Avon Critical Zone Observatory
Sally Thompson, Matthias Leopold, Louise Barton, Jason Beringer, Deirdre Gleeson, Caitlin E Moore, Andrew Rate, Megan H Ryan, Talitha Santini
The Avon CZO is an agricultural site, where 100 years of clearing and cropping have changed hydrology, the soils, and biology. Rotations of barley, canola and vetch cover the CZ site, which represents a state-of-the-art sustainable farming system for the Western Australian grainbelt. The CZ measures soil moisture – showing waterlogging in winter and plant water availability at the start of summer. Comparisons with nearby native vegetation show persistently less evaporation takes place from the CZ than under native vegetation.
The Avon CZO contains the remains of an ancient lateritic landscape amidst the colluvial valleys formed by its weathering. The critical zone is exposed at the Avon CZO in the remnant lateritic hills – including Avery’s Hill, which provides the upper-boundary of the CZO. These hills are inverted valleys, where wet conditions in ancient streambeds produced thick laterite which has not yet weathered away completely. Geophysical scanning shows how the lateritic cap has eroded to produce weathered, wet, slightly salty clay layers below a thin layer of soil. The highly leached, nutrient poor soils present many challenges to farming which originate from the CZ’s evolution.