When do plant hydraulics matter in terrestrial biosphere modelling?

Area of Science:

• Ecology
• Plant Physiology
• Ecosystem Modeling

Background:

• Plant hydraulics govern water transport from soil to leaves, crucial for ecosystem responses to environmental changes and stress recovery.
• Existing models of plant hydraulics vary, necessitating research into their significance for ecosystem functioning.

Purpose of the Study:

• To introduce and test four versions of plant hydraulics representations within the T&C terrestrial biosphere model.
• To investigate the impact of plant water capacitance and long-term xylem damage on ecosystem processes.

Main Methods:

• Developed four model versions combining representations with/without capacitance and xylem damage legacies.
• Applied these models across six case studies from semiarid to tropical ecosystems.
• Quantified the modulation of water and carbon dynamics by plant xylem flow, water storage, and xylem damage.

Main Results:

• Models with plant hydraulics predicted slower drought onset and more realistic diurnal water/carbon flux variability.
• Plant water storage significantly improved diurnal dynamics, especially when capacitance was included.
• Xylem damage legacies demonstrated a drought legacy effect, limiting post-drought productivity.

Conclusions:

• Plant hydraulics are vital for realistic water and carbon dynamics but do not solely enhance overall ecosystem model performance against climate variability.
• Future model development should integrate plant hydraulics with other processes like phenology and carbon allocation.