Добірка наукової літератури з теми "Riparian ecology Victoria"

Many of the world’s agricultural areas have greatly reduced levels of natural vegetation. This results in highly fragmented mosaic landscapes with multiple land-use types. We examined the importance of vegetation and landscape pattern by comparing the bird assemblages of riparian zones, non-riparian forest patches, and pasture in a fragmented agricultural landscape in south-eastern Australia. Bird surveys were conducted every four weeks at 27 sites in the Goldfields region of central Victoria for one year. The landscape context (position and shape of patches) and vegetation attributes were measured for each site. We found that bird assemblages strongly differed among these landscape elements. Mean abundance was significantly greater at forested patches, and there was a three-fold reduction in species richness at pasture sites. Bird assemblage structure was influenced substantially more by vegetation than by the landscape context of sites. Our results indicate that riparian vegetation is a key element for avian diversity, even in massively altered landscapes. The restoration of riparian vegetation and its connectivity with adjacent forest types would greatly benefit bird assemblages in agricultural areas.

The results of a trapping and spotlighting survey in Victoria of the squirrel glider, Petaurus norfolcensis, coupled with examination of historical records showed that the species is restricted to the Riverine Plains, Northern Uplands and northern slopes of the Western Highlands. Within these regions squirrel gliders inhabit remnant woodlands or open-forests which have mature or mixed-age stands of more than one eucalypt species, or riparian open-forests of Eucalyptus camaldulensis. The mixed-species stands which support squirrel gliders invariably include gum-barked and high nectar-producing species including some which flower in winter. The riparian open forests typically contain mature Acacia dealbata which may provide an important winter carbohydrate source. The squirrel glider was often the only arboreal mammal detected at a site; if another species was present it was usually the common brushtail possum, Trichosurus vulpecula. Other petaurids rarely occurred at the same site. We suggest that in Victoria the ecological tolerance of the squirrel glider is narrow 'and that the species should be considered vulnerable because most of its habitat has been cleared for farming. Commercial exploitation of timber and grazing of stock in much of the remaining habitat places further stress upon the small, fragmented populations of this species.

The responses of seedlings of Tristaniopsis laurina and Acmena smithii, two important tree species in riparian warm temperate rainforest communities in Victoria, are investigated in relation to flood disturbances. Freshly germinated A. smithii seedlings had died within 5 weeks of complete waterlogging in the greenhouse, and although the young T. laurina seedlings survived waterlogging for 14 weeks, their growth rate was curtailed. Nine-month-old seedlings of both species were found to be relatively tolerant to waterlogging, forming aerenchymatous surface roots after 40 days of flooding. Neither species suffered leaf abscission or demonstrated any other signs of water stress commonly associated with flood intolerant species. In experiments to determine the resilience of these species to physical flood damage, both species also demonstrated a capacity to regenerate vegetatively following the removal of above ground parts in young seedlings. The heartwood of T. laurina was found to be more decay resistant than that of other species in the field including that of A. smithii. The significance of these results are discussed in relation to other factors examined in earlier papers adding to the understanding of the ecological status of these species within the riparian rainforest communities.

The drought tolerances of the warm temperate rainforest species Tristaniopsis laurina and Acmena smithii were examined. Using pressure bomb techniques the tissue water relations of hardened juvenile and adult material were measured. T. laurina showed relatively little physiological drought tolerance in either the juvenile or adult plants, whereas A. smithii showed an increase in physiological drought tolerance in adult plants. Direct observations of droughted hardened 9-month-old seedlings revealed a relatively high leaf conductance in T. laurina seedlings with wilting becoming generalised after 9 days of droughting. All T. laurina plants rehydrated after 15 days of drought survived albeit with significant leaf abscission, but only 2 of the 5 plants rehydrated after 20 days of drought recovered and these were defoliated. Stomatal resistances were higher in droughted A. smithii seedlings and wilting did not become generalised until after 14 days of droughting. All A. smithii plants recovered when rehydrated after 20 days of droughting with little or no sign of leaf abscission. Leaves of T. laurina and A. smithii became scorched when subjected to temperatures of 50°C and 60°C respectively. The extent to which these differences delimit the distribution of these species in the relatively dry warm temperate rainforest communities of Gippsland in Victoria is discussed.

An extensive survey of the distribution and abundance of the spotted tree frog, Litoria spenceri, was conducted throughout its range in the Central and Eastern Highlands of Victoria and parts of New South Wales and the Australian Capital Territory between November 1991 and April 1994. Of the 64 streams surveyed, Litoria spenceri was recorded along 16, 15 in Victoria and one in New South Wales. The species was located along six streams in which it had not been recorded before, but could not be found along four streams in which it had previously been recorded. The survey failed to detect L. spenceri at historical sites on four other streams but located it elsewhere along those streams. Frogs were located predominantly in association with rocky banks adjacent to fast flowing water. Most populations occurred in dissected mountainous country, generally in areas with limited access and disturbance. Analysis of disturbance histories at individual sites and within catchments supporting the species indicates an association between the contraction in distribution and a number of human disturbances to forest and riparian habitats.

Free-living common wombats (Vombatus ursinus) living at high densities on pastoral land (1.9 wombats ha–1) had most of their burrows (83%) confined to a 20-m-wide strip of remnant riparian vegetation adjacent to pasture (24 burrows ha–1). The ratio of wombats to 'active' burrows (being used by wombats) was 1.0. Wombats shared burrows extensively, with a mean of 3.1 ± 0.3 (s.e.), range 2–9 wombats using each burrow (n = 37). The majority (70%) of occupied burrows contained several wombats independent of age, sex and stage of reproduction. On average, wombats used the same burrow for 3.8 consecutive nights before changing to another. Home ranges of wombats overlapped completely. Adult males had larger home ranges than females with young (7.3 ± 0.6, 6.1–8.3 ha, n = 3 versus 3.8 ± 0.5, 2.4–5.0 ha, n = 4, respectively). Distances travelled and the area used each night by wombats decreased in late winter and spring, when food was more abundant. Breeding occurred throughout the year but there was a cluster of births in summer. Lactation was associated with weight loss in females of several kilograms. Usually larger (30 kg) males that shared burrows or used burrows near (<300 m) to the burrows used by a female sired her young; however, occasionally wombats that used widely separated burrows (>700 m) bred. Adult males had a greater head length to weight ratio than adult females. Adult males generally emerged from their burrows shortly after dusk and 30 min before adult females. Ectoparasites such as ticks, mites, fleas and lice were common but the mite Sarcoptes scabiei was not found nor were there signs of sarcoptic mange in the population.

Tristaniopsis laurina and Acmena smithii often form a dominant association in riparian warm temperate rainforest communities in Victoria. The photosynthetic and morphological responses of seedlings of these species to varied light regimes, and the growth responses of seedlings in different nutrient regimes were examined in the laboratory. Acmena smithii was the most shade tolerant, having the lowest light compensation points, dark respiration rates and greater increases in leaf area ratio under low light conditions. Tristaniopsis laurina consistently demonstrated greater maximum rates of leaf photosynthesis at higher photon flux densities. In response to increased nutrients, T. laurina seedlings showed a marked increase in growth and a decrease in root/shoot ratios, while A. smithii demonstrated relatively small growth increases and showed an increase in root/shoot ratios. These results are discussed in relation to the ecological status of these species within the rainforest communities.

Riparian clearing and the removal of wood from channels have affected many streams in agricultural landscapes. As a result, these streams often have depauperate in-stream wood loads, and therefore decreased habitat complexity and lower levels of in-stream biodiversity. The introduction of wood was investigated as a possible rehabilitation technique for agricultural streams. Wood was re-introduced to eight streams in two separate high-rainfall, intensively grazed regions of Victoria, Australia and the effect on aquatic macroinvertebrate communities was measured. The addition of wood increased overall family richness and the richness of most functional feeding groups occupying edge and benthic habitats within the stream. Wood addition led to less overlap between benthic and edge macroinvertebrate communities, suggesting increased habitat heterogeneity within the stream ecosystem. Of all sampled habitats, wood supported the greatest density of families and was colonised by all functional feeding groups. Wood habitats also had the highest overall richness and supported the most taxa that were sensitive to disturbance. These findings suggest that re-introducing wood to agricultural streams is an appropriate rehabilitation technique where those streams are affected by reduced habitat complexity. Additional work is needed to confirm these findings over larger spatial and temporal scales.

Bucket dredging to mine and extract gold and tin from rivers is a global industry that has had a range of negative effects on physical environments. These include the destruction of riparian soil profiles and structures, artificial channel straightening and loss of in-stream biodiversity. In this paper we evaluate the immediate effects and long-term consequences of bucket dredging on rivers in Victoria and New South Wales during the period 1900–1950. High quality historical sources on dredge mining are integrated with geospatial datasets, aerial imagery and geomorphological data to analyse the scale of the dredging industry, evidence for disturbance to river channels and floodplains and current land use in dredged areas. The study demonstrates that the environmental impact of dredging was altered but not reduced by anti-pollution regulations intended to control dredging. An assessment of river condition 70–100 years after dredge mining ceased indicates that floodplains and river channels continue to show the effects of dredging, including bank erosion, sediment slugs, compromised habitat and reduced agricultural productivity. These findings have significant implications for river and floodplain management.

"Exotic willows (Salix spp.) are widespread riparian tree species of streams in temperate Australian and New Zealand. In Australian willow speicies are declared weeds of national significance, yet little is known about the novel habitats they create not the impact on aquatic biota of vegetation change following willow management programs ..." [leaf i]
Doctor of Philosophy

"Exotic willows (Salix spp.) are widespread riparian tree species of streams in temperate Australian and New Zealand. In Australian willow speicies are declared weeds of national significance, yet little is known about the novel habitats they create not the impact on aquatic biota of vegetation change following willow management programs ..." [leaf i]
Doctor of Philosophy

The exotic plant Lantana camara L. has invaded the riparian areas of the Victoria Falls World Heritage Site in Livingstone, southern Zambia, threatening native plant communities which support populations of species of special concern. I trialled the mechanical control method of manual uprooting and 3 different herbicides applied through paint brushing of an imazapyr concentrate at 250g. l¯¹, spraying on cut stumps with metsulfron methyl at 600g.l¯¹, and foliar spraying on re-emergent lantana foliage with glyphosate at a dosage of 166g. l¯¹ in July 2008 in 20 100m2 treatment plots, 5 invaded control plots and 5 uninvaded controls. Follow-up treatments for re-sprouting lantana stumps and emerging seedlings were undertaken in June 2009. I measured effectiveness of the methods using adult lantana mortality in June 2009 and lantana seedling density in the different treatment plots during the follow-up exercise. The cost of the various methods and human labour applied were compared across the four treatments at initial clear and at follow-up. All treatments recorded a high adult lantana mortality rate, though there were no significant differences in lantana adult mortality amongst the treatments. Overall, uprooting had the highest adult mortality, followed by imazapyr, metsulfron and lastly glyphosate. Germination of lantana seedlings after clearing was high for all treatments but with no significant differences occurring between the treatments. Both adult lantana mortality and seedling density were however significantly different from the control. With labour included, chemical costs were far higher relative to uprooting, though uprooting costs were the highest when it came to the follow-up because of the emerging seedlings and some resprouting stumps. The effects of mechanical and chemical treatments on vegetation composition in the cleared areas were also assessed in order to detect any non-target and medium term effects of treatments. Contrary to expectation, none of the chemicals showed any significant effects on vegetation composition in the short and medium-term and no significant differences were found in plant species richness, diversity and seedling density between invaded and uninvaded plots at baseline, in October 2008 and in September 2009. In order to determine potential for unaided vegetation recovery in the riparian areas of the study site after lantana clearing, I conducted an investigation of soil seed banks and seed rain using 60 seed bank samples measuring 1800m³ collected from 30 invaded and uninvaded plots. Using the seedling emergence method, 1, 991 seedlings belonging to 66 species representing 27 families germinated from the seed bank. Sedges (Cyperaceae family) were the most abundant taxa in the seed banks from invaded areas, followed by Ageratum conyzoides, lantana, Triumfetta annua and Achyranthes aspera which also occurred in the uninvaded soil seed banks. The seed banks from uninvaded plots were dominated by the grass Oplismenus hirtellus. Overall, species richness, diversity and seedling density from seed banks in invaded areas did not differ significantly from seed bank in uninvaded areas and there was a low similarity in species composition when above ground vegetation was compared to seed banks from invaded and uninvaded areas. It would appear if natural regeneration occured from the current seed bank in disturbed areas, future vegetation would largely comprise of short lived, early successional species in the short term as the seed bank is dominated by non-native herbaceous weedy species. From the seed traps investigating seed rain, a total of 27 species numbering 623 individual seeds were found in the thirty 1m² seedtraps distributed in invaded and uninvaded areas at the five sites, over an intermittent period of three months. Lantana had the highest monthly arrival rate in the seed traps followed by Phoenix reclinata and Ricinus communis. The number of species with invasive potential found in the seed traps located in invaded areas was more than that found in seed traps under native vegetation cover by far. Considerable forest remnants still occur around the invaded sites, and these could serve as an important source for long-term natural re-establishment of native vegetation if seed availability by animals and wind dispersal continues, while the re-invasion of lantana is prevented by ongoing follow-ups and futher clearing of lantana invaded areas. It is concluded that while uprooting and other treatments are effective in the control of lantana, its successful control in the Victoria Falls World Heritage Site will require extensive clearing to keep it from reinvading infested areas after clearing as shown by the seed rain data. The high seedling density of lantana in the seed banks and in the cleared areas shows the need for ongoing follow-up in order to deplete soil stored seed banks. There is need for longer term research to establish what the exact follow-up requirements are in order to contain lantana re-infestation and create favourable micro-sites for native species to establish. It is predicted that ongoing lantana control in the cleared plots will most likely initiate long-term community recovery.