Description:
A slem-galling weevil COT/o/rad,e/us alboeinereus Fiedler 1940 from Argentina is being field released to regulate populations of the weed Parlhenium hysterophorus in Queensland, Australia since 1995. In this paper we report the tissue and metabolic responses in P hyslerophorus in the context of the biology and feeding behaviour of the weevil. C albocinereus induces elliptical galls often on the main shoot axes and rarely on the terminal and axillary mcristems of the host plant. From oviposition through gall maturation, the structure and metabolism of the host-plant tissues. especially at the gall region, change continuously to accommodate pressure inflicted by the feeding larva. The host plant shows re-dirtttion of its vital metabolites to the gall, and to the lTlCtaplasitd cells of nutrition in particular. In mature galls. the pith parenchyma elements tum lignified. Larval feeding fractures the vertical continuity of vascular tissues, which affects the host plant's overall metabolism As the larva tunnels the shoot eolulTVl. it places the frass at the fissured vascular sites. That activity initialcs n«rosis and eventual death of the living eells of the vascular tissue complex. Such a development induces water.logging stress in the gall and the evapotranspirauonal system displays contrasting responses. Pennanenl1y closed Siomatal apertures and abnonnally inflated substomatal chambers indicate that P hYSleropltorus suffers moisture-stress with cecidogenesis. The larval performance triggers moisture inundation in the galled shoot and this appears to be an advantage in using this weevil in the control of P hyslerop/rorus.
Description:
A slem-galling weevil COT/o/rad,e/us alboeinereus Fiedler 1940 from Argentina is being field released to regulate populations of the weed Parlhenium hysterophorus in Queensland, Australia since 1995. In this paper we report the tissue and metabolic responses in P hyslerophorus in the context of the biology and feeding behaviour of the weevil. C albocinereus induces elliptical galls often on the main shoot axes and rarely on the terminal and axillary mcristems of the host plant. From oviposition through gall maturation, the structure and metabolism of the host-plant tissues. especially at the gall region, change continuously to accommodate pressure inflicted by the feeding larva. The host plant shows re-dirtttion of its vital metabolites to the gall, and to the lTlCtaplasitd cells of nutrition in particular. In mature galls. the pith parenchyma elements tum lignified. Larval feeding fractures the vertical continuity of vascular tissues, which affects the host plant's overall metabolism As the larva tunnels the shoot eolulTVl. it places the frass at the fissured vascular sites. That activity initialcs n«rosis and eventual death of the living eells of the vascular tissue complex. Such a development induces water.logging stress in the gall and the evapotranspirauonal system displays contrasting responses. Pennanenl1y closed Siomatal apertures and abnonnally inflated substomatal chambers indicate that P hYSleropltorus suffers moisture-stress with cecidogenesis. The larval performance triggers moisture inundation in the galled shoot and this appears to be an advantage in using this weevil in the control of P hyslerop/rorus.
Description:
During June 1998 a very strong windstorm at the Snowy River National Park ncar Mt Gelantipy caused severe damage to a stand of Eucalyptus delegatensis. Little is known about the impact of windthrow on E. delegatensis and subsequent seedling recruitment. This study was undertaken 4.5 y later 10 examine (i) windthrow damage to E. delegatensis and the understorey Acacia dealbata, (ii) the influence of tree size on the pattern of lree damage, (iii) the undergrowth in the windthrow area compared with that in control plots, and (iv) species composition of the soil-stored seed-bank in windthrow and control plots. We found that high winds toppled virtually all trees regardless of size and species, damaging 99% of the E. delegarensis. In windthrow plots there were 49 seedlings ha- I of E. delegarensis and 2210 ha-I of A. dealbata. No E. delegarensis or A. deafbara seedlings were recorded in the control plots. In the soil seed-bank study five species were recovered from soil samples collected from the control, and six from the windthrow-damaged sites. The canopy species E. delegatensis recruited only from the windthrow site. The exotic Rubus fruticosus was found to be colonising the windthrow site, but was not present in the control site. Results show that E. defegarensis recruitment is very poor in the damaged area, and species colonising within that area are light demanding or early succession species. It is proposed that seedling recruitment in the windthrow sites be accelerated by burning the site and broadcasting E. delega/ensis seed, or transplanting seedlings.
Description:
Green galenia is a South African woody prostrate perennial that was first recorded in Australia in the early 1900s and has since become a serious threat to indigenous temperate grasslands and surrounding agricultural areas. Laboratory and field based experiments were conducted to examine the effect of environmental factors on the germination and viability of green galenia seed. It was shown that green galenia was able to germinate over a broad range of temperatures, but short bursts (5 min) of high temperatures (80 C to 120 C replicating possible exposures to a fire) reduced seed germination. Seed germination was positively favored by light, declined rapidly in darkness, and decreased by >80% at a depth of only 0.5 cm in soil. Water stress greatly reduced seed germination (45% germination at osmotic potentials below -0.2 MPa). Germination was completely inhibited at water potentials of -0.4 to -1.0 MPa. This species is moderately tolerant to salinity, with over 50% of seeds germinating at low levels of salinity (60 mM NaCl), and moderate germination (49%) occurring at 120 mM NaCl, it can germinate well in both alkaline (pH 10-83%) and acidic (pH 4-80%) conditions. The results of this study have contributed to our understanding of the germination and emergence of green galenia, and this will assist in developing tools and strategies for the long term management of this noxious weed in Victoria and other parts of Australia. Nomenclature: Green galenia, Galenia pubescens (Eckl. & Zeyh.) Druce.
Description:
The noxious weed Nassella neesiana is established on a wide range of productive land throughout southeastern Australia. N. neesiana seeds, when mature, are sharp, causing injury to livestock, thus posing a problem in fodder bales. To reduce infestations of agricultural weeds in situ, production of silage from weed-infested pastures is practised as part of integrated weed management (IWM). However, there is little data to demonstrate whether this process is useful to reduce infestations or the harmful properties of N. neesiana. Therefore, the minimum duration of ensilage required to reduce the viability of N. neesiana seeds was investigated, both with and without addition of ensilage inoculants in this process. Also, the decreasing propensity of the seeds to injure livestock, after various times and conditions of ensilage, was assessed. Ensilage inoculant reduced seed germination probability to zero after 35 days. When no inoculant was added, zero viability was achieved after 42 days. A qualitative assessment of the hardness of ensilaged seeds found seed husks were softer (and therefore safer) after 42 days, whether inoculant was used or not. Therefore, we suggest that both the viability of N. neesiana seeds and hardness of seed casings are significantly reduced after 42 days, thereby reducing the risks of seed dispersal and injury to livestock.
Description:
The noxious weed Nassella neesiana is established on a wide range of productive land throughout southeastern Australia. N. neesiana seeds, when mature, are sharp, causing injury to livestock, thus posing a problem in fodder bales. To reduce infestations of agricultural weeds in situ, production of silage from weed-infested pastures is practised as part of integrated weed management (IWM). However, there is little data to demonstrate whether this process is useful to reduce infestations or the harmful properties of N. neesiana. Therefore, the minimum duration of ensilage required to reduce the viability of N. neesiana seeds was investigated, both with and without addition of ensilage inoculants in this process. Also, the decreasing propensity of the seeds to injure livestock, after various times and conditions of ensilage, was assessed. Ensilage inoculant reduced seed germination probability to zero after 35 days. When no inoculant was added, zero viability was achieved after 42 days. A qualitative assessment of the hardness of ensilaged seeds found seed husks were softer (and therefore safer) after 42 days, whether inoculant was used or not. Therefore, we suggest that both the viability of N. neesiana seeds and hardness of seed casings are significantly reduced after 42 days, thereby reducing the risks of seed dispersal and injury to livestock.
Description:
The partenium sumemr rust (puccinia melampodii dietel & holway, uredinals), native to Mexico, is a host-specific and highly damaging pathogen suited tio warmer weather conditions.
Description:
During June 1998, a severe windstorm caused significant damage to a sub-alpine stand of Eucalyptus delegatensis (Myrtaceae) at the Snowy River National Park. In 2002, about 4.5 y after the windstorm, a study documented the effects on E. delegatensis and early understorey succession. In February 2003, wildfire burnt across the windthrow site and we examined the seedling recruitment patterns at windthrow–burn and burn-only sites. Our aim was to document the regeneration of the canopy-dominant E. delegatensis and to confirm that Acacia dealbata is a pioneer species that potentially interferes with or prevents regeneration of E. delegatensis. Permanent transects were established within the windthrow–burn and burn-only sites. The data suggest that the heavily disturbed (mounded) soil at the windthrow site had a strong positive influence on regeneration of both species. By providing favourable growing conditions, the disturbed soil appears to have assisted seedling survival and subsequent growth of the E. delegatensis, despite competition from dense, concurrently established A. dealbata.
Description:
Summary This paper outlines a project that intends to investigate the link between the occurrences of weeds in pasture hay crops and weed seeds in bales. Noxious weed in particular pose a threat to the livelihoods of primary producers in this manner. As an example of a noxious weed, this project will investigate Nassella neesiana, Chilean needle grass. This species is a restricted (noxious) weed that infests roadsides, native grasslands and pastures that may be baled for hay. In Victoria it has the potential to cause significant economic harm to agricultural areas and the trade in fodder and hay. This project aims to develop methods for the detection of weed seeds in hay bales and provide more information about the role of hay machinery in their spread. Later, we will investigate the extent of seed shedding from hay bales during transportation by road. This project will attempt to correlate the percentage cover of N. neesiana prior to harvest with the seed content of bales. Trial core samples from bales indicate that seeds of N. neesiana and other grass species were present. However, a correlation has not yet been established between weed biomass and the seed content of bales.
Description:
The June 1998 a severe windstorm at Snowy River National Park near Mt. Gelantipy caused severe damage to a stand of Eucalyptus delegatensis. Little is known about the impact of windthrow on E. delegatensis and subsequent seedling recruitment. This study was undertaken 4.5 years later to examine (i) the windthrow damage on E. delegatensis and the understorey Acacia dealbata (type of damage, diameter class distribution), (ii) the influence of tree size (diameter at breast height, 1.3m) on pattern of tree damage (snapped/uprooted/ snapped and resprouting) (iii) undergrowth in the windthrow area compared with control plots, (iv) species composition of soil stored seed bank in windthrow damaged plots and control plots. Eleven (25 x 25 m2) plots within damaged areas and five plots within undamaged (control) were selected for study. Tree diameter at 1.3 from the rooting point and type of damage (snapped, uprooted, snapped resprouted, snapped dead) were recorded. To examine seedling recruitment, each 25 x 25 m2 plot was further divided into 1 x 1 m2 sub-plots. Within each sub plot, all E. delegatensis seedlings and their diameters were recorded. Soil seed bank species composition was examined by taking 88 and 40 soil samples from windthrow and control sites respectively. Soil samples were placed in punnets and new recruits were counted and identified. This study showed that, high winds toppled virtually all trees regardless of size and species damaging 99% of E. delegatensis. Seedling recruitment was 49 ha-1 for the canopy species E. delegatensis and 2,210 ha-1 for the sub-canopy species A. dealbata. No E. delegatensis or A. dealbata seedlings were recorded in the control plots. In the soil seed bank study five species were recovered from soil samples collected from the control and six from the windthrow damaged sites. The canopy species E. delegatensis recruited only from the windthrow site. The exotic Rubus fruticosus was found to be colonizing the windthrow site, but was not present in the control site. Results show that E. delegatensis recruitment is very poor in the damaged area and species colonizing within the windthrow damaged area were light-demanding or early succession species. It is proposed that seedling recruitment in the winthrow sites be promoted by burning the site and broadcasting E. delegatensis seed.
Description:
The June 1998 a severe windstorm at Snowy River National Park near Mt. Gelantipy caused severe damage to a stand of Eucalyptus delegatensis. Little is known about the impact of windthrow on E. delegatensis and subsequent seedling recruitment. This study was undertaken 4.5 years later to examine (i) the windthrow damage on E. delegatensis and the understorey Acacia dealbata (type of damage, diameter class distribution), (ii) the influence of tree size (diameter at breast height, 1.3m) on pattern of tree damage (snapped/uprooted/ snapped and resprouting) (iii) undergrowth in the windthrow area compared with control plots, (iv) species composition of soil stored seed bank in windthrow damaged plots and control plots. Eleven (25 x 25 m2) plots within damaged areas and five plots within undamaged (control) were selected for study. Tree diameter at 1.3 from the rooting point and type of damage (snapped, uprooted, snapped resprouted, snapped dead) were recorded. To examine seedling recruitment, each 25 x 25 m2 plot was further divided into 1 x 1 m2 sub-plots. Within each sub plot, all E. delegatensis seedlings and their diameters were recorded. Soil seed bank species composition was examined by taking 88 and 40 soil samples from windthrow and control sites respectively. Soil samples were placed in punnets and new recruits were counted and identified. This study showed that, high winds toppled virtually all trees regardless of size and species damaging 99% of E. delegatensis. Seedling recruitment was 49 ha-1 for the canopy species E. delegatensis and 2,210 ha-1 for the sub-canopy species A. dealbata. No E. delegatensis or A. dealbata seedlings were recorded in the control plots. In the soil seed bank study five species were recovered from soil samples collected from the control and six from the windthrow damaged sites. The canopy species E. delegatensis recruited only from the windthrow site. The exotic Rubus fruticosus was found to be colonizing the windthrow site, but was not present in the control site. Results show that E. delegatensis recruitment is very poor in the damaged area and species colonizing within the windthrow damaged area were light-demanding or early succession species. It is proposed that seedling recruitment in the winthrow sites be promoted by burning the site and broadcasting E. delegatensis seed.
Description:
Human activity has, in the recent past resulted in substantial changes in land cover, ecosystem health, and the ability of affected ecosystems to return to their original state. This necessitates further human intervention to recreate the systems functions than the present. Earlier restoration activities have not been documented extensively. This hinders our efforts to identify approaches that might support further work. "From abstract"
Description:
Laboratory experiments were carried out to determine the effect of several environmental factors on seed germination of feather fingergrass, one of the most significant emerging weeds in warm regions of the world. Seed germination occurred over a broad range of temperatures (17/7, 25/10, and 30/20 C), but germination being highest at alternating temperatures of 30/20 C under both 12 h light/12 h dark and 24 h dark conditions. Although seed germination was favored by light, some seeds were capable of germinating in the dark. Increasing salt stress decreased seed germination until complete inhibition was reached at 250-mM sodium chloride. Germination decreased from 64 to 0.7% as osmotic potential decreased from 0 to -0.4 MPa, and was completely inhibited at -0.6 MPa. Higher seed germination (>73%) was observed in the range of pH 6.4 to 8 than the other tested pH levels. Heat shock had a significant effect on seed germination. Germination of seeds placed at 130 C for 5 min was completely inhibited for both dry and presoaked seeds. The results of this study will help to develop protocols for managing feather fingergrass, and to thus avoid its establishment as a troublesome weed in economically important cropping regions.
Description:
Lachnagrostis filiformis (frost) Trin, commonly known as fairly grass, is a native grass that has recently become a major concern for rural communities.
Description:
Reliable on-ground information on groundwater (GW) hydraulic heterogeneity is required to determine flow direction and quantities, but its experimental characterization is difficult because of the complexities associated with the interaction involving the temporal changes in space modified by regolith stratigraphy. The impact of the aforementioned variables, particularly stratigraphy in a 51 m thick highly weathered basaltic regolith in the northeast humid tropics of Queensland, Australia, on flow gradients and directions was investigated in this study. Regolith cores at 1 m increments indicated that there were 3 different major strata. The temporal changes in water table, hydraulic- and pressure- heads, and solute concentrations in space indicated the top 51 m aquifer was contiguous, dynamic and hydraulically differentiated into three segments which approximately corresponded with the regolith strata. The lateralflow and solute transport from each aquifer segment was controlled by depth to water table, the number of regolith layers the segment covered, and the solute concentration.
Description:
Hollows are an important, but rare, resource for several native vertebrate species in the box-ironbark forests of central Victoria. A study assessed the external features of trees from burnt and unburnt areas of forest to determine the influence of fire on hollow formation in these forests. Significantly greater proportions of trees in burnt areas has scars than trees in unburnt areas. Fire had less influence on the number of small, medium, large and very large dead branches/branch stubs than tree diameter. Similarly, tree size rather than fire was a major determinant in the occurrence of hollows. The greater number of scars in burnt trees might eventually lead to a difference in hollow numbers between burnt and unburnt trees (A).
Description:
Hollows are an important, but rare, resource for several native vertebrate species in the box-ironbark forests of central Victoria. A study assessed the external features of trees from burnt and unburnt areas of forest to determine the influence of fire on hollow formation in these forests. Significantly greater proportions of trees in burnt areas has scars than trees in unburnt areas. Fire had less influence on the number of small, medium, large and very large dead branches/branch stubs than tree diameter. Similarly, tree size rather than fire was a major determinant in the occurrence of hollows. The greater number of scars in burnt trees might eventually lead to a difference in hollow numbers between burnt and unburnt trees (A).
Description:
Annual grasses are important components of vegetation, especially where perennial grasses have declined from overgrazing. Panicum laevinode is an annual grass that occurs in large numbers in grassy Eucalyptus victrix L. Johnson and K. Hill coolibah woodland in Pilbara, Western Australia. Little is known about the seed germination pattern and requirements of this grass. Our aim was to examine the effect of heat pre-treatment on seed germination of P. laevinode. Only 12% germination was observed from seeds pre-treated at 60oC for periods ranging from 1 to 8 weeks. However seed viability study showed that 61.5% and 71.5% of seeds were viable from 3 and 17 months respectively. Germination study did not reflect results of the viability test.
Description:
The main objectives of this study were to investigate: (i) the distribution of exotic plant species in flooded and control (unflooded) areas in relation to a 1997 episodic flooding event and (ii) the influence of grazing in flooded and unflooded open and fenced plots on wed colonization.