摘要:

AbstractFour 0.125 m2soil samples, 50 mm deep, from each of eight tropical lowland rainforest sites ranging from primary and secondary forests to degradedImperatagrasslands were exposed to shade‐house conditions. Germinations of soil seeds were monitored over 28 weeks in April‐October. The viable seed banks in the primary forest (592 m‐2) and the secondary forest sites resulting from one cycle of clearing and abandonment (1300–1400 m‐2) were composed predominantly of secondary species. The viable seed banks were small inImperatagrassland sites that had been burnt regularly (200–400 m‐2) and very large (2000–3000 m‐2) in sites that had not been burnt for five years or more. The seed banks of the burnt and unburntImperatagrassland sites were composed mostly of agricultural weeds whilst seeds of secondary rainforest trees were rare or absent. Similarities between the species composition of soil seed banks and regrowth vegetation types suggest that soil seed composition is important in determining the initial floristic composition following disturbance and that lack of seed of secondary rainforest trees is one factor which restricts re‐growth and secondary succession on degradedImperatagrasslands. Species such asEucalyptus intermediaR. T. Bak., E. pellitaF. Muell. andImperata cylindrica(L.)Beauv. which can establish and deflect the normal rainforest secondary succession were not present in the soil seed bank, and these species appear to rely on fresh seed inputs, lignotubers or rhizomes to colonize and regenerat

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1984.tb01345.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractThirteen floristic communities are recognized by numerical analysis of the vegetation of a part of the West Coast Range containing the climatic station with the highest mean annual precipitation in temperate Australia, and a variation in altitude from 400 to 1200 m. These communities form an altitude‐related sequence with a perceptible break at the transition to alpine vegetation. Within rainforest three intergrading groups also form an altitudinal sequence. However, total environmental stress, as reflected in growth rates, is hypothesized to control this floristic and richness gradient. Direct and indirect gradient analysis reveals a lowland successional sequence from sedgeland to rainforest. Although some alpine communities are clearly the product of firing of others, there is no analogue of the lowland sedgelands. Fire‐induced change in both alpine vegetation and rainforest can be extremely long term. Soil drainage is important in the differentiation of both lowland and alpine communit

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1984.tb01346.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractIt has often been assumed that the introduced speciesChrysanthemoides moniliferais displacing native species in invaded coastal communities in Australia but no direct evidence has been presented that this displacement is occurring and, if so, to what extent. At an invaded site near Moruya, New South Wales, we found strong negative correlations between the presence (measured as cover, frequency or volume of shrub) ofC. moniliferaandAcacia longifolia,the hitherto dominant native species, and ofC. moniliferaandLomandra longifolia.The negative correlations are partly accounted for by differences in the amounts of each species on different zones on the dune, but the negative correlations remain even within these zones. Also a comparison with uninvaded sites indicates thatC. moniliferais displacingA. longifoliafrom the fore‐dune and mid‐dune but is having less effect in the swale. In addition, there is a trend towards reduced seed production ofA. longifoliawhen growing in proximity toC. monilifera.There is no significant difference in the presence ofL. longifoliain the uninvaded and invaded sites. In invaded sites, significantly fewerC. moniliferaseedlings occur in the presence ofL. longifolia.Thus it appears that the observed negative associations arise from different causes.Chrysanthemoides moniliferais displacing the structurally similar, and previously dominantA. longifolia,while the tussock‐formingL. longifoliais locally hindering the inv

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1984.tb01347.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractThe seed production, germination and regeneration characteristics of two native species(Acacia longifoliavar.sophoraeandBanksia integrifolia)and two invasive subspecies(Chrysanthemoides moniliferassp.moniliferaand ssp.rotundata)were compared.C. moniliferassp.rotundatawas similar in seed characteristics and regeneration toB. integrifoliain that: (1) seed production was over an extended period each year; (2) seed longevity was low (0–2% viable after burial for 3 years), but increased with depth of burial; and (3) regeneration from 26 to 28% of mature plants occurred after fire.By contrast, C. moniliferassp.moniliferawas similar toA. Iongifoliavar.sophoraein that; (1) seed production was over a short period each year; (2) of the total buried, 6–13% of seeds were viable after 3 years, and again numbers increased with depth of burial (percentages of missing seeds ofA. longifoliawere high but all remaining seeds were viable after 3 years); and (3) regeneration after fire occurred only from seed, hence their seed longevity is an important factor for long‐term survival.However, growth habit and niche occupation by ssp.rotundatais similar to that ofA. longifoliaand the above differences may contribute to the observed displacement of the native by the invasive species. The distribution of the two invasive subspecies is at present largely in separate areas in Australia and it is predicted this situation will continue because of their differing climatic preferences, morphology and regeneration from

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1984.tb01348.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractDisplacement ofAcacia longifoliaon coastal dunes in New South Wales by the invasive speciesChrysanthemoides moniliferamay be linked to the greater competitiveness by the latter in the seedling stage, as demonstrated in pot experiments. This occurs despite a lower chlorophyll concentration in shoots ofC. moniliferawhich leads to a lower assimilation rate per unit leaf area and lower carbohydrate concentrations. However, this assimilate is spread over a greater total leaf area. Such a strategy associated with‘quantity’may thus be more important than leaf‘quality’in terms of competitiveness. InA. longifolia,the production of higher quality‘leaves’but of lower total area may be well‐suited in the often sparse native populations found in sand dunes, but appears disadvantageous when seedlings ofC. moniliferaalso co‐exist.The competitive advantage ofC. moniliferaoverA. longifoliais reduced but not reversed under water stress. Under severe stress, mortality ofC. moniliferais greater than that ofA. longifoliain monocultures but mortality of both species is similar in mixtures. The reason appears to be thatC. moniliferatranspires more water per plant even though its rate of transpiration per unit leaf area is reduced under water stress because of early stomatal closure. In mixtures, faster root growth ofC. moniliferaensures faster uptake of the available soil water, thus minimizing the inherent advantage inA. longifoliaof its lower water use and gre

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1984.tb01349.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractThe hypothetical correlation between temporal and spatial patterning in Landsat data and temporal and spatial heterogeneity required by persistent small populations of animals vulnerable to extinction has been tested by a biological survey and then applied to the design of a biological reserve. Vulnerable animals were associated with gradual gradients (ecoclines) in multi‐temporal texture transforms of Landsat imagery. Potential pest species and sites without fauna were associated with textureless areas and with abrupt boundaries. An area 150 000 km2of the Tanami Desert in central Australia was mapped. The data were utilized to order biological reserve prioritie

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1984.tb01350.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractAn account is given of the flower ofEchium plantagineumin south‐eastern Australia, including stages and timing of flowering, behaviour of raindrops in the flower and aspects of floral microclimate.The concentration of nectar solutes varied with time and site, with means varying from 2 to 62% (as g sucrose/100 g solution). There was a significant negative correlation between nectar solute concentration and ambient relative humidity: the drier the air, the more concentrated the nectar.Rates of nectar secretion per flower varied with the bagging method, with long‐term bagging reducing net secretion rates, possibly because of re‐absorption. Rates varied with time, day and site, with a temporal pattern of change suggesting a link between rates of photosynthesis and secretion. Maximum nectar secretion rates in short‐term bagging experiments were ca. 300 μg sugar/flower/hr (equivalent to>2 mglflower/24 hr).Secretion rate was correlated with flower density. As flower density increased, secretion rate per flower decreased; rate of sugar production per unit area increased relatively more slowly than flower density.E. plantagineumcould produce>500 mg sugar/m2/day.Honeybees foraged onE. plantagineumonly at ambient air temperatures above ca. 17°C unless irradiance exceeded ca. 750 W m‐2. Foragers collected nectar or pollen alone, or both, with the type of visit significantly correlated with nectar solute concentration. Below 35% (as g sucrose/100 g solution) most bees took pollen only; above 40%, most took nectar.Mean standing crop of nectar was generally<100 μg/flower when most bees were taking nectar, but could exceed 1000 μg/flower when bees were absent or foraging mainly for pollen. Honeybees did not always remove all nectar from flowers they probed. Reabsorption of residual nectar may augment the following da

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1984.tb01351.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractThe growth characteristics of the larvae of the major members of a necrophagous fly guild in Tasmania(Lucilia cuprina, Calliphora stygia, Calliphora vicinaandCalliphora hilli)were measured to assess their competitive ability. The measurements were made at temperatures between 10 and 45°C, to cover the range of temperatures that would be encountered by larvae in carrion or myiasis under field conditions.The characteristics measured were net production and respiration. The indices K2i(instantaneous growth efficiency), K2c(cumulated growth efficiency) and Mi(instantaneous cost of maintenance) were calculated. Generally K2cand K2iare highest and Milowest at 25°C for all the species. A sinusoidal response in K2c, K2iand Miagainst temperature is seen forL. cuprina, C. stygiaandC. vicina.This response is‘cold’adapted in theCalliphoraspecies and‘warm’adapted inL. cuprina.Egg size, egg caloric density and the energy content of the eggs are discussed in relation to the‘fitness’and reproductive strategies of the four species.The thermal tolerance range ofL. cuprinadetermined here suggests that carrion may provide a significant number of this fly particularly in areas whereChrysomyaspp. do not occur, and in large carcasses where temperatures

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1984.tb01352.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractRates of development and pupal weights were compared between seven field populations and two laboratory strains ofTribolium castaneum.Rates of development did not differ significantly between field populations, but pupal weights did vary. Laboratory strains were both slower to develop and heavier than the field populations. The data support the hypothesis that field populations undergo selection for fast development in transient habitats. The findings are discussed in the context ofrandKselection in field populations and laboratory cultures.

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1984.tb01353.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Interactions among animals and algae in an intertidal zone dominated by barnacles Peter JernakoffAn investigation of ecological relationships — experimental studies of the interactions between the sowthistle aphid,Hyperomyzus lactucaeand its parasite,Aphidus sonchiLiu Shu‐S

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1984.tb01354.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY