strongly influenced by the balance between seedling and vegetative reproduction of the dominant species, and the outcome of competition with associated species, both vascular and cryptogamic.An extension to the basic method of pattern analysis, involving repeated analyses using only successively larger, older plants demonstrates that different age classes of rosettes show different scales of pattern. In the various types of pattern and process in these herbfields,Pleurophyllummay alternate with eitherStilbocarpa polarisA. Gray, graminoids or bryophytes. There is no clear predictive relation between patterns as revealed statistically and the types of pattern

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1979.tb01197.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractSeven species of grazing molluscs, two littorinids, one nerite, three limpets and one chiton, lived on the vertical intertidal rock wall at the landward edge of the coastal limestone platforms at Rottnest Island, Western Australia. On the average, the vertical ranges of these species overlapped broadly, although a consistent zonation pattern was conspicuous from the platform surface upwards for 2 m.On these vertical intertidal shores, physical and biological conditions were predicted quantitatively from easily made measurements of vertical height on the shore; the percentage of time any shore level was immersed in seawater, the percent weight loss of plaster clods, the standing crop of algae, and the growth rate of the limpet,Notoacmea onychitis, all decreased linearly or semi‐logarithmically with increasing height on the shore. The standing crop of animals was greatest, largely due to the presence of the chiton, between 40 and 70 cm from the platform surface and decreased rapidly down the shore and more gradually towards higher shore levels.We interpret this information and the positive correlation between algal production rate, and egestion rate of the animal community at various levels of the shore as evidence supporting the idea that food may be in short supply on these shore

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1979.tb01198.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractThis study evaluates the adaptive significance of host preferences and searching behaviour in Vancouver and Canberra populations of the cabbage butterflyPieris rapae (L.).As a result of a complex of responses to plant age, the butterflies concentrate their eggs on middle‐aged plants. Young larvae develop faster and survive better on young plants than old ones, but larvae on smaller plants are more susceptible to crowding effects. Thus a preference for plants which are well‐grown but not too old is selectively advantageous. By contrast, the butterflies’ host species preferences appear non‐adaptive, and are unrelated to the quality of the host as larval food.Vancouver butterflies change their flight direction often and are very responsive to hosts, thereby generating a very aggregated distribution at a low cost in flight time. Canberra butterflies tend to fly in straight lines and are less responsive to hosts; their egg distribution is consequently more nearly random, but they fly further for each egg they lay. The relative costs of aggregation and increased flight time differ between the populations in a manner consistent with the observed behavioural diff

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1979.tb01199.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractThe abundances of litter and soil fauna and some related environmental measures are given for two Australian subtropical forests, a notophyll vine forest (or rainforest) and a wet sclerophyll forest. Animals were more abundant in the wet sclerophyll forest; peak abundances were recorded in summer in both forests. Mites and Collembola accounted for 79% of the rainforest fauna and for 85% of the wet sclerophyll forest fauna. Most mites in the wet sclerophyll forest were Crypto stigmata (68%); in the rainforest both Cryptostigmata and Mesostigmata were well represented (84%). Patterns of aggregations of individuals within major faunal groups differed for the two forests. Correlations are made between the numbers of individuals of Collembola, of mites and of each order of mite and the environmental measures. Significant correlations emerged for some environmental measures in some seasons. Results are compared with those of other studies and it is concluded that poor or no humus development restricts the numbers of individuals living on tropical or subtropical forest floors. Speculations are presented to account for the difference between the faunas in the two Australian subtropical forests.

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1979.tb01200.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractThe capacity for increase (rc) of three populations ofS. oryzaeand three populations ofS. granariusfrom Great Britain and Canada was determined over 15 and 24 weeks respectively at 15°C in wheat of 14% moisture content. The fertility of these populations at 27°C, their body weight and chill‐coma threshold was also measured.With bothS. oryzaeandS. granarius, values of rcfor the foreign populations fell within the range previously observed when several Australian populations were reared under the same conditions. The cohort generation times (Tc) of the foreignS. oryzaepopulations were significantly shorter than those of the Australian populations because of the shorter immature development periods (D) of the former. Two of the foreignS. granariuspopulations had lower values for D than all but one of their Australian counterparts but their values of Tcwere within the range previously observed for Australian weevils. When the Australian and foreign populations were considered together, the value of rcwas more strongly correlated with fertility at 27°, an optimal temperature, than with body weight in bothS. oryzaeandS. granarius.WithS. oryzae, rcwas correlated with the chill‐coma threshold of cold‐acclimated weevils only. There were no correlations between rcand chill‐coma thresholds inS. granarius.It was concluded that the observed differences in rcwere related to differences in the vigour of the populations rather than to physiological differences in cold‐tolerance.The likelihood of grain weevils becoming cold‐tolerant as a result of grain aeration is discussed and the practical significance of differences i

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1979.tb01201.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractResults of a mark‐release study ofRattus sordidus colletti(Gould) on sub‐coastal, treeless plains in the monsoonal north of the Northern Territory of Australia are given for 5 years.R. s. collettiis the dominant component of the small mammal fauna of these plains, with only small numbers of Melomys spp. and Planigale maculata also occurring. Two classes of peak densities were observed. Localized peaks resulted from non‐breeding adultR. s. collettirefuging onto the marginally higher levees during flooding of the plains, and also from refuging into a lower‐lying area at the end of a dry‐season drought. Generalized peak densities resulted from peaks in reproductive effort. In 1972 and 1974, reproduction was confined to the period immediately following the monsoons, but in 1973 breeding continued throughout the dry season, following unseasonal rain in June. Thus, generalized peak densities were observed in one year at the beginning of the dry season, and in another at its end. The relatively shallower flooding and mildness of the 1972–3 wet season resulted in commencement of breeding earlier in 1973 than in 1974, while rapid severe flooding of the plains in December 1974 resulted in mass mortality and failure of the refuging populations of adults to recolonize the lower plains in 1975.R. s. collettiremained extremely rare until November 1976, when the study was terminated.The good conditions which allowed reproduction during the dry season of 1973 were reflected in rapid growth rates at that time, compared with rates approaching zero in the 1974 dry season.R. s. collettiis the most fecund form of Australian Rattus species. This high fecundity appears to compensate for the restriction, by dry‐season aridity and wet‐season flooding, of the breeding season in most years to a short period immediately following the monsoons. In unusual years with rainfall during the dry season, the high fecundity givesR. s. collettipopulations the capacity to reach very

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1979.tb01202.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

The ecological effects of pesticides on non‐target organisms David L. Mowbr

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1979.tb01203.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY