UWA-CZO - Avon River Catchment, Australia's 1st CZO
The UWA-CZO is located in the Western Australia, approximately 25km north west of Pingelly and 160 km south east of Perth. It is part of the Eastern Darling Range and is located at the edge of the High Rainfall Zone (HRZ) for agriculture. Predominant land uses include grazing of livestock, cropping, perennial horticulture and rural residential development but there are vast areas of native bushland around. The site experiences a Mediterranean climate, with cool, wet winters and hot, dry summers. It has a mean annual rainfall of 445.4 mm. The driest months are December to February and the wettest months are June to July. The mean annual temperature is 10.4 (min) to 23.3°C (max) with a mean annual pan evaporation of 1600 mm.
The soils in this region have largely been shaped by the underlying geology and subsequent surface processes which results in a variable pattern of soil parent material. Climate has been another driving factor for soil formation and the seasonality in climate influences land qualities, such as waterlogging. Past climate has also been essential in shaping the geology and regolith of the region. The long weathering history of granitoid rocks has formed a deeply weathered landscape over 100Ma. This has resulted in nowadays dissected lateritic profiles with duricrust on top over deep sequences of mottled and pallid zone material that form the recent regolith above bedrock. Some faulting has occurred in the region, but other tectonic activity has been somewhat limited, as it is part of the geologically stable Yilgarn Craton. Other linear features dissect the landscape, such as mafic intrusions and dolerite dykes. Related to the geology and the climate is the hydrology of the landscape. Hillslope processes, such as surface runoff and subsurface flow, predominantly influence the upper parts of the landscape, within the mapping area. In comparison, intermittent streams characterize the lower parts of the landscape, with seasonal waterlogging often playing a large part in these areas.
This site offers a great variety of soil types, within a variable geologic and topographic setting. It is part of the larger Avon-River catchment and will act as the core CZO site.
The site offers some unique weathering factors. The weathering history and resulting soils in the southern hemisphere are often very different from those in the northern hemisphere because renewal of soil parent material by various processes during the Pleistocene ice ages (e.g. glacial and periglacial erosion and deposition, aeolian deposition of loess etc.) did not occur or only at an alleviated rate in the southern hemisphere. As a consequence soils and the associated critical zone often have different physical and chemical properties compared to otherwise similar environmental settings in the northern hemisphere – a circumstance that needs to be addressed in site specific as well as in global scale models. Additionally, the land use that influences soils and the critical zone, is very different, e.g., parts of the land in the southern hemisphere and on the site specifically have undergone clearing for agriculture only recently, i.e. during the past century or even less, which sets additional different preconditions.
The UWA-CZO site is the first CZO site in Australia – it is in its beginnings and will be “growing” over the years. http://www.see.uwa.edu.au/research/czo-critical-zone-observatory
PI: Matthias Leopold
PI: Deirdre Gleeson