Catalogue Search | MBRL
Are you sure you want to remove the book from the shelf?
{{itemTitle}}
301
result(s) for
"Groves, R. H"
Sort by:
Plant-animal interactions in Mediterranean-type ecosystems
This volume comprises invited contributions on important aspects of plant-animal interactions in Mediterranean-type ecosystems, which was the subject of the Sixth International Conference on Mediterranean Climate Ecosystems, held in Crete (Greece), from September 23 to 27, 1991. The subject of plant-animal interactions is fundamental to an understanding of the structure and the function of the Mediterranean-type ecosystems and their rational management.
Book
The Comparative Demography of the Pasture Weed Echium plantagineum between Its Native and Invaded Ranges
1. Echium plantagineum is native to the western Mediterranean Basin, where it is a common, but not dominant, component of species-rich annual grasslands. Since its introduction into Australia, E. plantagineum has spread to infest vast areas of predominantly agricultural land in south-east and south-west Australia, where it can be the dominant pasture species. 2. To unravel the ecological factors responsible for the high population abundance of E. plantagineum in Australia, its demography was compared between sites in the invaded and native ranges. Demographic parameters of E. plantagineum populations were estimated at a site near Canberra in south-eastern Australia, and at a site near Evora in southern Portugal. Identical factorial experiments were set up at each site with treatment combinations of the presence or absence of grazing and pasture competition. 3. The recruitment, survival, fecundity and seed bank dynamics of E. plantagineum populations were measured for each of the treatment combinations over 2 years at each site. These data allowed the estimation of demographic parameters describing the proportion of E. plantagineum individuals moving from one life-cycle stage to the next. 4. Seedling establishment fractions were two to five times greater at Canberra than at Evora, and seed bank incorporation rates were three times greater at Canberra than Evora. These demographic differences were those most likely to play an important role in the greater abundance of E. plantagineum in Australia compared with Mediterranean Europe. Neither seed bank survival rates nor seed production differed between populations at Canberra and Evora, while seedling survival rates were always lower at Canberra than at Evora. 5. Neither grazing nor pasture competition limited the seed production or seedling survival of E. plantagineum populations at Evora more than at Canberra. 6. An effective approach for the control of E. plantagineum in Australia may thus be through the reduction of the seedling establishment fraction. This may be achieved by maintaining significant pasture vegetation cover and reducing the available space for E. plantagineum establishment during autumn.
Journal Article
Are some weeds sleeping? Some concepts and reasons
Issue Title: Special Issue: Plant Breeding and Crop Domestication as Sources of New Invasive Species Sleeper weeds, a relatively new concept, are defined as a sub-group of invasive plant species for which their population sizes are known to have increased significantly more than 50 years after they became naturalized. The invasions of the European herb Hieracium pilosella into New Zealand, the northeast Asian Fallopia japonica and the Sicilian Senecio squalidus into Britain are presented as well-documented examples of sleeper weeds. While the concept of sleeper weeds has gained some acceptance with weed managers, its application remains a retrospective activity at present. Genetic factors, environmental suitability and anthropogenic disturbance are discussed as they affect sleeper weed status. Accurate botanical records for invasive species over long periods of time are relatively rare and limit documentation of the phenomenon. Some mathematical and ecological problems remain with the concept and its wider application to weed invasion, including the adequacy of the species level for determining sleeper weed status in genetically diverse and widely distributed groups of invasive plants.[PUBLICATION ABSTRACT]
Journal Article
Keynote Address: Research on Bitou Bush and Boneseed - a Work in Progress
In this overview of research on the two environmental weeds bitou bush (Chrysanthemoides monilifera subsp. rotundata (DC.) T.Norl.) and boneseed (C.m. subsp. monilifera (L.) Norl.), I list some of the more significant milestones in previous research as I perceive them before assessing the effectiveness of some present research. Throughout, I emphasize the importance of understanding the ecology of these two subspecies in southern Africa (their region of origin), especially as it relates to their management in southern Australia using biological agents. Further quantification of the impacts of bitou bush and boneseed in reducing native biodiversity will be necessary information for the future, especially for boneseed. For more effective management of the weeds, it will be necessary to continue to exclude entry to Australia and New Zealand of the other four subspecies of Chrysanthemoides monilifera known from southern Africa. An optimal combination of agents for biological control of boneseed in southern Australia and New Zealand is also called for, as is the smarter re-vegetation of areas on which bitou bush and boneseed have been weakened by on-going management. The positive roles of bitou bush and boneseed in stabilizing dunes and in providing early winter food for some migrating native birds will become more significant as these re-vegetation programs progress. Other impacts, either positive or neutral, on different groups of species and ecological processes must also be addressed before an integrated management system can be formulated to further reduce the negative impacts on coastal ecosystems of these two weeds of Australasian significance.
Conference Proceeding
The biology of Australian weeds - a short history of the series
The series on the Biology of Australian Weeds has been published over the last 35 years and, in this issue, is now at its 63rd number. As editors, we review its history over this period, list the bibliographic details of all weed species covered so far and request further contributions to the series. From an assessment of the contributions to date, based on a categorization of growth form and earlier published reviews, contributions on some of the grass weeds of high national significance to Australian ecosystems are a notable deficiency currently in the series' coverage.
Journal Article
Seed Population Dynamics of Onopordum Over 1 Year in Southern New South Wales
1. Seed input, changes in the seed bank and seedling recruitment of Onopordum were monitored over 1 year at three contrasting sites (pasture, oat crop and hillside) within an 80-hectare paddock at Galong, New South Wales, about 100 km NW of Canberra. Each site was c. 2000 m2. Time constraints precluded a longer study and repetition of the sampling procedures at similar sites in other areas. 2. In the pasture there were few Onopordum plants but a seed bank of c. 5000 seeds m-2. During the year the seed bank decreased by more than half, but the most dormant component remained constant at c. 800 seeds m-2. 3. In an oat crop nearby there were no flowering Onopordum plants and there was no direct seed input. Nevertheless, the seed bank of c. 700 seeds m-2did not decrease. 4. At the third site, a grazed hillside, Onopordum density was high (19 plants m-2). The seed input of 1788 seeds m-2caused a temporary small increase in the seed bank in summer but there was no change over the 1-year period either in the total seed bank (c. 3000 seeds m-2) or in its most dormant component (c. 750 seeds m-2). 5. Seedlings appeared in all seasons, invariably after rain. More than 95% of seedlings appeared in late summer or autumn, but different management practices changed the pattern of winter establishment. 6. For ecological studies of weeds, the population dynamics of the seeds in the soil and of the plants above ground are equally significant. This study shows that the existence of a small pool of labile seeds (c. 15% minimum) in the seed bank that can be recruited opportunistically, together with a large, strongly persistent component, will make any form of short-term control difficult.
Journal Article
Physiological determinants of growth rate in response to phosphorus supply in wild and cultivated Hordeum species
Under favorable nutrition, accessions of the weedy barleygrass (Hordeum leporinum and H. glaucum) had a higher relative growth rate (RGR) than did accessions of cultivated barley (H. vulgare) or its wild progenitor (H. spontaneum). RGR was not positively correlated with the presumed level of soil fertility at the collection site of an accession either within or among species. RGR was reduced more strongly by low-P supply in the progenitor than in the crop or weed, indicating that selection of cultivars to grow in fertile soils had not reduced their potential to grow effectively under low-P conditions. Seed and embryo masses were more important than RGR in determining plant size. Relative differences among accessions in plant size declined with time, because (1) accessions with small seeds had a higher RGR, and (2) RGR of large-seeded accessions declined with time. Absolute growth rate correlated positively with leaf area and negatively with photosynthetic rate per unit leaf area. Under favorable nutrition, maximum photosynthetic rate correlated negatively with leaf length and therefore was higher in the weeds than in the crop or progenitor accessions. P absorption potential did not differ consistently among species but generally increased in response to P stress. Cultivars produced a few tall tillers, whereas weeds and progenitors produced many small tillers. The cultivar had a larger proportion of reproductive tillers, allocated a larger proportion of biomass to grain, and produced larger grains than did the weedy accession. By contrast, the weed began maturing seeds sooner, produced more reproductive tillers, and produced more grains per ear and per plant than did the cultivar. The study suggests two major conclusions: (1) A low RGR is not an adaptation to low P supply in annual Hordeum species. (2) Seed size is the major determinant of early plant size between accessions in these Hordeum species under favorable nutrition. However, large seed size indirectly results in a low RGR because of the inverse relationship between plant size and RGR and results in a low photosynthetic rate because of the inverse relationship between leaf size and photosynthesis.
Journal Article
Competition and relative yield: estimation and interpretation at different densities and under various nutrient concentrations using Silybum marianum and Cirsium vulgare
(1) The role of the yield-density relationship in determining the choice of an additive or substitutive experimental design for competition experiments is examined, with particular reference to the design of multispecies experiments. A competition experiment between two thistle species Silybum marianum and Cirsium vulgaris at five density levels and six nutrient concentrations is described. (2) The design allows the influence of density and nutrient concentration on the relative yield in mixture compared with monoculture (RY) of the two species (as estimated from a substitutive design of N/2 plants in mixture) to be examined, and compared with that estimated from an additive design of N plants in mixture, where N is number of plants in monoculture. (3) Yields of the two species in monoculture show similar significant responses to both nutrient concentration and density: maximum yield occurs at a nutrient concentration four times standard Hoagland, and response to density is asymptotic. S. marianum has similar performance in mixture while C. vulgare yields are markedly reduced. Nutrient concentration has a significant influence on the RY of both species. A clear influence of density is only apparent at extremely high nutrient concentrations. (4) Acceptance of an asymptotic yield-density function implies that RY values between 0.5 and 1.0 cannot be interpreted unambiguously as being due to competition in substitutive experiments. Analysis of the substitutive design for S. marianum gives RY between 0.5 and 1.0, which cannot be interpreted as due to competition from C. vulgare. The additive design provides no evidence for such a competitive effect. RY values for C. vulgare are less than 0.5 in both designs indicating a competitive effect by S. marianum. (5) Choice of substitutive or additive design depends on knowledge of the yield-density function. Unequivocal results require a range of density combinations to be included in the design.
Journal Article
Competition in Mixtures of Susceptible and Resistant Genotypes of Chondrilla juncea Differentially Infected with Rust
Plants of two genotypes of Chondrilla juncea (skeleton weed), one susceptible to and the other resistant to one isolate of the rust Puccinia chondrillina, were grown as pure and mixed populations both in the presence and absence of rust. Weights of individual plants were obtained at two harvests, one when the plants were rosettes and the other when flowering had begun. Distributions of plant weights of each genotype became progressively more positively skewed with time, with rust infection of plants of the susceptible genotype and with increasing competition between plants of both genotypes. The results show that genetic differences may be an important factor in determining which individuals become dominant or are suppressed in competing mixtures, and that differential disease pressure may alter dominance of individuals in plant populations.
Journal Article