Letteratura scientifica selezionata sul tema "Arid regions ecology - New South Wales"

Surveys for juvenile Mythimna convecta throughout the agricultural and arid regions of eastern Australia were conducted from 1986 to 1989. Armyworm populations north of 33 degrees S were generally dominated by M. convecta, and further south by Persectania ewingii. M. convecta was most widely distributed in spring. Incidence during autumn and winter ranged from very low in Victoria to high in northern New South Wales and southern Queensland. Summer infestations were found mostly on the south-east coast where favourable habitats were abundant. Colonised habitats included extremely arid regions, where small numbers of larvae were associated with grasses in temporary watercourses, and the higher-rainfall, eastern regions. The largest infestations occurred in south-east Queensland and north central and north-east New South Wales, particularly after heavy autumn rains. There appeared to be two generations of M. convecta over the autumn/winter period: the first a synchronised event starting on the autumn rains and the second commencing in June/July and comprising a wide spread in age distribution. The progeny of the winter generation are probably the source of most economic outbreaks. Mythimna convecta larvae were collected from subtropical and temperate grasses. In the former, most larvae were found in tussocks, particularly of Dichanthium sericeum and Chloris truncata, which provided a dense, fine-leaf crown and canopy. After good autumn rainfall and vegetative growth, the wiry-stemmed tussocks, including Astrebla spp. and C. ciliaris, were also common hosts. The temperate grasses, particularly Avena fatua and Hordeum leporinum, were the main winter hosts although the greatest densities were found only in thick swards of growth, particularly those that contained dried grass. Two of the largest surveys, in autumn 1987 and 1988, followed periods of heavy rain and provided strongly contrasting results. The 1987 survey of central and south-west Queensland located no M. convecta larvae, indicating that densities were below detection thresholds. The paucity of larvae was attributed to lack of suitable atmospheric conditions to assist moth immigrations and absence of adequate populations in potential source areas. The 1988 survey revealed a major outbreak of M. convecta larvae in south-east Queensland and northern New South Wales. The area received record rains during early April of that year, and the outbreak probably arose from moth migrations from the east and south-east coast. An outbreak of similar scale occurred after further heavy autumn rains in 1989.

Shot samples of rabbits were taken every eight weeks for two years at four sites in the Southern Tablelands of New South Wales. Age structure differed between sites. The two sites at which rabbits were controlled by poisoning had the youngest age structures; the site where rabbits were not controlled had the the oldest age structure, the lowest density, the least myxomatosis and the highest production of young per female. The seasonal percentages of males in the samples were inversely proportional to the percentages of lactating females. Rabbits that were recovering from myxomatosis had higher infestations of Graphidium strigosum than rabbits that had active myxomatosis or no symptoms. At one of the sites, rabbits with myxomatosis were shot on every sampling occasion. Differences between sites, in duration and timing of reproduction, were very small compared with differences between rabbit populations from climatically different regions of Australasia; annual production of young per female older than six months varied between sites from 23.7 to 26.5 compared with the range of 15-53 for Australasia. The percentage of pregnant females and fertile males was highest in late spring and fell to zero for 1-2 months in summer. This seasonal pattern of reproduction is intermediate between the pattern found in some high-rainfall Australasian environments, where more than 30% of the females are pregnant in all months, and the patterns in arid, semi-arid and subalpine environments, where no females are pregnant for 3-6 months of the year.

Recent erosion in arid regions of western NSW has exposed large areas that are scattered with stone artefacts manufactured by Aboriginal people in prehistory. These exposures offer an opportunity for archaeologists to study the artefacts abandoned by Aboriginal people through time and to compare those artefacts that accumulate in different parts of the landscape. To reconstruct the nature of prehistoric behaviour in the rangelands, two approaches are needed. First, the geomorphological context of the artefacts needs to be considered since exposure of the artefacts is a function of landscape history. Second, large areas (measured in thousands of square metres) and large numbers of artefacts need to be considered if patterns reflecting long-term abandonment behaviour by Aboriginal people are to be identified. This paper reports on the Western New South Wales Archaeological Program (WNSWAP) which was initiated in 1995 to study surface archaeology in the rangelands. Geomorphological studies are combined with artefact analysis using geographic information system software to investigate Aboriginal stone artefact scatters and associated features such as heat retainer hearths, in a landscape context. Results suggest that apparently random scatters of stone artefacts are in fact patterned in ways which inform on prehistoric Aboriginal settlement of the rangelands. Key words: Aboriginal stone artefacts; rangelands; landscape archaeology; geomorphology; GIs

Following a morphometric and cladistic analysis of the Daviesia ulicifolia Andrews group (Chandler and Crisp 1997), a new species, D. sejugata, is described. It occurs disjunctly in eastern Tasmania and southern Yorke Peninsula, South Australia, and is closely related to D. arthropoda F.Muell., differing in a generally more robust habit, thicker fleshy phyllodes, and larger flowers. Even with this species removed from D. ulicifolia, the latter varies considerably over a wide geographic, edaphic and altitudinal range. Daviesia ulicifolia is divided into six subspecies based on distinct phenetic and phylogenetic groups delimited in the earlier study. These are subsp. aridicola (glaucous plants in arid regions), subsp. incarnata (reddish-flowered plants in the Mt Lofty Range, South Australia), subsp. ruscifolia (plants with ovate-acuminate leaves and orange flowers in Victoria and southern New South Wales (NSW), often at high altitude), subsp. stenophylla (a narrow-leaved form in northern NSW and Queensland), subsp. pilligensis (ovate-leaved plants on sandy soil in western NSW), and subsp. ulicifolia (a paraphyletic residual from south-eastern states).

Patterns in the distribution of Australasian species of freshwater aquatic plants were sought, to determine whether vicariance, distance dispersal, local speciation, or a mixture of these could best explain the distribution. The distribution was recorded from 10 regions of Australasia that include sizeable areas of wetland: Papua New Guinea, Cape York Peninsula, south-east Queensland, eastern New South Wales, Victoria, Tasmania, New Zealand, northern Northern Territory, the Kimberley, and south-west Western Australia. Matrices of 553 species by 10 regions, 139 genera by 10 regions, and 56 families by 10 regions were analysed using hierarchical fusion, nearest neighbour and ordination techniques. The results indicate that there are two distinct elements in the aquatic flora, tropical and temperate. The diffuse boundary between these two climatic zones could be interpreted as a barrier in the sense used in definitions of vicariance. There is little effective spread between tropical and temperate areas but, within each of these climatic zones, the species are mobile and many spread reasonably readily between regions, provided suitable habitats and dispersal opportunities are available. Where geographic barriers to distance dispersal have been great then these may become as important as the climatic barrier. This is demonstrated, at least in part, by the differences between some of the generic and species dendrograms. Local speciation (not shown by our PATN analyses because of the endemic species being ignored in them) has been important where some primarily aquatic genera have proliferated when conditions have been suitable. Local speciation has occurred in cosmopolitan aquatic genera that have presumably arrived in regions via long distance dispersal. The significance of bird migration and dispersal patterns are discussed. The aquatic flora of the monsoon tropics has evolved mainly from long distance dispersal but with significant local speciation in some genera such as Nymphoides, Utricularia, Nymphaea and Vallisneria. The pattern of distribution was compared with those recorded from other ecologically defined groups such as the Australian arid and alpine floras.

A morphological study of herbarium and field-collected specimens, using phenetic techniques of agglomerative classification, ordination and minimum spanning trees, and covering the geographic range of the Holly Grevillea, G.�ilicifolia (R.Br.) R.Br. sensu lato, has resulted in the recognition of three species and four subspecies. The taxa are based on leaf form, noted by previous authors to be highly variable between populations. The taxa recognised here are G.�ilicifolia, G.�ilicifolia subsp. ilicifolia (typical, kite-shaped leaf form), G.�ilicifolia subsp. lobata (F.Muell.) T.L.Downing comb. et stat. nov. (oak-shaped leaf form), G.�dilatata (R.Br.) T.L.Downing comb. et stat. nov. (fan-shaped leaf form), G.�angustiloba (F.Muell.) T.L.Downing comb. et stat. nov., G.�angustiloba subsp. angustiloba (narrow-lobed leaf form) and G.�angustiloba subsp. wirregaensis T.L.Downing subsp. nov. (very narrow-lobed leaf form). The rank of subspecies is used where there are some intermediate plants between forms. Grevillea ilicifolia subsp. ilicifolia is the most widespread taxon and occurs in South Australia, western Victoria and in two localities in New South Wales. Grevillea angustiloba subsp. wirregaensis has the most restricted range, occurring in semi-arid regions near Wirrega in South Australia. Grevillea dilatata is largely endemic to Kangaroo Island, South Australia.

The Great Artesian Basin (GAB) underlies a vast, mainly arid, region where most of the indigenous biota are not dependent upon surface water. In contrast, an important minority is dependent on refuges such as mound springs and their associated wetlands. In some parts of the GAB, such as western New South Wales, many springs have either ceased to flow, or are now barely detectable, because the proliferation of artesian waterbores has reduced groundwater pressures. Because of the rarity of species endemic to mound springs, and the damage they have suffered since pastoral settlement, emphasis should be directed towards conservation and possible rejuvenation of these ecosystems. Provision of artificial sources of water allows more widespread grazing by livestock, larger native and feral herbivores, thereby posing threats to native plants and animals that do not use the water. Because of the proliferation of artificial waters and the grazing they allow, terrestrial grazing-sensitive species now appear to be confined to tiny patches in the landscape. Some nature reserves within the GAB retain numerous artificial sources of water. Most of these should be closed over time to reduce negative impacts on grazing-sensitive plants and animals, especially where these species are inadequately protected elsewhere. In those regions where the ratio of artificial to natural waters is still low, consideration should be given to balancing provision of water for livestock with conservation of biological diversity, by maintaining a patchwork of areas remote from water. In regions where the density of artificial waters is high, conservation of biodiversity on freehold and leasehold lands might be enhanced with a mix of approaches accommodating the needs of the biota and the aspirations of landholders, tailored according to land type and condition. Key words: Great Artesian Basin, biological diversity, mound springs, refuges, rare biota, grazing impact, conservation management, groundwater.

The semi-arid to arid Western Division of New South Wales has suffered significant levels of land degradation due to overstocking by domestic animals and rabbits. Three major forms of land degradation are identified, soil erosion, woody weed growth and pasture quality decline. Restoration techniques developed and applied by the New South Wales Soil Conservation Service are presented and discussed. The successful techniques presented are contour furrowing and waterponding for sheet eroded or scalded areas, fire and blade ploughing for woody weed control and grazing management to reverse pasture decline. The lack of knowledge on pasture species responses to grazing management stimuli is highlighted.

An aerial survey of 966,000 km2 of the arid/semi-arid rangelands of Queensland and New South Wales in the winter of 1992 indicated a minimum feral goat population of almost 1 million animals (density 0.97�0.12/km2). Observed density (f standard error) was higher in New South Wales (1.51�0.23/km2) than in Queensland (0.47�0.09/km2).

The effects of roads on landscapes and wildlife and their ecological processes are substantial and represent a major anthropogenic disruption to the natural environment. Current understanding of the impacts of roads for their strategic management is hampered by a lack of information on 1) the influence of the ecosystems on road effects, 2) the effects of roads on higher-order ecosystem responses (populations and communities), and 3) the overall impacts of roads on ecosystems and their wildlife (on both abiotic and biotic ecosystem components). This study used the Silver City Highway in arid New South Wales, Australia, as a model for a typical road in an arid ecosystem to investigate the ecological effects of arid-zone roads and their management. The study examined the spatial variation of soil, vegetation, kangaroo and small mammal variables in relation to the road, explored the factors contributing to these respective spatial variations, investigated the effects of arid-zone road management on vegetation, assessed the fragmentation effect of the arid-zone road on small mammals, and determined the patterns, causes and effects of kangaroo-vehicle collisions. The study revealed that the arid-zone road influenced most of the variables measured, skewed the population demographics of two kangaroo species, and altered the community composition of small mammals, with two small mammal species listed as threatened in NSW and of national significance (Sminthopsis macroura and Leggadina forresti) negatively impacted by the road. Increases in the amount of water along the road edge drove many of the subsequent effects of the arid-zone road as arid-zone flora and fauna are adapted to exploiting limited and patchily distributed resources. However, current arid-zone road management also influenced vegetation quality, microclimates around the road influenced kangaroo densities and small mammal communities, and kangaroo flight behaviour and temporal variations in traffic volume affected roadkill frequency. Together, these results suggest that roads have a high overall ecological impact in arid ecosystems. Conservation managers need to first rank the impacts of arid-zone roads in order of their conservation importance and need for mitigation, and from there, devise relevant informed management frameworks to target these impacts.

The vegetation communities that existed in the semi-arid intermontane basins and gorges of Central Otago prior to human settlement ~750 years B.P. are poorly understood. This is because of a lack of fossil evidence and complex restructuring by anthropogenic factors, especially increased fire frequency, and more recently mammalian grazing. There is also little information regarding the effect of the lost fauna on maintaining and structuring presettlement communities, both in Central Otago and throughout the eastern South Island dryland zone. This study aims to provide a clearer understanding of the functioning of pre-settlement ecosystems in dryland Central Otago, particularly the role of the largest vertebrate herbivores, the moa (Aves: Dinornithiformes), and to explore the implications of the extinct fauna for land conservation management across New Zealand. Late Pleistocene and Holocene vegetation communities of the Central Otago lowlands were reconstructed from plant macrofossils, including seeds, leaves, and wood, excavated from rockshelter, cave, and swamp deposits throughout the region. The macrofossils represent three main vegetation types: late Pleistocene to mid (late?) Holocene basin floor wetland herb associations, Olearia-shrublands surrounding these wetlands, and mid to late Holocene open scrubland and woodland in gorges and on low altitude slopes, dominated by filiramulate Olearia, Coprosma, and Corokia, with abundant lianes (Muehlenbeckia spp. and Rubus spp.) and understorey herbs. Many native tree and shrub species that are presently widespread in the Central Otago lowlands were rare or absent prior to anthropogenic fires (e.g. Discaria toumatou, Kunzea ericoides, Leptospermum scoparium). Other tree and shrub species once present are now extinct in the region (e.g. Coprosma obconica, Plagianthus regius, Pseudopanax ferox). The loss of these indigenous woody vegetation communities was a major factor contributing to the extirpation of many small bird species, and undoubtedly also reptile and invertebrate species, from the region. Plant macrofossils from rockshelters included remains of bird nests, identifiable by desiccated feathers and eggshell amongst them. These macrofossils include the first described plant remains from the nests of moa, which were constructed from a shallow bed of twigs of locally available shrubs and lianes. Many of the twigs are 25-30 mm in length and show evidence of having been clipped by moa bills. Desiccated coprolites, mostly of moa, but also specimens attributed to Finsch�s duck (Chenonetta finschi) and red-crowned parakeet (Cyanoramphus novaezelandiae), were recovered from rockshelter excavations. Moa species associated with a sample of coprolites were identified using ancient DNA analysis, and plant macrofossils from these were examined, together with previously unexamined moa gizzard content samples excavated from mires in the eastern South Island dryland zone. The results indicate that, in addition to previously reported browsing, upland moa (Megalapteryx didinus) and heavy-footed moa (Pachyornis elephantopus) also functioned as grazers, and seeds in their coprolites are dominantly of low shrubs and ground-cover herbs. Of particular interest was the higher than expected frequency of seeds from the currently rare and threatened 'spring annual' herbs; Ceratocephala pungens and Myosurus minimus subsp. novae-zelandiae (Ranunculaceae), suggesting further research on potential ecological relationships between moa and these plants would be worthwhile. The results of this study have provided a baseline for future conservation and restoration projects in the Central Otago lowlands.

<em>Abstract.</em>—Wood induces hydraulic, morphologic, and textural complexity into fluvial systems in forested regions around the world. Snags and logjams can create complex networks of channels and wetlands across entire river valleys and historically posed a significant obstacle to navigation. The clearing of wood from channels and riparian forest land reduced or eliminated the quantity and supply of wood into rivers in many regions of the world. Ecological restoration of fluvial environments increasingly includes the placement of wood. But few guidelines exist on appropriate methods for emulating natural wood accumulations, where and how to place wood, its longevity, the hydraulic and geomorphic consequences of wood, and how to manage systems where wood is reintroduced. Important factors to understand when placing wood in rivers include the watershed and reach-scale context of a project, the hydraulic and geomorphic effects of wood placements, possible changes in wood structures over time, and how it may impact human infrastructure and safety. Engineered logjams constructed in Washington, USA and New South Wales, Australia offer examples of how wood reintroduction can be engineered without the use of artificial anchoring to form stable instream structures as part of efforts to rehabilitate fluvial ecosystems and provide ecologically sensitive means to treat traditional problems such as bank stabilization and grade control.