摘要:

AbstractBoth birds and insects visit yellow flower heads ofBanksia ilicifoliarather than those in the pink or red phases. Birds carry most pollen. Substantial nectar and pollen rewards are present only in the yellow phase. The timing of flower colour change also corresponds to a decline in viability of presented pollen and stigma receptivity. Colour change is age‐dependent rather than pollinator‐induced. Bird visits to yellow or red heads are essentially determined by the availability of nectar in each rather than differences in their visibility. Fruit set is negligible in the absence of pollinators but still<1% in their presence.Banksia ilicifoliahas the smallest heads and is the most localized of five co‐occurring and partly co‐floweringBanksiaspecies. It is hypothesized that the restriction of flower colour change toB. ilicifoliaincreases the competitiveness of this species: bird visitors are directed to flower heads with abundant nectar, viable pollen and receptive stigmas, foraging and pollination efficiency thereby being enhanced without a marked reduction in long‐distance attractiveness of the tree to potential po

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1988.tb00962.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractShort‐term seed survivorship for several species of the Queensland rainforest was compared in forests and early successional fields, treefall gaps and forest interior, and an array of microhabitats (tree buttresses, logs, forest floor with and without leaf litter cover). Seed survivorship was lower in forest than in field at one site, but equal at another. No differences were found in and out of treefall gaps, in contrast to several other studies. Microsites had little consistent influence on short‐term seed survivorship. A survey of the literature showed no consistent habitat or microhabitat patterns in seed survivors

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1988.tb00963.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractPattern analysis of stems>10 cm d.b.h. on 514 one‐tenth ha quadrats showed thatCallitris intratropicahas a clumped distribution throughout the more uniformly distributedEucalyptusforests at Murgenella in Northwest Arnhem Land.Callitrisclumps are typically located on sites with sandy soils. Eucalypts occur withinCallitrisclumps.Fire suppression over the past 18 years has allowed someC. intratropicato establish onEucalyptusforest sites with fine textured soils It is argued that distribution ofCallitrispreceding fire management was controlled by the interactive effects of fire, soils and understorey vegetation. High grass fuel loads (and thus intense fires), and competition are thought to have previously limited establishment ofC intratropicaon fine textured soils. Early dry season burning by Aboriginals may also have been important in limiting fire intensities and accumulation of fuel inCallitrisstands. Dry electrical storms commonly cause fires prior to the summer rains. Such wildfires did not completely kill stands ofCallitrissaplings or trees at Murgenella. Survivors were found to be significantly bigger and to have thicker bark than the dead stems. Sapling size is related to age and density, thus fire may be an important mechanism in thinning heavily stocked stands.The continuous regeneration ofCallitrisandEucalyptusis in marked contrast to the inhibition ofPinus caribaearecruitment following fire protection in the monsoonal neotropics. The lack of seral tree species in northern Australia suggests an equilibrium between forest distribution and the physical environmen

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1988.tb00964.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractTriodia basedowiiseeds were found almost exclusively withinTriodiahummocks, both in the centres and under the edges. Averaged over the whole ground surface, live seed densities in soil and litter were 85‐263 m−2in stands which had been burnt 9 and>35 years previously. These live seeds comprised only 56% of all filled grains, and in turn filled grains were present in only about 6% of all fruits. Thus>4% of fruits contained live seeds. A site burnt 1 year previously had about 35 live seeds m−2still ungerminated, but at sites burnt 3 years previously none of the pre‐fire seed bank was alive. After fire, juvenile plants were found predominantly around the edges of where hummocks had been before the fire, suggesting that seeds survive fires better around th

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1988.tb00965.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractTo investigate factors affecting the ability of introduced species to invade natural communities in the Western Australian wheatbelt, five communities were examined within a nature reserve near Kellerberrin. Transect studies indicated that introduced annuals were more abundant in woodland than in shrub communities, despite an input of introduced seed into all communities. The response of native and introduced annuals to soil disturbance and fertilizer addition was examined. Small areas were disturbed and/or provided with fertilizer prior to addition of seed of introduced annuals. In most communities, the introduced species used (Avena fatuaandUrsinia anthemoides) established well only where the soil had been disturbed, but their growth was increased greatly when fertilizer was also added. Establishment and growth of other introduced species also increased where nutrient addition and soil disturbance were combined. Growth of several native annuals increased greatly with fertilizer addition, but showed little response to disturbance. Fertilizer addition also significantly increased the number of native species present in most communities. This indicates that growth of both native and introduced species is limited by nutrient availability in these communities, but also that introduced species respond more to a combination of nutrient addition and soil disturbance.

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1988.tb00966.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractHigh‐density (dense) and low‐density (sparse) plots were set up in naturally sown monospecific stands ofBanksia ericifoliain coastal heath, 3 years after fire. This was done both in high‐growth and low‐growth areas. Plant mortality was recorded quarterly, and two harvests were made at 6 and 9 years to sample growth. Density‐independent mortality at an exponential rate was observed in the low‐growth treatments at both densities, and in the high‐growth sparse treatment. Growth level affected mortality, with the half‐life of populations in the high‐growth sparse plots being double that of populations in the low‐growth plots. Density‐dependent mortality (self‐thinning) was seen only in the high‐growth dense plots. Seasonal effects on mortality were slight; maximum mortality was observed in the spring‐summer period in plots subject to density‐independent mortality, and in the winter‐spring quarter in plots that had self‐thinned. Yields in the high‐growth plots and the low‐growth dense plots were high for heath vegetation. The self‐thinning populations did not exceed White's (1985) upper boundary for thinning lines of log intercept (K) = 5 on standardized axes. The data suggested a log intercept value in the range 4.8–4.9 in the high‐growth stands assuming a thinning‐line slope of – 1.5.Banksia ericifolia(a large shrub/small tree) has a high mean plant weight per given thinning density compared with trees, where an upper limit of logK= .4 has been suggested by White (1985). The volume of canopy space per plant inB. ericifoliais not unusual compared with other species. The amount of biomass packed into a given volume of canopy space was high in thisBanksia, achieved by having leaves with a low ratio of area to weight (specific leaf area, SLA). For given values of density, leaf area index and proportion of shoot as leaf, plants with a low SLA will be several times heavier than plants with a high SLA. This achieves a high biomass to volume ratio without an erectophile canopy and may explain the hig

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1988.tb00967.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractVarious aspects of the pollination biology of the alpine flora of Kosciusko National Park, NSW, were examined from late December 1983 until the end of March 1984, including flowering phenology, corolla tube lengths, flower colour, ultraviolet reflectance patterns, visitation rates to the flowers and proboscis lengths of the flower‐visiting insects. An average of 5.3 species flowered in each of 13, 2 m×2 m montane plots and 5.6 species in the 13 alpine plots. The maximum number in flower simultaneously averaged 4.1 species in the montane and 3.3 in the alpine plots; flowering peaked in mid‐January, Corolla tube lengths of the flora averaged 1.73 mm.The most common floral colour was white or predominantly white (40 species), followed by yellow (14 species). Only six of the 38 species (16%) examined had some type of reflectance pattern; the remaining species all absobed ultraviolet.Flies appeared to be the major pollinators. The insects collected in the study area comprised 60 species of Diptera, 33 species of Hymenoptera, and several species each of Lepidoptera and Coleoptera. On average, 14.4% of flowers watched during 379 observation periods (10 min each) were visited. On average, each plant species was visited by 6.4 species of flies, 2.4 species of bees, wasps or sawflies, one species of butterfly or moth and 0.3 species of beetles. Visitation rates increased over the growing season, and were significantly affected by ambient temperature (positively), light levels (positively) and wind speed (negatively).The maximum proboscis length for the 25 most common species of bees was 2.76 mm, but 18 of 51 species of flies had proboscis lengths longer than this. The mean proboscis length for all 25 species of bees was 1.68 mm, and for 51 species of flies was 2.31 mm. Proboscis lengths for flies were positively correlated with the average corolla length for the plant species they visited. For bees, however, the range in proboscis lengths was relatively small and did not show this pattern.There appear to be significant differences between the plant‐pollinator community of alpine Australia and other alpine areas where bumblebees are common pollinators. These differences include shorter proboscis and corolla tube lengths, and perhaps an increased diversity and significance of flies as polli

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1988.tb00968.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractExcept when sown into non‐wetting soils, buried seeds (achenes) ofChondrilla junceagerminated readily following summer rainfall events of less than 10 mm. Seeds lying on the surface were much less likely to germinate in response to small rainfall events, but were prone to predation by seed‐harvesting ants. Although seedlings were capable of resuming growth following temporary dehydration at the earliest stages of emergence from the pericarp, very few of these were able to establish. Establishment from summer germination was virtually nil.The capacity to germinate at higher temperatures was increased following storage for seeds which had been produced in February and March. However, this was considered to be only a weak expression of a release from relative dormancy, compared to the marked changes in temperature response which occur during the after‐ripening of many winter annuals. Differences in the germination behaviour and persistence of seeds of the narrow‐leafed and broad‐leafed forms ofC. juncea, when evident, were usually slight.On the basis of an analysis of climatic records for 13 wheatbelt sites, obtained over the period for whichC. junceahas been known to occur in Western Australia, it is argued that more than two germinating events could be expected to occur, on average, during the summer months. The relative absence of mechanisms which might confer protection from the effects of unseasonal rainfall, in conjunction with evidence for high levels of seed predation, point to considerable seed losses. Thus the abundance of the species elsewhere in Australia appears to have resulted from its capacity for vegetative reg

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1988.tb00969.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractPollen influx data derived from a sediment core from a small crater lake were related to two population growth models. Doubling times for some tropical rainforest tree taxa, estimated from the models, are 63–165 years for angiosperms and 199–355 years for conifers. These values are generally higher than those for temperate forest trees in the Northern Hemisphere. The results show that fossil pollen data can provide useful information on tree population ecology in tropical ar

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1988.tb00970.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.tb00971.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY