When reconstructing a root zone system, it is critical to restore physical structure and hydraulic functions across the whole root zone system. Only effective and holistically restored systems can control hydro-geochemical mobility of acutely and chronically toxic factors from the underlying horizon and maintain hydro-geochemical stability in the rhizosphere. Thereafter, soil biological capacity and ecological linkages (i.e. carbon and nutrient cycling) may be rehabilitated to integrate the root zones with revegetated plant communities into sustainable plant ecosystems. A conceptual framework of system transitions between the critical states of root zone development has been proposed. This will illustrate the rehabilitation process in root zone reconstruction and development for direct revegetation with sustainable plant communities. Sustainable phytostabilization of tailings requires the systematic consideration of hydro-geochemical interactions between the rhizosphere and the underlying supporting horizon. It further requires effective remediation strategies to develop hydro-geochemically stable and biologically functional root zones, which can facilitate the recovery of the microbial community and ecological linkages with revegetated plant communities.

Poor soil physical conditions such as low hydraulic conductivity can limit salt depletion from surface soil. Altering the pore system by addition of organic and inorganic amendments may improve salt leaching as a reclamation strategy. Column studies were conducted to investigate salt leaching in amended and non-amended soil profiles. A one-dimensional water and solute transport model (HYDRUS-1D) was also assessed for its applicability to simulate salt leaching for amendment strategy. Columns of length 300mm were filled with saline-sodic soil at the lower end (100–300mm) and then covered with soil amended with 40% (wt/wt) fine sand and 20% (wt/wt) wood chips, separately. A control column was filled with saline-sodic soil only. One rainfall scenario typical for a location in south-west Queensland (Australia) was applied to the columns. Water potentials were monitored using tensiometers installed at three depths: 35, 120 and 250mm. The concentrations of individual cations (Na+, Ca2+, Mg2+ and K+), electrical conductivity and sodium adsorption ratio of the soil solutions were also monitored for the investigated depths. A reduction in surface salinity (up to 28.5%) was observed in the amended soil profiles. This study indicated that the addition of wood chips to surface soil improved salt leaching under the tested conditions. The simulation successfully predicted both hydrology and chemistry of the columns. This study also concluded that HYDRUS-1D is a powerful tool to simulate salt leaching in the amended soil profiles, and can be applied to predict the success of amendment strategy under natural climatic conditions.

Quantifying infiltration is a challenging and time‐consuming process because the parameters are very difficult to measure directly. Estimating them from dependent and readily measurable parameters is a more efficient alternative. Many existing studies have focused on deriving the parameters in the Green–Ampt model from basic soil properties, with few related to other infiltration models or factors. In this study, infiltration experiments were conducted on 28 small plots using a field rainfall simulator, with the purposes to: (i) investigate the effect of various factors on the parameters in four popular infiltration models; and (ii) develop predictive equations for each parameter from its identified major controlling factors. To achieve the best outcome, four factor sets including different numbers of factors were applied in a regression analysis. Results showed that each infiltration parameter was controlled by not only soil factors but also vegetation and rainfall. Soil properties alone were not sufficient to predict these infiltration parameters, while the regression equations developed from the full set of factors showed much higher accuracy. In addition, a simpler factor set including only the four most readily obtainable factors was evaluated, but the expected success was not achieved. However, the inclusion of the saturated hydraulic conductivity greatly improved the results to an acceptable level. The results of this study demonstrate the contribution of the effects of vegetation and rainfall on various infiltration parameters. The simplified predictive equations are also expected to improve the outcome with regard to effort, time, and cost in determining these parameters.

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