Earth Systems education
In early April 2022, the Mulloon Institute hosted over 50 students and staff from the University of Canberra for education and training on identifying soils and geomorphology at Mulloon Creek Natural Farms (Home Farm).
Led by UC’s Associate Professor Duanne White, the students split into groups and dispersed across the catena sequence (sequence of soils down a slope), from hillslope across the floodplain valley floor and across to the opposite hillslope. Students dug holes down through the soil profile and assessed the various layers, collecting important information of texture, colour, composition, pH, and presence of organic matter. These are important factors to determine the type of soil, its health (pH and organic matter) or ability to function (water infiltration and water holding capacity), and what this reveals with respect to land use and management.
The students found a range of soils that were shallow (0.5m depth) on the hillslopes, and greater than 2m depth in the floodplains with pasture plant roots regularly found to 1m depth. Soils were generally in good condition with pH consistently in the neutral range, and good soil texture and aggregation in the upper root zone. In some soil profile locations on the floodplains, students encountered a sandy or gravel lens buried that indicates a previous shallow waterway that has since been buried due to morphological processes and as the floodplain soils build over time.
Figure 1: GPR transect across the floodplain at Mulloon Creek Natural Farms.
UC Honours student Celine Anderson used a portable ground penetrating radar (GPR) to detect the subsurface structure of the soil that may indicate different soil layers including shallow aquifers. The GPR data indicated some paleochannels (buried old alluvial channels) in the floodplain (see image 1 below). Duanne cross-referenced this against the topographic data using the LiDAR derived DEM (see image 2), with both datasets confirming the channels existence, and the GPR data provides information of depth and extent.
The value of this data is understanding the location and size of such paleochannels and how they function to help move and store water within the floodplain and whether they connected to the stream. These paleochannels play an important role when the creek floods and spills onto the floodplains for storing water naturally in the landscape that increases plant available water and soil microbial processes. These processes are vital for plant vigour, nutrient cycling, building soil, sequestering carbon that in turn increases the soil water holding capacity.
Figure 2: Digital Elevation Model of the topography of the floodplain at Mulloon Creek Natural Farms.
This work forms part of the Mulloon Rehydration Initiative which is jointly funded through the Mulloon Institute and the Australian Government's National Landcare Program, with support from the NSW Government's Environmental Trust.