Uncovering the critical soil moisture thresholds of plant water stress for European ecosystems
(2021) Global Change Biology — Vol. 28, n° 6, p. 2111-2123 (2021)
Files
GlobalChangeBiology-2021-Fu-UncoveringthecriticalsoilmoisturethresholdsofplantwaterstressforEuropean.pdf
Open Access - Adobe PDF
- 1.36 MB
Details
- Authors
Fu, Zheng 
Ciais, Philippe Bastos, Ana Wigneron, Jean‐Pierre
- Abstract
- Understanding the critical soil moisture (SM) threshold (θcrit) of plant water stress andland surface energy partitioning is a basis to evaluate drought impacts and improvemodels for predicting future ecosystem condition and climate. Quantifying the θcritacross biomes and climates is challenging because observations of surface energyfluxes and SM remain sparse. Here, we used the latest database of eddy covariance measurements to estimate θcrit across Europe by evaluating evaporative fraction(EF)-SM relationships and investigating the covariance between vapor pressure defi-cit (VPD) and gross primary production (GPP) during SM dry-down periods. We foundthat the θcrit and soil matric potential threshold in Europe are 16.5% and −0.7MPa, re-spectively. Surface energy partitioning characteristics varied among different vegeta-tion types; EF in savannas had the highest sensitivities to SM in water-limited stage,and the lowest in forests. The sign of the covariance between daily VPD and GPPconsistently changed from positive to negative during dry-down across all sites whenEF shifted from relatively high to low values. This sign of the covariance changed afterlonger period of SM decline in forests than in grasslands and savannas. Estimated θcritfrom the VPD–GPP covariance method match well with the EF–SM method, show-ing this covariance method can be used to detect the θ crit. We further found that soiltexture dominates the spatial variability of θcrit while shortwave radiation and VPDare the major drivers in determining the spatial pattern of EF sensitivities. Our resultshighlight for the first time that the sign change of the covariance between daily VPDand GPP can be used as an indicator of how ecosystems transition from energy to SMlimitation. We also characterized the corresponding θcrit and its drivers across diverseecosystems in Europe, an essential variable to improve the representation of waterstress in land surface models. K E Y W O R D Scritical soil moisture threshold, drought, Europe, evaporative fraction, gross primaryproduction, surface energy partitioning, vapor pressure deficit
- Affiliations
Citations
Fu, Z., Ciais, P., Makowski, D., Bastos, A., Stoy, P. C., Ibrom, A., Knohl, A., Migliavacca, M., Cuntz, M., Šigut, L., Peichl, M., Loustau, D., El‐Madany, T. S., Buchmann, N., Gharun, M., Janssens, I., Markwitz, C., Grünwald, T., Rebmann, C., et al. (2021). Uncovering the critical soil moisture thresholds of plant water stress for European ecosystems. Global Change Biology, 28(6), 2111-2123. https://doi.org/10.1111/gcb.16050 (Original work published 2021)