Carbon-Nitrogen dynamics in Australian grasslands

In a warmer climate, regional and global climate models have projected Australia to experience an increasing intensification of rainfall extremes, ranging from heavy rains to long droughts. These changes in rainfall regimes can increase variations in soil water content, which drives various ecosystem processes that affect vegetation growth, soil respiration, biogeochemical cycles, and greenhouse gas emissions.

We used BRTSim to simulate the impacts of the projected rainfall regimes on the emissions, stocks, and leaching of carbon and nitrogen in Australian grasslands. Figure 1 shows the reaction network of the coupled C-N cycle (BAMS2) solved within BRTSim. BAMS2 is one of the most comprehensive soil organic matter (SOM) reaction network that considers the depolymerization and mineralization of 11 SOM pools, the transformation of inorganic nitrogen through fixation, nitrification, and denitrification, the plant dynamics, and the explicit accounting for growth, mortality, necromass decomposition, and water stress response of five microbial functional groups. This work used the liquid-biological feedback module in BRTSim to simulate microbial and plant responses to water stress and has successfully modelled the “Birch” effects that have been widely documented in field experiments. The animation in Figure 2 shows the dynamics of soil saturation and the concentrations of dissolved, solid, and protected SOM, CO2 and N2O gases, and the dynamics of heterotrophic bacteria and fungi. Comprehensive analyses of SOM dynamics in Australian grasslands can be found in PUBLICATIONS.