Keeping carbon
There is increasing global evidence on the potential of grasslands to sequester soil organic carbon (SOC) through improved management. However, opportunities for increases in SOC in the tropical and semi-arid Australian grasslands of northern Australian grasslands remains unclear, with the limited Australian research showing contradictory results. Furthermore, current SOC process models, and the fundamental equations that underpin them, are based predominately on research from temperate bioregions, and likely do not represent northern Australia’s extreme climatic fluctuations and prolonged dry periods.
This project aims to determine if pasture management can increase the persistence of SOC to drought and promote permanence – a critical aspect of carbon accounting. This project will focus on the clay rich soils that dominate large areas of North-Eastern Australia, covering key beef production bioregions such as the Brigalow belt and Mitchell grasslands. These soils have the highest potential for soil carbon gains through improved management but are in some of the most drought prone regions of Australia. The project will address two core hypotheses: 1) Drought – specifically the lack of new carbon inputs through plant growth and the extreme desiccation of the microbial biomass – is a period of significant carbon loss from grasslands, and 2) improved management can increase the proportion of persistent carbon that is resilient to climatic fluctuations. In terms of improved management, research suggests that grazing management combined with greater functional diversity and deep-rooted perennial can act to increase mineral-associated organic carbon that is likely to persist in the soil in the long-term.
Simulated drought in these regions, combined with novel isotope labelling techniques, will generate a process level understanding of the mechanisms driving SOC persistence to drought and allow us to examine the impact of management at the paddock scale under a range of climate scenarios. The project will take a 4 step approach to quantify the impact of drought by 1) using rainfall enclosures to assess drought impacts on pasture growth and resilience, as well as soil biology and nutrient turnover 2) examine how management influences SOC dynamics and resistance to drought using 13C isotope tracers at the soil/root interface, 3) update our mechanistic understanding of the transformation of AGB into stable SOC under Australian conditions and 4) update, calibrate and validate DayCent for northern Australian conditions.
Project team
Project funding
