Rain use efficiency gradients across Australian ecosystems.

Area of Science:

• Ecology
• Climate Science
• Carbon Cycle Research

Background:

• Rain use efficiency (RUE) is crucial for understanding how ecosystems convert precipitation into carbon assimilation.
• The spatial distribution and drivers of RUE across Australian ecosystems remain largely uncharacterized.
• This knowledge gap hinders accurate assessment of Australia's contribution to global carbon sequestration.

Purpose of the Study:

• To investigate the spatial distribution of RUE across diverse Australian terrestrial ecosystems.
• To identify the primary drivers influencing RUE variability.
• To project future changes in RUE under different climate change scenarios.

Main Methods:

• Analysis of RUE spatial distribution across Australia.
• Multiple linear regression modeling using climatic predictors to explain RUE variability.
• Scenario modeling (SSP5-8.5 and SSP1-2.6) to project future RUE changes.

Main Results:

• Continental mean RUE in Australia is 1.19 g C m⁻² mm⁻¹, with significant spatial variation.
• Climatic factors explain approximately 68% of RUE spatiotemporal variability.
• Drainage patterns influence RUE, with diverging landscapes showing reduced efficiency and converging landscapes showing increased efficiency.
• Projected RUE increases of 29.3–64.8% by century's end under SSP5-8.5 (high CO2), and a 7% decrease under SSP1-2.6 (low CO2).

Conclusions:

• This study establishes baseline RUE values for Australian ecosystems.
• Understanding RUE drivers is vital for predicting ecosystem responses to climate change and human impacts.
• Future RUE projections highlight the complex interplay between CO2 fertilization, warming, and precipitation patterns.