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

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 data set 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 VCMAX (NSOL) when the soil relative extractable water content (REW) 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. This result was unexpected as it implies that NSOL (instead of stomatal closure) was the main process limiting GPP during drought.

GOURLEZ DE LA MOTTE Louis;  BEAUCLAIRE Quentin;  HEINESCH Bernard;  CUNTZ Matthias;  FOLTÝNOVÁ Lenka;  ŠIGUT Ladislav;  KOWALSKA Natalia;  MANCA Giovanni;  GODED BALLARIN Ignacio;  VINCKE Caroline;  ROLAND Marilyn;  IBROM A;  LOUSTEAU Denis;  SIEBICKE Lukas;  NEIRYINK Johan;  LONGDOZ Bernard; 

2020-09-25

ROYAL SOC

JRC119188

0962-8436 (online),   

https://publications.jrc.ec.europa.eu/repository/handle/JRC119188,   

10.1098/rstb.2019.0527 (online),