Rapid response of habitat structure and aboveground carbon storage to altered fire regimes in tropical savanna.

Fire regimes across the globe have been altered through changes in land-use, land management and climate conditions. Understanding how these modified fire regimes impact vegetation structure and dynamics is essential for informed biodiversity conservation and carbon management in savanna ecosystems. We used a long-term fire experiment at the Territory Wildlife Park (TWP), northern Australia, to investigate the consequences of altered fire regimes for habitat structure and aboveground carbon storage. We mapped vegetation three-dimensional (3D) structure in high spatial resolution with airborne LiDAR, across 18 replicated 1 ha plots of varying fire frequency and season treatments. We used LiDAR-derived canopy height and cover metrics to extrapolate field-based measures of woody biomass to the full extent of the experimental site (R² = 0.82, RMSE = 7.35 t C ha^-1), and analysed differences in aboveground carbon storage and 3D structure among treatments. Woody canopy cover and biomass were highest in the absence of fire (76 % and 39.8 t C ha^-1) and lowest in plots burnt late in the dry season on a biennial basis (42 % and 18.2 t C ha^-1). Woody canopy vertical profiles differed among all six fire treatments, with greatest divergence in height classes < 5 m. Our results highlight the large extent to which fire management can shape 3D structural patterns in savanna landscapes, even over time frames as short as a decade. The structural profile changes shown here, and the quantification of carbon reduction under late dry season burning, have important implications for faunal habitat conservation and carbon sequestration/emission reduction initiatives in the region. [ABSTRACT FROM AUTHOR]