Using long-term field data to quantify water potential regulation in response to VPD and soil moisture in a conifer...

Area of Science:

• Plant physiology
• Ecology
• Environmental science

Background:

• Stomatal regulation of vascular water potential (Ψstem) is vital for plant gas exchange and drought survival.
• Characterizing species-specific Ψstem regulation under varying soil and atmospheric dryness is challenging.
• Existing models often overlook the combined influence of soil water potential (Ψsoil) and vapor pressure deficit (VPD).

Purpose of the Study:

• To test the hypothesis that Ψstem regulation is best defined by considering both Ψsoil and VPD.
• To develop a predictive model for species-specific Ψstem variation based on environmental factors.
• To establish a novel method for quantitatively comparing plant water use and climate sensitivity.

Main Methods:

• Collected high-resolution time-series data of Ψstem using optical dendrometers on Callitris rhomboidea.
• Monitored trees across multiple, highly variable growing seasons (571 days).
• Utilized diurnal Ψsoil and VPD data to predict Ψstem regulatory behavior.

Main Results:

• Ψstem regulatory behavior was accurately predicted using a combination of diurnal Ψsoil and VPD (R² = 0.74).
• The prediction model incorporated five mechanism-aligned parameters describing specific stomatal regulation.
• Demonstrated the effectiveness of continuous Ψstem monitoring for capturing dynamic plant responses.

Conclusions:

• Species-specific vascular water potential regulation is effectively characterized by integrating soil and atmospheric water status.
• A novel, data-driven approach enables quantitative comparison of water use and climate sensitivity across plant species.
• This method advances our ability to predict plant responses to environmental change and drought stress.