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Hurstville Grove, Australia

Brooks A.J.,New South Wales Office of Water | Chessman B.C.,Climate Change and Water | Haeusler T.,New South Wales Office of Water
Journal of the North American Benthological Society | Year: 2011

The biological effect of water abstraction from unregulated streams in New South Wales, Australia, was assessed with data on macroinvertebrate assemblages in riffles (445 samples) and pool edges (718 samples) obtained from a national assessment of river condition in 1995 to 2000. We used limiting environmental difference (LED) modeling to predict the macroinvertebrate assemblage expected for each sample in the absence of water abstraction and estimated effect by comparing predicted and observed assemblages for sites with upstream abstraction. We found a high likelihood of effect on macroinvertebrates in 30% of riffles with upstream abstraction and 22% of edges. Complex combinations of biological traits appeared to determine the sensitivities and tolerances of individual taxa to water abstraction. For example, rheophilous families generally were rarer than predicted in apparently affected riffles, where thermophilic families seemed tolerant of the effects of water abstraction, and free-swimming families were less common than predicted in apparently affected edges, where families with tegument respiration appeared unaffected by water withdrawals. The trait response was clearer for the riffle fauna than for the edge fauna, perhaps because the physical and chemical effects of abstraction are more consistent for riffles than for edges. Our approach can support management planning by identifying taxa that are most at risk from water abstraction and sites where apparent effects are most evident. © 2011 The North American Benthological Society. Source

Bowker M.A.,Northern Arizona University | Eldridge D.J.,University of New South Wales | Val J.,Climate Change and Water | Soliveres S.,Rey Juan Carlos University
Soil Biology and Biochemistry | Year: 2013

Water redistribution has a profound influence on dryland ecosystem function. This hydrological function is largely regulated by ecosystem engineers including biological soil crusts (biocrusts) which produce run-off, and burrowing animals, such as the greater bilby, whose pits capture water. We estimated the relative importance of these two ecosystem engineers in determining infiltration rates in a system where dune slopes shed water to adjacent interdune swales to maximize overall productivity. Also, we determined which biocrust property was most hydrologically important: total cover, composition, patch aggregation or spatial heterogeneity. While both biocrusts and burrowing animals equally affected the overall infiltration through macro- and micropores (under ponding), only biocrusts were important for the infiltration specifically via micropores (under tension). Of the studied biocrust properties, community composition was the strongest influence such that the greater the prevalence of early successional biocrust patches, the greater the infiltration rate. Greater total cover of biocrusts reduced infiltration, and the spatial properties were relatively unimportant. Although bilbies and biocrusts comparably influenced infiltration under ponding at the microscale, realistic cover of bilby pits at the landscape scale is unlikely to strongly impair the hydrological function of dunes. Reintroduction of the endangered bilby may enhance nutrient cycling and plant recruitment via its seed and resource capturing pits, without a concomitant disruption of hydrological function. In contrast, removal of biocrusts caused by, e.g., livestock trampling, is expected to strongly enhance infiltration in the run-off areas, strongly reducing ecosystem productivity at the landscape scale. © 2013 Elsevier Ltd. Source

Eldridge D.J.,University of New South Wales | Val J.,Climate Change and Water | James A.I.,University of New South Wales
Austral Ecology | Year: 2011

Despite the widespread recognition that disturbance by livestock affects multiple indices of landscape health, few studies have examined their effects on both biotic and abiotic processes. We examined the effects of livestock disturbance on soil, vascular plants and reptiles across a disturbance gradient in a semi-arid Australian woodland. Our gradient ranged from long-ungrazed water remote sites, through intermediately grazed recovering sites, to currently grazed sites close to water. Our aim was to examine the nature of the effects of grazing-induced disturbance on biotic and abiotic processes along the gradient. We detected small biotic effects, but no abiotic effects, at low levels of disturbance (intermediate sites). We could not detect a consistent biotic effect on plants or reptiles along the gradient, except between the extreme disturbances. In contrast, we recorded substantial reductions in abiotic structure and function at the most disturbed sites. Structural changes included reductions in the cover of shrub hummocks and increases in bare soil, and reductions in cryptogamic soil crusts. Structural changes were associated with declines in function (soil stability and nutrient indices). Our data are consistent with the notion that abiotic effects predominate at high levels of disturbance in rangelands. Given the extent of abiotic modification at currently grazed sites, the cover of abiotic elements such as hummocks and soil surfaces would seem a better indicator of the long-term effect of grazing-induced disturbance than biotic components. The extent of disturbance at currently grazed sites across large areas of rangeland suggests that autogenic recovery will be protracted. © 2010 The Authors. Journal compilation © 2010 Ecological Society of Australia. Source

Shao Y.,University of Cologne | Ishizuka M.,Kagawa University | Mikami M.,Japan Meteorological Research Institute | Leys J.F.,Climate Change and Water
Journal of Geophysical Research: Atmospheres | Year: 2011

A critical problem in dust research is to estimate size-resolved dust emission rates. Several dust schemes have been proposed but are yet to be rigorously tested against observed data. In the recent Japan-Australia Dust Experiment (JADE), size-resolved dust fluxes were measured. In this study, the JADE data are used to test a size-resolved dust scheme. Our aim is to examine whether the scheme has the capability to predict size-resolved dust fluxes, what the ranges of the scheme parameters are, and whether the scheme is sensitive to the parameters. The JADE data show that dust emission depends linearly on saltation flux and thus confirm the basic assumption of the scheme. The magnitudes of the scheme parameters are found to be consistent with those reported in earlier studies. The estimated size-resolved dust fluxes are in satisfactory agreement with the measurements, although considerable discrepancies remain and are difficult to rectify without speculative tuning of the scheme input parameters. The discrepancies have been traced back to the uncertainties in the parent soil particle size analyses and in the dust flux observations. Ensemble tests showed both model physics uncertainties and parameter uncertainties. It is proposed that the dust scheme under consideration is not as sensitive as previously suspected and is likely to perform well if the parameters are specified within a reasonably correct range. Copyright 2011 by the American Geophysical Union. Source

Chessman B.C.,Climate Change and Water | Townsend S.A.,Charles Darwin University
Ecological Indicators | Year: 2010

The DSIAR biotic index for freshwater diatoms, regarded as a potential indicator of impact from agricultural and urban land use on rivers in temperate south-eastern Australia, did not correlate significantly with an index of catchment condition in a tropical region of northern Australia. However, the relationships between the index and water chemistry, especially pH, salinity and concentrations of nitrogen and phosphorus, were consistent in both regions. The variable relationship between the index and catchment conditions can be explained by differing effects of catchment land use on stream-water chemistry in northern and southern Australia. In the south, land use has commonly resulted in increases in stream pH, salinity and nutrients, whereas in the north its impact on pH and salinity appears weak. These findings emphasise the need to interpret biological and ecological indices in the context of the varying causal pathways by which human activities affect stream ecosystems in different circumstances. © 2009 Elsevier Ltd. All rights reserved. Source

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