The Control Of Plant And Soil Hydraulics On The Interannual Variability Of Plant Carbon Uptake Over The Central Us

Presenter: Xueyan Zhang1
Co-Author(s): -
Advisor(s): Dr. Guoyue Niu and Dr. Xubin Zeng
1Department of Hydrology and Atmospheric Sciences, University of Arizona

Panapto Presentation Video
Oral Session 3: Aerosols, Isotopes, and Soils

The interannual variability (IAV) of gross primary productivity (GPP) reflects the sensitivity of GPP to climate variations and contributes substantially to the variations and long-term trend of the atmospheric CO2 growth rate. Analyses of three observation-based GPP products indicate that their IAVs are consistently correlated to terrestrial water storage anomaly over the Central US, where episodic droughts occur. A land surface model explicitly representing plant hydraulics and groundwater capillary rise with an adequate soil hydraulics well captures the observed GPP IAV. Our sensitivity experiments indicate that, without representations of plant hydraulics and groundwater capillary rise or using an alternative soil hydraulics, the land model substantially overestimates the GPP IAV and the GPP sensitivity to water in the Central US. This study strongly suggests the use of the van Genuchten hydraulic model to replace the most commonly-used Clapp-Hornberger model, which produces too strong soil suction of water especially in dry conditions, in land surface modeling. This study highlights the importance of realistic representations of plant and soil hydraulics and surface-groundwater interactions in Earth System Models for projections of future climates that may experience more intense and frequent droughts.

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