Same climate, different recovery: Carbon and water dynamics of semi-arid woodlands through drought and deluge

Australia’s semi-arid ecosystems can exert a disproportionate influence on interannual carbon cycling, yet their resilience to increasingly hot and prolonged drought remains poorly constrained. Here, we combine long-term eddy covariance measurements with stand inventory data from paired flux tower sites in Australia’s semi-arid zone to examine ecosystem responses to the Tinderbox drought that preceded the 2019/2020 Black Summer bushfires.The complete omission of two consecutive wet seasons led to substantial reductions in ecosystem productivity, accompanied by marked declines in understorey grass cover and increased overstorey tree mortality. Despite this widespread drought impact, productivity was reduced rather than halted, highlighting the capacity of woody semi-arid systems to persist under extreme water limitation. Following the drought, an unusual triple La Niña delivered multiple years of above-average rainfall. Despite experiencing the same climatic forcing, adjacent Acacia woodlands exhibited contrasting recovery trajectories: a stand characterised by lower tree density and higher drought-induced mortality recovered slowly, whereas a denser stand with lower mortality showed a rapid rebound in carbon uptake.Together, these results demonstrate that local differences in vegetation structure, mortality, and access to soil water strongly shape ecosystem recovery following extreme climate events, complicating efforts to predict the future resilience of semi-arid woody ecosystems under a warming climate.