Large scale dieback events have profound effects on the biodiversity and ecosystem function with flow on effects to carbon, nutrient and hydrological cycles. Increasing temperatures associated with climate change are likely to cause droughts of greater duration and severity, exacerbating drought induced tree mortality across forest biomes. Recent evidence suggests that Australian vegetation is broadly resilient to drought stress. However, we are currently unable to predict the limits of this resilience in the face of rapid climate change. Making accurate predictions of vegetation response to climate change requires a detailed understanding of the physiological processes that allow plants to cope with drought stress and their thresholds to mortality. Recent work has demonstrated that the majority of woody plant species across all forest biomes operate close to their physiological safety margins with respect to drought, rendering them vulnerable to future shifts in precipitation and temperature. The central aim of this study was to determine the limits of drought stress tolerance in Australian tree species across forest biomes. Using the Terrestrial Ecosystem Research Network, we examined key physiological traits related to drought stress tolerance in tree species growing across a broad ecological range.
Results/Conclusions
The results of our work showed a strong relationship between site aridity and hydraulic traits of evergreen tree species growing across Australian forest and woodland biomes. This was reflected in tight coordination between stem hydraulic vulnerability and water stress experienced for different species across sites. These findings demonstrate the importance of hydraulic traits in adaptation to drought and the distributional limits of species with respect to aridity. Hydraulic safety margins were narrower among rainforest species compared with tree species located at more arid sites. This suggests rainforest species operate closer to their hydraulic threshold and may be more vulnerable to extreme climate events.