doi.org
Contrasting rare earth element responses to climate and pedogenesis in two sand chronosequences along a climosequence in southwestern Australia - Plant and Soil
Background and Aims Rare earth elements (REEs), known as lanthanides, play a crucial role as controls and indicators in geochemical and environmental studies due to their consistent chemical properties. Despite extensive research on the geochemical applications of REEs, the effects of pedogenesis on their characteristics remain poorly understood, which limits their use in tracing soil-forming processes. To address this, we assessed the distribution and fractionation of REEs along two sand-dune chronosequences spanning a climosequence in southwestern Australia (the Jurien Bay and Warren chronosequences). We aimed to (i) evaluate changes in REE distribution over two million years of pedogenesis, (ii) quantify the influence of climate on this process, and (iii) assess the consistency of the soil parent sand along the chronosequences and determine the extent to which the soils have been reworked. Methods Soils were collected along two 2-million-year chronosequences differing in climate. The REE concentration was quantified by acidic digestion and detection by inductively coupled plasma mass spectrometry. We correlated REE distribution and soil properties to compare patterns of REE with pedogenesis under contrasting climates. Results Our findings indicate that REE concentrations were determined by weathering state and pedogenic processes. Along both chronosequences, lower REE concentrations are observed in surface horizons, associated with higher weathering intensity and organic matter accumulation. However, differences in climate between the two sites resulted in distinct REE fractionation patterns. The cooler and humid conditions at Warren promoted greater REE mobilization than under the warmer and drier climate at Jurien Bay. Despite these differences, overall REE signatures indicate that all soil stages were derived from similar parent sands with minimal reworking. Conclusion This study highlights the potential of REEs as tracers for long-term pedogenic processes. Patterns in REE reflect the combined effects of parent material, weathering intensity, and climatic conditions. This supports the hypothesis that climate influenced REE distribution in soil can be used to trace soil formation and landscape evolution. Future research should expand this approach to other climatic regions and soil types.
