Non-stomatal processes reduce gross primary productivity in temperate forest ecosystems during severe edaphic drought

Louis Gourlez de la Motte*, Quentin Beauclaire, Bernard Heinesch, Mathias Cuntz, Lenka Foltýnová, Ladislav Šigut, Natalia Kowalska, Giovanni Manca, Ignacio Goded Ballarin, Caroline Vincke, Marilyn Roland, Andreas Ibrom, Denis Lousteau, Lukas Siebicke, Johan Neiryink, Bernard Longdoz

*Corresponding author for this work

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Abstract

Severe drought events are known to cause important reductions of gross primary productivity (GPP) in forest ecosystems. However, it is still unclear whether this reduction originates from stomatal closure (Stomatal Origin Limitation) and/or non-stomatal limitations (Non-SOL). In this study, we investigated the impact of edaphic drought in 2018 on GPP and its origin (SOL, NSOL) using a dataset of 10 European forest ecosystem flux towers. In all stations where GPP reductions were observed during the drought, these were largely explained by declines in the maximum apparent canopy scale carboxylation rate VCMAX,APP (NSOL) when the soil relative extractable water content dropped below around 0.4. Concurrently, we found that the stomatal slope parameter (G1, related to SOL) of the Medlyn et al. unified optimization model linking vegetation conductance and GPP remained relatively constant. These results strengthen the increasing evidence that NSOL should be included in stomatal conductance/photosynthesis models to faithfully simulate both GPP and water fluxes in forest ecosystems during severe drought. This article is part of the theme issue 'Impacts of the 2018 severe drought and heatwave in Europe: from site to continental scale'.

Original languageEnglish
Article number20190527
JournalPhilosophical Transactions of the Royal Society B: Biological Sciences
Volume375
Issue number1810
Number of pages11
ISSN0962-8436
DOIs
Publication statusPublished - 2020

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