Environmental and disturbance regime constraints on savanna carbon storage in northern Australia

Savannas are heterogenous landscapes, and variability in above-ground woody biomass (AGB) is evident at spatial scales ranging from regions, to landscapes, and even within individual trees. Considerable prior research has explored the environmental drivers shaping biomass distribution, their relative importance and their interactions. However, most studies use field-based inventories that traditionally rely on AGB estimates based on surrogate measurements (stem DBH), species-specific allometric models, and the upscaling of random sub-samples at the patch scale. Errors propagate at each of these stages, and as such significant uncertainty remains in the estimation of savanna ABG across scales.
Recent advances in remote sensing technology allow us to obtain tree structural information at unprecedented detail and spatial coverage; however, suitability to the tropical savanna of northern Australia remains to be explored. LiDAR remote sensing for ecological applications is a fast-developing field and protocols for data processing and extraction are still being developed. LiDAR allows us to build highly detailed 3D models of our environment, and when applied to the measurement of AGB it enables us surveying across scales from individual trees (terrestrial laser scanning) to landscapes (airborne laser scanning) and even to broad regions (spaceborne laser scanning).
This project aims to quantify uncertainties in current AGB estimates in the tropical savanna of northern Australia. Establishing LiDAR remote sensing as suitable survey method will allow me to improve our understanding of ecosystem dynamics driving AGB in this highly dynamic system. Above-ground woody biomass is an essential metric in local and global carbon models, which have long been challenged by poor representation of the tropical savanna zone. Research output of this PhD project will improve our understanding of the local carbon cycle in tropical savannas and inform the savanna carbon market.