The Warrumbungle Post-Fire Recovery Project-raising the profile of soils

The impacts of a wildfire and subsequent rainfall event in 2013 in the Warrumbungle National Park in New South Wales, Australia were examined in a project designed to provide information on post-fire recovery expectations and options to land managers. A coherent suite of sub-projects was implemented, including soil mapping, and studies on soil organic carbon (SOC) and nitrogen (N), erosion rates, groundcover recovery and stream responses. It was found that the loss of SOC and N increased with fire severity, with the greatest losses from severely burnt sandstone ridges. Approximately 2.4 million t of SOC and similar to 74,000 t of N were lost from soil to a depth of 10 cm across the 56,290 ha affected. Soil loss from slopes during the subsequent rainfall event was modelled up to 25 t ha(-1), compared to a long-term mean annual soil loss of 1.06 t ha(-1) year(-1). Groundcover averages generally increased after the fire until spring 2015, by which time rates of soil loss returned to near pre-fire levels. Streams were filled with sand to bank full levels after the fire and rainfall. Rainfall events in 2015-2016 shifted creek systems into a major erosive phase, with incision through the post-fire sandy bedload deposits, an erosive phase likely related to loss of topsoils over much of the catchment. The effectiveness of the research was secured by a close engagement with park managers in issue identification and a communications programme. Management outcomes flowing from the research included installation of erosion control works, redesign of access and monitoring of key mass movement hazard areas.