Using long-term field data to quantify water potential regulation in response to VPD and soil moisture in a conifer tree
Bourbia I, Yates LA and Brodribb TJ
New Phytologist
https://doi.org/10.1111/nph.70056
Abstract
- The regulation of vascular water potential (Ψstem) by stomata is one of the most dynamic and important behaviours in vascular plants, playing a central role in determining gas exchange and vulnerability to drought. Yet, the species-specific characterization of Ψstem regulatory behaviour in response to soil or atmospheric dryness remains elusive.
- We hypothesize that Ψstem regulatory behaviour can only be defined when the combination of both vapour pressure deficit (VPD) and soil water potential (Ψsoil) effects is considered. To test this hypothesis, we collected a high-resolution time series of Ψstem using optical dendrometers from trees of a hardy conifer, Callitris rhomboidea, monitored across multiple highly variable growing seasons.
- The regulatory behaviour of Ψstem collected over a total of 571 d could be predicted on the basis of diurnal Ψsoil and VPD (R2 = 0.74) using five mechanism-aligned parameters that describe specific stomatal regulation.
- Our novel approach to predict species-specific water potential variation in response to seasonal change using data from a continuous Ψstem monitoring technique creates a new opportunity to quantitatively compare water use and climatic sensitivity between diverse species or genotypes in the field or laboratory.
