Pervasive increase in tree mortality across the Australian continent

Area of Science:

• Ecology
• Climate Change Science
• Forestry

Background:

• Rising tree mortality rates due to climate change can diminish terrestrial ecosystem carbon storage.
• Quantifying global trends in tree mortality and their drivers is crucial for understanding carbon budget impacts.
• Australia's variable climate and diverse forests offer a unique test case for tree mortality dynamics.

Purpose of the Study:

• To investigate spatiotemporal patterns of tree mortality across Australian forest biomes over 83 years.
• To identify the drivers associated with observed trends in tree mortality.

Main Methods:

• Compiled an 83-year tree dynamics database (1941-2023) from over 2,700 forest plots in Australia.
• Analyzed tree mortality trends across tropical savanna, rainforest, and temperate forest biomes.
• Assessed the influence of stand structure, moisture index, competition index, species traits, growth, and temperature on mortality rates.

Main Results:

• A consistent trend of increasing tree mortality was observed across all four studied Australian forest biomes.
• The increasing mortality trend persisted after accounting for stand structure and was amplified by low moisture or high competition.
• Increasing temperature was associated with rising tree mortality, while growth rates showed no corresponding increase.

Conclusions:

• Ongoing climate change has induced pervasive shifts in forest dynamics, impacting even resilient forest biomes.
• These shifts threaten the long-term carbon sequestration capacity of forests under current and future climate scenarios.
• Understanding these dynamics is critical for predicting the future role of forests in the global carbon cycle.