Convergence across biomes to a common rain-use efficiency.

Area of Science:

• Ecology
• Global Change Biology
• Ecosystem Science

Background:

• Water availability is a primary constraint on terrestrial ecosystem productivity.
• Ecosystems exhibit varying sensitivity of aboveground net primary production (ANPP) to precipitation variability.
• Rain-use efficiency (RUE) differs across biomes due to vegetation structure and biogeochemical factors.

Purpose of the Study:

• To investigate biome-specific differences in RUE and its relationship with precipitation.
• To determine if RUE converges under water-limiting conditions.
• To assess the implications of RUE convergence for predicting ecosystem responses to climate change.

Main Methods:

• Analysis of ANPP and precipitation data across diverse terrestrial biomes.
• Calculation of average RUE and its variation with mean annual precipitation.
• Experimental manipulation of water and resource limitations to identify maximum RUE (RUE(max)).

Main Results:

• RUE decreases as mean annual precipitation increases across biomes.
• A common maximum RUE (RUE(max)), characteristic of arid ecosystems, is observed during the driest years at all sites.
• Experimental data confirmed the convergence to RUE(max) under severe water limitation.

Conclusions:

• Terrestrial biomes converge to a similar maximum RUE when water is the most limiting resource.
• This RUE(max) phenomenon highlights a consistent ecosystem response to extreme drought.
• Future ecosystem models must incorporate this convergent feature to accurately predict responses to altered precipitation regimes and increased drought frequency.