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Quantifying soil moisture impacts on light use efficiency across biomes
Author(s) -
Stocker Benjamin D.,
Zscheischler Jakob,
Keenan Trevor F.,
Prentice I. Colin,
Peñuelas Josep,
Seneviratne Sonia I.
Publication year - 2018
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/nph.15123
Subject(s) - environmental science , biome , arid , water content , vapour pressure deficit , eddy covariance , primary production , vegetation (pathology) , soil water , terrestrial ecosystem , moisture , productivity , canopy , ecosystem , water use efficiency , atmospheric sciences , hydrology (agriculture) , agronomy , soil science , ecology , transpiration , geography , meteorology , photosynthesis , macroeconomics , pathology , biology , medicine , botany , geotechnical engineering , economics , geology , irrigation , engineering
Summary Terrestrial primary productivity and carbon cycle impacts of droughts are commonly quantified using vapour pressure deficit ( VPD ) data and remotely sensed greenness, without accounting for soil moisture. However, soil moisture limitation is known to strongly affect plant physiology. Here, we investigate light use efficiency, the ratio of gross primary productivity ( GPP ) to absorbed light. We derive its fractional reduction due to soil moisture ( fLUE ), separated from VPD and greenness changes, using artificial neural networks trained on eddy covariance data, multiple soil moisture datasets and remotely sensed greenness. This reveals substantial impacts of soil moisture alone that reduce GPP by up to 40% at sites located in sub‐humid, semi‐arid or arid regions. For sites in relatively moist climates, we find, paradoxically, a muted fLUE response to drying soil, but reduced fLUE under wet conditions. fLUE identifies substantial drought impacts that are not captured when relying solely on VPD and greenness changes and, when seasonally recurring, are missed by traditional, anomaly‐based drought indices. Counter to common assumptions, fLUE reductions are largest in drought‐deciduous vegetation, including grasslands. Our results highlight the necessity to account for soil moisture limitation in terrestrial primary productivity data products, especially for drought‐related assessments.