CO<sub>2</sub>, nitrogen deposition and a discontinuous climate response drive water use efficiency in global forests.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 34465788.
- Also identified by DOI 10.1038/s41467-021-25365-1 and PMC identifier 8408268.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Reduced stomatal conductance is a common plant response to rising atmospheric CO<sub>2</sub> and increases water use efficiency (W). At the leaf-scale, W depends on water and nitrogen availability in addition to atmospheric CO<sub>2</sub>. In hydroclimate models W is a key driver of rainfall, droughts, and streamflow extremes. We used global climate data to derive Aridity Indices (AI) for forests over the period 1965-2015 and synthesised those with data for nitrogen deposition and W derived from stable isotopes in tree rings. AI and atmospheric CO<sub>2</sub> account for most of the variance in W of trees across the globe, while cumulative nitrogen deposition has a significant effect only in regions without strong legacies of atmospheric pollution. The relation of aridity and W displays a clear discontinuity. W and AI are strongly related below a threshold value of AI ≈ 1 but are not related where AI > 1. Tree ring data emphasise that effective demarcation of water-limited from non-water-limited behaviour of stomata is critical to improving hydrological models that operate at regional to global scales.