Potential impacts of water resource development on soil character in a semi-arid floodplain-wetland complex

Altered flow regimes are widely acknowledged as a major driver of deteriorating conditions in Australian floodplain ecosystems. These ecosystems have historically been sites of high biodiversity and productivity with much of Australia's unique and endangered biota existing exclusively in these environments. Water resource developments, however, have the potential to significantly impact on these systems through both direct (e.g., reduced wetting frequency) and indirect (e.g., alterations of physical habitat) impacts on biota. This study seeks to investigate how changes in flows to semi-arid floodplain-wetland ecosystems could alter soil character, an important driver of biological productivity. Specifically, this study investigates soil properties along a flood frequency gradient to determine how soil characteristics relate to the magnitude and frequency of inundation. Forty five soil samples collected from each of four inundation zones (frequent, intermediate-frequent, intermediate-rare and rare) were analysed to determine the pH, EC, % organic matter, particle size and concentrations of a suite of 19 geochemical elements. The results of the study show that there is a reduction in organic matter and most geochemical elements and critical plant nutrients and an increase in clay content, acidity and salt from frequently to rarely flooded sites. This clear association between soil characteristics and flood frequency suggests that altering flow regimes could negatively impact on semi-arid floodplain soils with reduced frequencies of inundation resulting in degraded conditions that could have deleterious consequences for floodplain-wetland ecosystems