Salinity Control and Catchment Management
A pre-requisite for sustainable land management is the management of water balance at a landscape and catchment scale. Understanding water balance is central to achieving effective control of salinity, nutrient loading in streams and wetlands and optimizing yield of potable water in catchment areas. Dryland salinity is one of Western Australia's main environmental problems. Our involvement in this area was a conscious effort to engage in research that makes a significant contribution to solving this major form of land degradation in WA. Research Topics
Flowtube ProjectDryland salinity is a major problem affecting agricultural production in all Australian states. Much time, effort and money is currently being spent by land managers and grain growers on agronomic, tree-based and engineering strategies to ameliorate the problem. Unfortunately there are few means of quickly and simply assessing beforehand the spatial impact of these treatments. Development of a simple tool to do this is urgently required. The groundwater computer model Flowtube developed by CSIRO Land and Water (CLW) has the potential to be evolved into such a tool. Modelling on behalf of the WA State Salinity Council using Flowtube investigated the impacts of the treatments recommended in the WA Salinity Action Plan, and after showing these to be inadequate for the task, investigated more effective alternatives. The model proved very effective in the rapid assessment of recharge management scenarios and in modelling the effect of a variety of treatments, but the catchments tested were quite difficult to set up and a computer expert was required to operate it. The Department of Agriculture Western Australia commissioned The University of Melbourne (UniMelb) to develop the Flowtube program for the WA type catchments for the development of dryland salinity (RIRDC 1998A) so that catchments are easy to set up and so that it operates in a Windows type "point and click" environment. This project extended the Flowtube program to do the same for the eastern states catchment conceptual models (RIRDC 1998A) and to provide thorough testing of the program for all catchment conceptual models. Land and Water Australia and GRDC jointly funded it from March 2001. The Flowtube program can be inspected and downloaded from http://www.civenv.unimelb.edu.au/~argent/flowtube/
Deep drains —are they an acceptable strategy for alleviating salinity in valley floors of the wheatbelt?
Many strategies have been proposed over the past 30 years to assist farmers deal with dryland salinity. Some have been discarded over the years. Others such as the widespread planting of deep-rooted perennial vegetation would be effective but the cost of widespread planting is daunting. Besides broadacre agriculture would cease to exist as we presently know it if large percentages of catchments were to be replanted across the wheatbelt. It is clear that the continuation of broadacre cereal and grains cropping will be at the cost of further spread of salinity unless a new cost-effective solution to the problem of rising saline groundwater is found. Many farmers in the WA wheatbelt are attracted to the installation of deep drains (2.5 to 3 m depth) as a means of alleviating salinity on their land. However, for other farmers and communities, questions remain about the effectiveness of drains, and about the possible downstream impacts. Some of the answers to these questions will come from a new project funded under the State Government’s Engineering Evaluation Initiative (EEI). Murdoch Environmental Scientists, Associate Professor Jenny Davis and Richard Bell are each involved in the EEI. The purpose of Richard’s project is to examine the changes in soil properties after salt-affected and waterlogged land is drained. Given the diverse nature of soils subject to salinity and waterlogging in Western Australia, the expected responses in soil quality to drainage will vary. Two sites (Dumbleyung and Beacon) varying in soil properties, and rainfall patterns were chosen for detailed study. Less intensive soil investigations will be carried out at other sites where deep drains are being installed under the EEI (Pithara, Morawa, Date Creek). On sandy, non-dispersive (non-sodic) soils in the high rainfall areas of the wheatbelt, there are believed to be good prospects for rapid recovery of soil productivity after deep drainage. On other soils, and in lower rainfall zones, a range of amendments could be needed to accelerate the recovery of soil productivity. Ripping at least on dispersive duplex and clay profiles may be necessary to accelerate the leaching of salts. Gypsum application may also be needed on the dispersive soils to achieve initial soil flocculation, but research is needed to define the soils that respond to gypsum, work out the amount required and whether a single application is sufficient. The development of stable soil structure usually also requires organic matter otherwise the effects of ripping and gypsum can be short lived. Finally biological drilling of soil by plant roots of salt-tolerant species may be used to accelerate the recovery of soil quality. These investigations will enable us to recommend when soil amendments are needed and the best package of practices for effective soil productivity recovery following deep drainage. The work is being conducted by Associate Professor Richard Bell and Mr Carlos Raphael, Murdoch University in conjunction with Dr Surender Mann, Chemistry Centre (WA), Mr Noel Schoknecht, and Dr M. Hamza, Department of Agriculture Western Australia.
Saltland pastures in southern Australia –opportunities for carbon sequestration?The aim of our project is to quantify the carbon trading benefits that accrue from saltland pastures on salt-affected and waterlogged agricultural land in south-west Australia. The purpose of the research is to determine how soil types, water regimes, and land management affect rates of carbon sequestration and how the rates of carbon sequestration and greenhouse gas emission might respond to revegetation with saltland pastures. The outcomes will be accurate greenhouse accounting for saltland pasture, informed development of carbon trading policies to decrease the economic and environmental impact of dryland salinity, and rehabilitation of saltland. The science community now acknowledges that the race has been lost to prevent dryland salinity from affecting large areas of land in south-west Australia. However, the scenario of living with increasing areas of salt-affected land need not become an economic and environmental burden to the community. On the contrary, once established, saltland pastures have considerable promise in generating economic and environmental benefits in farming systems. Carbon sequestration and decreased greenhouse gas emissions are potential additional environmental and economic benefits from saltland pasture that are presently unaccounted for. Dryland salinity is a major land degradation issue Australia-wide. Western Australia has the largest area of dryland salinity in Australia, and the highest risk of increased salinity in the future. The original landscape of southern Australia was mostly covered with deep-rooted perennial vegetation with steady-state carbon stocks below- and above-ground. In addition, it maintained steady-state water tables that were mostly well below the root zone of vegetation. However, with the development of agriculture, reliant on annual crops, increased water recharge to groundwater has occurred resulting in the rise in water tables and the development of dryland salinity. Under conventional agriculture soil salinity reduces plant growth, and hence lowers carbon stocks aboveground and in the soil. It also reduces microbial activity and therefore, changes carbon turnover as well as carbon dioxide (CO2) emission to the atmosphere. Increased waterlogging in saline soils may accelerate the emission of nitrous oxide (N2O) and methane (CH4) and on a molar basis these gases have more damaging greenhouse effects than CO2. Soil sodicity frequently occurs with salinity, and alters soil pH and other physical-chemical characteristics of soil so that microbial and chemical transformation of added plant carbon as well as soil carbon are altered. Bare salt-affected land often suffers from accelerated soil erosion that further depletes soil carbon. However, information is scarce on the quantitative impacts of salinisation and revegetation of salt-affected land on its carbon stocks and fluxes. An attractive option for salt-affected land is to rehabilitate it with vegetation that is salt and waterlogging tolerant. Such vegetation can lower groundwater levels, sequester carbon, and change soil carbon stocks and their turnover. However, many farmers are reluctant to invest in such areas due to cost. There is a clear imperative to add economic value to saltland revegetation, and carbon sequestration offers one such opportunity. The project will be carried out by the Land Management group in collaboration with Dr Surender Mann, Chemistry Centre (WA), Dr Ed Barrett-Lennard, Department of Agriculture and the Saltland Pastures Association.
Identify and verify critical source areas for P load and offsite risk in the Fitzgerald River CatchmentThis research is focused on the P loss mechanisms from the landscape, considering interactions between the potential source areas for P in the catchment, soil P level, fertilization practices over time and transport processes involved in the mobility of P in the landscape both in the runoff and erosion at Fitzgerald River Catchment. The Fitzgerald River National Park has both regional and national significance, and is listed as an international biosphere reserve with world heritage significance. Water draining from the Fitzgerald River agricultural catchment can produce offsite impacts on the biosphere reserve. Erosion and sedimentation are predicted to be the major problem on the Fitzgerald River. Fitzgerald Biosphere Group (FBG) sought to develop a clear understanding of the processes and rates of offsite export of phosphorus and sediments from cropping land into the National Park. Fitzgerald River catchment is located 20 km east of Jerramungup townsite or 400 km south east of Perth. This catchment covers an area of about 104,000 ha and annual rainfall ranges from 400 to 450mm. Objectives:
Ecosystem response to forest thinning in the Wungong Catchment
The Australian Research Council has agreed to fund a project between Murdoch University and the Water Corporation on “Balancing Water Quality and Ecosystem Health with Water Yield -- Ecosystem Response to Thinning in Wungong Catchment” under its Linkage programme, 2007-2010. The 4-year project worth $600,000 in cash and $500,000 in-kind contributions from partners will be led by Professors Richard Bell, Arthur McComb and Richard Hobbs of Murdoch University's School of Environmental Science. Dr Bishnu Devkota will manage the project for the Water Corporation with input from consultant Frank Batini. Dr Song Qiu who will be the Senior Research Fellow will look at processes underlying biological responses and the associated risks to water quality. A PhD student will be recruited to investigate vegetation responses and forest health issues associated with thinning. We expect to involve additional honours and postgraduate students during project. Earlier this year Patrick Schaub a visiting scientist from Switzerland spent 3 months conducting preliminary work in Wungong, examining litterfall from thinned forest stands. Futher interactions are anticipated with the various other research projects in Wungong some of which are already underway. Reduced rainfall in past decades and future climate uncertainty have added a sense of urgency in Australia to the search for new water resources to sustain a growing economy and population. The forest thinning trial in the Wungong Catchment is designed to substantially increase water yield for the Perth metropolitan area. Thinning is attractive as a low-cost option for increasing water supply, and is potentially suitable for other catchments. However the potential environmental and ecological impacts, which are major community concerns, must be investigated. To meet community expectations, the water yield from thinning must be sustainable and of high quality, with minimal impact on the catchment ecosystem as the thinned forests mature. This project will assess ecological responses to forest thinning in the Wungong Catchment. Vegetation dynamics, nutrient cycling processes and restoration pathways will be studied in relation to prescribed thinning, to define levels of disturbance, biotic and abiotic responses, and the capacity of catchment ecosystems to sustain thinning intervention. The project aims can be expressed as key research
questions (RQ): RQ 1 and 2 will be examined through establishing and quantifying interrelationships between site micro-climate, residue turnover, soil nutrient dynamics, plant physiological responses, and vegetation dynamics in relation to ecosystem composition, structure and function. RQ 3 will be addressed through tracing nutrient fluxes in residue, soil, leachate, groundwater and stream water, to evaluate the export potential of nutrients and other materials, as well as the role of riparian buffer in ameliorating such fluxes. RQ 4 will be addressed through establishing and testing conceptual models of restoration trajectories in response to forest thinning. The hydrological response to proposed thinning and a broad-scale remote sensing of vegetation changes are planned in separate projects. Carbon cycling has been assessed and concluded to be neutral in relation to the thinning effects. These issues are not included in the scope of the present study.
The conceptual framework for the research is shown in Figures 1 and 2. The proposed thinning can be considered a 'disturbance' to the jarrah forest-ecosystem, which is at a successional state following bauxite mine rehabilitation or past logging. A thinned ecosystem unit is conceived as being forced into a non-equilibrium status, and tends to 1) make adaptive changes into a transitional state, and gradually transforms along successional gradients to next phase of equilibrium (whether it is a meta-state, alternative state or a restoration objective). But 2) if impact exceeds biotic and abiotic thresholds, the system shifts towards degradation, and this needs to be prevented though early diagnosis of ecosystem responses. We anticipate the proposed thinning to trigger pulses of responses and induce changes in ecosystem components according the direction of energy and mass flow (Fig.1). The changes in energy (light) and mass (water and nutrients) flow, starting from altered microclimate on the forest floor, are expected to underlie biological changes and link to hydrological processes and runoff water quality. The efficacy of thinning catchment for water yield relies on the maintenance of such non-equilibrium conditions. While changes in micro-climate, water and nutrient supply will be viewed as driving forces for transitional responses, the long-term succession of the post-thinning ecosystem will depend on the trends for energy and mass flow, climate and environmental conditions, and on the trajectory linked to intermediate and transitional ecosystem dynamics. We use post-thinning dynamics (short-medium term time frame) to ascertain the vegetational attributes and ecological processes of transitional states, and “space-for-time” substitution, i.e. measuring attributes of 'historical' thinned sites near Wungong Catchment, as 'surrogates' for “long term” succession (Fig.2), to gain insights into post-thinning successional trajectories of jarrah forest, critical for sustainable water management in WA. The first priority for the project is to select study sites in consultation with the Water Corporation and Department of Conservation and Land Management. Shortlisting of sites commenced in early February 2006, comprises monitoring sites, transects, plot experiments, and 'historical' sites.
Research Associates and Collaborators
Research Students' ProjectsPhD Students
MSc (Env. Sci.)
Honours
Recommended Additional Information
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author: R.Bell;
created: 16/06/03, updated:
19/10/09
, expiry: 31/12/10 Document edited by: H.Gordon |
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