Effects of land-use intensification on soil carbon and ecosystem services in Brigalow (Acacia harpophylla) landscapes of southeast Queensland, Australia

Soil organic matter is an effective indicator of soil resource condition that reflects functional traits such as aggregation and infiltration and plays a critical role in sustaining production and ecosystem services in agricultural landscapes. Agricultural practices typically reduce soil carbon through the action of soil disturbance and mineralization. In the Brigalow (Acacia harpophylla) landscape we studied, soil carbon levels in pellic vertisols were significantly lower in the agricultural matrix of cropping and grasslands than in remnant Brigalow vegetation. There was no detectable gradient of soil carbon across Brigalow/matrix boundaries. Uncultivated grasslands showed significantly higher carbon levels than currently and previously cultivated grasslands. Regenerating grasslands showed no significant recovery of soil carbon over 15 years. Total, organic and labile soil carbon fractions were used to indicate different aspects of soil function, with the more active (labile) components reacting more sensitively to changes in land management. The carbon management index (CMI) was used to combine the active and passive components of soil carbon to provide a sensitive indicator of the rate of change of carbon dynamics in response to changes in land management at local-scales. A landscape CMI (CMIL) was developed using a combination of soil samples and GIS-derived spatial data and is proposed as a potentially useful tool for modelling soil carbon dynamics in agro-ecosystems at local and landscape scales.