摘要:

AbstractExperimental introductions of the annual Emex australis were made in two consecutive years at each of three sites in southern Western Australia. Introductions differed in relation to the numbers of seeds involved (n = 1, 2,4, 8 or 16) and whether seeds were buried or surface sown. Fates of the introductions were monitored for 30 months. Successful introductions were defined as those where at least one viable seed was produced. Generally, introduction success increased with the number of seeds involved and with seed burial. However, major departures from these trends were observed at one site in the second set of introductions.Most recruitment and most seed production occurred during the first growing season following introduction. The number of seeds produced over the 30 month period usually increased with increasing size of introduction. The year of introduction was a highly significant determinant of seed production. Since seedling mortality was low throughout this study, processes affecting seed burial and seed mortality are considered to be the major stochastic factors that influence the colonizing success of Emex australis.

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1994.tb01546.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abstractmall‐scale (within‐shore) and broad‐scale (among‐shore) patterns of distribution, abundance and size structure of Nodilittorina pyramidalis were measured on a number of shores in New South Wales. This species showed significant patchiness in distribution and size structure. The mean density and mean shell length of snails differed among patches of shore only a few metres apart, among different heights on the shore and from shore to shore. Differences in densities appeared to be strongly correlated to the distribution of particular microhabitats, especially cracks, crevices and pits within the rock surface. This relationship and the presence or absence of these microhabitats appeared to determine the patterns of distribution of this species within and among different shores. The sizes of snails were not correlated with densities of Nodilittorina nor with the coexisting species, Littorina unifasciata, in the populations examined. Processes influencing the distribution and abundance of Nodilittorina were not investigated, but the patterns of distribution found on these shores suggest that recruitment was limited to areas of topographic complexity, ft also seems likely that limited dispersal by the adult snails retain them within restricted patches on th

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1994.tb01547.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractThe effects of overstorey, type of site, seedbed, seeding date and seed harvesting by vertebrates and invertebrates on the emergence of Eucalyptus marginata (jarrah) seedlings were studied experimentally in the northern jarrah forest of Western Australia. Seed harvesting by small vertebrates substantially reduced emergence, whereas invertebrates only slightly reduced emergence. Ninety per cent of seed was removed within 1 day when it was on the soil surface and in the open, whereas seed removal was insignificant when the seed was covered by soil. Vertebrates harvested seed more effectively when the understorey and litter were removed and the seed was more visible on the soil surface. Seed harvesting by small vertebrates had less impact on a site where there had been bauxite mining, possibly because the surrounding area was being revegetated with large numbers of seed and the area afforded poor cover for vertebrates. Emergence was less where the overstorey was removed compared to where it was retained, and on the rehabilitated bauxite mined site compared to the forest sites. There was no difference in emergence between the low and high quality forest sites and so the emergence phase could not fully explain the variation in abundance off. marginata seedlings on different quality sites. Post emergence events are likely to be important in explaining this difference between low and high quality sites.

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1994.tb01548.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractThe effects of overstorey, site, seedbed, seedling density, application of fertilizer and grazing on mortality of Eucalyptus marginata (jarrah) seedlings were studied experimentally in the northern jarrah forest of Western Australia. Rainfall, soil temperature, soil water deficits, leaf water potentials and photosynthetically active radiation (PAR) were monitored. Seedlings on sites with the overstorey removed experienced significantly higher soil temperatures for 9 months of the year (of up to 6°C), smaller soil and leaf water deficits during the dry season (minimum predawn leaf water potentials of ‐0.5 MPa compared to ‐1.6 MPa) and higher intensities of PAR (maximum values of 1900 umol m−2s1compared to 900 umol m−2s−1), compared to seedlings on sites with the overstorey retained. Mortality off. marginata seedlings was greater on sites where the overstorey was retained compared to where the overstorey was removed, on low quality sites than high quality sites, and on undisturbed and lightly disturbed seedbeds compared to heavily disturbed seedbeds. Seedling density, application of fertilizer and grazing by vertebrates did not have a significant effect on percentage mortality. Most of the mortality occurred as water deficits developed in late spring and summer and was attributed to these water deficits. Some mortality that occurred prior to the development of substantial water deficits was probably caused by pathogenic fungi, We conclude that mortality of E. marginata seedlings in the northern jarrah forest of Western Australia can be minimized by reducing the density of the overstorey and by seeding into a seedbed that has had litter and groundcover removed and the soil

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1994.tb01549.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractFor demographic models of resprouting species in relation to fire regimes, spatially separated populations of different ages are usually treated as a chronosequence, and the average behaviour of these populations is used as the estimate of the generalized behaviour of a single population through time. Using the data of Bradstock (1990), we examine the way in which the between‐population variability affects the demographic parameters for Banksia serrata (Proteaceae) and thus assess whether the estimates of the shortest inter‐fire interval necessary to maintain a stable population size under low and high intensity fires are robust to variation in these parameters. The range of our estimates compares well to the average estimate of Bradstock (1990) for high intensity fires, but not for low intensity fires. However the relevant demographic parameters appear to vary more between populations than they do as a result of the length of the inter‐fire intervals, and the specific demographic model discussed here may have only local applic

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1994.tb01550.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1994.tb01551.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Book reviewed in this article:Behavioural Ecology: An Evolutionary Approach, 3rd ednEdited by J. R. Krebs and N. B. DaviesField Guide to Victoria's Native Grasslands: Native Plants of Victorian Lowland PlainsN. H. Scarlett, S. J. Wallbrink and K. McDougallDasycladales: An Illustrated Monograph of a Fascinating Algal OrderS. Berger and M. J. Kaever

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1994.tb01552.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY