1. Dr. Wendy Williams

Savannas cover ~20% of continental northern Australia with ~500–2000 mm annual rainfall, a long dry season and regular fire. They are used as rangelands for extensive beef cattle production. Farmers recognise that unsustainable grazing and burning practices, combined with droughts and floods, manifest in compromised productivity. Vast farm sizes (>200,000 hectares) prevent the application of fertilisers or soil ameliorants to compensate for the nutrient losses caused by soil degradation and cattle export. Our project raises awareness of the role of biocrusts in rangelands for protecting soil and generating organic carbon and bioavailable nitrogen, amongst other ecosystem services. Our multidisciplinary research aims to quantify the presence and function of biocrusts so that land managers can make informed decisions. Our study sites encompass two long-term research stations imposing contrasting fire (cool and hot fires) and grazing management (low and high intensity, grazing or seasonal resting). The project examines the functionality of biocrusts and their natural capacity to recover after fire and in relation to grazing regimes. Biocrust cover and micro-organism diversity were studied across micro sites of different soil types using field measurements, laboratory analysis (high throughput phylogenetic marker gene sequencing, carbon and nitrogen relations), as well as machine learning (mobile phone photos), and remote sensing. We highlight features of Australian cyanobacteria-rich biocrusts that have evolved with fire and weather extremes for millennia. We discuss how this knowledge can inform passive and active rangeland restoration efforts to ensure resilient savanna grazing lands.